Nondestructive characterization of epoxy matrix composites reinforced with Luffa lignocellulosic fibers

Luffa Cylindrica is a tropical plant from the Cucurbitaceae family, whose fruit becomes very fibrous when fully ripened. The lignocellulosic sponges of Luffa can be suitable for use as reinforcement of epoxy matrix composites, because they have a morphology with spatial 3-D arrangement as well as are eco-friendly mate-rials (biodegradable, and high available) and have economic advantages compared to composites reinforced with synthetic fibers derived from non-renewable sources. Surface modification of the Luffa fibers was car-ried out by hornification and mercerization methods and was verified by Fourier transform infrared spectros-copy (FTIR), scanning electron microscopy (SEM), and X-Ray Diffraction (XRD). For the fabrication of non-biodegradable composites by hand layup technique, the sponges were impregnated with an epoxy resin based on bisphenol in a metallic mold with dimensions 150×200×3 mm³, followed by compression at 5 MPa. The dynamic modulus of the fabricated composites were measured using the nondestructive impulse excita-tion technique (IET), according to the ASTM E1876 standard. Bar specimens with dimensions 80×25×3 mm³ of the laminated composites were tested at room temperature, with Sonelastic® (ATCP) equipment and its associated software. Results showed that the Luffa/epoxy composites has higher loss factor and dynamic modulus when the Luffa fiber is treated before the composite fabrication. The highest Young’s modulus ob-tained was 4.05±0.31 GPa for mercerized Luffa/epoxy. For hornificated Luffa/epoxy composite the highest loss factor and shear modulus values obtained, were 0.0337±0.003 and 1.46±0.13 GPa respectively.