The breakthrough - funded by the U.S. Department of Defense and published in Macromolecules and the Journal of Composite Materials - was led by Dr. Mohammad Naraghi, director of the Nanostructured Materials Lab and professor of aerospace engineering at Texas A and M, in close collaboration with Dr. Andreas Polycarpou at The University of Tulsa.
Their work explored the mechanical integrity, shape-recovery and self-healing properties of an advanced carbon-fiber plastic composite called Aromatic Thermosetting Copolyester (ATSP).
"In aerospace applications, materials face extreme stress and high temperatures," Naraghi said. "If any of these elements damage any part of an airplane and disrupt one of their main applications, then you could perform on-demand self-healing."
As ATSP matures and scales, it holds the potential to transform commercial and consumer industries, particularly the automotive sector.
"Because of the bond exchanges that take place in the material, you can restore a car's deformations after a collision, and most importantly, significantly improve vehicle safety by protecting the passenger," Naraghi said.
ATSP is also a more sustainable alternative to traditional plastics. Its recyclability makes the material an ideal candidate for industries aiming to reduce environmental waste without compromising durability or strength.
"These vitrimers, when reinforced with discontinuous fibers, can undergo level cycling - you can easily crush and mold it into a new shape, and this can happen across many, many cycles, and the chemistry of the material basically doesn't degrade," he said.
What sets ATSP apart from traditional plastics is its self-healing and shape-recovery capabilities.
"Shape recovery and self-healing are two facets of the same mechanism," Naraghi explained. "With shape recovery, it refers to the bond exchange within a continuous piece of material - a kind of built-in 'intelligence.' And, in self-healing, there's discontinuity in the material like a crack. These are the properties we investigated."
To investigate its properties, the researchers used a novel stress-test called cyclical creep testing.
"We applied repeated cycles of tensile, or stretching, loads to our samples, monitoring changes in how the material accumulated, stored and released strain energy," Naraghi said.
Using cyclical loading, the researchers identified two critical temperatures within the material.
"The first is the glass transition temperature, or the temperature at which the polymer chains can move around easily, and the second is the vitrification temperature. That's the temperature at which these bonds are thermally activated enough that you can see massive bond exchanges to cause healing, reshaping and recovery," he said.
The team then conducted deep-cycle bending fatigue tests, periodically heating the material to around 160 degrees Celsius to trigger self-healing.
Their results showed that the ATSP samples not only endured hundreds of stress and heating cycles without failure, but that they actually grew more durable during the healing process.
"Much like skin can stretch, heal and return to its original shape, the material deformed, healed and 'remembered' its original shape, becoming more durable than when it was originally made," Naraghi said.
The goal? To assess the material's performance and self-healing properties.
After two full damage-healing cycles, the material returned to nearly full strength. By the fifth cycle, healing efficiency dropped to about 80% because of mechanical fatigue.
"Using high-resolution imaging, we observed that the composite after damage and healing was similar to the original design, though repeated damage caused some localized mechanical wear attributed to manufacturing defects," Naraghi said.
Still, the material's chemical stability and self-healing behaviors remained reliable across all five cycles.
"We also observed that there was no thermal degradation or breakdown in the material, demonstrating its durability even after damage and healing," Naraghi said.
"Our partnerships are very important," Naraghi said. "In addition to supporting us financially, the program managers at AFOSR collaborate with us and offer valuable guidance on questions that could have been overlooked. Our close collaboration with ATSP Innovations has also proven to be very fruitful and very important."
The research team's breakthrough represents more than an emerging class of materials; it's a blueprint for how bold science and strategic partnerships can redefine a future where plastics don't just endure, they evolve and adapt.
"My students and post-docs do the heavy lifting - I cannot thank them enough," Naraghi added. "It's through trial and error, collabo
Research Report:Identifying the origin of intrinsic self-healing gradual decay in vitrimer carbon fiber reinforced polymer composites
Related Links
Texas A and M University
Space Technology News - Applications and Research
| Subscribe Free To Our Daily Newsletters |
| Subscribe Free To Our Daily Newsletters |
