The new technology solves the long-standing challenge of self-healing materials

Engineering researchers have developed a new self-healing composite that allows structures to repair
themselves without needing to be dismantled.
This latest technology solves two long-standing challenges faced by self-healing materials and can significantly extend the life of structural components such as wind turbine blades and aircraft wings
.

Jason Patrick, corresponding author of the research paper and assistant professor of civil, architectural and environmental engineering at North Carolina State University, said: "Researchers have developed a variety of self-healing materials, but previous self-healing composite strategies faced two practical challenges
.
"

"First, for treatment, these materials often need to be removed
from services.
For example, some need to be heated in the oven, but this cannot be done
for large parts or specific parts when in use.
Second, self-healing is only effective
for a limited time.
For example, the material may heal a few times, after which its self-healing properties will decrease
significantly.
We have proposed an approach to address both challenges in a meaningful way while preserving the strength and other performance characteristics
of structural fiber composites.
In

practice, this means that users can rely on a given structural component, such as wind turbine blades, for a long period of time without fear of failure
.


"By extending the life of these composites, we make them more sustainable," Patrick said
.
"While wind turbine blades are a good example, structural composites have a wide range of applications: aircraft wings, satellites, automotive parts, sporting goods
, you name it.
"

Here's how this new self-healing fiber-reinforced composite works
.


Laminated composites are made
by bonding fiber-reinforced layers, such as glass and carbon fiber, together.
Damage
most often occurs when the "glue" that binds these layers begins to peel off or delamilate from the reinforcement layer.
The team solved this problem
by 3D printing patterns of thermoplastic healing agents on reinforcement materials.
The researchers also embedded a thin "heater" layer
in the composite.
When an electric current is applied, the heater layer heats up
.
This in turn melts the healing agent, which flows into any cracks or microcracks in the composite and repairs them
.


"We found that this process can be repeated at least 100 times while maintaining the effectiveness of
self-healing," Patrick said.
We don't know what the upper limit is, if any
.
"

The printed thermoplastic also improves its inherent fracture resistance by up to 500%, meaning it needs more energy to cause delamination
in the first place.
In addition, both the healing agent and the heating layer are made of ready-made materials and are relatively inexpensive
.


"While it would be slightly more expensive to manufacture composites that incorporate our designs, significantly extending the life of the material would more than offset the cost
," Patrick said.


Another advantage of this new technology is that if internal heating elements are attached to the wings of an aircraft, airlines can stop using chemicals to remove ice from the wings when the aircraft lands, as well as de-ice
in flight.


"We've proven that this versatile technology works," Patrick said
.
"We are now looking for government and industry partners to help us tailor these polymer-based composites for specific applications
.
"

Prolonged in situ Self-healing in Structural Composites via Thermo-Reversible Entanglement