Damage resistance of single lap adhesive composite joints by transverse ice impact

This paper focuses specifically on the high velocity transverse impact of composite joints by hailstones. Impact tests with ice spheres onto composite lap joint specimens were conducted to determine the failure threshold energy describing damage initiation, and to investigate the modes of damage. The damage areas imaged by ultrasonic scanning were quantitatively measured and the specimens were also sectioned and observed with optical microscopy to determine the exact location of damage. The damage area versus impact kinetic energy was found to increase dramatically for impacts beyond the failure threshold. Delamination of the composite originated at the bond overlap termination facing away from the impact side. The damage usually occurred at specific ply locations and a transition of the delamination to other ply locations was also observed. Numerical simulation of the impact was conducted and the results show that the plies where delaminations were observed to occur have the highest peel and shear stresses.