SBIR-STTR Award

This investigation exploits the key advantages of plastic polyurethane as a material for NSSN heads/housings. These advantages include dramatic cost reduction, due to ease of manufacturing and lower material cost, decreased weight, inherent noncorrosivity, high strength, ductility and portability. A structural analysis methodology will be developed based upon proven advanced nonlinear finite element techniques and experience with structural plastics. This methodology will be applied to the design of a Government specified outer head. A materials search and synthesis (Phase 1 Option), will be conducted in paralllel, resulting in selection of material(s). Polyurethane plastics will be selected based on maximizing strength and ductility requirements, and requirements the analytic design dictates. These selected plastics will then be processed to accurately reflect the manufacturing process and geometry of the head. Selected plastics will then be mechanically tested to obtain the mechanical parameters used in the analysis. An initial set of parameters will start the analysis and an improved set will be used in the final design. A detailed manufacturing procedure will be developed which includes mold design, preprocessing, mold prepartion, mixing, demold procedures and quality control.

In Phase I GRW showed a Photonics Head made of a neat blend of GRW urethane can survive the combined loading of hydrostatic pressure and an underwater shock. This is based on extensive investigation of the mechanical properties of urethane blends, extrapolation of stress strain results (to be finalized at the completion of Phase I) using a fluid/structure nonlinear FEA with an attachment ring redesign, and GRW's manufacturing procedure. The manufacturing procedure was applied to the casting of a Head-sized cylinder, made from an optimum blend, that tensile tests showed maintained uniform mechanical properties throughout. GRW is currently doing further development of both neat and random fiber composite urethanes to achieve the necessary material selection for Phase II. In Phase II GRW will continue selection of optimum urethane materials that meet the design loading criteria of the Heads/Housings. Tests to establish the strain rate dependency of the materials will be performed and the results employed in ETC's FEA model. Modifications to mixing machines will be made as necessary to manufacture composite Heads/Housings.

Benefits:
The exceptional manufacturing and material cost reduction of a neat (or reinforced) urethane to replace high strength, shock resistant parts in a marine environment will create a military and commercial demand for additional Heads/Housings, Masts, Transducer Housings, Hull Plates and Gratings, as well as commercial bumper parts and machinery.

Keywords:
Masts Urethane Underwater Shock High Strength Heads