Mechanical and tribological response of red brick dust filled hemp-epoxy composites using response surface methodology and machine learning approach.

The current study focuses on the wear and mechanical properties of epoxy-based hybrid composites that contain hemp fiber and red brick dust (RBD). The hand lay-up method is used for making composites using hemp fiber (40 wt%) reinforced epoxy with varied RBD loading up to 15 wt%. The prepared samples are assessed by investigating their physical, mechanical and tribological behavior. The results revealed that the density increased from 1.257 to 1.338 g/cm³ with increasing RBD content, while tensile and flexural strengths decreased by approximately 13.3 and 7.4%, respectively, at 15 wt% filler loading. In contrast, impact strength and hardness improved significantly, showing enhancements of 144 and 152%, respectively, compared to neat epoxy. The sliding wear tests are also carried out in accordance with the L30 model of response surface methodology (RSM). According to reports, the two most important factors affecting the composites' wear rate are RBD content and sliding velocity. The developed RSM models showed good agreement with experimental results, with prediction errors within ± 5%. Additionally, an efficient model for predicting the wear characteristics of the RBD-filled hemp-epoxy composites is developed using three machine learning (ML) models: decision tree (DT), random forest (RF), and gradient boosting machine (GBM). Among them, the GBM model demonstrated superior performance, achieving the highest accuracy with R² values of 0.9542 for specific wear rate and 0.9879 for coefficient of friction, along with the lowest prediction errors. Moreover, the investigation revealed that filler content and normal load are the most important variables affecting the estimation of specific wear rate and COF, respectively.