Núm. 1 - Caracterización - Sostenibilidad y Reciclaje

• Lightweight materials development for automotive engineering use. Manufacture and End of Life optimization through Life Cycle Assessment.

  H. Afonso González, J. Ibarretxe, E. Acha, U. Olaziregi Cuevas, A. Esnaola, A. Serras, A. Iturrondobeitia.

  Materiales Compuestos (2023). Vol. 08 - COMUNICACIONES MATCOMP21 (2022) Y MATCOMP23 (2023), (Núm. 1 - Caracterización - Sostenibilidad y Reciclaje), 19

  
  

  Abstract

  With fuel economy and lightweight design becoming ever more significant due to the current materials, resources and environmental crisis, the manufacture of polymer composites for automotive industry use has experienced a steady growth in the last years and is expected to keep growing in the coming years. This means that there is a vast range of different polymer composites available in the market, with their unique properties, manufacturing processes and materials imbedded in them, each with their own set of impacts on the environment throughout their whole life cycle. The end-of-life treatment of a composite determines a substantial fraction of its footprint on the planet, and advanced treatments, namely pyrolysis can be used to obtain high value added compounds such as hydrogen and other light fuels. This study aims to address and quantify the impacts associated with the manufacturing and end of life treatments of an experimental glass fibre mat reinforced thermoplastic composite and compare them with the impacts caused by materials currently used in the automotive industry. Life Cycle assessment methodology will be used to compare the environmental impacts of this new material with traditional glass fibre composites, natural fibre reinforced composites and other materials with similar mechanical properties.

  Abstract
  With fuel economy and lightweight design becoming ever more significant due to the current materials, resources and environmental crisis, the manufacture of polymer composites [...]

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• Interface damage characterization of carbon-epoxy composite materials

  D. Mocerino, M. Bruno, M. Monclús, D. Garoz, M. Rueda, J. Molina, . M.Flores, C. Gonzalez

  Materiales Compuestos (2023). Vol. 08 - COMUNICACIONES MATCOMP21 (2022) Y MATCOMP23 (2023), (Núm. 1 - Caracterización - Sostenibilidad y Reciclaje), 20

  
  

  Abstract

  This research shows a novel in-situ experimental approach to characterize a carbon-epoxy unidirectional composite system interface. Computational models were implemented to support the experimental campaign and identify the interface properties. After validating the computational model with experimental results, it was employed to study the behaviour of interface debonding under both mode I and mode II damage. By utilizing the validated model, it becomes possible to assess the consistency of the proposed experimental approach in characterizing the interface, with the aim of generating in future an analytical model able to predict interface characteristics. 

  Abstract
  This research shows a novel in-situ experimental approach to characterize a carbon-epoxy unidirectional composite system interface. Computational models were implemented to [...]

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• Sustainable synthesis of iron oxide nanoparticles embedded into carbon foams. Síntesis sostenible de espumas de carbono con nanopartículas de óxido de hierro intercaladas.

  C. Cuesta, R. García, E. Rodriguez, M. López-Antón, M. Martínez-Tarazona

  Materiales Compuestos (2023). Vol. 08 - COMUNICACIONES MATCOMP21 (2022) Y MATCOMP23 (2023), (Núm. 1 - Caracterización - Sostenibilidad y Reciclaje), 21

  
  

  Abstract

    RESUMEN: Las espumas de carbono son materiales macroporosos que convenientemente funcionalizados pueden ser muy útiles en aplicaciones de adsorción y catálisis. Por otra parte, los óxidos e hidróxidos de hierro tienen excelentes propiedades para ser utilizados en biomedicina, remediación ambiental o almacenamiento de energía, entre otras aplicaciones. Este trabajo tiene como objetivo la preparación de una espuma de carbono con especies de hierro nanodispersadas en su superficie SFFe(10:1), y la identificación de los cambios sufridos en la morfología y la estructura del carbono, con respecto la espuma preparada sin especies de hierro (SF). El método de síntesis utilizado se diseñó con la intención de que fuera sencillo, necesitara un mínimo de reactivos y partiera de un precursor de carbono sostenible. Para ello, se sintetizó la espuma de carbono a partir de sacarosa en ácido cítrico, utilizando Fe(NO3)3 · 9H2O como aditivo, mediante un procedimiento basado en tratamientos térmicos en atmósferas de aire e inerte. Se observó como la adición de un 10% de nitrato de hierro al precursor favorece la espumación produciéndose simultáneamente el crecimiento in situ de nanopartículas de óxido de hierro sobre la matriz de la espuma. Además, durante la carbonización, las especies de hierro formadas catalizan una incipiente grafitización del material de carbono. Con la concentración de nitrato empleada, el hierro queda mayoritariamente como magnetita nanodispersada en la superficie de la espuma de carbono.    ABSTRACT: Carbon foams are macroporous materials that, properly functionalized, can be very useful in adsorption and catalysis applications. On the other hand, iron oxides and hydroxides have excellent properties to be used in biomedicine, environmental remediation and energy storage, among other applications. The objective of this work was the preparation of a carbon foam with nanodispersed iron species on its surface SFFe(10:1) and the identification of the changes suffered in the morphology and structure of the carbon with respect to a foam prepared without iron species (SF). The synthesis method used was designed with the intention of being simple, requiring a minimum of reagents, and starting from a sustainable carbon precursor. To this end, the carbon foam was synthesized from sucrose in citric acid, using Fe(NO3)3 · 9H2O as additive. The procedure was based on heat treatments in air and inert atmospheres. It was observed how the addition of 10% iron nitrate to the precursor favours foaming, simultaneously producing in situ growth of iron oxide nanoparticles on the foam matrix. Furthermore, during carbonization, the created iron species catalyze an incipient graphitization of the carbon material. With the nitrate concentration evaluated, the iron remains mostly as nanodispersed magnetite on the surface of the carbon foam.

  Abstract
    RESUMEN: Las espumas de carbono son materiales macroporosos que convenientemente funcionalizados pueden ser muy útiles en aplicaciones de adsorción [...]

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• Study of the recycling and reprocessing of composite materials and their subsequent use in the manufacture of sustainable composite materials

  M. Campo, I. Lorero, A. Jiménez-Suárez, S. Prolongo.

  Materiales Compuestos (2023). Vol. 08 - COMUNICACIONES MATCOMP21 (2022) Y MATCOMP23 (2023), (Núm. 1 - Caracterización - Sostenibilidad y Reciclaje), 22

  
  

  Abstract

  Due to the great increase in the use of composite materials, there is a need to investigate and develop effective recovery, recycling, and reuse techniques. This technological challenge entails significant research efforts to solve the current problems to separate and reuse the components of composite materials. In this work, two alternatives have been studied to solve the environmental problems that the use of resins as a matrix of composite materials entails, since there is no sustainable recycling process after its useful life cycle. On the one hand, a thermomechanical reprocessing will be studied and on the other the viability of the chemical dissolution of the matrix. For both processes, the optimal conditions (temperature, time, solvent, and pressure) have been studied to allow reprocessing the material or dissolve the resin of the composite material to recover the fiber. Subsequently, for thermomechanical reprocessing, the technical feasibility of impregnating fibers during the reprocessing process in the hot plate press has been studied. And for chemical recycling, the feasibility that the recycled carbon fiber will be reused to make a new composite material.

  Abstract
  Due to the great increase in the use of composite materials, there is a need to investigate and develop effective recovery, recycling, and reuse techniques. This technological [...]

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• Piezoresistive sensors based on reinforced PVDF nanocomposites

  V. Díaz-Mena, X. Sánchez-Romate, D. Martinez-Diaz, M. Sanchez, A. Ureña

  Materiales Compuestos (2023). Vol. 08 - COMUNICACIONES MATCOMP21 (2022) Y MATCOMP23 (2023), (Núm. 1 - Caracterización - Sostenibilidad y Reciclaje), 23

  
  

  Abstract

  Currently, due to the great advances achieved in medicine, together with those related to materials science and engineering, in recent years there has been a growing interest in the use of flexible sensors for monitoring the human body. The present work shows the development of flexible piezoresistive sensors based on polyvinylidene fluoride (PVDF) reinforced with carbon nanotubes (CNTs). First, the analysis of the electrical properties shows an increase in the electrical conductivity with CNT content. This increase is less pronounced at higher CNT contents due to an electrical network saturation, where the main electrical transport mechanisms are dominated by the CNT aggregates. In this context, the electromechanical analysis shows a higher sensitivity, by means of Gauge Factor, at lower CNT contents due to a higher prevalence of tunneling transport mechanisms between neighboring nanoparticles, which is reflected in a more exponential electromechanical behavior. Finally, the analysis of the electromechanical properties at cycling loading shows an elevated repeatability of the electrical response between consecutive cycles, which is indicative of the high robustness of the manufactured sensors.

  Abstract
  Currently, due to the great advances achieved in medicine, together with those related to materials science and engineering, in recent years there has been a growing interest [...]

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• Properties of Tetra Pak Particle Reinforced Concrete for use in masonry parts.

  D. Gámez-García, A. Alcaraz-Codina, I. Lucio-Pérez, H. Saldaña-Márquez, E. Solís, D. Martínez

  Materiales Compuestos (2023). Vol. 08 - COMUNICACIONES MATCOMP21 (2022) Y MATCOMP23 (2023), (Núm. 1 - Caracterización - Sostenibilidad y Reciclaje), 24

  
  

  Abstract

  Advances in single-use packaging and container technology are generating an indiscriminate increase in urban solid waste, which is on the rise. In 2020, Mexico achieved a recycling rate of around 30% in Tetra Pak packages; although this percentage is encouraging, most waste still needs to be reincorporated into any cycle. On the other hand, one of the most alarming impacts of the construction industry is the extraction of raw materials and their potential greenhouse gas emissions. In order to associate these two environmental issues, this work aimed to evaluate the physical-mechanical properties of concrete added to Tetra Pak waste. Specimens of 10 cm in diameter and 20 cm in height were studied. For the mixtures, weight contents of 2%, 4%, 6%, and 8% of 5 mm x 3 cm fibers were used, which were tested in the fresh and hardened state at 14 and 28 days of curing. The results indicated that as the fiber content increases, the mechanical properties of the specimens decrease, so its use for structural purposes should be re-evaluated with other techniques, such as gamma irradiation. It is recommended to use this material in masonry pieces for non-structural purposes and to characterize its thermal and acoustic properties.

  Abstract
  Advances in single-use packaging and container technology are generating an indiscriminate increase in urban solid waste, which is on the rise. In 2020, Mexico achieved a [...]

