The thin-walled tubular shaft shown in figure 2 is made of a randomly oriented, short- fibre-reinforced metal matrix composite. The shaft has a longitudinal through-thickness crack of length 2a and is subjected to a torque T=1.5 kNm. If the mode II fracture toughness of the composite is Kllc =55 MPa-m1/2: 3.1 Determine the critical crack size for self-sustaining crack growth. 3.2 (12) Determine the allowable torque, T, if the crack length for the shaft in figure 2 is 2a 10 mm. Use the same dimensions and fracture toughness values that were given. (8) 2a Figure 2 OF 38 mm diameter 42 mm diameter