Mechanisms of diverting out-of-plane impact to transverse response in plate structures

Impact protection structures are required to efficiently use material and provide maximum energy absorbing capability. When using plate structures against out-of-plane impact, most impact energy is dissipated near the impact area, resulting in low use efficiency of material. In this study, material distribution is analyzed to reveal its influence on intrusion in the out-of-plane direction and dynamic response in the transverse direction in plate structures. First, partitioning a plate into two plates along the thickness direction, mechanisms of dynamic response in the out-of-plane direction are studied. The upper plate takes impact from intruding object and the lower plate serves as delayed defense when the two plates contact and interact to each other. There exists optimal configuration range of the thickness partition and the gap between the plates for minimizing intrusion. The configuration determines contribution to energy absorption by membrane deformation. Second, mechanisms of diverting out-of-plane impact to energy dissipation in the transverse direction are studied. The material distribution determines the area on plate where most energy is dissipated. It has been found that energy dissipation can spread transversely to a larger range on plate when the strength is lower, demonstrating competing effects between deformation capability and activation of inertia. By adding non-structural mass on plate, it has been found that it can influence range of plastic deformation as the result of the inertial effect. The mechanism has been verified by using a mass-spring model. These mechanisms revealed offer insights to diverting out-of-plane impact transversely on protection plate by using non-uniformly distributed mass and material properties to increase energy absorbing efficiency.