초경량/고강성을 갖는 ISB 판넬의 정적 특성 분석

Abstract

Recently, various research works of ultra-light weight structured materials with a type of sandwich panel are actively in progress to improve the efficiency of energy and the safety for transport vehicles. The sandwich panel is produced by joining metallic cores with three-dimensional inner structures, such as a honeycomb, a kagome structure, a woven metal, etc, to metallic skin sheets with welding and adhesion. Because the sandwich panel has a large empty area in the core, the panel has a light weight in comparison with the solid material with an equivalent volume. In addition, the strength, the stiffness and the crash worthiness of the sandwich panel are highly improved by the inner structures. Hence, several types of sandwich panel have been developed. However, the previously developed sandwich panel has hardly applied to automotive industries due to the heavy thickness, which is greater than several centimeters, and an expensive manufacturing cost. In order to overcome the disadvantages of the sandwich panel, inner structured and bonded panel with three-dimensional inner structures (ISB panel) has been developed. The objective of this research work is to investigate into static characteristics of ISB panels with ultra-light weight and high stiffness. In order to investigate mechanical properties and deformation characteristics and of ISB panel with a pyramidal inner structure and skin sheet for the case of a tensile load, several tensile tests have been carried out. From the results of the experiments, the stress-strain curve and the mechanical properties of the ISB panel and the skin sheet have been obtained. In addition, the mechanical properties of the ISB panel have been compared with those of the skin sheet by the view point of a specific modulus, a specific yield strength and a specific strength. In order to examine characteristics of material deformation and failure three-points bending test has been performed. In the three-points bending test, the expanded metal with a pyramidal shape and woven metal are employed as an internally structured material. Through the three-points bending test, the influence of design parameters for ISB panel on the specific stiffness, the failure mode and the failure map has been found. In addition, it has been shown that ISB panel with expanded metal is prefer to that with woven metal from the view point of optimal design for ISB panel. In order to evaluate the influence of the crimping angle on the load and stress distribution in the ISB panel with a pyramidal inner shape, three-dimensional elasto-plastic finite element analysis has been performed using a commercial code ABAQUS. The results of the analysis showed a good agreement with those of experiments. From the results of the analysis for the case of a uni-axial tension, it has been shown that the load and stress shared by the skin sheet are increased when the crimping angle is decreased. Through the results of the analysis for the case of three-points bending, it has been shown that the load and stress shared by the inner structures are increased when the crimping angle is decreased. In addition, the local strain distribution and deformation characteristics in the vicinity of the center depression area for the case of three points bending and the center area for the case of the uni-axial tension. Based on the above results, it has been shown that the ISB panel has an excellent mechanical properties in terms of a specific stiffness and a specific strength. In addition, it has been shown that ISB panel with a pyramidal inner structure can be optimally designed by the control of the crimping angle for the pyramidal structure in terms of mechanical properties and failure characteristics.