• Title/Summary/Keyword: Delamination

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Isothermal Pass Schedule to Prevent Delamination in the Dry Wire Drawing Process (층간분리 방지를 위한 건식 등온 신선 패스 설계)

  • Ko, Dae-Cheol;Lee, Sang-Kon;Kim, Min-An;Kim, Byung-Min
    • Journal of the Korean Society for Precision Engineering
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    • v.24 no.1 s.190
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    • pp.57-63
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    • 2007
  • Wire drawing process of the high carbon steel with a high speed is usually conducted at room temperature using a number of passes or reductions through consequently located dies. In the multi-pass drawing process, temperature rise in each pass affects the mechanical properties of the final product such as bending, torsion, and tensile property, etc. This temperature rise during the deformation promotes the occurrence of delamination, and deteriorates the torsion property and durability of wire. This study investigates the occurrence of delamination in the wire through the torsion test and the evaluation of wire temperature. The excessive wire temperature leads to the occurrence of the delamination. Based on the calculation of the wire temperature, a new pass schedule, which can prevent the delamination due to the excessive wire temperature rise, is designed through the isothermal pass schedule.

A Study on the Delamination Growth in Composite Laminates Subjected to Low-Velocity Impact (저속 충격을 받는 복합 재료 적층판의 층간 분리 성장에 관한 연구)

  • 장창두;송하철;김호경;허기선;정종진
    • Journal of Ocean Engineering and Technology
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    • v.16 no.6
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    • pp.55-59
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    • 2002
  • Delamination means that cracking occurs on the interface layer between composite laminates. In this paper, to predict the delamination growth in composite laminates subjected to low-velocity impact, the unit load method was introduced, and an eighteen-node 3-D finite element analysis, based on assumed strain mixed formulation, was conducted. Strain energy release rate, necessary to determine the delamination growth, was calculated by using the virtual crack closure technique. The unit load method saves the computation time more than the re-meshing method. The virtual crack closure technique enables the strain energy release rate to be easily calculated, because information of the singular stress field near the crack tip is not required. Hence, the delamination growth in composite laminates that are subjected to low-velocity impact can be efficiently predicted using the above-mentioned methods.

Influence of Couplings on the Buckling Behavior of Composite Laminates with a Delamination (층간분리로 인한 연계강성이 복합재 적층판의 좌굴거동에 미치는 영향)

  • 김효진;홍창선
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.19 no.2
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    • pp.354-362
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    • 1995
  • The finite element modeling is used to study the buckling and postbuckling behavior of composite laminates with an embedded delamination. Degenerated shell element and rigid beam element are utilized for the finite element modeling. In the nonlinear finite element formulation, the updated Lagrangian description method based on the second Piola-Kirchhoff stress tensor and the Green strain tensor is used. The buckling and postbuckling behavior of composite laminates with a delamination are investigated for various delamination sizes, stacking sequences, and boundary conditions. It is shown that the buckling load and postbuckling behavior of composite laminates depend on the buckling model which is determined by the delamination size, stacking sequence and boundary condition. Also, results show that introduction of couplings can reduce greatly the buckling load.

Impact Damage of CFRP Laminated Composites Subjected to Impact Loading (충격하중을 받는 CFRP 적층복합재의 충격손상에 관한 연구)

  • M.S. KiM;Park, S.B.
    • Journal of the Korean Society for Precision Engineering
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    • v.14 no.7
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    • pp.116-125
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    • 1997
  • An investigation was performed to study the impact damage in CFRP laminated composites subjected to impact loading. A finite element model has been developed for predicting the impact damage in laminated composite plates resulting from the ballistic impact. The finite element model was based on the higher-order shear deformation theory and was used to predict the initial intraply matrix cracking and the shape and size of interface delamination in laminated composites. Numerical simulation was performed and then the initiation of the matrix cracking and the shape and size of impacted induced delamination were predicted, and te results were compared with those of impact experiments with the same dimension and stacking sequences. A linear relationship holds between impact velocity and length and width of delamination. As impact velocity is increased, the increase of delamination length is highger than the increase of delamination width.

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THERMAL EFFECTS ON THE STRAIN ENERGY RELEASE RATE FOR EDGE DELAMINATION IN CRACKED LAMINATED COMPOSITES

  • Soutis, C.;Kashtalyan, M.
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2001.04a
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    • pp.1-6
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    • 2001
  • In this paper, edge delaminations in cracked composite plates are analytically investigated. A theoretical model based upon a sub-laminate approach is used to determine the strain energy release rate, $G^{ed}$, in [$\pm$$\theta_m$/$90_n$]$_s$ carbon/epoxy laminates loaded in tension. The analysis provides closed-form expressions for the reduced stiffness due to edge delamination and matrix cracking and the total energy release rate. The parameters controlling the laminate behaviour are identified. It is shown that the available energy for edge delamination is increased notably due to transverse ply cracking. Also thermal stresses increase substantially the strain energy release rate and this effect is magnified by the presence of matrix cracking. Prediction for the edge delamination onset strain is presented and compared with experimental data. The analysis could be applied to ceramic matrix composite laminates where similar mechanisms develop, but further experimental evidence is required.

