Study On Mechanical Properties Of Porous Hierarchical Composite Structure

The energy absorption structures with excellent mechanical properties and lightweight performance are critical to the safety of vehicles and aircrafts.Therefore,the crashworthiness behavior of porous hierarchical composite structure are drawing more and more attention and have became a research hotspot in the field of composite structure in recent years.This paper presents a series of novel porous hierarchical composite structures,investigating theirs crashworthienss properties under multiple imopacting conditions by using theoretical analysis,numerical simulation and experimental testing.The specific research contents mainly include the following aspects:1)The crashworthiness of natural porous materials were studied by experimental tests.The wood porous materials with three fiber directions and two aged gradients were manufactured,and tested for mechanical properties under quasi-static conditions.It was studied that the failure behaviors,deformation modes,force response and energy absorption on the wood porous materials.To explore the potential superior performance on crashworthiness of natural porous materials,the composite structures were constructed by combining with aluminum material and carbon fiber reinforced plastic tube.It laid the experimental foundation and provided a novel idea for bionic design to obtain and study the porous composite structure.2)The mechanical properties of two-dimensional periodic honeycomb structures were studied.It was proposed that the novel self-similar hierarchical honeycomb structures with triangular,quadrangular and hexagonal configurations.First of all,the numerical models of honeycombs under different impacting conditions were developed and then validated by quasi-static crushing tests.The out-of-plane and in-plane impacting characteristics of honeycomb with different configurations were compared and analysed by numerical method.The mean crushing force was predicted based on Simplified Super Folding Element thoery.Furthermore,the impacting responses of regular honeycomb structure and hierarchical honeycomb structure with different configurations were compared and studied.It was found that hierarchical factor N and the layer quantity n had obvious influence on crashwothiness on hierarchial honeycomb under different impacting conditions.The hierarchical triangular honeycomb structure and the hierarchical hexagonal honeycomb structure had the superior crashworthiness performance under the in-plane and out-of-plane impact loads,respectively.3)The mechanical properties of three-dimensional periodic porous lattice structure were studied.The mechanical properties of regular and hierarchical pyramidal,Kagome and X-type lattice were investigated under out-of-plane impacting.The regular and hierarchical X-type lattice were manufactured by selective laser melting technique and then quasi-static crushing tests were carried out.The crashworthiness behaviors were analysed by numerical method among regular and hierarchical lattices with different critical parameters.The results showed that hierarchical X-type lattice presented more superior crashworthiness.The hierarchical design method opened up a new route of designing novel porous composite structre with improved crash characteristics and lightweight performance.