• 제목/요약/키워드: Delamination length

검색결과 85건 처리시간 0.019초

반도체패키지에서의 층간박리 및 패키지균열에 대한 파괴역학적 연구 (1) -층간박리- (A Fracture Mechanics Approach on Delamination and Package Crack in Electronic Packaging(l) -Delamination-)

  • 박상선;반용운;엄윤용
    • 대한기계학회논문집
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    • 제18권8호
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    • pp.2139-2157
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    • 1994
  • In order to understand the delamination between leadframe and epoxy molding compound in an electronic packaging of surface mounting type, the stress intensity factor, T-stress and J-integral in fracture mechanics are obtained. The effects of geometry, material properties and molding process temperature on the delamination are investigated taking into account the temperature dependence of the material properties, which simulates as more realistic condition. As the crack length increases the J-integral increases, which suggest that the crack propagates if it starts growing from the small size. The effects of the material properties and molding process temperature on stress intensity factor, T-stress is and J-integral are less significant than the chip size for the practical cases considered here. The T-stress is negative in all eases, which is in agreement with observation that interfacial crack is not kinked until the crack approaches the edge of the leadframe.

유리탄소섬유 하이브리드 복합재의 절삭 조건에 따른 가공 결함 비교 (Comparison of Machining Defects by Cutting Condition in Hybird FRP Drilling)

  • 백종현;김수진
    • 한국기계가공학회지
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    • 제21권9호
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    • pp.12-20
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    • 2022
  • Delamination and burr defects are important problems in drilling fiber reinforced plastics. A method for measuring FRP drilling defects has been studied. Delamination and burr factors were defined as the relative length or area. Using these factors, the effects of tool shape and drilling conditions on delamination and burr were studied. In this study, the defects that occur when drilling a glass-carbon fiber hybrid composite were compared in terms of three factors. In the glass-carbon fiber hybrid composite, the effects of the feed rate and tool point angle on the delamination and burr factors were similar to those in previous studies. The diameter of the tool did not affect the defect factor. A circular burr was generated in a drill tool with a point angle of 184°, and a relatively small deburring factor was observed compared with a tool with a point angle of 140°.

Delamination of non-linear viscoelastic beams under bending in the plane of layers

  • Victor I. Rizov
    • Coupled systems mechanics
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    • 제12권4호
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    • pp.297-313
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    • 2023
  • This paper deals with delamination analysis of non-linear viscoelastic multilayered beam subjected to bending in the plane of the layers. For this purpose, first, a non-linear viscoelastic model is presented. In order to take into account the non-linear viscoelastic behaviour, a non-linear spring and a non-linear dashpot are assembled in series with a linear spring connected in parallel to a linear dashpot. The behaviours of the non-linear spring and dashpot are described by applying non-linear stress-strain and stress-rate of strain relationships, respectively. The constitutive law of the model is derived. Due to the non-linear spring and dashpot, the constitutive law is non-linear. This law is used for describing the time-dependent mechanical behaviour of the beam under consideration. The material properties involved in the constitutive law vary along the beam length due to the continuous material inhomogeneity of the layers. Solution of the strain energy release rate for the delamination is obtained by analyzing the balance of the energy with considering of the non-linear viscoelastic behaviour. The strain energy release rate is found also by using the complementary strain energy for verification. A parametric study is carried-out by using the solution obtained. The solutions derived and the results obtained help to understand the time-dependent delamination of non-linear viscoelastic beams under loading in the plane of layers.

정수압을 받는 일방향 탄소섬유/에폭시 복합재의 파괴인성 결정을 위한 일인자 적용 (Application of Work Factor to Determine Fracture Toughness of Unidirectional Graphite/Epoxy Composites under Hydrostatic Pressure)

  • 이경엽
    • 한국복합재료학회:학술대회논문집
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    • 한국복합재료학회 2001년도 춘계학술발표대회 논문집
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    • pp.46-49
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    • 2001
  • In this paper. tile validity of work factor approach was investigated to determine compressive fracture toughness of unidirectional graphite/epoxy composites under hydrostatic pressure environment. The elastic work factor was determined under various pressures as a function of delamination length. It was found that elastic work factor was not affected by hydrostatic pressure.

