Effect of the Carding Process and Reinforcement Method of Carbon Fiber/Polypropylene Fiber Nonwoven Fabrics on the Anisotropic Mechanical Properties of Hot-Pressed Composites

In this work, nonwoven fabrics made from carbon fibers (CFs) and polypropylene (PP) fibers were manufactured through a carding process and a cross-laying process and reinforced by either a needle punching method or a thermobonding method. The effects of the carding parameters (adding oil, increasing the gauge and decelerating the speed) and reinforcement method (needle punching method or thermobonding method) on the anisotropic mechanical properties of hot-pressed CF/PP composites were investigated. Additionally, the length, distribution and orientation of carbon fibers in the hot-pressed composites were studied. The carbon fibers were oriented by the carding method, and the composites exhibited anisotropic properties. Moreover, the fiber distribution results indicated that increasing the gauge and decelerating the speed had a slightly negative influence on the distribution of carbon fibers and that the cross-laying process led to a uniform distribution of fibers. Furthermore, adjusting the carding parameters and reinforcement method could reduce the damage sustained by carbon fibers during manufacturing and subsequently improve the mechanical properties of the CF/PP composites in the transverse direction (TD).