• Title, Summary, Keyword: Double cantilever beam(DCB)

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Analysis of Bridging Stress Effect of Polycrystalline Aluminas Using Double Cantilever Beam Method II. Development of Double Cantilever Beam Method Considering Bridging Effect (Double Cantilever Beam 방법을 이용한 다결정 알루미나의 Bridging 응력효과 해서 II. Bridging 효과를 고려한 Double cantilever Beam 분석방법의 정립)

  • 손기선;이성학;백성기
    • Journal of the Korean Ceramic Society
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    • v.33 no.5
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    • pp.590-601
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    • 1996
  • This study aims at developing the double cantilever beam (DCB) method in order to calculate the bridging stress distribution in polycrystalline aluminas with different grain sizes. In the already existing DCB methods the measured crack opening displacement (COD) in coarse-grained aluminas deviates generally from the calcula-ted one because of the grain-interface bridging in the crack wake. In the current DBC method developed in the present study the effect of the bridging stress was considered in the DCB analysis. whereas the only effect of applied point-loading at the end of DCB specimen was taken into account in the existing DCB analysis The crack closure due to bridging stress was calculated using the power-law relation and the theoretical model developed in Part I of the present paper as bridging stress function and then compared analytically. The limitations of the current DCB methods such as specimen dimensions applied loads and elastic modulus were discussed in detail to provide a reliability of the newly developed DCB analysis for the bridging stress distribu-tion in polycrystalline aluminas.

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Evaluation Method of Adhesive Fracture Toughness Based on Double Cantilever Beam (DCB) Tests Including Residual Thermal Stresses

  • Yokozeki, Tomohiro;Ogasawara, Toshio
    • Advanced Composite Materials
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    • v.17 no.3
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    • pp.301-317
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    • 2008
  • The energy release rate associated with crack growth in adhesive double cantilever beam (DCB) specimens, including the effect of residual stresses, was formulated using beam theory. Because of the rotation of the asymmetric arms in the adhesive DCB specimens due to temperature change, it is necessary to correct the evaluated fracture toughness of the DCB specimens, specifically in the case of a large temperature change. This study shows that the difference between the true toughness and an apparent toughness due to the consequence of ignoring residual stresses can be calculated for a given specimen geometry and thermo-mechanical properties (e.g. coefficient of thermal expansion). The calculated difference in the energy release rates based on the present correction method is compared with that from FEM in order to verify the present correction method. The residual stress effects on the evaluation of the adhesive fracture toughness are discussed.

Analyses of Stress Intensity Factors and Evaluation of Fracture Toughness in Adhesively Bonded DCB Joints (DCB 접착이음에 대한 응력세기계수의 해석 및 파괴인성의 평가)

  • Jeong, Nam-Yong;Lee, Myeong-Dae;Gang, Sam-Geun
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.24 no.6
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    • pp.1547-1556
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    • 2000
  • In this paper, an evaluation method of fracture toughness to apply interfacial fracture mechanics was investigated in adhesively bonded double-cantilever beam (DCB) joints. Four types of adhesively bonded DCB joints with an interface crack were prepared for analyses of the stress intensity factors using boundary element method(BEM) and the fracture toughness test. From the results of BEM analysis and fracture toughness experiments, it is found that the stress intensity factor, K1 is a parameter driving the fracture of adhesively bonded joints. Also, the evaluation method of fracture toughness by separated stress intensity factors of mixed mode cracks was proposed and the influences of mode components for its fracture toughness are investigated in adhesively bonded DCB joints.

Study on Structural Analysis of DCB Specimen Bonded with Aluminum Foam Composite (알루미늄 폼 복합재료로 된 접합된 DCB 시험편의 구조 해석에 관한 연구)

  • Choi, Hae-Kyu;Kim, Sei-Hwan;Cho, Jae-Ung
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.13 no.4
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    • pp.1488-1495
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    • 2012
  • In this study, the fracture behaviour of DCB(double cantilever beam) specimen with aluminum foam composite materials is analyzed by simulation. The used model is 3D configuration on the basis of British industrial standard and ISO international standard. As the thickness of model is increased, the length of propagated crack is increased and the load becomes higher. The analysis result obtained by this study can be applied at the practical composite structure bonded with aluminum foam materials. The fracture behaviour is analyzed and the mechanical property can be understood.

