Taguchi Method Optimization of Water Absorption Behavior by Wheat Straw-Basalt Hybrid Brake Pad Composite

The application of biomass-derived composite material is in high demand worldwide in various commercial sectors, including automotive, due to its durable, cost-effective, and environment-friendly characteristics. However, one of the limiting factors of biomass-based composites is its higher water absorption capacity compared to commercial synthetic composites. Therefore, this study aimed to optimize the water absorption capacity of biomass-based, wheat straw fiber-basalt hybrid composite brake pad using the Taguchi method by considering the particle size and volume % of the composite compositions. The composite synthesized in this study carried two variations of particle sizes of basalt, wheat straw, steel, river sand, and graphite, as well as two-volume percentages of epoxy resin for optimization. All composites were molded using a compression molding process at compressive pressure of 6 MPa for 2 h curing in a forced convection oven at 100 °C. Water absorption capacity has been determined according to ASTM D570. The wheat straw fiber has been chemically treated with 5 wt.% of sodium hydroxide (NaOH) to remove the impurities, lignin, and hemicellulose and increase the surface area of the fiber, resulting in a larger area of contact between the fiber and the matrix. Elemental analysis, crystallinity, morphology, and mechanical strength of wheat straw fiber-based composites have been determined by XRD, SEM, and compression tests, respectively. The statistical method, analysis of variance (ANOVA), was implemented for Taguchi optimization of the composite compositions. The maximum compressive strength and minimum and maximum water absorption capacity of composites were obtained as 77 MPa, 3.55%, and 26.86%, respectively. From the optimum setting of the confirmation experiment, the optimal water absorption value of 5.718% has been obtained. The optimum particle size of the composite compositions was 1 mm basalt particle, 0.5 mm wheat straw fiber, 1 mm steel particle, 1 mm river sand, 0.5 mm graphite dust particle, and 30 vol% epoxy resin by Taguchi method. The parameter impact of Taguchi ranking on water absorption capacity presented the maximum improvement of water absorption, 10.47%, with river sand particle size.