Effect of Z-pin insertion angles on low-velocity impact mechanical response and damage mechanism of CFRP laminates with different layups

Abstract This paper investigates the effect of Z-pin insertion angles (60°, 75° and 90°) on low-velocity impact mechanical response and damage mechanism for cross-ply and quasi-isotropic layups. The laminates were impacted with 25 J, 40 J and 60 J to obtain different mechanical response and damage status (permanent dent, delamination and backside damage). Experimental results demonstrate that the impact resistance is reduced with the decreasing Z-pin insertion angles, which is accompanied by more severe backside cracking, larger impact dent and delamination area. This phenomenon is more significant in cross-ply laminates compared with quasi-isotropic layups. Additionally, 60° pinned cross-ply laminates show asymmetry delamination because the damage modes of Z-pins on both sides of the impact center are different, which results in the different delamination resistance of the two sides. These findings can give some guidance for choosing Z-pin insertion angles when Z-pinning in different layups.