Adhesive fracture, definition

The main conclusion of that work was that the toughness of the adhesive joint could be defined thermodynamically as the work of adhesion W. Of course, this definition was only applicable in certain special equilibrium circumstances, when the materials were elastic and when the fracture occurred very slowly. The toughness W was measurable in a T peel test shown in Fig. 15.4. This idea explained the force F required to peel two sheets apart, depending only on W and the width of the strips b (see Section 7.7). 

All of the above conclusions have been drawn for isothermal conditions without considering a thermal fluctuation under creep conditions but which in practice represent the usual case during the service life of structural adhesive joints. Considering temperature effects in creep-dependent lifetime, prediction can either follow a worst case scenario in which the definition of the load-dependent fracture envelope or the test for compKance with predefined strain limits is carried out at the maximum temperature to he expected during service life. This conservative approach is likely to lead to excessive contingency reserves. 

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