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

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