• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1039-1044
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• 2003

Adhesive-bonded joints are widely used in the industry. Recently aircraft applications of adhesive bonding joints have been increased extensively in automobile and air industry. Because adhesives which are available for structural applications have been developed a lot and understanding of adhesive bonding has been improved so much. In this study, as the fundamental research of design of adhesive bonding joints, this study considers specimen shape are affect strength and durability of Al/Polymer lap joints. In this research, cross head speed difference were concerned to evaluate their effects on the adhesive strength. Cross head speed makes a change 0.05mm/min, 0.5mm/min, 5mm/min. The result is load-displacement diagram showed brittleness fracture tendency. Fracture tendency that is shown enough on stress distribution of trigonal single lap joint and trigonal edged single lap joint occur the inside of adhesive.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.05a
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• pp.172-175
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• 2001

The co-cured Joining method, which is regarded as an adhesively bonded Joining method, is an efficient joining technique because both curing and bonding processes for the composite structures can be achieved simultaneously. It requires neither surface treatment onto the composite adherend nor an additional adhesive joining process because the excess resin, which is extracted from composite materials during consolidation, accomplishes the co-cured Joining process. Since the adhesive of the co-cured joint is the same material as the resin of the composite adherend, the analysis and design of the co-cured joint for composite structures are simpler than those of an adhesively bonded joint, which uses an additional adhesive. In this paper, effects of the manufacturing parameters, namely surface roughness, stacking sequence of the composite adherend, and manufacturing pressure in the autoclave during curing process, on the tensile load bearing capacity of the co-cured single lap joint will be experimentally investigated.

• Composites Research
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• v.18 no.1
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• pp.1-9
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• 2005

A methodology is presented for the failure prediction of composite single-lap bonded joints considering both of composite adherend failure and bondline failure. An elastic-perfectly plastic model of adhesive and a delamination failure criterion are used in the methodology. The failure predictions have been performed using finite element method and the proposed methodology. The failure prediction results such as failure mode and strength have very good agreements with the test results of joint specimens with various bonding methods and parameters. The influence of variations in the effective strength (that is, adhesion performance) and plastic behavior of adhesive on the failure characteristics of composite bonded Joints are investigated numerically. The numerical results show that optimal joint strength is archived when adhesive and delamination failure occur in the same time.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.3
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• pp.157-164
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• 2003

The pulse-echo method is one of the most widely used ultrasonic techniques for application of nondestructive evaluation. Particularly, quantitative nondestructive evaluation of defects has been considered more important to assure the reliability and the safety of structure. Frequency energy in adhesive joints is based on the ultrasonic wave analysis. The attenuation coefficient upon wave amplitude and the frequency energy that is expressed in the term of wave pressure amplitude were utilized for the primary wave experiment. By means of a control experiment, it was confirmed that the variation of the frequency energy in adhesive joints depends on transition by stress variation. In this paper, the ultrasonic characteristics were measured for single lap joint and Double Cantilever Beam specimen with different fracture modes that was subjected to stress. Consequently, the data that was obtained from the adhesive specimen was analytically compared to the fracture mechanics parameter

• Composites Research
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• v.16 no.4
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• pp.51-58
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• 2003

Since the reliability of adhesively bonded joints is much dependent on the curing status of thermosetting adhesive, the on-line cure monitoring during the cure of adhesively joints could improve the quality of adhesively bonded joints. In this work, the dielectric method which measures the dissipation factor of the adhesive during the cure of joints and converts it into the degree of cure of the adhesive was devised. The relation between the dissipation factor and the degree of cure of adhesive was investigated, which could eliminate the temperature effect on the dissipation factor that is a strong function of the degree of cure and temperature of adhesive. From the investigation, it was found that the dissipation factor showed a trend similar to the cure rate of the adhesive.

