| Abstract: | Shape memory polymers are novel materials that can be easily formed into complex shapes, retaining memory of their original
shape even after undergoing large deformations. The temporary shape is stable and return to the original shape is triggered
by a suitable mechanism such as heating. In this paper, we develop constitutive equations to model the mechanical behavior
of crystallizable shape memory polymers. Crystallizable shape memory polymers are called crystallizable because the temporary
shape is fixed by a crystalline phase, while return to the original shape is due to the melting of this crystalline phase.
The modeling is done using a framework that was developed recently for studying crystallization in polymers (28], 25], 27],
31]) and is based on the theory of multiple natural configurations. In this paper we formulate constitutive equations for
the original amorphous phase and the semi-crystalline phase that is formed after the onset of crystallization. In addition
we model the melting of the crystalline phase to capture the return of the polymer to its original shape. The model has been
used to simulate a typical uni-axial cycle of deformation, the results of this simulation compare very well with experimental
data. In addition to this we also simulate circular shear of a hollow cylinder and present results for different cases in
this geometry. |
