In this paper, an elastic constant and Poisson's ratio of the grain or the fiber reinforced composite materials are analyzed by applying the probabilistic technique. The analytical model used is composed of two kinds of elements: the one is made of matrix only and the other contains a grain or fibers. These elements are disposed to make a composite model by using two-dimensional random vectors in order to simulate the condition of an actual material. The finite element method is applied to analyze the deformation behavior of this model.
The numerical calculations to examine the above mentioned technique are performed for the spheroidal graphite cast iron and the glass fiber reinforced plastic. The former is one of the grain reinforced composite materials and the latter one of the fiber reinforced materials. The results on these models coincide with the experimental ones fairly well.