Energy-Absorbing Structural Epoxy Resin for "Silent" Composites

1Advanced underwater vehicles currently require a thick outer coating of elastomer to dampen noise radiating from excited structures to seawater. This increases weight, size, drag and detectability if the coating is damaged. Foster-Miller proposes to reduce the acoustic coating requirement more than 60% by making the composite structures intrinsically energy-absorbing. In Phase I, we will combine commercial materials to produce a semi-interpenetrating network (SIPN) epoxy/elastomer resin that maintains structural integrity because of separated phase morphology, absorbs energy over a broad range of frequencies (100 to 4000 Hz) and temperatures (-10 C to 40 C) and is processible via filament winding. We will apply our experience in undersea acoustic materials, polymer design, polymer synthesis and composite processing to provide the Navy with a complete evaluation of key technical issues, including: tailoring the SIPN in both acoustic and structural properties, processing the SIPN into composites and measuring acoustic and mechanical properties. Phase I will demonstrate the feasibility of producing "silent" composites that maintain the strength and stiffness of unmodified composites. In Phase II, we will refine the process and filament-wind prototype 21 in., heavy-walled composite tubes, 48 in. in length, with end fittings for testing at NUSC.