Finite Element Analysis and Validation for Mode I Interlaminar Fracture Behavior of Woven Fabric Composite for a Train Carbody Using CZM(Cohesive Zone Model) (CZM(Cohesive Zone Model)을 이용한 철도차량용 직물 복합재의 모우드 I 층간파괴의 해석적 연구)

  • Kim, Seung-Chul;Kim, Jung-Seol;Yoon, Hyuk-Jin;Seo, Seung-Il
    • Journal of the Korean Society for Railway
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    • v.12 no.5
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    • pp.719-724
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    • 2009
  • In this study, DCB(double cantilever beam) specimens of woven fabric carbon/epoxy and glass/epoxy were manufactured and mode I fracture toughness of specimen was measured according to ASTM 5528-01. And FE analysis was conducted in the same condition and evaluated the behavior of delamination analytically. Mode I fracture toughness measured by test was $845.7\;J/m^2$ in the case carbon/epoxy and that of glass/epoxy was $1,042\;J/m^2$. FE analysis was conducted using cohesive elements for adhesive layer and applied measured fracture toughness. To verify the result of analysis, the reaction force measured at the end of specimen and that calculated by Timoshenko beam theory were compared. The numerical results show good agreements with the measured one.

The Effect of the Core-shell Structured Meta-aramid/Epoxy Nanofiber Mats on Interfacial Bonding Strength with an Epoxy Adhesive in Cryogenic Environments (극저온 환경에서 에폭시 접착제의 물성 향상을 위한 나노 보강재의 표면 개질에 관한 연구)

  • Oh, Hyun Ju;Kim, Seong Su
    • Composites Research
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    • v.26 no.2
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    • pp.129-134
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    • 2013
  • The strength of adhesive joints employed in composite structures under cryogenic environments, such as LNG tanks, is affected by thermal residual stress generated from the large temperature difference between the bonding process and the operating temperature. Aramid fibers are noted for their low coefficient of thermal expansion (CTE) and have been used to control the CTE of thermosetting resins. However, aramid composites exhibit poor adhesion between the fibers and the resin because the aramid fibers are chemically inert and contain insufficient functional groups. In this work, electrospun meta-aramid nanofiber-reinforced epoxy adhesive was fabricated to improve the interfacial bonding between the adhesive and the fibers under cryogenic temperatures. The CTE of the nanofiber-reinforced adhesives were measured, and the effect on the adhesion strength was investigated at single-lap joints under cryogenic temperatures. The fracture toughness of the adhesive joints was measured using a Double Cantilever Beam (DCB) test.

The Characteristics for Mode I Interlaminar and Intralaminar Fractures of Cross-Ply Carbon/Epoxy Composite Laminates Based on Energy Release Rate (변형률 에너지 해방률에 기반한 Carbon/Epoxy 직교적층판의 모드 I 층간 및 층내 파괴 특성 분석)

  • Kang, Min-Song;Jeon, Min-Hyeok;Kim, In-Gul;Woo, Kyeong-Sik
    • Composites Research
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    • v.32 no.1
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    • pp.6-12
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    • 2019
  • This paper describes the characteristics for mode I interlaminar and intralaminar fractures of cross-ply carbon/epoxy composite laminates. We obtained mode I interlaminar fracture toughness and mode I intralaminar fracture toughness based on energy release rate and Finite Element Analysis (FEA). For this purpose, the Double-Cantilever Beam (DCB) test and FEA were performed for cross-ply DCB specimens. Also, the behavior of load-displacement curve at the interlaminar and intralaminar crack was analyzed. The results show that mode I intralaminar fracture toughness was lower than mode I interlaminar fracture toughness in the cross-ply DCB specimen.

