Investigation On Energy-absorption Nanomaterials For Lunar Lander And Analasys On Soft-landing Performance

With the deep-going development of “Chang E” project,and the plan of Mars exploration and manned space exploration,conventional energy-absorption materials become difficult to meet the ever-increasing high-demand on small volume,light-weight,and high energy absorption efficiency systems.Recent researches show that nanostructured materials have great potential in energy absorption,due to the excellent mechanical properties such as enhanced surface-to-volume,strength-to-weight,and stiffness-to-weight ratios.Thus,this paper studies mechanical behavior and energy absorption properties of three typical types of nanostructured materials.Then buckypapers and aluminum honeycomb are selected as typical nanostructured and convential energy absorption materials for manned lunar lander respectively and their soft-landing properties are analyzed and compared.The main work done in this paper is as follows:(1)Phase-field method and Cahn-Hilliard equations are adopted to create a nanoporous aluminum model.Scaling laws of some mechanical properties are developed.Comparison of scaling laws amang this material,other nanoporous materials and conventional foam materials provide a better understanding of nanoporous materials.Energy absorption capability and deformation mechanism of nanoporous aluminum are analyzed.The results demonstrate that nanoporous aluminum has high energy absorption density and energy absorption efficiency up to 98%..(2)A nanostructure of buckyballs-filled CNTs(Carbon Nanotubes)is provided for energy absorption.Molecular dynamic simulations are implemented to study the effects of impact energy,number of buckyballs,and size of buckyballs on energy absorption and impact behavior of this nanostructure.The results show that this material is able to absorb over half of the impact energy during a single impact and has extremely high energy absorption density.(3)Single-walled CNT buckypapers are created by “random walk” and a coarse-grained model.Non-equilibrium molecular dynamic simulations are perfomed to investigate the viscoelastic properties.Effects of oscillatory shear strain amplitude,shear frequency,buckypaper's density,and length of individual CNTs on viscoelasticity of buckypaper are investigated respectively.The results show that buckypapers exhibit linear viscoelasticity and possess high energy dissipation capability,thus providing theoretical basis for crashworhiness.(4)Impact simulations of buckypapers are performed to investigate propagation of impact wave,deformation mechanism,and energy absorption capability.The effects of impact energy,buckypaper's density,and length of individual CNTs on energy absorption performance are also analyzed.The results show that buckypapers have capability of large plastic deformation,high energy absorption density and high energy absorption efficiency near 100%.Besides,energy absorption density of a buckypaper can be further improved by enlarging its density.(5)Inheriting the configuration of the landing gear system of lunar lander of “Chang E 3”,technical index and critical geometric parameters for soft-landing of manned lunar lander are determined.Buckypapers and aluminum honeycomb are selected as typical nanostructured and convential energy absorption materials respectively for manned lunar lander and the soft-landing properties of the two lunar landers are analyzed and compared.The results show that the mass of buckypapers needed for energy absorption is 52.71%(8.14 kg)less than that of aluminum honeycomb.And the lunar lander adopting buckypapers exhibits better soft-landing performance.This research provides valuable insights to the design of landing gear system of future manned lunar lander for our country.