PMC/Al2O3/PMC 판상복합재료의 3점 굽힘 변형에 의한 파괴 거동

Abstract

The three point bending behavior of a monolithic Al2O3 and PMC/Al2O3/PMC laminated composites has been investigated. The PMC/Al2O3/PMC laminated composites were fabricated by bonding two plane woven fiber reinforced polymer matrix composite(PMC) layers with 1. 2mm thickness on both surfaces of an Al2O3 plate with 3.8mm thickness. Four types of PMC/Al2O3/PMC laminated composites were fabricated using four different kinds of PMCs. i.e., Carbon(0/90)4, Carbon(+45 /-45)4, Aramid(0/90)4 and Aramid(+45 /-45)4. The fracture behavior of the PMC/Al2O3/PMC laminated composites was strongly affected by the properties of the PMCs. The three point bending process of the PMC/Al2O3/PMC laminated composites could be divided into three regimes( I, II, Ⅲ) in stress-strain curves related with the initiation and propagation of crack. In regime I, from the start point up to the first load drop, the PMC /Al2O3/PMC laminated composites deformed elastically. The first load drop was related with the crack initiation in Al2O3 layer of the PMC/Al2O3/PMC laminated composite, and the crack initiation stress in Al2O3 layer is proportional to the elastic modulus of laminated PMC. In regime II, from the first load drop up to the second load drop, the PMC layer deformed elastically and the crack was opened in Al2O3 layer. The crack propagation behavior in regime Ⅲ, from the second load drop up to the complete fracture, is dependent on the ratio of flexural strength of PMC to shear strength at the Al2O3/PMC interface. The C(0/90) /Al2O3/ C(0/90) and A(0/90) / Al2O3 / A(0/90) laminated composites, in which the laminated PMCs have higher flexural strengths, fractured by the deb