Effect of cross-link density on strain gradient plasticity in epoxy

The variation of specific strain gradient plasticity modulus in epoxy has been examined as a function of cross-link density in epoxy. Cross-link density is controlled by varying the hardener content in the epoxy and the moduli are determined from nanoindentation data. Nanoindentation revealed that hardness increased with decreased indent depth. Specific strain gradient plasticity moduli and the characteristic lengths were found to increase with cross-link density in the epoxy. Data analysis revealed that the characteristic length is inversely proportional to the square root of the kink density. Consequently, material that has a higher cross-link density will have a higher specific strain gradient modulus and a lower kink density at yield.