Abstract: The failure modes and damage processes of weft V-shaped woven spacer composites were examined under flat and edgewise compression loads. The ABAQUS program was used to create a multi-scale single-cell composite model and define periodic boundary conditions. The elastic characteristics of fiber bundles were studied in order to predict the macroscopic material elastic constants. For the progressive damage analysis of weft V-shaped 3D woven spacer composites, a subsequent improvement of the UMAT subroutine in Fortran provides a 3D Hashin damage criterion and a Camanho stiffness degradation scheme. The results reveal that the simulated and test outcomes are consistent. Under the flat compression stress, the V-shaped pile warp group with higher bending amplitude cracked first, whereas the pile warp group with lower amplitude fractured subsequently, resulting in a secondary peak load. Stress concentrations at the interweaving of the pile warp and weft, as well as at the pile warp’s flexure, with fractures concentrated at the pile warp’s highest flexure and at the interface with the panel, and no obvious panel breakage; the principal load-bearing entities under edgewise pressure are the resin panel and the inner resin yarn, with the top layer of weft yarn under more pressure and the spacer layer of pile warp under less pressure. Fracture occurs mostly between the two rows of V-pile yarns, with gradual resin breakdown, fiber debonding, and yarn breaking as failure modes.

Key words: weft V-shape, 3D woven spacer composite, finite element simulation, compression properties