Investigation on fatigue behavior and damage mechanism of C/BMI composites under hygrothermal environment

Abstract In this paper, the fatigue behavior and damage mechanism of C/BMI composites in hygrothermal environment were studied. T700/HT280 composite and its matrix resin were subjected to the hygrothermal aging treatment of 80 °C/85% RH. Moisture absorption rate, FTIR, DMA, Static tensile properties and fatigue properties of materials were tested before and after hygrothermal aging, respectively. The results show that the moisture absorption rate of composite and resin is in accordance with the Fick's second law. The maximum moisture absorption rate of composite is about 1/3 of resin's. With the increase of the hygrothermal aging time, the tensile strength of the composite increases and then decreases. The stiffness degradation curves of the original specimens at 60% and 65% stress levels follow the “fast-slow-fast” trend which presents a complete three stages of stiffness degradation. The fatigue properties damage of the materials by the hygrothermal aging can be attributed to the interface debonding and delamination between the interface and the layer under the action of moisture absorption and hygrothermal stress. The stage III of the stiffness degradation curve and the area of the hysteresis energy curve can effectively characterize the environmental damage effects induced by the hygrothermal environment factors.