Changes in the Vickers hardness, wettability, structural and mechanical properties of the «shielding composite» under the exposure to cosmic radiation

Abstract

The article presents the results of the study of the structure and surface of the «Shielding composite» (polymer composite for radiation shielding), which was in space on the Russian segment of the ISS for 225 days. The research was conducted as part of the space experiment “Shielding Composite” on the Russian segment of the ISS in 2022. The polymer composite was used to make the container that was installed in the cosmonauts’ cabin for the entire duration of the orbital flight. Being in space resulted in a slight decrease in the microhardness of the outer surface, but did not affect the deeper layers or the inner structure of the composite: microhardness of the outer surface decreased by 0.19 HV (4.5 %); microhardness of the inner surface increased by 0.79 HV (18.6 %); cross section remained unchanged. The results of ultrasound scanning of the upper cap of the container showed a slight decrease in the ultrasonic wave propagation velocity (by 4 %) and the modulus of elasticity of the composite (by 9 %) after space tests of the composite. There is an insignificant decrease (up to 5 %) in free surface energy of the composite after being in space for 225 days. Water wetting contact angle of the composite increased from 100.98 ± 2.60° to 106.85 ± 14.28° and diiodo-methane wetting contact angle increased from 57.50 ± 8.33° to 59.55 ± 7.22° after cosmic exposure.