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Key engineering materials
Trans Tech Publications Ltd.
Key engineering materials

Trans Tech Publications Ltd.

半月刊

1013-9826

Key engineering materials/Journal Key engineering materials
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    Fiber Bridging Effect on In-Plane-Shear Mode Crack Extension Resistance of Unidirectional Fiber-Reinforced Composites

    H. SekineS. Kamiya
    19-29页
    查看更多>>摘要：The fiber bridging effect, which affects the crack extension resistance in fibrous composites, is discussed in the case of in-plane-shear mode crack extension parallel to fibers in unidirectional fiber-reinforced composites. We first make a model of the bridging of a single fiber and estimate the force acting on the crack surface through a bridging fiber. Then, introducing the stochastic process of fiber breakage, we obtain the quantitative relationship between the relative crack surface displacement and the equivalent cohesive stress which is the probabilistic expectation of forces acting on the crack surface through a large number of bridging fibers. We numerically simulate the crack extension behavior with the equivalent cohesive stress acting on the crack surface. Then the simulated results are consistent with the experimental results. We finally conclude that the in-plane-shear mode crack extension is greatly affected by the stochastic process of fiber breakage.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Fracture Energy and Fracture Behavior of Short-Fiber-Reinforced SMC Composites

    H. SuzukiH. Sekine
    31-40页
    查看更多>>摘要：A probabilistic fracture model is introduced to clarify the influence of the fiber bundle-matrix interfacial condition on the fracture energy and fracture behavior of short-fiber-reinforced SMC composites. In this paper, we focus on the study of the influences of two parameters of the interfacial condition, i.e., the debond stress and the constant which governs the frictional forces acting on the debonding interfaces between fiber bundles and matrix in a debonding process, and then the influences of these parameters on the fracture energy and load-displacement curve are elucidated.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Fracture Toughness of Whisker Reinforced Ceramics

    M. KatagiriA. KumakiY. IzumiH. Suzuki...
    41-46页
    查看更多>>摘要：By use of a probabilistic fracture model, a numerical simulation method for deformation and fracture behavior of whisker reinforced ceramics is developed first. A crack in whisker reinforced ceramics is regarded as the crack with a cohesive stress acting on the crack surface, and then the tension-softening relation is derived on the basis of a micromechanical study. After the numerical simulation method is constructed by incorporating the tension-softening relation in an FEM scheme, we simulate the load-load point displacement relationship for an edge-cracked bend specimen of a SiC whisker/alumina composite. The fracture toughness determined from the simulated maximum load is consistent with that obtained from experiment.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Load Carrying Capacity of Notched CFRP Laminates

    H. SuzukiS. KinugawaH. Sekine
    47-51页
    查看更多>>摘要：On the basis of a micromechanical study, a method for evaluating load carrying capacity of notched CFRP laminates is developed. The damage zone at a notch tip in CFRP laminates is modeled as a fictitious crack with a cohesive stress acting on the crack surface. Then, applying the Weibull weakest link theory to the strength of surviving fiber bundles on the crack surface, we derive the relationship between the cohesive stress and the crack opening displacement, i.e., the tension-softening relation. By incorporating it in a BEM scheme, the load-displacement relationship is simulated. The simulated result for notched CPRP laminates is compared with experimental ones, and it is found that the simulated and experimental results of load carrying capacity are consistent.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Damage Mechanism and Apparent Fracture Strength of Notched Fiber-Reinforced Composite Laminates

    S. KamiyaH. Sekine
    53-67页
    查看更多>>摘要：Apparent fracture strength of notched fiber-reinforced composite laminates depends on the notch tip radius even if it is evaluated in terms of the local parameters such as the stresses at a notch tip or the stress intensity factors. Although numbers of phenomenological explanations have been made, this phenomenon has not yet been physically clear enough. In order to elucidate its key mechanism, our interest is here focused on the interlaminar crack extension from a notch tip in cross-ply laminates subjected to mode-I loading. We find a stochastically expected upper bound of interlaminar crack length due to the probabilistic breakage process of fibers in load-bearing laminas inside the delaminated zone. This upper bound, i.e., the critical length of interlaminar crack, is inherent to the laminate and corresponds to its notched strength. The well-known variation in apparent fracture strength of notched fiber-reinforced composite laminates with respect to the notch tip radius is clearly explained as the scale effect of this constant critical length in different displacement distributions ahead of notch tips of different radii.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Tensile Strength Deterioration of Short-Glass-Fiber Reinforced Thermoplastics by Addition of a Slight Amount of Inorganic Agent