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• Composite material thermal characterization for a digital twin-based model of an automated tape-laying process

  J. Rodrigues, J. Rodrigues

  Materiales Compuestos (2023). Vol. 08 - COMUNICACIONES MATCOMP21 (2022) Y MATCOMP23 (2023), (Núm. 1 - Caracterización - Sostenibilidad y Reciclaje), 25

  
  

  Abstract

  As the demand of the automotive and aeronautics industry for high-performance structures increases, the tendency goes towards the use of composite materials. This tendency requires designing efficient manufacturing processes to ensure repeatability and quality. Attending those requirements, the Automated Tape Laying process has gained relevance, as an out-of-autoclave process, consuming less energy and lower production times. This process consists of continuously heating a thermoplastic-based composite material and, using a compaction roll, pressing it against a mould, consolidating the structure by cooling down the composite. On the other hand, the Automated Tape Laying process arises a relevant problem related to the control system. The problem is related to the impossibility of measuring the temperature at the nip point, the temperature under the compaction roll, having no feedback then, no control decision. To overcome this type of problem, some authors have implemented a model-based control system, which allows to estimate the temperature at the desired location. To guarantee the best estimation, the model must be as detailed as possible, which leads to the concept of a Digital Twin. The Digital Twin as a detailed mathematical representation of the physical world, requires knowing the behaviour of the process element due to their interaction. This work proposes a thermal characterization methodology, using an in-house designed method, to describe the thermal-optical and thermal-conductivity properties of composite materials as a function of their temperature, which is required for the Digital Twin to compute the temperature distribution along an Automated Tape Laying process to lower the uncertainties due to properties approximations

  Abstract
  As the demand of the automotive and aeronautics industry for high-performance structures increases, the tendency goes towards the use of composite materials. This tendency [...]

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• Estudio de procesabilidad de composite CF-LMPAEK reciclado: inyección vs impresión 3D

  C. Martín-Pérez, D. Rosario, N. González-Castro, R. Travieso-Puente, E. Rodríguez-Senín

  Materiales Compuestos (2023). Vol. 08 - COMUNICACIONES MATCOMP21 (2022) Y MATCOMP23 (2023), (Núm. 1 - Caracterización - Sostenibilidad y Reciclaje), 26

  
  

  Abstract

  El proyecto ECO-CLIP se basa en una combinación de actividades de innovación orientadas a lograr piezas estructurales más ligeras a partir de los residuos de fábrica de TPC´s (Thermoplastic Composites), para la próxima generación de demostradores de fuselaje de aviación, que se lleva a cabo como parte de Clean Sky 2. En el proyecto se ha desarrollado un material polimérico compuesto de LMPAEK reforzado con un 40% en peso de fibra de carbono corta para la producción de Brackets. Con el fin de seleccionar la tecnología más ventajosa para la fabricación de estos, se ha llevado a cabo la comparativa de un método de fabricación convencional, como es la inyección, con una tecnología emergente, como es el FGF (Fused Granulated Fabrication). Para su comparativa se han llevado a cabo estudios de longitud y distribución de fibra, caracterización térmica y ensayos mecánicos, tanto para las probetas de inyección como en FGF. En esta última tecnología, además se ha llevado a cabo un estudio de parametrización de diámetros de boquillas con el fin de obtener la influencia que tiene en la adhesión entre capas, la longitud de la fibra, la microestructura de la pieza y la calidad final de las piezas. Gracias a estos resultados se ha podido establecer una relación entre la naturaleza del refuerzo, las propiedades térmicas y los parámetros de fabricación, con las propiedades mecánicas en pieza final.

  Abstract
  El proyecto ECO-CLIP se basa en una combinación de actividades de innovación orientadas a lograr piezas estructurales más ligeras a partir de los residuos [...]

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• Análisis de las propiedades mecánicas de composites de fibra continua con electrónica impresa embebida

  A. Pérez-Márquez*, J. Maudes, L. Bilbao, C. Vaquero, H. Villaverde, O. Adarraga, I. Bustero, I. Obieta, J. Gayoso

  Materiales Compuestos (2023). Vol. 08 - COMUNICACIONES MATCOMP21 (2022) Y MATCOMP23 (2023), (Núm. 1 - Caracterización - Sostenibilidad y Reciclaje), 27

  
  

  Abstract

  Desde hace varios años surge la necesidad de desarrollar materiales compuestos multifuncionales, que además de las propiedades clásicas como alta resistencia y elevada rigidez, integren distintas funcionalidades como por ejemplo la capacidad de detectar cualquier deformación de la estructura o la integración de iluminación, en una tendencia hacia el aligeramiento de las estructuras. Sin embargo, en la mayoría de los casos, el hecho de embeber componentes físicos puede hacer que surjan aspectos negativos en las estructuras como la presencia de discontinuidades en la resina que son propensas a la delaminación o la iniciación de grietas alrededor del componente, disminuyendo sus propiedades estructurales. Las técnicas de fabricación, basadas en la impresión funcional para el desarrollo de circuitos y electrónica impresa como parte inherente de la estructura, son muy prometedoras y por ello, están consiguiendo una gran aceptación en el mercado. Este trabajo muestra el análisis de las propiedades mecánicas de composites de fibra continua con electrónica impresa sobre diferentes tejidos empleados en los propios procesos de fabricación como fibras de vidrio o sobre velos poliméricos fabricados a partir de la técnica de electrospinning. Los resultados obtenidos muestran que no existen diferencias relevantes en el comportamiento a tracción por el hecho de tener circuitos impresos e incluso con diferentes espesores de línea. Así mismo, el módulo de elasticidad no se ve afectado para el caso de los composites que embeban circuitos de iluminación basados en LEDs integrados sobre el velo. También se han analizado las impresiones sobre los distintos sustratos mediante microscopía y se ha medido el comportamiento de un sensor resistivo de temperatura impreso en el velo y embebido en composite, para el cual se ha conseguido una respuesta lineal con una sensibilidad de 4,9Ω/ºC.

  Abstract
  Desde hace varios años surge la necesidad de desarrollar materiales compuestos multifuncionales, que además de las propiedades clásicas como alta resistencia [...]

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• Descomposición en modos en ensayos de fractura interlaminar y de uniones adhesivas con brazos de grieta asimétricos

  F. Mujika

  Materiales Compuestos (2023). Vol. 08 - COMUNICACIONES MATCOMP21 (2022) Y MATCOMP23 (2023), (Núm. 1 - Caracterización - Sostenibilidad y Reciclaje), 28

  
  

  Abstract

  Las pruebas de flexión con entalla final y viga en doble voladizo se diseñaron para caracterizar la fractura interlaminar de materiales compuestos en modos puros I y II. En ambos casos, los especímenes tienen una longitud de fisura inicial en la mitad del espesor. En el caso de especímenes bimaterial, si la grieta está ubicada en el medio del espesor, el modo mixto podría existir, debido a la asimetría material. El objetivo del presente estudio es proponer relaciones geométricas para obtener condiciones de modo puro cuando se ensayan especímenes bimateriales en configuraciones DCB y ENF.

  Abstract
  Las pruebas de flexión con entalla final y viga en doble voladizo se diseñaron para caracterizar la fractura interlaminar de materiales compuestos en modos puros [...]

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• Pruebas de fuego virtuales de paneles compuestos termoplásticos

  F. MILLAN, M. FROVEL, F. CABRERIZO, M. TORRE, . F.LOPEZ, D. BENITO, R. TEJERINA, . S.LOPEZ(‡).

  Materiales Compuestos (2023). Vol. 08 - COMUNICACIONES MATCOMP21 (2022) Y MATCOMP23 (2023), (Núm. 1 - Caracterización - Sostenibilidad y Reciclaje), 30

  
  

  Abstract

  Este artículo describe el desarrollo de una metodología de simulación FEM para predecir el comportamiento de un panel compuesto con matriz termoplástica y fibras de carbono en pruebas de fuego. El panel tiene un soporte de metal en su centro a cuál se aplica simultáneamente una carga monotónica mecánica al inicio del ensayo de fuego. La herramienta tiene como objetivo capturar los fenómenos más relevantes involucrados en este complejo problema y centrarse en predecir el tiempo de desprendimiento del soporte bajo la carga aplicada, que es el resultado más relevante de dicha prueba de fuego. En el problema, muchos diferentes fenómenos físicos están involucrados. Para considerar los más relevantes, se ha seleccionado un FEM termomecánico acoplado y, dentro de él, un análisis de fluencia transitoria. Las partes más relevantes de la simulación son los supuestos del modelo térmico, el modelo constitutivo mecánico del material, la dependencia de la temperatura de las propiedades térmicas y mecánicas y la selección de un criterio de fallo consistente. Durante el desarrollo de la metodología de simulación se han tomado precauciones para identificar un conjunto de parámetros que conforman los ajustes disponibles. Seleccionando un conjunto de valores para estos parámetros, se puede simular un caso de prueba concreto. Manteniendo los valores de estos parámetros sin cambios, la metodología puede predecir casos similares en lugar de probar estos casos físicamente en ensayos de fuego. Este artículo se centra en el desarrollo de herramientas de simulación. Por el momento solo se han realizado tareas iniciales de correlación y validación. Se espera completar y mejorar esta investigación en el futuro aumentando la validez de la simulación, p.ej. incluyendo cargas de tracción y/o ángulos/distancias de llama. En el documento también se proporciona una idea de las posibles simplificaciones y mejoras de las herramientas.

  Abstract
  Este artículo describe el desarrollo de una metodología de simulación FEM para predecir el comportamiento de un panel compuesto con matriz termoplástica [...]

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• Contribution of auxetic core structures on the radial impact behaviour of 3D printed continuous fibre reinforced polyamid profiles

  U. Morales*, A. Esnaola, I. Sukia, L. Aretxabaleta, J. Aurrekoetxea

  Materiales Compuestos (2023). Vol. 08 - COMUNICACIONES MATCOMP21 (2022) Y MATCOMP23 (2023), (Núm. 1 - Caracterización - Sostenibilidad y Reciclaje), 31

  
  

  Abstract

  The present study investigates the enhanced energy absorption capabilities in the radial direction of structures through the combination of continuous glass fiber reinforced polyamide hollow sections (cGF/PA) and complex cellular cores manufactured by 3D printing cFF (continuous Fibre Fabrication). For this purpose, two types of auxetic structures based on conventional reentrant structure designs (hexagonal and octagonal) have been characterised. Likewise, the energy absorption capacity (SEA) of the filled profiles has been analysed and compared with the capability of the hollow profiles. Falling weight impact tests have been carried out for the dynamic characterization of the profiles and the effect of concentric fibers and the auxetic core on filled profiles has been analysed. On the one hand, it has been identified that the octagonal re-entrant structure (RSH) presents a higher impact performance, reaching a SEA value of 8.5 kJ/kg. On the other hand, it has been found a substantial improvement in the absorption capability of the filled profiles (17.7 kJ/kg) compared to the capability of the hollow profiles (2.5 kJ/kg). The SEA values achieved are promising, as they are 18% higher than the values found in literature.

