Energy absorption and bending stiffness in CFRP laminates : the effect of 45º plies

The impact characteristics of cross-ply and angle-ply composite laminates were investigated, with an instrumented impact drop tester by performing gravity-assisted drop tests on [0/90]6s and [0/45/90]4s laminates. The impact energy was kept constant at 12 J for all the tests. From the dynamic responses presented here as force history, energy history and force–displacement plots, relevant characteristics such as contact time, delamination load, absorbed energy, bending stiffness, after impact deflection, etc. were obtained. The plots were non-smooth, disclosing the salient features of the composites. It was important to note that the [0/45/90]4s was more resistant to impact bending, but incurred more damage as exhibited by its higher contact time and absorbed energy. The laminates were sectioned through the impact point and magnified macro- and micro-photographs were taken to show the failure modes, which include delamination, matrix cracking, etc