THE EFFECTS OF ENVIRONMENTAL HUMIDITY AFTER POST CURE ON THE OPTIMAL TEMPERATURE PATH OF POLYMER COMPOSITES

Previous studies on the optimal cool-down path of a composite laminate , were applied in this paper to a new element-humidity used for analys is of the residual stresses which develop in a composite material lami nate after termination of cool down due to further exposure to a humid environment. Computations were performed for AS4/3502 symmetric balan ced cross-ply laminate. The viscoelastic behaviour and the constant ex pansion coefficients of temperature and moisture of hygrothermorheolog ically simple material have been considered and an optimal temperature path was obtained with the assistance of variations for yielding the minimal value for the average residual stress within the laminate. Fur thermore, the experiment for measuring the residual stress by strain g auge is conducted in order to ensure the reliability of the theoretica l analysis. The result of this paper gives further understanding of th e humidity effect on composite material during its post cure process. Therefore, this study will be very helpful for the improvement of manu facturing industries.