Experimental investigation of the permeability of a tribo-contact in dry friction clutches

The effect of the first order phase transition from solid organic material to gas on fading in dry clutches has been discussed recently. In the present paper the permeability of the contact layer being one of the key parameters determining if the sufficient gas cushion can occur, is measured for friction linings commonly used in the automotive industry. It is shown that the permeability at 20 °C is too high. Chemical analysis shows that fluid compounds with high viscosity occur while heating the lining material alongside with gas. Further experiments indicate that the gas permeability of the contact decreases rapidly in presence of a viscous fluid. This result points out a promising direction for the further investigations of the fading phenomenon.