Cross-scale modeling of energy absorption behavior of nanofluidic systems

To investigate the energy absorption behavior of nanofluidic energy dampers (NEDs) consisting of a water chamber and nanoporous materials, a cross-scale modeling approach integrating molecular dynamics (MD) simulation and finite element method (FEM) is proposed. An isolated-channel model is employed for MD simulations; whereas three FEM models (isolated-channel, multi-channel and unit-cell) are constructed. FEM isolated-channel model parameters, modeling the hydrophobic nanochannel as a cylindrical channel with a linear elastic-perfectly plastic spring, a damper, and a rigid circular lid, are calibrated against MD load-displacement results. Multi-channel model is constructed by parallel assembling cylindrical nanochannels, while unit-cell model is developed via introducing an elastic sealing layer. Simulations show that the FEM isolated-channel and multi-channel models exhibit identical load-displacement curves as their MD counterparts. In contrast, the unit-cell model enables a substantial larger displacement range, which is attributed to the elastic deformation of the sealing layer. Across all FEM models, external work is mainly converted into spring strain energy absorbed by NEDs, which mimics the nanophase liquid energy quantified in MD simulations. Upon unloading, the stored spring strain energy is released and dissipated by the damper, a process that simulates the solid-liquid interfacial friction behavior.