The Amazing Self-Healing Material

Space Concordia is participating in the second iteration of the Canadian Satellite Design Challenge. Building onto an already successful design, the next stage of our journey requires the choice of a payload. In essence, this choice will largely define the direction and scope of ConSat-2’s mission.

Following the consideration of multiple proposals for the payload, the decision was rendered in a payload determination meeting on January 25th, 2013. During this meeting, the top 5 ideas were presented. After the presentations, members got the chance to vote on the best payload. After a close race, ConSat-2's main payload was chosen to be the self-healing material. Our mission objective is to conduct a comprehensive study of the self-healing technology for spacecraft applications.

Figure 1 - A composite is made of matrix (blue) and reinforcement (yellow). (Image taken from Wikipedia)

The self-healing material is a fiber-reinforced composite. Composites are materials that are made from two or more ingredients: Matrix and reinforcement. Figure 1 shows the inside of a composite. The self-healing material uses carbon fiber as reinforcement and epoxy resin as its matrix. This material was developed in Concordia University by Dr. Suong V. Hoa, director of Concordia Centre for Composites (CONCOM), in collaboration with MPB Technologies and the Canadian Space Agency. MPB Technologies is a research and development company in the fields of telecommunications, robotics, space and photonics.

The self-healing material uses an autonomic polymer healing process. This is a three-step process that starts by a response to the trigger, immediately after the damage on the material. The second step is the transport of the healing agent to the affected area. Microcapsules are placed throughout the resin to facilitate this step. The third step is the chemical repair process. The polymerization of the healing agent does not happen at room temperature. It’s the catalyst that lowers the energy barrier of the reaction to allow the monomer to polymerize at room temperature. Figure 2 shows the healing process of a self-healing material.

Figure 2 - Microcapsule Healing Process (Credit to Xia's Academic Blog)

This kind of material had been in existence before this research. For example, one of the first uses of self-healing material was in the painting industry, where the paint is capable to heal the scratches on the surface. Initial funds from the Canadian Space Agency and MPB Technologies in 2006 started the research for the space application. These parties were awarded a patent in 2009 (US Patent 20090036568) for their success in making a self-healing material that is capable of surviving the harsh space environment. However, this patented technology has not been tested in space yet and this is where Space Concordia comes into play. We plan to study the performance of this composite in space by sending a 3U CubeSat into the low-earth orbit. Specifically, the behaviour of the healing process will be observed at a microgravity environment. Doing our experiment in microgravity is important because there are many unknowns associated with the behavior of the material in that environment. The most important of which is the behavior of the monomer and the healing in the absence of gravity. Studying the long-term effects of the radiation on the material is necessary too. Our team’s job is to design a method to autonomously conduct this experiment in space.

Figure 3 - Damage from a 1 mm debris on space shuttle's window pit during STS-7 (Credit to NASA)

Currently, there are more than 300 million pieces of space debris in the earth’s orbit. In NASA’s Long Duration Exposure Facility, a cylindrical experiment rack was placed in the orbit for 5.8 years. This rack was as big as a school bus. During its time in orbit, it recorded almost 3800 debris impacts, 90% of which were caused by particles smaller than 1 mm.  In figure 3, the damage from a particle smaller than 1 mm is shown. The propagation of the cracks is clearly visible in this window pit on board of the space shuttle. The presence of space debris is very dangerous. According to the European Space Agency, any of these objects can cause harm to an operational spacecraft, where a collision with a 10-cm object would entail a catastrophic fragmentation, a 1-cm object will most likely disable a spacecraft and penetrate the ISS shields, and a 1-mm object could destroy sub-systems on board a spacecraft. Repairing the damage is very difficult and expensive. It could take effect on board of the International Space Station. It would most likely be impossible on board of a satellite. A sophisticated satellite would cost up to US$600 million to build and up to US$400 million to launch. Damage from small debris will reduce the capability and lifetime of such expensive satellites. In fact, all spacecraft are always in risk of collision with space debris. In a recent experiment in McGill University, impact tests of pellets with a velocity of up to 9 km/s were performed. The test results showed that the self-healing material is capable to greatly decrease the propagation of the cracks within the material. This experiment was led by Dr. Emile Haddad, Dr. Brahim Aissa, and Dr. Kamel Tagziria from MPB Communications.

This self-healing material is of high interest within the aerospace community. It is capable of increasing the lifetime of a structure by 5 years. Prolonging the life of a spacecraft will decrease the required maintenance over its lifetime. For example, if implemented in the International Space Station, the advantage would be to reduce the amount of manual repairs needed on the exterior of the craft and generally improve its lifespan in orbit. Therefore, there will be an overall cost reduction for a spacecraft. One of the most dangerous issues about sending a manned mission to Mars is the passage of the spacecraft through the cloud of meteoroids. NASA is currently working on a protective shield for a future Mars spacecraft. Self-healing material could be a good candidate to be one of the layers of the shield. That's why we think this payload is the next necessary leap in spacecraft design.

Data gathered from our mission would be of interest to composite researchers and spacecraft design engineers. If this material functions as expected in space, it will be a proof of concept to spacecraft design engineers. They will be able to use its huge advantages when designing for extreme conditions like the space environment. Similarly, if the material behaves differently than expected, it will provide valuable data to composite researchers around the world. The main users of our data will be Dr. Suong V. Hoa and CONCOM. The Canadian Space Agency and MPB are potential corporate stakeholders because they provided the original funds for this research. It is important to note that this technology is of high interest to the European and Canadian Space Agencies.

 

Self-Healing Material in Pictures:

Figure 4 - The resin as seen under the microscope. The average microcapsule size is 20 um. (Credit to CONCOM and Asgar Khan Warsi)

Figure 5 - Healed crack on the surface (Credit to CONCOM and Asgar Khan Warsi)

 

Demonstration of self-healing after the impact of a 1.8 mm aluminum projectile at 600 m/s:

Figure 6 - The polished sample after the impact (Credit to CONCOM and Asgar Khan Warsi)

Figure 7 - The opposite side of the same sample after the impact (Credit to CONCOM and Asgar Khan Warsi)

 

Acknowledgements

   -  Concordia Center for Composites, Department of Mechanical and Industrial Engineering, Concordia University

   -  Department of Smart Materials and Sensors for Space Missions, MPB Technologies Inc.

   -  Shock Waves Physics Group and Department of Mechanical Engineering, McGill University

   -  Center for Applied Research on Polymers (CREPEC), Mechanical Engineering Department, École Polytechnique de Montréal

   -  Department of Chemistry and Biochemistry, Concordia University

   -  The Quality Engineering Test Establishment, Department of National Defence

   -  Institut National de la Recherche Scientifique, INRS-Énergie, Matériaux et Télécommunications

   -  Engineering Development, Canadian Space Agency

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About Mehdi Sabzalian

I've always loved everything space related. I'm really interested in working with Space Concordia because I'm looking forward to learn a lot from this project and contribute as much as a I can to build this satellite.