The interface debonding in particle-reinforced nonlinear viscoelastic polymer composites

To conveniently and feasibly characterize the interface debonding in particle-reinforced nonlinear viscoelastic polymer composites (PRNVPCs), a micromechanical model is proposed based on a normalization method that can convert the rate-dependent constitutive relationship of a nonlinear viscoelastic matrix into a rate-independent linear viscoelastic constitutive relationship. With this treatment, a linear homogenization scheme is used to achieve closed-form solutions for the critical particle stress and the critical time at the initiation of interface debonding in PRNVPCs. The change in the particle debonding stress versus the debonding angle is theoretically predicted with the new model, and the predicted change is qualitatively consistent with the experimental data. Furthermore, it is found that the particle debonding stress increases monotonically with decreasing particle size. The increase of the applied strain rate leads to an increase of the particle debonding stress but a decrease in the critical debonding time. This demonstrates that a smaller particle and a higher loading rate are both beneficial for improving the interfacial adhesion, while the latter will shorten the time needed to initiate interface debonding. The present research provides a convenient approach to theoretically characterize the interface debonding in PRNVPCs, which should be of guiding value for the design of advanced polymeric composites with a good load bearing capacity.