Mechanical Properties and Damage Mechanism of 3D Woven Spacer Composites Improved with Changing Face Layer Structures: Experimental and Numerical Study

The thin face layers of three-dimensional (3D) integrated woven spacer fabric-reinforced polymer composites (WSFC) result in the limited mechanical properties. In this work, changing the face layer structures (e.g., thickening, asymmetrizing, differing woven structures) were investigated to improve the mechanical properties of WSFC. The results show that the 3D WSFC in the weft direction have significantly greater flexural strength than those in the warp direction. When the two-dimensional (2D) fiberglass fabrics for thickening the face layer of WSFC are increased from 1 to 3 layers, the flexural strengths of composites in the warp direction improve with 14.3%, 39.3%, and 97.2% as compared with the original composites, respectively. Besides, the flexural behavior and damage mode of WSFC with additional face layers also change. For asymmetric lay-up, the flexural properties of WSFC with the additional layers on the stressed side are better than those of WSFC with the additional layers on the non-stressed side. Furthermore, the multi-scale elastic-plastic damage models of 3D WSFC with changing face layer structures are established, and the numerical simulation is performed to analyze the damage mechanism.