• Steel and Composite Structures
• /
• 제17권2호
• /
• pp.145-157
• /
• 2014

This study aimed to investigate the fatigue crack growth behavior of a kind of fiber metal laminates (FML) under four different stress levels. The FML specimen consists of three 2024-T3 aluminum alloy sheets and two layers of glass/epoxy composite lamina. Tensile-tensile cyclic fatigue tests were conducted on centrally notched specimen at four stress levels with various maximum values. A digital camera system was used to take photos of the propagating cracks on both sides of the specimens. Image processing software was adopted to accurately measure the length of the cracks on each photo. The test results show that: (1) a-N and da/dN-a curves of FML specimens can be divided into transient crack growth segment, steady state crack growth segment and accelerated crack growth segment; (2) compared to 2024-T3 aluminum alloy, the fatigue properties of FML are much better; (3) da/dN-${\Delta}K$ curves of FML specimens can be divided into fatigue crack growth rate decrease segment and fatigue crack growth rate increase segment; (3) the maximum stress level has a large influence on a-N, da/dN-a and da/dN-${\Delta}K$ curves of FML specimens; (4) the fatigue crack growth rate da/dN presents a nonlinear accelerated increasing trend to the maximum stress level; (5) the maximum stress level has an almost linear relationship with the stress intensity factor ${\Delta}K$.

• Composites Research
• /
• 제31권5호
• /
• pp.215-220
• /
• 2018

본 연구에서는 적층 패턴이 다른 5가지 섬유금속적층판(Fiber Metal Laminates, FMLs)에 대한 유한요소해석을 수행하여 선행 연구로 수행한 낙추충격시험과의 유사성을 검증하였고, 효과적인 저속 충격 해석 모델을 개발하였다. 또한 동일한 두께를 가지는 연강(mild steel)과 에너지흡수율을 비교하여 Carbon-Steel 섬유금속적층판의 내충격성을 확인하였다. Carbon-Steel 섬유금속적층판은 동일한 두께를 가지는 연강에 비하여 우수한 충격흡수율을 보였으며, 모든 적층 패턴에서 96% 이상의 높은 에너지흡수율 갖는 것을 확인하였다. 본 연구에서 제시한 저속 충격 해석 모델은 복합형상 및 자동차 구조체 연구에 효과적으로 적용할 수 있을 것으로 판단된다.

• International Journal of Precision Engineering and Manufacturing
• /
• 제1권1호
• /
• pp.33-41
• /
• 2000

Fiber reinforced metal laminates(FRMLs) were new type of hybrid materials. FRMLs consist of high strength metals(Al 5052-H34) and laminated fiber with structural adhesive bond. The effect of resin mixture ratios on the fatigue crack propagation behavior and mechanical properties of aramid fiber reinforced aluminum composites was investigated. The epoxy, diglycidylether of bisphenol A(DGEBA), was cured with methylene dianiline(MDA) with or without an accelerator(K-54). Eight kinds of resin mixture ratio were used for the experiment ; five kinds of FRMLs(1)(mixture of epoxy and curing agent) and three kinds of FRMLs(2)mixture of epoxy, curing agent and accelerator). The characteristic of fatigue crack propagation behavior and mechanical properties FRMLs(2) shows more effecting than that of FRMLs(1).

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2003년도 추계학술대회
• /
• pp.1388-1393
• /
• 2003

In this study, analytic stress-displacement solutions are obtained by using a shear lag modeling constructed for the spliced joint area with a splicing gap filled with adhesive material of elastic modulus $E_{a}$ in the fiber metal laminate (FML) which is known to have excellent fatigue, corrosion and fire-flame resistant characteristics while with relatively low densities compared to the conventional aluminum alloys for lightweight structures.

• 한국항공우주학회지
• /
• 제33권6호
• /
• pp.39-44
• /
• 2005

섬유금속적층판(Fiber Metal Laminates, 이하 FML)에서 알루미늄과 유리섬유/에폭시 복합재료 사이의 열팽창 계수의 차이는 경화공정 시 FML내부에 열 잔류응력을 남기게 되며, 이러한 열 잔류응력은 FML의 피로특성과 항복강도에 영향을 주게 된다. 잔류응력을 예측하기 위해 두 가지 실험법이 제안 되었으며, 이론식을 통해 그 결과를 예측하고, 실제 실험을 수행하여 그 값을 확인 하였다. 또한, 열 잔류응력의 제거 및 응력의 역전을 위하여 후-인발 가공이 수행 되었으며, 가공 이후 발생한 FML내의 잔류응력이 측정 되었다. 예측된 열 잔류응력 결과와 실험을 통한 값이 일치함을 보이며, 후-인발 가공을 통하여 열 잔류응력 제거 및 항복강도의 증가가 발생하였다.

