• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.527-532
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• 2000

The armor composite material targets such as aramid FRMLs with different type and ply number of face material and different type of back-up material, were studied to determine ballistic impact resistance and dynamic failure behavior during ballistic impact. Ballistic impact resistance is determined by $\textrm{V}_{50}$ ballistic limit, a statical velocity with 50% probability for complete penetration, test method. Also dynamic failure behaviors are respectfully observed that result from $\textrm{V}_{50}$ tests. $\textrm{V}_{50}$ tests with $0^{\circ}$ obliquity at room temperature were conducted with projectiles that were able to achieve near or complete penetration during high velocity impact tests. As a result, ballistic impact resistance of anodized Al 5052-H34 alloy(2 ply) is better than that of anodized Al 5052-H34 alloy(1 ply), but Titanium alloy showed the similar ballistic impact resistance. In the face material, ballistic impact resistance of titanium alloy is better than that of anodized Al 5052-H34 alloy. In the back-up material, ballistic impact resistance of T750 type aramid fiber is better than that of CT709 type aramid fiber.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.1
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• pp.58-65
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• 2003

The aramid fiber reinforced metal laminates(AFRMLs) used for the wing part fair flight suffer the cyclic bending moment of variable amplitude during service. The fatigue crack propagation and delamination behavior in AFRMLs containing a saw-cut and circular hole was investigated using the average stress criterion(ASC) model. Mechanical tests were carried out using the cyclic bending moment of 4.9 N . m and delamination was observed by ultrasonic C-scan images. In case of AFRMLs containing a saw-cut fatigue crack propagated in aluminum matrix, inducing delamination. However, in case of AFRMLs containing a circular hole, delamination formed with two types under cyclic bending moment of 4.9 N . m. First, delamination formed along the fatigue crack in aluminum matrix. Second, delamination formed without any fatigue crack around the circular hole. Therefore, delamination was formed depending on the stress distribution near the circular hole.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.2
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• pp.174-180
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• 2004

If Fiber Reinforced Metal Laminates(FRMLs) were delaminated, the decrease of stiffness and fiber bridging effect would result in the sudden aggravation of fatigue characteristics. It was reported that the delamination of FRMLs resulted from the crack of metal layers and that it depended on the crack growth. While cracks were made in FRMLs containing a saw-cuts under fatigue loading, cracks could be produced or not in FRMLs with circular holes under the same condition. When the FRMLs with the circular holes produce not the crack but the delamination, it is not possible to analyze it by the conventional fracture parameters expressed as the function of the crack. And so, this research suggests a new analytical model of the delamination to make the comparison of the delamination behavior possible whenever the cracks occur or not. Therefore, a new analytical model called Pseudo Crack Model(PCM) was suggested to compare the delaminations whether cracks were made or not. The relationship between the crack energy consumption rate( $E_{crack}$) and the delamination energy consumption rate( $E_{del}$) was discussed and it was also known that the effect of $E_{del}$ was larger than that of $E_{crack}$.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.479-482
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• 2004

The behavior of fatigue delamination in a GLARE(Glass Fiber Reinforced Metal Laminates) under fatigue loading conditions investigated. The behavior of fatigue delamination was examined basing on investigation of the crack and delamination using a SAM (Scanning Acoustic Microscope). The crack and delamination behavior on the relationship among a-N, SAM images and crack length-delamination length were considered. The test results indicated the features of different fatigue delamination and crack growth according to each fiber orientation angle and also obtained to more increase delamination than crack through the relationship between crack length and delamination length in GLARE.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2003.04a
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• pp.398-404
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• 2003

Most previous researches for the hybrid composite materials such as FRMLs(Al/AFRP, Al/GFRP) have evaluated the fatigue delamination behavior using the traditional fracture mechanism. However, most previous researches have not generally been firmed yet. Because delamination growth behavior in hybrid composite should be consider delamination growth rate, $dA_D$/da using the delamination shape factors, fs instead of traditional fracture mechanic parameters. The major purpose of this study was to evaluate the relationship between delamination shape factor, fs and delamination growth rate, $dA_D$ . And a propose parameter on the delamination aspect ratio, b/a. The details of the study are as follow : 1) Relationship between crack length, a and delamination width,b. 2) Relationship between delamination aspect ration, b/a and delamination area rate,($(A_D)_{N}(A_D)_{ALL}$. 3) Variation of delamination growth rate, $dA_D/da$ was attendant on delamination shape factors, $fs_1$, $fs_2$, $fs_3$. The test results indicated the delamination growth rate depends on delamination shape factors.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.04a
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• pp.113-116
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• 2003

The investigation of delamination growth behavior in hybrid composite material such as FRMLs should be considered delamination growth rate, dA_D/da$ using the delamination shape factor, $f_S$ instead of traditional fracture mechanics parameters. The main objective of this study is to evaluate the relationship between delamination element (i. e. delamination width, b, delamination contour, c, delamination shape factor, $f_S$ and delamination growth rate, dA_D/da$) and delamination growth in FRMLs under cyclic bending moment. The delamination shape formed along the fatigue crack between aluminum layer and glass fiber/epoxy layer are measured by scanning method. The details of study are as follow : ⅰ) Relationship between crack length, a and delamination width, b. ⅱ) Variation of delamination growth rate, dA_D/da$ was attendant on delamination shape factors, $f_{S1}$, $f_{S2}$, $f_{S3}$. The test result indicated the delamination growth behavior depends in delamination element such as delamination width, b, delamination shape factors, $f_{S1}$, $f_{S2}$, $f_{S3}$.