Establishing the Correlation Between Pore Characteristics and Permeability of Porous Polyimide Based on Micro‐
CT
Huan Tang, Haiyuan Wei, Shaohua Zhang, Ningning Zhou, Yanqiang Hu, Yafeng Zhang ABSTRACT
Effective lubrication of the gyroscope bearing cage directly determines the reliability of the shaft system operation in spacecraft. Capillary transport characteristics of porous polyimide (PI) materials used in the bearing cage are the key to achieving effective lubrication. Permeability, as the core indicator characterizing this property, directly affects the stability of lubricating oil supply. At present, the quantitative correlation between the microscopic pore structure and permeability of porous PI materials is still unclear, and the correlation of “pore characterization – model construction – permeability calculation” that can be used for porous PI cages has not yet been established. This study aims to analyze the intrinsic relationship between the microscopic characteristics of pores and permeability. Firstly, Micro‐CT imaging combined with Avizo three‐dimensional reconstruction technology is adopted to achieve non‐destructive and high‐precision characterization of the internal pore structure of the porous PI. Then, by integrating the pore network model with the ball‐and‐stick model, the system extracts and analyzes the geometric and topological parameters of the pores/larynx, and accurately calculates the tortuosity, permeability and diffusion coefficient. The research results show that as total porosity increases from 0.223% to 0.353%, the pore structure presents a non‐monotonic evolution characteristic of “coarse – fine – re‐coarse”, and the pore connectivity improves simultaneously, gradually approaching a fully connected state. Parameter analysis based on precise calculation of dual models shows that permeability has a very strong negative correlation with tortuosity, a strong positive correlation with pore and throat equivalent radius, and almost no correlation with total porosity. Furthermore, through a systematic analysis of the geometric parameters of pores and larynx, it was found that there is a significant synergistic effect between the two, with a radius correlation coefficient as high as 0.99, while in terms of quantity, there is a significant trade‐off relationship. This study reveals the control mechanism of the microscopic topological structure of porous PI materials on the transmission performance, establishes the pore structure‐permeability correlation analysis, and provides important theoretical support and technical reference for the pore structure optimization and permeability performance regulation of the bearing cage of porous PI gyroscopes.