Determination of hygrothermal ageing effects in sandwich construction joints using thermoelastic stress analysis

Typical marine sandwich construction composite tee joints have been exposed to a hygrothermal ageing environment and were simultaneously subjected to one of three loading conditions: free standing, static compression and cyclic compression. The joints were removed from their environment for experimental evaluation after 60 and 144 days of ageing. The experimental approach adopted for this work was thermoelastic stress analysis (TSA), using the DeltaTherm equipment to obtain full-field thermoelastic data from the region of interest in the structural specimens. Readings from the aged joints have been obtained and compared to reference readings taken from an unaged joint. The implications of the changes in thermoelastic signal in specific regions of the joints have been discussed. The work shows the potential for using TSA to detect material changes due to hygrothermal ageing and for establishing damage severity levels resulting from mechanical loading during hygrothermal exposure.