Degradation of structural adhesive bonding joints on ship exposure decks

The degradation process of adhesive bonding layers on ship exposure decks was examined via an exposure test using adhesive bonding joint specimens under tensile shear load. The degradation was evaluated by the delamination and the deformation of the adhesive layer. The degradation initiated in summer, which was more significant for the specimens located at exposed areas of the ship than those in the engine room (i.e. not exposed area). Environmental measurements revealed that, in summer, the daily highest surface temperature was greatly raised at the exposed areas that, however, exhibited equal or lower average values compared to the engine room. The degradation of an adhesive bonding joint would initiate relatively rapidly in a high-temperature environment. This indicates the highest temperature is a more important factor for adhesive bonding durability than the average temperature. The tensile test conducted after the exposure test showed that the degradation progressed from the adhesive layer edge. The surface temperature on an ocean-going ship was also measured to examine the temperature condition, revealing more severe values than those on ships in mid-latitude regions such as Japan. The design temperature for adhesive bonding joints should be estimated as at least 70 degrees C for exposed areas.