FEM을 이용한 원형단면 CFRP 구조부재의 정적 압궤 특성 연구

Abstract

The recent development of core techniques in automobiles and aerospace can be condensed into a technical advance for safety and convenience, and mechanical technology for being eco-friendly and lightweight. In this circumstance, researches for the composite material have been attracted. The CFRP has a number of advantages such as the specify strength, specify rigidity, low thermal deformation, corrosion resistance, and vibration attenuation properties, etc. CFRP has been demaned in several industries due to its strength, stiffness and light-weight. Unlike general isotropic materials, the structural characteristics of composite materials are strongly influenced by the stacking directions and sequences of composite laminates. CFRP consists of carbon fiber and matrix. Composite laminas with different characteristics, such as material properties, thickness, azimuth etc., can be stacked together to produce a very effective structure. This makes the composite laminates adapt the response in specific load conditions. In some cases, the structure has unique advantage to reduce weight and manufacturing cost. As non-linear fiber material matrix has a tough measurement for a property of CFRP precisely, it is necessary for measuring mechanical properties through experiment and measuring physical properties are required for a lot of experimental time and cost. In this study, the finite element analysis was used to predict and obtain the material properties of the carbon fibers and the resin even if the carbon fiber laminate and the number of modified external angle. It verifies the reliability in comparison with the simulation result and the real test results to predicted material properties of the carbon fibers and the resin. Conclusions obtained from this study are as follows.

1. The CFRP circular structural member was collapsed according to the different orientation angles by compounding of the 4 different modes: transverse shearing, laminar bendingm brittle fracture and local bucking.

2. When the external angle is 0°, the external fiber induces lamina bending of the inner fibers due to lamina bending, so that it has lower load value than the case where the external angle is 90°. However when the outermost angle was 90 °, the 0 ° fiber was fractured while interfering with the lamina bending to expand outside the inner 0 ° fiber, which showed the highest load value due to more fiber breakage.

3. As the number of interfaces increased to 2, 3, 6, and 7 interfaces, the load to the specimens with 2, 3, 6 interfaces increased linearly, while it decreased with the interfaces with 7 interfaces.

4. As a result of applying CFRP static collapse analysis of fiber properties and resin properties through basic experiment and basic theory, it is possible to predict through finite element analysis and proved to be effective because the error rate is about 10%.

5. The results of the finite element analysis and the experimental results according to the outermost changes were compared with the load-displacement curve and the maximum load. [02/902]S, [902/02]2, [0/90]2S, [90/0]4 specimens showed a maximum error rate of 12.93%, also 902/02]S, [02/902]2, [90/0]2S, [0/90]4 specimens also showed error rates of about 14%.

6. It was found that the reproducibility of the experimental data is required through the accuracy of the manufacturing method such as the prepreg sheet moving and storing method, cutting, laminating method and molding conditions during the production of the specimen.