On Impact of Carbonaceous Components on the Performance of NAO Cu-free Brake Friction Material

"On Impact of Carbonaceous Components on the Performance of NAO Cu-free Brake Friction Material Vishal Reddy Singireddy*, Manisha Upreti*, Sai Krishna Kancharla*, Peter Filip* *School of Mechanical, Aerospace and Materials Engineering, Southern Illinois University Carbondale, Illinois Cu-free NAO brake pads are generally phenolic resin-based polymer matrix composites containing varying amounts of fibrous reinforcements, friction modifiers and various fillers. Carbonaceous components like coke, graphite are the main lubricants (also friction modifiers) used in brake friction material to stabilize the friction levels and support in the formation of friction layer. Research shows that the type of carbon used effects the compressibility and damping capacity of the pads. This study focuses on studying the impact of superior graphite carbon and commercially available graphite on the friction performance of laboratory developed modern NAO cu-free friction material. Two samples with same composition except for the type of carbon, are developed in laboratory. These samples were tested against commercially available gray cast iron rotors (C30, Waupaca Foundry Inc.). A bench-top tester (Tribolab by Bruker) was used to test the brake pair following a scale-down SAE J2522 standard procedure [1, 2]. The sound pressure levels during the harshest steps (section 4.5, 200 to 170 kph at 80 bar) were monitored by a ?? free-field prepolarized microphone (PCB Electronics, Model = 377C01). A DAQ module (NI USB - 6218) was used to collect the data from microphone and MATLAB was used to analyze the data. Scanning Electron Microscopy (FEI, Model: Quanta FEG450) and Energy Dispersive X-ray spectroscopy (EDX, Oxford Instruments) were used to characterize the friction tested surface of the rotor and pad. Sample with superior graphite carbon exhibited relatively high friction levels (0.38 in Fade 1), low wear (0.18 g) and showed relatively stable friction levels (??~0.05) whereas the sample with commercially available graphite exhibited relatively lower friction levels (0.29 in Fade 1), showed thermal fade (??~0.12) but had lower wear (0.14 g). Surface analysis of the tested pads revealed that a continuous friction layer with both uncovered and partially covered, carbon and graphite along with other carbonaceous content is present. This played a crucial role in the formation of friction layer and maintaining stable friction levels. References: [1] Vishal Reddy Singireddy, Rohit Jogineedi, Sai Krishna Kancharla, JV Kingston, Craig Zirkle, Peter Filip ?Impact of Resin Types on Performance of Friction Materials for Vehicles with Regenerative Braking?, SAE International 2020 Brake Colloquium [2] Vishal Reddy Singireddy, Rohit Jogineedi, Sai Krishna Kancharla, Kora Farokhzadeh, Peter Filip ?Impact of Acrylic Fiber on the Performance of Newly Developed Friction Materials for Vehicles with Regenerative Braking?, SAE International 2020 Brake Colloquium "