From: University of Washington
November 4, 2021 -- Researchers have
created a new type of carbon fiber reinforced material that is as strong and
light as traditionally used materials, but can be repeatedly healed with heat,
reversing any fatigue damage. This also provides a way to break it down and
recycle it when it reaches the end of its life.
Because of their high strength and light
weight, carbon-fiber-based composite materials are gradually replacing metals
for advancing all kinds of products and applications, from airplanes to wind
turbines to golf clubs. But there's a trade-off. Once damaged or compromised,
the most commonly-used carbon fiber materials are nearly impossible to repair
or recycle.
In a paper published Nov. 2 in the
journal Carbon, a team of researchers describes a new type of carbon
fiber reinforced material that is as strong and light as traditionally used
materials but can be repeatedly healed with heat, reversing any fatigue damage.
This also provides a way to break it down and recycle it when it reaches the
end of its life.
"Developing fatigue-resistant
composites is a major need in the manufacturing community," said co-lead
author Aniruddh Vashisth, University of Washington assistant professor of
mechanical engineering. "In this paper, we demonstrate a material where
either traditional heat sources or radio frequency heating can be used to
reverse and postpone its aging process indefinitely."
The material is part of a recently
developed group known as carbon fiber reinforced vitrimers, named after the
Latin word for glass, that show a mix of solid and fluid properties. The
materials typically used today, whether in sporting goods or aerospace, are
carbon fiber reinforced polymers.
Traditional carbon fiber reinforced
polymers typically fall into two categories: thermoset or thermoplastic. The
"set" variety contains an epoxy, a glue-like material where the
chemical links holding it together harden permanently. The "plastic"
version contains a softer type of glue so it can be melted back down and
reworked, but this becomes a drawback for high strength and stiffness.
Vitrimers on the other hand, can link, unlink and relink, providing a middle
ground between the two.
"Imagine each of these materials is
a room full of people," Vashisth said. "In the thermoset room, all of
the people are holding hands and won't let go. In the thermoplastic room,
people are shaking hands and moving all around. In the vitrimer room people
shake hands with their neighbor but they have the capacity to exchange
handshakes and make new neighbors so that the total number of interconnections
remains the same. That reconnection is how the material gets repaired and this
paper was the first to use atomic-scale simulations to understand the
underlying mechanisms for those chemical handshakes."
The research team believes vitrimers
could be a viable alternative for many products currently manufactured from
thermosets, something badly needed because thermoset composites have begun
piling up in landfills. The team says that healable vitrimers would be a major
shift toward a dynamic material with a different set of considerations in terms
of life-cycle cost, reliability, safety and maintenance.
"These materials can translate the
linear life cycle of plastics to a circular one, which would be a great step
toward sustainability," said co-senior author Nikhil Koratkar, professor
of mechanical, aerospace and nuclear engineering at Rensselaer Polytechnic
Institute.
The research team also includes Mithil
Kamble and Catalin Picu at Rensselaer Polytechnic Institute and Hongkun Yang
and Dong Wang at the Beijing University of Chemical Technology. This research
was funded by the U.S. Army and NASA through the Vertical Lift Research Centers
of Excellence program, the National Science Foundation, the John A. Clark and
Edward T. Crossan Chair Professorship at Rensselaer Polytechnic Institute, the
University of Washington, and the company Software for Chemistry &
Materials.
https://www.sciencedaily.com/releases/2021/11/211104115358.htm
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