Scipedia: Documents published in 2024

LIGTHWEIGHT STRUCTURE OF HIGH SPEED TRAIN (TALGO) CARBODY. COMPOSITE IN RAILWAY ROLLING STOCK

Francisco José García Piñeiro — Fri, 19 May 2023 10:17:11 +0200

Currently, the railway sector demands novel lighter designs for the structural components of rolling stock that compensate for the increase in weight due both to the incorporation of new technologies for passenger comfort and experience, as well as to face new environmental challenges (reduction of emissions, consumption power, etc).

With this objective in mind, Aernnova-Talgo-FIDAMC-Tecnalia have proceeded to develop a car body structure design for a high-speed passenger car that introduces up to 70% of high-performance composite material (CFRP). This makes it possible to achieve weight reductions of more than 20% when it is compared to the original 100% aluminum structure.

The solution combines frame, sidewalls and roof in an integral solution in CFRP with the usual solution in welded aluminum for the closing endwalls.

The use of composite material for these structures also implies the introduction of non-conventional manufacturing methods for the railway sector (Semipreg-Sandwich-Pultrusion) with curing outside of autoclave and compliance with the demanding fire and smoke requirements of the EN 45545.

The final objective of the project is the bench validation of the prototype according to the usual standards of the railway sector, EN 12663.

Wingbox Component Integration by Liquid resin Infusion

Luis Rubio — Thu, 18 May 2023 21:16:05 +0200

Composite epoxy resin based structures are widely and increasingly used at aerospace sector. Conventional composite processing requires the use of pre-impregnated raw material that requires refrigerated storage and autoclave use for the component consolidation. ADS jointly with Mtorres and with Hexcel support, have been intensely involved in the development of a Dry fibre automatic lamination, Liquid resin infusion and oven consolidation technology process (shortly referred as LRI) which permits the elimination of this energy consuming steps in order to improve the sustainability and reduce manufacturing costs so as allowing an increasing component integration reducing structural weight.

A LRI integrated lower cover with spars and stiffening elements has been delivered by CBC for its integration into an Outer external wing box specimen for its test, scheduled as the latest Milestone of Clean Sky 2 AIRFRAME ITD project (supported also by IIAMS, MALTA, CERTERIN R&T projects). This specimen will be assembled through a jiggles process with the delivered thermoplastic Upper Cover. The full scale test will complete the testing pyramid after having completed the previous steps: coupon, detail, panel level.

This partial Lower cover demo so as the Full Scale test, in which it will be integrated, will contribute to the TRL6 maturity status of the technology.

Improvement of electrical resistivity of cement mortar through nanotechnology

Angel Yedra Martínez — Thu, 18 May 2023 15:32:04 +0200

The diffusion or permeability of ions or gases through the cement matrix is key in the degradation of reinforced concrete for marine applications. The delay in ion diffusion has been an important approach to extend the life of this type of materials. In this work it is detailed how reduce degradation of cement mortar using nanotechnology. The addition of nanoparticles to the cement paste has important implications for the hydration and microstructure, reducing porosity and improving mechanical properties. In this study, different nanoparticles have been used to reduce the porosity of mortars evaluating this improvement by means of electrical resistivity measurements. It is perfectly established the porosity reduction with the increasing of electrical resistivity. Reduction of porosity minimises the intake of aggressive agents into the mortar in a meaningful way, retarding the corrosion of metal reinforcement. Nanoparticles addition (<10%) within cement mortar have allowed to increase the electrical resistivity in up to 112% regarding to control sample, without modifying of mechanical properties.

Improvement of the impact behavior of forged composite plates reinforced with continuous fiber tapes

Udane Olaziregi — Thu, 18 May 2023 13:54:04 +0200

The conception of structural components using thermoplastic composite materials faces a dilemma when selecting the material/manufacturing process pairing. Continuous fiber-reinforced composites offer the best properties, but their design freedom is limited to shell-type parts. On the other hand, manufacturing processes for discontinuous fiber, such as injection (LFT) and forging (GMT), allow the production of complex geometries, but their mechanical properties are substantially lower. In fact, LFT and GMT are important in the current automotive industry, but their applications are limited to semi-structural components or internally complex geometries whose functionality is more focused on function integration rather than supporting high mechanical loads. The hybridization of discontinuous fiber composites with continuous fiber materials presents itself as a promising approach to achieve a synergistic effect from both technologies.

