Out-of-plane mechanical behaviors of a side hierarchical honeycomb

Hierarchical honeycombs have been extensively used as protective devices due to their superior mechanical performance. In this paper, a novel side hierarchical triangular honeycomb (SHTH) constructed by sequentially arranging a certain number of similar subtriangles on the geometrical side of an ordinary triangular honeycomb (OTH) is proposed to enhance structural mechanical performance. Experimental specimens and finite element models of SHTHs are developed to explore their mechanical behaviors under out-of-plane compression, and the numerical models are validated based on the results of crushing tests of SHTHs. Numerical comparisons of the SHTH, OTH and double-triangular honeycomb (DTH) are performed and illustrate that the SHTH has a higher collision force level and better energy absorption than the OTH and DTH due to more stable collapse deformation. Moreover, a parametric investigation of the SHTH is performed to explore the influences of the relative density, hierarchical factor and layout of the honeycomb on crashworthiness. The results show that the crashworthiness of the SHTH is improved with increasing relative density and number of layouts. Furthermore, the stable energy absorption and load bearing efficiency of the SHTH are observed when the hierarchical factor is close to 10. A theoretical model of the SHTH is also derived and validated based on simplified super folding element theory (SSFE) and numerical analysis. The findings of this study provide a new method for designing an energy absorber with excellent protective performance.