Effects of walnut shells on friction and wear performance of eco-friendly brake friction composites

Abstract

The paper addresses utilization of 0–14.6 vol.% alkaline-treated walnut shell powders (WSPs) as a functional filler in the proposed eco-friendly brake friction materials. Five non-asbestos friction material samples containing WSP and jute fibers from biomass as biodegradable components were prepared, also including several from natural resources, such as wollastonite, basalt fibers, zircon, barite, and vermiculite. The friction-wear properties of the prepared composites were tested by using Chase friction performance testing device. Furthermore, an extension evaluation method was introduced to rank the composites based on their overall friction-wear characteristics. The coefficient of friction (COF) and wear rate of the samples could be effectively improved, especially for the sample with a WSP content ≤5.6 vol.%. With confirmation of the analysis and characterization results, chars were very possibly formed by the degradation of organic ingredients, such as WSP and jute fibers, which played a key role in affecting the friction performance of the friction composites.