1. A computerized method for creating a two-dimensional finite element model of a rubber composite of a rubber matrix and fillers, comprising: a first step in which a region of the rubber matrix and a plurality of regions of the fillers are defined in a predetermined two-dimensional space, and coordinates of these regions defined are stored in a memory of a computer, a second step in which, with the computer, each of the rubber matrix's region and the fillers' regions is divided into a plurality of triangular elements to define a two-dimensional primary finite element model of the rubber composite, wherein the two-dimensional primary finite element model consists of the triangular elements only, and with respect to the total number of the triangular elements of the two-dimensional primary finite element model, at least 95% of the triangular elements each have a longest side whose length is L 4 a and a shortest side whose length is L 4 b , and a length ratio L 4 a /L 4 b is not more than 2, a third step in which, with the computer, each of the triangular elements of the two-dimensional primary finite element model is subdivided into three quadrilateral elements to define the two-dimensional finite element model made up of the quadrilateral elements only, and a fourth step in which a computer simulation utilizing the defined two-dimensional finite element model made up of the quadrilateral element is performed to obtain and display a relationship between stress and elongation of the rubber composite.