Response and damage mechanism of UHMWPE 3D weft-knitted inlay fabric reinforced composites under low-velocity impact

The 3D weft-knitted inlay (3DWKI) fabric structure enhances the mechanical properties of fabrics and their composites, while preserving the formation advantages of the weft knitting process. This study is a comparison of the impact resistance of 3DWKI composites and 2D plain woven (2DPW) laminated composites under identical impact energy conditions. Additionally, the impact response and damage mechanisms of 3DWKI composites under varying impact energies are analyzed. The results show that the energy absorption rate of the 3DWKI composite is 2.95% higher than that of the 2DPW composite for the same impact energy, 20 J. However, the dent depth of the 3DWKI composite is 1.65× that of the 2DPW composite, and the damaged area of the 3DWKI composite is only 20% of that of the 2DPW composite. The inlay yarn facilitates the propagation of stress waves in the horizontal direction, while the knitted yarn helps to reduce delamination damage and enhance the impact resistance of the composite. Furthermore, when the impact energy increases to 20 J, fiber breakage occurs in the interlock yarns, whereas only fiber tow splitting is observed in the inlay yarns, with no significant failure damage. Consequently, 3DWKI composites are promising for the development of full-form knitted composites that require enhanced impact resistance.