• Journal of Mechanical Science and Technology
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• v.17 no.11
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• pp.1659-1664
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• 2003

A cracked plate with a patch bonded on one side was treated with a crack-bridging model using weight function: assuming continuous distribution of springs acting between th crack surfaces, the stress intensity factor of the patched crack was numerically obtained. Especially in the case of a patched crack subjected to residual non-uniform stress, the stress intensity factor was easily with the corresponding approximate weight function. This paper presented the stress intensity factors for a crack partially patched within a finite plate or a patched crack initiated from a notch.

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.123-128
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• 2000

A cracked-plate with a patch bonded on one side is treated with a crack-bridging model: assuming continuous distribution of springs acting between crack surfaces. the approximate weight function was introduced to obtain the stress intensity factor of patched crack subjected to residual stress or non-uniform stress. The stress intensity factors for the partially patched crack within finite plate or the patched crack initiated from a notch were successfully obtained by numerical calculation.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.4
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• pp.1013-1022
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• 1995

A hybrid composite (APAL;Aramid Patched ALuminum alloy, CPAL;Carbon Patched ALluminum alloy), consisting of a Al 2024-T3 aluminum alloy plate sandwiched between two aramid/epoxy and carbon/epoxy laminate, was developed. Fatigue crack growth behavior was examined at stress ratios of R=0.2, 0.5. The APAL and CPAL showed superior fatigue crack growth resistance, which may be attributed to the crack bridging effect imposed by the intact fibers in the crack wake.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.165-169
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• 2000

A simple method was suggested to calculate the stress intensity factor for a one-sided patched crack with finite thickness. To consider out-of-plane bending effect resulting from the load-path eccentricity, the spring constant as a function of the through-thickness coordinate z was calculated from the stress distribution in the un-cracked plate, ${\sigma}_{yy}(y=0,\;z)$, and the displacement for the representative single strip Joint, $u_y(y=0,\;z)$. The stress Intensity factors were obtained using Rose's asymptotic solution approach and compared with the finite element results. In short crack region, two results had a little difference. However, two results were almost same in long crack region. On the other hand, the stress intensity factor using plane stress assumption was more similar to finite element result than plane strain condition.

• Journal of Welding and Joining
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• v.12 no.4
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• pp.117-126
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• 1994

APAL (Aramid Patched ALuminum alloy) was manufactured, which was a material that was consisting of a A12024-T3 aluminum alloy plate bonded to single-side of it with aramid/epoxy laminates. The aramid/epoxy laminates were bonded to it in condition of 1, 2 ply and fiber orientation of .+-.45, 0.deg./90.deg. Fatigue crack propagation tests were performed at stress ratio R-0.2, 0.5 with Al 2024-T3, APAL 45-1P, APAL 0/90-1P, APAL 45-2P, APAL 0/90-2P specimens to examine behavior of retardation in fatigue crack propagation. All the APAL specimens showed superior fatigue crack resistance. Number of cycle spended for crack to propagate from $a_{M}$=37 to $a_{M}$=65 mm in case of APAL 0/90-2P specimen was half that of Al 2024-T3 specimen. Fatigue crack propagation rate of APAL 0/90 specimens were retarded more compared to APAL 45 specimens and the amounts of retardation at R=0.5 were larger than that at R=0.2. It was found that the retardation in fatigue crack propagation was caused by intact fibers in the wake of crack.ack.

• Composites Research
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• v.12 no.3
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• pp.1-7
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• 1999

New hybrid composite material CPAL(Carbon Patched ALuminum alloy), an Al2024-T3 plate doubleside reinforced with carbon/epoxy laminates were made. Fatigue crack growth tests were carried out at R=0.2, 0.5 in the CPAL specimens. The retardation mechanism and behavior of fatigue crack growth were examined basing on investigation of the crack and the delamination using a X-Ray and a ultrasonic C-Scan. The fatigue crack growth rates of CPAL specimens were remarkedly retarded compared to that of the Al2024-T3 specimen. The retardations amounts of the fatigue crack growth rates get higher in $0^{\circ}$/$90^{\circ}$ CPAL specimen than in $\pm$$45^{\circ}$ CPAL specimen, and get higher at R=0.2 than at R=0.5. The retardation of fatigue crack growth rates in CPAL specimen was generated by the crack bridging mechanism, that is the behavior that the fibers in CFRP layers decrease the COD in the Al2024-T3 plate.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.1
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• pp.160-170
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• 2002

Many of aged and damaged concrete structure have been revitalized with composite reinforcement. Flexural behaviors of composite-patched concrete specimens are characterized by high-sensitivity moire interferometry. The three-mirror, four-beam interferometry system and a compact loading system are used for obtaining singe patterns representing whole-field contour maps of in-plane displacements. It is seen from the calibration test for the loading system that the measured bending displacement is in excellent agreement with the displacement calculated by the beam theory. The crack opening displacement as well as the bending and the horizontal displacement fur the notched and unnotched specimen are investigated. The results also show that the notched specimen reinforced by a composite sheet has sufficient stiffness and strength compared to the original concrete specimen.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2004.04a
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• pp.241-245
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• 2004

An analytical study was conducted to characterize the fatigue crack growth behavior of pre-cracked aluminum plates repaired with asymmetric bonded composite patch. For single-sided repairs, due to the asymmetry and the presence of out-of-plane bending, crack front shape would become skewed curvilinear started from a uniform through-crack profile, as observed from previous studies. In this study, the fatigue analysis of single-sided repairs considering crack front shape development was conducted by implementing three-dimensional successive finite element method coupled with linear elastic fracture mechanics (LEFM) concept, which enables the growing crack front to be directly traced and modeled in a step by step way. Through conducting present analysis technique, crack path of the patched plate as well as the fatigue life was evaluated with sufficient accuracy. The analytical predictions of both the crack front shape evolution and the fatigue life were in good agreement with the experimental observations.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.6A
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• pp.411-418
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• 2012

In this study, behavior of unpatched and patched cylindrical shells with through-wall cracks has been estimated using numerical experiments, and patching effect of them has been investigated according to various patching parameters. To show credibility of numerical models considered, two ways such as h- and p-methods have been adopted. Also, domain integral method and virtual crack extension method have been considered to calculate energy release rates based on linear elastic fracture mechanics. For examples, the unpatched cylindrical shells with circumferential cracks under remote tension have firstly been analyzed to show the validity of finite element modeling with h-method or p-method, and then the results have been compared with literature values published. Next, the sensitive analysis of patch repaired problems in terms of thickness of patch and adhesive, shear modulus of adhesive, composite material type of patch, crack length, etc. has been carried out.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.12
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• pp.2091-2099
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• 2001

Fatigue crack growth behavior of inclined cracked Al 6061-T6 thick aluminum plate(6mm) repaired with the bonded composite patch was studied. A 0°inclined crack bonded reinforced composite patch and 15°, 30°, 45°, 60°inclined crack plates were tested. The effect of patch and inclined angle were studied and compared to each other. Also we investigated to the crack propagation direction and debonding behavior during the fatigue crack growth test. In this paper. a study was con(ducted to get an fatigue life, fatigue crack growth ratio and crack growth direction. Finally, the effectiveness of composite patch on inclined cracked plate was investigated. The results demonstrated thats there was a definite variation in fatigue life and fatigue crack growth behavior depending on the inclined crack angle.