• 제목/요약/키워드: delamination fracture

검색결과 175건 처리시간 0.026초

틸팅열차 차체용 탄소섬유직물/에폭시 복합재의 모우드 I 층간파괴인성 평가 (Evaluation of Mode I Interlaminar Fracture Toughness for Carbon Fabric/Expocy Composite for Tilting Train Carbody)

  • 허광수;김정석;윤성호
    • 한국철도학회논문집
    • /
    • 제8권6호
    • /
    • pp.573-580
    • /
    • 2005
  • Model I interlaminar fracture behaviors of the carbon/epoxy composite, one of the candidate composites for a tilting train carbody, were investigate by the use of DCB(Double cantilever beam) specimens. These specimens were made of CF3327 plain woven fabric with epoxy resin, and an artificial starter delamination was fabricated by inserting Teflon film with the thickness of $12.5{\mu}m$ of $25.0{\mu}m$ at the one end of the specimen. Mode I interlaminar fracture toughness was evaluated for the specimens with the different thickness of an inserter. Also delamination propagating behaviors and interlaminar fracture surface were examined through an ooptical travelling scope and a scanning electron microscope. We found that abruptly unstable crack propagation called as stick-slip phenomena was observed. In addition, interlaminar fracture behaviors were affected on the location and the morphology of a crack tip as well as an interface region.

Interlaminar stresses and delamination of composite laminates under extension and bending

  • Nguyen, Tien Duong;Nguyen, Dang Hung
    • Structural Engineering and Mechanics
    • /
    • 제25권6호
    • /
    • pp.733-751
    • /
    • 2007
  • The metis element method (Hung 1978) has been applied to analyse free edge interlaminar stresses and delamination in composite laminates, which are subjected to extension and bending. The paper recalls Lekhnitskii's solution for generalized plane strain state of composite laminate and Wang's singular solution for determination of stress singularity order and of eigen coefficients $C_m$ for delamination problem. Then the formulae of metis displacement finite element in two-dimensional problem are established. Computation of the stress intensity factors and the energy release rates are presented in details. The energy release rate, G, is computed by Irwin's virtual crack technique using metis elements. Finally, results of interlaminar stresses, the three stress intensity factors and the energy release rates for delamination crack in composite laminates under extension and bending are illustrated and compared with the literature to demonstrate the efficiency of the present method.

Fracture Analysis of Electronic IC Package in Reflow Soldering Process

  • Yang, Ji-Hyuck;Lee, Kang-Yong;Lee, Taek sung;Zhao, She-Xu
    • Journal of Mechanical Science and Technology
    • /
    • 제18권3호
    • /
    • pp.357-369
    • /
    • 2004
  • The purposes of the paper are to analyze the fracture phenomenon by delamination and cracking when the encapsulant of plastic IC package with polyimide coating shows viscoelastic behavior under hygrothermal loading in the IR soldering process and to suggest more reliable design conditions by the approaches of stress analysis and fracture mechanics. The model is the plastic SOJ package with the polyimide coating surrounding chip and dimpled diepad. On the package without cracks, the optimum position and thickness of polyimide coating to decrease the maximum differences of strains at the bonding surfaces of parts of the package are studied. For the model delaminated fully between the chip and the dimpled diepad, C(t)-integral values are calculated for the various design variables. Finally, the optimal values of design variables to depress the delamination and crack growth in the plastic IC package are obtained.

탄소섬유직물/에폭시 복합제의 모우드 I 층간파괴인성 평가 (Evaluation of Mode I Interlaminar Fracture Toughness for Carbon Fabric/Epoxy Composite)

  • 이은동;윤성호;신광복;정종철
    • 한국철도학회:학술대회논문집
    • /
    • 한국철도학회 2004년도 추계학술대회 논문집
    • /
    • pp.698-703
    • /
    • 2004
  • In this study, mode I interlaminar fracture phenomena of carbon fabric/epoxy composite for tilting train were investigated. Specimens were 25mm $\times$ 180mm $\times$ 4.7mm with an initial artificial delamination of 65mm at one end. This delamination with the thickness of 12.5$\mu$m and 25$\mu$m (teflon film) was used. Mode I interlaminar fracture toughness was measured using the double cantilever beam and the fractured surfaces were examined through a scanning electron microscope. The experimental results obtained in this study would be applicable in the design and structural analysis of the composite structures.

  • PDF

탄소나노튜브로 보강된 탄소섬유복합재의 제조 공정과 모드 1 파괴인성 (Processing and Mode 1 Fracture Toughness of Carbon Fiber Composites Reinforced With Carbon Nanotubes)

  • 김한상
    • Composites Research
    • /
    • 제24권5호
    • /
    • pp.39-43
    • /
    • 2011
  • 탄소나노튜브로 보강된 고분자 수지에 대한 연구는 지난 20년간 활발히 수행되어 왔다. 또한 이를 이용하여 탄소섬유복합재의 물성을 증대시키기 위한 연구도 최근 그 영역을 넓혀가고 있다. 탄소섬유복합재는 탄소섬유의 비약적인 발전으로 섬유 방향의 기계적 물성은 상당히 만족할 만한 수준에 도달했으나, 수지에 의해 좌우되는 기계적 물성은 아직 기대에 못미치고 있다. 특히, 층간의 분리 (delamination)는 탄소섬유복합재의 가장 전형적이며 치명적인 파손의 원인중 하나이다. 이 층간분리에 대한 저항성을 알아보는 모드 1 파괴인성 실험 (혹은 double cantilever beam, DCB test)을 다양한 작용기로 기능화된 SWNT가 첨가된 탄소섬유복합재 시편에 대하여 수행하였다. 부직포 형태의 탄소나노튜브층을 이용한 시편의 경우 10.6%의 파괴인성 증대를 보였다.

