Date of Award

Fall 2016

Project Type

Thesis

Program or Major

Mechanical Engineering

Degree Name

Master of Science

First Advisor

Yaning Li

Second Advisor

Yannis P Korkolis

Third Advisor

Igor Tsukrov

Abstract

A unique deformation mechanism of auxetic chiral structure was investigated via integrated analytical, experimental and numerical approaches. This unique deformation mechanism is the auxetic effect due to internal rotation. In this thesis, first, a rigid-rod-rotational-spring model was developed to capture the quantitative relation between the Poisson’s ratio and internal rotation of the cells in the auxetic chiral structure. It was concluded that the auxetic effects will be amplified with elevated internal rotation. Then, based on this concept, two new auxetic chiral structures were designed: (1) auxetic chiral structure with soft hinges at the corners, and (2) auxetic chiral structure with hard cores in the center. The original and the two new chiral structures were fabricated via a multi-material 3D printer (Objet Connex260). Mechanical experiments under uni-axial compression were performed to prove the concept. It was proved that both new structures can effectively amplify the auxetic effects through increased internal rotation. In addition, to further explore the mechanical behaviour of the two new designs, thorough parametric study was performed via Finite Element (FE) simulations. Design guidelines for the auxetic chiral structure was provided.

The new designs of auxetic chiral structures enable tailorable negative Poisson’s ratio under large deformation. These new cellular structures have broad potential applications in designing industrial energy absorption foams, impact and tearing resistant materials, drug-delivery medical bandages, biomedical scaffolds, responsive/smart façade of architectures, and metamaterials for optical, electro-magnetic devices and components.

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