Ultrasonic and thermographic analysis of composite adhesive joints subjected to accelerated aging

Bonded joints provide a means of assembling that reduces the stress concentration. However, to ensure the joints have a good mechanical strength, is necessary to control various factors including the adhesion of the two surfaces of the joints. Glass-fiber reinforced thermosetting plastic (GFRP) adhesive joints were characterized through ultrasonic imaging (UT) and lockin thermographic (TT) analysis in order to assess the adhesion quality before being subjected to static tensile mechanical tests. Furthermore, samples of the same lot were subjected to accelerated aging cycles to evaluate their behavior in temperate zones. They were taken from the climatic chamber monthly and, before being subjected to mechanical testing, were again analyzed by non-destructive techniques. The mapping of each sample using non-destructive testing has been obtained. The visual images , obtained after the mechanical tests, have been compared with defects highlighted with non-destructive controls. The ability of lock-in thermography in investigating inadequate bonding between the adherents has been validated by the consistency of the results with the well-established ultrasonic testing.