Page 184 - Handbook of Adhesives and Sealants

154 Chapter Four

Figure 4.9 Effect of adhesive thickness on peel resistance of Resiweld 7007
epoxy adhesive. 7

used when one adherend is flexible enough to permit a 180 deg turn
near the point of loading. This test offers more reproducible results
than the T-peel test because the angle of peel is maintained constant
although it is dependent on the nature of the adherend.
Considerable work has been done, notably by D. H. Kaeble 12,13 and
J. J. Bikerman, 14,15 to develop formulae for the force required to peel
a flexible tape from a rigid substrate. Figure 4.12 shows those equa-
tions for a peeling force. An examination of the Kaeble formula would
indicate that the peel force is directly proportional to the adhesive
thickness. Work has shown, however, that the relationship is logarith-
mic as seen in Fig. 4.13. Considerable study has been made of the
8
effect of backing on peel force. The peel angle and the joint strength
depend on the type of backing and its thickness.