• Steel and Composite Structures
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• 제25권6호
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• pp.685-692
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• 2017

In this study, the effect of various adhesively bonded composite patches on mechanical properties of notched Al-Mg alloy plates was analyzed. For this purpose firstly, the un-notched and notched specimens were fabricated from 5086 Al-Mg alloys which have been used in armor-plated military vehicles. The surface notches as a flaw were machined with circular cutting tool to form notch aspect ratio a/c=0.15 and notch-to-thickness ratios a/t=0.5 in the radial direction on the test specimens. Then, various composite patches which reinforced by glass, carbon and Kevlar fibers were bonded adhesively at elliptically surface notches. Finally, experimental measurements conducted by applying tensile static loading. The experimental results showed that repairing with composite patches with order of carbon, glass and Kevlar fibers have remarkable effect on tensile strength of the notched plate. Also the finite element models were developed using Abaqus/Explicit code to predict the tensile strength and elongation of unrepaired notched specimen and specimen repaired by carbon fiber composite patch. The comparison between numerical and experimental results showed good agreement between them and proved the accuracy of numerical modeling.

• Composites Research
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• 제31권4호
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• pp.128-132
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• 2018

Multi-material design with metals and composites can keep structural functions as well as reduce the weight of automotive parts. However, recycling of automotive parts should be considered due to the increasing emphasis on the environments and pollutions. We derived the key issues for increasing the recycling rate of automotive parts by carrying out a survey targeting representatives and workers related with automotive recycling. The core of the key issues was the separation technology of adhesively bonded metal-composite hybrid structures, so we conducted the basic research and suggested the separation technology which can easily be adopted into the recycling industries.

• Proceedings of the Korean Society For Composite Materials Conference
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• 한국복합재료학회 2000년도 춘계학술발표대회 논문집
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• pp.149-153
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• 2000

Substituting composite structures for conventional metallic structures has many advantages because of higher specific stiffness and specific strength of composite materials. In this work, one-piece propeller shafts composed of carbonfepoxy and glass/epoxy composites were designed and manufactured for a rear wheel drive automobile satisfying three design specifications, such as static torque transmission capability, torsional buckling and the fundamental natural bending frequency. Single lap adhesively bonded joint was employed to join the composite shaft and the aluminum yoke. For the optimal adhesive joining of the composite propeller shaft to the aluminum yoke, the torque transmission capability of the adhesively bonded composite shaft was calculated with respect to bonding length and yoke thickness by finite element method and compared with the experimental result. Then an optimal design method was proposed based on the failure model which incorporated the nonlinear mechanical behavior of aluminum yoke and epoxy adhesive. From the experiments and FEM analyses, it was found that the static torque transmission capability of composite propeller shaft was maximum at the critical yoke thickness, and it saturated beyond the critical length. Also, it was found that the one-piece composite propeller shaft had 40% weight saving effect compared with a two-piece steel propeller shaft.

• Proceedings of the Korean Society For Composite Materials Conference
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• 한국복합재료학회 2001년도 춘계학술발표대회 논문집
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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.

• Journal of the Korean Society for Nondestructive Testing
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• 제10권1호
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• pp.29-37
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• 1990

In this study the disbonding tests of adhesively bonded Al/Al honeycomb structures were performed by ultrasonic methods. Ultrasonic C-scan squiter method and ultrasonic surface wave attenuation measuring method were applied for the detection of skin/core disbonding. The bonding quality of Al/Al honeycomb structures could be well evaluated by properly controlled ultrasonic parameters.

• Transactions of the Korean Society of Mechanical Engineers
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• 제7권2호
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• pp.145-152
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• 1983

An adhesively bonded anisotropic structure containing a part-through crack subjected to in-plane mixed mode deformations is investigated. The problem is reduced to a pair of Fredholm integral equations of the second kind by mathematical analysis. By solving these equations numerically stress intensity factors k$_{1}$ and k$_{2}$ are presented. Two cases are considered with respect to fiber orientations. Case one is to fix the fiber orientations of sound plate bonded to cracked plate with various fiber orientations. The other is to vary fiber orientations for both plates. As boundary conditions, tension and shear loading respectively, are applied to bonded anisotropic plates to observe mixed mode deformations.

