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학위논문 동서

AFRP/Aluminum 하이브리드 複合材料의 靜的 및 披勞 特性에 관한 硏究

박원조

부산: 동아대학교 1994. -

94장: 삽도; 27cm. -

학위논문(박사)- 동아대학교 대학원 기계공학과 `95년2월

영문초록 : A new hybrid composite (APAL; Aramid Patched ALuminum alloy), consisting of a Al2024-T3 aluminum alloy plate sandwiched between two aramid /epoxy laminates(HK 285/RS 1222), was developed. The static strength, faigue life and fatigue crack growth characteristics of the APAL were investigated. The effect of number of AFRP laminates on the staic strength was examined and so it could be calculated with theoretical method, and the fatigue strength was improved and the effect of lay-up method on it, and the fatigue crack growth rate was remarkedly delayed and a retardation mechanism was made dear and so a model of retardation mechanism was proposed. The results were as follows; 1. Static strength of APAL were proportional to number of AFRP laminate, theoretical strength by law of mixture adapting both tensile strengths well agreed with experimental strength. 2. Interlaminar shear strength of interface between Al 2024-T3 and AFRP was lower in case of longer lap length, and the value of 1 ply was higher than the value of 2 ply. 3. Fatigue life of APAL was remarkedly increased compared to that of Al 2024-T3. Fatigue life of APAL 0/90-DS-2P Was δ_(f)≒200 MPa and that of Al 2024-T3 was δ_(f)≒130 MPa, so the value of APAL went up by 55% compared to that of Al 2024-T3. In addition, the effect of number of laminate on fatigue life was little in this study. 4. Fracture life of APAL was great increased in comparison to that of Al 2024-T3. The cycle number of APAL 0/90-DS-2P corresponding crack length a=65mm was increased by 5 time in R=0.2 and 10 times in R=0.5 in comparison to that Al 2024-T3. 5. Fatigue crack growth rate of APAL was remarkedly decreased compared to Al 2024-T3, a peculiar behavior was seen that fatigue crack growth rate was decreased as ΔK was increased. The decreased magnitude of crack growth rate in APAL of AFRP orientation 0˚/90˚ was larger than that APAL of .AFW orientation ±45˚, and that was larger as number of laminate was increased, and that of double-side was larger than that of single-side. The decreased magnitude in R=0.5 was larger than that in R=0.2. 6. It was found that the reason of the decrease of fatigue crack growth rate was a crack bridging mechanism by undamaged fibers in wake of crack on AFRP laminates, and so a model of the crack bridging mechanism was proposed. 7. The effect of crack bridging was largely increased in early stage of experiment but that was made constant after ΔK≒20 MPa*√m. The ΔK_(eff) would be proposed as parameter for quantitative estimate of the effect of crack bridging. ΔK_(eff)=(ΔCOD_(ARAL)/ΔCOD_(Al))ΔK In consequence of above results, a new method of repair and reinforcement for defected and weak parts have been proposed by AFRP bonding on surface of aircraft, a theoretical foundation have been consolidated for development of a hybrid composite that they say a materials for next generation of aircraft. A mechanism of retardation of fatigue crack growth rate would be used to prodict fatigue life of structures for its reliability.

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