Reduction of tensile strength in angle-ply composite laminates due to low-velocity impact

The purpose of the present paper is to evaluate the tensile strength reduction of angle-ply composite laminates due to low-velocity impact. Three angle ply lay-up were chosen: [+30 degrees,-30 degrees](2s), [+45 degrees,-45 degrees](2s) and [+60 degrees,-60 degrees](2s). Impact tests were performed at different impact energy level and then an ultrasonic scan NIDI was performed, to evaluate the internal damage. The impacted specimens were subjected to tensile load until failure occurs and the ultimate tension strength after impact was compared with the corresponding value for undamaged specimens. Moreover, for a better understanding of the failure phenomenon, some tension tests for damaged specimens were interrupted at different load levels (respectively at 30%, 60%, 85% and 90% of the corresponding failure load) and ultrasonic scans at any step were performed to evaluate the delamination growth due to tensile load. A correlation between the amount of delamination areas and the impact energy has been determined.