Fracture Surface Energy of glassy polymers

L. H. Lee, "Surface Free Energies and Fracture Surface Energies of Glassy Polymers," in Physical Aspects of Polymer Surfaces, K. L. Mittal, Editor, Vol. 1, p. 523, Plenum, New York (1983). ... 

SURFACE FREE ENERGIES AND FRACTURE SURFACE ENERGIES OF GLASSY POLYMERS... 

R. P. Kusy and M. J. Katz, Generalized theory of the total fracture surface energy for glassy organic polymers, Polymer 19, 1345-1357 (1978). 

The fact that even the rapid deformation of a glassy polymer under concentrated stresses entails considerable local plastic deformation immediately suggests that the molecular properties, which influence yielding and flow, are also effecting Gc and thus the impact strength. The data compiled in Table 9-II reveal this dependency of Gc on temperature, rate of deformation, and molecular properties. A possible relation between molecular relaxation processes and fracture surface energy of polymers has been pointed out in many of the cited references (e.g. [14, 19, 22, 24, 25, 54,63,... 

Ber Berry, J. P. Fracture processes in polymeric materials. IV. Dependence of the fracture surface energy on temperature and molecular structure. J. Polym. Sci. Part A 1 (1963) 993-1003. 68Key Key, P. L., Katz, Y., Parker, E. R. An application of fracture mechanics to glassy plastics. 

On the basis of the results shown in Table 13.1, Berry concluded that the largest contribution to the surface energy of a glassy polymer comes from a viscous flow process that in PMMA, he suggested [14], was related to the interference bands observed on the fracture surfaces, as seen in Figure 13.6. He proposed that work was expended in the... 

In the following sections, we shall discuss the effects of molecular weight, crack speed and molecular orientation on effective fracture surface energy, fracture energy and fracture toughness of glassy polymers. Polymethyl methacrylate will be used for illustration. Other variables, e.g., temperature, sampl thickness, etc., have been well discussed in the literature, we do not include them in this section. 

In several glassy polymers [22,23], such as the polycarbonate shown in Figure 13.9, a complication occurs in that a thin line of material called a shear lip forms on the fracture surface where the polymer has yielded. Analogous to the behaviour of metals, it has been proposed that the overall strain energy release rate G is the sum of the contribution from the craze and that from the shear lips. To a first approximation, we would expect the latter to be proportional to the volume of yielded material. If the total width of the shear lip on the fracture surface is w, 5 is the specimen thickness and the shear lip is triangular in cross section, then... 

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