Automotive Parts and Infrastructures

Abstract

Abstract Although continuous fiber-reinforced composite materials have about 10 times higher specific strength than low (SAE 1010) to high (SAE 4340) carbon steels, as shown in tables 2.2 and 2.3, they are not widely used in automotive or infrastructure applications due to their high cost. They are slowly becoming employed in the loadbearing structures of automotive parts and infrastructures such as bridges, guard rails, and special buildings, as the cost of composite materials becomes lower and efficient mass production methods are developed. The principal advantages of fiberreinforced polymeric matrix composites for automotive parts are weight savings, part consolidation, and improvement in NVH (noise, vibration and harshness). The absence of corrosion problems, which lowers maintenance cost for automotive parts and infrastructures such as bridges and sewage pipes, has enabled the fiberreinforced polymeric composites to be employed in these areas, although gradually. The randomly oriented chopped E-glass-fiber-reinforced polymeric matrix composites, which are not load-bearing structural materials, are mainly used in the automotive industry due to their low cost. The polymers for the matrix are either thermoplastics, such as nylon, ABS, and polypropylene, or thermosets, such as unsaturated polyesters, vinylesters, and polyurethanes. Shorter processing time is an important consideration because automotive parts are produced at a rate of one part per minute, unlike parts in the aerospace industry. Therefore, the preferred processing methods for automotive composite parts are injection molding, compression molding, reaction injection molding (RIM), structural reaction injection molding (SRIM), pultrusion, and resin transfer molding (RTM). All these methods are fast and highly automated, which compensates for the higher cost of composite materials (Mallick, 1997). However, there have been several attempts and some successful applications of fiber-reinforced composite structural members to various parts of passenger cars, including load-bearing structural parts (Beardmore, 1986; Weeton et al., 1986). Especially, glass-fiber-reinforced polymer composites have been used for static and dynamic load-bearing structures such as bumpers and leaf springs, thanks to their high specific strength (strength/density) and impact energy absorption characteristics (Mallick and Broutman, 1977; Cheon et al., 1999; Lee et al., 2000; Lee and Cheon, 2001).