Natural Fibers for Automotive Nonwoven Composites

Two types of nonwoven composites, uniform and sandwich structures, are produced using bagasse, kenaf, ramie, and polypropylene (PP) fibers. The experimental uniform composites include kenaf/PP (70/30), bagasse/PP (50/50), and ramie/PP (70/30). The experimental sandwich composites include kenaf/bagasse/kenaf and ramie/kenaf/ramie. A comparative study of these experimental composites is conducted in terms of mechanical properties, thermal properties, and wet properties. Composite tensile and flexural properties are measured using a desktop tensile tester. Composite thermal properties are characterized using dynamic mechanical analysis (DMA). Water absorption and thickness swelling of the composites are evaluated in accordance with an ASTM method. Scanning electron microscopy is used to examine the composite bonding structures. Statistical method of ANOVA is used for the comparative analysis. The study finds that the uniform structures have higher tensile strength and modulus, as well as higher flexural yielding stress and modulus than the sandwich structures. In terms of the wet properties, the uniform composites have less water absorption but higher swelling rate than the sandwich composites. The DMA results show that the uniform composites feature a higher softening temperature (140 C) and melting temperature (160 C), in contrast to the sandwich composites with the softening point 120 C and melting point 140 C. Within the uniform structure group or sandwich structure group, the composite thermal mechanical properties did not differentiate very much among the different natural fibers, indicating that the composite thermal mechanical strength was largely dependent upon the thermal property of the polypropylene bonding fiber.