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 materials (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 carried out by hornification and mercerization methods and was verified by Fourier transform infrared spectroscopy (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 x 200 x 3 mm(3), followed by compression at 5 MPa. The dynamic modulus of the fabricated composites were measured using the nondestructive impulse excitation technique (IET), according to the ASTM E1876 standard. Bar specimens with dimensions 80x25x3 mm(3) of the laminated composites were tested at room temperature, with Sonelastic (R) (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 obtained 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.