A Comparison of Different Methods for the Detection of a Weak Adhesive/Adherend Interface in Bonded Joints

There are three main classes of defect which occur in adhesive joints: complete disbonds, voids or porosity in the adhesive layer, poor cohesion (ie a weak adhesive layer) and poor adhesion (ie a weak interface between the adhesive layer and one or both adherends). The detection of disbonds, voids and porosity generally presents few problems and significant progress has been made towards the development of techniques for monitoring the cohesive properties of the adhesive layer [1]. However, there is no satisfactory method for the detection of a weak interface between the adhesive and the adherend(s) and this remains one of the major challenges in NDE. It is the interlayer which is affected by the common problem of slight contamination due to, for example, grease on the adherend surfaces prior to bonding. The adhesive/adherend interface is particularly important in aluminium-aluminium joints in which an inappropriate interface structure can cause greatly enhanced susceptibility to environmental attack [2]. Inspection of the interlayer is difficult because it is frequently only of the order of 1µm thick, compared with an adhesive layer thickness of the order of 100 µm

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An Optimal Expected-Time Algorithm for Voronoi Diagram of Polygonal Objects

Adhesive bonding of aluminum holds some possible advantages over the traditional methods of construction in the aerospace industry. However, there is uncertainty about the mechanism of adhesive bonding and the changes occurring during environmental attack which reduce the bond strength. An improved understanding will aid in the development of better techniques for non-destructive testing (NDT) of joints by determining what properties should be measured and will lead to the development of better adhesive systems