Polypropylene (PP) has inherently poor interfacial adhesion with carbon fibers (CF), which limits its reinforcing effect when used as a matrix material. To enhance the chemical interaction between the fiber and matrix, maleic anhydride-modified polypropylene (MAPP) is commonly added. The addition of MAPP promotes chemical bonding at the interface through polar functional groups, improving interfacial adhesion to some extent. On the other hand, methods that enhance physical bonding (anchoring effects) and physical constraint (tightening force) at the fiber-matrix interface have been developed, including the growth of carbon nanotubes (CNT) on the surface of carbon fibers. In this study, in order to clarify the effects of carbon nanotube-grafted carbon fibers (CNT-grafted carbon fiber) and maleic-anhydride modification on interfacial shear strength and flexural strength, we evaluated the interfacial shear strength and flexural strength of CF/PP composites. The interfacial shear strength between CNT- grafted carbon fibers and PP exhibited higher values compared to that between virgin carbon fibers and MAPP-added PP. However, regarding the flexural strength of laminated composites, those using virgin carbon fibers and MAPP-added PP showed higher values than those using CNT-grafted carbon fibers and PP. This result suggests that chemical bonding at the fiber-matrix interface is particularly important for resisting normal stresses generated under bending deformation, highlighting the different contributions of chemical and physical interfacial interactions.
TANAKA et al. (Thu,) studied this question.