Woven glass/epoxy laminates subject to projectile impact

Impact results of woven E-glass/epoxy composite laminates are presented in this paper. A gas gun was employed to launch 12.7 mm diameter hemispherically-tipped projectiles 35.5 g in weight. The developed laser Doppler anemometer (LDA) system was successfully employed to record the projectile velocity history, whose range was from several m/s to twice the ballistic limit of the target, and was converted into the force history by using both the optimization and the polynomial curve-fitting methods. It was found that, when the projectile initial velocity was lower than the ballistic limit, the delamination area was approximately proportional to the initial energy of the projectile, and the relationship between the absorbed energy and initial energy of the projectile followed a straight line of unit slope when it was expressed non-dimensionally. Also, the incremental rate of the peak impact force became gradually smaller and finally reached a constant value at the ballistic limit, and the impact force history became progessively asymmetric. Beyond the ballistic limit, the absorbed energy remained approximately constant regardless of the increase of the initial striking velocity of the projectile. The peak impact force, on the other hand, was surprisingly found to increase again.