Abstract
An isolated thin-coated spheroidal short fiber in an infinite body is modeled by a double inclusion which consists of a nested sequence of two inclusions whose elastic constants are different from each other. By adopting the double inclusion method proposed by Hori and Nemat-Nasser to the present model, the volume averages of stresses induced in and around the fiber under the uniaxial external stress are calculated and compared with the exact value obtained by Mikata and Taya. The present value of the average stress in the thin-coat layer is in good agreement with the exact one at the equators of the thin-coat layer. The Mori-Tanaka theorem is extended to the random distribution of the double inclusions in order to analyze the average interaction stress induced in the matrix and the inclusion, and the modified equivalent expression is derived for the double inclusion. By adopting the modified equivalent expression to the thin-coated fiber-reinforced composites, the stresses in and around the fiber are derived as a function of the volume fraction of the thin-coated fiber and the aspect ratio of the fiber. When the volume fraction of the thin-coated fiber is zero, the stress in the thin-coat layer agrees with that in the isolated thin-coated fiber. The stress in the thin-coated layer decreases with increase in the volume fraction of the thin-coated fiber.
