Over the last decades, enormous efforts have been devoted to developing energy absorption materials and structures to prevent personnel injuries or key facilities damages. Among many other energy absorbing components, thin-walled structures have been widely used in automotive, aerospace and other industries, due to their light weight, low cost, and easiness to manufacture. To improve the energy absorption performance of thin-walled tubes, metallic foams and polymeric foams are commonly used as the filling material. In this study, a highly compressible liquid filler, i.e. liquid nanofoam (LN), has been introduced into the thin-walled tubes. The LN is composed of two phases, a hydrophobic nanoporous media and a liquid phase. As a critical pressure is reached, the liquid is driven into the nanopores, converting the mechanical energy into the liquid-solid interfacial energy at the liquid-nanopore wall interface. Upon unloading, the excessive interfacial energy is mitigated as other forms of energies, such as heat. It is hypothesized that by using LN as the filling material in thin-walled tube, its energy absorption performance can be significantly improved.

The mechanical response of these LN-filled tubes (LNFTs) has been characterized by quasi-static compression tests and dynamic impacts. The quasi-static compression tests are conducted by an MTS system at a loading speed of 2 mm/s. Results show that the energy absorption capacity of LNFTs is 45% higher than that of identical empty tubes. The strengthening coefficient of LNFTs is found to be larger than 3.5. Micro-CT images show that the liquid-solid interaction at the liquid and tube wall interface improves the performance of LNFT by extending the plastic deformation of the tube wall. Gas gun impact are conducted to characterize the dynamic behavior of LNFTs at an incident speed of 6.7 m/s. The energy absorption capacity of LNFTs is found to be 76% higher than that of identical empty tubes. In addition, the LNFT exhibits an energy absorption efficiency of 0.77, 48% higher than the value of empty tubes. More importantly, as the strain rate is increased from quasi-static condition (10^-2^ s^-1^) to intermediate range (10^2^ s^-1^), the energy absorption capacity of LNFTs is increased by 54% without increasing the working pressure of the system. This is due to is due to the different energy mitigation mechanisms of the LN-filler. The strain rate sensitivity of LNFTs suggests that LNFTs can be used as advanced energy absorber. These findings provide design guidance for liquid nanofoam filled thin-walled structures for vehicle crashworthiness and infrastructure protection.


Liquid-Solid Interaction in Liquid Nanofoam Filled Thin-Walled Tubes Under Quasi-Static and Dynamic Loadings

Division / Sponsors: 
Aerospace, Bioengineering, Applied Mechanics, Design Engineering Division, Advanced Energy Systems, Manufacturing Engineering Division, Noise Control and Acoustics, Nondestructive Evaluation, Diagnosis, and Prognosis (NDPD), Nuclear Engineering Division, Process Industries Division, Fluids Engineering, Heat Transfer, Materials, Microelectromechanical Systems, Safety Engineering and Risk Analysis, Computers & Information in Engineering


Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2020/volume/84478

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