Stress Relaxation Behavior of Symmetric Angle-ply Laminates of CFRP at High Temperature and Numerical Simulation

Abstract

Stress relaxation behavior of symmetric angle-ply laminates of T800H/3631 at large strain and high temperature has been examined. Stress relaxation tests are performed at 100°C on plain coupon specimens of three types of angle-ply laminates: [±30]s, [±45]s, [±60]s. For each ply orientation, the stress relaxation tests are carried out at three different tensile strain levels. Stress relaxation phenomenon clearly appears in all kinds of angle-ply laminate. Just after the total strain is kept constant, the stress rapidly relaxes with time in a short period. The stress relaxation rate of the angle-ply laminates tends to almost vanish. Simulation of the stress relaxation behavior of the angle-ply laminates is performed using the classic laminated plate theory with a phenomenological viscoplasticity model for elementary plies. Good agreements between the predicted and observed results on the angle-ply laminates are obtained by taking account of the local strain recovery measured with strain gauges. It is also demonstrated that the stress relaxation response is consistent with the creep response of the same material system.