• Title, Summary, Keyword: Brittle Matrix Composites

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Reinforcing Characteristics on Volume and Shape of Ductile Short-Fiber in Brittle Matrix Composites (취성기지 복합재료에서 연성 단섬유의 함유량 및 형상에 관한 보강특성)

  • Sin, Ik-Jae;Lee, Dong-Ju
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.24 no.1
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    • pp.250-258
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    • 2000
  • The reinforcing effects of ductile short-fiber reinforced brittle matrix composites are studied by, measuring flexural strength, fracture toughness and impact energy as functions of fiber volume fraction and length. The parameters of fracture mechanics, K and J are applied to assess fracture toughness and bridging stress. It is found that fracture toughness is greatly, influenced by the bridging stress ill which fiber pull-out is occur. For the reinforcing effects as functions of fiber volume fraction($V_f$ = 1, 2, 3 %) and length(L = 3, 6. 10cm), the flexural strength is maximum at $V_f$ = 1% and both fracture toughness.

Interfacial Evaluation and Microfailure Mechanisms of Carbon Fiber/Bismaleimide (BMI) Composites using Tensile/compressive Fragmentation Tests and Acoustic Emission (인장/압축 Fragmentation 시험법과 음향방출을 이용한 Carbon Fiber/Bismaleimide (BMI) Composites 의 계면 평가와 미세파괴 메커니즘 연구)

  • 김진원;박종만;윤동진
    • Proceedings of the Korean Society For Composite Materials Conference
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    • pp.79-83
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    • 2000
  • Interfacial and microfailure properties of carbon liber/bismaleimide (BMI) composites were evaluated using both tensile fragmentation and compressive Broutman tests with acoustic emission (AE). Since BMI is rather difficult matrix to apply for the conventional fragmentation test because of its too low elongation and too brittle and high modulus properties, dual matrix composite system was applied. After carbon fiber/BMI composite was prepared for rod shape by controlling differing curing stage, composites rod was embedded in toughened epoxy as outer matrix. The typical microfailure modes including fiber break, matrix cracking, and interlayer failure were observed during tensile testing, whereas the diagonal slippage in fiber ends was observed during compressive test. On the other hand, AE amplitudes of BMI matrix fracture were higher than carbon fiber tincture under tensile test because BMI matrix has very brittle and high modulus. The waveform of signals coming from BMI matrix fractures was consistent with AE amplitude result under tensile tests.

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Effect of Interfacial Debonding on the Material Properties of Brittle Matrix Composites (취성기지 복합재료의 물성치에 미치는 계면분리의 영향)

  • 염영진;진민철
    • Composites Research
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    • v.16 no.1
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    • pp.42-49
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    • 2003
  • Brittle matrix composites often have interfacial debonding between the fiber and matrix which may lead to strength and stiffness degradation. The effect of interfacial debonding and fiber volume fraction on the mechanical properties of composite material were studied by using finite element method. Firstly, the modelling of fiber and matrix constituting the composite material was simplified under some assumptions. Traction and displacement continuity conditions were imposed along the boundary of adjacent representative volume elements. In order to obtain the effective material properties of composite material, stiffness constants were inverted. Numerical values of longitudinal moduli in case of perfect bonding were compared with theoretical values obtained by rule of mixtures and yielded consistency. Material properties of composite with large debonding an81e were found to decrease even though the fiber volume fraction increased.

Influence of Oxidation Inhibitor on Carbon-Carbon Composites: 9. Studies on Impact Properties of the Composites (산화억제제 첨가에 의한 탄소/탄소 복합재료의 물성에 관한 연구: 9. 복합재료의 충격특성에 관한 연구)

  • 박수진;서민강;이재락
    • Composites Research
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    • v.16 no.3
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    • pp.41-48
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    • 2003
  • In this work, the effect of molybdenum disilicide(MoSi$_2$) content on the impact properties of carbon-carbon composites(C/C composites) was investigated in the presence of MoSi$_2$. The content of MoSi$_2$ was varied in 0, 4, 12 and 20 wt% on the basis of resin matrix for anti-oxidation properties of the composites under high temperature. As a result, the composites made with MoSi$_2$ resulted in an increase of interfacial adhesion between fibers and matrix, which could improve the impact properties of the composites. Especially, 12 wt% Mosi$_2$ composites showed the highest impact properties in the present system. This was probably due to the existence of brittle-to-ductile transition(BDT) properties of MoSi$_2$ in the vicinity of 90$0^{\circ}C$, resulting from increasing the interfacial adhesion force among fibers, filler, and matrix in the composites.

Carbon Fiber Reinforced Ceramics based on Reactive Melt Infiltration Processes

  • Lenz, Franziska;Krenkel, Walter
    • Journal of the Korean Ceramic Society
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    • v.49 no.4
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    • pp.287-294
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    • 2012
  • Ceramic Matrix Composites (CMCs) represent a class of non-brittle refractory materials for harsh and extreme environments in aerospace and other applications. The quasi-ductility of these structural materials depends on the quality of the interface between the matrix and the fiber surface. In this study, a manufacture route is described where in contrast to most other processes no additional fiber coating is used to adjust the fiber/matrix interfaces in order to obtain damage tolerance and fracture toughness. Adapted microstructures of uncoated carbon fiber preforms were developed to permit the rapid infiltration of molten alloys and the subsequent reaction with the carbon matrix. Furthermore, any direct reaction between the melt and fibers was minimized. Using pure silicon as the reactive melt, C/SiC composites were manufactured with an aim of employing the resulting composite for friction applications. This paper describes the formation of the microstructure inside the C/C preform and resulting C/C-SiC composite, in addition to the MAX phases.

