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Ballistic threats armed with high energy explosives create a particularly damaging shock wave and fragmentation environment for lightweight aircraft structures. Specifically engineered composite structure may mitigate these damaging phenomena by tolerating penetration with minimal collateral damage and by attenuating shock wave reflection and transmission. Documented herein is the development of composite structural concepts for fragment damage mitigation and shock wave attenuation using advanced analysis techniques for phenomenological sensitivity, constituent optimization, and structural response prediction. Mitigation and attenuation analysis techniques are validated through panel impact and explosive testing. A full scale subcomponent article was designed and fabricated and successfully subjected to ballistic and residual strength testing. typical high energy explosive ballistic threat damages structure through fragmentation, shockwave, and heat, as shown in Figure 1. High-velocity fragments resulting from both the kinetic energy of the ballistic threat and propelled by explosion forces impact and penetrate exposed structure. The explosive reaction of energetic materials produces both a damaging, high-pressure shockwave and intense thermal heating. Boeing has pioneered and validated methods to simulate these explosive events and the resulting effect on exposed aircraft structure. This has lead to effective, novel solutions to make aircraft structure more tolerant of these hostile environments. The methodology employed, outlined in Figure 2, begins with a knowledge base of hostile threats including the physical phenomena associated with the threat, the effects of this phenomena on target structure, the resulting structural degradation, and the analysis tools to accurately simulate relevant behavior. This knowledge base comes from public domain literature, past United States Department of Defense research and development, and proprietary industry information. For example, a specific threat may produce a circular fragmentation pattern with relatively close spacing between the penetrations. The fragments are closely followed by a shockwave which overloads the area within the circular pattern, blowing it free. The area around resulting large hole becomes unstable and buckles under flight loads, followed by general collapse of the airframe structure and loss of the aircraft. Defeating such a threat may require several steps including limiting collateral damage during penetration, preventing penetration damage propagation and coalition, preventing local instability of damaged structure, and/or preventing general instability by tolerating local buckling. A |
