Mechanical Response of Stitched T300 Mat/Urethane 420 IMR Composite Laminates: Property/Orientation Dependence and Damage Evolution

This report presents experimental and analytical results of investigations on the mechanical response of stitched T300 mat/urethane 420 IMR composite laminates with three different lay-up configurations. Tensile tests and short-term creep and recovery tests were conducted on the laminate coupons at various orientations. The X-ray photographic technique was adopted to detect the internal damage due to external loading history. The tensile data of laminates with antisymmetric and symmetric lay-ups indicated that lay- up sequences of cross-ply laminates do not have much influence on their tensile properties. However, misalignments within the stitch-bonded plies disturb the symmetry of intended quasi-isotropic laminates and thereby cause the mechanical properties to exhibit a certain amount of angular dependence. Classic lamination theory was found to be able to provide a very good prediction of tensile properties for the stitched laminates within linear range. Creep and recovery response of laminate coupons is greatly dependent on loading angles and load levels. The internal damage of laminate coupons is also directly related to loading angles and load levels as well as loading history