In this study, the impact behavior of glass fiber-reinforced polyamide forged plates (GMT) was characterized, along with their hybridization with unidirectional carbon reinforcements. In the first phase, the effect of the processing temperature was investigated, concluding that increasing the temperature promotes the compaction between the two materials, resulting in improved impact resistance. Specifically, a 14% increase was observed in both maximum force and dissipated energy. In the second phase, the effect of hybridization with unidirectional tapes as reinforcement was analyzed, showing the same positive effect. The hybridization led to a 20% improvement in maximum force and a 36% increase in dissipated energy.

CUSTOMISED AND INTEGRATED SOLE FOR CYCLING MANUFACTURED BY 3D PRINTING OF CONTINUOUS CARBON FIBRE REINFORCED POLYAMIDE

Aritz Esnaola — Thu, 18 May 2023 13:46:09 +0200

Customised cycling soles are extremely complex to design and manufacture since the plantar pressure distribution and anatomical shape are specific for every foot. This paper explores the potential of topology optimisation and additive manufacturing of continuous fibre reinforced plastic. The highly abstract material distribution resulting from the topology optimization software was interpreted considering the additive manufacturing constraints for getting the detailed design. The selected printing strategy consisted of concentric fibre orientation to better fit load-paths, and the build-orientation aimed to maximise the fibre content, resulting in 30 hours for printing each sole. Regarding the specific stiffness at the hallux and the hell, the new soles are at least 60% higher. Therefore, it has been confirmed that the proposed approach is a powerful tool to design the cycling shoe adapted to the local stiffness of each foot.

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

Jon Aurrekoetxea — Thu, 18 May 2023 13:45:04 +0200

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).

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

Ana Cristina Restrepo Montoya — Thu, 18 May 2023 12:49:03 +0200

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.

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

Inés Iváñez — Thu, 18 May 2023 11:58:02 +0200

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.

Thermoset polyurethanes based on recycled and biobased constituents

Arantxa Eceiza — Thu, 18 May 2023 11:50:06 +0200

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.

Tecnologías de fabricación avanzadas en material compuesto termoplástico dirigidas al sector aeronáutico

Mariasun Mendizabal — Thu, 18 May 2023 11:03:03 +0200

La fabricación avanzada en materiales compuestos termoplásticos es clave para satisfacer los requerimientos del sector aeronáutico. Las ventajas diferenciadoras de los polímeros termoplásticos de alto rendimiento frente a las resinas termoestables, hace que estos materiales sean cada vez más demandados en el sector. Es clave su capacidad de reprocesado que permite 1) la automatización de los procesos, 2) la utilización de la tecnología de unión por soldadura entre sus componentes y 3) aplicar criterios de reciclabilidad y reutilización, imposibles para los materiales termoestables. Su mayor tenacidad y su cumplimiento de los estándares más estrictos de llama, humo y toxicidad aportan un plus importante a sus prestaciones. Polieterimida (PEI), Sulfuro de Polifenileno (PPS), Polieteretercetona (PEEK), Polietercetonacetona (PEKK) y el novedoso poliariletercetona (PAEK) son las matrices empleadas en esta tecnología de materiales compuestos termoplásticos de altas prestaciones. En función de la tipología del componente final, se selecciona la tecnología de procesado más adecuada, dependiendo de aspectos como geometría de pieza, tamaño y número de piezas a fabricar. El objetivo del presente trabajo fue la exploración de tecnologías de procesado de composites termoplásticos, tales como: Termoconformado de láminas compuestas (organosheet), obtención de laminados customizados (tailored sheet consolidation) y moldeo de escamas y/o pellets reforzados mediante compresión (T-BMC, Thermoplastic Bulk Moulding Compound) a través del desarrollo y puesta a punto de la fabricación de prototipos. Los resultados demostraron que estas tecnologías cumplen los requerimientos exigidos por el sector aeronáutico tanto en procesabilidad como en propiedades.

