The Porosity-dependence of Bulk Modulus of Dry Porous Materials

By semi-analytical modifications to Mackenzie's equation, a new third-order relation between bulk modulus and porosity is developed for porous materials. Compared with Mackenzie's equation, the proposed equation takes into consideration critical porosity and real geometry represented by the assembly of hollow spheres. It has been shown that the proposed equation is in better agreement with 10 sets of published data than Mackenzie's equation and that has an advantage in predicting the matrix bulk modulus even lack of the data of dense porous specimens. In addition, the proposed equation can describe the bulk modulus of porous materials with critical porosity well. However, Mackenzie's equation cannot work.