  Abstract
  The present study investigates the enhanced energy absorption capabilities in the radial direction of structures through the combination of continuous glass fiber reinforced [...]

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• Procedimiento de extrapolación de leyes cohesivas de uniones adhesivas en modo I y II: validación numérica

  A. Arrese, U. Garitaonaindia, I. Adarraga, F. Mujika

  Materiales Compuestos (2023). Vol. 08 - COMUNICACIONES MATCOMP21 (2022) Y MATCOMP23 (2023), (Núm. 1 - Caracterización - Sostenibilidad y Reciclaje), 32

  
  

  Abstract

  En este trabajo se presenta y valida numéricamente un novedoso procedimiento de extrapolación para predecir las leyes cohesivas de uniones adhesivas en modo I y II. En primer lugar, partiendo de los métodos de reducción de datos basados en la variación de la flexibilidad recientemente propuestos para extraer las leyes cohesivas, se definen nuevas expresiones factorizadas con respecto a la carga aplicada y a los espesores de adhesivo y adherente de la flexibilidad (C0i), la Integral–J (J0i) y el desplazamiento de la punta de la grieta (Δ0i) para cada modo de fractura. Suponiendo que todos los efectos asociados al daño se incluyen en la longitud de grieta equivalente, y de acuerdo con las expresiones polinómicas de J0i, C0i y Δ0i con respecto a la misma, se obtienen relaciones invariantes entre J0i-C0i y Δ0i-C0i para cualquier relación de espesores adhesivo-adherente de un sistema material y configuración de ensayo determinados, tanto en modo I como en modo II. Por último, se presenta un procedimiento de extrapolación basado en las curvas calibradas J0i-C0i y Δ0i-C0i, que permite estimar las leyes cohesivas para un amplio rango de relación de espesores adhesivo-adherente de un sistema material dado procesando únicamente la curva carga-desplazamiento del ensayo.

  Abstract
  En este trabajo se presenta y valida numéricamente un novedoso procedimiento de extrapolación para predecir las leyes cohesivas de uniones adhesivas en modo [...]

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• Paneles fabricados mediante curado UV de prepregs fuera de autoclave reforzados con perfiles de pultrusión UV

  I. Eguino, G. Goenaga, A. Arruti, I. Saenz-Dominguez, I. Tena, F. Vallejo, M. Sarrionandia, J. Aurrekoetxea

  Materiales Compuestos (2023). Vol. 08 - COMUNICACIONES MATCOMP21 (2022) Y MATCOMP23 (2023), (Núm. 1 - Caracterización - Sostenibilidad y Reciclaje), 29

  
  

  Abstract

  En el presente trabajo se ha demostrado el potencial de la tecnología de curado UV cuando se aplica en los materiales compuestos reforzados con fibra de vidrio. Se han comparado dos vías de fabricación de paneles; la fabricación por separado de ambos elementos y su posterior adhesivado, y la integración directa de los perfiles en el curado UV de las pieles. Los resultados de ensayos interlaminares demuestran que la resistencia de la unión prepreg/perfil es equiparable a la de la unión prepreg/prepreg. Consecuentemente, los prototipos obtenidos con ambas estrategias muestran prestaciones mecánicas similares, tanto en rigidez como en resistencia a la flexión. Por último, la baja temperatura con la que se da el curado UV de la piel permite utilizar núcleos hidrosolubles fabricados mediante impresión 3D que facilitan las operaciones de laminado y la compactación.

  Abstract
  En el presente trabajo se ha demostrado el potencial de la tecnología de curado UV cuando se aplica en los materiales compuestos reforzados con fibra de vidrio. Se [...]

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Núm. 2 - Fabricación y Aplicaciones Industriales - Sostenibilidad y Reciclaje.

• Determination of curing times in an ultraviolet curing composites manufacturing process

  J. Vallejo, I. Avila, A. Uriarte

  Materiales Compuestos (2023). Vol. 08 - COMUNICACIONES MATCOMP21 (2022) Y MATCOMP23 (2023), (Núm. 2 - Fabricación y Aplicaciones Industriales - Sostenibilidad y Reciclaje.), 33

  
  

  Abstract

  Currently, the manufacture of fiberglass composite parts for the automotive industry is limited by the curing times of the resins. The curing of this type of parts is usually done at room temperature, which entails waiting times of up to 48 hours. The purpose of this study is to analyse the curing times of the pieces made with ultraviolet curing resin to replace the conventional temperature curing. In the case of ultraviolet radiation curing, the geometry of the part has a significant importance in curing times. To carry out this study, the UV lamp has been characterized to determine the irradiance at different distances. Once the irradiance is obtained as a function of the distance, the curing time of the prepreg test tubes was determined by means of a dielectric analysis (DEA). As a result, a mathematical model capable of approximating the curing time of different types of pieces based on their geometry and distance from the spotlight has been obtained. In this way, it is possible to create a strategy that optimizes the process. This process is much more efficient than the hand lay-up (HLU) used up to now, so it could be a good substitute if you want to increase the production of fiberglass composite parts.

  Abstract
  Currently, the manufacture of fiberglass composite parts for the automotive industry is limited by the curing times of the resins. The curing of this type of parts is usually [...]

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• Establishing the differences between the use of bio-based composites and nanocomposites as matrices in additive manufacturing.

  K. Nuñez-Carrero, M. Villar, L. Pastor, F. Lizalde-Arroyo, J. Pastor

  Materiales Compuestos (2023). Vol. 08 - COMUNICACIONES MATCOMP21 (2022) Y MATCOMP23 (2023), (Núm. 2 - Fabricación y Aplicaciones Industriales - Sostenibilidad y Reciclaje.), 34

  
  

  Abstract

  With the recent increase in the use of additive manufacturing (AM) in more and more challenging applications, the demands on the mechanical performance and sustainability of printed parts are increasing considerably. Among the different additive manufacturing technologies, fused filament fabrication (FFF) is the most widely used for thermoplastic materials. This work focuses on comparing the behaviour of parts obtained by FFF using a bio-based polyamide (BIOPA-11) reinforced with different types of fibres: short glass fibre (GF) and a fibrillar nanoclay (SEP, sepiolite). Different composites were prepared by melt process, converted into filaments used in FFF, and characterised the final parts. The thermal and mechanical properties obtained were systematically examined as a function of printing orientation, amount and type of fibre, accompanied by X-ray tomography image analysis of the internal parts of the pieces. As expected, anisotropic properties showed improvements in Young's Modulus and tensile strength in both composites with increasing amount of reinforcement, with respect to pure biopolyamide. However, the improvements in mechanical performance of the nanocomposites were very noticeable under many conditions (composition and direction of fabrication). The research shows that this is due to the stiffening mechanism, based on the polymorphism of BIOPA, which is induced by nanometric loadings. Additionally, the internal morphology of the nanocomposite parts showed small amounts of inter-filament cavitations, while the parts obtained from the GF composites showed irregular, intra-filament cavitations. Thus, the BIOPA11 nanomaterial parts are attractive in terms of properties, weight, cost reduction, and sustainability.

  Abstract
  With the recent increase in the use of additive manufacturing (AM) in more and more challenging applications, the demands on the mechanical performance and sustainability [...]

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• Materials from revaluation of rice straw through extraction of cellulose and lignin

  V. Serrano, M. Carbonell, H. Pérez, V. Serrano Martínez

  Materiales Compuestos (2023). Vol. 08 - COMUNICACIONES MATCOMP21 (2022) Y MATCOMP23 (2023), (Núm. 2 - Fabricación y Aplicaciones Industriales - Sostenibilidad y Reciclaje.), 35

  
  

  Abstract

  Rice straw is a problematic agricultural waste that is currently burnt in tonnes in the Albufera de Valencia after the harvest, with the consequent environmental damage. In this sense, to avoid wasting resources and unnecessary pollution, it is proposed to revalue the product, that is, to use rice straw, as a source of lignin and cellulose, for the development of materials for footwear, such as soles, insoles, or adhesives. The extraction of cellulose fibres from rice straw is done by physical and/or chemical processes, such as: hydrothermal steam treatment (steam explosion); alkaline treatment, peroxides, and bleaching. The extraction method is optimised by combining processes to maximise the yield obtained. To do this, the processing conditions of each of the extraction stages are varied, optimising variables such as: temperature, time, CO2 pressure, among others. Furthermore, through the use of lignin, also present in rice straw, it is possible to produce polyols to synthesise adhesives, achieving a complete revaluation of rice straw. Therefore, this study aims to determine the effect of rice straw processing conditions on the cellulose extraction yield by optimising the hydrothermal process, pre- and post-processing, as well as on the properties of the cellulose fibres, in addition to the extraction of lignin for its future use as a raw material for the production of polyols and synthesis of adhesives.

  Abstract
  Rice straw is a problematic agricultural waste that is currently burnt in tonnes in the Albufera de Valencia after the harvest, with the consequent environmental damage. In [...]

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• Diseño de moldes de materiales compuestos para la fabricación aditiva basada en extrusión

  E. Bellvert*, J. Antolín-Urbaneja, H. Vallejo, J. Gayoso, . J.I.Hernández, A. Pizarro

  Materiales Compuestos (2023). Vol. 08 - COMUNICACIONES MATCOMP21 (2022) Y MATCOMP23 (2023), (Núm. 2 - Fabricación y Aplicaciones Industriales - Sostenibilidad y Reciclaje.), 36

  
  

  Abstract

  La fabricación aditiva mediante extrusión de materiales termoplásticos en formato pellet se está convirtiendo en una tecnología prometedora que trata de competir con tecnologías de fabricación convencionales. En este sentido, permite depositar una alta cantidad de material (kg/h), pudiendo generar preformas de moldes termoplásticos en un tiempo razonable que permita rivalizar con los precios del mecanizado de moldes metálicos de gran tamaño. Sin embargo, aún es necesario analizar sus limitaciones productivas, abordando soluciones desde el punto de vista de la selección de los materiales, el propio diseño del molde y los postprocesos necesarios para la obtención de moldes operativos para la fabricación de piezas con materiales compuestos. En concreto, dentro del Proyecto MOLDAM cofinanciado por el EIT Manufacturing, se ha seleccionado un material termoplástico reforzado con fibra de carbono (PA6/CF) en formato granza para la fabricación aditiva basada en extrusión de alta tasa de deposición. Se ha realizado una amplia campaña de ensayos del material extruido, para caracterizar sus propiedades termo-mecánicas en las direcciones de deposición y a diferentes temperaturas, basada en los requisitos de los casos de uso (sector aeronáutico y eólico). El objetivo ha sido desarrollar una metodología de diseño iterativo de moldes, en la que se utilizan herramientas avanzadas de Ingeniería asistida por ordenador (CAE), para simular y calcular el comportamiento termo-mecánico de los moldes mediante el análisis de elementos finitos (FEA), definiendo así los espesores y rellenos óptimos para garantizar la integridad estructural del molde en las condiciones de curado de las piezas en autoclave (P=7bar,Tª=180ºC).  

