Evaluation of back stress in inelastic deformation of polymer matrix composite
Ishii Takeyuki; Mizobe Takuya; Mizuno Mamoru; Murakami Sumio
Abstract:In order to formulate an inelastic constitutive equation of polymer matrix composites, back stress in the kinematic hardening creep theory of Malinin and Khadjinsky extended to anisotropic materials is evaluated experimentally under various loading conditions. After brief discussion to evaluate the back stress from experimental results, we perform several tests for tubular specimens under various loading conditions ranging from monotonic loading with step-up change in stress rate to reversal loading in axial and torsional modes. Then the evolution of back stress with respect to the change of viscous strain is calculated for these tests. The stress-strain relations together with back stress-viscous strain relations are simulated also by using Armstrong-Frederick model of kinematic hardening. By comparing the results of Armstrong-Frederick model with those of the corresponding experiments, we discuss characteristics of the evolution of back stress in polymer matrix composites and further elaboration of kinematic hardening rule for the composites. Key Words:Back stress, Polymer matrix composites, Inelastic constitutive equation, CFRP, Kinematic hardening, Reversal of stress direction, relaxation of strain hardening