The Mechanical Behavior of Poly(Methyl Methacrylate) Under Pressure
CASE WESTERN RESERVE UNIV CLEVELAND OH DEPT OF MACROMOLECULAR SCIENCE
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Tensile deformation of PMMA, extruded under hydrostatic pressure up to 4 kb has shown that the pressure-transmitting fluid silicon oil strongly affects the mechanical properties of this polymer. Unsealed specimens fractured in a brittle manner at almost the same strain of 5 in the whole pressure range examined, while specimens sealed with Teflon tape and rubber showed a brittle to ductile transition at only 0.25 kb. At this pressure, the craze initiation and shear band initiation stresses were found to become equal. The pressure dependency of the shear band initiation stress could be expressed well with a non-linear pressure dependent Von Mises criterion and the onset of the shear banding was proved to relate to the enthalpy energy density stored in the specimen. The combination of the non-linear pressure dependent Von Mises criterion and the enthalpy energy density conept enable us to predict the pressure dependency of Youngs modulus. Author, modified-PL.
- Solid State Physics