Dynamic crushing behaviors and enhanced energy absorption of bio-inspired hierarchical honeycombs with different topologies

In order to pursue good crushing load uniformity and enchance energy absorption efficiency of conventional honeycombs, a kind of bio-inspired hierarchical honeycomb model is proposed by mimicking the arched crab shell structures. Three bio-inspired hierarchical honeycombs(BHHs) with different topologies are designed by replacing each vertex of square honeycombs with smaller arc-shaped structures. The effects of hierarchical topologies and multi-material layout on in-plane dynamic crushings and absorbed-energy capacities of the BHHs are explored based on the explicit finite element(FE) analysis.Different deformation modes can be observed from the BHHs, which mainly depend upon hierarchical topologies and impact velocities. According to energy efficiency method and one-dimensional(1D) shock theory, calculation formulas of densification strains and plateau stresses for the BHHs are derived to characterize the dynamic bearing capacity, which is consistent well with FE results. Compared with conventional honeycombs, the crushing load efficiency and energy absorption capacity of the BHHs can be improved by changing the proper hierarchical topology and multi-material layout. These researches will provide theoretical guidance for innovative design and dynamic response performance controllability of honeycombs.

A comprehensive study on Li_(4)Si_(1-x)Ti_(x)O_(4) ceramics for advanced tritium breeders

Hetero-element doped lithium orthosilicates have been considered as advanced tritium breeders due to the superior performances.In this work,Li_(4)Si_(1-x)Ti_(x)O_(4) ceramics were prepared by proprietary hydrothermal process and multistage reactive sintering.The reaction mechanism of Li_(4)Si_(1-x)Ti_(x)O_(4) was put forward.XRD and SEM analyses indicate that insertion of Ti leads to lattice expansion,which promotes the grain growth and changes the fracture mode.The compressive tests show that the crush load increases almost four times by increasing x from 0 to 0.2.However,the thermal conductivity and ionic conductivity are the best when x=0.05 and x=0.1,respectively.Thermal cycling stability of Li_(4)Si_(1-x)Ti_(x)O_(4) pebbles was further appraised through investigating the changes of microstructure and crush load.After undergoing thermal cycling,the Li_(4)Si_(1-x)Ti_(x)O_(4) still show higher crush load compared with Li_(4)SiO_(4),despite Ti segregation in some samples.The x=0.05 sample exhibits excellent thermal cycling stability.In summary,proper amount of Ti doping can improve the crush load,thermal and ionic conductivity,and thermal cycling stability of Li_(4)SiO_(4).