High-temperature tensile testing of composites
Description
True stress–strain data from specimen mechanical tests, XRD results, and constitutive model code.
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Steps to reproduce
Uniaxial tensile tests were conducted using a universal testing machine (INSTRON 5982, USA). High-temperature tensile experiments were performed within a thermal environmental chamber equipped with an electric heater, liquid nitrogen tank, thermocouples, and an internal air circulation fan, ensuring uniform and stable temperature conditions throughout the chamber. Prior to each test, the tensile specimen was conditioned at the target temperature for 15 minutes to ensure thermal equilibrium. During testing, an extensometer was used to record the axial tensile strain under all temperature conditions. The tensile strain rate was fixed at 0.01 s⁻¹, and tests were performed at five different environmental temperatures: 30 °C, 70 °C, 90 °C, 110 °C, and 150 °C. To ensure data reliability, thermocouples were affixed at different positions on the printing platform during specimen fabrication to monitor temperature uniformity. In addition, an infrared thermal imager was used to monitor the nozzle temperature in real time. During tensile testing, thermocouples were also attached to the specimen surface to assess temperature stability during loading. Each tensile test was repeated three times to ensure repeatability and accuracy of the results. To further explore potential crystalline phase transitions in SCF‑PA12 composites under elevated temperatures, in-situ X-ray diffraction (XRD, Bruker D8 Advance, Germany) was conducted. Cu-Kα radiation (λ = 0.15406 nm) was used for continuous scanning. Bulk samples with dimensions of 10 mm × 10 mm × 3 mm were placed on a high-temperature heating stage. In-situ XRD measurements were performed at three characteristic temperatures: 30 °C (representing the glassy state), 110 °C (near the glass transition region), and 150 °C (superheated state). Temperature was controlled with a precision of ±1 °C, and specimens were held isothermally for 5 minutes at each temperature point to ensure thermal equilibrium and stress relaxation. The heating rate was set to 5 °C/min. High-purity nitrogen gas was introduced during the test to prevent oxidative interference. The scanning range was set from 5 ° to 40 ° (2θ), with a scanning speed of 1 °/min. All diffraction data were processed with background subtraction and smoothing, and peak positions, intensities, and full width at half maximum (FWHM) were analyzed to characterize phase transitions and changes in crystallinity. These results provide crystallographic evidence for thermally induced structural evolution mechanisms.
Institutions
- Nanjing University of Aeronautics and Astronautics