Damage mechanics unified constitutive modeling for polymers

Adequacy of a material model that is based on isothermal properties becomes questionable for non-isothermal cases such as polymer processing which includes continuous change in temperature and rate. For true prediction of thermomechanical response of amorphous polymers under non-isothermal conditions, it is necessary to formulate temperature-dependent material properties and flow rules to provide a smooth transition around glass transition temperature. An improved version of dual-mechanism viscoplastic constitutive model is presented that is used to describe thermomechanical response of amorphous polymers below and above glass transition temperature. Material property definitions, evolution of internal state variables, and plastic flow rules were revisited to provide a smooth and continuous transition in material response around glass transition temperature, eg. The elastic-viscoplastic constitutive model is developed based on a thermodynamics framework. For damage evolution in complex thermomechanical problems such as polymer processing, irreversible entropy production rate is used as a damage metric [a.k.a Basaran Damage Evolution Model].