Air Blast & Ballistic Impact Damage Evaluation of Air Force Composite Structures

There is a growing interest in the development of accurate and fast-running target vulnerability models that address the combined effect of fragment and blast on the damage of structures. Here by blast we refer to the dynamic pressure loading due to explosion in either air or water, or to the hydrodynamic ram as a fragment travels through a liquid. For the kill radii of interest, the fragments from the warhead typically arrive before the blast and perforate the structure. When the blast arrives it is loading this weakened, perforated, cracked structure. This increases the degree of damage to the plate well beyond what it would have sustained without the fragment-induced damage. Typically cracks propagate from the fragment-produced hole, petals are formed and the plate tears. Existing survivability and vulnerability codes simply add the cross sectional area of the fragments impacting the plate to determine the total hole area, ignoring fragment-fragment interactions, fragment-blast interactions and the potential for overlap of these areas. In this Phase II effort, we propose to develop an engineering model to predict the damage of a plate (metal or composite) subject to ballistic impact followed by blast pressure loading accounting for the interactions discussed above. Our model development derives from controlled tests in a scaled Ram Gun system, Finite Element Analyses and simplified analytical models. This three prong approach is critical since neither area of study alone can produce the desired results within a reasonable time frame or budget. The model developed here can be interfaced with larger applications such as COVART, AJEM and Endgame Framework to expand their predictive capability.