Mechanical enhancement of carbon fiber/epoxy composites based on carbon nano fibers by using spraying methodology

Carbon nanofibers have been utilized increasingly for enhancing the mechanical properties of advanced polymer composites, which include high strength, stiffness, toughness, and through-thickness Properties. The incorporation of nano particles with a high aspect ratio and extremely large surface area into polymers improves their mechanical properties significantly. Although a number of efforts have been made to improve various properties by mixing nano particles directly into resin, however, it could lead to high viscosities which create problems during processing. In this particular study, an attempt has been made to enhance mechanical response of nano composites by using, state of the art, a different technique i.e spraying the Carbon Nano Fibers (CNF) on dry perform before infusion. The nano composite samples were prepared using a spraying methodology i.e dispersing the 1.0 weight percent CNF solution on carbon fabric, and evaporating the solvent such that only nano fibers remain on perform, followed by Vacuum assisted resin transfer molding (VARTM). Tensile, compression, flexural and short beam strength tests were performed to evaluate the effectiveness of CNF addition on the mechanical properties of carbon/epoxy composites. Results indicated, CNF addition offered simultaneous increase in all these mechanical properties in different percentages i.e 22-28 percent improvement in tensile strength, 7-11 percent in compressive strength, 14-19 percent in Flexural strength and 45-55 percent in short beam strength with respect to the neat composite. The rise in their modulus has also been discussed in detail and part of this study. For in-depth analysis, Microscopic approaches were also carried out to investigate the fracture behavior and mechanism of material. Scanning electron microscopy of fractured surfaces revealed improved primary fiber-matrix adhesion and indications of CNF-induced matrix toughening.