Preparation carbon nanotube-decorated carbon fibers under low pressure for epoxy-based unidirectional hierarchical composites with enhanced interlaminar shear strength

Multi-walled carbon nanotubes (CNTs) were grown in-situ on the surface of carbon fibers (CFs) at low pressure by a vertical chemical vapor deposition (CVD) reactor. The surface of CFs was modified by electrochemical anodization, and the growth morphology and other properties of CNTs were analyzed by detailed techniques. The CNT-grown CF reinforced unidirectional hierarchical composite material based on the epoxy resin was prepared. The interlaminar shear strength (ILSS) indicates that the maximum strength of the composites reaches 108 MPa after the CNTs are grown on the CF surface with a 25.2% increase than that of the desized CF composites. The fracture surface of composites was observed by scanning electron microscopy (SEM) to further understand the interfacial fracture behavior and enhancement mechanism of CNTs-CF/epoxy composites. The significant improvement in the overall performance of the hierarchical composites can be attributed to the increased adhesion of the interface between the fibers and the resin. The presence of CNTs can restrict the molecular movement of the resin and achieve a strong anchoring interaction, thereby increasing the strength and toughness of the composites and reducing the stress concentration between the layers.