Behaviour design of 3D printed beetle elytron inspired sandwich plate (beetle elytron plate) under lateral load

Abstract

Sandwich panels with cellular cores are commonly used in many industries, such as Construction and Aerospace, owing to their excellent structural efficiency. To achieve further structural efficiency, researchers are turning their attention to nature-inspired structures. This project focuses on beetle elytron plate (BEP) which is a new type of sandwich structure inspired by the internal architecture of beetle elytra and characterized by trabecular (tubular) structure in the core. Some preliminary researches have studied their material properties. This research focuses on design methods for fundamental bending and shear behaviour of BEP as an engineering structure. The research of this thesis is carried out by using a combination of numerical modelling and physical tests to provide a detailed understanding, leading to the development of analytical methods to quantify elastic buckling, elastic-plastic buckling and post-buckling stresses of the compressive skin as well as elastic shear buckling stress of the core web of BEP under lateral loads. Numerical simulations are carried out using the general finite element software ABAQUS. Validation case studies include existing analytical solutions for elastic buckling of the compressive skin of conventional sandwich plates (CSPs) with flexible core support, elastic-plastic buckling of the compressive skin of CSPs with simple and fixed supports under uniaxial and biaxial loading conditions, and experimental results of 3D printed CSPs and BEPs beams under bending and shear conducted by the author. The experiment consists of a total of 27 physical tests conducted on 3D printed BEPs and CSPs, including 18 tests (9 each for BEP and CSP) under bending and 9 tests for BEP under shear. The variations of these specimens, covering different values of slenderness ratios of the compressive skin and the core web, ratio of the thickness of the compressive skin to the core web, and aspect ratio of the core web, are guided by numerical modelling results to ensure that the tests are able to cover the complete range of buckling behaviour of CSP and BEP. The test results reveal that a large amount of post-buckling resistance of the compressive skin exists after observation of elastic and elastic-plastic; however, under shear loading, although there is a considerable amount of additional load after elastic shear buckling, the scatter is large and shear failure is brittle. Therefore, for engineering applications of BEP, as for CSP, the post-buckling stress of the compression skin and the elastic shear buckling stress of the core should be used. The analytical solutions for these stresses are the focus of this thesis. Based on numerical results, three buckling modes can be observed on the compressive skin of BEP: interior buckling in the space between four adjacent trabeculae, exterior buckling on the edge between two adjacent trabeculae and circular buckling within each individual trabecula. To achieve the maximum structural efficiency of BEP, interior buckling is preferred and is the focus of this research for further analytical development. The geometric conditions for the interior buckling are: i) the ratio of trabecular radius to cellular length does not exceed 0.25 to avoid circular buckling; ii) the ratio of edge distance to cellular length does not exceed 0.3 to avoid exterior buckling. In order to analytically calculate the final post-buckling stress of the compressive skin of BEP, it is necessary to calculate the elastic and elastic-plastic buckling stresses of the compressive skin with simple, fixed and flexible supports, as intermediate values. The elastic buckling stresses under simple, fixed and flexible supports are calculated based on the rotational spring analogy theory using shape functions identified from numerical results. The elastic-plastic buckling stresses of BEP with simple and fixed supports are calculated by adapting the analytical solutions for CSP; that with flexible support is c

Date of Award	31 Dec 2022
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Meini Su (Supervisor), Andrew Foster (Supervisor), Yong Wang (Supervisor) & Paulo Jorge Da Silva Bartolo (Supervisor)