Comparison of Quantitative Interfacial Adhesion Energy Measurement Method between Copper RDL and WPR Dielectric Interface for FOWLP Applications (FOWLP 적용을 위한 Cu 재배선과 WPR 절연층 계면의 정량적 계면접착에너지 측정방법 비교 평가)

  • Kim, Gahui;Lee, Jina;Park, Se-hoon;Kang, Sumin;Kim, Taek-Soo;Park, Young-Bae
    • Journal of the Microelectronics and Packaging Society
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    • v.25 no.2
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    • pp.41-48
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    • 2018
  • The quantitative interfacial adhesion energy measurement method of copper redistribution layer and WPR dielectric interface were investigated using $90^{\circ}$ peel test, 4-point bending test, double cantilever beam (DCB) measurement for FOWLP Applications. Measured interfacial adhesion energy values of all three methods were higher than $5J/m^2$, which is considered as a minimum criterion for reliable Cu/low-k integration with CMP processes without delamination. Measured energy values increase with increasing phase angle, that is, in order of DCB, 4-point bending test, and $90^{\circ}$ peel test due to increasing roughness-related shielding and plastic energy dissipation effects, which match well interfacial fracture mechanics theory. Considering adhesion specimen preparation process, phase angle, measurement accuracy and bonding energy levels, both DCB and 4-point bending test methods are recommended for quantitative adhesion energy measurement of RDL interface depending on the real application situations.

Study on Fatigue Analysis of DCB Specimen Bonded (접착제로 접합된 DCB 시험편의 피로 해석에 관한 연구)

  • Choi, Hae-Kyu;Hong, Soon-Jik;Kim, Sei-Hwan;Cho, Jae-Ung
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.13 no.7
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    • pp.2865-2871
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    • 2012
  • In this study, the fracture behaviour of DCB(double cantilever beam) specimen with aluminum foam composite materials is analyzed by simulation. By comparing the analysis results with two models of 25 mm and 40 mm, the model with thickness of 25 mm is weaker than 40 mm at fatigue life and damage. Two models are unfavorable at 'SAE Transmission' in case of nonuniform fatigue load and rainflow matrices are weakest at 'SAE Bracket history'. In damage matrices, the model with 25 mm of thickness is weaker than the model with 40 mm of thickness but the model with 40 mm of thickness relative damage possibility is higher than in case of 25 mm. As two models are safest at 'SAE Transmission', the relative damage becomes the lowest value from 1.1 to 1.8 %. The mechanical property can be investigated by applying these analyses results with the real composite structure bonded with adhesive and analyzing fracture behaviour.

A Study on Mode I Interlaminar Fracture Toughness of Foam Core Sandwich Structures

  • Sohn, Se-Won;Kwon, Dong-Ahn;Hong, Sung-Hee
    • International Journal of Precision Engineering and Manufacturing
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    • v.2 no.3
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    • pp.47-53
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    • 2001
  • This paper investigates the characteristics of interlaminar fracture toughness of foam core sandwich structures under opening mode by using the double cantilever beam (DCB) specimens which are Carbon/Epoxy and foam core composites. Instead of using a DCB specimen of symmetric geometry, a non-symmetric DCB specimen was used to calculate the interlaminar fracture toughness. Three approaches for calculating the energy release rate(G$\sub$IC/) were used and fracture toughness of foam core sandwich structures made by autoclave, vacuum bagging and hotpress were compared. Experiment, analysis using nonlinear beam bending theory, and numerical work by FEM methods were performed. Bonding surface compensation and equivalent moment of inertia were used to calculate the energy release rate in nonlinear analytical work. Conclusions of experimental, nonlinear analytical and FEM methods were compared. It is, also, shown that the vacuum bagging forming can substitute the method of autoclave without serious loss of Mode I energy release rate(G$\sub$I/).

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