Abstract
Polymeric products are mostly manufactured by warm mechanical processes, wherein large viscoplastic deformation and the thermomechanical coupling effect are highly involved. To capture such intricate behavior of the amorphous glassy polymers, this paper develops a finite-strain and thermomechanically-coupled constitutive model, which is based on a tripartite decomposition of the deformation gradient into elastic, viscoplastic, and thermal components. Constitutive equations are formulated with respect to the spatial configuration in terms of the Eulerian Hencky strain rate and the Jaumann rate of Kirchhoff stress. Hyperelasticity, the viscoplastic flow rule, strain softening and hardening, the criterion for viscoplasticity, and temperature evolution are derived within the finite-strain framework. Experimental data obtained in uniaxial tensile tests and three-point bending tests of polycarbonates are used to validate the numerical efficiency and stability of the model. Finally, the proposed model is used to simulate the gas-blow forming process of a polycarbonate sheet. Simulation results demonstrate well the capability of the model to represent large viscoplastic deformation and the thermomechanical coupling effect of amorphous glassy polymers.
Highlights
IntroductionTheir extraordinary physical (lightweight), optical (light transparency), and mechanical (toughness, impact resistance) properties allow them to be widely used in a variety of engineering applications, such as aircraft canopies, explosion shields, goggles, medical apparatuses, etc
Amorphous glassy polymers are a group of thermoplastics that do not crystallize below the glass transition temperature Tg
In order to further account for the thermomechanical coupling effect, we assumed a tripartite decomposition of the deformation into elastic, viscoplastic, and thermal components [29]
Summary
Their extraordinary physical (lightweight), optical (light transparency), and mechanical (toughness, impact resistance) properties allow them to be widely used in a variety of engineering applications, such as aircraft canopies, explosion shields, goggles, medical apparatuses, etc. [1,2] These polymeric products are mostly manufactured by warm mechanical processes such as extrusion, drawing, blow forming, and calendering, wherein glassy polymers undergo large viscoplastic deformations and exhibit the thermomechanical coupling effect [3,4]. To capture such intricate behavior accurately, developing a reliable and practical constitutive model is of prime significance for the design and manufacture of polymeric products. Over the last few decades, considerable effort has been devoted to developing constitutive models that can describe viscoelastic and large viscoplastic deformations of amorphous glassy polymers [5,6,7,8,9].
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