Strengthening and Toughening Epoxy Composites by Constructing MOF/CF Multi-Scale Reinforcement

The interfacial designing of carbon fiber (CF)/epoxy composites, as a well-accepted method used to obtain high-performance composites, has gained extensive attention. However, an improvement in interfacial adhesion is usually accompanied by a simultaneous decrease in toughness, which has become an obstacle to the performance enhancement of CF/epoxy composites. Herein, nanosized UiO-66-NH2 was proposed to yield on the CF surface through an in situ growth method for preparing high-performance CF/epoxy composites. The induced UiO-66-NH2 could significantly enhance the active groups, surface roughness and wettability on the fiber surface, which can be confirmed by XPS, FTIR, dynamic contact angle (DCA) and SEM. Moreover, the porous structure of UiO-66-NH2 enables the epoxy resin to pass through it, which could toughen the matrix by forming an interpenetrating network structure and reducing the density of resin crosslinking. Meanwhile, the size effect of UiO-66-NH2 could hinder the crack propagation and release the stress concentration. Benefiting from these interfacial strengthening and toughening effects, the interlaminar shear strength and impact strength increased by 44.2% and 27.6%, respectively, in comparison to those of untreated CF. This work proposes a simple and effective strategy for interfacial designing that could offer new ideas for solving the conflict between the strengthening and toughening and provide a practical basis for preparing high-performance resin matrix composites.