Wednesday, 13 October 2004 - 9:40 AM

This presentation is part of : Rajagopal Symposium

Application of multiple natural configurations to the modeling of crystallization in polymers

I Joga Rao, New Jersey Institute of Technology, New Jersey Institute of Technology, Deptartment of Mechanical Engineering, University Heights, Newark, NJ 07102

We present a thermodynamic framework within the context of continuum mechanics to predict the behavior of crystallizing polymers. The constitutive models that are developed within this thermodynamic setting are able to describe the main features of the crystallization process. The model is capable of capturing the transition from a fluid like behavior to a solid like behavior in a rational manner without appealing to any adhoc transition criterion. The anisotropy of the crystalline phase is built into the model and the specific anisotropy of the crystalline phase depends on the deformation in the melt. These features are incorporated into the multiple natural configuration framework that associates different natural configurations and material symmetries with distinct microstructural features within the body that arise during the process under consideration. Specific models are generated by choosing particular forms for the internal energy, entropy and the rate of dissipation. Equations governing the evolution of the natural configurations and the rate of crystallization are obtained by maximizing the rate of dissipation, subject to appropriate constraints. The initiation criterion, marking the onset of crystallization, arises naturally in this setting in terms of the thermodynamic functions. The model generated within such a framework is used to simulate a variety of problems in which crystallization plays an important role. The predictions of the theory that has been proposed are consistent with the experimental results.

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