In this study, an epoxy resin was reinforced by three-dimensional (3-D) carbon fiber fabrics (orthogonal nonwoven type). The purpose of the study was to investigate the effect of weave density (5 mm type and 7.5 mm type (spacing between two Z axis yarn bundles are 5 mm and 7.5 mm. respectively)) and directional reinforcement (3D and 5D) on the mechanical fracture behavior of these 3-D composites. A comparison with a traditional two-dimensional (2-D) composite is also presented. The results revealed that the tensile strength of the 2D CFRP was 2-2.5 times greater than that of 3D CFRP and about three times greater than that of the 5D CFRP. Also, the 3D CFRP was 3-4 times, and the 5D CFRP was five times, more deformable than the 2D CFRP composite. In Charpy impact tests, the impact strengths of 3D and 5D structural composites were found to be 2 and 2.5 times greater than those of 2D composites, respectively. From failing weight impact tests, we found that the impact energy of 3-D composites was higher than that of 2-D composites, and the ductility index of 3-D composites was also higher than that of 2-D composites. We concluded that the impact toughness of 3-D composites was better than that of 2-D composites. The flexural and shear strengths of these materials are also discussed.
