Multi-layer structure design, fabrication and numerical simulations of 3D woven spacer fabric composites with improved mechanical properties

The 3D woven spacer fabric lightweight composites (WSFC) show promising applications in construction, transportation and aerospace. In this study, the 3D WSFC with different structural variations (e.g., layer thicknesses, stacking and face layer thickening) were designed and fabricated. The fracture strengths of single-layer WSFC in the weft direction with layer thicknesses of 5, 10 and 15 mm were 54.4, 14.3, and 5.4 MPa. In the weft direction, the fracture strengths of double- and triple-stacked 3D WSFCs were 30.6 and 21.7 MPa, which improved 1.1 times and 3.0 times as compared with those of original single-layer 3D WSFCs, respectively. The double- and triple-stacked WSFC also had large flexural deformation. The 3D WSFC with double-layer misaligned stacking had the similar flexural strengths in both directions, which obviously reduced the performance differentiation of 3D WSFC in different directions. With the addition of face layer fabric, the mechanical performances of 3D WSFC were notably enhanced, and the damage modes were changed from brittle failure to ductile failure. Furthermore, a multi-scale model of 3D WSFC with different structural variations was developed for numerical simulation to analyze the stress distribution and damage mechanism. Highlights center dot Stacking design obviously improves mechanical properties of 3D WSFC. center dot WSFC with misaligned stacking has similar flexural strengths. center dot A multi-scale elastic-plastic damage model for 3D WSFC is established. center dot Damage modes of WSFC are changed with the stacking method.