2. (15 % of final grade) A double ended DCB specimen (Fig. 2) consists of two adhesively bonded thin plates. The plates have the thicknesses h1=2 mm and h2=3 mm. The width of the plates is w=20 mm. The length of each plate is L=250 mm. The upper plate has Young's modulus of 40 GPa and the lower plate has Young's modulus of 60 GPa. The plates are bonded by an adhesive with Young's modulus of 2.5 GPa, tensile strength of 80 MPa and toughness of 3.1 kJ/m 2 . The specimen contains a crack in the adhesive between the plates with the length of a=40 mm located at the center of the specimen. It is loaded by the forces