The damage resistance of composite structures to high-velocity ice impacts and their tolerance to impact damage

Since their inception, polymer composite structures have been susceptible to damage by impacts. This source of damage poses a realistic threat which can significantly compromise the integrity of composite structures. In particular, the high velocity impact of hail ice onto composite structures is an area not well investigated. Experimental and analytical investigations have therefore been performed in the study of hail ice impacts onto thin gauge carbon/epoxy composite panels. Experiments were conducted using a gas cannon to project cast ice spheres which simulate real hail ice. From these experiments, the failure modes and progression of failure modes for the materials tested were determined. Numerical analytical studies were then conducted using the explicit finite element code DYNA3D to simulate the ice impact experiments. The simulations successfully predicted the elastic response of the composite panels when impacted by ice at high velocity. Furthermore, the numerical models permitted the gathering of information impossible to obtain experimentally, such as the interlaminar stress state in the panel during the impact event. Simulation results were used to compose a simple energy based relationship to predict the initiation of impact damage in the composite panels tested.; While predicting impact damage is of real-world interest, the evaluation of a composite structure's tolerance to the presence of impact damage is also of interest, especially with regard to the impact damage forms which can exist but are not readily detectable. The operation of structures containing these non-detectable forms of impact damage is a safety threat. To address this safety threat, an energy based analytical methodology for the prediction of the buckling of delaminated composite plates has been developed. Both possible failure modes of global plate and local sublaminate buckling have been predicted and were validated using numerical finite element analyses.