The Irradiation Study On Micro-macro Erosion And Mechanical Properties Of PDMS/PI Material

In the Low Earth Orbit(LEO)environment,Factors such as Atomic Oxygen(AO)erosion,ultraviolet irradiation,high and low temperature cycles,space debris and charged particle irradiation can cause mass loss,surface denudation and mechanical degradation of Polyimide(PI)materials and coating materials such as polydimethylsiloxane.Based on Molecular Dynamics(MD),the erosion characteristics and mechanical properties of polyimide(PI)and its Polydimethylsiloxane(PDMS)materials at the nanoscale under atomic oxygen erosion,ultraviolet irradiation and high and low temperature cycling were considered.Secondly,through the mesoscopic statistics of the reaction probability,input physical quantities are provided for the dynamic evolution of micro-and centimeter-scale macroscopic erosion morphology based on Monte Carlo(MC)method,and the research idea of the microscopicmicroscopic-macroscopic erosion characteristics and mechanical properties of PI and its coating materials in the irradiation environment is established.The details are as follows:Firstly,the effects of atomic oxygen erosion on the composition,mass and mechanical properties of PI and PDMS/PI were studied based on molecular dynamics method.Reaxff reaction field was used to carry out Molecular Dynamics simulation,considering the oxidation reaction process of AO,PI,and PDMS/PI with a speed of8km/s and an energy of 5e V.Based on oxidation diffusion and reaction mechanism,the changes in composition,temperature and mass during the reaction process were analyzed.The tensile and unloading simulations of polyimide materials with different irradiation times were carried out to analyze the effects of atomic oxygen erosion on mechanical properties such as Young’s modulus and yield strength.Tensile simulation was carried out for PDMS/PI interfaces under different irradiation intensities to explore the influence of atomic oxygen erosion on coating adhesion.Secondly,the composition,mass and mechanical properties of PI and PDMS/PI were considered in coupled irradiation environment such as thermal cycle and ultraviolet irradiation.The influence degree and coupling mechanism of each factor were analyzed by tensile and unloading analysis and interface opening and drawing simulation.Finally,in order to further characterize the macroscopic morphologic changes of materials during the erosion process,the complex physicochemical reaction process was simplified to particle collision behavior based on the reaction probability of single factor and coupled irradiation by molecular dynamics statistics,and the cutting model was constructed by Monte Carlo method.The retrieval method of two-dimensional Monte Carlo model was improved to improve the computational efficiency and fault tolerance rate of the model,and reduce the error with the experimental results.The effects of defect size,protective layer thickness and defect shape on the erosion depth,erosion width and erosion profile under the action of atomic oxygen were analyzed.Based on this,the Monte Carlo method and ray tracing method are considered to construct a three-dimensional cutting model.The prediction of erosion volume and mass loss is consistent with the experimental results,which provides a feasible method for the comparison of macroscopic erosion prediction and experimental results.