Abstract

Due to the increasing demands in environment regulations related to gases emissions, the automotive sector has gradually increased the plastic consumption in vehicles.The objective is to introduce in the market structural components made in latest generation composite materials in a serial and competitive way with the functionality of the present metallic parts. In this work the redesign of two automotive metallic components that will be produced via thermoplastic RTM (Part II) is presented. This technology allows the manufacturing of high performance long fibre composite materials with shorter cycle times. Based on the specifications of the components and the actual metallic solutions performance a new concept of a brake pedal and a control arm consistent with the manufacturing via a RTM thermoplastic process is adressed. For the calculations of both components, carbon or glass fibre with poliamide matrix (APA6) based solutions are used.

Abstract

Continuous Fibre Reinforced Thermoplastic Composites (CFRTPCs) are becoming alternative materials to replace the conventional thermosetting polymers and metals due to excellent mechanical performance, recycling and potential used in lightweight structures. Fused deposition modelling (FDM) is a promising additive manufacturing technology and an alternative of conventional processes for the fabrication of CFRTPCs due to its ability to build functional parts having complex geometries. The mechanical properties of a built part depend on several process parameters. The aim of this study is to characterize the effect of build orientation, layer thickness and fibre volume content on the mechanical performance of 3D printed continuous fibre reinforced composites components manufactured by a desktop 3D printer. Tensile and three-point bending tests are carried out to determine the mechanical response of the printed specimens. SEM images of fractured surfaces are evaluated to determine the effects of process parameters on failure modes.

It is observed that the effect of layer thickness of nylon samples on the mechanical performance is marginally significant. In addition, continuous fibre reinforced samples show higher strength and stiffness values than unreinforced ones. The results show that carbon fibre reinforced composites exhibit the best mechanical performance with higher stiffness and flat samples exhibit higher values of strength and stiffness than on-edge samples. Additionally, the results show that strength and stiffness increase as fibre volume content increases in most cases but, conversely, the level of increment in mechanical performance is moderate with continued rise in fibre content, particularly in the case of Kevlar® and glass fibres, due to weak bonding between the fibre/nylon layers as well as the presence of increased levels of defects.

Abstract

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].

Abstract

Sisal fibers have taken special focus by material investigators and commercial environment because they are economical, biodegradable and lightweight(1). Composite manufactured using natural fibers can supply properties that can be compared to other composites reinforced with synthetic fibers, as previous studies have shown (2-6). Thus, fibers that come from nature sources, such as wood, nuts fruit, jute, kenaf, hemp, sisal, etc. are being introduced in composite manufacturing (7-9). Sisal fiber has relevant economical and ecological properties (10), but it is a lignocelulosycal fiber with hydrophylic character, so it is difficult its usage with hydrophobic matrix, and it is required to use coupling agents in order to improve its interface adhesion. This work starts with sisal fibers submitted to different types of primary treatments, and for each one of these treatments, sisal fibers are submitted to secondary treatments of maleinization, mercerization, silanization, formation of nascent surface isocyanates, carboxylation and methacrylate treatment. The efficiency of these treatments has been evaluated using morphology characterization techniques by FTIR-ATR, electronic microscopy (SEM). With some of the treated fibers, thermoplastic composites have been prepared and these have been used to prepare standard probes that have been thermally and mechanically tested, as well as other additional interesting physicochemical characteristics.