Issue 35

G. Kullmer et alii, Frattura ed Integrità Strutturale, 35 (2016) 368-378; DOI: 10.3221/IGF-ESIS.35.42 375 Figure 10 : Crack paths for different orientation angles of compliant changes in stiffness C OMPARISON OF CRACK PATHS FOR STIFF AND COMPLIANT CHANGES IN STIFFNESS ig. 11 illustrates the definition of the transition angles of the crack paths at region transitions. initial crack stiff stiff compliant initial crack β γ γ stiff compliant compliant Figure 11 : Definition of the entrance angle β and the exit angle γ of the crack path at region transitions. The comparison of the transition angles in Fig. 12 and the crack paths through stiff and compliant changes in stiffness in the Figs. 7, 8 and 10 show that in both cases at the transition from a compliant to a stiff region the crack grows away from the region boundary. Therefore, the transition angle from compliant to stiff according to the definition of the transition angles in Fig. 11 becomes smaller than the orientation angle of the change in stiffness. At the transition from a stiff to a compliant region, the crack grows towards the region boundary and the transition angle becomes greater than the orientation angle of the change in stiffness. Furthermore, Fig. 12 indicates that the transition angles are equal at transitions with the same stiffness mismatch independent of what causes the change in stiffness. Figure 12 : Comparison of the entrance and the exit angles depending on the type of the change in stiffness F