Issue 47

V. Rizov, Frattura ed Integrità Strutturale, (2047) 468-481; DOI: 10.3221/IGF-ESIS.47.37 478 The strain energy release rate in non-dimensional form is presented as a function of 2 1 / H H ratio in Fig. 4 for the two beam configurations shown in Fig. 3 at 2 / 0.75 a l  , 2 1 / 0.6 g g E E  , 3 1 / 0.5 g g E E  , 1 1 / 0.4 r g E E  , 2 1 / 0.6 r r E E  , 3 1 / 0.8 r r E E  , 1 1 / 0.6 f g E E  , 2 1 / 0.7 f f E E  , 3 1 / 1.1 f f E E  , 1 1 / 0.6 g H E  , 3 1 / 0.7 H H  and 1 2 3 0.7 m m m    . Figure 3 : Two three-layered four-point bending beam configurations with delamination crack located between (a) layers 2 and 3 and (b) layers 1 and 2. The curves in Fig. 4 indicate that the strain energy release rate decreases with increasing of 2 1 / H H ratio. Besides, it can be observed in Fig. 4 that the strain energy release rate is higher when the delamination crack is located between layers 1 and 2. This behavior is due to the fact that when the delamination crack is located between layers 1 and 2, the stiffness of left- hand crack arm is lower. The influence of the 2 1 / g g E E ratio on the delamination fracture is investigated too. For this purpose, the strain energy release rate in non-dimensional form is presented as a function 2 1 / g g E E ratio in Fig. 5. The three-layered four-point bending beam configuration with a delamination crack located between layers 1 and 2 is analyzed (Fig. 3b). It can be observed in Fig. 5 that the strain energy release rate decreases with increasing of 2 1 / g g E E ratio. The effect of the non-linear mechanical behavior of the material is elucidated also. For this purpose, the strain energy release rate obtained assuming linear-elastic behavior of the inhomogeneous material in each layer is presented also in Fig. 5 for comparison with the non-linear solution. The linear-elastic solution is derived by substituting of i H  in formulae (12), (19), (20) and (32) since at i H  the Ramberg-Osgood stress-strain relation (6) transforms in the Hooke’s law. One can observe that the non-linear behavior of the material leads to increase of the strain energy release rate (Fig. 5).