Torsion damage mechanisms analysis of two-dimensional braided composite tubes with digital image correction and X-ray micro-computed tomography

This paper investigates the torsion progressive damage and failure mechanism of two-dimensional (2D) braided carbon/epoxy composite tubes. Four kind of samples with four braiding angles, 30°, 45°, 55°, and 60°, are experimentally tested on the static torsion machine. Three-dimensional digital image correlation (3D-DIC) is utilized to monitor the progressive torsional strain and the crack propagation. Also, Micro-computer tomography (Micro-CT) is employed to describe the volume of damages and the torsional damage morphologies inside the specimens. Results indicate that the braiding angle has a significant effect on the torsional mechanical behaviors. Furthermore, the damage modes of 30° and 60° specimens are mainly influenced by the accumulation of the matrix damage, whereas those of 45° and 50° ones are largely dominated by the fiber tows breakage.