• Proceedings of the Korean Society For Composite Materials Conference
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• 한국복합재료학회 2001년도 춘계학술발표대회 논문집
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• pp.250-253
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• 2001

Recently, based on the smart structure concept, optical fiber sensors have been increasingly applied to monitor the various engineering and civil structural components. Repairs based on adhesively bonded fiber reinforce composite patches are more structurally efficient and much less damaging to the parent structure than standard repairs based on mechanically fastened metallic patches. As a result of the high reinforcing efficiency of bonded patches fatigue cracks can be successfully repaired. However, when such repairs are applied to primary structures, it is needed to demonstrate that its loss can be immediately detected. This approach is based on the "smart patch" concept in which the patch system monitors its own health. The objective of this study is to evaluate the potentiality of application of transmission-type extrinsic Fabry-Perot optical fiber sensor (TEFPI) to the monitoring of crack growth behavior of composite patch repaired structures. The sensing system of TEFPI and the data reduction principle for the detection of crack detection are presented. Finally, experimental results from the tests of center-cracked-tension aluminum specimens repaired with bonded composite patch is presented and discussed.

• Journal of the Korean Society for Nondestructive Testing
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• 제19권6호
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• pp.439-447
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• 1999

One of the problems for practical use of fiber-reinforced plastics is the performance degradation by fatigue damage in the joints. The study is to develop a nondestructive technique for real-time evaluation of adhesively bonded composite-metal joints. From the prior study we confirmed that the bonding strength can be estimated from the correlation between the qualify of bonded parts and AUP's. We obtained a curve showing the correlation between the degree of fatigue damage and AUP's calculated from signals acquired during fatigue loading of single-lap and double-lap joints of CFRP and Al6061. The curve is an analogy to the one showing stiffness reduction ($E/E_o$) of polymer matrix composites by fatigue damage. From those facts, it is plausible to predict the degree of fatigue damage in real-time. Amplitude and AUP2 appeared to be optimal parameters to provide more reliable results for single-lap joints whereas Amplitude and AUP2 did for double-lap joints. It is recommended to select optimal parameters for different geometries in the application for real structures.

• Steel and Composite Structures
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• 제20권6호
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• pp.1275-1303
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• 2016

Steel plates and carbon-fiber-reinforced polymer (CFRP) laminates or plates bonded to concrete substrates have been widely used for concrete strengthening. However, this technique cause plate debonding, which makes the strengthening system inefficient. The main objective of this study is to enhance the bond strength of externally bonded steel plates and CFRP laminates to the concrete surface by proposing new embedded adhesive and steel connectors. The effects of these new embedded connectors were investigated through the tests on 36 prism specimens. Parameters such as interfacial shear stress, fracture energy and the maximum strains in plates were also determined in this study and compared with the maximum value of debonding stresses using a relevant failure criterion by means of pullout test. The study indicates that the interfacial bond strength between the externally bonded plates and concrete can be increased remarkably by using these connectors. The investigation verifies that steel connectors increase the shear bond strength by 48% compared to 38% for the adhesive connectors. Thus, steel connectors are more effective than adhesive connectors in increasing shear bond strength. Results also show that the use of double connectors significantly increases interfacial shear stress and decrease debonding failure. Finally, a new proposed formula is modified to predict the maximum bond strength of steel plates and CFRP laminates adhesively glued to concrete in the presence of the embedded connectors.

• Transactions of the Korean Society of Mechanical Engineers A
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• 제24권8호
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• pp.2000-2006
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• 2000

The enhancement of service life of damaged or cracked structures is currently major issue to the researchers and engineers. In order to improve the life of cracked aging aircraft structures, the repair technique which uses adhesively bonded boron/epoxy composite patches is being widely considered as a cost-effective and reliable method. This paper is to study the performance of the bonded composite patch repair of a plate containing an inclined central through-crack. A 3-dimensional finite element method having three layers to the cracked plate, composite patch and adhesive layer, is used to compute the stress intensity factor. In this paper, the reduction of stress intensity factors near the crack-tip are determined to evaluate the effects of various non-dimensional design parameter including composite patch thickness, and material properties of the composite patch and thickness of the adhesive layer, materials of patch etc., and the crack length, Finally, The problem of how to optimize the patch geometric configurations has been discussed.