• Composites Research
• /
• 제29권5호
• /
• pp.249-255
• /
• 2016

섬유금속적층판은 우수한 피로특성, 내부식성, 충격저항 등으로 인하여 항공우주산업에서 널리 사용되고 있다. 본 논문에서는 다구찌 기법을 사용하여 섬유금속적층판의 내부 에너지 해방률을 향상시킬 수 있는 공정 조건을 도출하는 절차에 대해 실험적 연구가 수행되었다. 내부 접착력 향상을 위한 제조공정을 도출하기 위해서, 표면처리, 접착필름의 용융점 유지시간 및 초기 압력이 서로 다르다는 조건하에서 제작한 시편들에 대해서 Double cantilever beam과 End-notched flexure 시험을 수행하였다. 시험으로부터 모드 I과 모드 II의 에너지 해방률을 측정한 후, 다구찌 기법의 망대특성에 의한 신호 잡음비를 비교하여 효율적인 제조공정을 도출하였다.

• 대한기계학회논문집A
• /
• 제28권2호
• /
• pp.174-180
• /
• 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 $E_{crack}$.

• 대한기계학회논문집A
• /
• 제27권3호
• /
• pp.440-449
• /
• 2003

Residual strength of fiber metal laminates after impact was studied. 3/4 lay up FML was fabricated using 4 ply prepreg, 2 ply aluminum sheets, and 1 ply steel sheet. Quasi isotropic ([0/45/90/-45]s) and orthotropic ([0/90/0/90]s) FRP were also fabricated to compare with FML. Impact test were conducted by using instrumented drop weight impact machine (Dynatup, Model 8250). Penetration load and absorbed energy of FML were superior to those of FRPs. Tensile tests were conducted to evaluate the residual strength after impact. Strength degradation of FML was less than that of FRP. This means that the damage tolerance of FML is excellent than that of FRP. Residual strength of each specimen was predicted by using Whitney and Nuismer(WN) Model. Impact damage area is assumed as a circular notch in WN model. Damage width is defined as the average of back face and top face damage width of each specimen. Average stress and point stress criterions were used to calculate the characteristic length. It is supposing that a characteristic length is a constant. The distribution of characteristic length shows that the assumption is reasonable. Prediction was well matched with experiment under both stress criterions.

• 한국정밀공학회지
• /
• 제16권8호
• /
• pp.149-154
• /
• 1999

FRMLs(Fiber Reinforced Metal Laminates) is a new type of hybrid materials. FRMLs consists of high strength metal and fiber which are laminated using a structural adhesive bond(epoxy resin). The effect of resin mixture ratios on the fatigue crack propagation behavior and mechanical property of Aramid fiber reinforced aluminum composites was investigated. The epoxy, diglycidylether of bisphenol A(DGEBA) was cured with methylene dianiline(MDA) with or without accelerator(K-54). Eight kinds of resin mixture ratio were tested for the experiment ; five kinds of FRMLs(1))epoxy & curing agent) and three kinds of FRMLs(2)(epoxy & curing agent & accelerator). FRMLs(2) have a more effective characteristics on the fatigue crack propagation behavior and mechanical property than FRMLs(1)

• 대한기계학회논문집A
• /
• 제26권11호
• /
• pp.2374-2382
• /
• 2002

Aluminum alloy/aramid fiber reinforced plastic(Al/AFRP) laminates consists of high strength metal(A15052) and laminated aramid fiber with structural adhesive bond. The mixture ratio effect of epoxy resin curing agent accelerator on the tensile strength and T-peel strength characteristic in Al AFRP laminates were investigated in this study. The epoxy. diglycidylether of bisphenol A(DCEBA), It'as cured by methylene dianiline(MDA) with or without an accelerator(K-54). Eight different kinds of resin mixture ratios were selected for the test , five kinds of Al/AFRP laminates were named as Al/AFRP(1) and three others of Al/AFRP laminates were named as Al/AFRP(2). The comparison of tensile strength and T-peel strength with variation of resin mixture ratio were studied. Respectively. Al/AFRP(1) and Al/AFRP(2) indicated approximately 6.0 times and 7.0 times more improved maximum tensile strength in comparison with those of monolithic A15052. Al/AFRP(2) indicated approximately 1.5 times more impoved maximum T-peel strengths in comparison with those of Al/AFRP(1). As results. Al/AFRP(2) turned out to have more effective characteristics on the tensile strength and T-peel strength than those of Al/AFRP(1).