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Underwater Diver-Applied Composite Patch Repair for Crack Arresting


OUSD (R&E) CRITICAL TECHNOLOGY AREA(S): Advanced Materials OBJECTIVE: Develop an underwater, diver-applied, composite patch repair capability for crack arresting that is applicable to multiple hull materials and will be considered for longer-permanent repair or be categorized as a temporary emergent repair. DESCRIPTION: The superstructure of the Ticonderoga-class cruisers, which is composed of aluminum (Al) alloy 5456, has been determined to be susceptible to cracking across its aluminum alloy. The Navy recognized that this aluminum alloy will become sensitized at higher temperatures as a result of the heat treatment processing received during the manufacturing process. As a result of this sensitization, there have been many issues with cracking in the aluminum. Sensitization refers to a harmful microstructure that increases the corrosion susceptibility in Al 5XXX series alloys. Sensitized Al is observed in 5XXX alloys that have magnesium contents greater than 3 percent weight content and operate at temperatures reached by simple solar exposure. Conventional repairs for the Ticonderoga-class superstructure must be done in a “dry environment”. Furthermore, they include completely cutting out and removing the affected sections, and conducting hot work (welding) repairs. Moreover, the Independence class Littoral Combat Ships (LCS) and the Expeditionary Fast Transport (EPF) ships have also utilized aluminum for structural components in the hulls and superstructures, raising additional concerns regarding stress corrosion cracking, fatigue, and sensitization. In some situations, a weld repair cannot be performed, as called out in ASTM G67, which states “a mass loss greater than 60 mg/cm2 cannot be welded because cracks will form in the area adjacent to the weld repair”. Where applicable, conventional repairs are time consuming and costly. For instance, a waterborne weld repair can take upwards of $500,000 and two weeks to repair. Dry docking a ship requires a cost of approximately $1,000,000 and repairs take one month at minimum. Additionally, the burden to prepare and move the ship to dry dock falls on the crew, reducing their availability for other tasking. A case study of the Royal Navy and its Type 21 Frigates has shown that an above water composite repair patch procedure is an effective alternative to conventional repairs. It has also shown that this type of repair could be considered durable, and potentially classified as a long-term temporary repair lasting at least 10 years in service. In response, the U.S. Navy has developed an approved above water procedure for repairing an affected aluminum alloy area of concern and preventing crack growth while restoring the integrity of the compromised area utilizing composite patching. The U.S. Navy has applied this above water composite repair patch procedure to the 5456-H116 aluminum alloy superstructures and decks aboard CG-47 class ships, and is currently in service aboard eleven different ships of that class. Since then, the conceptual viability of underwater composite patching technology has been proven through initial research conducted at the Naval Post-graduate School (NPS). This work is publicly available in Lieutenant Commander Robyn W. Bianchi’s 2018 Thesis and Dissertation, which can be located at the web address under the “References” section. The Navy desires an underwater composite patching technology that will be able to withstand the loading experienced in the dynamic environment of a waterborne US Navy vessel. The proposed solution will have a minimum lifespan of 6 months to 1 year in the saltwater environment across a temperature range of 40 to 90ºFahrenheit for cracks measuring up to 12 inches in length. This flexibility will allow for more robust Shipyard planning. The successful proposer will also investigate, estimate, simulate, and verify the repair’s expected lifespan across the extended underway periods of US Navy vessels. The proposed underwater composite patching solutions will also be applicable to hulled vessels of varying materials, including composite, aluminum, steel, and fiberglass. While these cracks are well within the Navy’s capabilities to repair, an underwater, diver-applied composite patch offers the warfighter the potential to extend operational time and save money. Currently, weld crack repairs on steel hulled vessels are common. A small crack weld repair on a steel hulled vessel costs just under $400,000 and takes 10 days for vessels that have a refined/approved procedure. Aluminum hulled vessels currently cannot be welded underwater in accordance with an approved procedure, thus increasing the 10 day timeline to as long as one month with costs exceeding $1,000,000. The ideal patching