  Abstract
  La fabricación aditiva mediante extrusión de materiales termoplásticos en formato pellet se está convirtiendo en una tecnología prometedora [...]

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• Effect of the Surface treatments on the interphase during the injection moulding process with PAEK with carbon fibre

  J. Vidal, P. Castell, A. Marqués, J. Dieste

  Materiales Compuestos (2023). Vol. 08 - COMUNICACIONES MATCOMP21 (2022) Y MATCOMP23 (2023), (Núm. 2 - Fabricación y Aplicaciones Industriales - Sostenibilidad y Reciclaje.), 37

  
  

  Abstract

  The transformation processes used for thermoplastic composites, have been increasing their complexity, while incorporating new high demanding materials. From the aeronautic and medical sector, with their restrictions and specific demanding needs. The PAEK materials have been promoted and deeply applied due to their high temperature stability and their chemical resistance. In this research, the work has focussed on the use of the reinforced 40%CF PEEK process through injection moulding. In these over injection moulding processes the joint between 40%CF PEEK and other materials such as Aluminium, or reinforced PA and PEEK has been studied. As well as the adhesion between them and the variation generated on the mechanical properties. It has been observed that this joint is far better between thermoplastic materials than between metals and thermoplastic, this is due to the fact that even tough the PEEK has high processing temperatures, these are not relevant chemically speaking for metals such as Aluminium. Limiting the forces of the interphase to the physical and mechanical interaction between both materials. Nevertheless, in the case of the thermoplastic over injected parts several parameters have been observed to be affecting the final properties of the joint. Firstly, the over injected angle, obtaining higher mechanical properties as the angle increases as well as the contact surface. And the effect of the roughness of the overinjected part, having these a direct impact on the final mechanical properties.

  Abstract
  The transformation processes used for thermoplastic composites, have been increasing their complexity, while incorporating new high demanding materials. From the aeronautic [...]

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• Implementation guidelines for the application of innovative composite manufacturing processes in the shipbuilding industry

  I. Saenz-Dominguez, R. Pereira, I. Ruiz de Eguino, A. Arruti, I. Tena

  Materiales Compuestos (2023). Vol. 08 - COMUNICACIONES MATCOMP21 (2022) Y MATCOMP23 (2023), (Núm. 2 - Fabricación y Aplicaciones Industriales - Sostenibilidad y Reciclaje.), 38

  
  

  Abstract

  Composites are still playing an important role in the strategic agendas of industries associated with the transport sector, such as the shipbuilding industry. This is mainly because composites are a key element in lightening structures due to their elevated strength-to-weight characteristics, excellent corrosion resistance and low maintenance costs. However, the production capacity in the number of Fibre Reinforced Polymer (FRP) ships nowadays is not achieving its full potential due to high total production costs. Thus, to maintain or even expand the competitive position of the EU shipbuilding industry it is essential to improve, optimize and automate the production processes for FRP parts. The European Project Fibre4Yards (This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 101006860) addresses this challenge through the implementation of the Shipyard 4.0 concept and applying innovative FRP manufacturing technologies to the shipbuilding industry such as: curved pultruded profiles, automated fibre placement (ATP), adaptive moulds, additive manufacturing, and hot stamping. This work proves that during the adaptation process of certain manufacturing technologies to a new market, the decision-making stage must follow some specific steps: from the first analysis of the technical feasibility and the perception of the market of each technology, to the final measurements of the achieved improvements. Therefore, in this paper, implementation guidelines on adapting new composite manufacturing processes to the shipbuilding industry are presented, based on their evolution from the initial state to the final improvements.

  Abstract
  Composites are still playing an important role in the strategic agendas of industries associated with the transport sector, such as the shipbuilding industry. This is mainly [...]

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• Re-usage of uncured carbon fiber scrap material

  J. Sistach*, A. Calero, B. López-Romano, M. Ordóñez

  Materiales Compuestos (2023). Vol. 08 - COMUNICACIONES MATCOMP21 (2022) Y MATCOMP23 (2023), (Núm. 2 - Fabricación y Aplicaciones Industriales - Sostenibilidad y Reciclaje.), 39

  
  

  Abstract

  Industrial automated tape layup methods significantly increase the productivity, precision, and efficiency of manufacturing methods for large aerospace parts; however, although they allow reducing scrap fraction compared with manual processes, it keeps being too high, requiring waste management. The scope of the MC4 project, part of Horizon Europe program, is to not only recycle that scrap material, but also to transform it to a completely new, functional part, without the need of adding additional material other than this recycled scrap. This can be achieved by cutting that material into strip shape and reducing it to a specific thickness by means of a compacting process. Those homogenous thickness strips can then be processed using a heated plate press to form it to any needed shape. Mechanical properties will be studied and compared to the original material, to check if this process is suitable for the manufacturing of functional parts. As this method does not separate the original resin and fiber, it avoids the usage of chemicals that can damage the properties of the material and increase the risk and pollution of the process, which is ideal for a recycling process.

  Abstract
  Industrial automated tape layup methods significantly increase the productivity, precision, and efficiency of manufacturing methods for large aerospace parts; however, although [...]

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• Revaluation of recycled reinforcement fibers through innovative textile technologies for developing new thermoplastic composites

  I. Doménech, J. Pascual, F. Fornés, C. Santamaría

  Materiales Compuestos (2023). Vol. 08 - COMUNICACIONES MATCOMP21 (2022) Y MATCOMP23 (2023), (Núm. 2 - Fabricación y Aplicaciones Industriales - Sostenibilidad y Reciclaje.), 40

  
  

  Abstract

  Composite materials, such as those made from carbon and glass fibres, are now considered to be high value-added materials. However, a barrier to their full circularity is the difficulty of their recyclability and the serious environmental problems that these materials pose. Fibres can be recovered using techniques such as pyrolysis and solvolysis and disposed of as chopped fibre at the end of their life cycle. However, their use in industrial applications is limited to injection moulding, anisotropic mats, etc. This work has focused on the research and adaptation of textile technologies for staple fibre processing, such as carding, spinning and weaving, with the aim of obtaining textile intermediates suitable for the production of thermoplastic composites. These technologies must improve the mechanical properties of currently available commercial solutions and adapt to these reinforcing fibres, which are fragile, extremely thin and in some cases electrically conductive. This research has resulted in the production of intermediate textile products such as hybrid yarns (rCF-PA6 and rAramid-PA6), and nonwovens (rCF-PA6, rAramid-PA6 y rGF-PA6), both suitable for obtaining mainly thermoplastic composites.

  Abstract
  Composite materials, such as those made from carbon and glass fibres, are now considered to be high value-added materials. However, a barrier to their full circularity is [...]

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• Modification of the performance of printed parts through their hybridization with thermostable resin

  J. Gómez, S. Neira, A. Allue, K. Gondra, D. Pineda

  Materiales Compuestos (2023). Vol. 08 - COMUNICACIONES MATCOMP21 (2022) Y MATCOMP23 (2023), (Núm. 2 - Fabricación y Aplicaciones Industriales - Sostenibilidad y Reciclaje.), 41

  
  

  Abstract

  The final benefits obtained in plastic parts made with the commonly used 3D printing technologies (extrusion, laser sintering, photopolymerizable resin bath, inkjet) depend on the nature of the materials used, and the variables and printing strategies followed for obtaining the parts. In the present study, working with filament extrusion technology, the development of hybrid polymeric structures has been analysed with the purpose of being used as moulds for plastic and composite moulding processes. 3D printing by thermoplastic extrusion enables the use of a wide catalogue of materials, and facilitates the hybridization of the printed parts, choosing different values for variables such as skin thickness, wall thickness, or the pattern and infill percentage. Acting on the values of these variables, it is possible to generate superficial and internal porosity, or obtain cast parts with solid walls that define the geometric details and the surface finish of the final part. The hybridization study was carried out with PC ABS as a thermoplastic printing matrix and catalysed thermosetting resin as a complementary material. The characteristics of the thermosetting resin used in hybridization can be modulated by formulating its composition, to achieve additional features or functionalities in the printed parts, such as greater thermal or mechanical resistance, to modify their conductivity or thermal or electric insulation characteristics.

  Abstract
  The final benefits obtained in plastic parts made with the commonly used 3D printing technologies (extrusion, laser sintering, photopolymerizable resin bath, inkjet) depend [...]

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• Integrated nano-enabled heaters for automotive composite panels to enable external airbag activation

  R. Seddon, M. Chapartegui, I. Gaztelumendi, A. Iriarte Legarreta, S. Florez, N. Romero, R. Fernandez

  Materiales Compuestos (2023). Vol. 08 - COMUNICACIONES MATCOMP21 (2022) Y MATCOMP23 (2023), (Núm. 2 - Fabricación y Aplicaciones Industriales - Sostenibilidad y Reciclaje.), 42

  
  

  Abstract

  OASIS Composites Open Innovation Test Bed (OITB) is a single-entry point for scale-up of Innovative Smart lightweight polymer matrix and aluminium composite materials and components. OASIS offers technological and business support services for accelerated innovation studies and success in industrialisation, market penetration and commercialisation of nano-enabled products (NEPs). IGESTEK (Spain) is a leading company in the development of technology projects: specialized in lightweight solutions using plastics and composite materials. In collaboration with Tecnalia (Spain), IPC (France), University of Patras (Greece), UCLM (Spain), TMBK (Poland) and AMIRES (Czech Republic) they identified an opportunity for the development of a heating system based on buckypapers (MWCNT films) for automotive exterior bodywork panels manufactured using recyclable thermoplastic composite material via a press moulding method. Heater integration was screened using resistive heating, simple mechanical and microscopy analysis of the test panels. Coupon panels were manufactured (using optimised processing conditions) for thermal analysis. A prototype mould was designed and manufactured for the fabrication of representative demonstrator parts (1:3 scale car bonnet panel). Electrothermal analyses of four heater configurations were calculated, leading to the selection of two final demonstrator configurations. Ten functioning demonstrator panels were successfully manufactured based on these two designs. Thermal assessment of the integrity of the heaters was carried out via electrical resistive heating. The results of the collaboration confirmed that NEP based thin film heaters could successfully be integrated into thermoplastic composite panels via a compression thermoforming process.

  Abstract
  OASIS Composites Open Innovation Test Bed (OITB) is a single-entry point for scale-up of Innovative Smart lightweight polymer matrix and aluminium composite materials and [...]

