Effect of thermo-oxidative aging on three-dimensional and four-directional braided carbon fiber/epoxy composite

Abstract

An experimental study was performed to investigate the effect of high temperature exposure on flexural properties of the three-dimensional and four-directional braided carbon fiber/epoxy composite and the corresponding neat resin. For this purpose, samples were exposed to 90℃, 120℃, 150℃, and 180℃ (below and above the glass transition temperature of the matrix resin) for various periods of time up to 13 days. The flexural properties combining with Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), weight loss, scanning electron microscope (SEM), and optical microscope analyses were performed on the unaged and aged samples. The results revealed that the thermo-oxidative behavior of the braided composite was significantly different from the neat resin. The flexural strength of the neat resin decreased dramatically due to the oxidation degradation of the sample surface when the aging temperature was equal to its glass transition temperature. The extensive degradations of both the matrix and the fiber/matrix interface, especially for the interface, were responsible for the significant decrease in flexural strength of the braided composite. The flexural strength retention rates of the braided composite were higher than that of the neat resin after exposure to 90℃, 120℃ and 150℃ because the integral structure of the braided composite can make the fiber bear flexural force together although the matrix resin and the fiber/matrix interface had a certain degree of damage after longtime thermo-oxidative aging.