The effect of random spectrum on the fatigue life of hybrid metal matrix composites (랜덤하중이 하이브리드 금속복합재료의 피로수명에 미치는 영향)

  • 김성훈;배성인;송정일
    • Composites Research
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    • v.16 no.6
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    • pp.48-55
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    • 2003
  • This research makes comparisons of empirical fatigue-lives between AC8A A1 alloy and the metal matrix composites(A1/A12O3, A1/A12O3/A12O3p), and also includes comparisons of fatigue-lives between empirical fatigue-lives and estimated fatigue-lives from regular-periodic load testing, AE method to predict fatigue-crack initiation before visible in sight and SEM(scanning electron microscope) photographs of each material. According to the test results of the notched specimen. the fatigue life of the hybrid metal matrix composites and the metal matrix composites, which are more brittle than the base matrix was shorter than that of the base matrix under both types of loads. In addition, the fatigue-life estimated from the damage summation method and that from experiments at random loads were fairly identical.

Thermo-mechanical Properties and Microstructures of $ZTA-Al_2O_3$ Whisker Composites ($ZTA-Al_2O_3$ Whisker계 복합재료의 미세구조 변화에 따른 열적, 기계적 특성에 관한 연구)

  • 이문환;최성철;이응상
    • Journal of the Korean Ceramic Society
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    • v.30 no.6
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    • pp.457-468
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    • 1993
  • In oxide matrix-SiC(W) composites, instability and glassy phase formation due to oxidation at the high temperature and the diffusion of Si, respectively, cause brittle fracture and low reliability for ceramic materials. The mode of contribution in each mechanisms induced by matrix-whisker debonding, varies with the morphology of matrix-whisker interfaces. This work has described the dispersion behaviours and stabilization mechanisms in slip systems, and multiple toughening mechanisms by dint of two second phase different from each other when spherical ZrO2 and chemically stable Al2O3(W) is respectively added in Al2O3 matrix. To obtain complexshaped components, slip casted bodies were sintered at 1$600^{\circ}C$, 2hrs up to 98~99% R.D.. Multiple toughening mechanisms in comparison with theories reported until now will be discussed as a result of the phase analysis of ZrO2 by athermal behaviours and microstructural characterizations as well as measured mechanical properties.

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Numerical simulation of elastic-plastic stress concentration in fibrous composites

  • Polatov, Askhad M.
    • Coupled systems mechanics
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    • v.2 no.3
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    • pp.271-288
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    • 2013
  • In the present study an elastic-plastic strain analysis is carried out for fibrous composites by using numerical modeling. Application of homogeneous transversely-isotropic model was chosen based on problem solution of a square plate with a circular hole under uniaxial tension. The results obtained in this study correspond to the solution of fiber model trial problem, as well as to analytical solution. Further, numerical algorithm and software has been developed, based on simplified theory of small elastic strains for transversely-isotropic bodies, and FEM. The influence of holes and cracks on stress state of complicated configuration transversely-isotropic bodies has been studied. Strain curves and plasticity zones that are formed in vicinity of the concentrators has been provided. Numerical values of effective mechanical parameters calculated for unidirectional composites at different ratios of fiber volume content and matrix. Content volume proportions of fibers and matrix defined for fibrous composite material that enables to behave as elastic-plastic body or as a brittle material. The influences of the fibrous structure on stress concentration in vicinity of holes on boron/aluminum D16, used as an example.

Evaluation on The Fracture Toughness of Chopped Strand Reinforced ALS Matrix Composites (촙트 스트랜드 강화 ALS계 복합재료의 파괴인성 평가)

  • 차용훈;김덕중;이연신;성백섭;채경수
    • Journal of the Korean Society of Safety
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    • v.13 no.1
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    • pp.13-18
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    • 1998
  • It is well known in the fracture mechanics community that the fracture toughness of brittle materials, such as ceramics, can be improved improves significantly when fibers are added into the material. This is because in presence of fibers the cracks cannot propagate as freely as it can in absence of them. Fibers bridge the gap between two adjacent surfaces of the crack and reduce the crack tip opening displacement, thus make it harder to propagate. Several investigators have experimentally studied how the length, diameter and volume fraction of fibers affect the fracture toughness of chopped strand reinforced matrix composite materials. In this paper, matrix used ALS, Arizona Lunar Simulant, types of fiber used carbon steels and stainless steels. To analyze quantitatively fiber reinforced ALS composites, experimental and analytical methods was progressed. Load-displacement curve is used to experimental method, and FEM analysis program using ABAQUS is used analytical method.

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Mechanical Behavior and Fracture Resistance of $SCS6/Si_3N_4$ CFCCs ($SCS6/Si_3N_4$ 연속섬유강화 세라믹 복합재료의 기계적 거동 및 파괴저항평가)

  • Yoon, Yu-Sung;Kwon, Oh-Heon;Jenkins, Michael G.
    • Proceedings of the KSME Conference
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    • pp.658-662
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    • 2001
  • Continuous fiber ceramic composites(CPCCs) having the advantages of ceramics resistance to heat, eroson can be applied in chemical reactors and engine. CFCCs has relatively high stiffness in spite of low weight. In particular, it exhibits greatly increased toughness, which serves to decrease its inherent damage characteristics of the brittle nature of monolithic ceramics. In this wort, tensile and flexural test for SCS6 fiber/ $Si_3N_4$ matrix composites were studied. An objective of this study is to obtain the basic quantities of mechanical properties for tension and flexural test and link these to the fracture resistance behavior. Then, we showed that wok of fracture concept was useful as a method for describing fracture restance behavior of CFCCs.

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