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 research work is focused on developing thermoplastic composites by automated tape laying process (ATL) having acceptable gas permeability levels to store hydrogen H2 in linerless composite material tanks at cryogenic temperatures. Carbon fibre (CF) with polyamide 11 (PA11) matrix was used to manufacture composites using automated tape laying process. The manufactured composites treated in autoclave and tested for hydrogen permeability at room temperature. The results show that autoclave cured CF/PA11 composites meet the set permeability requirements for composite hydrogen storage vessel designed for pressure of 6 bar. 

Abstract

This paper focuses on the impact of processing parameters on the joint quality of carbon fiber-reinforced thermoplastic (CFRTP) materials in a continuous ultrasonic consolidation process, with the purpose of optimizing the performance of this process. Parameters such as joining speed and ultrasonic amplitude are examined through porosity and shear strength. Optical microscopy was employed to analyse the interface morphology, and the shear strength of the joints was measured. The results showed that a joining speed of 1 mm/s resulted in the highest shear strength. Additionally, samples with less than 2% porosity were achieved, indicating that this process can produce high-quality joints with respect to porosity and mechanical properties.

Abstract

The increase in both competitiveness and new environmental regulations has created a need within the transport sector to develop new high value-added and differentiated products in an efficient and sustainable manner. In this context, there is a growing need to develop new multi-material components, understood as dissimilar joints between lightweight metals and thermoplastic composite materials, especially for use in high-stress areas of the component. The use of Fibre-Metal Laminates (FMLs) offers, in addition to improved strength compared to lightweight metal alloys such as aluminum, enhanced resistance to mechanical fatigue and impact when compared to monolithic composite materials, combining the properties of both materials. The development of this type of laminate (FML) has traditionally focused on thermoset composites, which have a limited lifespan due to their inability to be reprocessed, as well as longer manufacturing times. For this reason, the COMIC project has studied different manufacturing methodologies for FMLs with a thermoplastic matrix, achieving lightweight and sustainable components simultaneously. This work presents a study of various surface treatments aimed at increasing the surface energy of the metal, which promotes physical and chemical anchoring between the metal and the composite. Additionally, different FML manufacturing methodologies have been explored, incorporating the various surface treatments. Finally, the optimal parameters and treatments have been selected for the production of FML laminates (PA6-aluminum composite) that maximize interlaminar strength and mechanical performance, with a comparison made against monolithic composite materials.

Abstract

The demand for lightweight and high-strength materials across various industries has driven research into hybrid structures that combine the mechanical advantages of metals with the low weight and strength of carbon fiber-reinforced composites. The use of thermoplastic composites additionally enables disassembly and reuse at the end of the service life. Furthermore, the metal-composite joining process and the thermoplastic CFRP processing could potentially be achieved in a single step, resulting in reduced manufacturing cycle times and overall higher productivity. However, several challenges must be addressed, such as differences in the coefficients of thermal expansion, the influence of the composite processing parameters on the metallic material and its surface treatment, and the potential formation of galvanic couples. This study investigates different manufacturing methods for dissimilar or multi-material joints: automated fiber placement (AFP) and thermoforming. A comparison is presented based on the manufacturing parameters, which were adjusted to maximize joint strength for each process.A cross-sectional optical microscopy analysis was carried out to evaluate the joint interface and the interaction between the surface treatment and the thermoplastic resin matrix layer, which is responsible for the adhesive bond between both components. In addition, mechanical testing was conducted to assess the influence of processing parameters, establishing a joint design route for optimized performance evaluation. The conclusions demonstrate that the polymer layer at the interface plays a key role in compensating for differences in thermal expansion coefficients, leading to enhanced mechanical performance of the joint. The advantages and limitations of each manufacturing method are discussed in this work.

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.