Session: SYMP 2-4: Structure and Performance of Shape Memory Polymer Actuators

Paper Number: 140187

140187 - Multi-Dimensional and Multi-Scale Shape Configurations Using Chiral Kerf Structures 

In this study, we explore the interplay of material behaviors and microstructural topologies of 3D-printed planar chiral kerf structures to enable multi-dimensional and multi-scale shape configurations. Chiral kerf structures are formed based on arrangements of chiral and coiled unit cells and are capable of in-plane and out-of-plane shape configurations under mechanical and thermal stimulations. By defining the kerf pattern, coil density of each unit cell, unit cell size, spatial cell distribution and materials, the local properties of the structure can be controlled to achieve the desired shape reconfigurations by mechanical and thermal stimulation. We study two chiral kerf patterns, namely square Archimedean and hexagon, with several coil densities to control the local flexibility of the structures. These patterns are relatively easy to arrange to form large-scale structures that can be molded into desired freeform shapes. Due to its repeatable and asymmetric patterns, kerf cells and structures are often considered as chiral and fractal-like structures. The number of coiling can be referred to as fractal order. We consider three materials, i.e., brittle Polylactic Acid (PLA), soft thermoplastic polyurethane (TPU), and a composite of alternating PLA and TPU referred to as programmable material. Because PLA owns shape memory properties, once thermally activated it presents the capability for shape change and retention (actuating component) while TPU restrains its deformation (restraining component). Controlling the PLA and TPU compositions can also alter the physical properties and responses of the programmable material, hence tuning the response characteristics of chiral kerf structures. 

We examine the influence of geometrical characteristics and nonlinear and inelastic material responses in altering shape configurations in chiral kerf structures. In all cells, the kerf patterns are formed by arrangements of straight prismatic bars with rectangular cross-sections. The slenderness ratios of the prismatic bars, measured by the ratio of the length to the cross-section dimensions of the bar and the second moments of areas of the rectangular cross-section can guide the local cell deformations, i.e., in-plane and out-of-plane deformations. Within a linear elastic material response, the shape reconfigurations are mainly controlled by the geometrical shapes and sizes of the kerf cells. When the materials exhibit nonlinear and inelastic responses, new shape reconfigurations can take place. We demonstrate attaining shape reconfigurations by mechanical and thermal stimulations. Through combinations of materials, geometries, and external stimulations, we can control local and global shape reconfigurations in planar chiral kerf structures. The goal of achieving multi-dimensional and multi-scale shape configurations is to create freeform shapes that are reconfigurable with energy management capability.

Presenting Author: Anastasia Muliana Texas A&M University

Presenting Author Biography: Anastasia Muliana is a professor of Mechanical Engineering at Texas A&M University.

Authors:

Aryabhat Darnal
Kamal Poluri
Osazuwa Okundaye-Santos
Jeeeun Kim
Negar Kalantar
Anastasia Muliana