Study the stability of crack propagation in a DCB specimen made of a polymeric material for which the R-curve is parameterized by KR (Aa) - KSS-(KSS - KIN) exp(-E Aa). where KS is the steady-state value of the fracture toughness = 1.5 MPa-m, KIN is the initiation fracture toughness=1.0 MPa-m. Aa is the crack advance (in m), and is a constant. The DCB specimen characteristics are Thickness 2h = 0.01 m - Initial crack length 4-0.05 m Width w=0.02 m Stiffness E = 3.0 GPa Discuss, as a function of the material parameter & the critical values of the applied load P for which: (1) crack propagation will initiate and (ii) becomes unstable.