A New Method of Mixing Quality Assessment for Friction Material Constituents Toward Better Mechanical Properties

Abstract

Friction materials used for brake lining are highly heterogeneous composites for which the link between formulation, the resulting material properties, and performances is not well understood. Their heterogeneity is induced by the variety of ingredients (morphology, size, properties etc.) and the manufacturing process which includes a succession of steps: mixing, preforming, hot molding, and post-curing. Among these steps, mixing have a great impact on the material microstructure in terms of ingredient distribution and, therefore, on its mechanical properties. However, mastering the mixing process is very difficult, since it is still based on the empirical experience of manufacturers. In this study, a new method and methodology of mixing state evaluation of friction material constituents was developed. First, it consists on studying constituents’ physical properties permitting to facilitate the investigation of mixing state evolution. This investigation includes two steps: binary and multi-constituent mixture study. This work suggests a non-time-consuming image analysis method using two statistical coefficients to evaluate the mixing state, which are Kurtosis and Coefficient of Variation (C.V). The latter enable to describe the mixing quality and state evolution at the surface of the mixing volume as well as to evaluate the mixing time.