NDT of adhesive joints-current capabilities and future needs

Summary form only. Defects in adhesive joints fall into three main categories:- complete disbonds or voiding/porosity in the adhesive; poor cohesive properties of the adhesive due to, for example incorrect mixing or cure; poor adhesive-adherend interfacial properties. The detection of disbonds or voiding presents few technical problems, though the inspection may be slow if large areas have to be covered. The detection of poor cohesive properties can be done ultrasonically though it is somewhat more difficult than the detection of disbonds. Unfortunately there is no currently available technique for the detection of poor interfacial properties and it is the interface that is the source of the majority of premature joint failures. The author describes possible methods that have been investigated for the monitoring of interfacial properties and discusses their potential. Ultrasonic reflection coefficient measurements are probably the most developed of the possibilities