Effect of Load on the Thermal Expansion Behavior of T700 Carbon Fiber Bundles

Abstract

T700 carbon fiber bundles (CFBs) are the primary material used for manufacturing cable-net in a deployable antenna. In this paper, the relationships between the coefficient of thermal expansion (CTE) of T700 CFBs and the experimental load were investigated. The microstructure of T700 CFBs was analyzed with Raman spectra and XRD before and after the thermomechanical test. The measured results indicated that the T700 CFBs that were parallel to the axis had negative expansion characteristics when in a temperature range of −150-+150 • C. The thermal strain that occurred during the heating and the cooling thermal cycles had an unclosed curve that served as the loop. When the thermal cycles were the same, the position of the strain loop and the length of the sample exhibited regular change. The average of the CTEs decreased as the experimental load increased. The microstructural analysis suggested that the degree of structural order and the degree of orientation along the fiber axis improved with the experimental load increase. The change of microstructure parameters could be the primary cause of the negative CTE's variation within the T700 CFBs. The experimental results provide some guidelines for improving the cable-net material selection.

Objects impact effect on thermal fatigue life of unidirectional T700 Carbon Fiber/Epoxy

“…The nominal modulus and tensile strength of T700 are 230 GPa and 4900 MPa, respectively, and the nominal diameter for the sample of bundles was 1.4 mm, with an original gauge length of 500 mm at 1 N tensile load. All samples were dried at 50°C for 3 h" (Geng et al, 2018).…”

“…The pre-stretching treatment was performed at the Thermo-Mechanical Analyzer (TMA) (This instrument is self-made by Harbin Institute of Technology, Harbin, China), and the samples were pre-stretched at room temperature by periodically cycling the tension from 0 to 80 N 30 times for 500 s. When the length of the sample tended to be stable, the thermal expansion was measured. The sample in the pre-stretching treatment and actual test was the same" (Geng et al, 2018).…”

“…In the initial stage of pre-stretching, the micro-strain of Table 1. The axial CTEs of the samples applied series load during the three thermal cycles and the series test load that corresponded to the initial micro-strain (Geng et al, 2018). the CFBs showed a significant change, which was an obvious strain relaxation characteristic.…”

“…The micro-strains of the CFBs decreased and tended toward stability as the pre stretching durations increased. The initial micro-strain values, under the various load conditions, are provided in Table 1" (Geng et al, 2018).…”

“…(a) Schematic diagram of the thermo-mechanical analyzer (1. lead rail; 2. ball screw; 3. frame; 4. loading motor; 5. load sensor; 6. strain sensor; 7. the benchmark frame of quartz tube; 8. quartz rod; 9. the sample; 10. thermal conductivity layer; 11. the lagging; 12. infrared lamp; 13. liquid nitrogen; 14. the interface of vacuum and argon gas; 15. the inlet of argon gas; 16. the outlet of argon gas) and (b) The picture of the test facility for the measurement of coefficients of thermal expansion. Source: Geng et al (2018).…”