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• Infinite: composites aeroespaciales sensorizados digitalmente desde su fabricación hasta el final de vida

  Materiales Compuestos (2023). Vol. 08 - COMUNICACIONES MATCOMP21 (2022) Y MATCOMP23 (2023), (Núm. 2 - Fabricación y Aplicaciones Industriales - Sostenibilidad y Reciclaje.), 43

  
  

  Abstract

  Uno de los mayores desafíos a los que se enfrenta la industria aeronáutica europea es la necesidad de ofrecer tecnologías digitales transformadoras para completar el ciclo de vida de las aeronaves y aumentar la competitividad. Esto ha llevado recientemente, por ejemplo, al desarrollo de nuevas superficies aerodinámicas, SHM y la incorporación de materiales multifuncionales tanto dentro de estructuras primarias como secundarias, entre otros. Sin embargo, es necesario incorporar las ventajas de los sistemas de control inteligentes que se pueden utilizar para la monitoración in situ de la fabricación de alto valor, el mantenimiento, reparación y revisión (MRO) en servicio y el reciclaje al final de la vida útil (EoL).El proyecto europeo INFINITE tiene como objetivo desarrollar sensores y analizadores basados en el uso de microhilos ferromagnéticos para ser embebidos en piezas estructurales compuestas, con el fin de monitorizar la fabricación y la salud estructural a lo largo de todo el ciclo de vida del componente. El sistema de monitoreo inalámbrico permitirá producir señales digitales y gran conjunto de datos vinculados con el espécimen para crear un gemelo digital de la estructura construida que también representará toda la historia desde que se fabricó a través de todas las operaciones de mantenimiento realizadas. Esto proporcionará los medios para desarrollar una garantía de calidad precisa, rentable y personalizada de los componentes compuestos aeroespaciales a lo largo de toda su vida útil, asegurando que las estructuras aeroespaciales estén bien posicionadas para cumplir con las estrategias económicas circulares actuales, pero altamente exigentes.

  Abstract
  Uno de los mayores desafíos a los que se enfrenta la industria aeronáutica europea es la necesidad de ofrecer tecnologías digitales transformadoras para [...]

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• Design and manufacture of 3D printed cores for the integration of photovoltaic cells in sandwich panels

  I. Sukia, A. Esnaola, J. Aizpurua, W. Cambarau, J. Hernández, J. Aurrekoetxea

  Materiales Compuestos (2023). Vol. 08 - COMUNICACIONES MATCOMP21 (2022) Y MATCOMP23 (2023), (Núm. 2 - Fabricación y Aplicaciones Industriales - Sostenibilidad y Reciclaje.), 44

  
  

  Abstract

  Multifunctional sandwich panels that can lighten and generate electrical energy are strategic for many industrial sectors, such as electric vehicle roofs or drones. This work analyses the integration of crystalline silicon photovoltaic cells between the glass/epoxy skins and the core manufactured by 3D printing with a polyamide reinforced with short carbon fibres. 3D printing has enabled the development of lightweight and stiff cores, with integrated wiring and junction box housings within the sandwich structure, as well as facilitators for the skin infusion process. The core design, with ramps on the periphery, facilitates the lamination and impregnation flow in the infusion process and the re-coating operations after infusion. The results, comparing the performance of the sandwich panel with and without integrated photovoltaic cells, show that the effect on the mechanical properties of the sandwich panel is not very significant. The maximum force recorded under a complex bending-twisting load is 11% lower with cells, but no delamination phenomena were observed in any case. As for the penetration energies under quasi-static and impact loads, the energies recorded for structures with photovoltaic cells are 5% and 2% lower respectively.

  Abstract
  Multifunctional sandwich panels that can lighten and generate electrical energy are strategic for many industrial sectors, such as electric vehicle roofs or drones. This work [...]

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• Mechanical recycling of composites for profile production by pultrusion

  S. Quiles-Díaz*, A. Gálvez Moreno, E. Barriguete, M. Hernández, A. Menaza, A. Farre.

  Materiales Compuestos (2023). Vol. 08 - COMUNICACIONES MATCOMP21 (2022) Y MATCOMP23 (2023), (Núm. 2 - Fabricación y Aplicaciones Industriales - Sostenibilidad y Reciclaje.), 45

  
  

  Abstract

  The investigation into recycling methodologies for composite materials has emerged as a prominent area of study, encompassing both theoretical research and practical implementation. Within this context, the present study focuses on the mechanical recycling of obsolete epoxy resin pieces reinforced with fiberglass, which are subsequently repurposed as fillers in the production of new profiles through pultrusion technology. A comprehensive examination of the grinding process, granulometric distribution, and rheological properties of the final system was conducted, with the objective of maximizing the filler content within the resin while optimizing the properties of the manufactured profile. Consequently, a flat profile measuring 10 cm in width was successfully fabricated, which incorporates the recycled filler comprising up to 30 % of the resin’s total weight. This achievement was realized by employing a pultrusion system measuring 25 meters in length, coupled with a heated flat plate mold spanning 80 cm. Following the fabrication of the profile, an extensive characterization of both its physicochemical properties and mechanical behavior was conducted to investigate the influence of filler on the ultimate product. The outcomes obtained demonstrate compelling evidence that the incorporation of the recovered filler effectively enhances the interlaminar properties of the pultruded composite materials, thereby underscoring the inherent potential of the charge as a reinforcing agent.

  Abstract
  The investigation into recycling methodologies for composite materials has emerged as a prominent area of study, encompassing both theoretical research and practical implementation. [...]

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• Automated recycling of unidirectional preimpregnated carbon fibre scraps

  T. Gonzalo, J. Seara, G. Aizpurua, K. Garmendia, J. González, J. Pozo

  Materiales Compuestos (2023). Vol. 08 - COMUNICACIONES MATCOMP21 (2022) Y MATCOMP23 (2023), (Núm. 2 - Fabricación y Aplicaciones Industriales - Sostenibilidad y Reciclaje.), 46

  
  

  Abstract

  It is estimated that the aeronautic industry in the European Union produces annually around 10 tn of uncured prepreg scraps, generated mainly from manual and automated lamination processes of composites, and that the treatment cost for these residues is between 3 and 12 € per kilogram. This work presents a technology for the reuse of the unidirectional prepreg scrap using a machine that allows the manufacturing companies, mainly form aeronautic sector, the reuse and valorisation of the leftovers of PREPREG in the workshop, involving a reduction in the economic and environmental impact. The developed solution consists in a machine able to perform the needed processes to reuse the prepreg scrap leftovers in an automatic and efficient way, maintaining the quality and the material properties for the manufacturing of non-critical components. The equipment integrates different technologies that include computer vision to identify the shape of the leftovers and the fibre direction, cutting technology to generate regular rectangular chips aligned with the fibre direction, and a robotic system to pick and place the chips generating an ordered pattern. The result of the process is a material sheet aiming to control the mechanical properties by using homogeneous chips with controlled fibre orientation following a predefined pattern.

  Abstract
  It is estimated that the aeronautic industry in the European Union produces annually around 10 tn of uncured prepreg scraps, generated mainly from manual and automated lamination [...]

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Núm. 3 - Caracterización - Daño, Fractura y Fatiga

• Analysis of the pure shear stress-strain state obtained by biaxial tension-compression test

  S. Horta Muñoz, M. Serna Moreno

  Materiales Compuestos (2024). Vol. 08 - COMUNICACIONES MATCOMP21 (2022) Y MATCOMP23 (2023), (Núm. 3 - Caracterización - Daño, Fractura y Fatiga), 1

  
  

  Abstract

  Characterization of shear properties in unidirectional fibre composite materials can be a complex process due to the difficulty in obtaining uniform and pure shear stress-strain states at the moment of failure. This limits the range of application of the most commonly used standardized methods, as they focus on small deformations. Therefore, this work proposes an alternative solution: the tension-compression test applied to cruciform specimens with ±45° symmetric laminates for the characterization of lamina in-plane shear properties. By using a test method that provides uniform and pure shear stress-strain states, the accuracy of the results can be improved, and the range of application of the method can be expanded. The analysis is based on experimental tests, supported by simulations performed using the finite element method. Special attention is paid to verifying the achieved shear state, and the obtained response is compared with standardized tests that generate non-pure shear stress-strain states on the principal material directions. Additionally, Digital Image Correlation is used during the test to verify the appearance of nonlinear response in different regions of the cruciform specimen, which allows ensuring the validity of the test.

  Abstract
  Characterization of shear properties in unidirectional fibre composite materials can be a complex process due to the difficulty in obtaining uniform and pure shear stress-strain [...]

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• Analytical approach for two-plane bending applied to unidirectional composite plates

  U. Garitaonaindia, N. Carbajal, M. Isasa, F. Mujika

  Materiales Compuestos (2024). Vol. 08 - COMUNICACIONES MATCOMP21 (2022) Y MATCOMP23 (2023), (Núm. 3 - Caracterización - Daño, Fractura y Fatiga), 2

  
  

  Abstract

  In this work, a new analytical procedure is developed to obtain the displacement field of a unidirectional composite plate subjected to bending in two planes. The analysed configuration consists of a plane plate supported at four points to which a point force is applied at the centre. The calculation procedure is based on the strain energy. The effects created by bending moments, torsional moments and shear forces in the plate have been considered. The results obtained analytically have been validated by comparing them with existing literature and with numerical simulations performed with the finite element software ABAQUS. High correlations have been obtained for the values corresponding to the vertical displacements in different alignments of points belonging to the plate, however, the same has not occurred with the distribution of moments.

  Abstract
  In this work, a new analytical procedure is developed to obtain the displacement field of a unidirectional composite plate subjected to bending in two planes. The analysed [...]

  • 2
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• Energy absorption capacity of pre-homologated polyamides against fire for 3D-printing

  U. Morales, A. Esnaola, I. Sukia, U. Olaziregi Cuevas, J. Aurrekoetxea

  Materiales Compuestos (2024). Vol. 08 - COMUNICACIONES MATCOMP21 (2022) Y MATCOMP23 (2023), (Núm. 3 - Caracterización - Daño, Fractura y Fatiga), 3

  
  

  Abstract

  Recent advances in developing new concepts for railway structures demand new lightweight structure concepts not only to reduce their energy consumption but also to reduce the load transmitted to the rail track. Fibre-reinforced polymers (FRP) have gained attention in the railway industry due to their lightweight properties, specific strength and stiffness, and corrosion resistance. Most published studies on the design of lightweight structures, for body and rolling stock, focus on continuous fibre-reinforced thermoset polymers (cFRP). However, derailment risk and fire safety must never be compromised due to this weight-reduction process.   Therefore, new structure designs must be impact resistant and the materials must comply with EN-45545-2. A wide variety of fire protection, self-extinguishing or flame retardant systems for composite components and structures are available in the literature. The influence of flame retardant loading on the impact properties of a continuous carbon fibre reinforced polyamide 6 manufactured by 3D printing of continuous carbon fibre prepregs (FFF) has been analysed in the present work. The impact characterisation of a sandwich panel with a bio-inspired cellular core was carried out in this study. From the results, it has been concluded that the pre-homologated materials (Onyx-FR and cCF/PA-FR) have a similar energy absorption capacity (EAS) to that of the reference reinforced polyamide 6 used in 3D printing processes - FFF.