GF/PP 복합재료의 충격파괴거동에 관한 연구 (A Study on the Impact Fracture Behavior of Glass Fiber Polypropylene Composites)

  • 엄윤성
    • 수산해양기술연구
    • /
    • 제35권4호
    • /
    • pp.421-427
    • /
    • 1999
  • The critical fracture energy and failure mechanisms of GF/PP composites are investigated in the temperatures range of the ambient temperature to $-50^{\circ}C$ The critical fracture energy increase as fiber volume fraction ratio increased The critical fracture energy shows a maximum at ambient temperature and it tends to decrease as temperature goes up. Major failure mechanisms can be classfied such as fiber matrix debonding, fiber pull-out and/or delamination and matrix deformation.

  • PDF

Critical thrust force and feed rate determination in drilling of GFRP laminate with backup plate

  • Heidary, Hossein;Mehrpouya, Mohammad A.;Saghafi, Hamed;Minak, Giangiacomo
    • Structural Engineering and Mechanics
    • /
    • 제73권6호
    • /
    • pp.631-640
    • /
    • 2020
  • Using backup plate is one of the most commonly used methods to decrease drilling-induced delamination of composite laminates. It has been shown that, the size of the delamination zone is related to the vertical element of cutting force named as thrust force. Also, direct control of thrust force is not a routine task, because, it depends on both drilling parameters and mechanical properties of the composite laminate. In this research, critical feed rate and thrust force are predicted analytically for delamination initiation in drilling of composite laminates with backup plate. Three common theories, linear elastic fracture mechanics, classical laminated plate and mechanics of oblique cutting, are used to model the problem. Based on the proposed analytical model, the effect of drill radius, chisel edge size, and backup plate size on the critical thrust force and feed rate are investigated. Experimental tests were carried out to prove analytical model.

AE법에 의한 유한 폭 CFRP 판재의 파괴특성 (Fracture Characteristics of Finite-Width CFRP Plates by Acoustic Emission)

  • 박성완;이장규
    • 한국공작기계학회논문집
    • /
    • 제16권3호
    • /
    • pp.125-132
    • /
    • 2007
  • The purpose of present paper is to investigate a fracture characteristics of the finite-width single-edge-notch(SEN) carbon fiber/epoxy reinforced plastics(CFRP) plates by using an acoustic emission(AE). Uni-directionally oriented 10 plies CFRPs specimen which had different notch length were prepared for monotonic tensile test. Matrix cracking appeared over whole testing process and fiber breaking appeared later on mainly Load distribution factor of the matrix confirmed that increased according as increases of plate width ratio. The amplitude distribution of AE signal from a specimens is an aid to the determination of the different fracture mechanism such as matrix cracking, disbonding, interfacial delamination, fiber pull-out, fiber breaking, and etc. In the result of AE amplitude distribution analysis, matrix cracking, fiber disbonding or interfacial delamination, and fiber pull-out or fiber breaking signal correspond to <65dB, <75dB, and <90dB respectively, Also, changes of the slope of cumulative AE energy represented crazing phenomena or degradation of materials.

Carbon/Phenolic 내열 복합재료의 기계적 특성 (Mechanical Properties of Carbon/Phenolic Ablative Composites)

  • 김평완;홍순형;김연철;예병한;정발
    • 한국복합재료학회:학술대회논문집
    • /
    • 한국복합재료학회 1999년도 추계학술발표대회 논문집
    • /
    • pp.160-163
    • /
    • 1999
  • The mechanical properties and failure behaviour of carbon/phenolic composites were inverstigated by tension and compression. Carbon/phenolic composites were fabricated by infiltration of matrix into 8 harness satin woven fabric of PAN-based carbon fibers. The tensile and compressive tests were performed at 25℃ under air atmosphere and, at 400℃ and 700℃ under N₂ atmosphere. The tensile strengths of carbon/phenolic composites in with-laminar/0° warp direction were about 10 times higher than those in with-laminar/45° warp direction, which was analyzed due to a change of fracture mode from fiber pull-out by shear to tensile fracture of fibers. The fracture of carbon/phenolic composites in with-laminar/45° direction was analyzed due to delamination by buckling. Tensile and compressive strength of carbon/phenolic composites decreased to about 50% at 400℃, and to about 10% at 700℃ compared to that at room temperature. The main reason for the decrease of tensile or compressive strength with increasing temperature was analyzed due to a reduction of bond strength between fibers and matrix resulting from thermal degradation of phenolic resin.

  • PDF

복합적층판의 층간파괴에 미치는 충격하중속도의 효과 (Effects of Impact Loading Rate on the Delamination Behavior of Composite Laminates)

  • 최낙삼
    • 대한기계학회논문집A
    • /
    • 제23권11호
    • /
    • pp.1886-1895
    • /
    • 1999
  • The delamination behavior of multidirectional carbon-fiber/epoxy composite laminates under 10NA intermediate and high rates of test, up to rate of about 11.4m s has been investigated using the double cantilever beam specimens. The mode I loading under rates above l.0m/s showed considerable dynamic effects on the load-time curves and thus higher values of the average crack velocity than that expected from a simple proportional relationship with the test rate. The modified beam analysis utilizing only the opening displacement and crack length exhibited an effective means for evaluating the dynamic fracture energy $G_{IC}$. Based on the assumption of constant flexural modulus, values of $G_{IC}$ at the crack initiation and arrest were decreased with an increase of the test rate up to 5.7m/s, but the maximum $G_{IC}$ was increased at 11.4m/s.