Impact properties of layer by layer in-situ UV cured composites

Imanol Ruiz de Eguino — Thu, 18 May 2023 10:05:03 +0200

Fast and eco-friendly composite curing technologies are highly sought after, and ultraviolet (UV) curing offers both features. UV curing can be applied as a bulk curing technology as long as light arrives at all the points in the material with enough intensity. Additionally, the outer layer cures almost instantaneously, reducing the emission of volatile organic compounds. Despite its benefits, the implementation of UV curing technology in composites manufacturing is still in an early stage, and more basic knowledge about its principles needs to be generated. For instance, when curing considerably thick laminates, the light arriving at the points in the material further from the exposed surface is insufficient for a one shot consolidation, requiring a layer-by-layer curing strategy.

In the present paper, we explore several approaches for the layer-by-layer curing of a glass fibre reinforced unsaturated polyester composite. We assessed the impact properties of the manufactured laminates through drop weight low velocity impact tests to quantitatively evaluate the different approaches. We found that the laminate cured in three steps, applying four plies by shot, had the best impact performance, followed by the composite cured in two steps. On the other hand, the laminate cured in one shot had the worst impact properties, dissipating 20% less energy than the best performing laminate. Therefore, we conclude that the bonding of the UV cured laminates is tough and that the residual stresses induced during manufacturing are lessened the thinner the layers cured in each step are.

New functionalities and recycling opportunities for dynamic epoxy-based composites

Arrate — Thu, 18 May 2023 08:13:04 +0200

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.

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

Unai Morales — Thu, 18 May 2023 07:56:15 +0200

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.

ENDURING PREPREGS THANKS TO THE USE OF DYNAMIC EPOXY RESINS

Aratz Genua — Wed, 17 May 2023 11:49:02 +0200

The use of CIDETEC's patented 3R technology allows the development of thermoset composites that are intrinsically Reprocessable, Recyclable and Repairable (3R). These materials are very interesting for sectors as diverse as energy, transport, and construction, as they maintain the high performance of conventional thermoset composites and can be processed using common manufacturing technologies. The use of prepregs is one of the methods used to manufacture thermoset composites, but it is a labour-intensive and cost-intensive process. In addition, the epoxy matrix of prepregs, which is partially cured (called B-phase) and sticky, requires them to be stored cold (refrigerated or frozen) and, once the due date has passed, they cannot be used to form a consolidated laminate because of their lack of adhesion. The dynamic character of the 3R epoxy resin described here makes it possible to manufacture what we have called "enduring prepregs", which are (semi-)cured, non-perishable prepregs, with the advantage that they can be stored at room temperature without losing their adhesion capacity. Moreover, it is possible to process them using techniques as diverse as AFP (automated fibre placing) or thermoforming to manufacture multilayer composite parts. This communication will present the latest advances and the objectives of several European projects funded under the H2020 (CARBO4POWER - GA.953192) and Horizon Europe (BIO-UPTAKE -GA. 101057049 and GENEX -GA. 101056822) frameworks, which are working on the development and optimisation of these "enduring prepregs" for different sectors.

AUTOMATED FIBER PLACEMENT OF THERMOPLASTIC MATERIALS: TOWARD A NEW WAY OF CONTROLLING TEMPERATURE HOMOGENEITY

DENIS CARTIE — Wed, 17 May 2023 11:45:03 +0200

Automated fiber placement (AFP) is a highly efficient process to produce thermoplastic matrix composite parts. This process involves heating, compaction and cooling steps that must be understood and controlled to achieve an optimal process for the manufacture of structural parts. Heating using a laser provides many advantages due to high energy density and efficient control that are beneficial for process control and productibility [1]. However, the temperature distribution during the layup can be altered by process parameters, i.e., laser power, layup speed and compaction force [2, 3]. The geometric configurations of the laser and the temperature measurement device (IR camera) also need to be considered to control the heat flux distribution at the tape/substrate interface (nip point region) and temperature homogeneity of the part. At the composite scale, the consolidation quality is determined by governing mechanisms such as intimate contact development between plies, void consolidation, and adhesion, which are a function of temperature, time and pressure distribution [4].

