A randomly oriented, short-fiber-reinforced composite plate having a central through-thickness crack of length 2a is subjected to a uniaxial stress , as shown in Figure 9.1. If the composite has a fracture toughness K = 50 MPa m/2 and the applied stress o = 200 MPa, determine the critical crack size, a for unstable and catastrophic crack growth. 4a 2a Crack Elliptical zone assumed to be relaxed due to presence of crack