Effective medium approximations

Summary

Effective medium approximations are explicit formulas for the effective property of a composite, such as its conductivity or stiffness. They use the properties and volume fractions of its phases. The exact effective property is defined by homogenization and depends on the whole geometry of the microstructure, so it is rarely computable in closed form. Effective medium approximations replace this geometry by a simple model, for example spherical grains surrounded by an averaged medium. Classical examples are the Maxwell Garnett formula, the Bruggeman formula and the Mori–Tanaka method.