Molecular Origin of the Reinforcement Effect and Its Strain-Rate Dependence in Polymer Nanocomposite Glass

We investigate the molecular origin of mechanical reinforcementin a polymer nanocomposite (PNC) under a glass state via moleculardynamics simulations. The strength of the PNC system is found to bereinforced mainly via reduced plastic deformations of the nanoparticleneighborhood (NN). Such a reinforcement effect is found to decay withan increase in the strain rate. The Arrhenius-Eyring relationis used to analyze its origin. The amplitude of the reinforcementis found to be determined by the difference between the energy barrier(& UDelta;E) for the activation of NN and the work(W) done by the applied stress to conquer that barrier.A larger strain rate is found to result in a larger W and, hence, a weaker reinforcement effect. Such a strain-rate dependenceis verified in the experimental tensile tests of a poly(vinyl alcohol)/SiO2 composite system. These results not only provide a new understandingof the molecular origin of the reinforcement effect in the PNC system,but also pave the way for a better design of the PNC material properties.

Automated summary

We investigate the molecular origin of mechanical reinforcement in a polymer nanocomposite (PNC) under a glass state via molecular dynamics simulations. The strength of the PNC system is mainly reinforced by reducing plastic deformations of the nanoparticle neighborhood. This reinforcement effect decays with increasing strain rate, and the amplitude depends on the difference between the energy barrier for activation of the nanoparticle neighborhood and the work done by applied stress.