• Structural Engineering and Mechanics
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• 제59권1호
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• pp.123-132
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• 2016

Many military and commercial aging aircrafts flying beyond their design life may experience severe crack and corrosion damage, and thus lead to catastrophic failures. In this paper, were used in a finite element model to evaluate the effect of corrosion on the adhesive damage in bonded composite repair of aircraft structures. The damage zone theory was implemented in the finite element code in order to achieve this objective. In addition, the effect of the corrosion, on the repair efficiency. Four different patch shapes were chosen to analyze the adhesive damage: rectangular, trapezoidal, circular and elliptical. The modified damage zone theory was implemented in the FE code to evaluate the adhesive damage. The obtained results show that the adhesive damage localized on the level of corrosion and in the sides of patch, and the rectangular patch offers high safety it reduces considerably the risk of the adhesive failure.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2002년도 춘계학술발표대회 논문집
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• pp.167-172
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• 2002

During the operation of military aircraft, maintenance is divided into organizational, intermediate and depot maintenance. In the depot maintenance, after removal of major parts and removable doors, damage assessment is performed. Locating damage, charactering the damage and determining its extent, zoning the damage on the part being repaired and re-evaluation of the damaged area after damage removal. Repair joints are classified by bonded joints and bolted joints, depending on joining material. In this paper, repair method in aging aircraft is investigated and the possibility of application of copmposite patch is surveyed.

• 대한기계학회논문집A
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• 제25권12호
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• pp.2070-2077
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• 2001

An experimental investigation of the effect of composite patching repair was conducted to characterize the fatigue crack growth behavior in thick A16061-T6 (6mm) panels with single bonded patch by fiber reinforced composite patch. Four patch lengths and no patch plate were examined. An analytical procedure, involving three-dimensional finite element method having three layers to model cracked aluminum plate, epoxy by adhesive and composite Patch, is calculated the stress intensity factors. From the calculated stress intensity factors, the fatigue crack growth rates are obtained. At the single patching type, different fatigue crack growth ratios through the palate thickness were investigated by using the experimental and analytical results. The results demonstrated that there was a definite variation in fatigue life depending on the size of composite patch. While crack reached the patch end, retardation of crack growth was also revealed in the bonded repair.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집A
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• pp.292-298
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• 2001

An experimental investigation of the effect of composite patching repair was conducted to characterize the fatigue crack growth behavior in thick A16061-T6 (6mm) panels with single bonded patch by fiber reinforced composite patch. Four patch lengths and no patch plate were examined. An analytical procedure, involving three-dimensional finite element method having three layers to model cracked aluminum plate, epoxy by adhesive and composite patch, is calculated the stress intensity factors. From the calculated stress intensity factors, the fatigue crack growth rates are obtained. At the single patching type, different fatigue crack growth ratios through the plate thickness were investigated by using the experimental and analytical results. The results demonstrated that there was a definite variation in fatigue life depending on the size of composite patch. While crack reached the patch end, retardation of crack growth was also revealed in the bonded repair.

• International Journal of Precision Engineering and Manufacturing
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• 제1권2호
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• pp.55-60
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• 2000

A comparison of Riveted and bonded repairs, bearing and net tension failures, and Al 6061-T6 plates is presented. The results are then compared with previous papers about bonded repairs on different patch materials and shapes. Aluminum alloys, including Al 6061-T6, have a face-centered-cubic crystal structure. Under normal circumstances, these types of crystal structures do not exhibit cleavage fractures even at very low temperatures. In aluminum-base structures, the cracked plate structures are frequently repaired using mechanical fasteners-either rivets of bolts- even though patch-bonding techniques are applied to repair and reinforce the structure. Static test results indicate that the riveted repairs are affected by the position of the rivers. When using the same size of patch, the bonded repair technique is stronger; the rate of elongation is also increased. Form FEM analysis, it is revealed the origin of patch debonding in patch-bonded structures is the edge of the patch along to the tensile strength.

