Despite its relative novelty, carbon fiber has actually been around for more than 150 years. It has only become prevalent in the last 50 years or so due to advances in the manufacturing process, which give it the impressive strength-to-weight ratios. Combined with a sharp decrease in the manufacturing cost over the last 20 years, it has become a favorite material among design engineers that are developing some of the most advanced products in the world.

Carbon fiber composites are lightweight and strong, and therefore they have been gradually replacing metals in various applications, some examples include golf clubs and wind turbines. However, there are some notable disadvantages to carbon fiber composites. Damaged carbon fiber is impossible to fix. It is also expensive and time consuming to craft into difficult shapes. Finally, the chemical bonds created during carbon fiber curing are irreversible, meaning components cannot be recycled.

As a response to this, there has been focus on developing a new type of carbon fiber that can be repaired. Researchers have focused on creating a carbon fiber that exhibits the light and strong characteristics, but can repaired and recycled.

The carbon fiber industry is in desperate need of materials innovation. And a new material called vitrimer could be key to that.

What is vitrimer?

Polymer products typically fall into one of two categories, thermoplastic, or thermoset.

Thermoplastics contain a base material that withholds filler or additives, which impart performance attributes, such as dielectric resistance or physical strength, into components made of the material. However, there is no chemical reaction between the materials. This makes them relatively easy to process, shape, rework and recycle, and it is completed using heat or chemicals. However, thermoplastics tend to have less strength than thermosets, and are generally less durable.

Thermosets contain raw materials that, once heated, create irreversible molecular cross-links. As a result thermosets are much more difficult to process into complex shapes and the curing process takes a bit longer. Yet final components have performance qualities better than thermosets, and are less likely to degrade from chemical or environmental exposure. This means they are also better suited for bonding with itself or other materials.

Vitrimers present a happy medium between thermosets and theroplastics. Vitrimers are a newly created group of composite, founded in 2011 by Ludwik Leibler of the French National Centre for Research Science. They are closely related to thermosets, yet when heated, can exchange cross-links with neighboring materials at a molecular level. They have the mechanical and thermal performance of thermosets, and can even be welded. However, under the right conditions, they can be reverse processed, and therefore also repaired.

“Imagine each of these materials is a room full of people,” said University of Washington mechanical engineering assistant professor Aniruddh Vashisth.

“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 re-connection 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.”

Carbon fiber reinforced vitrimers could replace traditional carbon fiber materials. Materials used in aerospace and in sporting goods today are generally carbon fiber reinforced polymers (CFRP). In their own right, CFRPs are very high-tech materials that have properties that exceed aluminum and steel for many applications. They consist of several constituents: a carrier substance or base, known as the matrix; and the actual carbon fiber material, which acts as the reinforcing component that is embedded within the matrix. Typically, a type of synthetic resin is used as the matrix material. The variety of mechanical properties that can be see in carbon fiber comes from the different materials that can be chosen as the matrix material, the type of carbon fibers that are used in the material, and the specific manufacturing process that was used to make it.

The potential when it comes to repairable carbon fiber composite is endless, almost literally. It has industry leading properties in strength, weight, durability and conductivity, yet promises a type of carbon fiber that can be repaired and reworked -- and more impressively reversed and recycled.

It remains to be seen how pervasive the repair technology can become, as that would be the main challenge to wider ubiquity. But if it can be made available on a professional or consumer level, expect this new flavor of carbon fiber to have a big industrial appetitie.

Do you think that a healable carbon fiber composite is the answer to a lot of issues with reusability? What product would you like to see a healable carbon fiber in the most?