Application of acoustic emission to study creep behaviour of composite bonded lap shear joints

The objective of this work is to define criteria to distinguish different types of rupture of composite bonded lap shear joints by using non-destructive acoustic emission method. Bonded joints of carbon-epoxy, glass-epoxy and mixed, were considered. The method is efficient to carry out the progressive damage induced by creep. The influence of some aspects related with crack initiation and growth, included in the damage propagation mechanism, are also discussed. A damage acoustic coefficient, Cd, allowing to characterize the bonded joint rupture from acoustic emission signal, is defined at the secondary stage of creep. The effects of temperature and moisture on the creep behaviour and on the corresponding AE signal were studied by comparison of cumulative counts. The obtained results showed that the acoustic signal increases in function of each of these effects.