Thermomechanical characteristics of green nanofibers made from polylactic acid: An insight into tensile behavior via molecular dynamics simulation

Abstract

All-atom molecular dynamics simulations are conducted to elucidate the thermomechanical characteristics of polylactic acid nanofibers with a diameter range of 1.93 nm–5.4 nm. Nanofibers undergo tensile deformations from which elastic, yield, softening and fracture phases are recognized and mechanical parameters are evaluated by tracking the stress, energy and geometrical evolutions at each phase. Special attention is devoted to the fracture phase where a new method is proposed to calculate the energy release rate during crack propagation which is a crucial factor in fracture mechanics. The effect of nanofibers' diameter, temperature and the deformation strain rate on fracture properties, moduli of resilience and toughness, yield stress, Young's modulus and Poisson's ratio is studied. Monitoring the variation of the internal energy components during deformation reveals the dominance of bond and van der Waals contributions in the deformation mechanism. Finally, a comparison of nanofiber parameters with that of the bulk polymer shows that compared to the thermal properties, the mechanical parameters are more affected by the confinement of the nanofibers.