The time dependence of surface energy in cohesive fracture

The time-temperature dependence of the cohesive fracture energy is deduced from experiments on a centrally cracked sheet of butadiene-acrylonitrile-acrylic acid viscoelastic terpolymer crosslinked with an epoxy curing agent. Analytic results based upon a cylindrical flaw model of the crack permit the segregation of the fracture energy time dependence from that of the relaxation modulus.