Study Of Thin-walled Structures With Characteristics Of Bamboo Vascular Bundles

It is important to improve the stiffness-strength and energy absorption properties of thin-walled structures while ensuring light weight.After millions of years of natural selection,bamboo has evolved a structure with outstanding mechanical properties,with excellent strength and stiffness properties in both the axial and lateral directions.The porous and radial skeletonisation structure of the bamboo cross-section at the microscopic level is a structure that not only gives bamboo its lightweight,high-strength thin-walled characteristics,but also good energy absorption properties.In this study,the design of thin-walled tubes and thin-walled lattice panels are inspired by the microscopic morphology of bamboo vascular bundles and the arrangement of vascular bundles in the tissue,based on the principles of engineering bionics and the requirement for lightweight.The effects of structural parameters on the crashworthiness of the two proposed bionic thin-walled structures are investigated based on experimentally validated finite element models.In the study of the bionic tube,the effects of the structural parameters of the bionic tube on its crashworthiness are first analysed.The best crashworthiness is obtained when the ratio of the fascia length to the bionic through-hole circuler core is 7:3 and the bionic fiber sheath unit（VF）is semi-circular（i.e.б=180°）.Secondly,the effects of the connection between the bionic unit and the outer circular tube（C-x）on the crashworthiness are analysed,and the crashworthiness of C-VF-C-αβ_б=180°is found to be the best.Finally,the fractal method is introduced to investigate the crashworthiness of VF unit under different fractal level.In the study of bionic lattice panels,the crashworthiness of three bionic lattice panels are significantly better than that of conventional lattice panels through quasi-static compression experiments of 3D printed samples.The effect of structural parameters on the crashworthiness of the bionic lattice panels are then investigated and it is found that the crashworthiness of the bionic lattice panels increased with increasing thickness and bionic unit’s number,but the mass also increased accordingly.Therefore,the paper concludes by considering the mass factor and introducing a lightweight high-strength trade-off fraction（Lw Hs_i）to measure the effect of the structural configuration of the three bionic lattices on the crashworthiness under both radial and transverse compression conditions.In summary,this thesis combines bionics and structural design to develop bionic design of thin-walled tube and thin-walled lattice plate structures based on the microscopic morphology of bamboo vascular bundles and their arrangement in the tissue,and demonstrates the excellent energy absorption performance of the bionic structures by means of theoretical analysis,numerical simulation and experimental verification.Then,the effects of the structural parameters on the crashworthiness of the proposed bionic structure are investigated.Finally,the optimum crashworthiness structure is obtained by further optimisation while ensuring light weight.