Experimental study on the influence of impact positions on compression-after-impact behavior of composite stiffened panels

The effect of impact positions on the damage tolerance of T-stiffened composite panels was investigated by experimental methods. Low velocity impact (LVI) was carried out at two typical locations, namely the center of skin between two stiffeners and the stiffener flange tip of the panels, to introduce visible impact damage (VID). With the help of visual inspection and nondestructive detection, obvious differences in damage morphology from different impact positions were observed. Compared with the skin impact, the damage types induced by the flange tip impact were more complicated, including fiber fracture, matrix cracks, delamination, ply splitting and interface debonding. compression-after-impact (CAI) tests were performed on the intact, skin-impacted and flange-impacted stiffened panels respectively. The experimental results show that the deformation of skin-impacted panels is restricted due to blade supports, inducing the damage initiation and causing ultimate destruction, which is extremely similar to intact panels. For the flange tip impact, whilst, damage propagation is along the transverse direction from the impact location, which is entirely different from skin impact in the damage scenario, promoting the structural failure and reducing significantly the residual compressive strength. Additionally, the digital image correlation (DIC) was used to monitor the deformation of the specimens during compression and compared with the results of contact measurement, which verified the feasibility and superiority of the test method applied to the mechanical properties of materials.