• 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.

• 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.

• International Journal of Automotive Technology
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• v.3 no.4
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• pp.157-163
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• 2002

It is well recognized that the ultrasonic method is one of the most common and reliable nondestructive testing (NDT) methods for the quantitative estimation of defects in welded structures. However, NDT techniques applying for adhesively bonded joints have not been clearly established yet. In this paper, the detection of interface crack by the ultrasonic method was applied for the measurement of interfacial crack length in the adhesively bonded joints of double-cantilever beam (DCB). An optimal condition of transmission coefficients and experimental accuracy by the ultrasonic method in the adhesively bonded joints have been investigated and discussed. The experimental values are in good agreement with the computed results by boundary element method (BEM) and Ripling's equation.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.6 s.177
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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.

• 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.

• 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.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.3
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• pp.421-426
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• 2007

This study was analyzed dynamically by finite element method about the results of experiments which the double cantilever beam specimens with two kinds of materials were applied by impact load. And they were compared with each other as the simulation data applied onto impact velocities of 6.4 and 18.47 m/s. The crack energy release rate, force and displacement of block were calculated numerically by computer. As the numerical simulation data of specimen analyzed in this study approached the experimental data, the inspection of this specimen model suggested in this paper could be reasonable for the numerical simulation.

• 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.

• 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.

• 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.