Low-velocity impacts on preloaded GFRP specimens with various impactor shapes

The simultaneous effect of impactor shape and biaxial preload on the impact response of thin glass fibre reinforced polyester laminates is investigated herein. Using a specially designed drop weight test rig, specimens were impacted at initial impact energies of 4 J and 6 J using steel flat, hemispherical, ogival and conical impactors, all 12 mm in diameter. Biaxial tension of 500 and 1000 microstrain was applied to the specimens. The applied levels of preload were found to have little effect on the impact response of the GFRP specimens. Due to the stiffening effect of the biaxial tension, the contact duration and deflection were found to decrease with increasing preload. However, the peak force, absorbed energy and damage area were largely unaffected by the preload. The indentation depth produced by the conical impactor at 4 J increased significantly as preload was applied. However, this did not correspond to an increase in damage area.