In situ observations of fractures in short carbon fiber/epoxy composites

In contrast with traditional methods of observation, synchrotron radiation X-ray computed tomography (SR-CT) is an advanced technique that allows direct three-dimensional (3D) and non-destructive observation of microstructures in materials. High-resolution in situ observations (0.7 μm/pixel) of fractures in short carbon fiber/epoxy composites are achieved using the SR-CT technique, and the mechanical load response of short carbon fibers treated with oxidation and those untreated are compared. By the quantitative extraction and analysis of microstructure parameters in high-resolution 3D images, the failure mechanisms of the two materials were studied. The proportion of broken fibers to other types of fiber damage in the sample with oxidation-treated fibers increases by about 6%. Also, the oxidation treatment is able to reduce the ineffective length of the fibers by about 20%, thereby improving the mechanical properties of these composites. The results show that computed tomography can promote characterization of the internal microstructures in carbon fiber-reinforced polymer composites, which will facilitate further theoretical research on the failure mechanisms of these composites.