경량화용 자동차 전면부 사이드부재의 충돌안전성 평가

Abstract

The most important objective in designing automobiles is currently to focus on environment-friendly aspect and safety performance aspect. As for the environment-friendly aspect, the issues are the overall movements toward lightweight automobile production due to the fuel-efficiency improvement and heavier restriction on exhaust, however in contrast, the issues of the safety performance such as crush safety, comfort level and muti-functional programs demand increase of automobile’s weight. Therefore, the designing automobile should be more concerned on the aspect of securing safety performance, but at the same time, it also should consider reducing weight of automobile structural member. In this study, for lightweight design of side member, CFRP side member was manufactured from CFRP uni-direction prepreg sheet. The stacking condition related to the energy absorption of composite materials is being considered as an issue for the structural efficiency. Therefore, the axial collapse tests were performed with change of the stacking condition. The collapse mode and energy absorption characteristics were analyzed according to stacking condition. The experimental results are as follows; 1. The CFRP hat shaped section member was collapsed according to the different orientation angles by compounding of the 4 different modes: transverse shearing, laminar bending, brittle fracture, and local buckling. When the fiber orientation angle is small, the member absorbed energy by laminar bending. As the fiber orientation angle increases, the member was absorbed energy by local buckling and matrix crack due to transverse shearing. 2. As the fiber orientation angle increases, as shown the absorbed energy decreases linearly. This means that when the fiber orientation angle is small, energy was absorbed by the laminar bending and break of fibers, however as the fiber orientation angle increases, matrix crack takes place, instead of the fiber breaking. energy absorption was most effective when the fiber orientation angle of CFRP was 0°/90° and 90°/0°. 3. The absorbed energy increases to the interlaminar number of 6, with increasing interlaminar number. However, decreasing trend is observed on moving to the interlaminar number of 7. Since a key element of the energy absorption is the crack growth and extension, the cracks may be classified as interlaminar cracks, intralaminar cracks and central cracks. It is apparent that the interlaminar cracks increase, but the growth of intralaminar and central cracks decrease with increasing interlaminar number. 4. The energy absorption capability of the members increases as the sectional area ratio (sectional area ratio of flat member to "∩" shaped member) increase due to stress concentration on their edges.