Mechanical properties of a novel Tri-directional carbon-flax-aramid fiber reinforced composite

A novel Tri-directional Carbon-Flax-Aramid fiber reinforced composite (3D-CFAFRP) was proposed, manufactured and tested in this study, which was designed based on the idea of better tailoring the strength, stiffness, toughness and weight requirements, adopting three different types of fibers to reinforce the matrix along three orthogonal directions. The in-plane and interlaminar mechanical properties of 3D-CFAFRP composites were studied experimentally, and were compared with those of the carbon fiber orthogonally laminates (2D-CFRP). Results showed that the Mode I and Mode II interlaminar fracture toughness of 3D-CFAFRP composites were enhanced by 6.2 times and 64.77%, respectively. The interlaminar fractured surfaces indicated that the preventing of the crack propagation by the needle aramid yarns and the hierarchical failure modes due to the unique microstructure of the flax fibers contributed to the improved interlaminar fracture toughness. In addition, the tensile strength of 3D-CFAFRP composites was about 33% higher than that of 2D-CFRP composites due to the existence of the needle aramid yarns in the thickness direction. The flexural and compressive strength of 3DCFAFRP composites were 14.09% and 7.6% lower than those of the 2D-CFRP composites, respectively, which was attributed to resin-rich region, in-plane fibers distortion and damage introduced by stitching. Nevertheless, the specific in-plane strength and modulus of 3D-CFAFRP composites were all higher than or similar to that of 2D-CFRP composites due to its lower density. Furthermore, 3D-CFAFRP composites also possessed lower cost and eco-friendly advantages compared with 2D-CFRP composites.