Functionally graded carbon nanofiber/phenolic nanocomposites and their mechanical properties

For the first time, functionally graded carbon nanofiber/phenolic nanocomposites were designed and fabricated. The effect of compositional gradients on the flexural properties of functionally graded carbon nanofiber/phenolic composite beams was evaluated. Samples with four compositional gradients as well as a non-graded nanocomposite with the same total carbon nanofiber content and geometry were fabricated using a combination of powder stacking and compression molding techniques. Analytical and finite element models were both performed to investigate the effects of compositional gradients, boundary conditions, and external loadings on flexural properties of nanocomposite beams. Close agreement was observed between analytical solutions, finite element analyses and experiment. The morphology of the fracture surfaces was examined using a scanning electron microscope. The results showed that the flexural properties of carbon nanofiber/phenolic nanocomposites can be greatly improved by controlling the carbon nanofiber content across the thickness of the samples.