  Abstract
  Recent advances in developing new concepts for railway structures demand new lightweight structure concepts not only to reduce their energy consumption but also to reduce [...]

  • 3
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• Characterization of induction welded thermoplastic composites

  J. Sogorb, N. Sarin, C. Worrall, J. Wächter, S. Gonzalez, R. Buelga, F. Lasagni

  Materiales Compuestos (2024). Vol. 08 - COMUNICACIONES MATCOMP21 (2022) Y MATCOMP23 (2023), (Núm. 3 - Caracterización - Daño, Fractura y Fatiga), 4

  
  

  Abstract

  Rib-AM project aims to contribute to the development of novel in-situ manufacturing technologies applied to large size components of primary structure of aircrafts. Framed in Clean Sky 2, the activities within Rib-AM are set out to develop a leading-edge (LE) concept based on reinforced thermoplastic materials avoiding mechanical joints between the skin and the ribs. Induction Welding (IW) process has been selected for the integration of the ribs into the leading-edge structure. The development of an appropriate IW process methodology, including the introduction of magnetic flux concentrators and new coil designs, are key to assure the quality and structural integrity of the produced joints. In this research, the mechanical strength of induction welded thermoplastic composites have been evaluated at sample level. Characterization specimens have been obtained by welding: (i) short carbon fiber reinforced polyether ether ketone (SCFR/PEEK), with 10 % carbon content, processed by additive manufacturing – fused deposition modeling; and (ii) multidirectional carbon fiber reinforced polyether ether ketone (CFR/PEEK) laminates processed by oven consolidation. The mechanical characterization of the strength has been carried out by means of the block shear test method. In addition, light optical microscopy has been performed to analyse the SCFR/PEEK - CFR/PEEK interface. Infrared thermography (IRT) has been considered for the non-destructive characterization of the welded joints to evaluate the feasibility of being applied as an inspection method for induction welded structures. IRT results have been validated by X-ray computed tomography.

  Abstract
  Rib-AM project aims to contribute to the development of novel in-situ manufacturing technologies applied to large size components of primary structure of aircrafts. Framed [...]

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• New analytical models for non-symmetric Double Cantilever Beam and End-Notched Flexure tests

  F. Mujika, A. Arrese, J. Gracia, A. Boyano

  Materiales Compuestos (2024). Vol. 08 - COMUNICACIONES MATCOMP21 (2022) Y MATCOMP23 (2023), (Núm. 3 - Caracterización - Daño, Fractura y Fatiga), 5

  
  

  Abstract

  The fundamentals of new analytical models based on energy and coenergy of deformation are explained to analytically address asymmetric interlaminar fracture tests. After reviewing some concepts of laminated beam theory, the energy release rate as a function of coenergy is determined from a global point of view, including in an unprecedented way the contribution of hygrothermal stresses. On the other hand, after the determination of the J integral in the cohesive zone, the conditions required for the asymmetric fracture tests to occur in pure mode in linear elastic fracture are explained, based on the forces and displacements of the crack tip. Furthermore, knowing these forces and displacements, it is possible to determine the energy release rate that corresponds to each fracture mode.

  Abstract
  The fundamentals of new analytical models based on energy and coenergy of deformation are explained to analytically address asymmetric interlaminar fracture tests. After reviewing [...]

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• Use of digital image correlation to quantify the different fracture modes in the Longitudinal Half Fixed Beam (LHFB) test

  M. Lozano, A. López, A. Argüelles, J. Viña, P. Vigón

  Materiales Compuestos (2024). Vol. 08 - COMUNICACIONES MATCOMP21 (2022) Y MATCOMP23 (2023), (Núm. 3 - Caracterización - Daño, Fractura y Fatiga), 6

  
  

  Abstract

  One of the failures with significant practical repercussions in structural elements made of laminated composite materials is the formation and growth of interlaminar cracks (delamination) under static and dynamic loading. Although the cracks can be subjected to three different modes of stress, the material toughness in mode III is higher than in the other two, so delamination mainly occurs in modes I or II. This is true when there is more than one fracture mode acting in the element. However, by using a testing methodology that allows testing in pure or nearly pure mode III, such as the Longitudinal Half Fixed Beam (LHFB) method, it is possible to characterize the material against this mode. Therefore, the degree of purity of mode III, compared to the residual modes I and II, will be an important indicator of the adequacy of the testing methodology. In this research work, the degree of purity of mode III in LHFB-type tests has been determined by using a digital image correlation (DIC) system. This technique allowed for the analysis of displacements in the X, Y, and Z directions in specimens with initial crack lengths of 1, 5, 10, 15, 20, 25, and 30 mm, using AS4/8552 and AS4/3501-6 materials. Considering the displacements measured with DIC during the different tests, it has been possible to determine the level of combination of modes I, II, and III achieved during the tests.

  Abstract
  One of the failures with significant practical repercussions in structural elements made of laminated composite materials is the formation and growth of interlaminar cracks [...]

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• Analysis of multiple high-velocity impact phenomenon in composite laminate plates

  M. Paredes-Gordillo, I. Iváñez, S. García-Castillo, C. Navarro

  Materiales Compuestos (2024). Vol. 08 - COMUNICACIONES MATCOMP21 (2022) Y MATCOMP23 (2023), (Núm. 3 - Caracterización - Daño, Fractura y Fatiga), 7

  
  

  Abstract

  High-velocity impact is one of the most common load states to which composite material structures can be subjected during their service life and can cause a sudden loss of properties favouring its catastrophic failure. Impact loads are usually caused by external elements such as debris, particles carried by the wind, hail, fragments derived from an explosion, etc. All these cases can be represented as high-velocity impacts; however, in general, these impacts are not usually reduced to the action of a single projectile on the structure but can be represented as multiple projectiles that impact simultaneously, or sequentially, on it. This is known as multiple impact phenomenon. In this work a numerical model is developed, using a commercial finite-element software, that allows to analyse the phenomenon of multiple impact in composite material laminates, focusing attention on the wave’s interaction between projectiles. The model is validated with experimental results from the scientific literature for a single high-velocity impact. The interaction among waves generated by the action of two projectiles impacting at the same velocity, and that are separated at a certain distance from each other (simultaneous high-velocity multiple impact), is studied in terms of out-of-plane displacement, and relative movement between projectiles.

  Abstract
  High-velocity impact is one of the most common load states to which composite material structures can be subjected during their service life and can cause a sudden loss of [...]

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• Experimental study of the use of ultra-thin plies in quasi-isotropic laminates under cyclic tension after impact

  C. Sandino, S. Sánchez Carmona, E. Correa Montoto, F. Paris

  Materiales Compuestos (2024). Vol. 08 - COMUNICACIONES MATCOMP21 (2022) Y MATCOMP23 (2023), (Núm. 3 - Caracterización - Daño, Fractura y Fatiga), 8

  
  

  Abstract

  In this work, the authors propose an experimental study on the possible improvement of the mechanical behaviour produced by ultra-thin plies in laminates subjected to cyclic loading after impact. More specifically, this work introduces the use of these plies in carbon fibre quasi-isotropic laminates, with the aim of studying the evolution of impact damage under tensile cyclic loads. To this aim, the behaviour of quasi-isotropic laminates consisting of conventional thickness plies is compared with laminates with 90° ultra-thin plies, keeping the same stacking sequence. When considering the same loading level, the damage evolution shows a lower progress and a later failure for the laminates containing ultra-thin plies.

  Abstract
  In this work, the authors propose an experimental study on the possible improvement of the mechanical behaviour produced by ultra-thin plies in laminates subjected to cyclic [...]

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• Characterisation of the mode I interlaminar fracture toughness in multidirectional interfaces in a 3D-printed composite

  J. Santos, N. Blanco, J. Guerrero

  Materiales Compuestos (2024). Vol. 08 - COMUNICACIONES MATCOMP21 (2022) Y MATCOMP23 (2023), (Núm. 3 - Caracterización - Daño, Fractura y Fatiga), 9

  
  

  Abstract

  Debonding between plies, or delamination, is a critical failure mechanism for laminated composite materials and has been analysed in several scientific investigation. Usually in real applications delamination initiates and propagates between interface layers with different reinforcement orientation. However, most of the experimental works are carried out using unidirectional specimens for determining the interlaminar fracture toughness because in laboratory conditions it is difficult to propagate the crack between multidirectional interface layers without other failure mechanisms that invalidate the test. Among these failure mechanisms, crack plane migration and crack branching at several planes are the most common. In this communication it will be detailed and analyzed the experimental characterization of the interlaminar fracture toughness in multidirectional interfaces of 3D-printed composite materials is detailed, including the manufacturing process of the Double Cantilever Beam (DCB) specimens that warranty crack propagation under pure mode I loading and without plane migration. Finally, a quantitative comparison is carried out between multidirectional interlaminar fracture toughness and the unidirectional one and a fractography analysis is reported.

  Abstract
  Debonding between plies, or delamination, is a critical failure mechanism for laminated composite materials and has been analysed in several scientific investigation. Usually [...]

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• Behaviour of fibre/matrix interface cracks under biaxial stress state caused by edge effect in carbon/epoxy laminates

  S. Sánchez Carmona, C. Sandino, E. Correa Montoto, A. Barroso, F. Paris

  Materiales Compuestos (2024). Vol. 08 - COMUNICACIONES MATCOMP21 (2022) Y MATCOMP23 (2023), (Núm. 3 - Caracterización - Daño, Fractura y Fatiga), 10

  
  

  Abstract

  A recent study about the ''edge effect'' phenomenon in cross-ply laminates made of ultra-thin plies composites has shown the presence of a relevant stress component through the laminate thickness. This fact implies that there is a biaxial stress state in the 90° ply block, which is present both before and after the cyclic loading tests. 4 cross-ply laminates were analysed, only varying the 90° ply block thickness. In each case, the biaxial stress state was obtained, selecting the most detrimental one to analyse the Energy Release Rate (G) with respect to the fibre/matrix interface crack growth. This analysis is performed using a BEM model from a previous study of the authors. An exhaustive microscopic revision is performed both before (only sanded and polished after curing process) and after cyclic testing, corroborating the occurrence of different crack growth of the present longitudinal fibre/matrix interface debonds. In conclusion, the single fibre numerical model using BEM and the experimental microscopic observations shed light on the micromechanical behaviour of the interface cracks which are subjected to a biaxial stress state.

  Abstract
  A recent study about the ''edge effect'' phenomenon in cross-ply laminates made of ultra-thin plies composites has shown the presence of a relevant stress [...]

