Characterisation of off-axis tensile behaviour and mesoscale deformation of woven carbon-fibre/PEEK using digital image correlation and X-ray computed tomography

The architectural intricacy of multi-ply woven composites, caused by differences in layer alignment, introduces complexity into their mesoscale response to on- and off-axis tensile loading. To better understand the relationship between architecture and deformation response, this work combines digital image correlation (DIC) and 3D micro-computed tomography (μCT) to examine deformation for 0°, 15°, 30° and 45° specimens. Tensile tests were conducted with a four-layer plain woven carbon/polyetheretherketone (C/PEEK) laminate. In addition to the evident variance of mechanical properties between orientations, significant mesoscale differences in topography and strain were observed resulting from the layer alignment of individual specimens. Alignment of the top two surface layers induced distinct topographical peaks under extension, whereas nested architectures formed continuous topographical ridges. Matching observed surface strains around microstructural cracks identified in μCT images revealed both inter-tow and intra-tow shearing during off-axis extension and corresponding fibre reorientation, which effectively illustrates the potential benefits from combining DIC and μCT.