Effect of thermal aging on the mechanical and dielectric properties of quartz fiber reinforced polyimide matrix composite

Structural absorbing composite material is the key material for both stealth, load bearing and lightweight. In this experiment, a lightweight microwave absorbing material was prepared using quartz fiber as the reinforcement, polyimide as the matrix, and 5 wt% carbon black as absorbent. The bending performance of the composite material without thermal aging reached 709 MPa, and the surface of the material was dense, smooth and flat. After thermal aging for 200 h, the surface of the material still remained a good condition, which showed that the thermal stability of the material was excellent. After thermal aging for 1000 h, the weight loss of the material remained within 5%. It could be seen that the performance of weight retention was also very good. Compared with the untreated material, the flexural strength of the material after 1000 h thermal aging still maintained 70% (493 MPa). The real and imaginary parts of dielectric of the material still maintained the frequency-dependent characteristics. But after a long time of thermal aging, the imaginary part of the material showed an increasing trend, increasing from 1.4 to 1.9 at 8.2 GHz. Ultimately, after thermal aging, when the thickness of the material was 3 mm, the minimum reflectivity of the material changed from − 8.5 to − 12.5 dB.