3D micro-mechanics of a CFRP laminate under high-rate and varying temperature loading using digital volume correlation

Understanding microscopic damage mechanics in laminated CFRP at high-strain-rate (HSR) loading and extreme temperatures remains an enduring challenge. Using X-ray tomography coupled with digital volume correlation (DVC), three-dimensional local displacement/strain fields and segmented micron-scale intra-ply cracking were quantified, revealing damage micro-mechanics at HSR. Local deformation exhibits strong directionality that intensifies with increasing strain and decreasing temperature, accompanied by earlier and more rapid damage development at low temperature. Strain–damage correspondence indicates both Mode-II–dominated and mixed-mode (I/II) intra-ply cracking, while delamination shows a stronger Mode-I contribution but remains mixed-mode. Inter-ply kinematic constraint and shear transfer between adjacent plies with mismatched fibre orientations were directly visualised and characterised under HSR loading, particularly at low temperature. Together with the spatially non-uniform and asynchronous development of local deformation through the laminate thickness, these results highlight substantial departures from the nominal in-plane shear state commonly assumed for uniaxial ± 45 ° laminate tests under extreme conditions.