Epoxy Based Underwater Transducer Encapsulation Material

Epoxy materials exhibit a great range of properties (from soft to hard) which leads to a great versatility in application. Epoxy is the material of choice for underwater acoustic window applications as its acoustic impedance can be made to match the acoustic impedance of sea water. Acoustic impedance can be modified over a broad range for epoxy material by changing the resin (prepolymer) to curing agent ratio in the composition. Acoustical and mechanical properties of these epoxy composition have been investigated. Sound velocity and density of materials were measured. Acoustic impedance of the materials were evaluated and compared with the acoustic impedance of sea water. Insertion loss and echo reduction of the materials were measured in the frequency range 15 kHz to 100 kHz. Insertion loss was less than 2 dB and echo reduction was more than 10 dB throughout the frequency range which is suitable for underwater transducer encapsulation material. Mechanical properties like tensile strength, elongation at break and hardness etc. were investigated, which are important for encapsulation materials to withstand hydrostatic or hydrodynamic pressure. Ageing resistance to hot air was also conducted in the present study.