Accelerated Thermo-Oxidative Aging On Carbon Fiber/Epoxy Composite

In this work, weight loss measurement, static mechanical property test, infrared spectrum analysis, thermogravimetric analysis (TGA) and dynamic mechanical thermal analysis (DMTA) were used to investigate the accelerated thermo-oxidative behaviors of T700-CF/828+TDE-85 composite at the temperatures above and below its Tg, respectively. The changes in the weight loss, NOL shear strength, glass transition temperature, and thermal degradation activation energy of the composite with aging were studied. In addition, the Flynn—Wall—Ozawa method was used to predict the lifetime of the composite based on the activation energies calculated from the TGA results.The weight loss measurement showed that the weight of the composite quickly reduced at the first aging period then was close to a constant, which increased with aging temperature. While the NOL shear strength showed a complicated change due to the positive (physical shrinkage) and negative (interface damage) effects developed during the aging process. It was found that the NOL shear strength increased at the fore-period of the thermal aging, and eventually dropped. The DMTA results indicated that thermal aging caused embrittlement in the composite, with an indicator of increasing of Tg with aging. The higher the aging temperature, the more increasing of the Tg.In addition, the Flynn—Wall—Ozawa method was chosen to predict the lifetime of the composite at room temperature. The activation energies of the composite in different aging periods were calculated from the TGA results. It was found that the activation energy presented a little increase after aging. In this experiment, the change of the activation energy was not so much that the Flynn—Wall—Ozawa method was still used to calculated to the lifetime of the T700-CF/828+TDE-85 composite. Choosing weight loss of 5% as the failure criteria of the composite, a lifetime of 37.541 years was obtained for the T700-CF/828+TDE-85 composite.