Correlation of NDE Parameters with Fatigue Lifetime of Aircraft Adhesive Bonds

Abstract

Various NDE methods and techniques have recently been developed to characterize adhesive bonds. These techniques simply detect voids. However, information about the presence of voids does not necessarily reflect the strength of the joints [1]. Moreover, it has been shown by Schonhorn [2] that the static failure load of joints is not largely affected by the size of a defect. Although this may be true for monotonic loading, it may not be the case under fatigue loading which is more representative of the in-service conditions. Under fatigue loading, inherent voids, cracks etc. can coalesce and form a considerably larger flaw which will eventually consume a very large portion of the bonded area. Fatigue failures account for a large number of in-service material failures of joints. Therefore, it is important to relate the size and number of defects detected by NDE methods to a quantity such as fatigue lifetime; this is the focus of the present work.