Damage evolution in nanoclay-reinforced polymers: A three-dimensional computational study

Initiation and growth of microcracks in the nanoclay reinforced polymer composites were analyzed in numerical experiments using 3D micromechanical unit cell models. An original program code for the automatic generation of FE unit cells with multiple disk-shaped nanoplatelets, with high aspect ratio, clustered or exfoliated, randomly arranged or inclined, was developed. A four phase model of nanocomposites which includes the effective interface between the nanoplatelets and polymer, as well as interplatelet and outer phases, was used in the simulations. Different crack growth criteria were compared, including the 3D Benzeggagh and Kenane law (BK law) criterion, the 3D Wu and Reuter law (power law) criterion and the Reeder law criterion. The effects of the platelelet aspect ratio, clustering and orientation effects on the crack propagation are studied in numerical experiments. It was observed that the increasing aspect ratio leads to the increasing Young modulus, but decreasing strength. The clustering of disks had an adverse effect, meaning increased strength and lower stiffness. In the simulations, damage mechanisms such as crack deflection and delamination were observed.