N242-072 TITLE: Improved Heat Blanket Technology for Aircraft Composite Bonding Operations

OUSD (R&E) CRITICAL TECHNOLOGY AREA(S): Advanced Materials; Sustainment

OBJECTIVE: Develop technology capable of providing a militarized heat blanket available in various sizes that have uniform heating as far up to the edge as possible, with no heat sinks or dead spots.

DESCRIPTION: Composite hot bonder repair sets are used to apply heat and vacuum pressure to composite patches via heat blankets to achieve structurally sound repairs of aircraft structural components in the fleet. Composite aircraft structural repairs at the I-level typically are compromised due to dead spots and uneven/inadequate distribution of heat towards the ends of the blankets, leading to improperly cured repairs if the users do not know the actual heating area of the blanket in relation to the size of the repair. Lack of uniform heating leads to premature failure of bonded parts. Present composite hot bonding technology is unable to properly cure complex geometries, leading to heat sinks or improperly cured parts. The objective of this SBIR topic is to seek technical solutions from industry to this problem. The technology must be capable of providing a militarized heat blanket available in various sizes that have uniform heating as far up to the edge as possible, with no heat sinks or dead spots. Additionally, the Navy desires a system that can be used with all of the material combinations/geometries for composite components on current Navy aircraft. The radome window repair requires a cure at 365 °F (185 °C) for five hours, and then a cure at 400 °F (204.44 °C) for four hours.

PHASE I: Develop, design, and demonstrate feasibility of how the chosen technology works, how it could be adapted for the military environment, Develop a test plan. The Phase I effort will include prototype plans to be developed under Phase II.

PHASE II: Perform a current required high-temperature hot-bonded repair at a Navy site, evaluate results, determine next steps/path forward. The radome window repair requires a cure at 365 °F (185 °C) for five hours, and then a cure at 400 °F (204.44 °C) for four hours.

PHASE III DUAL USE APPLICATIONS: Successfully perform a range of high-temperature repairs on five separate layup combinations. The commercial airline industry has the same issues with heat sinks during composite structural repair and could benefit from this technology.

REFERENCES:

1. Wright Aeronautical Laboratories. "MIL-HDBK-337: Military standardization handbook: Adhesive bonded aerospace structure repair." Department of Defense, 1 December 1982. http://everyspec.com/MIL-HDBK/MIL-HDBK-0300-0499/MIL_HDBK_337_1865/
2. "AC_43-214A: Repairs and alterations to composite and bonded aircraft structure." U.S. Department of Transportation, 23 July 2016. https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC_43-214A.pdf
3. Baker, A. "Bonded composite repair of fatigue-cracked primary aircraft structure." Composite structures, 47(1-4), 1999, pp. 431-443. https://doi.org/10.1016/S0263-8223(00)00011-8
4. Katnam, K. B.; Da Silva, L. F. M. and Young, T. M. "Bonded repair of composite aircraft structures: A review of scientific challenges and opportunities." Progress in Aerospace Sciences, 61,2013, pp. 26-42. https://doi.org/10.1016/j.paerosci.2013.03.003
5. "Composite Bonding & Repair Benefits and Solutions." Composites World, 8 September 2020. https://www.compositesworld.com/articles/composite-bonding-repair-benefits-and-solutions

KEYWORDS: Aircraft; composite; structural; heat-sink; heat blanket; hot bonder

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