Abstract

The main objective of this work has been the manufacture , and subsequent flexural and fatigue  tests, of automotive real parts, made of thermoplastic composites. This has been achieved by incorporation continuous carbon fiber (textile) to polyamide matrix, through an specific process very similar to a thermoplastic  RTM. The fatigue behaviour of any composite is governed by the toughness of the material. Because of this and the low cost, the polyamide has been considered as a polymer matrix. The process involves an in-situ polymerization, that the low viscosity of the monomer,e-caprolactama (e-CL), allows the infiltration of preforms and textiles. The demonstration part has been completely redesigned by BATZ and TECNALIA to fullfill mechanical requirements and  manufacture ability. In particular, it has been fabricated a suspension subframe with an 52%vol. of a commercial carbon fiber and thickness variations from 3 to 8mm within the same part, obtaining a significant reduction in weight relative to the metal part (6,8 kg vs 3,48 kg) and the established mechanical requirements. As far as the fatigue/durability test are concerned, they have been performed to evaluate the strength of the composite and to increase the correlation between CAE analysis and the real behavior of the hybrid component. All the tested parts support 2.000.000 cycles (the stipulated for this part in metal) without break, only with small deformations in the bushings holes. As far as the flexural test are concerned, they evaluate the maximum quasi-static strength of the component. All the parts tested deform considerably, recovering much of this deformation once the load is removed.

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.

Abstract

The aim of the study was to define the composition and methodology for manufacturing laminated composites of polypropylene and continuous fiber reinforcement. These composites are designed with the aim of being integrated into high mechanical performance lightweight parts obtained by high production rate manufacturing processes such as compression molding or the overinjection. The complete cycle of production of the polypropylene textile laminate composites has been analyzed, going from the selection and additivation of raw materials, treatment of the reinforced fibers and fabrication and characterization of the composite laminates. The study has focused on composites based on polypropylene resins and twill 2/2 reinforcements of fiberglass fabric.

Abstract

This work is focused on two current and important issues. On one hand, 12 millions of tons of PET are thrown into the sea each year. In fact, in spite of being a recyclable polymer, less than 50 % of processed PET is recycled in Europe. On the other hand, thermoset matrix composites are widely used in the industry and the end-of-life products and scraps need to be recycled. Compared to thermoplastics, thermosets present a problem for being recycled or remolded due to their irreversible curing.

Many researches are focused on the recycling of carbon fiber reinforced epoxy, presenting three different paths: mechanical, thermal and chemical recycling. Thermal recycling is the most promising because it allows to recover clean fiber. However, it is an energetically expensive and non-environmentally friendly process. Chemical recycling, for its part, needs hazardous products, such as nitric acid, to dissolve the matrix. Finally, both, fibers and matrix, are recovered with mechanical recycling which consists on milling the composite to obtain finer parts.

In this work, unidirectional carbon fiber reinforced epoxy is blade-milled and it is used as reinforcement of a new composite. As matrix, PET coming from recycled bottles is used. First of all, pellets of PET are produced from the bottles with a blade mill. Recycled composite and PET are mixed and a sheet is manufactured with a hot plates press. The resulting material is chemically and mechanically tested.

Abstract

The transport industry is dominated by the challenge on lightening the weight due to environmental restrictions and cost reduction. The use of different materials and multi-material designs provide a great opportunity to develop products capable of meeting this challenge. Critical aspects to be considered in multi-material manufacturing are surface preparation and dissimilar joining. The multi-material joining metal-composite thermoplastic (CTP) is critical for different aspects such as low adhesion due to a low chemical affinity or corrosion problems in the case of the use of carbon fiber reinforced composites. On the other hand, laser texturing is one of the most promising techniques to create surfaces with controlled roughness, manufacturing in a single step and improving metal-CTP adhesion, without the need to use adhesives.

This work, developed within the framework of the European COMMUNION project (GA680567), addresses the optimization of the direct joining process between different high-performance metals and thermoplastic composite cintas. The study deals with surface preparation using laser texturing, the study of different joining strategies and the characterization of joints using different techniques and Single-Lap Shear tests.

Depending on the texture, type of materials or manufacturing strategy, the strength of the joint is improved by 50-200%, achieving structural strength values (> 10MPa) in the optimized joints.