• Journal of Chest Surgery
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• 제24권6호
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• pp.560-569
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• 1991

The surgical management of symptomatic tetralogy of Fallot in infants is debatable. From November 1986 to August 1990, 21 infants under 10 kg of the body weight with tetralogy of Fallot underwent primary repair. Mean body weight was 8.6$\pm$1.40kg. All the patient were clubbing and there were cyanotic except for 1 patient. Transannular patch was laid down in 8 patients. Right ventricular outflow patch was used with Goretex but pericardial patch was utilized in 3 patients at the initial period of operation. Incidence of the complications following total correction of tetralogy of Fallot was more frequent in the patients placed with transannular patch compared to the patients with right ventricular outflow tract patch. Two deaths occurred in the 21 patients, Hospital mortality was 9.4%, but there were no operative deaths in the patients who transannular patch was laid down. Causes of deaths were low cardiac output.

• Structural Engineering and Mechanics
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• 제91권2호
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• pp.135-147
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• 2024

The objective of this study is to analyze, using the finite element method, the durability of damaged and repaired structures under the effect of mechanical loading coupled with environmental conditions (water absorption and/or temperature). The study is based on the hybrid patch repair technique, considering several parameters based on the J integral to observe the behavior of the adhesive in transferring load from a damaged plate to the repair patch. The results clearly show that water absorption and increased temperature cause degradation of the mechanical properties of the adhesive, leading to an increase in its plasticization, which is beneficial for the assembly's strength. However, the degradation of the adhesive's properties due to aging in the repair results in poor load transfer from the damaged area to the patch. The findings of this study allowed the authors to conclude that the [0°]8 sequence consistently offers the best performance, with the lowest J integral values and superior crack resistance. The lowest the J integral for the [0°]8 stacking sequence is typically 3-7% lower than that of the [0/-45/45/90]S and [0/-45/90/45]S sequences at elevated temperatures. At 60℃, the J integral increases by approximately 3-6% compared to 40℃ and 20, depending on the aging duration and stacking sequences.

• Structural Engineering and Mechanics
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• 제57권2호
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• pp.295-313
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• 2016

In this study, the three-dimensional finite element method is used to determine the stress intensity factor in Mode I and Mixed mode of a centered crack in an aluminum specimen repaired by a composite patch using contour integral. Various mesh densities were used to achieve convergence of the results. The effect of adhesive joint thickness, patch thickness, patch-specimen interface and layer sequence on the SIF was highlighted. The results obtained show that the patch-specimen contact surface is the best indicator of the deceleration of crack propagation, and hence of SIF reduction. Thus, the reduction in rigidity of the patch especially at adhesive layer-patch interface, allows the lowering of shear and normal stresses in the adhesive joint. The choice of the orientation of the adhesive layer-patch contact is important in the evolution of the shear and peel stresses. The patch will be more beneficial and effective while using the cross-layer on the contact surface.

• Composites Research
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• 제12권4호
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• pp.17-24
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• 1999

프리프레그 덧대기 방법을 이용하여 복합재료 쉘 구조물을 수리할 때 발생하는 잔류 변형을 고찰하기 위해서 유한요소해석과 실험을 수행하였다. 삼차원 응축 쉘 요소와 일차 전단변형 이론에 기초하여 유한요소 프로그램을 개발하였다. 자유 경계조건을 갖는 적층 쉘에 대한 해석결과를 프리프레그 덧대기 수리과정을 통해 측정된 변형률과 비교 검토하였다. 네 변이 고정된 적층 쉘을 프리프레그 덧대기로 수리할 경우 최종 잔류응력이 덧대기 부근에서 크게 발생하였다. 적층 쉘과 덧대기의 적층순서는 잔류응력에 크게 영향을 미치고, 또한 적층 쉘과 덧대기의 적층 순서가 동일해도 잔류응력이 발생하였다.

• 대한기계학회논문집A
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• 제24권9호
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• pp.2246-2251
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• 2000

Adhesive bonding repair methods has been used for a number of decades for construction of damaged structures. In order to evaluate 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. But, this repair method contains many shortcomings. One of these shortcomings, debonding is major issue. When the adhesive shear stress increases, debonding is caused at the end of patch and plate interface. And this debonding is another defect except cracks propagation. In this paper, we assess safety at the cracked AI-plate repaired by Br/Epoxy composite patch. Firstly, from the view of fracture mechanics, reduction of stress intensity factors is determined by the variety of patch feature. Secondly, using the elastic analysis and finite element analysis, the distribution of adhesive shear stresses is acquired. Finally, The problem of how to optimize the geometric configurations of the patch has been discussed.