Molecular dynamics simulation and experimental investigation of mechanical properties of calcium carbonate and graphene reinforced polylactic acid nanocomposites.

Abstract

The use of Molecular Dynamics (MD) simulations to examine the mechanical characteristics of polymer compositesreinforced with calcium carbonate (CaCO3) and graphene (GR) is represented in this work. The effects of CaCO3 andGR nanoadditives in polylactic acid (PLA) matrix in different concentrations were evaluated using the results of MDsimulations. Experimental analyses have been conducted to validate the results of MD based on the mechanicalproperties of fabricated nanocomposites, including modulus of elasticity, shear modulus, and Poisson's ratio. Themodeling, computation, and analysis of several simulations on the improved mechanical characteristics ofPLA/CaCO3 and PLA/GR nanocomposites are introduced and discussed. The results revealed that the addition ofGR nanoparticles were more effective in enhancing the mechanical properties of PLA components as compared withthat of CaCO3 nanoparticles, as the modulus of elasticity, shear modulus and Poisson's ratio increased byapproximately 21%, 17%, and 16% for addition of 3 wt% GR nanoparticles in the PLA matrix, respectively. The mechanical behavior of PLA/CaCO3 and PLA/GR nanocomposites have been simulated based on the moleculardynamic technique using material studio (MS) that enabled the analyses of synergy between the polymer moleculesand the nanoparticles. Molecular models for a system of nanocomposites were built by embedding the nano-clustersinto an amorphous PLA matrix. Nanoparticles have been modeled as spherical nanoclusters of graphite and calciteunit cells. Molecular models of the pure PLA matrix were also developed for comparison. The relaxed systems of MDsimulations have been carried out to calculate the mechanical properties of nanocomposites containing 1, 3 and 5wt% nanofiller contents. To validate the results of the simulations, the PLA/CaCO3 and PLA/GR nanocompositegranules, containing different weight ratios of the nanofillers in the matrix, have been synthesized by melt-blendingtechnique. These granules have been used to produce tensile test samples by injection molding technique, withdifferent fractions of nanoparticles in the matrix, to study the effects of such nanoadditives on the mechanicalproperties of the PLA nanocomposites.