Abstract

This work is focused on two current and important issues. On one hand, 12 millions of tons of PET are thrown into the sea each year. In fact, in spite of being a recyclable polymer, less than 50 % of processed PET is recycled in Europe. On the other hand, thermoset matrix composites are widely used in the industry and the end-of-life products and scraps need to be recycled. Compared to thermoplastics, thermosets present a problem for being recycled or remolded due to their irreversible curing.

Many researches are focused on the recycling of carbon fiber reinforced epoxy, presenting three different paths: mechanical, thermal and chemical recycling. Thermal recycling is the most promising because it allows to recover clean fiber. However, it is an energetically expensive and non-environmentally friendly process. Chemical recycling, for its part, needs hazardous products, such as nitric acid, to dissolve the matrix. Finally, both, fibers and matrix, are recovered with mechanical recycling which consists on milling the composite to obtain finer parts.

In this work, unidirectional carbon fiber reinforced epoxy is blade-milled and it is used as reinforcement of a new composite. As matrix, PET coming from recycled bottles is used. First of all, pellets of PET are produced from the bottles with a blade mill. Recycled composite and PET are mixed and a sheet is manufactured with a hot plates press. The resulting material is chemically and mechanically tested.

Abstract

The thermoplastic RTM process (T-RTM) is currently one of the most demanded process for R&D in the automotive sector. This sector tries to lighten the weight of the vehicle with highly resistant non-metallic components and with efficient manufacturing in cycle-time and cost. In the framework of the BIHARKONP project, EDERTEK-TECNALIA proposes the migration of a suspension arm, currently manufactured by means of metal stamping, to high mechanical requirements composite materials, obtaining a weight reduction of 30%. For the manufacture of this component it was proposed to redesign the component in carbon fiber (CF) and polyamide 6 matrix (APA6). The redesign (Part I) consisted in a mechanical calculation of the loads that the component had to support. The geometry has been changed with the aim of fulfilling the part specification and the peculiarities of the T-RTM process. For the manufacture of the component, a CF/APA6 composite laminate was defined and characterized and a specific CF for thermoplastics was selected. Subsequently, a T-RTM mold was designed and manufactured with inserts for fiber compaction and eight thermal control zones. The geometry of the control arm involves the manufacture of CF preforms by means of a thermal forming process with thermoplastic veils. Caprocast technology has been used to manufacture the prototype by caprolactam injection and its polymerization inside the heated mold. The prototype was subjected to bearing test, bushing insertion-extraction test and bushing strength test. The component was validated.

Abstract

El futuro del sector aeronáutico está orientado a fabricar estructuras y componentes más ligeros y rentables, empleando materiales y tecnologías más ecológicos que permitan reducir costes, peso y consumo de combustible con ciclos de fabricación más cortos, a la vez que se aumenta la eficiencia energética en la fabricación. En este contexto surge el proyecto AEROPLAS, con el objetivo de contribuir al proceso de fabricación avanzada de composites termoplásticos utilizando tecnologías de bajo coste para la industria aeronáutica. En el presente estudio se abarca la sustitución de piezas aeronáuticas fabricadas actualmente en composite termoestable por composite termoplástico, en dos componentes reales: panel de cubierta y puerta de acceso del carenado ventral del A350, empleando dos materiales de distinta calidad: un semipreg de LM-PAEK/CF (TenCate Cetex® TC1225) y un prepreg de PC/CF (ePreg245CHT/PC40). Mediante diseño y cálculo, se han obtenido los apilados y espesores de pieza necesarios para cubrir los requerimientos estructurales de ambos componentes, a partir de los datos obtenidos de la caracterización de los materiales de partida. Se han estudiado y comparado dos procesos de fabricación para la obtención de las nuevas piezas, seleccionando el termoformado y la estampación como los más prometedores. Por último, se ha llevado a cabo la caracterización de las piezas obtenidas mediante ensayos no destructivos (inspección visual, verificación por ultrasonidos, inspección dimensional mediante laser tracker) y destructivos (tracción en sentido plano [AITM1-0066], resistencia al aplastamiento [AITM1-0009], resistencia a tracción del laminado [AITM1-0007], resistencia a tracción de unión atornillada [AITM1-0067]).

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.