Fracture toughness and fatigue life of MWCNT/epoxy composites

The present work experimentally characterizes the mode-I fracture toughness and stress-life curve of multi-walled carbon nanotube-(MWCNT-)reinforced epoxy-matrix composites. The effects of carbon nanotube weight fraction and voids on the composite fracture toughness are studied. The average fracture toughness of 1 wt%- and 3 wt%-MWCNT/epoxy composites is 1.29 and 1.62 times of that of pure epoxy, respectively. The 0.5 wt%-MWCNT/epoxy composites' fatigue lives are 10.5 and 9.3 times of the average fatigue life of neat epoxy, when they are subjected to cyclic loadings with stress amplitudes of 8.67 MPa and 11.56 MPa, respectively. The micrographs indicate that the separation and uniform distribution of MWCNTs in the matrix and the formation of voids significantly affect the fracture and fatigue behavior of MWCNT-reinforced composites.