Development and multifunctional characterization of lemon peel biochar filled pineapple leaf fiber reinforced lightweight composites

Abstract This study examines the influence of lemon peel-derived biochar on the mechanical, thermal, and physical properties of pineapple leaf fiber (PALF)-reinforced polyester composites. Alkali-treated PALF served as the primary reinforcement, while biochar, produced via slow pyrolysis at 500 °C and sieved to below 75 µm, was incorporated at 0, 5, 10, 15, and 20 wt.% using the hand lay-up method. Mechanical testing revealed that the composite with 10 wt.% biochar exhibited the highest performance, with hardness increasing from 72.133 Shore D in PALF-B0 to 77.040 Shore D in PALF-B10, tensile strength from 42.530 MPa to 52.317 MPa, flexural strength from 58.307 MPa to 68.807 MPa, shear strength from 24.163 MPa to 29.327 MPa, and impact strength from 3.733 kJ m −2 to 4.201 kJ m −2 . Thermal stability improved, with mass retention at 400 °C increasing from 27.58 % to 47.8 %. Water absorption decreased from 10.42 % to 7.88 % after 28 days. SEM analysis revealed uniform filler dispersion and strong fiber–matrix bonding at 10 wt.%, while higher loadings caused agglomeration and reduced properties. The findings identify 10 wt.% lemon peel-derived biochar as optimal, offering a sustainable method for converting agro-waste into high-performance, lightweight composites suitable for various engineering applications.