A constitutive model for predicting the effects of the manufacturing process on the mechanical properties of engineering polymers will be developed. The constitutive model, which has no adjustable constants, will predict (I) the non-Newtonian flow of polymer fluids; (2) the solidification process during cooling from the fluid into the glass; and (3) the three-dimensional stress-strain behavior, including ductile failure of the glassy solid. The only material properties required by the model are the equilibrium pressure-volume-temperature behavior and the linear viscoelastic shear and bulk modulus. Thus, the nonlinear mechanical behavior can be rapidly estimated, effecting a considerable reduction in the time and expense required to evaluate a new material for a particular application.The model will enable the development of innovative CAD/CAM software for the more efficient design of components constructed from engineering polymers and the manufacturing process used to produce these components. The predictive capabilities of the constitutive model will be investigated for polycarbonate to assess its suitability for engineering thermoplastics. The researchers will experimentally measure the effects of controlled thermal/deformation histories during formation of the polymer glass on the nonlinear stress-strain behavior of the solid. The experimental stress-strain behavior will be compared to predictions of the constitutive model.Commercial Applications:The research proposed could lead to the development of a new class of CAD/CAM software for engineering polymers.
