Self healing composites

A self-healing material system developed by researchers at the University of Illinois offers an inexpensive way to repair composite materials used in structural applications ranging from aeroplane fuselages to wind-farm propeller blades.

The new self-healing system incorporates chlorobenzene microcapsules, as small as 150 microns in diameter, as an active solvent.

'Self-healing of epoxy materials with encapsulated solvents can prevent further crack propagation, while recovering most of the material’s mechanical integrity,' said Jeffrey Moore, the Murchison-Mallory Professor of Chemistry at Illinois.

During normal use, epoxy-based materials experience stresses that can cause cracking, which can lead to mechanical failure. Autonomous self-healing – a process in which the damage itself triggers the repair mechanism – can retain structural integrity and extend the lifetime of the material.

In the new system, when a crack forms in the epoxy material, microcapsules containing the chlorobenzene break. The solvent then disperses into the matrix, where it finds pockets of unreacted epoxy monomers. The solvent then carries the latent epoxy monomers into the crack, where polymerisation takes place, restoring structural integrity.