Sage Journals: Discover world-class research

Abstract

The variation of the effective moduli in encapsulated fiber composites, which consist of anisotropic phases, is presented in this paper. The strain energy rate released by an edge crack in a rectangular composite thin sheet was evaluated and provided information for the toughness of the material prior to fracture. A typical composite mate rial was macroscopically assumed as a transversely isotropic medium, whereas the repre sentative volume element used for its description is formed by a cylindrical fiber of either a transversely isotropic, or a purely isotropic material, a transversely isotropic cylindrical annulus as coating of the fiber, and an annulus of the matrix covering the encapsulated fiber. The matrix consisted either of isotropic or transversely isotropic material, which is further surrounded by the equivalent composite, which averaged the actual properties of the bulk of the composite containing the dispersed encapsulated fibers. Solutions for the longitudinal and transverse elastic moduli E_Lc and E_Tc as well as the shear moduli G_Lc and G_Tc of the composite are defined in a closed form. Their variation in terms of the relative extent of the matrix is also evaluated. Finally, interesting information concerning the vari ation of the elastic stiffness of the composite due to anisotropy of the matrix was found. Furthermore, the strain energy density released by an edge crack in a rectangular compos ite sheet was determined for the various models with anisotropic fibers or matrices studied in this paper.

Get full access to this article

View all access options for this article.

References

Matonis, V.A. 1969. "An Analytical Evaluation of a Hypothetical 3-Phase Material," Polymer Engng. Sci. , 9:100-108.

Broutman, L.J. and B.D. Agarwal. 1974. "A Theoretical Study of the Effect of an Interfacial Layer on the Properties of Composites," Polymer Engng. Sci. , 14(8):581-588.

Arridge, R.G.C. 1975. "The Effect of Interlayers on the Transverse Stresses in Fiber Composites," Polymer Engng. Sci. , 15(10):757-760.

Mikata, Y. and M. Taya. 1985. "Stress Field in a Coated Continuous Fiber Composite Subjected to Thermo-Mechanical Loadings," Jnl. of Composite Materials, 19:554-578.

Christensen, R.M. 1979. "Effective Moduli of Cylindrical and Lamellar Systems," in Mechanics of Composite Materials. New York: J. Wiley, pp. 73-105.

Kerner, E.H. 1956. "The Elastic and Thermoplastic Properties of Composite Media," Proceedings of the Physical Society of London, 69:808-813.

Theocaris, P.S. 1987. "The Mesophase Concept in Composites," Polymers/Properties and Applications, Series, No. 11. Berlin: Springer Verlag.

Theocaris, P.S. and C.B. Demakos. 1988. "The Effect of Coating on the Stiffness and Toughness of Encapsulated Fiber Composites," Colloid and Polymer Science, 266:1110-1125

, see also: Theocaris, P.S. and C.B. Demakos. 1992. "The Influence of the Elasitc Properties and Dimensions of the Coatings on the Stiffness of Encapsulated Fiber Composites," Composites Science and Technology , 45(4):293-305.

10.

Timoshenko, S.P. and J.N. Goodier. 1970. Theory of Elasticity, Third Ed. Tokyo: McGraw Hill Co.

11.

Eshelby, J.D. 1956. "The Continuum Theory of Lattice Defects," in Progress in Solid State Physics, Vol. 3 F. Seitz and D. Thrnbull , eds., New York : Academic Press, pp. 79-144.

12.

Sih, G.C. and H. Liebowitz. 1968. "Rectilinearly Anisotropic Bodies with Cracks," in Fracture, Vol. 2, H. Liebowitz , ed., New York and London: Academic Press, pp. 108-131.

13.

Bowie, O.L. 1973. "Solutions of Plane Crack Problems by Mapping Technique," in Methods of Analysis and Solutions of Crack Problems, Vol. 1, G. C. Sih , ed., Leyden: Noordhoff International Publishing , pp. 1-55.

14.

Theocaris, P.S. and T.P. Philippidis. 1985. "Theoretical Evaluation of the Extent of the Mesophase in Particulate and Fibrous Composites," Journal of Reinforced Plastics and Composites, 4:173-185.

15.

Griffith, A.A. 1920. "The Phenomena of Rupture and Flow in Solids," Philosophical Transactions of Royal Society of London, Series A, 221:163-198.

16.

Theocaris, P.S. and A.G. Varias. 1987. "The Shear Modulus in the Fiber Direction of Unidirectional Fiber Composites Based on the Concept of Mesophase," Rheologica Acta, 26:322-327.

17.

Hashin, Z. and B.W. Rosen. 1964. "The Elastic Moduli of Fiber-Reinforced Materials," Jnl. of Applied Mechanics, 31:223-232.

18.

Agarwal, B.D. and J.N. Narang. 1977. "Strength and Failure Mechanism of Anisotropic Composites," Fibre Science and Technology , 10:37-52.

The Anisotropy Effect on the Stiffness and Toughness of Encapsulated Fiber Composites

Abstract

Get full access to this article

References