13.1 Two wooden beams are butt-jointed using an epoxy adhesive as shown in the following diagram. The adhesive was stirred before application, entraining air bubbles which, under pressure in forming the joint, deform to flat, penny-shaped discs of diameter 2a = 2 mm. If the beam has the dimensions shown, and epoxy has a fracture toughness of 0.5 MN m 3/2, calculate the maximum load F that the beam can support. Assume K = Yo√ла for the disc-shaped bubbles, where Y = 0.64. Answer 4.65 kN Joint IF F12 t=b=0.1 m; /=2m F/2