A method of measuring energy dissipation during crack propagation in polymers with an instrumented ultramicrotome

In order to characterize very local energy dissipation during crack propagation in polymers, an ultramicrotome was instrumented to measure the energy dissipated during sectioning. The work to section per unit area, W-s, was measured for five different amorphous polymers [polymethyl methacrylate (PMMA), polystyerene (PS), polycarbonate (PC) and two epoxy resins] in the glassy state. When the section thickness was varied between 60 and 250 nm, Ws varied between 15 and 100 Jm(-2), depending on the material and section thickness. The method and the results are compared with other methods used for determining the energy dissipation at a local level as well as at a macroscopic level in polymers. The differences between different polymers were found to be contradictory to macroscopic fracture toughness, G(Ic), measurements. The material that showed the highest W-s had the lowest G(Ic), values reported. Possible mechanisms for energy dissipation during sectioning are also discussed.