In agiven event the energy absorbed is something like the integral of torque transmitted *rotational slip velocity.
This lost energy is used to heat the lining material, which you may be able to model, and to wear it away, for which you need a wear equation. These do exist, try researching brake calculations. Roughly the enrgy required is related to the particle size, and the UTS of the material in shear.
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.