Modelling mechanical properties of core-shell rubber-modified epoxies

Experiments have been carried out to quantify the effects of rubber content and strain rate on the elastic and plastic deformation behaviour of core-shell rubber-modified epoxies. Both the Young's modulus and the yield stress were found to be slightly dependent on strain rate, but very sensitive to the volume fraction of rubber particles. Finite element analyses have also been performed to determine the influences of rubber content on the bulk elasticity modulus and the yield stress. By comparing with experimental results, it is found that the Young's modulus of rubber-toughened epoxies can be accurately estimated using the Mori-Tanaka method, provided that the volume fraction of rubber particles is appropriately evaluated. A yield function is proposed to quantify the effects of hydrostatic stress on the plastic yielding behaviour of rubber-modified epoxies. Agreement with experimental results is good. Also, a viscoplastic model is developed to simulate the strain-rate-dependent stress-strain relations.