• International Journal of Korean Welding Society
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• v.4 no.1
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• pp.53-60
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• 2004

Adhesive-bonded joints are widely used in the industry. Recently, applications of adhesive bonding joints have been increased extensively in automobile and aircraft industry. The strength of adhesive joints is influenced by the surface roughness, adhesive shape, stress distribution, and etc. However, the magnitude of the influence has not yet been clarified because of the complexity of the phenomena. In this study, as the fundamental research of adhesive bonding joints, the effects of adhesive shape and loading speed on bonding strength properties and durability of aluminum to polycarbonate single-lap joints were studied. To evaluate the effect of adhesive shape, several modified shapes were used, and loading speeds were varied from 0.05 to 5mm/min. As a result, the load distribution showed a brittle fracture tendency. The trigonal edged single lap and bevelled lap joints showed the higher strength than the plain single lap, trigonal single lap, joggle lap and double lap joints in same adhesive area. The fractures of trigonal single lap and trigonal edged single lap joints that had the higher strength level were shown as the mixture type of the cohesive and interfacial-failure, mostly joggle lap joints that had the lower strength level were shown as the adhesive-failure.

• Journal of Welding and Joining
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• v.21 no.5
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• pp.555-560
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• 2003

In automobile industry, it is necessary to reduce the weight from the view point of energy and environmental problems in these days. One of the ways for weight reduction is using adhesive aluminum structures. In this study, ultrasonic signals reflected from the adhesively bonded joint layer are used to evaluate the adhesively bonded joints. FFT is performed to determine bond-layer parameters such as effective thickness and frequency for adhesively bonded joint Al 6061 plates in comparison with the measured and theoretical ratios. And the parameters of ultrasonic wave and the J-integral are investigated to evaluate the adhesively bonded joint strength by DCB specimens.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.796-801
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• 2007

The optical performance of the mirror for satellite camera is highly dependent on the adhesive properties between the mirror and its support. In order to design a mirror with high optical performance, the mechanical properties of adhesives should be well defined. In this research, the mechanical properties of three kinds of space adhesives are studied. In case of the materials which show nearly incompressible behavior such as space adhesives, it is important to measure shear modulus which governs deviatoric stress components. Shear moduli of the adhesives are determined by using single lap adhesively bonded joint. For the shear tests, several points have been selected from $-20^{\circ}C$ to $50^{\circ}C$ which is operating temperature range of the adhesive. The shear modulus of each adhesive is expressed as a function of temperature. Characteristics of the adhesives are discussed regarding their temperature sensitivity. The analysis results of RMS wavefront error w.r.t shear modulus are presented.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.196-201
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• 2004

Adhesive joints have been widely used for fastening thin adherends because they can distribute the load over a larger area than mechanical joints, require no hole, add very little weight to the structure and have superior fatigue resistance. However, the fatigue characteristics of adhesive joints are much affected by applied pressure during curing operation because actual curing temperature is changed by applied pressure and the adhesion characteristics of adhesives are very sensitive to manufacturing conditions. In this study, cure monitoring and torsional fatigue tests of adhesive joints with an epoxy adhesive were performed in order to investigate the effects of the applied pressure during curing operation. From the experiments, it was found that the actual curing temperature increased as the applied pressure increased, which increased residual thermal stress in the adhesive layer. Therefore, the fatigue life decreased as the applied pressure increased because the mean stress during fatigue tests increased due to the residual thermal stress.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.11
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• pp.1115-1122
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• 2010

The main objective of this study is to experimentally investigate the effect of adhesive thickness and environmental conditions on the failure and strength of sandwich-to-laminate bonded joints. Three different adhesive thicknesses (t=0.2, 2 and 4 mm) and two different environmental conditions were considered. Environmental conditions include the RTD(room temperature and dry condition) and ETW(elevated temperature and wet condition). Test results show as the adhesive thickness increases from 0.2 mm to 2 and 4 mm, the joint strength decreases 16 and 30%, respectively. Regarding the effect of environmental conditions, except for one case, the joint strength in the ETW conditions turned out to be 12% higher than those in the RTD conditions. In the joints with adhesive thickness of 0.2 mm, remarkable difference from RTD condition was not found.