INDEX adhesives joints

The reason for the visibility of cracks is seen in Fig. 7.9. A light source shining on an adhesive joint is not much reflected at the adhesive interface, because the difference in refractive index at the interface is not large. Therefore, in reflection the adhered interface looks dark because almost no light is reflected... 

Thus, independent of the dimensions of the test pieces, the strength values obtained are always comparable. These relationships refer also to bonded joints for which the term adhesive strength has become established for destructive testing of overlapped test pieces (Figure 10.2). It is abbreviated by the Greek letter r (pronounced tau) referenced with the index B ... 

The other index of adhesion durability is the Coefficient of Variation (CV) that is defined as the standard deviation divided by the average strength. Adhesively bonded joints show a fairly good correlation between the CVand the C/T. A low CVunder 0.15 is necessary and 0.10 is desirable for highly durable adhesion. Interfacial fracture increases the CV. A large CV condition over 0.2 gives unreliable joints and should be avoided (Haraga 2008). 

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