Acoustic and Magnetic Signature Reduction for Outboard Engines Using Metal Matrix Composites

Metal matrix composites (MMCs) are the proposed replacement materials for the ferromagnetic parts that exist in an outboard engine. MMCs have specific stiffness properties 2 to 4 times that of aluminum alloys, steel, and titanium, while having equal or greater specific strength. The resulting parts are extremely light weight yet robust enough to handle high strength applications typically reserved for steel, such as connecting rods, wrist pins, and crankshafts. The technical objectives of Phase I are to: (1) demonstrate cost effective near-absolute net-shape MMC engine components that will contribute to making a "magnetically invisible" outboard using the MIT licensed pressure infiltration casting process; (2) prove feasibility of improved engine performance and efficiency by reducing mass of rotating engine parts; (3) determine magnetic components and rank them based upon magnetic signature contribution; (4) evaluate performance and cost to identify appropriate material and manufacturing processes. A MMC connecting rod will be demonstrated to reduce mass and eliminate magnetic signature. All other contributing magnetic sources will be examined. In the option phase, cost and performance of replacement materials will be evaluated. BBN Laboratories, experts with marine acoustics and vibration control, will provide consulting on potential benefits of MMCs.