Effect of layup layers and stitch row spacing on drop-weight temperature impact and compression after impact behavior of stitched composites

• Combining the characteristics of force displacement/time and energy/velocity time curves during the impact process, explore the influence of the number of layup layers and stitch spacing on dynamic load transfer. • Study the influence of temperature changes on the impact performance and damage mode of composite materials, and reveal the weakening mechanism of matrix softening on mechanical properties under high temperature environment. • Combining ultrasound C-scan technology with compression after impact characterization to determine the damage area and residual compression strength after impact. The number of layup layers and stitch row spacing have important effects on the mechanical properties of 3D stitched composites under different temperature impact loads. In this study, the effects of layup layers and stitch row spacing on the impact behavior of composites were systematically analyzed via drop-weight temperature impact experiments. The results show that, compared with those of the unstitched composites, the fiber breakage and delamination damage areas of the stitched composites subjected to impact are significantly smaller, resulting in the greater strength of compression after impact. With decreasing stitch row spacing, delamination damage is further reduced, resulting in increased impact resistance and increased peak load. However, with increasing impact temperature, the composite undergoes a progressive increase in damage. The strength of compression after impact decreases with increasing temperature, and first increases but then decreases with decreasing stitch row spacing.