Abstract: In order to understand the influence of moisture gain on the electrical properties of quartz fiber composite radome, both simulation and experiments are performed on the radome and test samples. In this paper, electrical properties of quartz fiber composite before and after moisture gain are measured using both test samples and a radome. The wave transmissivity of the radome as a function of moisture gain are presented. And, the moisture absorption model of the radome is also proposed. The results show that quartz fiber composites usually have relatively high porosity and specific surface area, and tend to absorb moisture in the air. The moisture gain influences the electrical properties of quartz composite radome. The dielectric constant is slightly affected by the moisture gain, but the loss angle tangent increases by c.a. 3 times. The unmiostureproofed radome reaches absorption equilibrium within 2 weeks at the temperature of 20 ℃~30 ℃ and humidity of 65%~75%, the equilibrium and maximum absorption is 0.083 kg/m² and 6.3‰, respectively. The wave transmissivity of the radome drops by 7%~11% during the absorption, and keeps constant thereafter. The moisture absorption process basically agrees with the Langergren pseudo-second-order kinetic model. In summary, moisture gain has innegligible influence on the electrical properties and wave transmissivity of the radome. And, proper moistureproof measures must be taken to protect the quartz fiber composite radome from gaining moisture in the air.

Key words: moisture gain, quartz fiber/SiO₂ composite, radome, electrical properties, absorption dynamics, moistureproof