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Al/CFRP 하이브리드 복합재료의 인장파괴거동 (The Behavior of Tensile Fracture for Al/CFRP Hybrid Composite Material)

  • 강지웅;권오헌;유진규
    • 한국안전학회지
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    • 제24권2호
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    • pp.23-29
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    • 2009
  • The hybrid composite materials are recently used in many field as an advanced material due to their high resistance to fracture. However, hybrid composite materials have several problems, especially delamination, compared with homogeneous materials such as an aluminum alloy, etc. In this study, we carried out the tensile test to study the tension failure appearances and tensile ultimate strength of CFRP/Al/CFRP hybrid composite materials. The CFRP material used in the experiment is a commercial material known as CU175NS in unidirectional carbon prepreg. Also Al/CFRP/Al hybrid composites with three kind length of a single edge crack were investigated for the relationship between an aluminium volume fraction and a crack length. The crack length was measured by a traveling microscope under a universal dynamic tester. Futhermore the stress intensity factor behavior was examined according to a volume fraction and an initial crack length ratio to a width.

Multilayered inhomogeneous beam under prescribed angle of twist and displacements: A delamination analysis

  • Victor I. Rizov
    • Coupled systems mechanics
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    • 제13권2호
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    • pp.153-170
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    • 2024
  • The problem considered in this theoretical paper is the delamination of a multilayered inhomogeneous beam structure that has viscoelastic behaviour under angle of twist, horizontal and vertical displacements which vary smoothly with time according to prescribed laws. The cross-section of the beam is a rectangle. The layers are made of different materials which are smoothly inhomogeneous along the length of the beam. The beam under consideration represents statically undetermined structure since it is clamped in its two ends. The problem of the strain energy release rate is solved. For this purpose, the strain energy stored in the beam structure is analyzed. In order to verify the solution obtained, the strain energy release rate is found also analyzing the time-dependent compliances of the beam under prescribed angle of twist and displacements. A parametric investigation is carried-out by applying the solution obtained. Special attention is paid to the effect of the parameters which control the variation of the angle of twist and the displacements with time on the strain energy release rate.

Effects of edge crack on the vibration characteristics of delaminated beams

  • Liu, Yang;Shu, Dong W.
    • Structural Engineering and Mechanics
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    • 제53권4호
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    • pp.767-780
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    • 2015
  • Delaminations and cracks are common failures in structures. They may significantly reduce the stiffness of the structure and affect their vibration characteristics. In the present study, an analytical solution is developed to study the effect of an edge crack on the vibration characteristics of delaminated beams. The rotational spring model, the 'free mode' and 'constrained mode' assumptions in delamination vibration are adopted. This is the first study on how an edge crack affects the vibration characteristic of delaminated beams and new nondimensional parameters are developed accordingly. The crack may occur inside or outside the delaminated area and both cases are studied. Results show that the effect of delamination length and thickness-wise location on reducing the natural frequencies is aggravated by an increasing crack depth. The location of the crack also influences the effect of delamination, but such influence is different between crack occurring inside and outside the delaminated area. The difference of natural frequencies between 'free mode' and 'constrained mode' increases then decreases as the crack moves from one side of the delaminated region to the other side, peaking at the middle. The analytical results of this study can serve as the benchmark for FEM and other numerical solutions.

다양한 기하학적 형상을 갖는 층간 분리된 복합신소재 적층구조의 동적 불안정성 (Dynamic Instability of Delaminated Composite Structures with Various Geometrical Shapes)

  • 이상열;장석윤
    • 복합신소재구조학회 논문집
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    • 제1권1호
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    • pp.1-8
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    • 2010
  • The dynamic instability analysis of delaminated composite structures subjected to in-plane pulsating forces is carried out based on the higher order shell theory of Sanders. In the finite element (FE) formulation, the seven degrees of freedom per each node are used with transformations in order to fit the displacement continuity conditions at the delamination region. The boundaries of the instability regions are determined using the method proposed by Bolotin. The numerical results obtained for skew plates and shells are in good agreement with those reported by other investigators. The new results for delaminated skew plate and shell structures in this study mainly show the effect of the interactions between the radius-length ratio and other various parameters, for example, skew angles, delamination size, the fiber angle of layer and location of delamination in the layer direction. The effect of the magnitude of the periodic in-plane load on the instability regions is also investigated.

