Mechanical and structural optimisation of transverse and radial load bearing characteristics of reed straw based on finite elements

Abstract

Straw, as a widely available agricultural by-product, has several notable properties, including good mechanical strength, sustainability, and low cost, making it valuable for various research fields and applications. In this study, the lateral and radial load-bearing characteristics of reed straw were investigated, focusing on structural optimization using Micro-Computed Tomography (Micro-CT) and Mimics inverse reconstruction techniques, combined with finite element analysis (FEA). The approach compared the mechanical properties of real and optimized straw models. Micro-CT scanning was employed to capture cross-sectional image data, which were then processed using Mimics software to generate three-dimensional models representing the outer skin, vascular bundles, and inner foam core. Material properties and loading conditions were defined using finite element analysis to establish a simulation model that assessed the reed straw's mechanical properties under axial and radial compression. To support biomimetic design, the mechanical performance of the real and optimized models was simulated and compared. The results showed that the nodal features effectively maintained structural stability by providing radial constraints to the outer bark and pith core during both axial and radial compression. The internal vascular bundles also played a significant role in withstanding compression. The microstructure analysis revealed that vascular bundles are scattered throughout the tissue, with increasing size and decreasing number towards the inner regions, and their uniformity and density directly influence the straw's mechanical properties. The stress distribution between the real and optimized models was relatively uniform, with the real model showing maximum stress values of 64.59 MPa under axial compression and 1.17 MPa under radial compression, indicating distinct differences in load-bearing capacity. The maximum stress generally occurred at the nodes, which are the most vulnerable to failure but also contribute to enhanced structural stability. This study provides valuable insights into the mechanical response of reed straw under different compression conditions, offering a useful reference for future research and applications of bio-materials.