Sustainable Brake Pad Development: Integrating Micro- and Nano-Sized Ceramic Reinforcements and Carbon Nanotubes for Enhanced Tribological Performance

The development of sustainable, high-performance friction composites is critical for the automotive industry, given the environmental and health concerns associated with conventional brake pad materials such as asbestos and copper. This study investigates the effect of incorporating micro- and nano-sized Al2O3, SiC, and carbon nanotubes (CNTs) into a novel, eco-friendly, asbestos-free, and copper-free brake pad formulation. Six composite samples were fabricated via a cold-pressing and hot-molding process: five formulations containing a single, size-controlled micro-/nano-sized reinforcement (Al2O3, SiC, and CNTs), and one reference formulation (CBP# Reference) containing an unrefined, commercial-grade combination of Al2O3 and SiC in place of the size-controlled additive. All formulations were rigorously characterized for their physical, mechanical, and tribological properties. The nano-Al2O3 formulation exhibited the highest density (2.197 g/cm3) and compressive strength (249.7 MPa), while the micro-SiC formulation achieved superior wear resistance, recording the lowest weight loss (0.0053 g) and the highest hardness (90 HV). The nano-SiC formulation offered the most balanced overall performance, combining high hardness (86.2 HV) with the highest average friction force (33.65 N) and the most stable friction-time response among all samples. The CNT-reinforced formulation produced the highest maximum friction force (42.07 N) but showed only moderate improvement in density, hardness, and compressive strength relative to the ceramic-reinforced samples. Compared with the CBP# reference, all five developed formulations exhibited higher hardness and coefficient of friction alongside lower weight loss, confirming their potential as durable, sustainable alternatives for automotive brake friction applications.