Date of Award

8-2017

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Mechanical Engineering

Committee Member

Dr. Suyi Li, Committee Chair

Committee Member

Dr. Joshua Summers

Committee Member

Dr. Oliver Myers

Abstract

The application of origami patterns in engineering design has been the subject of much research efforts. Structures derived based on origami patterns are capable of displaying a host of innovative mechanical properties which are directly related to the kinematics of their folding. The work presented in this research takes design inspiration from a rigid foldable type of origami, namely the Miura-ori pattern. A cellular solid designed based on the Miura Ori folding pattern can exhibit three dimensional multi-stability, and different programmable characteristics like variable stiffness and elastic moduli, which stem from the inherent elastic multi-stability. The Miura Ori structure can be broken down to a basic building block termed as a unit Miura cell. This unit cell inherits its bistability from the nonlinear relationship between the external deformation and the folding of the cell. Unlike other conventional bistable mechanisms such as curved beams or asymmetric laminar composites, this unit cell possess an unorthodox characteristic; the critical, unstable equilibrium configuration lies on the same side of the two stable ones. This leads to two distinct force deformation curves within the same range and thereby leading to two distinct stiffness magnitudes at the two stable configurations. The difference in the stiffness magnitudes between the two stable configurations can be tweaked by tailoring certain key design parameters of the unit cell. The programmable properties of the bistable unit cell can be further extended to include variable effective elastic modulus since it can be directly related to the stiffness. This research focuses on the comprehensive study and design of such a bistable unit Miura cell with programmable mechanical properties. The results from the study of this cell are qualitatively validated using a 3D printed prototype. The analysis of the unit cell also paves the way for extending the study where identical unit cells are assembled to form a multi-stable Miura structure with programmable stiffness and effective elastic modulus.

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