Fracture tests

Abstract

This chapter considers first the fracture in a bulk adhesive specimen under mode I, that is, tensile opening loading conditions. Then, the testing of adhesive joints using a linear-elastic fracture mechanics approach is considered. In these tests, the substrates are assumed to only deform in a linear-elastic manner, and any permanent deformation of the substrates is avoided. In adhesive joints, due to the directional constraint of the failure path that is often observed, it is common to encounter failures in other loading modes, in addition to mode I. Thus, mode II (in-plane shear) and mixed-mode I/II testing of adhesive joints are also considered. There is often the need to measure the resistance to fracture in a joint with flexible substrates. In this case, the assumptions of linear elastic fracture mechanics may no longer be valid, and permanent deformation of the substrates may occur. One such test is the peel test and some variants of the peel test are considered in the present chapter, with a focus on the recent development of a geometry-independent peel test.