Strength of quasi-isotropic laminates under off-axis loading

An experimental investigation was carried out to determine the failure properties of quasi-isotropic AS4/3501-6 carbon/epoxy laminates under conditions where the loading axis did not coincide with the fiber axis. A tubular specimen subjected to combinations of pressure and axial tension was used to determine the response under various tension-tension biaxial stress states. The results showed no loss of strength with rotation of the laminate orientation with respect to the loading axes at angles including 22·5°,the maximum possible for the laminate used. Maximum fiber direction strains at failure were essentially independent of the rotation of the laminate as well as the biaxial stress state.