Some improvements on Sun-Chen's one-parameter plasticity model for fibrous composites - Part I: Constitutive modelling for tension-compression asymmetry response

摘要

Herein, a one-parameter plasticity model proposed by Sun and Chen [Sun CT and Chen JL. A simple flow rule for characterizing nonlinear behavior of fiber composites. J Compos Mater 1989; 23: 1009-1020] demonstrates features that make it highly attractive for characterizing non-linear responses of fibrous composites. However, a detailed exploitation of the model's potential has been halted by unresolved problems that include tension-compression asymmetry in stress-strain curves, FEM implementation as well as optimal parameters determination, which are addressed in this investigation as well as proposed solutions are presented. The major focus in Part I of this three-part study was devoted to developing a simple model for predicting the tension-compression asymmetry in stress-strain curves for fibrous composites, which was based on Sun and Chen's one-parameter plasticity model. A generalized Hill yield criterion was proposed from combinations of the Drucker-Prager yield criterion that considers the effect of hydrostatic pressure for isotropic materials and the Hill yield criterion suitable for anisotropic materials. By incorporating the yield strength-differential effect on the plastic flow rule in composite laminates, the one-parameter plasticity model was extended to a strength-differential effect-incorporated model. The improved model has been calibrated and validated by off-axis tension and compression tests on unidirectional carbon/epoxy (IM600/Q133) composite laminates. Results verified that the proposed model captured the complex tension-compression asymmetry in observed non-linear responses of stress-strain curves.