Mechanical properties of CNT reinforced nano-cellular polymeric nanocomposite foams

Mechanics of CNT-reinforced nano-cellular PMMA nanocomposites are investigated using coarse-grained molecular dynamics simulations. Firstly, static uniaxial stretching of bulk PMMA polymer is simulated and the results are compared with literature. Then, nano-cellular foams with different relative densities are constructed and subjected to static uniaxial stretching and obtained stress-strain curves are used to compute Young moduli and tensile strength of PMMA foams. Carbon nanotubes in various weight fractions and random orientations are then introduced into the constructed samples to investigate effect of reinforcement on mechanical properties of bulk and foam samples. Also dynamic compression experiment at high strain-rate is simulated in all of the samples to check effects of relative density and reinforcement on energy absorption capability and plateau stress. By plotting variation of lateral strain with respect to longitudinal strain, auxeticity of the foams at the early stage of loading was observed. It is shown that there are multiple distinct regimes in stress-strain curves obtained from simulation of compression due to densification of foams during compression. Both recoverable and unrecoverable energies per unit volume in all of the compression experiments are computed and it is shown that reinforcement of foams could result in a lighter structure with improved energy absorption.