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Interlaminar Stress Analysis of the Mechanical Joint of the Composite Materials (복합적층판 기계적 체결부에 대한 층간응력해석)

  • 안용택;송관형
    • Journal of the Society of Naval Architects of Korea
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    • v.40 no.6
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    • pp.49-57
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    • 2003
  • This method surely needs a hole that causes local strength and stiffness deterioration of the structure because of stress intensity. In this work, three dimensional stress analysis of pin-loaded joint for quasi-isotropic composite laminates was performed using commercial finite element software. Stress distribution was calculated near the edge of the pin-leaded hole and effects of the stacking sequence on the delamination were investigated. Also, the delamination strength of the composite laminates was predicted using the Ye-delamination failure criterion and compared with the experimental results. finally, newly modified failure criterion has been suggested owing to the consideration of effects of interlaminar normal stress on the delamination strength.

Evaluation of the delamination strengths in differently processed practical Ag-stabilized REBCO CC tapes under transverse loading

  • Diaz, Mark A.;Shin, Hyung-Seop;Ha, Hongsoo;Oh, Sang-Soo
    • Progress in Superconductivity and Cryogenics
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    • v.21 no.4
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    • pp.34-38
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    • 2019
  • Multilayered high-temperature superconductor coated conductor (CC) tapes are used in an extensive range of applications and are exposed to many stresses such as hoop stress, radial/transverse tensile stress under large Lorentz forces, and thermal stress while cooling if thermal expansion properties differ. Loads induced transversely at the tape surface inevitably create delamination phenomena in the multilayered CC tapes. Thus, delamination behaviors of CC tapes along the c-axis under transverse loading conditions, which can vary based on manufacturing process and constituent layers, must be characterized for applications. The anvil test method was used to mechanically investigate the delamination characteristics of various commercially available Ag-stabilized CC tapes at room temperature and 77 K, finding superior strength at the latter. The wide variations found depended on tape structure and fabrication technique. Fractographic morphologies of delaminated tapes supported the findings under transverse loading conditions.

On the analysis of delamination in multilayered inhomogeneous rods under torsion

  • Rizov, Victor I.
    • Coupled systems mechanics
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    • v.8 no.5
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    • pp.377-391
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    • 2019
  • The present paper is focused on analyzing the delamination of inhomogeneous multilayered rods of circular cross-section loaded in torsion. The rods are made of concentric longitudinal layers of individual thickness and material properties. A delamination crack is located arbitrary between layers. Thus, the internal and external crack arms have circular and ring-shaped cross-sections, respectively. The layers exhibit continuous material inhomogeneity in radial direction. Besides, the material has non-linear elastic behavior. The delamination is analyzed in terms of the strain energy release rate. General solution to the strain energy release rate is derived by considering the energy balance. The solution is applied to analyze the delamination of cantilever rod. For verification, the strain energy release rate is derived also by considering the complementary strain energy.

The Effect of Fiber Stacking Angle on the Relationship Between Fatigue Crack and Delamination Behavior in a Hybrid Composite Materials (하이브리드 복합재료의 섬유배향각이 피로균열 및 층간분리 거동의 관계에 미치는 영향)

  • Song, Sam-Hong;Kim, Cheol-Woong
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.28 no.3
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    • pp.281-288
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    • 2004
  • The hybrid composite material (Al/GFRP laminates) are applied to the fuselage and wing in a aircraft. Therefore, Al/GFRP laminates suffer from the cyclic bending moments. This study was to evaluate the effect of fiber stacking angle on the fatigue crack propagation and delamination behavior using the relationship between crack growth rate (da/dN) and stress intensity factor range (ΔK) in Al/GFRP laminates under cyclic bending moment. The variable delamination growth behavior in case of three different type of fiber orientations, i.e., [Al/O$_2$/Al], [Al/+45$_2$/Al] and [Al/90$_2$/Al] at the interface of Al layer and glass fiber layer was measured by ultrasonic C-scan images. As results of this study, It represent that the delamination shape should turns out to have more effective characteristics on the fiber stacking angle. The extension of the delamination zone in case of [Al/+45$_2$/Al] and [Al/90$_2$/Al] were not formed along the fatigue crack profile. The shape of delamination zone depend on fiber stacking angle and the variable type with the delamination contour decreased non-linearly toward the crack tip at the Al layer.

Influence of Manufacturing Environment on Delamination of Mixed Cross Laminated Timber Using Polyurethane Adhesive

  • SONG, Dabin;KIM, Keonho
    • Journal of the Korean Wood Science and Technology
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    • v.50 no.3
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    • pp.167-178
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    • 2022
  • To investigate the influence of manufacturing environment on bonding performance of mixed cross laminated wood (CLT) using polyurethane (PUR) adhesive, a boiling water soak delamination test according to the temperature and relative humidity was conducted. The 5-ply mixed CLT consisted of Japanese Larch for external and middle layer and yellow poplar for internal layer. The PUR adhesives with different opening times of 10 and 30 minutes were used. The mixed CLT was manufactured according to pressing times of PUR and manufacturing environments of summer and winter. In case of summer environment, the delamination rate of the mixed CLT with pressing time of 4 hours using a PUR adhesive with open time of 10 minutes met the requirements of KS F 2081. In case of winter environment, the delamination rate of the mixed CLT didn't meet the requirements of KS standard. However, it was possible to confirm the effect of improving the adhesive performance by adjusting the pressing time according to the open time of the adhesive under the manufacturing conditions. The delamination rate of CLT with open time 30 minutes PUR, manufactured by indirect moisture supply methods was 11.2% better than direct moisture supply methods. As a result of delamination test in the same condition of relative humidity and adhesive, it was found that the temperature of manufacturing environment influences the adhesive performance.