Flexural fatigue properties and failure propagation of 3D stitched composites under 3-point bending loading

This work investigated the static and fatigue properties of 3D stitched composite and 2D laminated composite subjected to three-point bending loads. Four stress levels were carried out to investigate fatigue characteristics of the composites. The failure propagation of the composites and their fracture morphology were captured in detail using the high-speed camera. The results demonstrated that the static flexural strength of 3D stitched composite was lower than 2D laminated composite but the modulus of 3D stitched composite was higher than that of the latter. Besides, the fatigue failure mechanism of 3D stitching composite was dependent on the stress levels. Though the fatigue life of the 3D stitching composite was not as good as 2D laminated composite, the failure of stitching thread proved to be able to judge the catastrophic damage of the 3D stitching composite, which is important for indicating the safe use of the composite structure.