• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2004년도 춘계학술발표대회 논문집
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• pp.202-205
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• 2004

A numerical method is presented to determine the characteristic lengths for the failure analysis of composite joints without characteristic length tests. In the conventional methods, compressive characteristic length was determined from the result of a combined bearing test and finite element analysis. The present study, however, shows that the same compressive characteristic length can be obtained by numerical calculation without the bearing test. A new method to define the tensile characteristic length is also introduced so that the tensile characteristic length is numerically determined without the tensile test. Failure loads based on the numerically calculated characteristic lengths are validated by the test results for composite joints

• 한국안전학회지
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• 제18권4호
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• pp.8-15
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• 2003

A study on predicting the joint strength of mechanically fastened woven glass/epoxy composite has been performed. An experimental and numerical study were carried out to determine the characteristic length and joint strength of composite joint. The characteristic lengths for tension and compression were determined from the tensile and compressive test with a hole respectively. The characteristic lengths were evaluated by applying the point stress failure criterion to a specimen containing a hole at the center subjected to tensile loading and a specimen containing a half circular notch at the center subjected to compressive load. The joint strength was evaluated by the Tsai-Wu and Yamada-Sun failure criterion on the characteristic curve. The predicted results of the joint strength were compared with experimental results.

• 대한기계학회논문집A
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• 제33권4호
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• pp.360-365
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• 2009

In the manufacture of CFRP(Carbon Fiber Reinforced Polymer Composite) composite structures, various independent components join by bolts and pins. Holes for bolts and pins have an effect on the failure strength of such structures, because those act as notches in structures. The failure characteristic of such structures are different from those of plain plate subject to remote load. In this paper, tensile properties of woven CFRP composite plates with laminates of $0^{\circ}$, $30^{\circ}$ and $45^{\circ}$ were obtained according to ASTM D 3039. By using obtained tensile failure strength and Tan-Cheng failure criterion, tensile failure strength of CFRP laminate with arbitrary fiber angle were evaluated. Also, the degradation of tensile properties by center hole(${\phi}10mm$) with a remote load was evaluated and the failure strengths were applied to Tan's failure criterion, similarly.

• 한국정밀공학회지
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• 제26권7호
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• pp.99-104
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• 2009

Creep characteristic is an important failure mechanism when evaluating engineering materials that are soft as polymers or used as mechanical elements at high temperatures. One of the popular thermo-elastic plastics, Polyethylene(PE) which is used broadly for engineering purposes, as it has good properties and merits compared to other plastics, was studied for creep characteristic at various level of stresses and temperatures. From the experimental results, the creep limit of PE at room temperature is 75% of tensile strength. Also the creep limits decreased exponentially as the temperatures increased, up to 50% of the melting point. Also the secondary stage among the three creep stages was nonexistent nor was there any rupture failure which occurred for many metals.

• 한국정밀공학회지
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• 제27권9호
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• pp.78-85
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• 2010

Creep characteristic is an important failure mechanism when evaluating engineering materials that are soft material as polymers or used as mechanical elements at high temperatures. One of the popular thermo-elastic polymers, Polycarbonate(PC) which is used broadly for engineering polymer, as it has excellent mechanical and thermal properties compared to other polymers, was studied for creep characteristic at various level of stresses and temperatures. From the experimental results, the creep limit of PC at room temperature is 85 % of tensile strength. which is higher than PE (75%)at room temperature. Also the creep limits decreased exponentially as the temperatures increased, up to 50 % of the melting point($267^{\circ}C$). Also the first and third stage among the three creep stages was non-existent nor was there any rupture failure which occurred for many metals.

• 한국정밀공학회지
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• 제28권12호
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• pp.1403-1410
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• 2011

Creep characteristic is an important failure mechanism when evaluating engineering materials that are soft material as polymers or used as mechanical elements at high temperatures. One of the popular thermo-elastic polymers, Polymethyl methacrylate(PMMA) which is used broadly for engineering polymer, as it has excellent mechanical and thermal properties compared to other polymers, was studied for creep characteristic at various level of stresses and temperatures. From the experimental results, the creep limit of PMMA at room temperature is 85 % of tensile strength. which is higher than that of PE (75%)at room temperature. Also the creep limits decreased to nil linearly as the temperatures increased, up to $120^{\circ}C$ of the melting point($267^{\circ}C$). Also the first and third stage among the three creep stages were non-existent nor were there any rupture failure which occurred for many metals at high temperatures.

• Journal of the Korean Wood Science and Technology
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• 제26권2호
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• pp.16-23
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• 1998

This paper examines the effects of specimen length and grade on the strength and stiffness properties of structural timber of radiata pine. The tensile strength and modulus of elasticity of 1,902 machine-graded boards with 3.15- and 1.62-m clear span lengths, were determined using a horizontal tension test machine. The mean failure and characteristic stress values for tensile strength show an extremely high dependency on test specimen length. The mean and characteristic values of both modulus of elasticity and tensile strength show significant dependency on machine stress grades.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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• pp.293-298
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• 2003

In this study, tensile adhesive strength(TAS) test was carreid out for evaluated the effects of temperature conditions(-20, -10, 5, 20, 30, $40^{\circ}C$) on the tensile adhesive characteristics about six waterproofing membranes which were commercially used in bridge decks. And, failure appeariences of waterproofing systems in each temperature were investigated and observed the sawing surfaces of waterproofing systems for whether or not damaged of waterproofing membranes. TAS test results were increased when test temperature was decrease in all waterproofing membrane. The type of failure was ductile in $30^{\circ}C$ and $40^{\circ}C$, but brittle failure below $20^{\circ}C$. This results were shown that if temperature above $30^{\circ}C$ is continued for a long time, waterproofing material will be damaged by softening and a part of membranes were damaged by hot aggregate in SMA. So we will consider the type of asphalt for choice of the waterproofing membranes.

• International Journal of Safety
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• 제2권1호
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• pp.23-27
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• 2003

Recently, continuous fiber reinforced ceramic composite(CFCC) has attracted attention to a number of engineers because of its significant benefit for several industrial area. This work was conducted to provide a basic characteristic of CFCC for tensile loading condition. The numerical analysis by general purpose finite element program was accomplished and compared with an experimental tensile test. The stress strain curves were expressed well by the numerical analysis and the first matrix cracking stress was in accordance with that of the experimental result. Moreover, fracture pattern was shown by kill command graphically.

• 대한기계학회논문집
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• 제16권7호
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• pp.1285-1293
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• 1992

본 연구에서는 glass/epoxy 직조된 복합재료에 있어서 원공 및 판폭의 크기가 노치강도에 미치는 영향을 명확히 하고, 또한 노치강도 및 파괴조건과 위에서 언급한 특성길이와의 관계를 검토하였다.