Thermomechanical Modeling of Microstructure Evolution Caused by Strain-Induced Crystallization

Area of Science:

• Polymer Science
• Materials Science
• Continuum Mechanics

Background:

• Strain-induced crystallization significantly affects polymer mechanical and thermal properties.
• Understanding this phenomenon is crucial for polymer manufacturing and product application.
• Existing models may not fully capture the coupled thermomechanical effects.

Purpose of the Study:

• To develop a comprehensive thermomechanical model for strain-induced crystallization in unfilled polymers.
• To simulate the coupled evolution of microstructure and temperature during deformation.
• To provide a basis for numerical implementation in finite element analysis (FEA).

Main Methods:

• Utilized a triple decomposition of the deformation gradient.
• Employed a thermodynamic framework based on the Coleman-Noll procedure and minimum dissipation potential principle.
• Defined appropriate Helmholtz free energy and dissipation potential functions.
• Formulated evolution equations for crystalline regions and temperature changes.

Main Results:

• The model successfully simulates the formation and degradation of crystalline regions during cyclic tensile tests.
• Coupled temperature changes accompanying crystallization/degradation are captured.
• Numerical examples demonstrate microstructure evolution and temperature distribution.

Conclusions:

• The proposed thermomechanical model accurately captures strain-induced crystallization in polymers.
• The model provides valuable insights into the interplay between mechanical deformation, crystallization, and temperature.
• The developed framework is suitable for finite element analysis (FEA) of polymer behavior.