Characterization of Creases in Polymers for Adaptive Origami Structures

Techniques employed in origami are of interest for the design of actuating structures with multiple defined geometric states. Most research in this area has focused on manipulating material chemistry or geometry to achieve folding, but crease development through full material thickness has not been studied in detail. Understanding creasing is crucial for establishing material selection guidelines in origami engineering applications. Identification of the precise failure mechanisms is critical for understanding the residual fold angle and selecting optimal materials for specific origami applications. To characterize crease formation and development, polymer films were folded using a modified parallel plate bending technique which was successfully modeled with Euler beam theory in the elastic regime. Fold angles measured after creasing provided a means to quantitatively describe a material’s ability to retain a fold, and degree of plastic deformation incurred during folding. SEM micrographs of creased regions revealed tensile deformations on exterior crease surfaces while compressive deformations such as wrinkling occurred inside. Profilometry was performed on crease interiors to identify and measure wrinkle topology. It was found that increased dissipative plastic deformation led to retention of smaller fold angles. These characterization techniques can be used as a means of classifying and organizing polymers by potential usefulness in structural origami applications.