NASA Funding Research on Self-Repairing Composite Materials

NASA is funding two research programs focused on developing advanced carbon composite materials that can detect and repair damage they suffer.

The space agency is funding the research under its Small Business Technology Transfer (STTR) program.  It recently selected two projects for continued funding under Phase II of the program, which provides contracts for up $750,000 apiece.

One project selected for negotiations is being undertaken by Aurora Flight Sciences Corporation of Manassas, Va., and the University of Massachusetts — Lowell. The research proposal is for the automated manufacturing of damage detecting, self-healing composite cryogenic pressure vessels.

“This combination of materials and manufacturing processes lends itself attractive for applications within NASA’s Space Exploration program such as large pressure vessels, vehicles, and habitat modules,” the partners said in the proposal summary. “The lifetime and reliability of these structures will be improved as they become larger and lighter weight, and are sent deeper into space for future missions. Clearly, after these structures are launched into space, it is often not practical to service them in the event of any damage. The ability to detect damage and to self-heal will be advantageous in such cases.”

The second project is from Nanosonic of Pembroke, Va., and Colorado State University at Fort Collins. The partners plan to develop “revolutionary multifunctional, super lightweight, self-healing and radiation shielding carbon fiber reinforced polymer (CFRP) composites as a viable lightweight material for space applications such as primary or secondary structures on NASA vehicles, habitat modules, and pressure vessel structures. While current composites are lightweight, they do not offer reliable methods for damage inspection. These advanced materials offer the ability to self-heal upon impact and allow for micro crack damage inspection via DC or RF measurements”

Summaries of the two projects are below.

Automated Manufacture of Damage Detecting, Self-Healing Composite Cryogenic Pressure Vessels
Research Subtopic Title: Smart Structural Composites for Space

Aurora Flight Sciences Corporation
Manassas, VA

University of Massachusetts – Lowell
Lowell, MA

Principal Investigator/Project Manager
Dr. Konstantine Fetfatsidis

Estimated Technology Readiness Level (TRL) at beginning and end of contract:
Begin: 4
End: 5

Technical Abstract

After successfully demonstrating the basic functionality of a damage-detecting, self-healing ‘smart’ material system in Phase I, Aurora and UMass Lowell aim to advance the material technology to a TRL 5 in Phase II. The team will use their ‘smart’ material system to design and manufacture various scaled-up core-stiffened composite specimens in application-appropriate geometries, and subsequently test the specimens in a simulated operational environment that includes hypervelocity impact to simulate MMOD impacts, and thermal cycling to represent the large temperature gradients in space. Aurora and UMass Lowell will automate the resistive heating process by relying on changes in the flow of heat through the material as measured by sending electrical current through the structure and monitoring using infrared thermography. Based on the extent of damage, additional heat can be automatically triggered to accelerate healing. The team will consider the integration of the ‘smart’ material into a larger system in Phase II, including the storage of fluid within the honeycomb core cells to re-fill micro-channels. Vertically aligned carbon nanotubes (VACNTs) from N12 Technologies, Inc. will be continuously transfer-printed onto the carbon fiber prepreg slit tape and spooled for automated fiber placement (AFP). When laid down by AFP, the VACNTs will “stitch” adjacent layers together to reinforce the interlaminar region and improve the damage tolerance of the overall structure with a negligible increase in weight and thickness. At the end of Phase II, the team will work with NASA Langley Research Center’s new Integrated Structural Assembly of Advanced Composites facility to manufacture a scaled pressure vessel that will be damaged via hypervelocity impact multiple times to evaluate its self-healing performance. This scaled demonstration will enable the team to define further scale-up requirements and make cost and performance predictions for subsequent development phases.

Potential NASA Commercial Applications

The developed “smart” material has several applications within NASA. First, the smart aspects are integrated with a commercially available OOA prepreg material suitable for large, lightweight composite structures. Second, this material is compatible with AFP for cost-effective, rapid manufacture of such large, lightweight structures. Furthermore, the implementation of the smart aspects is done using automated, controlled processes. The microvascular channels for self-healing are fabricated using a FDM print-head that can be interfaced with the AFP machine, while the CNTs are transferred continuously to prepreg slit tape and spooled prior to AFP. This combination of materials and manufacturing processes lends itself attractive for applications within NASA’s Space Exploration program such as large pressure vessels, vehicles, and habitat modules. The lifetime and reliability of these structures will be improved as they become larger and lighter weight, and are sent deeper into space for future missions. Clearly, after these structures are launched into space, it is often not practical to service them in the event of any damage. The ability to detect damage and to self-heal will be advantageous in such cases. With the success of this STTR program, Aurora will have positioned itself to compete for future NASA contracts that require the manufacture of large, composite space structures similar to the Orion heavy lift launch vehicle, the SLS, and NASA’s COTS vehicle.

