Waterproofing of Strain Gauges for Underwater Applications

To measure strain in underwater applications, it is required to carry out waterproofing of strain gauges to protect them from the water ingress. In this work a novel approach using Polyurethane (PU) sealant has been adopted for the waterproofing. The approach was demonstrated on a composite laminate. Strain gauges were bonded on the laminate and PU sealant was applied over the gauges. Strains of PU sealant coated gauge and bare gauge is compared to see the effect of coating the gauge with PU sealant. Experiments were performed to measure strains in three cases - before application of the sealant, during curing of the sealant and presence of water over the sealant. In all three cases, the strains were found to be in accordance with each other. Strain value of PU sealant coated gauge varies less than 2 % of the bare gauge.