Sustainable Lemon Juice Treatment of Linaria Tarhunensis Pamp-Fiber: Interfacial Enhancements and Mechanical Performances in Epoxy-Based Composites

This study aims to explore the potential of using Linaria tarhunensis Pamp-fiber, a new and unexplored natural fiber endemic only to Libya as a way to produce sustainable reinforcement for epoxy composites. The surface was treated using green methods with natural lemon juice containing the citric acid to improve fiber-matrix compatibility. Fourier-transform infrared (FTIR) spectroscopy demonstrated chemical modifications of the samples (a decrease in –OH groups intensity in the range of 3400–3200 cm⁻¹, whereas a decrease in hemicellulose/lignin content (1730–1500 cm⁻¹)), suggesting successful esterification and enhanced water resistance of the treated samples. The water absorption experimental results showed that due to better interfacial adhesion, the uptake of water by treated fibers (7.4%) was significantly lower than untreated fibers (9.71%). The VARTM-process composites underwent mechanical tests ultimately showing that lemon juice treated composites have better tensile properties than pure epoxy, having 23% increased strength (7320 MPa) and 21% higher maximum stress (95.15 MPa) due to efficient load transfer and low fiber pull-out. This environmentally friendly cure adheres to green chemistry principles, presenting an inexpensive and harmless alternative to traditional approaches. The results indicate the potential of Linaria Tarhunensis Pamp-fiber as an eco-friendly reinforcement and the efficiency of lemon juice treatment to yield high- performance bio-composite materials that can find applications in automotive, aerospace, and construction industries.