Delamination toughening and healing performance of woven composites with hybrid z-fibre reinforcement

This paper presents an investigation of a novel three-dimensional (3D) hybrid fibre-polymer composite material that has the unique combination of properties to both resist the growth and self-heal delamination cracks. This hybrid fibre composite contains two types of through-the-thickness z-binders made of carbon fibre tows (for high delamination resistance) and thermoplastic filaments (for self-healing). The performance of this hybrid 3D composite is compared with 3D composites reinforced in the through-thickness direction with either carbon tows or thermoplastic filaments. The results show that the hybrid 3D reinforcements substantially improve the mode I interlaminar fracture toughness (∼1200%) and self-reparability of the composite. To understand the toughening mechanism of the hybrid z-binders, a finite element analysis is conducted to simulate the crack growth resistance behaviour and the fracture properties of the composite materials in the as-manufactured and healed conditions. The model is able to predict with good accuracy the fracture toughness and healing properties, and is used to further study the effects of hybridization ratio of the carbon and thermoplastic z-binders on the fracture toughness and healing properties of the 3D reinforced composites.