Interlaminar Fracture Toughness of Carbon-Fiber-Reinforced Epoxy Composites Toughened by Poly(phenylene oxide) Particles

In this study, carbon-fiber-reinforced epoxy composites were interleaved by poly(phenylene oxide) (PPO) particles to improve their delamination resistance. The morphology of PPO particles at the interlayer was visually observed by a fluorescence microscope. The effects of the PPO particle size and loading level on Mode I and Mode II interlaminar fracture toughness of the interleaved laminates were investigated by standard double cantilever beam (DCB) and end-notched flexure (ENF) tests. The results indicated that the toughening efficiency of PPO was inversely proportional to the particle size. Notably, the laminate interleaved by 10 wt % small-sized PPO particles (10–50 μm) exhibited 65% and 40% enhancements of Mode I and Mode II interlaminar fracture toughness, respectively. The observations of fracture surfaces showed evidence of the toughening mechanisms induced by PPO particles, including plastic deformation of the matrix resin, crack bridging, crack deflection, crack pinning, and resin hackles.