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• Study of the influence of stacking sequence in the failure of cross-ply laminates manufactured with ultra-thin plies

  M. Velasco*, E. Correa, S. Sánchez-Carmona, F. Paris

  Materiales Compuestos (2024). Vol. 08 - COMUNICACIONES MATCOMP21 (2022) Y MATCOMP23 (2023), (Núm. 3 - Caracterización - Daño, Fractura y Fatiga), 11

  
  

  Abstract

  Numerous studies on the use of laminates manufactured with ultra-thin composite laminates have shown the existence of a significant delay in the appearance of damage, a phenomenon known as the Scale Effect. To study the effect that layer thickness may have on the damage mechanisms that appear at higher values of the load, this work analyses whether the use of ultra-thin laminates exhibits a better behaviour in the instants prior to failure and laminate rupture. For this purpose, different laminates have been manufactured with ultrathin thickness material formed by the same number of laminae oriented at 0 and 90 degrees, but with different stacking sequences, distributing the laminae such that the thicknesses of the resulting layers are different. The laminates have been subjected to uniaxial tension up to values close to the ultimate load in order to observe and compare the different damage morphologies that appear in the 90 and 0 degrees layers, using optical microscopy techniques for the observation of the damage. On the other hand, the loads for which the failure of the selected laminates happens have also been compared. The results obtained from this study show different behaviour of the laminates depending on the thickness of their 0 and 90 degrees layers in the moments prior to failure and at the instant when failure occurs.

  Abstract
  Numerous studies on the use of laminates manufactured with ultra-thin composite laminates have shown the existence of a significant delay in the appearance of damage, a phenomenon [...]

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• Study of delamination behavior in adhesive joints with epoxy-based adhesive under Mode II

  P. Vigón, A. Argüelles, I. Viña, M. Lozano, J. Viña

  Materiales Compuestos (2024). Vol. 08 - COMUNICACIONES MATCOMP21 (2022) Y MATCOMP23 (2023), (Núm. 3 - Caracterización - Daño, Fractura y Fatiga), 12

  
  

  Abstract

  This study experimentally analyses the phenomenon of delamination under static and fatigue loading in mode II using the standardized End-Notched Flexure (ENF) test. Adhesive joints made of two epoxy matrix laminates reinforced with unidirectional carbon fiber are studied, bonded with an epoxy adhesive, and subjected to environmental degradation in a saline environment for exposure periods of 1, 2, 4, and 12 weeks. By conducting initial static tests on the joints, we identified crucial values for the rate at which energy is released under mode II conditions. These values served as a benchmark to establish the approach for dynamic fatigue testing. Our objective was to generate characteristic curves that illustrate how these adhesive joints behave when fatigue delamination begins, while also assessing the impact of varying exposure periods on their performance. To enhance result interpretation, we employed a probabilistic model rooted in the Weibull distribution to analyse the experimental data. The results show that adhesive joints experience a decrease in their delamination resistance when exposed to a saline environment.

  Abstract
  This study experimentally analyses the phenomenon of delamination under static and fatigue loading in mode II using the standardized End-Notched Flexure (ENF) test. Adhesive [...]

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• Thermoplastic weld fatigue behaviour analysis using structural health monitoring sensors data

  M. Mazzeschi, K. Nuñez-Carrero, M. Fernandez, E. Cañibano, J. Merino

  Materiales Compuestos (2024). Vol. 08 - COMUNICACIONES MATCOMP21 (2022) Y MATCOMP23 (2023), (Núm. 3 - Caracterización - Daño, Fractura y Fatiga), 13

  
  

  Abstract

  Thermoplastic composite joints show many advantages in comparison to conventional fasteners. However, thermoplastic welding of primary aircraft structures is still a certification issue. Long and extensive fatigue and test campaign is required for a depth understanding of damage progression. In fact, scarce historical data are currently available and the joint fatigue performances are extremely sensitive to numerous welding process parameters. In this context, Structural Health Monitoring (SHM) technologies consists of a built-in sensors network providing real-time condition and the damage state of a structure. SHM brings several benefits. First of all, SHM ensures safety in-flight through continuously assessing damages and alerting if strength reduction approaches acceptable limits. The data obtained are useful for future structure retrofitting and new developments. Moreover, SHM has the potential to support and speed up the certification of thermoplastic composite joint. SHM data give added value to each individual fatigue test contributing to a greater understanding of damage progression and making fatigue campaign shorter and more efficient. In the present work, both quasi-static as well as fatigue tests were conducted to evaluate performances of thermoplastic induction welded joints. Strain gauges and purpose-designed electromagnetic-based SHM sensor were integrated into the specimens in order to collect useful data during tests in three main cases: lap-joint specimens manufactured (i), (ii) with two different set of process parameters and (iii) with an artificially generated lack of weld at the joint interface. The approach proposed and data collected by the sensors has provided valuable information for understanding damage propagation in this kind of joint.

  Abstract
  Thermoplastic composite joints show many advantages in comparison to conventional fasteners. However, thermoplastic welding of primary aircraft structures is still a certification [...]

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Núm. 4 - Sostenibilidad y Reciclaje

• Life cycle assessment of new Talgo lightweight prototypes

  . M.Cerdeira*, E. Guerra, F. García, J. Fernández, . V.Meroño

  Materiales Compuestos (2024). Vol. 08 - COMUNICACIONES MATCOMP21 (2022) Y MATCOMP23 (2023), (Núm. 4 - Sostenibilidad y Reciclaje), 14

  
  

  Abstract

  The European rail network is largely electrified, and rail emits far less CO2 than equivalent travel by road or air. It accounts for only 0.4 % greenhouse gas emissions from EU transport, while all EU transport accounts for 25% of the EU’s total emissions. Additionally, rail is the only transport that between 1990 and 2017 has consistently reduced its emissions and energy consumption, while increasingly using renewable energy sources. Following this green line, this article presents the Life Cycle Assessment (LCA) study of new generation trains, mainly based on lightweighted primary structures made of composite material (about 30-50% weight loss compared to conventional ones). The composite materials are novelty in the railway sector. Their introduction brings a clear advantage from the point of view of train capacity or energy/infrastructure canon savings. However, it needs to be justified from the LCA point of view. Two different stages are developed in this article. An LCA of the new prototypes (production, assembly, transport and use phase). It is completed with an LCA of conventional structures. The second phase presents a comparison between the environmental impact produce using CFRP materials or metallic materials at the end of a useful life (EoL) of a carbody. The results indicates that, at EoL, the composite material would be more economically and environmentally attractive than the current materials.

  Abstract
  The European rail network is largely electrified, and rail emits far less CO2 than equivalent travel by road or air. It accounts for only 0.4 % greenhouse gas emissions from [...]

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• Bio-based recyclable crosslinked polyurethanes based on a thermally reversible Diels-Alder adduct

  A. Restrepo Montoya, I. Larraza, K. Gonzalez, O. Echeverria Altuna, I. Harismendy, A. Saralegi, A. Eceiza

  Materiales Compuestos (2024). Vol. 08 - COMUNICACIONES MATCOMP21 (2022) Y MATCOMP23 (2023), (Núm. 4 - Sostenibilidad y Reciclaje), 15

  
  

  Abstract

  Thermosets comprise a family of chemically cross-linked networks formed by irreversible chemical reactions, resulting in polymers with outstanding properties such as superior mechanical properties, high thermal stability and chemical resistance. However, their high stability precludes reprocessing or recycling, thus making it difficult to move towards a circular economy and sustainability. During the last years, research has focused on dynamic chemistry, in order to introduce reversible bonds along the polymer chain and synthesize reprocessable and/or recyclable thermosets. In this context, the Diels-Alder reaction is of special interest, as it can give thermoreversible reactions with a relatively low coupling and high decoupling temperature. Within this work, a trifunctional polyol containing the furan-maleimide Diels-Alder adduct has been developed to facilitate the recycling of cross-linked polyurethanes. The maleimide-furan adduct forms covalent bonds at low temperatures, but when heated these bonds break down, splitting the polymer chain into smaller chains and softening the polymer, allowing it to be reprocessed. Then, when the temperature drops, the bonds between the maleimide and the furan are reformed and the polymer regains its mechanical properties. Thereby, a thermoset polyurethane was synthesized reacting the triol containing Diels-Alder adduct with a polymeric isocyanate. The reprocessability and/or recyclability of the synthesized polyurethane was then evaluated by breaking it into small pieces and reprocessing them by pressing at high temperature, in order to obtain new sheets and evaluate their mechanical properties, being similar to the original ones.

  Abstract
  Thermosets comprise a family of chemically cross-linked networks formed by irreversible chemical reactions, resulting in polymers with outstanding properties such as superior [...]

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• Impact behavior of thermoplastic matrix composites reinforced with basalt fibers and manufactured by RTM

  M. Baskaran, R. Hoto, J. García-Manrique, J. Aurrekoetxea

  Materiales Compuestos (2024). Vol. 08 - COMUNICACIONES MATCOMP21 (2022) Y MATCOMP23 (2023), (Núm. 4 - Sostenibilidad y Reciclaje), 16

  
  

  Abstract

  Reducing the environmental impact of composite materials by using new matrices and fibres, as well as a manufacturing process that allows obtaining high-quality standards, is on the strategic agenda of academia and industry. Replacing thermosetting matrices with thermoplastics is a challenging vector for improvement, facilitating recycling. Regarding the fibres, natural fibres of mineral origin, such as basalt, reduce the ecological footprint in the raw material extraction phase. Characterising the impact behaviour of these new composites is necessary to identify potential applications. Otherwise, direct comparison with reference materials is essential since differences in the manufacturing process, fibre content, or test conditions make it impossible to put the new material in context. In this paper, we compared the impact properties of two thermoplastic-matrix (pCBT) composites manufactured using resin transfer moulding (RTM). On the one hand, as a reference material, the pCBT is reinforced with carbon fibres, and on the other hand, with basalt fibres. The results are better for the composite reinforced with basalt fibres, regardless of whether the properties are compared in absolute terms (×2.2), in weight reduction (×1.8) or in reduction of energy consumed during the primary production of the fibres (×4.4). 

  Abstract
  Reducing the environmental impact of composite materials by using new matrices and fibres, as well as a manufacturing process that allows obtaining high-quality standards, [...]

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• Elastomeric composite materials reinforced with natural fibers and with self-healing capacity

  S. Utrera-Barrios, O. Lopes, M. Hernandez Santana

  Materiales Compuestos (2024). Vol. 08 - COMUNICACIONES MATCOMP21 (2022) Y MATCOMP23 (2023), (Núm. 4 - Sostenibilidad y Reciclaje), 17

  
  

  Abstract

  Elastomeric composite materials are widely used in multiple applications, especially in the automotive industry; however, they have the drawback of being difficult to recycle, generating a significant environmental impact. For this reason, in recent years there has been an increase in research for the development of self-healing and biodegradable materials that minimize this impact by extending their lifetime. In this context, the aim of this work is to design a new generation of self-healing elastomeric composite materials using additives of natural origin. For this, epoxidized natural rubber (ENR) and cellulose propionate (CP) were used as matrix, reinforced with cellulose fibers. Self-healing was achieved by combining the flow of the thermoplastic (CP) phase (extrinsic mechanism) and the formation of hydrogen bonds between the ENR and the CP (intrinsic mechanism). A promising repair efficiency of 95% was obtained, as well as an increase in tensile strength in the presence of cellulose fibers, without affecting the healing capacity of the material. Therefore, this work overcomes the well-known dichotomy between mechanical performance and self-healing and constitutes a new contribution in the field of self-healing elastomeric composites using bio-based additives.

