Mechanical properties of nanofiber-reinforced closed-cell foams

In order to investigate the mechanical properties of nanofiber-reinforced closed-cell foams, the micro-geometry structures of closed-cell foams were simulated by Voronoi random foam model, and nanofiber was distributed in cell walls of foams randomly, fiber nodes and matrix nodes were coupled by the improved automatic search coupling (ASC) technology, thus the numerical model which can reflect the micro-structures of nanofiber-reinforced closed-cell foams was established. On the basis, the influence rules of random level of foam model, relative density as well as aspect ratio and mass fraction of nanofiber on elastic modulus and yield strength of nanofiber-reinforced closed-cell foams were investigated further. The results show that the elastic modulus and yield strength of nanofiber-reinforced closed-cell foams obtained by the numerical model established agree well with the experimental values. The increase for random degree of foam model will enhance the elastic modulus and yield strength of composite foams, while after the random degree reaches 0.450, the elastic modulus and yield strength of the materials change little. When the relative density changing in the range of 0.05-0.30, the elastic modulus and yield strength of composite foams almost increase linearly with the increase of relative density. The elastic modulus and yield strength of the materials can also be enhanced by increase the aspect ratio and mass fraction of nanofiber, while the strengthening effect of fiber aspect ratio gradually weakens after fiber aspect ratio achieves 500. The conclusions obtained have significance for the preparation of nanofiber-reinforced closed-cell foams.