Figures 5(a) and 5(b) portray the effect of fracture energy on the stress–strain curves of model I under the plane stress and plane strain conditions, respectively. It can be observed that the stress–strain curves for both cases are almost the same. Figure 5(c) represents the effect of fracture energy on the stress–strain curves under axisymmetric condition. It is seen that the axisymmetric assumption leads to lower stresses compared to the plane stress and plane strain cases. The strength of the interface is set to be 64 MPa in the calculations. Table 2 reports the elastic moduli for plane strain, plane stress, and axisymmetric conditions. The elastic moduli are almost the same for plane stress and strain conditions, while the elastic modulus for the axisymmetric case is lower than the ones for plane stress and strain cases. Moreover, it can be inferred from Fig. 5 that the fracture energy does not affect the stiffness, but it significantly influences the strength as is replotted in Fig. 6. The stiffness of model I is not affected by the fracture energy because of the same initial linear behavior of the traction-separation law. Once the maximum strength at the interface is reached, the crack starts to propagate according to different prescribed damage evolution laws, and this introduces the nonlinear mechanical response shown in Fig. 5. Figure 5 indicates that strain at failure increases with the increase of the interfacial fracture energy for all (plane stress, plane strain, and axisymmetric) cases. In addition, Fig. 6 shows that a plateau is obtained at high fracture energy values. Figure 7 portrays the von Mises stress in model I at a strain of 2%. Figures 5 and 6 and Table 2 show similar results for both plane strain and plane stress conditions. Hence, similar stress fields are expected for both plane elasticity cases as shown in Fig. 7. However, in the case of plane stress condition, the stress field in the collagen phase is more uniform than in the case of plane strain, and this indicates that collagen carries less load in the case of plane stress. In the axisymmetric case, the stresses are concentrated at the HA located in the center and are not distributed over the HA platelets as in the cases of plane stress and plane strain conditions. Hence, higher stress levels are observed compared to the plane stress and plane strain conditions at the same applied strain, which leads to faster failure for the axisymmetric condition. Generally, tensile loading is mainly carried by HA minerals while the collagen contributes by transferring the load between adjacent mineral platelets. Furthermore, the mismatch between the elastic properties of collagen and minerals causes significant sliding between them as implied by the discontinuity of the contours (see Fig. 7). The delamination starts at the ends of the crystals and then propagates along their sides.