Effects of aging process and testing temperature on the open-hole compressive properties of a carbon fiber composite

Abstract

The properties of T800 carbon fiber–epoxy composite specimens with a hole were studied in terms of mass change, scanning electron microscopy, glass transition temperature ( T g), heat-resistant temperature, Fourier-transform infrared (FTIR) spectroscopy, open-hole compressive strength at different temperatures, and stereomicroscopic observations after being subjected to hygrothermal aging and thermal-oxidative aging processes. FTIR spectra indicated that after hygrothermal aging at 70°C and 85% relative humidity (RH), chemical aging did not occur, whereas after thermal-oxidative aging at 190°C, the specimens exhibited chemical aging. The unaged specimens had a T g of 229°C and an extreme heat-resistant temperature T gmod of 184°C; after hygrothermal aging, the specimens had a T g and T gmod of 207°C and 143°C, respectively; and after thermal-oxidative aging, the specimens had a T g and T gmod of 252°C and 215°C, respectively. The effects of temperature on open-hole compressive strength were evaluated at room temperature of 23°C, 50°C, 100°C, 150°C, and 200°C. The compressive strengths of the specimens decreased after aging and with the increasing test temperature. At the highest test temperature, the unaged specimens, hygrothermal-aged, and thermal-oxidative-aged specimens retained over 73.7%, 65.5%, and 67.9%, respectively, of their compressive strength. Thus, the T800 carbon fiber–epoxy composite evaluated in this study exhibited good resistance to the effects of aging and high temperature. These results should be beneficial to the understanding of the long-term performance of composites.