Effects of reinforcing fibers on airborne particle emissions from brake pads

Abstract

The effect of reinforcing fibers in the brake friction material on brake emission was investigated. Fibers made of steel, mineral, cellulose, and aramid were used to reinforce the friction materials, and friction tests were performed using a Krauss-type tribometer in an environmental chamber with an optical particle counter. The results showed that the use of steel fiber and aramid fiber resulted in the highest and lowest brake emissions, respectively. The fibrillation of cellulose and aramid fibers strengthened the friction films on the pad surface and reduced the brake emissions by improving wear resistance, which was promoted by re-embedding of wear debris in the pad surface during sliding. This suggests that airborne particle emission from a brake system could be reduced by reinforcing the friction material with fibrillating fibers. However, the analysis of the settled wear particles in the chamber indicated that the total brake emission could be increased since the large and settled particles from the friction materials reinforced with fibrillating fibers can be resuspended after a collision since they were agglomerated ultrafine particles.