Experimental and numerical research on the nonlinear creep response of polymeric composites under humid environments

Abstract The aim of this work is to study the nonlinear creep response of polymeric composites under humid environments. A three-dimensional orthotropic nonlinear creep constitutive model that considers the moisture effect is derived by introducing the moisture shift factor into Schapery’s nonlinear equation. Hygrothermal-mechanical coupling moisture absorption tests, as well as static mechanical property tests and short-term tensile creep-recovery tests with different moisture contents were performed to obtain the hygroscopic parameters and the moisture and stress dependent nonlinear creep parameters. A fully coupled numerical prediction model was developed in Abaqus with a user-defined material subroutine (UMAT) and user-defined field variable subroutine (USDFLD) to simulate the coupled diffusion-nonlinear creep behaviour. Good agreement was observed between the numerical and experimental results.