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 once damaged or compromised, the most commonly used carbon fiber materials are nearly impossible to repair or recycle.
A team of researchers has created a new type of carbon fiber reinforced material that is as strong and light as traditionally used ones but can be repeatedly healed with heat, reversing any fatigue damage and providing a way to break it down and recycle it when it reaches the end of its life. 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 (CFRP). The materials typically used today, whether in sporting goods or aerospace, are carbon fiber reinforced polymers (CFRP). Traditional CFRPs 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 re-link, providing a middle ground between the two.
If each of these materials was a room full of people, 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 around. In the vitrimer room, people shake hands with their neighbor but have the capacity to exchange handshakes and make new neighbors so that the total number of interconnections remains the same. That re-connection is how the material gets repaired.
The team believes vitrimers could be a viable alternative for many products currently manufactured from thermosets, something badly needed as thermoset composites have begun piling up in landfills. Healable CFRPs would be a major shift toward a dynamic material with a different set of considerations in terms of lifecycle cost, reliability, safety, and maintenance.