Characterization and modeling of the creep behavior of fiber composites with tension and compression asymmetry

This paper seeks to present an integrated experimental-theoretical-numerical approach to accurately model the asymmetric tension/compression creep behavior of IM600/Q133 composites. The nonlinear deformation behavior of composites depends on loading time, loading mode, and fiber orientation, and does not satisfy the Boltzmann superposition principle. Therefore, an elastic-viscoplastic constitutive model was developed to characterize this behavior based on an improved one-parameter plasticity model. In addition, the plastic potential function was extended to describe the plastic flow and time-dependent behavior of unidirectional fiber composites with tensile and compressive asymmetry. The proposed model was implemented using the finite element analysis (FEA) in the ABAQUS software via a user-defined subroutine (user material or UMAT). The model was validated against experimental creep curves for unidirectional and angle-ply laminates under off-axis tensile and compressive loading. Finally, the results were discussed to illustrate the applicability of the proposed method.