FEM을 이용한 원형단면 CFRP 구조부재의 계면수 변화에 따른 압궤 특성 연구

Abstract

Global warming is one of the most serious global environmental problems that threaten human society and natural ecosystems. The average temperature of the earth rises every year because of greenhouse gases such as carbon dioxide(CO2), methane(CH4), and nitrogen dioxide(N2O). It constantly caused losses of material and economic by climate changes. As a result, the most countries actively have provided solutions and fulfilled their obligations through not only the Kyoto Protocol but the Paris Protocol. As global attention such these, many countries tightened fuel economy regulations then this has become an important issue to determine the survival of the automotive industry. In addition, "Dieselgate" which caused by the german automobile manufacturers in November 2015 has spread the negative perception of diesel engines. For this reason, the automotive industry has focused on developing lightweight materials to increase engine efficiency. Therefore, CFRP(Carbon Fiber Reinforced Plastic) having light weight, excellent mechanical properties, and environment friendliness has recently attracted attention. However, CFRP consisting of carbon fiber and resin, it is so complicated and the mechanical properties changed depending on the fiber orientation angle. Additionally since it is elastic-brittle materials and the failure happen suddenly, the prediction of failure is too difficult. Nevertheless CFRP has been widely researched in various industries including the aerospace industry under leader of developed countries such as the United States and Europe. But, almost of study on CFRP has proceeded through the method depending on a experimental approach. Therefore, by performing the experiment and FEA(Finite Element Analysis) simultaneously, minimize the loss for temporary and financial. As the data obtained from these ways should be utilized appropriately for application of CFRP to some parts or structural member in demand for enough mechanical properties through characteristic evaluation. In this paper, structural members with CFRP according to number of interface and layered structure were manufactured and collapse experiment and simulation about them were carried out. Based on their results, the following conclusions were drawn.

1. In the case where the outermost fiber orientation of the structural member is 0°, the load-displacement graph of the experiment and simulation was partial converged as the collapse mode showed difference between experiment and simulation. On the other hand, in the case where the outermost fiber orientation of the structural member is 90°, the load-displacement graph of the simulation was similar to experiment and the structural member after collapse also showed comparatively similar.

2. The the experiment showed that tendency to the peak load is decreased as the number of interface of the structural member increased from 3 to 7, and the simulation was also same. The error rate of the experiment contrast simulation showed that the outermost fiber orientation is 0°, the structural member with interface of 7 was the highest with –96%, and the others showed the error rate ranging from -4% to 23%.

3. The the experiment showed that tendency to the absorbed energy is decreased as the number of interface of the structural member increased from 3 to 7. But in the simulation, the case of outermost fiber orientation of 0° showed increased and the case of outermost fiber orientation of 90° was same as the experiment. The error rate of the experiment contrast simulation showed that the outermost fiber orientation is 0°, the structural member with interface of 7 was the highest with –28%, and the others showed the error rate ranging from -4% to 8%.