탄소섬유강화 복합재 적층쉘의 관통특성에 관한 연구

Abstract

Carbon fiber reinforced plastics, among the advanced composite material watched with keen interests today, is widely used as structural components requiring light weight property because of its high specific strength as well as high specific rigidity. However, this material has a drawback of weakness against a transverse impact loading acting toward the direction of its stacked thickness, which requires different design parameters other than those used for general metal products in actual application. Therefore, to utilize a laminated composite material for structural component, impact behaviors, damage analysis and penetration characteristics against transverse impact loading must be studied essentially in the first place, and impact and penetration experiments for laminated composite material shell curved to actual body shape of the structural component must be conducted in advance to any others. In connection with this point of view, this study utilized specimen of laminated composite material shell having certain radius of curvature considering actual structural component made of laminated CFRP composite material. Radii of curvature generally found in aircraft wings were adopted for the specimens; i.e. 100mm., 150 mm., 200 mm. and ∞respectively. Specimens were prepared in autoclave after undergoing vacuum pack forming process on lamination stacked in proper sequences. They were, then, cut into a size of 100 × 140 mm by precision automatic cutter fitted with diamond wheel. Penetration experiment was conducted by measuring time of penetration of steel ball between two (2) points where ballistic-screen sensors were attached on front and reverse side of the specimen with the air gun under air pressure that is adjusted by the pressure gauge attached to. Critical penetration energy was found by measuring kinetic energies of the steel ball before and after the penetration. In order to identify crack pattern and penetration mode generated inside the specimen after the experimental penetration, this study used digitalized optical microscope. Through this study, therefore, penetration characteristics by changes in number of layers, by different stacking sequences as well as penetration mode against inclined impact have been observed.