Engineers create self-healing fiber-based composites

Microvascularized system repeatedly repairs internal cracks automatically.

0 April 16, 2014
Mike McLeod

3D microvascular networks for self-healing composites: Researchers were able to achieve more effective self-healing with the herringbone vascular network (top) over a parallel design (bottom), evidenced by the increased mixing (orange-yellow) of individual healing agents (red and green) across a fracture surface. (Photo Credit: University of Illinois at Urbana-Champaign)

3D microvascular networks for self-healing composites: Researchers were able to achieve more effective self-healing with the herringbone vascular network (top) over a parallel design (bottom), evidenced by the increased mixing (orange-yellow) of individual healing agents (red and green) across a fracture surface. (Photo Credit: University of Illinois at Urbana-Champaign)

Fiberglas and other fiber-reinforced composites have long been a favored build material in aerospace, automotive and even sporting goods due to their high strength-to-weight ratio, but they have one major drawback. Small, internal cracks in the material can quickly develop into irreversible damage from delamination, a process in which the composite layers separate.

To confront this short-coming, a group of researchers — headed by professors Nancy Sottos, Scott White, and Jeff Moore at the Beckman Institute’s Autonomous Materials Systems (AMS) Group at the University of Illinois at Urbana-Champaign — have created an autonomous self-healing system for fiber-based composites.

The system works by weaving 3D vascular networks into the multi-layered, fiber-reinforced composites. The capillary-like microchannels are then filled with either an epoxy resin or a hardener. When cracks within the material form, the small tubes break, and allow the self-healing fluids to “bleed out” and polymerized, thereby healing the internal structure.

“This is the first demonstration of repeated healing in a fiber-reinforced composite system,” said Scott White, aerospace engineering professor and co-corresponding author. “Self-healing has been done before in polymers with different techniques and networks, but they couldn’t be translated to fiber-reinforced composites. The missing link was the development of the vascularization technique.”

To create the vascular network, the researchers weaved thin polymer fibers into the composite material during fabrication. Afterwards, the material was then heated to melt and evaporate the fibres, leaving behind the hollow microchannels. According to the research team, the system was tested multiple times and 100 percent of the cracks healed.

“Additionally, creating the vasculature integrates seamlessly with typical manufacturing processes of polymer composites, making it a strong candidate for commercial use,” said Nancy Sottos, materials science and engineering professor and co-corresponding author.

The researchers’ findings were detailed in a paper titled “Continuous self-healing life cycle in vascularized structural composites,” published in Advanced Materials. Their work was supported by the Air Force Office of Scientific Research; the Department of Homeland Security Center of Excellence for Explosives Detection, Mitigation, and Response; and the Army Research Laboratory.
http://beckman.illinois.edu


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