Shock Loading Mitigation Performance and Mechanism of the PE/Wood/PU/Foam Structures

Abstract Multilayer structures have found extensive applications in personal protection engineering, which are considered effective materials in mitigating shock loads. In this paper, the effect of layer thickness and layout on the shock mitigation performance of multilayer structures is evaluated experimentally, and the mitigation mechanism is analyzed. The tested structures are designed into three groups, composing of four protection materials, including ultra-high molecular weight polyethylene composite (PE), wooden laminated composite (Wood), polyurea (PU), and expanded polyethylene foam (Foam). In the experiment, a pressure test platform is developed to measure the transmitted shock pressure pulse after passing through the structure, and the tested structure supported by the platform is subjected to the shock loads generated by a shock tube facility. Experimental results indicate that the transmitted pressure amplitude can be considerably reduced by increasing the thickness of the Foam layer. Besides, with the same thickness, when the Foam layers are staggered and arranged within the structure, the transmitted pressure amplitude is much higher than that of when they are entirely arranged as the back layer within the structure. Further, a new energy transmission model is proposed to reveal the shock mitigation mechanism, which considers that the output energy transmitted into the target is generated jointly by the input energy from the shock loads and the energy transmission efficiency of the structure. The specific energy values are quantitively calculated through numerical simulation. Results indicate that for different layer layouts of designed structures, the energy transmission efficiency changes little, but the input energy varies a lot. Arranging the Foam layers as the back layer within the structure can reduce their compressed deformation under shock loads, which contributes to much less input energy and better mitigation performance.