Abstract

La principal dificultad que se encuentra en el momento de diseñar estructuras
con materiales compuestos es la falta de modelos constitutivos que permitan si- mular su
comportamiento.  Las técnicas analíticas convencionales utilizadas para el estudio de materiales
simples isótropos no resultan adecuadas para el análisis de materiales compuestos. Tampoco ha
resultado satisfactoria la representación de un compuesto mediante un único material ortótropo con
propiedades del conjunto. Puede observarse en distintas referencias los intentos que ha habido para
modelar el comportamiento de materiales compuestos, utilizando la técnica de elementos fi- nitos
para el análisis y diseño de estructuras, donde la correlación entre los análisis y los resultados
experimentales no resulta satisfactoria (Ali, 1996) (Klintworth y Macmillian, 1992). El proceso de
diseño de componentes en materiales compuestos se ha basado, principalmente, en métodos empíricos,
observándose en la literatura la ausencia de análisis o simulaciones del comportamiento de
materiales compuestos sometidos a niveles de esfuerzos que sobrepasan el límite elástico.

Abstract

Materiales Compuestos is the journal edited by the Spanish Association of Composite Materials (AEMAC). Its first volume has been published in year 2017. The journal aims to be a gathering point for researchers, developers, technicians, engineers, scientists and, summarizing, all those professionals conducting their activity in the field of composite materials.

The main objective of the journal is to disseminate the scientific and technological developments made in the field of composite materials, which might be of interest to AEMAC and to all other professionals to whom this journal is addressed. Under this scenario, are of special interest for the journal all works developed in Spain, Portugal and Latin America, as well as works from any other origin that might be of interest to be shared in the journal’s forum.

Abstract

Compression After Impact (CAI) test is normally used for the assessment of damage tolerance of composite laminates. The applicable specification for the execution of these tests is AITM 1-0010. However, for thicknessess under 4mm were buckling occurs, the applicable specification is the AITM 1-0077, which introduces the use of anti-buckling tooling covering the entire surface of the specimens. The tooling, which is used in the aeronautical industry  for the testing of thin specimens presents two problems which are the difficulty of assembly and of obtaining realiable results, and the visibility of the specimen during the test.

This work comprises the design, manufacturing and validation of a novel anti-buckling device for compression after impact thin specimens. For that purpose, a study of the specification toolings along with a review of the already developed anti-buckling tooling literature has been carried. As part of the validation process three series of impacted specimens of 3mm thickness.

This activity is developed as part of the project CERES, which is framed under Clean Sky 2, and has the main objective of validating the manufactured anti-buckling tooling. This tooling has been developed as an innovative solution for its application in compression after impact thin specimens. 

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

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

Heat dissipation is an issue that is acquiring great importance to increase the efficiency in the utilization of the energy and extending the lifespan of the equipment. Traditionally, heat dissipation has been carried out using metals, but the increase in the requirements of equipment and devices, composites have gained importance. Graphite based composites have relevance in heat dissipation, particularly when the disperse material is a metal or metal carbide. The reason is the great value of thermal conductivity combined with good mechanical properties and lightness. Research has focused until nowadays on the composite graphite-MoC, although there are other composites with great potential, as that proposed in this manuscript: graphite- Cr3C2. The preparation of the composite graphite-Cr3C2 consisted in mechanical mixing of the staring powders, subsequent obtaining of the green compact of 40 mm in diameter and, finally, sintering at 2000 °C for 20 minutes under an applied pressure of 30 MPa in the Spark Plasma Sintering apparatus. The sintered material exhibited electrical and thermal conductivities in the in-plane direction of 1.08 MS/m and 215 W/m · °C, respectively, and a flexural strength of 113 MPa, which makes this material a suitable candidate for its application in heat dissipation.

Abstract

Carbon fibre reinforced polymer composite material structures continue to be, despite the tremendous technological maturity achieved in recent decades, one of the most promising options to address the challenges of the aeronautical industry with respect to behaviour in the face of efforts such as improvements, regarding weight or costs.

Ongoing demands to address major societal challenges, promote industrial leadership in Europe, and address aviation decarbonisation for the purpose of protecting the environment drive the demand for more optimal materials designed to improve these aspects.

The previous tasks carried out to complete the test campaign will be described, showing its plan and design, details of preparation, assembly of the specimens and the execution of the tests. The philosophy proposed by Airbus (ADS) is presented with the consolidation of admissible design against alterations of the material that could realize its evolution or arise in the manufacturer's batches.

Observing changes in the material, leading to the improvement of its mechanical and handling characteristics, a comparison has been made by Airbus with the one used previously for the determination of admissible design. It is intended to incorporate assessments of effects associated with the process of its industrialization. Once the results and analyzes are available, the normalized results of the conclusions would be presented.

The activity carried out is included within the CERES project (Advanced Rear End Structural test program), belonging to the Clean Sky 2 Joint Undertaking European research aeronautical program.

Abstract

One of the main advantages of using reinforced thermoplastic materials is the possibility of joining different parts by welding. Welding process avoids the use of mechanical joints, which increase the weight of the component and the manufacturing time; as well as adhesive joints, where it is difficult to ensure their quality.

Welded joints are of special interest when applied in assembly processes with a high production rate. However, welded joints on high-rate components require research into new materials, processes, and inspection techniques. In this line, the present work analyzes the results obtained from different welded joints through heating by electrical resistance without contact. This characterization study includes mechanical, microstructural and physical-chemical properties analysis, as well as its evaluation through non-destructive inspection techniques. As a result, a deeper knowledge of the materials and processes has been obtained, including the effect of the different welding processing parameters.

Different opening mode mechanical tests are presented in this study, as well as thermal analysis by differential scanning calorimetry to evaluate the effect of temperature and time applied during the welding process on the final properties. The quality of the process in the different joining elements has been verified with inspection by means of infrared thermography, correlating indications in the level of IR radiation with localized variations microscopy features (i.e.: amount of resin). In addition, a microstructural study has been carried out to assess the fiber/resin content of the material in the joint areas, as well as a complementary analysis using computed tomography and ultrasound.