• Title, Summary, Keyword: 파손 강도

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Failure Mode and Strength of Unidirectional Composite Single Lap Bonded Joints II. Failure Prediction (일방향 복합재료 Single Lap 접합 조인트의 파손 모드 및 파손 강도 II. 파손 예측)

  • Yi Young-Moo;Kim Chun-Gon;Kim Kwang-Soo
    • Composites Research
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    • v.18 no.1
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    • pp.1-9
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    • 2005
  • A methodology is presented for the failure prediction of composite single-lap bonded joints considering both of composite adherend failure and bondline failure. An elastic-perfectly plastic model of adhesive and a delamination failure criterion are used in the methodology. The failure predictions have been performed using finite element method and the proposed methodology. The failure prediction results such as failure mode and strength have very good agreements with the test results of joint specimens with various bonding methods and parameters. The influence of variations in the effective strength (that is, adhesion performance) and plastic behavior of adhesive on the failure characteristics of composite bonded Joints are investigated numerically. The numerical results show that optimal joint strength is archived when adhesive and delamination failure occur in the same time.

Failure Mode and Strength of Unidirectional Composite Single Lap Bonded Joints I. Experiments (일방향 복합재료 Single Lap접합 조인트의 파손 모드 및 강도 I. 실험)

  • Kim Kwang-Soo;Yoo Jae-Seok;An Jae-Mo;Jang Young-Soon
    • Composites Research
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    • v.17 no.6
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    • pp.14-21
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    • 2004
  • Failure process, mode and strength of unidirectional composite single lap bonded joints were investigated experimentally with respect to bonding methods, those are, co-curing with and without adhesive and secondary bonding. The co-cured joint specimens without adhesive had the largest failure strength. Progressive failures along the adhesive layer occurred in the secondary bonded specimens. In the co-cured specimens with adhesive film which had better material strength and adhesion performance, delamination failure occurred and the joint strengths were less than those of secondary bonded specimens. Delamination failure did not occur in the secondary bonded specimens because of earlier crack growth and progressive failure in the adhesive layer. Therefore, failure strength of composite bonded Joints were not always proportionate to material strength and adhesion performance of the adhesive due to the weakness of delamination in composite materials. The effects of surface roughness, bondline thickness and fillets were also studied on secondary bonded specimens.

Prediction of Laminate Composite Strength Using Probabilistic Approach (확률분포를 이용한 복합재료의 강도예측)

  • 조영준;강태진;이경우
    • Composites Research
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    • v.13 no.1
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    • pp.33-39
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    • 2000
  • A numerical approach for predicting the ultimate strength of laminate composites has been studied using the Weibull distribution of the strengths of lamina plies. The probabilistic initial failure strengths of laminates were calculated using Tsai-Hill failure criterion. The ultimate strength of the laminate composites has been predicted using progressive failure analysis. The experimental results show that the strength prediction based on the Weibull distribution of ply strength reasonably agrees well with the experimentals better than equal strength assumption.

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Prediction of the Failure Stress of Tofu Texture Using a Delay Time of Ultrasonic Wave (초음파의 지연 시간을 이용한 두부 조직의 물성변화 예측에 관한 연구)

  • Kim, Hak-Jung;Hahm, Young-Tae;Kim, Byung-Yong
    • Applied Biological Chemistry
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    • v.38 no.4
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    • pp.325-329
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    • 1995
  • Changes in the physical properties of soybean curd upon the processing conditions such as coagulant concentration, heating temperature and molding pressure were determined by using a failure stress and residual delay time of ultrasonic wave(5 MHz). Maximum failure stress of Tofu was obtained at the 0.3% $CaCl_2$ coagulant concentration, $95^{\circ}C$ heating temperature and greater molding pressure, respectively, whereas the delay time is inverse proportion to the failure stress value. The results of the multiple regression analysis with factorial design showed that the model equation consisted with delay time and processing conditions gave the good prediction of the Tofu failure stress.

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An Experimental Study on the Strength of Two Serial Bolt-Fastened Composite Joints under Elevated Temperature and Humid Condition (고온다습 조건($82.2^{\circ}C$)에서 2열 볼트 체결 복합재 조인트의 강도에 관한 실험적 연구)

  • Kim, Hyo-Jin
    • Composites Research
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    • v.22 no.5
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    • pp.30-36
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    • 2009
  • The failure strengths and modes in carbon fiber reinforced polymeric composites, with two serial bolt-fastened composite joints, were investigated to evaluate the typical joint configurations of composite components. The parametric studies were performed experimentally at room temperature dry and elevated temperature wet, $82.2^{\circ}C$ on several different laminate configurations. Based on the experimental data presented, two basic load-displacements curves are observed. Each failure mode has the characteristic curve. It is showed that the bearing failure mode occurs in elevated temperature wet condition. It is analysed that the strength of bearing failure mode is not highly depending on the effective modulus of specimen. The failure strength at elevated temperature wet is decreased by the cause of interfacial deterioration between fiber and matrix with moisture absorption.

