Oriented polymer glasses exhibit several phenomena during deformation: they are non-linear viscoelastic, they show a yield peak and a subsequent yield drop, and they exhibit strain-stiffening which depends strongly on the processing conditions.
In order to capture all of these phenomena we have worked on combining the Oxford glass-rubber model for polymers near the glass transition with the Rolie-Poly rheological model. Although there are still some areas to be addressed at the transition between the conformational behaviour of the molecules and the local glassy interactions, the model captures all of the features described above. The combined model is able to predict the optical birefringence and the constitutive response of oriented polymers. In combination with Kramer's crazing theory, it is also able to predict the craze initiation stress along the orientation direction resulting from process-induced orientation.
The stress-strain behaviour of bars of polymer pre-deformed by the same amount, but at different temperatures, as calculated by the constitutive model
Carry on to Crazing introduction, or go back to Glassy Polymers.
Relevant publications in the area of polymer mechanics.
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