Effects of ozonized carbon black on fracture and post-cracking toughness of carbon fiber-reinforced epoxy composites

Improving the fracture and post-cracking toughness of carbon fiber-reinforced composites based on thermosetting epoxy matrices are of significant interest in a wide range of applications. Herein, we report the synergistic integration of multi-scale composites by combining nano-scale filler and macro-scale fiber reinforcement inspired by the hierarchy approach. For the nano-scale filler, the carbon black (CB) surface was successfully modified using ozone treatment and thereby achieved highly efficient dispersion and interfacial properties. The reinforcing mechanisms were also analyzed, and the improvements on dispersion and interfacial properties should mainly be attributed to mechanical interlocking effect. For all of the multi-scale composites fabricated, the ozone-functionalized CB content was found to be optimal at 5 wt%, which improved the fracture and post-cracking toughness by 12.5% and 61.9%, respectively, compared with pristine CB.