Loading rate effect on woven glass laminated plates by penetration force

The effect of the loading rate on 2.9 mm thick E-glass/epoxy woven composite laminates subjected to quasi-static contact and impact forces applied in the transverse direction was investigated. The quasi-static contact test was performed using a 12.7 mm hemispherically-tipped indentor. On the other hand, impact was conducted using a gas gun with projectiles of the same frontal shape weighing 8.7 g, 17.7 g and 35.5 g. The test speeds were from several m/s to the ballistic limits of the laminates. The impact response was measured using the self-developed laser Doppler anemometer (LDA) system and was subsequently converted into the force and displacement histories. Significant loading rate effects were observed when comparing the laminates loaded quasi-statically to those struck by projectiles with a four-fold difference in mass. These effects included differences in the impact force history, a drastic increase of the force peak and the absorbed energy, and a completely different delamination damage pattern. Thus, the loading rate effect for composite laminates reinforced by glass fibers cannot be overlooked. On the other hand, fiber breakage throughout the plies on the distal side of laminates was found to absorb a significant amount of impact energy. The absorbed energy versus the initial projectile energy for the dynamically loaded specimens, when plotted in a non-dimensionalized manner, was found to have a bilinear relationship regardless of the projectile mass employed. This bilinear line was also closely bounded from below by the quasi-static results.