The energy release rate for interface crack propagation for the Microbond-T
est specimen is calculated by using several stress analysis methods. For th
e corresponding finite element calculation an axisymmetrical model (ellipti
cal droplet) and linear elastic material properties are used. The analytica
l approximations use several stress analysis methods to obtain the energy r
elease rate.
The resulting energy release rate curves suggest that the debonding process
can be described at least partially as a stable crack propagation along th
e interface. Some experiments confirm this prediction. The matrix droplet c
ontribution to the energy release rate can be considerable. Because of the
very complex stress fields in the droplet a simple analytical approximation
cannot be given. The qualitative dependences on the material properties an
d on the geometry can be explained from the presented analysis. The remaini
ng correction factor can be obtained from a numerical calculation.