Research on the Characteristics of Braided String Based on Domestic Aramid Fiber for Semi-rigid Substrate of Solar Array

Abstract The substrate serves as a mounting base for the solar cells of the space-based solar array, and the “rigid frame of carbon fiber composite + tensioned mesh structure based on the braided string” constitutes the primary structure of the semi-rigid substrate of the large DFH-5 satellite. Tests and experiments have been conducted in four key areas: the creep characteristics of the braided string and its core under different loads, the creep characteristics of the braided string’s core due to changes in humidity and temperature, and the creep characteristics of the braided string itself due to temperature changes. The results show that the elongation of the braided string is twice that of its core under the same load. To reduce the stress relaxation of the tensioned braided string, it is necessary to perform pre-treatment to mitigate creep in advance. An increase in humidity can cause tension relaxation in the tensioned braided string. To mitigate this, a pre-tensioned core of the braided string can be utilized, and environmental control on the ground is recommended to reduce the impact of humidity on tension relaxation. Thermal pre-treatment is advised, as high temperatures can lead to partial changes in the properties or thermal stress release of aramid III fiber, resulting in the relaxation of the tensioned braided string and irreversible changes. The creep performance of the braided string’s core, however, is not affected by low temperatures. Through these experiments, the creep characteristics and pre-treatment guidelines for the braided string under different environmental conditions have been established, providing a foundation for the large-scale application of this structure in semi-rigid substrates of solar arrays.