The pigeon pea (PP) stalk is a sustainable lignocellulosic material left by the farmers after harvesting its pulses. The use of agricultural residue in the development of polymer composites is a step towards sustainability. This study focuses on developing and characterizing the mechanical properties (the tensile, flexural, interlaminar shear, compression, impact, and hardness) of less utilized agro-based PP stalk particle reinforced epoxy composites and their hybrid composites. In addition, the density, dynamic mechanical analysis, water absorption, and morphology were also investigated for a better understanding of these composites. In comparison to other agro-residue reinforced composites, PP stalk particles (up to 20 wt.%) reinforced epoxy composites have demonstrated comparable mechanical, viscoelastic, and water absorption characteristics. Jute/PP/epoxy and glass/PP/epoxy hybrid composites outperformed PP/epoxy composites in mechanical, dynamic, and water absorption characteristics. The ranking of the composites based on the characterization was done using the TOPSIS method, and glass/ PP/epoxy composite with a 20 wt.% was identified as the best performer among all the composites. The results demonstrated that PP stalk particle reinforced composites are a viable alternative to wood and other natural fiber-based composites and could be used in lightweight structural applications such as automotive interiors, furniture, packaging containers, and cascading applications.

The current research explores the possibility of reinforcing massively available, less utilised, low-cost agro-residue fibres in an epoxy matrix to create a new tribo-material. This study focuses on determining the three-body abrasive wear behaviour (volume loss and specific wear rate (SWR)) of natural cellulosic pigeon pea (PP) stalk fibre reinforced epoxy composites. Further, abrasive wear characteristics of untreated and treated E/PP20 (20 wt.% PP stalk fibre-reinforced epoxy) composites were analysed using Taguchi and ANOVA techniques. Untreated and treated biocomposite specimens were developed using the hand lay-up (open mould) technique. At 11.77 N, 23.54 N, and 47 N loads, the SWR of untreated E/PP20 composite was reduced by almost 5.03%, 3.68%, and 22.30% when compared to epoxy specimens. Results of the untreated E/PP20 composite showed that the applied load was the main contributing parameter (54.72%) followed by sliding distance (21.82%) and sliding speed (15.31%). Results of the treated E/PP20 composite showed that the applied load was the main contributing parameter (48.96%) followed by sliding speed (26.24%) and sliding distance (20.78%). The regression model predicted the SWR with a pooled error ranging from 2.37% to -17.77% for untreated composite and 9.87% to -11.49% for treated composite respectively. The alkali-treated E/PP20 composite exhibited better abrasive resistance than the untreated E/PP20 composite. Scanning electron microscopy images of the treated composites showed good fibre adhesion with the matrix. In addition, the surface of the treated composite showed no fibre pullout or ploughing compared to that of the untreated composite. Surface topography revealed the formation of more craters on the surfaces of the untreated composites and small-sized dispersed craters on the treated composites.

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