Potential Non-NASA Commercial Applications

As an aerospace company, Aurora designs, develops, and manufactures various primary and secondary composite structures for unmanned and manned, military and commercial aircraft. The structures, over repeated load cycles, will develop cracks that affect performance and require significant downtime and maintenance. Being able to integrate damage detection and self-healing capabilities with these structures will position Aurora to offer innovative new, “smarter” designs for commercial customers, that are more lightweight and damage tolerant. Aurora is already working on an application that detects damage and dynamically adjusts its flight parameters (e.g. lower altitude, different speed, etc.) to maximize performance prior to grounding for repairs. A self-healing system would enable the aircraft to fly for a longer period of time and complete its required mission without unnecessarily grounding the aircraft for maintenance and repairs. Furthermore, Aurora could leverage its relationship with major prepreggers such as Cytec, Hexcel, TenCate, and Toray to license the “smart” material out for subsequent sales to other industries including wind energy, automotive, and construction (e.g. buildings and bridges).

Technology Taxonomy Mapping

• Composites
• Nanomaterials
• Polymers
• Pressure & Vacuum Systems
• Processing Methods
• Recovery (see also Vehicle Health Management)
• Smart/Multifunctional Materials
• Structures
• Thermal Imaging (see also Testing & Evaluation)

Multifunctional Shielding and Self-Healing HybridSil Smart Composites for Space
Research Subtopic Title: Smart Structural Composites for Space

Nanosonic, Inc.
Pembroke, VA

Colorado State University
Fort Collins

Principal Investigator/Project Manager
Dr. Jennifer Lalli

Estimated Technology Readiness Level (TRL) at beginning and end of contract:
Begin: 5
End: 7

Technical Abstract

NanoSonic has developed revolutionary multifunctional, super lightweight, self-healing and radiation shielding carbon fiber reinforced polymer (CFRP) composites as a viable lightweight material for space applications such as primary or secondary structures on NASA vehicles, habitat modules, and pressure vessel structures. While current composites are lightweight, they do not offer reliable methods for damage inspection. These advanced materials offer the ability to self-heal upon impact and allow for micro crack damage inspection via DC or RF measurements. During the Phase I program, this phenomenon was demonstrated on multifunctional smart structural composites consisting of: carbon fiber plies, NanoSonic’s Thoraeus Rubber™ Kevlar Lightweight Shieling Veils (LSV), and our conductive self-healing microcapsules. The innovative microcapsules are comprised of a corrosion resistant HybridShield polymer shell, a resin-rich core of self-repairing, room temperature curing polymer, and Al nanoparticles to impart EMI and radiation shielding as well as a conductive pathway between the conductive Thoraeus Rubber veils to monitor both damage and repair via RF measurements. NanoSonic is working with Colorado State University, ILC Dover, and Lockheed Martin Space Systems Company to increase the TRL of this technology from 5-7 during the Phase II program via mechanical, RF, and radiation shielding measurements and space qualification testing.

Potential NASA Commercial Applications

NanoSonic’s HybridShield Metal Rubber (HS-MR) materials will be primarily transitioned as smart, lightweight, multifunctional, self-healing composites for spacecraft to further NASA Space Exploration Program. The materials shall be engineered for both primary and secondary structures, including vehicle, habitat module, and pressure vessel structures. The multifunctional MR nano-additive component of the self-healing materials formed via NanoSonic’s ESA process offer EMI and radiation shielding for enhanced long-term high altitude and space durability. Such higher specific strength self-healing composites will result in drastic reductions in uptake mass and increased reliability for more cost effective and efficient space exploration. Specifically, the composites shall monitor the extent of damage and repair such destruction throughout the lifecycle from manufacturing, to a tool drop, and in service due to micrometeoroid and orbital debris impacts on orbit. Both coupons and a targeted space demonstrator shall be produced during this program with our space partners.

Potential Non-NASA Commercial Applications
Non-NASA applications for the self-healing composites include long-term protective storage liners for food or other sensitive materials, self-sealing tires, anti-ballistic fuel tanks and life critical personnel protective equipment (PPE). The EMI and radiation shielding protective constituent offer utility as cost effective protection against electrostatic charging, radiation, and abrasion. Aerospace, biomedical and microelectronic markets would benefit from the EMI SE under repeated and severe reconfigurations. Such EMI shielding skins can be envisioned for use on aircraft, morphing unmanned aerial vehicles, antennas and space structures. Structural, high temperature, composite materials having unique dielectric and multiple controlled electromagnetic properties are possible via NanoSonic’s layer-by-layer approach. Spray ESA is envisioned as a cost-effective, environmentally friendly technology to displace sputtering and traditional dense filled composites. Metal Rubber™ fabrics and films can also function as conducting electrodes for high strain mechanical actuator and sensor devices, or as electrically conductive mechanically flexible ground planes or electrical interconnection.

Technology Taxonomy Mapping

Airship/Lighter-than-Air Craft
Coatings/Surface Treatments
Composites
In Situ Manufacturing
Nanomaterials
Outreach
Polymers
Protective Clothing/Space Suits/Breathing Apparatus
Smart/Multifunctional Materials
Spacecraft Design, Construction, Testing, & Performance (see also Engineering; Testing & Evaluation)