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 reduct ion of angle-ply composite laminates due to low-velocity impact. Three angl e ply lay-up were chosen: [+30 degrees,-30 degrees](2s), [+45 degrees,-45 d egrees](2s) and [+60 degrees,-60 degrees](2s). Impact tests were performed at different impact energy level and then an ultrasonic scan NIDI was perfo rmed, to evaluate the internal damage. The impacted specimens were subjecte d to tensile load until failure occurs and the ultimate tension strength af ter impact was compared with the corresponding value for undamaged specimen s. Moreover, for a better understanding of the failure phenomenon, some tensio n tests for damaged specimens were interrupted at different load levels (re spectively at 30%, 60%, 85% and 90% of the corresponding failure load) and ultrasonic scans at any step were performed to evaluate the delamination gr owth due to tensile load. A correlation between the amount of delamination areas and the impact energy has been determined.