Stress Relaxation Behavior of Angle-Plied Carbon Fiber-Reinforced Composite Laminates at Elevated Temperature

Abstract

Short-term stress relaxation behavior of angle-plied T800H/Epoxy [±θ] has been studied at high temperature. Stress relaxation tests were performed at 100℃ using plain coupon specimens with various fiber orientation angles : θ=0,30,45,60,and 90°. For each fiber orientation angle, the stress relaxation tests were carried out at three different total strain levels. The stress relaxation phenomenon was clearly observed for all kinds of angle-plied laminate, including θ=0°. Just after the total strain was kept constant, the stress rapidly relaxed with time in a short period. Then, the relaxation rate of the composite stress apparently vanished. The extent of the transient stress relaxation was significantly dependent on the total strain kept constant and the fiber orientation angle. Normalized relaxation curves eventually fell on a single relationship.