Optimum materials for sonar windows must have low insertion loss and high structural performance. The team assembled for this project proposes a material screening program to map the parametric space of modified epoxy systems. The modified systems would employ aliphatic epoxy links or liquid rubbers to lower the sound speed; thermoplastic microspheres to match the speed of sound and density of water; carbon nanotubes as a non-intrusive damping filler to mitigate shear resonances that increase insertion loss at oblique incidence angles; and chopped organic fibers for structural reinforcement. Each design criterion for the final system will be fulfilled by contributions from multiple ingredients, allowing leeway to manipulate the properties. Phase I lab tests will monitor the sound speeds and dynamic properties to develop a framework for Phase II optimization studies. The team includes experts from Materials Science, Acoustical Engineering and Underwater Acoustics and is well-equipped to solve the challenges of complex material systems at lab-scale and large-scale. In addition, the team will have full access to the synthesis, processing and testing infrastructure at the University of Southern California Composites Center, and the team includes the M.C. Gill Corporation for commercialization of the technology developed through this project.
Benefits: The most obvious application is sonar domes for the Navy, commercial fishing industry, and underwater oil explorations. Other applications of this research include radar domes for airplanes and various medical appliances. Wave-speed controlled, mechanically tough epoxy thin layers with damping additives would have application to increasing the transmission loss of composite laminates used for commercial airplanes. Through impedance mismatched interfaces it would be possible to create quieter cabins for commercial airplanes. Also the carbon nanotube-epoxy system could be modified for film applications that could reduce the weight of constrained layer dampers (CLD) in airplanes and space shuttles.
Keywords: Sonar, Nanotube, Epoxy, Microsphere, Sound Speed, Dynamic Shear Modulus
