Issue 47

V. Rizov, Frattura ed Integrità Strutturale, (2047) 468-481; DOI: 10.3221/IGF-ESIS.47.37 470 of adhesively bonded lengthwise vertical layers which exhibit material inhomogeneity in both width and length directions. The number of layers is arbitrary. Each layer has individual width and material properties. Besides, each layer exhibits non- linear mechanical behavior of the material which is treated by applying the Ramberg-Osgood equation. A notch of depth, 2 b , is introduced in the right-hand lateral surface of the beam in order to generate conditions for delamination fracture. The delamination crack is located symmetrically with respect to the mid-span. Besides, the delamination crack is located arbitrary between vertical layers. Therefore, the cross-sections of the two crack arms have different widths denoted by 1 b and 2 b for the left-hand and right-hand crack arms, respectively. The notch divides the right-hand crack arm in two symmetric segments of length, a , each. Apparently, the two segments of the right-hand crack arm are free of stresses. It should also be mentioned that the delamination crack is located in the beam portion, 2 4 B B , which is loaded in pure bending (Fig. 1). Due to the symmetry, only half of the beam,   1 2 3 1 2 2 l l x l l     , is considered in the present fracture analysis. Figure 1 : Loading and geometry of the multilayered four-point bending beam configuration. The delamination fracture behavior is studied in terms of the strain energy release rate, G . For this purpose, the strain energy release rate is written as [16] * dU G dA  (1) where * dU is an elementary change of the complementary strain energy, dA is an elementary increase of the delamination crack area. Since dA hda  (2) formula (1) takes the form * dU G hda  (3)