A Study on Elastomer/Metal Bonds Applicable in Underwater Sonar Systems

Recent emphasis on the long-term performance of sonar systems requires that investigations be carried out to improve the durability of elastomer-to-metal adhesive bonds in water. A screening test of some commercially available adhesive systems was performed. ASTM-D429 test methods using both conical button specimens and peel-strips were employed. The 90-degree peel test was modified such that the effects of stress corrosion, water salinity and gas content could be examined. Most commercial systems were found to give adequate dry bond strength. Preliminary environmental aging studies also showed that thermal aging did not produce any measurable effect in accelerating the degradation of the elastomer/metal bond. However, chemical attacks from salt water under stress caused great reductions in the bond strength, especially when the oxygen supply was abundant. The weakened bonds were found to show increasingly large portions of fracture failure at the adhesive/metal interface rather than rupture failure of the bulk rubber.