Zhang, Pu
(2016)
Bioinspired Hierarchical Materials and Cellular Structures: Design, Modeling, and 3D Printing.
Doctoral Dissertation, University of Pittsburgh.
(Unpublished)
Abstract
Bioinspired design is a useful method for developing novel materials and structures. This dissertation presents some works on designing and modeling hierarchical materials and cellular structures inspired by biological materials. The goals are to provide insight into the mechanisms underlying their remarkable mechanical performance and devise new theories to model their mechanical behaviors. The design and modeling take advantage of structural hierarchy, anisotropy, and symmetry. In addition, most of the designed materials and structures are realized by 3D printing and verified by testing.
The first key objective is to explore the energy dissipation mechanisms in bioinspired hierarchical materials. Two distinct mechanisms have been discovered regarding the wave scattering and damping figure of merit in hierarchical materials. The first mechanism is called multilevel Bragg scattering, which originates from the multiple periodicity of hierarchical materials so phononic bandgaps can be formed in a broad range of frequencies. The second mechanism is the damping enhancement in staggered composites, which arises from the large shear deformation of the viscous soft matrix. A total of three kinds of staggered composites are fabricated by 3D printing and tested to verify the theory.
The second key objective aims at modeling cellular structures with material anisotropy either inherent in the material or induced by the processing. In order to characterize the anisotropy of such cellular structures, a mathematical framework is established for their point group symmetry and symmetry breaking, which is useful for the physical property characterization and constitutive modeling. Moreover, the anisotropic inelastic deformation and failure of 3D printed cellular structures are studied by developing a hyperelastic-viscoplastic constitutive law for glassy photopolymers, which considers material anisotropy, pressure-sensitivity, and rate-dependence. Both experimental and simulation results indicate that the mechanical behavior of 3D printed cellular structures depends on both structural orientation and printing direction.
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Details
| Item Type: |
University of Pittsburgh ETD
|
| Status: |
Unpublished |
| Creators/Authors: |
|
| ETD Committee: |
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| Date: |
26 January 2016 |
| Date Type: |
Publication |
| Defense Date: |
21 October 2015 |
| Approval Date: |
26 January 2016 |
| Submission Date: |
21 October 2015 |
| Access Restriction: |
No restriction; Release the ETD for access worldwide immediately. |
| Number of Pages: |
146 |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
Swanson School of Engineering > Mechanical Engineering |
| Degree: |
PhD - Doctor of Philosophy |
| Thesis Type: |
Doctoral Dissertation |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
hierarchical material; cellular structure; 3D printing; bioinspired material; constitutive modeling; polymer; composites; phononic crystals; point group; symmetry breaking |
| Date Deposited: |
26 Jan 2016 15:47 |
| Last Modified: |
15 Nov 2016 14:30 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/26242 |
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