Competition between rate-dependency of bulk laminates and interlaminar interface on the responses of thermoplastic composites

Thermoplastic composites can be an alternative solution for automotive light-weighting and hence, the reduction of carbon emissions. Double cantilever beam (DCB) test is one of the primary standards tests used to evaluate the Mode I interlaminar fracture toughness of composite laminates. DCB tests at various pulling rates are usually performed to get information about the rate-dependent fracture toughness of a given composite. Usually, the observed rate-dependent response has attributed solely due to the influence of the interlaminar interface although the bulk-ply in laminate itself is rate-dependent. In this paper, we use a viscoelastic viscoplastic ply damage model and viscoelastic cohesive element model to study the response of DCB test at various pulling rates. The objective is to break down the contribution of each constituent (bulk-ply and interlaminar interface) by turning on and off the rate-dependent model in the ply and the interface. Hence, we can isolate the contribution of each constituent to the increase of apparent load-displacement curves.