Highly aligned aramid nanofibrillar nanocomposites for enhanced dynamic mechanical properties

Abstract

Nanocomposites with aligned nanofillers have received significant attention because of their excellent mechanical properties. However, because of the difficulty in identifying interfacial interactions in mechanical responses, the anisotropic dynamic mechanical properties of aligned nanocomposites, especially those with high reinforcement contents, are not fully understood. In this study, aligned aramid nanofiber/poly(vinyl alcohol) (ANF/PVA) nanocomposites with a nanofiller volume fraction of 48% are fabricated by using the swellingassisted stretching method. This method enabled high degree of alignment of the ANF nanofibers with a sheath of PVA matrix. Enhancement of mechanical strength and stiffness is attributed to improvements of interfacial interactions between aligned ANFs and PVA via effective stress transfer. The damping properties are varied by activation of different dissipation modes, such as the stick-slip and reversible matrix-tearing at the interfaces, that are dependent to the loading angle relative to the nanofiber alignment direction. Resultant viscoelastic properties evaluated by the weight-adjusted viscoelastic figure of merits, the combination of stiffness and damping properties, exceed the conventional limit line up to three folds in magnitude. Deepening the understanding of anisotropic dynamic mechanical responses is required for designing aligned nanocomposite materials for mechanical and electronic applications.