Multiscale modeling of nanofiber-filled cross-linked natural rubber composites guided by molecular dynamics simulations

The parameterized modeling method of constitutive equations guided by molecular simulation has attracted widespread attention, in which the microstructural parameters in the constitutive equations are directly calculated through molecular dynamics simulations. Based on this approach, the macroscopic and microscopic transition factor, shear lag theory, and Krenchel orientation parameters are combined to construct the constitutive equations for vulcanized cross-linked natural rubber (VNR) and nanofiber-filled VNR composites considering microstructural parameters. Further, by introducing a non-uniform interface stiffness function, a constitutive equation for nanofiber-filled VNR composites considering the interface debonding damage is constructed. The microstructural parameters of the constitutive equations are obtained from the coarse-grained and all-atomic models. The results show that the predicted values of the constitutive equation of the VNR model coincide well with the experimental stress-strain data under small deformation, while the mechanical responses of the two under large deformation have the same trend of change. Furthermore, the predicted and experimental values of carbon nanotube filled VNR without considering interface debonding damage only have good consistency with the experimental values under small deformation, while the predicted and experimental values of carbon nanotube filled VNR considering interface debonding damage are generally in good agreement. The proposed model may have practical application value for the structural design and performance optimization of nanofiber-filled hyperelastic composites.