Graphite-chromium carbide composites with application in heat dissipation

Daniel Fernández-González — Wed, 17 May 2023 10:26:04 +0200

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.

rCF LM PAEK PRESS-MOULDING PROCESS OPTIMIZATION THROUGH THE INTRODUCTION OF A WAAM MOULD CORE

Alejandro Marques — Tue, 09 May 2023 11:53:02 +0200

Carbon fibre matrix composites are consolidated in high-demanding industries such as aeronautics and aerospace. Nowadays, thermoset composites are fully integrated on several new aircrafts in production. However, thermoplastic composites are progressively emerging as a better solution due to their end-of-life recyclability and optimized manufacturing process. One of the processes used to manufacture final parts from thermoplastic composite materials is press-moulding, in which a high-temperature heating system is combined with the application of pressure at high speeds. This article studies the optimization of press-moulding process in combination with an Additive Manufacturing (AM) produced metallic mould core. The aim of this study is the manufacturing of a thermoplastic aeronautical part, that would be submitted to real-world performance test. For the press-moulding process, a high-temperature infrared heating system was designed, supported by thermal oil mould heating, this heating system was combined with a mould-pressing process by integrating the system in a commercial injection machine. Regarding the AM tooling, produced by Wire Arc Additive Manufacturing (WAAM) process, was designed to reduce tooling weight, and optimise thermal cycle. Moreover, manufacturing data from WAAM tooling was recorded and compared with that obtained from a symmetrical conventional manufacturing made mould. The analysis shows savings in terms of material and energy consumption, as well as cycle times reduction. The final part metrology study shows indistinguishable results between the press-moulding process carried out using the WAAM tooling and that manufactured through conventional methods.

PANELES FABRICADOS MEDIANTE CURADO UV DE PREPREGS FUERA DE AUTOCLAVE REFORZADOS CON PERFILES DE PULTRUSION UV

Jon Aurrekoetxea — Tue, 21 Jun 2022 10:12:18 +0200

This paper has demonstrated the potential of UV curing technology when applied to glass fibre reinforced composites. Two manufacturing routes for making panels have been compared: manufacturing each element by its side and their subsequent bonding, and the direct integration of the profiles in the UV curing of the skins. The results of interlaminar tests show that the strength of the prepreg/profile bond is comparable to that of the prepreg/prepreg bond. Consequently, the prototypes obtained with both strategies show similar mechanical performance, both in stiffness and flexural strength. Finally, the low-temperature UV curing of the skin allows the use of water-soluble cores manufactured by 3D printing, which facilitates lamination and compaction operations.

Active and biodegradable food packaging based on PLA reinforced with inorganic particles encapsulating essential rosemary oil

Octavio Fenollar Gimeno — Sat, 30 Apr 2022 15:08:03 +0200

Poly(lactic acid) (PLA) is the most widely used bio-based and biodegradable polymer in the food packaging sector, due to its market availability, competitive cost and ease of processing. However, PLA has some limitations in terms of its mechanical, thermal and barrier properties, which can be improved by adding inorganic particles to the polymer matrix to obtain hybrid organic-inorganic composites with improved properties. Among all the inorganic particles, Halloysite Nanotubes (HTH) and Diatomaceous Earth (DT) are of special interest because their hollow structure offers the possibility of incorporating active agents inside them to be released in a sustained way to the food, extending their shelf life. In the present work, rosemary (Rosmarinus Officinalis) essential oil was encapsulated in the cavities of NTH and TD, the active particles were incorporated into a PLA polymeric matrix and processed by extrusion followed by cast-film process to simulate industrial conditions. The presence of NTH and TD improved the Young's modulus of PLA, while rosemary oil acted plasticising the system increasing the elongation at break allowing flexible films to be obtained. The obtained materials showed antioxidant capacity, demonstrating the potential to produce biodegradable active materials of interest in the food packaging sector.

test formulas

Test — Mon, 14 Jan 2019 10:46:03 +0100

Practical size structural optimization problems can involve a large number of variables and constraints that meet regulatory requirements for safety and structural performance. Most optimization problems tend to find the minimum value of the objective function within a feasible set that satisfies the constraints. Among evolutionary computation techniques, genetic algorithms (GAs) have been successfully used for the optimization of structures, including lattice systems. This article proposes an automated interactive methodology for the optimization of structures based on the integration of two commercial programs: Ansys and Matlab. The developed script uses the Finite Element Method for the analysis of the structure, together with the Genetic Algorithms for the optimization. The objective of the article is to evaluate the applicability, precision and efficiency of the proposed methodology. Two numerical examples of trusses were solved with the proposed methodology, classic truss of the literature and truss with normative restrictions. The results show that the methodology is adequate for the solution of size structural optimization problems with a good precision of the results.