Abstract
A short-term stress relaxation behavior of a unidirectional carbon fiber-rein forced composite (T800H/Epoxy) has been examined under off-axis loading condition at elevated temperature. Stress relaxation tests were performed at 100℃ on plain coupon specimens with various off-axis angles: θ=0, 10, 30, 45, and 90°. For each of these off-axis angles, the stress relaxation tests were carried out at three different strain levels. The stress relaxation phenomenon was clearly observed for all off-axis angles. Just after the total strain was kept constant, the stress rapidly relaxed with time in a short period. The stress relaxation rate tended to immediately vanish. Then, the off-axis stress relaxation behavior was simulated using a phenomenological viscoplastic constitutive model based on the overstress. This model favorably reproduced the off-axis relaxation behavior of this material system at 100℃.