  Abstract
  Elastomeric composite materials are widely used in multiple applications, especially in the automotive industry; however, they have the drawback of being difficult to recycle, [...]

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• New life for aeronautical dry carbon fiber

  A. Calero, T. Blanco Varela, J. Sistach

  Materiales Compuestos (2024). Vol. 08 - COMUNICACIONES MATCOMP21 (2022) Y MATCOMP23 (2023), (Núm. 4 - Sostenibilidad y Reciclaje), 18

  
  

  Abstract

  Our latest generation aircraft are more efficient by design, lighter and emit on average 25% less CO2 than previous generation aircrafts. Lightweight materials like composites have contributed significantly to reach the current emissions levels, like the A350 with more than 50% of structural weight made of composites. However, composites drive also the environmental footprint of the aircraft life-cycle without considering the operational phase, involving currently important drawbacks in terms of energy consumption and waste recycling. The transition towards a composite circular economy needs to be anticipated due to the aviation sector de-carbonization challenge as well as the regulation evolution. This transition will be leveraged by several elements, being the composite recycling one of the most important, due to the need to transform the composite waste from production and end of life into new added value materials. For this, the development of efficient composite recycling technologies to not only recover energy during incineration but also high value recycled carbon fibers and semi-products are needed. This project was focused on the recycling of dry carbon fiber scrap, which can proceed from part production by infusion technologies (e.g. RTM) or from pyrolysis of end of life composite part. The approach was to obtain a non-woven mat from the dry fiber scrap, following a mechanical process, which was, then, fully characterized to identify potential applications in aeronautical field. Different approaches of hybridization of the recycled non-woven fabric with virgin fabric were also evaluated.

  Abstract
  Our latest generation aircraft are more efficient by design, lighter and emit on average 25% less CO2 than previous generation aircrafts. Lightweight materials like composites [...]

  • 0
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• Thermochemical recycling of epoxy matrix composite materials with Diels-Alder bonds

  I. Lorero, C. Bravo, M. Campo, A. Jiménez, S. Prolongo, I. Lorero

  Materiales Compuestos (2024). Vol. 08 - COMUNICACIONES MATCOMP21 (2022) Y MATCOMP23 (2023), (Núm. 4 - Sostenibilidad y Reciclaje), 19

  
  

  Abstract

  The high cross-linking degree of thermosetting resins, which gives them remarkable mechanical properties, also implies an irreversible structure that impedes proper recycling at the end of life. This problem influences both thermosetting matrices and composite materials, since the crosslink irreversibility of the matrix hinders the recovery of the fibers. One way to solve this problem is the development of new thermosetting resins that incorporate Diels-Alder thermo-reversible bonds. The introduction of Diels-Alder bonds allows thermosets to have a polymeric network capable of disengaging at temperatures above 90 °C, acquiring certain fluidity and recyclability. However, its composition and curing cycle must be carefully adjusted to avoid undesired chemical reactions and to maintain certain mechanical properties, since the addition of Diels-Alder bonds in high contents usually results in a notable embrittlement of resin. In the present work, the manufacture of an epoxy matrix composite material with 60% Diels-Alder bonds reinforced with carbon fiber is developed, which shows mechanical properties similar to those of a conventional epoxy resin laminate. After that, the recovery of the fiber is addressed thermochemically by dissolving the matrix in dimethyl sulfoxide at 150 °C, achieving the reuse of the fiber to manufacture new composite materials with mechanical properties comparable to the original.

  Abstract
  The high cross-linking degree of thermosetting resins, which gives them remarkable mechanical properties, also implies an irreversible structure that impedes proper recycling [...]

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• Solvolysis of carbon fibre reinforced composites under mild conditions

  L. Fulgencio, A. Asueta, S. Arnaiz, J. Leivar, I. Amundarain, R. Miguel, A. Iruskieta, L. Fulgencio

  Materiales Compuestos (2024). Vol. 08 - COMUNICACIONES MATCOMP21 (2022) Y MATCOMP23 (2023), (Núm. 4 - Sostenibilidad y Reciclaje), 20

  
  

  Abstract

  Carbon fibre reinforced composites (CFRP) are key in different industrial sectors as they combine lightness and robustness. This circumstance and the growing need to take advantage of the resources of any product, has triggered a strong demand to establish sustainable technological solutions that allow the effective use of composite materials: resins (matrix) and fibres (reinforcement). Limited to mechanical recycling, recycling alternatives for CFRP with thermosetting resins have focused on thermochemical treatments, usually pyrolysis to recover the fibres, degrading the matrix. In addition to thermal routes, solvent treatments under supercritical conditions have also been studied. However, these processes exclude resin recovery and involve a partial loss of mechanical properties of the fibres due to the heat treatment (450-550 °C). As an alternative, a solvolysis using mild conditions is proposed to treat CFRPs with amine-hardened epoxy resins, so that the fibres are recovered with all their properties and the organic matrix is materially valorised. This process is applied to reference materials of known composition and validated with real residues with good results in terms of degree of resin decomposition. The recovered fibres show almost resin-free surface and seem to have mechanical properties comparable to those of virgin fibres.

  Abstract
  Carbon fibre reinforced composites (CFRP) are key in different industrial sectors as they combine lightness and robustness. This circumstance and the growing need to take [...]

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• Thermoset polyurethanes based on recycled and biobased constituents

  E. Mendiburu-Valor, I. Larraza, O. Echeverria Altuna, I. Harismendy, A. Eceiza

  Materiales Compuestos (2024). Vol. 08 - COMUNICACIONES MATCOMP21 (2022) Y MATCOMP23 (2023), (Núm. 4 - Sostenibilidad y Reciclaje), 21

  
  

  Abstract

  Poly(ethylene terephthalate) (PET) is one of the most consumed plastics in the world, so it is very common to find it in the sea or ocean. Thermomechanical recycling is normally used for urban and industrial PET waste, but it is not suitable for highly degraded marine litter. Chemical recycling of marine PET litter is presented as an alternative for the valorization of this highly degraded waste. The bis(2-hydroxyethyl) terephthalate (BHET) monomer obtained can be used in the synthesis of new polymers. This study explores the potential of using BHET for the synthesis of high modulus and high strength thermoset polyurethanes. In addition, a renewable reagent, such as a polyol derived from castor oil, has been used to synthesize a recycled and biobased polyurethane thermoset (BHET-BioPU). The resulting BHET-BioPU has been thermally, thermo-mechanically and mechanically characterized to evaluate its potential applications. In addition, the recyclability by glycolysis of the BHET-BioPU has been demonstrated, thus advancing towards a circular economy. The results of this study provide fundamental knowledge for the development of sustainable, environmentally friendly and high performance materials and recyclable as well, materials, and represent an important achievement in the global effort to reduce dependence of fossil resources and plastic pollution.

  Abstract
  Poly(ethylene terephthalate) (PET) is one of the most consumed plastics in the world, so it is very common to find it in the sea or ocean. Thermomechanical recycling is normally [...]

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• Validation of a laboratory-scale technology for complete recycling of wind turbine blades

  A. Lopez-Urionabarrenechea, A. Serras-Malillos, E. Perez-Perez, B. Perez-Martinez, E. Acha, B. Caballero, A. Lopez-Urionabarrenechea

  Materiales Compuestos (2024). Vol. 08 - COMUNICACIONES MATCOMP21 (2022) Y MATCOMP23 (2023), (Núm. 4 - Sostenibilidad y Reciclaje), 22

  
  

  Abstract

  This paper presents the experimental validation of a thermal treatment technology to recover added-value substances from the plastic matrix of end-of-life wind turbine blades, when these are subjected to a pyrolysis process to recover the glass fibres. The experiments have been carried out in a laboratory installation consisting of two reactors in series, in which pyrolysis and thermal treatment of pyrolysis gases and vapours take place, respectively. The application of this treatment enables a 25 wt.% reduction in the production of pyrolysis liquids, increasing the production of gases in an equivalent way and without compromising the pyrolysis conditions to be used to recover the glass fibres. The two-phase liquids are converted into single-phase aqueous ones, while the hydrogen concentration in the gases increases from 4 % to almost 50 % in volume. This high concentration of hydrogen in the gases allows them to be used as a source of hydrogen for various applications. Consequently, the technology demonstrates that the plastic matrix of wind turbine blades can be valorised in a pyrolysis based recycling process.

  Abstract
  This paper presents the experimental validation of a thermal treatment technology to recover added-value substances from the plastic matrix of end-of-life wind turbine blades, [...]

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• New functionalities and recycling opportunities for dynamic epoxy-based composites

  A. Rekondo*, I. Azcune, A. Huegun

  Materiales Compuestos (2024). Vol. 08 - COMUNICACIONES MATCOMP21 (2022) Y MATCOMP23 (2023), (Núm. 4 - Sostenibilidad y Reciclaje), 23

  
  

  Abstract

  Reprocessable, repairable, and recyclable thermoset composites have the potential to improve the circularity of composites and ensure their sustainability. Disulfide-based epoxy matrices are under development to meet the specifications of key sectors (transport, wind energy, etc.). The manufacturing of reinforced composites by different techniques (infusion, prepregs, etc.) has been validated (TRL 4-5). The incorporation of new functionalities, such as fire resistance, and the validation of recycling are now on the table. Conventional chemical recycling separates the reinforcement from the composite for reuse, leaving aside the polymer matrix. The new functionalities incorporated require recovery and validation of the matrix. Dynamic resins allow milder conditions to be applied during recycling, and the challenge remains to find new applications that reuse these recycled products. On the other hand, the rational use of resources demands for new recycling routes that do not require separation of the components, apply few steps, be economically viable, and maintain the value of the reinforcement and the matrix. Vitrimers allow the thermoforming of composite parts through the application of heat and pressure. This process opens the way from reusing final parts with new shapes to generating short new fibre composites from mechanical pre-crushing. This communication will present the latest developments and objectives of several European projects funded under the HE framework (SURPASS, GA no. 101057901; MC4, GA no. 101057394) in which work on the maturity of the technologies is in progress.

  Abstract
  Reprocessable, repairable, and recyclable thermoset composites have the potential to improve the circularity of composites and ensure their sustainability. Disulfide-based [...]

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