This is a law applicable to composite materials. It allows for the prediction of properties when two materials or more are put into a system. e.g. in Fibre Reinforced Polymer matrices. The equation is as follows: -

X_c=X_mV_m + X_fV_f

where: -

• X represents the property of the material, e.g. Density
• V represents the Volume fraction of the material
• m represents the matrix material, e.g. Epoxy
• f represents the reinforcement
• c represents the composite material