Issue34

M. Ševčík et al, Frattura ed Integrità Strutturale, 34 (2015) 216-225; DOI: 10.3221/IGF-ESIS.34.23 222 experimental results. For the studied specimen MMB 02 the fiber bridging length is approx. 35 mm which well corresponds to the experimental observation. Figure 6 : Simplified fracture criterion based on the G tot depending on the fiber bridging length. Figure 7 : The effect of fiber bridging length on the load vs. crack length diagram ( c = 227 mm, c g = 54 mm). Crack propagation path The fracture of the laminate is often accompanied with delamination in the neighboring layers and interfaces between the layers. This phenomenon is shown in Fig. 8 where photograph of the MMB specimen after test is complemented by the crack propagation path description. Figure 8 : Propagation of the crack in multiple paths. The propagation of the crack in various paths brings another complication for the reliable prediction of the P-a diagram. For the comprehensive prediction of the P-a diagram the crack propagation in multiple paths should be captured. One of the possibilities is to plot P - a diagram for all crack propagation paths and therefore to show bounds in which the P - a diagram of the real structure will fall. The preview of such P-a diagram is shown in Fig. 9 where fiber bridging length of 20 mm is considered. Figure 9 : P-a diagram for crack propagating in path I, II and III ( c = 150 mm, c g = 38 mm).