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MMB시험에 의한 평직 CFRP/GFRP 적층판 혼합모드 층간분리의 실험적 평가 (The Experimental Evaluation of the Mixed Mode Delamination in Woven CFRP/GFRP Laminates under MMB Test)

  • 곽정훈;강지웅;권오헌
    • 한국안전학회지
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    • 제28권4호
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    • pp.14-18
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    • 2013
  • Blades of horizontal axis are nowadays made of composite materials. Generally, composite materials satisfy design provides lower weight and good stiffness, while laminate composites have often damages as like the delamination and cracks at the interface of laminates. The box spar and tail parts of a blade are composed of the CFRP/GFRP hybrid laminate composites. However, delamination and the interfacial crack often occur in the interface of CFRP/GFRP hybrid laminate composites under the mixed mode fracture condition, especially mode I and mode II. Therefore, there is a need for the evaluation of the mixed mode fracture behavior during the delamination of CFRP/GFRP hybrid laminates. This study shows the experimental results for the delamination fracture toughness in CFRP/GFRP hybrid laminate composites. Fracture toughness experiments and estimation are performed by using DMMB(Dissimilar mixed mode bending) specimen. The materials used in the test are a commercial woven type CFRP(Carbon fiber reinforced plastic) prepreg(CF3327) and UD type GFRP(Glass fiber reinforced plastic) prepreg(HD224A). A CFRP/GFRP hybrid laminate composite is composed by the 10 plies CFRP and GFRP prepreg for DMMB. A thickness of CFRP and GFRP layer is 2.5mm and 3.0mm, respectively. Also the fulcrum location which is a loading parameter is changed from 80 to 100mm on the specimen of length 120mm because it defines the ratio of mode I to mode II. In this study, the effects of the fulcrum location are evaluated in the viewpoint of energy release rate in mode I and mode II contribution. The results show that the delamination crack initiates at higher displacement and lower load according to the increase of the fulcrum location ratio. And the variation of the energy release rate for mode I and II contributions for the mode mixity are shown.

CFRP 적층쉘의 적층구성 및 곡률 변화에 따른 관통 특성 (Penetration Characteristics of CFRP Laminated shells according to Stacking Sequence and Curvature)

  • 조영재;김영남;양인영
    • 한국정밀공학회지
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    • 제22권2호
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    • pp.164-171
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    • 2005
  • This study aims to examine an effect of stacking sequence and curvature on the penetration characteristic of a composite laminated shell. For the purpose, we manufactured specimens with different stacking sequences and curvatures, and conducted a penetration test using an air-gun. To examine an influence according to stacking sequence, as flat plate and curvature specimen had more plies, their critical penetration energy was higher, Critical penetration energies of specimen A and C with less interfaces somewhat higher than those of B and D with more interfaces. The reason that with less interfaces, critical penetration energy was higher is pre-impact bending stiffness of composite laminated shell with less interfaces was lower than that of laminated shell with more interfaces, but bending stiffness after impact was higher. And it is because interface, the weakest part of the composite laminated shell, was influenced by transverse impact. As curvature increases, critical penetration energy increases linearly. It is because as curvature increases, resistance to in-plane deformation as well as bending deformation increases, which need higher critical penetration energy. Patterns of cracks caused by penetration of composite laminated shells include interlaminar crack, intralaminar crack, and laminar fracture. A 0$^{\circ}$ply laminar had a matrix crack, a 90$^{\circ}$ply laminar had intralaminar crack and laminar fracture, and interface between 0$^{\circ}$and 90$^{\circ}$laminar had a interlaminar crack. We examined crack length and delamination area through a penetration test. For the specimen A and C with 2 interface, the longest circumferential direction crack length and largest delamination area were observed on the first interface from the impact point. For the specimen B and D with 4 interface, the longest crack length and largest delamination area were observed on the third interface from the impact point.