Micromechanics based FEM study on the mechanical properties and damage of epoxy reinforced with graphene based nanoplatelets

A numerical micromechanics study is performed to investigate the effect of using graphene nanoplatelets (Gnp) with theoretical maximum properties and reduced graphene oxide (rGOnp) on the mechanical properties and damage mechanism of graphene based nanocomposites. Here we consider brittle matrix cracking and interface debonding as the main damage mechanisms. The results showed that the competition between both mechanisms is affected by nanoplatelets/matrix modulus-mismatch, volume fraction, interface strength and orientation. Gnp showed improved modulus, however, with inferior strength and fracture strain compared to rGOnp. This is due to the large modulus-mismatch of Gnp, which resulted in increasing the stress concentration, matrix cracking and coalescing at lower loads. On the other side, the lower stress concentration of rGOnp allowed for higher load accumulation and increased interface debonding. Applying stronger interface properties was found to suppress the interface debonding, improving strength and fracture strain. Further, aligned nanoplatelets lead to a simultaneous improvement in modulus, strength and fracture strain. This is due to the improved load transfer and activation of toughening mechanisms observed for bioinspired nacre like structures.