Minoru Taya

Effective thermal conductivity of a misoriented short fiber composite

This paper examines the effective thermal conductivity of a misoriented short fiber composite. The analysis is based on the equivalent inclusion method for steady‐state heat conduction in composite which we have recently proposed. The present approach is unique in that it takes into account the interaction among fibers at different orientations. Closed form solutions are given for the thermal conductivity of a misoriented short fiber composite. Then, numerical results are presented to demonstrate the effects of volume fraction, fiber aspect ratio, and distribution function of fiber orientation on the thermal conductivity.

Stress Field in a Coated Continuous Fiber Composite Subjected to Thermo-Mechanical Loadings

The stress field in a coated continuous fiber composite subjected to thermo- mechanical loadings is calculated by use of four concentric circular cylinders model. The target material is Ni- or SiC- coated graphite fiber/6061 Aluminum composite. Ni coating is found to be advantageous over SiC-coating from the crack resistance view point.

On two kinds of ellipsoidal inhomogeneities in an infinite elastic body: An application to a hybrid composite☆

Abstract The problem of two kinds of ellipsoidal inhomogeneities embedded in an elastic body is formulated with an application to a hybrid (three-phase) composite. The analytical tool used in this study is a combination of Eshelbys equivalent inclusion method[1] and Mori-Tanakas back stress analysis[2], and therefore the results are valid for large volume fraction of inhomogeneities. As a demonstration, two types of hybrid composites are examined: (i) fiber-fiber; and (ii) fiber-particulate systems.

A Self-Consistent Approach to the Elastic Stiffness of Short-Fiber Composites

The self-consistent approach originally proposed by Hill has been adopted to derive the effective elastic stiffness constants of unidirectional short-fiber composites. The short-fibers are modeled as ellipsoidal inclu sions uniformly distributed in the matrix and the transverse isotropy of the composite has been taken into account. The method of analysis is valid for multi-component systems and hence, applicable to hybrid composites. Comparisons of this analysis with existing theories are made for binary composites.

ON STIFFNESS AND STRENGTH OF AN ALIGNED SHORT-FIBER REINFORCED COMPOSITE CONTAINING PENNY-SHAPED CRACKS IN THE MATRIX.

A model study is conducted on the prediction of the stiffness and fracture toughness of an unidirectional short-fiber reinforced composite containing numerous cracks in the matrix. It is assumed in our model that short-fibers are aligned in the uniaxial loading direction and that cracks in the matrix are perpendicular to the loading axis and are penny-shaped. Then the longitudinal Youngs modulus of the composite weakened by those cracks and the energy release rate of a representative penny-shaped crack are com puted by a combination of Eshelbys equivalent inclusion method and Mori- Tanakas back stress analysis. The interaction between fibers and that be tween fibers and cracks are taken into account by Mori-Tanakas back stress analysis. Hence our results are valid even for a large volume fraction of fiber and crack.

Work of fracture of unidirectional metal matrix composites subjected to isothermal exposure

Work of fracture, γF, was measured on as-fabricated and isothermally exposed unidirectional boron fibre reinforced 1100 aluminium composites. Then an analytical study was made to predict γF of unidirectional metal matrix composites with the special emphasis on the thermally degraded composites. In the analytical study the statistical data on the strength of the fibres that were extracted from as-fabricated and thermally exposed composites were used. A good agreement between the experimental and analytical results of γF was obtained for the entire range of exposure time. It was found in this study that the toughness of the thermally exposed composite decreases with the increase in the exposure time.

Effects of fiber-end cracks on the stiffness of aligned short-fiber composites

Abstract The longitudinal Youngs modulus of an aligned short-fiber reinforced composite with fiber-end cracks extending into the matrix is predicted theoretically in this paper. The analytical technique is based upon a modified Eshelbys equivalent inclusion method where infinite number of three kinds of ellipsoidal inhomogeneities are embedded in the matrix. The results indicate the importance of two parameters in affecting the stiffness of the composite: the size of the fiber-end crack, and the ratio of the number of fibers with fiber-end cracks to the total number of fibers.

Prediction of failure modes in unidirectional short-fibre composites

In short-fibre reinforced composites, penny-shaped cracks often initiate from fibre-ends and propagate into the matrix until they are arrested by the neighbouring fibres. A theoretical study on the prediction of failure modes after the arrest, that is, either the penetration of the crack into the fibres or the debonding of the matrix-fibre interface, is performed. The analytical method used in this study is the extension of the two-dimensional model of Kendall to the three-dimensional crack problem. Strain energy release rates for the initiation of the cracks of the penetration and debonding types are calculated. Also computed are the total potential energy required for a complete penetration of the crack through the fibre diameter and a complete debonding of the matrix-fibre interface. Based on these computations, the failure modes of the crack arrested by the neighbouring fibres are discussed.

Macroscopic fracture surface energy of unidirectional metal matrix composites: experiment and theory

A method of measuring the macroscopic frature surface energyγF is studied and its verification is made compared with the theoretical prediction. Metal matrix composites used in the experiment are unidirectional graphite fibre-reinforced 6061 aluminium. A good agreement between the experimental and theoretical results is obtained.

Growth of a debonded void at a rigid secondary particle in a viscous metal

When a ductile two-phase material is subjected to a high strain-rate deformation, the secondary particles nucleate voids, which will grow and coalesce, in a viscous matrix, leading to a dynamic ductile fracture. If the secondary particle is strong, the void nucleates at the matrix—particle interface and will grow without the shattering of the secondary particle. In this paper the growth of a debonded void at the secondary particle in a viscous metal has been studied theoretically in order to simulate the dynamic ductile fracture of two-phase materials. It has been assumed that the matrix is viscous and that the second-phase consists of randomly-dispersed rigid spherical particles. The analytical technique used in our study is a combination of the equivalent inclusion method of Eshelby and the back stress analysis method of Mori and Tanaka, by which the interaction between debonded voids are accounted for; hence the results presented are valid even for large volume-fractions of debonded voids. The theoretical results obtained in this study are compared with those for the case of complete voids nucleated by the shattering of weak particles.