    H. SekineK. Yamada
    69-81页
    查看更多>>摘要：This paper concerns a micromechanical study of the tensile strength deterioration of short-glass-fiber reinforced thermoplastics by addition of a slight amount of inorganic agent. Tensile tests were conducted using short E-glass fiber reinforced polyamide 6 with a slight amount of the inorganic addition agents TiO_2, ZnO and ZnS. It is found by the tensile tests that the tensile strength decreases with increasing the hardness of the inorganic addition agents, and scarcely depends on the amount of the inorganic addition agents. After measuring the pull-out length of glass fibers on the fracture surfaces of test specimens, the variation of the scale parameter of Weibull moduli is estimated from the cumulative probability of pull-out length. Finally, the tensile strength deterioration is numerically predicted using the data. The predicted values of tensile strength are consistent with the experimental ones.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Effect of Matrix Hardening on Tensile Strength of Alumina-Fiber Reinforced Aluminum Matrix Composites

    T. OkabeM. NishikawaN. TakedaH. Sekine...
    83-99页
    查看更多>>摘要：This paper examines the stress distribution around a fiber break in alumina-fiber reinforced aluminum matrix (Al_2O_3/Al) composites using finite element analysis and predicts the tensile strength using tensile failure simulations. In particular, we discuss the effect of the matrix hardening on the tensile failure of the Al_2O_3/Al composites. First, we clarify the differences in the stress distribution around a fiber break between an elastic-perfect plastic matrix and an elastic-plastic hardening matrix using finite element analysis. Second, the procedure for simulating fiber damage evolution in the Al_2O_3/Al composites is presented. The simulation incorporates the analytical solution for the axial fiber stress distribution of a broken fiber in the spring element model for the stress analysis of the whole composite. Finally, we conduct Monte Carlo simulations of fiber damage evolution to predict the tensile strength of the Al_2O_3/Al composites, and discuss the effect of matrix hardening on the tensile strength of the Al_2O_3/Al composites. Coupled with size-scaling analysis, the simulated results express the size effect on the strength of the composites, which is seen in experimental results.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Stress-Corrosion Cracking in Unidirectional GFRP Composites

    H. SekineP. W. R. Beaumont
    101-113页
    查看更多>>摘要：A micromechanical theory of macroscopic stress-corrosion cracking in unidirectional glass fiber-reinforced polymer composites is proposed. It is based on the premise that under tensile loading, the time-dependent failure of the composites is controlled by the initiation and growth of a crack from a pre-existing inherent surface flaw in a glass fiber. A physical model is constructed and an equation is derived for the macroscopic crack growth rate as a function of the apparent crack tip stress intensity factor for mode I. Emphasis is placed on the significance of the size of inherent surface flaw and the existence of matrix crack bridging in the crack wake. There exists a threshold value of the stress intensity factor below which matrix cracking does not occur. For the limiting case, where the glass fiber is free of inherent surface flaws and matrix crack bridging is negligible, the relationship between the macroscopic crack growth rate and the apparent crack tip stress intensity factor is given by a simple power law to the power of two.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Multi-Scale Analysis of Viscoelastic Behavior of Laminated Composite Structures

    Y. ShibuyaH. Sekine
    115-132页
    查看更多>>摘要：For high temperature applications of laminated composite structures, viscoelastic behavior of laminated composite structures is investigated by multi-scale analysis based on a homogenization theory. Effective viscoelastic properties of the laminas are evaluated by a boundary integral method at a micro-scale level, and viscoelastic analysis for laminated composite structures is performed by a finite element method at a macro-scale level using the effective viscoelastic properties of lamina obtained by the micro-scale analysis. In the multi-scale analysis, the Laplace transformation is adopted and the correspondence principle between elastic and viscoelastic solutions in the Laplace domain is applied. The inverse Laplace transform is formulated by the Duhamel integral, and is calculated numerically. As a numerical example, a laminated composite plate with a hole is treated and the viscoelastic behavior of the laminated composite structure is elucidated.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd