Mechanical and fracture properties of carbon nano fibers/short carbon fiber epoxy composites

This work investigated the influence of carbon nanofibers (CNFs) and aggregate of CNFs with micro-sized short carbon fibers (SCFs) on the mechanical, thermal, and fracture properties of epoxy (80%) - Polylactic acid (PLA) (20%) composite. Epoxy-PLA composite loaded with CNFs (0.2, 0.3, and 0.4 wt.%) and a combination of CNFs and SCFs (0.2 and 0.4 wt.% with equal content of each filler) were manufactured by sonication and manual casting. The synergistic effects of CNFs and SCFs in the epoxy matrix were investigated through mechanical and fracture characterization of nanocomposites. In comparison to CNF-reinforced nanocomposites, the composites reinforced with integrated multiscale fillers have higher tensile, flexural, impact strength, and fracture toughness. Tensile, flexural and impact strength increased by 17.18-25.72%, 39.24-44.07%, and 39.87-97.05% respectively with the incorporation of both CNFs and SCFs into epoxy-PLA matrices. An improvement in fracture toughness in the range of 37.93-38.77% was observed in hybrid nanocomposites in comparison to pristine epoxy-PLA composite. The synergetic mechanism of nano and micro fillers was studied by using the fracture surfaces from tensile tests using scanning electron microscopy. The numerical analysis was also carried out to simulate the effects of filler concentration on the tensile and bending strength of nanocomposites through representative volume element using an ANSYS workbench.