Microscale intrinsic properties of hybrid unidirectional/woven composite laminates: Part I experimental tests

Understanding of the failure of composites is critical for evaluating their safety and reliability when they are in service. In this research, a combined image analysis technique using computed microtomography (micro-CT) and scanning electron microscopy (SEM) is proposed to study the microstructures, damage and failure of a hybrid unidirectional/woven composite laminate (HUWCL). Micro-CT is used to extract the 3D microscale morphology and identify the internal failure behaviours of the HUWCL. A series of material parameters, such as fiber volume fraction, void ratio and layer mode, are acquired by the statistical analysis of the micro-CT images. In addition, microscale surface damage and failure mechanism of woven and unidirectional (UD) laminae are further investigated by SEM. It is found that the matrix damage around the interface always occurs in both woven and unidirectional (UD) laminae, and distinct delamination is found between the UD laminae and the woven composites. The study shows a great potential of combining micro-CT with SEM in revealing the local damage and intrinsic failure mechanism in HUWCLs at microscale.