Modelling of shape memory polymer sheets that self-fold in response to localized heating

Area of Science:

• Materials Science
• Mechanical Engineering
• Polymer Physics

Background:

• Self-folding polymers offer potential for novel actuation and deployable structures.
• Understanding the thermo-mechanical behavior of pre-strained polymers is crucial for controlled shape transformation.
• Origami-inspired designs leverage material properties for complex 3D structure formation.

Purpose of the Study:

• To develop and validate a nonlinear finite element analysis (FEA) model for thermo-mechanical shrinking and self-folding of pre-strained polystyrene.
• To investigate the influence of localized heating on polymer sheet deformation and folding dynamics.
• To provide fundamental insights into the shrinking and folding mechanisms for designing 3D origami structures.

Main Methods:

• Nonlinear finite element analysis (FEA) was employed to simulate the thermomechanical response.
• The model incorporates viscoelastic recovery of pre-strained polystyrene under localized surface heating.
• Heat generation was simulated via light absorption by patterned ink on the polymer surface.

Main Results:

• FEA predictions show shrinking and folding are sensitive to the polymer's thermo-mechanical history.
• Shrinkage distribution through the polymer thickness is nonlinear due to mass accumulation at hinges.
• Maximum shrinkage was observed below the patterned surface, not at the heated interface.

Conclusions:

• The study provides a fundamental understanding of shrinking and self-folding dynamics in pre-strained polymers.
• The FEA model accurately captures the complex thermo-mechanical behavior leading to origami-like folding.
• Findings offer design guidelines for creating 3D shapes and structures from 2D polymer sheets.