Influences Of Vacuum Thermal Cycling And Hydrotherm On T700/5429 Composites

T700/5429 composites was processed under vacuum thermal cycling at the continuously changing interval of -120~100℃. The changes of mass loss rate and mechanical properties were used to characterize the thermal aging of T700/5429 composites. ANSYS was employed to analyze the change of thermal stress distributing in T700/5429 composites at the same temperature as that of thermal cycles. Experiments on the moisture absorption rate and mechanical properties of hydrothermal aging tests of T700/5429 composites were carryed out under 100℃/ 100%H and 80℃/ 90%H.The experimental results showed that the properties of the composites have changed after thermal cycles. The mass loss ratio of the composites firstly increased with the increasing thermal cycles and finally reached the maximum after certain cycles. With the increase of vacuum thermal cycles, the 90°tensile strength of the composites reduced and then incrased gradually after 50 thermal cycles, the trend of the strength went flat untill 180 cycles. The bend strength of the composites decreased at the initial stage of thermal cycles and then increased gradually, the final bend strength of the composites had no difference with the original ones. The interlaminar shear stength of the composites reduced at the initial stage and began to go up after 50 thermal cycles, then the strength growed to the maximum after 180 thermal cycles. The whole range of the change of strength was small.The results of ANSYS analyse indicated that the thermal stress of the matrix reduced gradually with the increase of thermal cycles, while the stress at the fiber-matrix interface firstly decreased and then increased and finally went flat after 25 thermal cycles. The maximum thermal stress was found to locate at the fiber-matrix interface. The main damage in the composites due to thermal cycling was attributed to fiber-matrix de-bonding.The hydrothermal aging result of T700/5429 composites under 100℃/100%H and 80℃/90%H showed that the moisture absorption rate increased with the increasing temperature and humidity. It took less time to reach the saturation moisture absorption rate. Under the condition of 100℃/100%H, the transvers tensile strength of the composites firstly increased, and then decreased with the growing absorption rate and still reduced after drying. The interlaminar shear strength of the composites reduced with the increasing absorption rate and decreased after drying. The variety of the bend strength of the composites was unremarkable. The transvers tensile strength and bend strength did not change a lot with the increasing absorption rate under the condition of 80℃/90%H and did’t change after drying. The interlaminar shear strength decreased with the growing absorption rate and regained after drying.