Multiscale Dielectric Constant Simulation Of Quartz Fiber Woven Composites

Quartz fiber reinforced silicon dioxide(SiO2f/SiO2)composite material is a thermal wave permeable material with excellent performance.It has good wave permeability,high temperature resistance,and mechanical properties.It is commonly used as a radar radome for high-speed aircraft,and plays an important role in the field of national defense and security.Its microscopic structure is complex,composed of continuous braided fibers and a large number of pores,and the material properties are easy to absorb moisture,which has a certain influence on the overall dielectric properties of the material.In large-scale simulation of structures such as radar radomes,the complex microstructure of materials can bring high costs to modeling and calculation,making analysis more difficult.According to the equivalent medium theory,in the analysis of electromagnetic problems,if the wave length is larger than the material microstructure size,an inhomogeneous medium with complex microstructure can be equivalent to a homogeneous plate.Therefore,as long as we can obtain the equivalent electromagnetic parameters of quartz fiber reinforced silica matrix composites,it will help reduce the cost and difficulty of related issues in large-scale analysis.This article aims to study the pore structure,moisture adsorption,and possible temperature gradients of materials at high temperatures,and then obtain equivalent electromagnetic parameters to analyze the dielectric properties of materials.Firstly,a reasonable and simplified method is used to establish a fiber woven structure model,and a random distribution of macroscopic uniform pores is generated through the random growth method.On this basis,the electromagnetic parameter inversion method based on scattering parameters and the strictly coupled wave analysis method are combined to calculate the equivalent electromagnetic parameters.Different finite element simulation examples are used to preliminarily verify the results at 1-18 GHz frequencies,and the accuracy is better than the formula calculation results.Secondly,the dielectric properties of materials containing a certain amount of water were analyzed,and it was found that the dielectric loss would significantly increase at 1%water content,reaching the order of 10-2.At the same time,the influence of different volume water content on electromagnetic wave transmission is calculated,indicating the necessity of adopting moisture-proof measures for SiO2f/SiO2 composite materials.Finally,for the possible temperature gradient of materials during high-speed flight,the equivalent dielectric constant and dielectric loss under the temperature layered model are calculated using the transfer matrix method,indicating that the dielectric properties of materials in solid state vary little due to temperature.The analysis of the carbonized layer formed at high temperatures shows that the simulation results of the dielectric properties and losses of the carbonized layer are greater than the experimental measurements,but it should still be noted that the carbonized layer has a significant impact on the dielectric properties of the material.The above research is mainly aimed at SiO2f/SiO2 Composite materials,but some methods and ideas also have certain reference value for other composite structures.Obtaining the equivalent electromagnetic parameters of materials through modeling and calculation has considerable practical significance for the design and analysis of composite materials.