“…Increasing the actual contact leads to heightened interaction of hard particle in the specimen with asperities of disc surface. However, in contrast to this result, previous researchers have reported that the coefficient of friction of composite brakes decreased with a rise in contact pressure [27,28].…”
Section: Effect Of Contact Pressure and Nbr On Coefficient Of Frictioncontrasting
The aim of this research is to investigate the effect of nitrile butadiene rubber (NBR) as fillers on the mechanical and tribological properties of composite friction brake. Four compositions of specimens, having different NBR volume fractions (0, 4, 8, and 12 %), were manufactured. We assessed their mechanical properties by the three-point bending method according to ASTM D790 standard. We measured their tribological properties under various contact pressures and sliding speeds using a pin on disc tribometer. The results showed that NBR could improve the mechanical properties of composite friction brake materials, and the tribological properties such as wear resistance and friction coefficient increased with increasing NBR volume fraction.
“…Increasing the actual contact leads to heightened interaction of hard particle in the specimen with asperities of disc surface. However, in contrast to this result, previous researchers have reported that the coefficient of friction of composite brakes decreased with a rise in contact pressure [27,28].…”
Section: Effect Of Contact Pressure and Nbr On Coefficient Of Frictioncontrasting
The aim of this research is to investigate the effect of nitrile butadiene rubber (NBR) as fillers on the mechanical and tribological properties of composite friction brake. Four compositions of specimens, having different NBR volume fractions (0, 4, 8, and 12 %), were manufactured. We assessed their mechanical properties by the three-point bending method according to ASTM D790 standard. We measured their tribological properties under various contact pressures and sliding speeds using a pin on disc tribometer. The results showed that NBR could improve the mechanical properties of composite friction brake materials, and the tribological properties such as wear resistance and friction coefficient increased with increasing NBR volume fraction.
“…It consists of 10 wt.% binder for binding all ingredients together, 21 wt.% reinforcing fibres for mechanical and thermal strength, 12 wt.% friction modifiers for controlling friction performance and 57 wt.% fillers either to impart some specific function in the brake-pads or as a space filler. Brake-pads were prepared as per standard industrial procedure discussed in earlier papers 12–14 and shown in Figure 2. Figure 2.Flow chart for the development of brake-pads.…”
The range of thermal conductivity of friction materials is a critical issue since lower thermal conductivity leads to accumulation of frictional heat on the working surface, which results in excessive fade, while higher thermal conductivity leads to excessive heat flow towards back-plate resulting to “spongy brakes”. Therefore, thermal conductivity of the friction materials across the brake-pads should not be high while along the length of brake-pad; it should be high. To enhance the thermal conductivity, metals in the form of powder or fibres are used in the friction materials. Apart from improvement in thermal conductivity, strength and structural integrity, metals get actively involved in controlling the tribo-performance. Their role as improver of thermal conductivity and hence indirectly tribo-performance can never be known clearly. Keeping this in view, it was proposed to design a bulk of pad rather than the surface. Three types of pads with identical composition but differing in the bulk/body were designed by placing a thin fabric layer of Cu (2 mm away from surface) in one pad and two layers in other pad. The third pad did not contain any fabric. The developed pads were characterized for physical, chemical, thermal, and mechanical properties. Tribo-performance was evaluated on full-scale inertia dynamometer by following the JASO C 406 testing standard. It was concluded that Cu fabric inclusion led to improvement in thermal conductivity and heat exaction capacity, which in turn, improved the tribo-performance of pads significantly.
“…In general, four types of raw materials e.g. polymer matrix, fibrous reinforcement, friction modifiers, and fillers are used in multi-phase organic friction composites [6]. The mutual interactions of the raw ingredients both in a positive and negative way influence the overall performance of the composite.…”
New elastomer-modified brake friction composites with the identical composition, but differing in the type of rubber, were developed by altering polar/non-polar elastomeric phases into the phenolic resin matrix. Effect of dispersion and interaction of the polar/non-polar rubbers with the matrix resin on dry sliding wear characteristics of the friction composites was investigated using a laboratory-scale pin-on-disc tribometer. The composites were prepared by hot mixing followed by compression molding and post-curing at a high temperature. Coefficient of friction (COF) and specific wear rate of the composites sliding against a cast-iron disc were measured and analyzed. Polar acrylonitrile-butadiene rubber (NBR, both powder, and bale rubber), and non-polar styrene-butadiene rubber (SBR) and ethylene-propylene-diene monomer (EPDM) were used with the phenolic resin where rubber islands and its polarity played the key role in delayed stress dissipation, while the hard matrix phase contributed to the intrinsic strength of the composites. This work describes how the distribution and interaction of polar and non-polar rubbers with the matrix resin influence the performance of brake friction composites. NBR (powder)-phenolic composite showed the highest stable average COF of 0.52 as compared to 0.36 for EPDM-based composite. NBR (powder)-based composite also exhibited ~1.5 times better specific wear rate (4.9 × 10 −3 mm 3 N −1 m −1) than EPDM-based composite (7.2 × 10 −3 mm 3 N −1 m −1). However, EPDM rubber-based composite showed a significant enhancement in thermal conductivity (0.43 W/m K). Morphological analyses revealed that the dispersion of rubber phase in phenolic matrix played a significant role in transforming the wear mechanism from abrasive to adhesive.
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