The proposed modeling framework was used to obtain a fundamental understanding of the thermo-mechanical behavior of SMPs and the impact of the material behavior on hinged self-folding.
These predictions indicated how the thermal and mechanical conditions during pre-strain significantly affect the shrinking and folding response of the SMP.
This updated framework accounted for external heat sources, such as ambient temperature and incident surface heat flux, as well as internal temperature changes due to conduction and viscous heat generation.
Viscous heating during the pre-strain sequence affected the residual stresses after cooling due to accelerated viscoelastic relaxation.
Ink patterned on the surface of the SMP sheet absorbs thermal energy from the IR light, which produces localized heating.
The material shrinks wherever the activation temperature is exceeded and can produce out-of-plane deformation.
The time and temperature dependent response of these SMPs provides unique opportunities for developing complex three-dimensional (3D) structures from initially flat sheets through self-folding origami, but the application of this technique requires predicting accurately the final folded or deformed shape.
Furthermore, current computational approaches for SMPs do not fully couple the thermo-mechanical response of the material.
Hence, a proposed nonlinear, 3D, thermo-viscoelastic finite element framework was formulated to predict deformed shapes for different self-folding systems and compared to experimental results for self-folding origami structures.
A detailed understanding of the shape memory response and the effect of controllable design parameters, such as the ink pattern, pre-strain conditions, and applied thermal and mechanical fields, allows for a predictive understanding and design of functional, 3D structures.