Durability testing and life prediction of adhesive joints

Durability testing is an important requirement in the assessment of behaviour of structural adhesive joints and in the specification of bonding systems for particular applications. A wide variety of test methods have been developed to measure degradation characteristics and it is shown that different methods exhibit varying degrees of sensitivity and discrimination between joints with different bonding conditions. The effect of stress in the adhesive on the environmental ageing process is considered, and durability test methods in which some form of load is applied to the joint during environmental exposure are reviewed. The analysis and interpretation of durability test data requires a good understanding of the mechanisms involved in the degradation process. This is also particularly important in the derivation of life prediction models, and the uncertainties of simple extrapolation of durability test information by means of acceleration factors are discussed. The use of historical data obtained from an analysis of old bonded structures to provide life prediction is demonstrated by reference to a case study of an aerospace application.