On Optimization of NAO Cu-Free Friction Material Formulation Using Design of Experiments and Taguchi Orthogonal Array

"On Optimization of NAO Cu-Free Friction Material Formulation Using Design of Experiments and Taguchi Orthogonal Array Vishal Reddy Singireddy*, Sai Krishna Kancharla*, Peter Filip* *School of Mechanical, Aerospace and Materials Engineering, Southern Illinois University Carbondale, Illinois Development of novel friction material is a very long, expensive process which also involves rigorous testing. Researchers in the industry often use full-factorial design of experiments to test the influence of each factor and their interactions on the outcome. NAO Cu-free brake pads are made of several ingredients like metals, ceramics, fibers, binder, and rubbers, it would require a very large number of experiments to assess the influence of each individual material (factor) on the performance and mechanical properties of the final product. To overcome this, Taguchi developed a new method which would test factors in pairs instead of individually, thereby lowering the required number of experiments [1]. This research studies the feasibility of using Taguchi orthogonal array and statistical analysis to optimize the formulation of newly developed friction material. Six parameters (Resin type, percentage of resin, abrasives, acrylic fiber, aramid fiber and metal fiber) are studied at two levels (lower limit and upper limit) using design of experiments via Taguchi orthogonal array (L8). Statistical analysis software Minitab is used to create and analyze design of experiments. The sample were then developed accordingly in the laboratory and were tested by adopting the scaled-down SAE J2522 brake effectiveness procedure [2, 3] against surface treated commercially available pearlitic gray cast iron rotors (Waupaca Foundry Inc.) [4, 5] on a Universal Mechanical Tester (UMT, Tribolab by Bruker). Hardness of pads was measured using CV Shore D durometer (ASTM D2240) and density and porosity were measured using Archimedes? principle on a AWS ALX ? 310 precision balance. Wear debris and the friction surfaces of tested samples were analyzed using Scanning Electron Microscopy (FEI, Model: Quanta FEG450) equipped with Energy Dispersive X-ray spectroscopy (EDX, Oxford Instruments). The optimized pads, when tested against coated rotors, were stable at high temperatures (~350?C), and exhibited relatively high (~0.34) and stable friction levels (?? ~ 0.05). Wear of rotors (0 g) was also very low. Achieved performance of the optimized sample indicates that Taguchi orthogonal array is a very useful tool in development and optimization of new friction material and, when combine with scaled-down friction tests, greatly reduces the amount of time, and material involved in the development process. [1] Taguchi, Gen'ichi, and Seiso Konishi. Orthogonal arrays and linear graphs. na, 1987. [2] Vishal Reddy, et al., ""Impact of Acrylic Fiber on the Performance of Newly Developed Friction Materials for Vehicles with Regenerative Braking,"" 38th Annual SAE Brake Colloquium (Online and on-demand), Oct. 2020 [oral presentation only] [3] Vishal Reddy, et al., ?On Scaled-down Bench Testing to Accelerate Development of Novel Friction Brake Materials? (to be published) [4] Filip, Peter, and Nathan K. Meckel. ""Wear resistant braking systems."" U.S. Patent 10,895,295, issued January 19, 2021. [5] Filip, Peter, and Nathan K. Meckel. ""Wear resistant braking systems."" U.S. Patent 10,197,121, issued February 5, 2019. "