Thermal Stress Analysis Methods of Protective Coating on Polymer Surface for Space:A Review
Flexible polymer materials,which are key materials for spacecraft surfaces,are exposed to the synergistic erosion of ultraviolet(UV)irradiation,ionizing irradiation,and atomic oxygen in the space environment,resulting in material loss and functional failure.Therefore,to achieve long-term service,it is often necessary to prepare protective coatings on surfaces.For most coating materials,during processing,manufacturing,and use,owing to their brittleness,the coating often exhibits a local stress concentration due to temperature changes.With the continuous increase in thermal stress,cracking and spalling occur after exceeding the tensile strength limit,which has become a significant factor affecting performance.Therefore,the analysis of the thermal stress distribution is significant in the design and optimization of coatings.The analysis methods of thermal stress in coatings can be divided into two categories:experimental measurements and finite element analysis based on numerical simulations.Owing to the limitations of a single stress-testing method,limitations in the process of material stress analysis have not been addressed.Therefore,an increasing number of researchers have combined finite element simulations with experimental characterization.Finite element simulations can be used to analyze the theoretical stress distribution of materials under idealized conditions and further optimize the calculation parameters according to environmental conditions,gradually approaching the coating condition under real conditions.Moreover,measuring the actual stress distribution of a material through experiments and matching it with the calculated results effectively solves the problem of calculation reliability.The key factors influencing the material stress can also be effectively understood by analyzing the gap between the simulation and measured results.The combination of finite element simulations and experimental measurements has gradually become the most widely used method for analyzing the stress of coating materials.Owing to the mutual restrictions of the flexibility and protection ability of space-protective coatings on polymer surfaces,improving the flexibility of materials while maintaining good protection performance has become a key problem.Therefore,the stress analysis of the coating has become an important direction for improving the coating design.Space-protective coatings,especially inorganic coatings with good protective properties,face complex temperature-cycling environments in the actual space environment,and changes in the temperature field cause different degrees of deformation,cracking,and other failures of coating materials.In addition,the protective coating needs to be processed at a certain temperature during the preparation process,and a change in these temperature fields causes stress problems in the protective coating.However,it is difficult for traditional stress testing methods to effectively characterize the process of stress generation and accumulation without failure.Finite element simulation is limited in that it is difficult to establish environmental and material models in the actual application process.Therefore,by summarizing the current common thermal stress analysis methods,this study aims to analyze the relevant factors affecting the service life of the coating,which will help adjust the composition,structure,microstructure,and other parameters of the material,predict the failure form of the coating and optimize the preparation process of the coating material.By analyzing the advantages and limitations of destructive test methods and non-destructive test methods based on experimental measurements,as well as finite element simulations,this paper further summarizes the improvement of the current commonly used stress analysis methods by combining the two to guide the coating design and develop coating materials with a low-stress structure.This study provides technical support for the lightweight development and long-term reliable service of key coating materials for polymer surfaces.
polymer materials,protective coating in spacethermal stressstress analysis methodfinite element simulation
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