Unidirectional spread‐tow carbon fiber/polypropylene composites reinforced with mechanically aligned multi‐walled carbon nanotubes and exfoliated graphite nanoplatelets

We investigated efficient methods to maximize the mechanical properties of carbon fiber/polypropylene (PP) composites by combining unidirectional spread‐tow carbon fibers (USCFs) and mechanically stretched PP films reinforced with aligned carbon nanomaterials (CNMs), such as multi‐walled carbon nanotubes (MWCNTs) and exfoliated graphite nanoplatelets (xGnPs). CNM/PP composite films were fabricated using film extrusion process, which resulted in tension‐induced orientation of CNMs. The influences of CNMs and their orientations in the films, the speed of the drawing rollers (take‐up speed), and the degree of crystallinity on the mechanical properties of nanocomposites were investigated. Multiscale hybrid composites (MHCs) consisting of USCFs and PP films reinforced with MWCNTs and xGnPs were manufactured by hot pressing. As compared with neat USCF/PP composites, USCF/PP composites containing 1 wt% aligned CNMs showed up to 18.3 and 77.3% increases in tensile modulus and strength, respectively, and 68.4 and 36.1% increases in flexural modulus and strength, respectively. In parallel, modeling and simulation of CNM/PP composite films and CNM/USCF/PP composites were performed to predict the tensile properties, taking into account the effects of CNM orientation. The mechanical properties of both nanocomposite films and MHCs were most dominantly affected by the degree of polymer crystallinity and CNM orientation. POLYM. COMPOS., 39:E1251–E1261, 2018. © 2018 Society of Plastics Engineers