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고무변성 에폭시 수지의 균열선단 손상역 발달과 음향 방출 특성
이덕보(Deok-Bo Lee),김현수(Hyun-Soo Kim),남기우(Ki-Woo Nam),최낙삼(Nak-Sam Choi) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.8
A damage zone around a crack tip occurred before fracturing is a significant data, which offer the toughening mechanism of a materials. The growth processing of damage zone in the vicinity of crack tip for rubber-modified epoxy resin is investigated using an acoustic emission(AE) analysis system. The volume fractions of rubber(CTBN 1300×8) in rubber-modified epoxy resin are 5% and 15%. The fracture toughness(K<SUB>IC</SUB>) and the fracture energy(G<SUB>IC</SUB>) were measured using single notch 3 point bending specimens. The damage zone and rubber particles distributed around the crack tip of damaged specimens were observed by a polarization microscope and an atomic force microscope(AFM). The damage zone around crack tip of rubber-modified epoxy resin appears in 13.1% loading and develops into 57.2% loading based on 100 % fracture loading. The propagated-behavior of stable crack which initiated at 57.2% loading occurs in discontinuity. At the maximum loading, it has changed into unstable crack and the modified epoxy resin is broken
혼합모드 부하조건에 의한 고무변성 에폭시수지의 파괴거동
이덕보(Deok-Bo Lee),최낙삼(Nak-Sam Choi) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.3
Recently, structural adhesives and fiber composites have been largely used in many structural components. Rubber-modified epoxy resins are employed as adhesives and matrix materials for various engineering components. This study is focused on the relationship between fracture toughness and damage zone size around the crack tip of rubber-modified epoxy resin under mixed mode conditions. Fracture toughness(K<SUB>IC</SUB>) and fracture energy(G<SUB>C</SUB>) are evaluated using the end notched circle type(ENC) specimens. The damage zone and rubber particles distributed around the crack tip of damaged specimens are also observed by an optical microscope. It is concluded that G<SUB>C</SUB> of rubber-modified epoxy resin is closely related to the area of the damage zone. The rubber particles are deformed elliptically due to the difference in principal stresses in the case that the loading angle is 30 degree
고무 변성 에폭시 알루미늄 접합부의 계면 균열 파괴거동
이덕보(Deok-Bo Lee),최낙삼(Nak-Sam Choi),문창권(Chang-Kwon Moon),남기우(Ki-Woo Nam) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.3
Fracture mechanism of an interface crack in an adhesive joint is important from the viewpoint of the structural integrity of the adhesive joint. The rubber-modified epoxy resin is used in engineering components as adhesive. The damage zones around crack tips in adhesive joints consisting of aluminum and rubber-modified epoxy resin are compared with those around crack tips in the rubber-modified epoxy resin. Damage zones around crack tips are observed by a optical microscope and an atomic force microscope(AFM). The results show that the damage zones generated by cavitation in rubber particles in the modified epoxy resin specimen are not observed around crack tips in the adhesive joints
미소접합시험과 유한요소법을 통한 섬유/에폭시 복합재의 계면 전단강도 해석
강수근(Soo-Keun Kang),김덕재(Deok-Jae Kim),최낙삼(Nak-Sam Choi),이덕보(Deok-Bo Lee) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.3
In this study, we performed the microbond test by utilizing the microbond specimen with an epoxy micro-droplet adhered onto a carbon fiber. The interfacial shear stress distributions along the fiber/matrix interface were calculated by finite element analysis with three kinds of finite element models such as droplet model, circular model and pull-out model. Conclusions were obtained as follows. (1) Interfacial shear stress distribution showed that larger stresses were concentrated in the fiber/matrix interface for microbond test than for pull-out test. Thus, debonding at the fiber/matrix interface during microbond test was liable to occur at low load level. (2) Microbond test showed higher interfacial strength which was caused by various effects of micro-droplet geometry and size as well as stress concentration in the region contacting with the micro-vise tip.