A constrained optimization scheme is used to determine the stacking sequence that maximizes the extension-twist coupling in a composite laminate while maintaining its hygrothermal stability. The results are compared with the hygrothermally stable laminates obtained by stacking a set of rotated [0/90] plies. It is found that the laminate configurations resulting from the optimization scheme have improved coupling. Their coupling magnitude, however, is very sensitive to changes in fiber angle.
Eight sets of laminates with varying extension-twist coupling were fabricated and tested using a custom loading transducer designed to allow the laminate end to twist while undergoing extension. Test results were compared with analytical predictions.