A Comparative Study on Interlaminar Properties of L-shaped Two-Dimensional (2D) and Three-Dimensional (3D) Woven Composites

The effect of fiber-resin interfacial structures (especially three-dimensional (3D) structures) on the delamination resistance of L-shaped beam composites was investigated via hinged loading tensile tests. Four types of structures were woven, and the corresponding reinforced epoxy composites were manufactured through a vacuum-assisted resin infusion (VARI) process. The results revealed that the two-dimensional (2D) laminate and 3D shallow-straight woven composite (3DSSWC) had the similar interlaminar strength and failed via delamination. However, compared with the resistance of these composites, a significantly higher delamination resistance was realized for a 3D orthogonal woven composite (3DOWC) and a 3D shallow-bend woven composite (3DSBWC). This high resistance resulted from the reinforcing fibers (i.e., Z-yarns) in the Z-direction and the considerable yarn waviness of the 3DOWC and the 3DSBWC, respectively. The failure mode of 3DOWC was characterized by interlayer delamination and Z-yarn or weft yarn breakage. Moreover, the failure mode of 3DSBWC was dominated by delamination and weft yarn breakage. Therefore, the 3D orthogonal (3DOW) and 3D shallow-bend (3DSBW) woven structures were quite effective in resisting delamination and, of the structures considered, the 3DSBW structure yielded the best L-shaped beam composite.