Failure Load Prediction of the Composite Adhesive Joint Using the Damage Zone Ratio (파손영역비를 이용한 복합재 접착 체결부의 파손강도 예측)

  • Lee, Young-Hwan;Ban, Chang-Su;Choi, Jin-Ho;Kweon, Jin-Hwe
    • Composites Research
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    • v.21 no.4
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    • pp.22-28
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    • 2008
  • The composite joint has become an important research area because the structural efficiency of a structure with a joint is determined by its joints rather than by its basic structure since the joints are often the weakest areas in composite structures. In this paper, the strengths of adhesive joints consisting of metal and composites were predicted and tested by the maximum strain theory and damage zone theory. Nonlinear finite element analyses of adhesive Joints considering the material nonlinearity of the adhesive layer were performed. From the tests and analyses, the strengths of the adhesive joints could be predicted to within 22.2% using the damage zone ratio.

Progressive Failure Analysis and Strength Prediction based on Hashin Failure Criterion of Bolted Composite Joint (Hashin 파손이론을 이용한 복합재 볼트체결부의 점진적 파손 해석 및 강도 예측)

  • Kim, Seongmin;Kim, Pyunghwa;Doh, Sungchul;Kim, Hyounggun;Park, Jungsun
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • pp.936-938
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    • 2017
  • In this paper, the progressive failure analysis of a bolted composite joint which is used in combustion tubes of projectiles and weapon systems is performed. Hashin's failure criterion is considered as fiber tensile failure mode, fiber compressive failure mode, matrix tensile failure mode, and matrix compressive failure mode for this analysis. And this criterion is used to make user subroutine, UMAT. Through the progressive failure analysis we predicted failure strength and compared failure strength with specimen test result.

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Experimental Debonding Failure Behaviors of Composite Skin-Stiffener Bonded Specimens (복합재료 스킨-보강재 접합 시편의 파손 특성에 대한 시험 연구)

  • Kim, Kwang-Soo;An, Jae-Mo;Jang, Young-Soon;Yi, Yeong-Moo
    • Composites Research
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    • v.20 no.6
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    • pp.8-14
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    • 2007
  • Debonding failure characteristics of the composite skin-stiffener specimens were experimentally investigated. The influences of bonding methods, types of stiffener shape and various secondary bonding parameters were evaluated. Present test results combined with the previous test results[1] showed that the failure displacement of the skin-stiffener specimens well evaluates the skin-stiffener debonding failure strength of the composite stiffened panels. The specimens with an open type stiffener had lower bending stiffness and larger failure displacement than those with a closed type stiffener. Secondary bonding and co-curing with adhesive had better failure strength than co-curing without adhesive film. Secondary bonded specimens failed by adhesive failure and co-cured specimens failed by delamination failure. As the bondline thickness was thinner, the skin-stiffener specimens had higher failure strength. The fillets had no influence on failure strength of the specimens. The influence of the surface roughness was shown according to types of stiffener shape.

Size effect on tensile strength of filament wound CFRP composites (필라멘트 와인딩 탄소섬유 복합재의 인장강도 크기 효과)

  • Hwang, T.K.;Doh, Y.D.;Kim, H.G.
    • Composites Research
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    • v.24 no.5
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    • pp.1-8
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    • 2011
  • This paper presents the results of theoretical analysis and experimental test to show the size effect on the fiber strength of filament would pressure vessel. First, a series of fully scaled hoop ring tests with filament would carbon-epoxy were conducted, which exhibited a remarkable size effect on the fiber strength. Next, the failure analyses using WWLM(Weibull Weakest Link Model) and the SMFM(Sequential Multi-step Failure Model) were performed and compared to the hoop ring test data, as well as to unidirectional specimens test data from the literature. It was found that the analysis results significantly underestimated the fiber strengths compared to the test data. In this study, a modified SMFM was proposed through the modification of the length size effect. The fiber strengths from modified SMFM analysis showed good agreement with the test data.

Micromechanical Computational Analysis for the Prediction of Failure Strength of Porous Composites (다공성 복합재의 파손 강도 예측을 위한 미시역학 전산 해석)

  • Yang, Dae Gyu;Shin, Eui Sup
    • Composites Research
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    • v.29 no.2
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    • pp.66-72
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    • 2016
  • Porosity in polymer matrix composites increases rapidly during thermochemical decomposition at high temperatures. The generation of pores reduces elastic moduli and failure strengths of composite materials, and gas pressures in internal pores influence thermomechanical behaviors. In this paper, micromechanical finite element analysis is carried out by using two-dimensional representative volume elements for unidirectionally fiber-reinforced composites with porous matrix. According to the state of the pores, effective elastic moduli, poroelastic parameters and failure strengths of the overall composites are investigated in detail. In particular, it is confirmed that the failure strengths in the transvers and through-thickness directions are predicted much more weakly than the strength of nonpored matrix, and decrease consistently as the porosity of matrix increases.