Fade and Recovery Behavior of Non-Asbestos Organic (NAO) Composite Friction Materials based on Combinations of Rock Fibers and Organic Fibers

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Abstract
Non-asbestos organic composite friction materials are increasingly used in automotive brake disc pads and clutch facing applications. Loss in braking effectiveness at elevated temperatures (300-400°C) because of reduction in friction coefficient (μ) and the revival of the same at lower temperatures is referred to as fade and recovery, respectively. The present paper deals with the role of binary combination of volcanic rock fibers (either basalt or Lapinus) and organic fibers (either aramid or PAN) on the fade and recovery behavior of friction composites. The fade-recovery behavior of four composites was evaluated following ECE R-90 regulation. The μ-performance, μ-fade, and μ-recovery were significantly influenced by the type of fiber combinations. It was observed that among the rock fibers, basalt was more effective to boost the performance μ than the Lapinus. In the case of organic fibers, aramid was more effective than the PAN in this aspect. The Lapinus fiber-based composites showed higher resistance to wear and friction-fade than the composites based on basalt fiber. The aramid and Lapinus fibers imparted higher resistance to fade and wear than the PAN and basalt fibers, whereas the overall recovery response of the PAN fiber-based composites was higher than the others. Worn surface analysis by SEM has proved to be useful in understanding the wear behavior of the composites.