A Novel Test Method to Induce Bi-Axial Stress States in Thin-Ply Carbon Composites Under Combined Longitudinal Tension and Transverse Compression

A novel test configuration has been developed to induce combined stress-states of inplane longitudinal tension and transverse compression in unidirectional (UD) composite layers. Two different multi-directional laminates have been designed incorporating UD carbon/epoxy plies embedded in angle-ply blocks of the same material. The scissoring deformation of the angle-plies induces compression in the central UD layers when the composite is strained in the 0° fibre direction. The amount of transverse compressive stress is determined through an inverse identification method from the measured surface strains of the laminates. Despite the large in-plane transverse compressive strain generated, there is only about 9% drop in the failure strain of the laminates when compared to the baseline failure strain of the UD carbon/epoxy material.