3D printing comes to the rescue of self-healing materials

Researchers at the NC State University (NCSU) in the U.S. turned to 3D printing to add a healing layer to materials that will help equipment to heal onsite, a university press release said.

Self-healing materials are the next frontier of technology that can help keep equipment in service for long periods of time. There has been significant progress in this area, but it is not without its own challenges.

For instance, the self-healing material in use today still requires it to be removed from service for the healing process. At times, the healing process can require the use of a heating oven, which might not be conducive for use for large components. Additionally, there are limits to how many times the material can self-heal.

Jason Patrick, an assistant professor of civil, construction, and environmental engineering at NCSU, and his team have now addressed these challenges by using additive manufacturing or 3D printing techniques to manufacture self-healing material.

Using 3D printing to make self-healing composites

Most modern-day lightweight composite materials are made using layers of glass and carbon fiber that are held together using specialized glue. The material, when used in equipment such as aircraft wings or wind turbines, begins to give way after the glue begins to peel away and the layers separate, a process called delamination.

Patrick and his team turned to 3D printing to put a pattern of a thermoplastic healing agent onto the laminated material. Embedded inside the laminated material were thin heater layers that could be turned on by supplying an electric current. The heat, thus generated, melts the healing agent that can flow into cracks or microfractures of the composite to repair them.

Interestingly, the research team found that the process could be repeated over 100 times, and the self-healing process was still effective.

Advantages of self-healing composites

The research also found that the composite made using this technique was inherently resistant to fracture by as much as 500 percent. This meant that the material was less likely to get delaminated in the first place. Even when it did, the self-healing property of the material would allow it to remain in service for long periods of time.

By increasing the longevity of the equipment made using these composites, the researchers are making them more sustainable. This would apply to a range of equipment made from these composites ranging from wind turbines to automotive components, satellites, as well as sporting goods, the researchers said in the press release.

When used to make aircraft wings, the heating elements could also be put to use to remove ice from the wings, whether on the ground or during flight. This would help airlines reduce their dependence on chemical agents for these purposes, the press release said.

The research findings were published in Nature Communications.

Abstract

Natural processes continuously degrade a material’s performance throughout its life cycle. An emerging class of synthetic self-healing polymers and composites possess property-retaining functions with the promise of longer lifetimes. But sustained in-service repair of structural fiber-reinforced composites remains unfulfilled due to material heterogeneity and thermodynamic barriers in commonly cross-linked polymer-matrix constituents. Overcoming these inherent challenges for mechanical self-recovery is vital to extend in-service operation and attain widespread adoption of such bioinspired structural materials. Here we transcend existing obstacles and report a fiber-composite capable of capable of minute-scale and prolonged in situ healing—100 cycles: an order of magnitude higher than prior studies. By 3D printing a mendable thermoplastic onto woven glass/carbon fiber reinforcement and co-laminating with electrically resistive heater interlayers, we achieve in situ thermal remending of internal delamination via dynamic bond re-association. Full fracture recovery occurs below the glass-transition temperature of the thermoset epoxy-matrix composite, thus preserving stiffness during and after repair. A discovery of chemically driven improvement in thermal remending of glass-over carbon-fiber composites is also revealed. The marked lifetime extension offered by this self-healing strategy mitigates costly maintenance, facilitates repair of difficult-to-access structures (e.g., wind-turbine blades), and reduces part replacement, thereby benefiting the economy and the environment.