Experimental and micromechanical modeling of fracture toughness: MWCNT

In this study, polypropylene-based nano and hybrid composites are prepared with 20 wt% glass fiber and multiwalled carbon nanotubes (MWCNTs) ranging up to 5 wt%. The multiaxial stress fields developed during external loading of composites cause crack propagation by various fracture mechanisms. Among the nanocomposites, it is observed that the critical stress intensity factor (KI) is highest for the one prepared at 3 wt% loading of MWCNTs. The synergistic effect of multiscale fillers in hybrid composite with MWCNT content of 3 wt% results in superior fracture toughness properties as evidenced by 16.6% increase in KI with respect to neat PP. Analytical expressions that take into account the fracture mechanisms like particle debonding and matrix yielding are employed to estimate the composite crack resistance and then compared with experimentally obtained fracture toughness properties. The fracture toughness properties are found to be dependent on composition of fillers, matrix yield strain, and debonding strain of the composites