Scientific Experiences in Mechanical Engineering

Abstract
This research looks into the tensile, impact, and Fourier Transform Infrared Spectroscopy (FTIR) characteristics of hybrid composites reinforced using alkali-treated coconut coir fibers and pine fruit peel powder in an epoxy resin matrix. Coconut coir fibers were extracted using a four-day water retting method and then treated with 3 wt.% NaOH for 2 h to increase fiber-matrix interfacial adhesion. The volume fractions of coconut coir fibers (CF) (5%, 10%, and 15%) and pine fruit peel powder (SP) (10%, 20%, and 30%) were varied to form hybrid composites. The CF5/SP10 composite demonstrated the maximum tensile strength (25.61 MPa) and impact strength (46.5 kJ/m²) in the study. The CF15/SP20 composite has the highest modulus of elasticity (1.46 GPa). Increasing the fiber and filler contents over the optimal level often decreased mechanical performance caused by reinforcement agglomeration, insufficient matrix wetting, and the creation of stress concentration sites. FTIR examination revealed the existence of cellulose, hemicellulose, lignin, and epoxy functional groups. The lower intensity of hydroxyl-related absorption bands demonstrated that alkali treatment improved fiber-matrix compatibility. These studies show that coconut coir fiber and pine fruit peel powder can be used as sustainable reinforcements for lightweight engineering composites.

Keywords: Coconut coir fiber; Pine fruit peel powder; Hybrid composite; Tensile strength; Impact strength