In this case, the stress singularity becomes larger than /2. When the Material 1 is softer
then the Material 2, the transverse crack deflects to the ply-interface and becomes
delamination. The stress singularity becomes lower than 1/2. In this study, conditions
under which a transverse crack becomes a delamination are studied, and the fracture
toughness of the transverse crack is quantified and measured.
M4ateriadl Materia 2
......... .... i,- --
Singularity dominated
zone
Figure 1-5. Variation of stresses acting normal to a crack tip, when the crack reaches a bi-
material interface.
Williams [13] estimated the singularity for isotropic bi-material systems by solving
a set of eigenfunctions developed by the continuity equations of normal and tangential
stresses and displacements at the ply-interface. Ting and Chou [14] have developed
methods to predict singularity at the free edge of a ply-interface of laminated composites.
The general equations of displacement and stresses are derived in terms of arbitrary
constants. The stress singularity is determined when the boundary condition at a crack
plane and the continuity equations at the ply-interface are satisfied. Later, Ting and
Hoang [15] developed this method to predict singularity of a transverse crack in
laminated composites. Hutchinson and Suo [16] formulated a characteristic solution to