= (1) We consider the case of a beam or plate splits along its mid-plane where the total height is 2h, the length of the crack is a, the overall length of the beam is L, and the out-of-plane depth is b, as shown in Figure 1. The material is assumed to be isotropic, homogeneous and linear elastic, with E E/(1 2) for plane strain conditions (i.e. b a) and E = E for plane stress conditions (i.e. b top P. bottom P, P 12 P P II 11 a a h h h h a h h L Mode I + Mode I Mode II FIGURE 1. Analysis of fracture in composite beam/plate by linear superposition. 1