The prestressed end-notched flexure fracture specimen is developed in
the present work, which combines the traditional double-cantilever beam
and the end-notched flexure specimens in a very simple way. The most
important features of the new beam-like specimen are that it is able to
provide any combination of the modes I and II strain energy release
rates and it may be performed by using a simple three-point bending
fixture. The mode-I part of the strain energy release rate is fixed by
inserting a steel roller, which causes a fixed crack opening
displacement. The mode-II part of the energy release rate is provided
by the external load. A simple closed-form solution using beam theory
is developed for the energy release rates of the new configuration. The
applicability and the limitations of the novel configuration are
demonstrated using unidirectional glass/polyester composite specimens.
If only propagation onset is involved then the prestressed end-notched
flexure specimen can be used to obtain the fracture criterion of
transparent composite materials in a very simple way.