Durable, Extended-Life Radar Absorbing Material (RAM) Environmental Protection Layer - MSC P4699

The Department of the Navy (DON) has issued a broad agency announcement as part of the Small Business Innovative Research (SBIR) program soliciting proposals for the development of materials and/or processes addressing existing deficiencies related to lifespan and performance of the acoustic hose containing the sensors, strength member, and communication electronics of Tactical Towed Array Sonar Systems (TACCTAS) TB-34 Fat line and the TB-29 Thin line. The current hoses are extruded thermoplastic polyurethane (TPU) tubes reinforced with polyester or aramid ropes arranged longitudinally to prevent tensile elongation of the hose as it is towed at high speeds.  The hose protects the electronics, which are suspended in dielectric fluid from saltwater and physical damage.   The extrusion process is only able to feature parallel longitudinal reinforcements around the circumference of the hose because the extrusion process cannot accommodate off-angle fibers in a single extrusion.  Such limitations leave the hose susceptible to damage by marine life (shark bites) and sharp foreign objects (fishing gear.)  To add spiral or braded reinforcement, the hose would need to be made in multiple extrusions which tend to delaminate.  Another common problem with the current hoses is the long-term migration of water through the hose wall, due primarily to the absorption of water by the TPU. Over time, the water degrades the performance of the sensors, which limits the total lifespan.  Again, the extrusion process is not amenable to water-blocking additives or internal water blocking coatings.  The unique multi-layer reinforced polymer tube manufacturing process proposed by MSC enables a variety of solutions to the Navy’s problem.  The final important role of the hose, providing damping of boundary layer and vibrational acoustic noise to the inside components of the array, will be unaffected as the alternate material system’s acoustic loss factor can be similarly tuned to that of the current product.             The approach identified by Materials Sciences LLC (MSC) focuses on an alternative processing technique consisting of multiple layers of elastomer integrally bonded through the thickness of the tube. Each layer can be reinforced with continuous or discontinuous fibers in multiple orientations with novel coatings or additives between layers.  The resulting product can be produced continuously up to 200 ft or more.  To qualify the design, MSC will perform extensive mechanical and environmental testing to compare the puncture and moisture resistance of the chosen designs to the existing product.