Energy Dissipation Mechanism Of Automotive Nanoporous Material Liquid System

Development of new intelligent materials with high energy dissipation density is an important issue for vehicle crash safety. A nanoporous material liquid system(NMLS) is established and investigated here, which is composed of hydrophobic nanoporous materials and liquid. The pressure induced infiltration of liquid into nanopores with ultralarge surface area enables NMLS to be a highly-efficient energy dissipation system, with wide perspective applications such as impact absorbers for vehicles. However, its physical mechanism and engineering application have not been fully studied. In this research, the energy dissipation mechanism of NMLS is experimentally investigated, with emphasis on the liquid infiltration and defiltration behavior in molecular-sized nanopores. The crushing of thin-walled tube structures filled with NMLS is also studied.The liquid infiltration behavior into molecular-sized nanopores driven by external pressure is experimentally investigated. Various kinds of NMLS is made up by using different kinds of nanoporous materials. Parametric studies are conducted on the surface properties of nanopores(by pretreatment) and liquid(by adding electrolyte), as well as pore size(by using multi-pore-sized materials). Their influences on the infiltration pressure are analyzed. Then an equivalent contact angle is proposed based on the classic Young–Laplace equation, and proved to be a reliable quantity to describe the solid-liquid interaction at molecular scale. Besides, a series of drop hammer tests is carried out to obtain the dynamic response of NMLS. It’s found that infiltration mechanism is still valid under impact, and its rate effect is discussed.The liquid defiltration behavior from molecular-sized nanopores upon the unloading of NMLS is experimentally investigated. Different from the infiltration process, defiltration is determined by the interaction among nanopores, liquid and gas molecules in nanopores as well. Through an observation on the rate effect of the defiltration behavior, the influence of gas molecules on the outflow of water molecules is revealed, and its invalidation mechanism is discussed. By silanol introduction and adding electrolyte, the surface properties of nanopores and liquid are modified and their influences on liquid defiltration are analyzed. The defiltration control methods proposed here can improve the recoverability and energy dissipation ability of NMLS.The crush behavior of NMLS filled thin-walled stainless-steel tubes under axial compression is studied by both experiments and finite element analysis. Its mechanical characteristics at various strain rates are investigated by quasi-static tests, drop hammer impact tests and Split Hopkinson Pressure Bar(SHPB) tests. Its energy dissipation mechanism and failure modes are discussed. Besides, a finite element model of NMLS filled thin wall tube is established and validated by experiments. Parametric studies are conducted on its structural and material parameters, and the interaction effect between NMLS and tube wall is revealed. A general rule of designing NMLS filled tube structures is concluded in view of crush force efficiency and energy dissipation density. This will promote the application of NMLS and the development of novel energy absorbers for vehicles.