Evaluation on shear modulus of cylindrical honeycomb core structures

Abstract

The objective of this study is to evaluate a shear modulus of cylindrical honeycomb core structures with various core sizes and curvatures. Honeycomb core structures exhibit high rigidity only in the out-of-plane direction and cannot effectively support multidirectional loads. Especially for rotating machinery including vehicle tires, the structures are required to support radial loads and also shear loads generated by torque under acceleration and deceleration. The cylindrical honeycomb core structures are a potential solution for applications to rotating machinery, as they feature hexagonal cells arranged radially to support radial loads during rotation. Given the necessity to elucidate the mechanical properties for practical applications, this study quantitatively evaluates the relationship between the geometry and shear modulus of the cylindrical honeycomb core structures by using finite element analysis and experiment. In the experiment, paper-made specimens of the cylindrical honeycomb core structures were mounted and tested on the experimental devices converting translational displacement to rotational displacement via a slider-crank mechanism. As for the structural analysis, the experimental conditions were reproduced by applying rotational displacements to the cylindrical honeycomb core structures and measuring the corresponding reaction forces. The material properties used in the analysis were derived from compression tests of the paper used in the experiments. The experimental and numerical results indicated that as the core size increased, the shear modulus decreased, similar to the conventional flat honeycomb core structures, and the shear modulus on the outer periphery while inner periphery was fixed was smaller than that on the inner periphery while outer periphery was fixed. Additionally, as the inner diameter increased and approached the outer diameter, the shear modulus at the outer and inner peripheries ultimately converged to that of a flat honeycomb core structure with a geometry equivalent to the outer periphery of the cylindrical core structures.