Synchrotron X-ray diffraction and digital volume correlation of carbon fibre-reinforced polymers for enhanced characterisation of deformation behaviour

This paper demonstrates a new approach that exploits both lattice strain mapping via Wide Angle X-ray Scattering (WAXS) and Digital Volume Correlation (DVC) of Computed Tomography (CT) to understand the material response at different length scales in Carbon Fibre Reinforced Polymers (CFRPs) under in-situ loading, a phenomenon of substantial importance for the modelling, design, and certification of composite structures. WAXS gives insight into fibre lattice strain, while DVC provides sub-laminate response in the CFRP. A detailed numerical simulation was also developed to compare with these novel experimental methods. This approach is the first demonstration that the strain within the crystalline regions of the fibre is distinct from the sub-laminate behaviour, with up to 80 % and 36 % differences in the longitudinal and transverse directions, respectively, as a result of the complex microstructure of the fibres. An improved understanding of composite behaviour is fundamental to understanding how strain accommodation leads to structural failure, providing routes to refine part rejection criteria and reduce the environmental impact of this increasingly widespread material class.