For two porous components A and B in welded contact, the volume fractions of the components vA, vB satisfy
v_A + v_B = 1, while the overall porosity is given by
= v_A_A + v_B_B,
where are respectively the porosities of the porous constituents
A and B.
The fractions of the total volume occupied by the solid components are
and
, respectively.
The solid components in A and B are individually pure, so that each
porous constituent may be thought of as a microhomogeneous (or Gassmann) material.