Automated Manufacture of Damage Detecting, Self-Healing Composite Cryogenic Pressure Vessels

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.