Abstract: To enhance the impact resistance of carbon fiber laminates, a three-dimensional hollow woven spacer fabric was integrated with the carbon fiber laminate through a integratedforming process. Various materials, including glass fiber and carbon fiber as well as different thicknesses (3 mm, 7 mm, and 15 mm) of spacer fabrics, and carbon fiber biaxial warp-knitted fabrics were designed and prepared as hybrid reinforced composites. Continuous low-velocity impact tests were conducted at energy of 9 J, 15 J, 21 J and 27 J. This study further investigated the effect of stackingsequence on impact performance and damage mechanisms. The findings demonstrate that unilateral distribution of spacer fabric significantly enhances the initial energy absorption. Specifically, the specific energy absorption (SEA) increases by over 25.74% in comparison to pure laminate configuration. At the impact energy of 27 J, the SEA experiences a reduction of at least 33.67%. An increase in the thickness of spacer fabric correlates with an enhanced energy absorption capacity. Furthermore, it is found that the energy absorption of carbon fiber spacer fabric is superior to that of glass fiber spacer fabric, with a 21.46% reduction in SEA during a 27 J impact. The energy absorption of sandwich structure is positively correlated with the thickness of spacer fabric and remains effective after progressive impact. At the impact energy of 27 J, SEA of sandwich structure with 15 mm glass fiber spacer fabric shows an enhancement of 2.48%. Additionally, the impact resistance of sandwich structure with carbon fiber spacer fabric, when compared at equivalent thickness, demonstrates superior performance relative to the glass fiber counterpart. At the impact energy of 27 J, the SEA for the carbon fiber structure is observed to decrease by 30.34%.

Key words: hybrid reinforced composite, 3D woven spacer fabric, low velocity impact, layering sequence