capability proposed will cost less than $1,000 per application and would require 2 days or less for repair time. This repair time must encompass the time necessary for divers to apply the patch as well as the total cure time. The proposed composite patching technology will delay or eliminate the need for crack repairs outside of a ship’s regularly scheduled dry dockings. Currently, crack repairs occur at least once per fiscal quarter. Permanent crack repairs can then be scheduled once the ship enters its extended dry-docking availability. This capability will lower demand within our Navy shipyards and reduce the need to contract private yards. The proposed solution’s threshold use will be temporary emergent repairs whereas its objective use will be for permanent patch repair for crack arresting. This technology could also be applied to commercial vessels and help them save cost or time associated with weld repair delays as there are very few solutions of this nature commercially available. Most solutions pertain to sail boats that are made of fiberglass or composite hull structures. All commercial vessels with aluminum or steel hulls require either underwater welding or dry-docking solutions. The technology will be tested against the qualification requirements of Department of Defense Manufacturing Process Standard, MIL-STD-1689A, Fabrication, Welding, and Inspection of Ship Structure. PHASE I: Develop a concept for the fabrication and application process of underwater composite patching. Determine the feasibility of the proposed composite patching and recommendations for improvement on any associated manufacturing processes. Feasibility shall be demonstrated by a combination of analysis, modeling, and simulation as stated in the Description. The Phase I Option, if exercised, will include the initial design specifications, load testing results, and capabilities description to build a full scale prototype solution in Phase II. PHASE II: Develop a full scale prototype and procedure shall be developed and delivered to the Government for final testing and evaluation. The system shall include recommended composite and epoxy type and manufacturing materials and procedures. An initial evaluation of the system will be performed on a waterborne US Navy vessel or representative substitute platform. The system will also go through preliminary qualification testing based on a test plan developed by the Government IAW MIL-STD-1689A. Final test and evaluation will take place at the Navy Experimental Diving Unit, Panama City, FL. Lastly, it will be determined if composite patching repairs could be used as permanent or temporary emergent repairs. Describe in extensive detail the conditions under which the solution would be considered as a permanent or temporary emergent repair, including but not limited to water temperature, salinity, and other criteria. PHASE III DUAL USE APPLICATIONS: Support the Navy in transitioning the technology to Navy use. Deliver an operational system to the Government for qualification testing in accordance with MIL-STD1689A, Fabrication, Welding, and Inspection of Ship Structure. Provide composite and epoxy materials necessary for qualification testing. Provide all required training to safely conduct the procedure. After successful qualification, deliver the systems to the Navy’s Emergency Ship Salvage Material (ESSM) program where they will be maintained and ready for issue. Train ESSM personnel in the operation and maintenance of the delivered systems. Provide all drawings of the system to support fabrication, maintenance, and overhaul. This technology also has the potential to impact commercial industry. The concept of saving time and money with waterborne patch repairs vice entering dry dock or contracting divers to perform underwater welding would be applicable to maritime vessel maintenance and repair communities associated with commercial shipping and transportation industries. REFERENCES: 1. R.W. Bianchi, Diver-Applied Underwater Composite Patch Repair on Aluminum Hulls, Naval Post Graduate School, Monterey, CA, 2018. 2. R. C. Allan, Carbon Fibre Reinforcement of Weld Repairs to the Aluminium Alloy Superstructure of HMS Active, Chicago: AMTE(S) TM83475, 1983. 3. R. M. Jones, Mechanics of Composite Materials, 2nd ed., New York, NY: Taylor & Francis Group, LLC, 1999. 4. D. Hart and J. J. Noland, "Composite patch repair installation procedure for 5XXX aluminum alloy affected by stress corrosion cracking," Naval Surface Warfare Center Carderock Division, West Bethesda, MD, 2015. 5. D. Popineau and P. Wiet, "Subsea pipeline repair by composite system," in Society of Petroleum Engineers, Abu Dhai, 2012. KEYWORDS: Composite repair; Underwater repair; Navy Ship repair; Composite Patch; Underwater Composite Patching; Navy Hull Patching
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