Highly tough 3D woven composite materials: Fracture characterization and toughening mechanisms.

• A combination of the experiment and cohesive zone mode approach is proposed to determine the R-curve of 3D woven composite. • It overcomes the limitation of LEFM-based approach and avoids the difficulty in measuring the crack growth length. • The determined fracture toughness is about 860 kJ/m2, which is the highest. • The toughening mechanisms of are revealed. Characterization of the intralaminar fracture toughness of 3D woven composites is challenging owing to the limitation of linear elastic fracture mechanics-based approach. In this study, five different crack configurations are designed and tested. Only the single-edge notched tensile specimen can be used to measure the fracture toughness. A hybrid approach based on experiment and cohesive zone model is proposed to determine the R -curve of 3D woven composites. The fracture toughness of the present 3D woven composite is around 860 kJ/m2, considerably higher than those of the existing carbon fiber polymer reinforced composites. The mechanism underlying this high toughness is clarified. [ABSTRACT FROM AUTHOR]