Self-healing composites are composite materials capable of automatic recovery when damaged. They are inspired by biological systems such as the human skin which are naturally able to heal themselves. Over the past two decades, two major self-healing concepts – based respectively on the use of capsules and vascular networks containing healing agents - have been proposed and material property recovery has been enhanced from 60% to nearly 100%. However, this improvement is still not sufficient to allow self-healing composites to be applied in practice because the healing capability varies with many external factors such as ambient temperatures and damage conditions. The key to the practical application of self-healing composites is to promote the sustainability of healing capacity to make the recovery robust. The thesis presents various techniques to enhance the healing capacity of fibre-reinforced composites to realise strong recovery regardless of ambient temperatures or material types. It presents the effects of various popular configurations of vascular networks on the flexural properties and healing performances of fibre-reinforced composites. The thesis demonstrates a design enabling recovery at ultra-low temperatures by using hollow vascular networks and porous heating elements. It also presents a new healing mechanism to repair the broken structural carbon fibres by incorporating conventional healing agents with short carbon fibres which could be aligned in an in situ electric field. The mechanism was also adopted to enable the restoration of the conductivity of a fibre-reinforced composite incorporating a porous conductive element, a carbon nanotube sheet, which could be used as a heating actuator or a sensing component. Thus, the development reported in this thesis have contributed to promoting the sustainability of the recovery of self-healing composites.
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