Interface modification of carbon fiber composites by interlocked brushite nanopins and brushite nanosheets

The interface region of carbon fiber/epoxy composites (CE) plays an essential role in mechanical and biotribological properties for bone replacement application. However, the debonding interface of fiber/matrix in CE presents a significant obstacle to their practical deployment. In this study, two component brushites with interlocked structure reinforcement have been designed and synthesized into CE for synchronously upgrading the tensile strength and biotribological property. Especially, brushite nanopins (BSp) are radially grafted on the surface of carbon fibers in order to optimize the interface between carbon fiber and epoxy matrix via forming intertwined filamentous architectures. In addition, brushite nanosheets (BSs) are vertical growth on the surface of BSp in order to promote the penetration of the epoxy and improve the cohesion of epoxy matrix. Thus, the mechanical and biotribological properties of BSp and BSs (BSps) modified CE (BSps-CE) have been markedly enhanced. In contrast with CE, the tensile strength of BSps-CE (97.22 MPa) is increased by 27%, and the elastic modulus is increased by 54%. The wear rate of BSps-CE (0.283×10⁻¹⁵ m³(N·m)⁻¹) is greatly reduced by 169% compared with CE (0.763×10⁻¹⁵ m³(N·m)⁻¹). The boost of mechanical strength and the reduce of wear rate means that the service life of the BSps-CE as an artificial implant in human body is prolonged, and the wear debris is reduced. This work demonstrates that it is feasible for BSps to improve the mechanical and biotribological properties of CE by interfacial modification. Superior mechanical and biotribological performances of BSps-CE show its potential for orthopedic implant and fracture internal fixing applications.