Investigation Of Static Mechanical Property Of The Bidirectional Self-locked Thin-walled Tubular Structure And System

Thin-walled structure has been widely used in transportation,aerospace,and other engineering fields due to lightweight,high energy absorption efficiency,low cost and so on.However,the problems of low energy absorption of a thin-walled structure,difficulty in disassembly and assembly of a nested system,and the inability of achieving multi-directional self-locked have yet to be resolved.Therefore,it is necessary to study a new type of energy-absorbing protective structure that can be assembled,expanded,and multi-directional self-locked.This paper proposed a novel bidirectional self-locked thin-walled tubular structure,and conducted related research in terms of structural configuration design,manufacturing process and mechanical performance characterization.The following three aspects were mainly studied:Firstly,based on the design idea of assembly and expansion,the design method of bidirectional self-locked thin-walled tubular structure was proposed.Based on the 3D printing technology,a novel PLA bidirectional self-locked thin-walled tubular structure was manufactured,and the bidirectional self-locked property of the system was verified by the oblique centralized compression experiment.Through static lateral compression experiments,the load-bearing capacity,energy absorption and deformation modes of bidirectional self-locked thin-walled tubular structure and system,dumbbell-shaped thin-walled tubular structure and system,rectangular-shaped thin-walled tubular structure and system were studied.The results showed that the bidirectional self-locked thin-walled tubular structure and system had higher load-bearing capacity and energy absorption.A finite element model of static lateral compression of the bidirectional self-locked thin-walled tubular structure was established and a parametric study was conducted.The finite element results were in good agreement with the experimental results.Secondly,based on the super folding element theory,the theoretical prediction formula of the mean crushing force of the bidirectional self-locked thin-walled tubular structure under static lateral compression was established.The theoretical prediction results were in good agreement with the experimental results.Through theoretical analysis,the deformation energy absorption mechanism of the bidirectional self-locked thin-walled tubular structure was revealed,and to further improve the structural energy absorption by configuration design.The results showed that the specific energy absorption and mean crushing force of the novel bidirectional self-locked thin-walled tubular structure with configuration design were increased by 55.6% and 68.3%,respectively.The finite element model of the bidirectional self-locked system was established and the numerical simulation research of the system's static oblique central compression was carried out.The numerical simulation results were in good agreement with the experimental results.The results showed that the specific energy absorption and maximum compression force of the bidirectional self-locked system with configuration design were increased by 100.0% and 86.8%,respectively.Finally,the hot-pressing fabrication method of carbon fiber reinforced epoxy resin matrix composite bidirectional self-locked thin-wall tubular structure was developed.Through static lateral compression experiments,the load-bearing capacity,energy absorption and deformation modes of the composite bidirectional self-locked thin-walled tubular structure and system were studied.The finite element model of the static lateral compression of the ABAQUS/Explicit three-dimensional composite bidirectional self-locked thin-walled tubular structure with 3D-Hashin failure and damage evolution was established,and the influence of the layup angle on its load-bearing capacity,energy absorption and deformation mode were studied.Further through the PMI foam-filled and local stiffness reduction,it had been achieved that the composite bidirectional self-locked thin-walled tubular structure with a crushing force efficiency increase of 139.9%(from 33.3% to 79.9%)and a specific energy absorption increase of 27.5%(from 4.0 J/g to 5.1 J/g),while the initial peak force drops by 36.4%.