|Acquisition Program: ||PMS 450, PMS 377|| Objective: ||Develop cost effective coatings on composite materials for insertion into naval propulsion (in air and in water) and lift fan systems that improve durability by enabling the composite blades to become highly resistant to erosion from cavitation, sand, mist, rain, or sea-water spray while providing compatibility with geometry and ease of installation.
|| Description: ||The use of composite materials for underwater propulsors (ships and subs) and propulsion and lift fans (for air-cushion vehicles such as LCACs) has the potential to greatly improve various metrics, including: stringent fabrication tolerance at reduced procurement cost, hydrodynamic efficiency leading to reduced life-cycle costs, cavitation, radiated noise and weight. Recent efforts have demonstrated improvements in the cavitation erosion resistance of fiber-reinforced polymers (FRP), although their improved performance still remains well below traditional metallic materials. A multifunctional composite material that provides both good structural properties and high resistance to erosion from a multiple of sources is desired. Cavitation, characterized by the sudden formation and collapse of low-pressure bubbles as the liquid pressure is reduced to the vapor pressure, subjects adjacent structural materials to repeated and concentrated shock and microjet impact loading. This dynamic loading can have an even more profound effect on strain-rate sensitive materials such as FRP. Indeed, traditional lightweight materials such as aluminum or FRPs do not perform well in a cavitating environment.
This topic seeks innovative coating solutions that address the resistance to cavitation erosion, and impact due to sand, mist, rain, or sea-water spray of FRP materials. Desired coating material attributes include:
o Erosion resistance in excess of or equivalent to traditional metallic materials (e.g., 316 SS, Nickel-Aluminum-Bronze, high-strength aluminum, etc.)
o Low cost
o Structural properties consistent with service loads
o Scalable manufacturing
o Compatible with the marine environment
o Conformable to the target application’s geometry
|| ||PHASE I: Establish geometry, operating conditions, and material requirements relevant to Navy applications. Conduct survey of new and existing materials for further consideration. Identify and implement preliminary sub-scale test methods for assessing erosion resistance to cavitation and impact due to sand, mist, rain, and/or sea-water spray. Perform trade-off analysis considering cost, mass, structural properties, and erosion resistance to downselect to several candidate materials to be considered for Phase II effort.
|| ||PHASE II: Qualify candidate materials for Navy applications through extensive testing including cavitation erosion performance, abrasion, impact, water absorption, and other environmental effects. Demonstrate affordable manufacturability for large-scale applications.
|| ||PHASE III: Working with Navy and/or industry, as applicable, to develop and demonstrate material concept(s) in “mid-scale” trials. The trials should include a controlled demonstration with hardware of a nominally 4-5 ft diameter composite propeller and/or lift fans, installed and demonstrated on a surface ship as main propulsion, or on an LCAC as a lift fan or thruster.
PRIVATE SECTOR COMMERCIAL POTENTIAL/|| ||DUAL-USE APPLICATIONS: The advanced coating materials developed would have direct application for commercial manned and unmanned surface vessels used in oceanographic surveying, off-shore oil exploration and on salvage ships. Additionally, high-performance marine composite materials have nearly unlimited applications in shipbuilding.
|| References: ||1. Rathnam, K.V. and Peel, L.D., “Impact Resistant Fiber Reinforced Elastomer Composite Materials,” Proceedings of the SAMPE 2004 Conference, May 2004, Long Beach, CA.
2. Kendrick, L.H., and Caccese, V., “Development of a Cavitation Erosion Resistant Advanced Material System,” ADA441468.
3. Bhagat, R.B., “Cavitation Erosion of Composites – A Materials Perspective,” Journal of Materials Science Letters, 6(12), 1987, pp1473-1475.|
|Keywords: ||Composite materials, coatings, erosion, cavitation, marine structures, composite propeller, low cost|