This study aims to reduce brake pad thickness and density variations by pressure equalization in the preforming process. Brake pads consist of fillers, lubricants, abrasives, reinforcing fibers, and binders. These are compacted together as raw materials. Each component is responsible for a different specific property to help the brake pad reduce the speed of the vehicle. The forming of a brake pad begins with compression of friction powder in a rigid mold with a complicated contour. It is then compacted by vertically pressing punches to form a body of complicated shape and homogeneous density. The strength of the brake pad, which is a main property in the compacted material, primarily depends on the type of fiber reinforcing material. Since the ability of fiber to flow is poor due to its high internal friction and its random arrangement. These two characteristics cause non uniformity in density and elastic modulus. Pressure equalization is an adjustment of the filling depth of the powder which otherwise would have an uneven fill inf the cavity of the mold. The pressure equalization of the filled powder is shown to correlate with the brake pad dimensional accuracy and uniformity of density.
Evaluation of airborne particle emissions from commercial products containing carbon nanotubes
