• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.34 no.4
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• pp.450-456
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• 1998

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.40 no.4
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• pp.328-336
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• 2004

This paper describes the effect of loading rate, specimen geometries and material properties for ModeⅠ and Mode Ⅱ interlaminar fracture toughness of hybrid composite by using double cantilever beam (DCB) and end notched flexure (ENF) specimen. In the range of loading rate 0.2~20mm/min, there is found to be no significant effect of loading rate with the value of critical energy release rate (Gc).The value of Gc for variation of initial crack length are nearly similar values when material properties are CF/CF and GF/GF, however, the value of Gc are highest with the increasing intial crack length at CF/GF. The SEM photographs show good fiber distribution and interfacial bonding of hybrid composites when the moulding is the CF/GF.

• Korean Journal of Materials Research
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• v.5 no.8
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• pp.979-987
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• 1995

This study has been investigated the Influence of layer thickness on the mechanical properties of cross laminated carbon fiber/epoxy composites. And also the difference of mechanical properties between cross laminated composites of unidirectional prepreg and fabric prepreg has been investigated. Experimental results are showed that the Interlamina Shear Strength(ILSS) of cross laminated carbon fiber/epoxy composites decreased with increasing thickness of unit ply and the decree of delamination in the laminated composites increased as ILSS decreased. Fracture toughness and impact values were found to increase as delamination occurs to some extent in the laminated composites. It Is also shown thats mechanical properties of cross laminates from unidirectional prepreg were better than those of cross laminates from fabric prepreg.

• Journal of the KSME
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• v.31 no.3
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• pp.236-243
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• 1991

운전상태 II의 여러 가지 각종 파괴사고의 원인을 한 두가지인 원인으로 명확하게 구분 할 수는 없다. 여러 가지의 복잡한 원인과 조건들이 복합적으로 작용하여 대. 소형 구조물의 안전성. 건전성이 위협받는 경우가 대부분일 것이다. 여기에서는 원자로의 건전성 평가에 파괴역학의 이론. 개념 등을 어떻게 응용하는가를 간단하게 기술하였다. 여기에서 논의된 사항들뿐만 아니라 소형시험편을 사용하여 정확한 파괴인성치를 측정하는 방법론이라든지, 급속히 발달되고 있는 전자장비들을 어떻게 우리들의 파괴역학적인 개념들과 접목시켜서 건전성, 안전성을 평가. 유지 하는데 이용할 것인가 등의 방법론들의 개발. 연구되어야 하겠다.

• Journal of the KSME
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• v.30 no.2
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• pp.107-114
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• 1990

(1) Cr-Mo-V 합금강 로우터재료는 사용도중 템퍼 취화된다. 템퍼취화된 소재는 취성제거처리 혹 은 재열처리를 하여 취성을 감소시킬 수 있다. (2) 축의 신뢰도를 파괴역학 원리를 적용하여 계산하였으며 템퍼 취화된 소재는 파손 위험성이 있으나 열처리 된 소재는 취성파괴 및 고 사이클 하중에 의한 피로균열 성장에 대해서 안전성 이 충분하다는 결론을 얻을 수 있다. (3) 샬피 V-노치 충격치 (CVN)와 파괴인성치(K$_{tc}$ )의 관계식을 취성재료에도 적용할 수 있 는가의 여부에 대해서는 많은 조사가 필요하다. (4) 취성소재의 피로균열 개시값$\Delta$ $K_{th}$을 알고 있으면 취송소재로 제조된 구조물의 파괴역학적인 해석을 하는데 도움을 줄 수 있다.

• Journal of the KSME
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• v.31 no.3
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• pp.261-266
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• 1991

원자력발전소 배관에 대한 일반적인 파단전누설(LBB)개념 적용절차 및 해석 방법에 대해 간단히 기술하였다. 그러나 LBB해석방법은 배관의 크기 및 작용하중의 상태에 따라 많은 차이가 있 으므로 보다 많은 배관에 LBB개념을 적용하여 설계하기 위해서는 합리적인 해석방법의 마련, 배관재질의 파괴인성치 향상 및 원자력발전소의 운전조건 개선 등을 위한 계속적인 노력이 필요 하리라고 판단된다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.3
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• pp.936-943
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• 1991

• Journal of the Korean Society for Nondestructive Testing
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• v.18 no.4
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• pp.278-291
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• 1998

Fracture process of continuous fiber reinforced composites is very complex because various fracture mechanisms such as matrix cracking, debonding, delamination and fiber breaking occur simultaneously during crack growth. If fibers cause crack bridging during crack growth, the stable crack growth and unstable crack growth appear repeatedly. Therefore, it is very difficult to exactly determine tile starting point of crack growth and the fracture toughness at the critical crack length in composites. In this research, fracture toughness test for CFRP was accomplished by using acoustic emission(AE) and recording of tile fracture process in real time by video-microscope. The starting point of crack growth, pop-in point and the point of unstable crack growth can be exactly determined. Each fracture mechanism can be classified by analyzing the fracture process through AE and video-microscope. The more reliable method ior the fracture toughness measurement of composite materials was proposed by using the combination of R-curve method, AE and video microscope.

• Journal of Advanced Marine Engineering and Technology
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• v.25 no.5
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• pp.1140-1147
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• 2001

This paper describes the effect of various molding pressure for Mode I. Mode II interlaminar fracture toughness of carbon fiber reinforced plastic composites by using double cantilever beam(DCB), end notched flexure(ENF) and end loaded split(ELS) Specimen. The value of $G_{IC}$, $G_{IIC}$ as a function of various molding pressure is almost same at 307, 431, 585 kPa, however it shows highest value under 307kPa molding pressure, The SEM photographs show good fiber distribution and interfacial bonding of composites when the molding pressure is the 307kPa.

• Journal of Power System Engineering
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• v.4 no.3
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• pp.48-54
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• 2000

This paper describes the effect of molding pressure, specimen geometries for Mixed Mode I/II interlaminar fracture toughness of carbon fiber reinforced plastic composites by using asymmetrical double cantilever beam(ADCB) specimen. The value of $G_{I/IIC}$ as a function of various molding pressure is almost same at 307, 431, 585 kPa. However it shows the highest value under 307 kPa molding pressure. The effect of $G_{I/IIC}$ due to the change of initial crack length of ADCB specimen was almost negligible in this study. It turns out that the condition for mix mode quasi-static crack growth in ADCB specimen is the ratio of the crack length to that of the specimen, i.e., ${\alpha}/L<0.4$.