抄録
Off-axis compressive deformation behavior of a unidirectional CFRP laminate at high temperature and its strain-rate dependence in a quasi-static range are examined for various fiber orientations. By comparing the off-axis tensile and compressive behaviors at an equal loading rate, the effect of loading direction on the flow stress level, nonlinearity and rate-dependence of off-axis deformation is elucidated. The experimental results show that the compressive flow stresses for relatively larger off-axis angles 30, 45, 90° have about 50 percent larger values than in tension for the same fiber orientations, respectively. The off-axis flow stresses in tension and compression significantly depend on the rate of loading, while they exhibit similar features in fiber orientation dependence and tension-compression asymmetry of off-axis nonlinear behavior regardless of the rate of loading. Then, formulation of a phenomenological viscoplasticity model that can describe the nonlinear rate-dependent behavior as well as its tension-compression asymmetry of unidirectional composites under off-axis loading in a unified manner is attempted. It is demonstrated that the proposed viscoplasticity model succeeds in adequately predicting the fiber orientation dependence of off-axis non-linear behavior, deformation asymmetry in off-axis tension and compression, and the strain rate dependence.
