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SYNTHESIS AND MECHANICAL EVALUATION OF MICRO-SCALE TRUSS STRUCTURES FORMED FROM SELF-PROPAGATING POLYMER WAVEGUIDES
by
Alan J. Jacobsen
A Dissertation Presented to the
FACULTY OF THE GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
DOCTOR OF PHILOSOPHY
(MECHANICAL ENGINEERING)
December 2007
Copyright 2007 Alan J. Jacobsen
Object Description
| Title | Synthesis and mechanical evaluation of micro-scale truss structures formed from self-propagating polymer waveguides |
| Author | Jacobsen, Alan J. |
| Author email | ajacobse@usc.edu |
| Degree | Doctor of Philosophy |
| Document type | Dissertation |
| Degree program | Mechanical Engineering |
| School | Viterbi School of Engineering |
| Date defended/completed | 2007-10-22 |
| Date submitted | 2007 |
| Restricted until | Restricted until 31 Oct. 2009. |
| Date published | 2009-10-31 |
| Advisor (committee chair) | Nutt, Steven |
| Advisor (committee member) |
Kassner, Michael E. Hogen-Esch, Thieo E. |
| Abstract | Materials with significant porosity, generally termed cellular materials, have considerably lower bulk density than their solid counterparts. However, at the cost of reducing the mass of a material by introducing porosity, mechanical properties such as the strength and elastic modulus are significantly diminished. Ordered cellular structures generally exhibit an increase in modulus and peak strength relative to random cellular configurations by changing the mode of deformation from bending-dominated to stretch/compression-dominated within the microstructure during elastic loading. Nevertheless, techniques to fabricate three-dimensional ordered open-cellular materials, particularly with feature sizes ranging from tens to hundred of microns, are limited. Presented in this dissertation, is a new technique to create cellular materials with a truss architecture from a three-dimensional interconnected pattern of self-propagating polymer waveguides. The self-propagating effect enables the rapid formation (< 1 min) of thick (> 5 mm) three-dimensional open-cellular micro-truss structures from a single two-dimensional exposure surface. The process also affords significant flexibility and control of the resulting truss microstructure.; The structure-property relationships in these new polymer micro-trusses have been investigated, correlating compressive and shear behavior with structural features, such as density, cell size, truss angle, and unit cell architecture. The compression and shear modulus compare well with analytical predictions; however the measured peak strength was significantly lower than predicted. The deviation of the measured peak strength from the idealized predictions was attributed to imperfections in the structure and the nonlinear behavior of the solid polymer. The affect of imperfections can be reduced by developing unit cell architectures with increased waveguide connectivity that ultimately increase nodal stability and decrease the waveguide truss member slenderness ratio. |
| Keyword | cellular materials; polymer waveguides; mechanical properties; lithography; rapid prototyping |
| Language | English |
| Part of collection | University of Southern California dissertations and theses |
| Publisher (of the original version) | University of Southern California |
| Place of publication (of the original version) | Los Angeles, California |
| Publisher (of the digital version) | University of Southern California. Libraries |
| Type | texts |
| Legacy record ID | usctheses-m896 |
| Rights | Jacobsen, Alan J. |
| Repository name | Libraries, University of Southern California |
| Repository address | Los Angeles, California |
| Repository email | http://www.usc.edu/isd/libraries/services/ask_a_librarian/email/ |
| Filename | etd-Jacobsen-20071031 |
| Archival file | uscthesesreloadpub_Volume23/etd-Jacobsen-20071031.pdf |
Description
| Title | Page 1 |
| Full text | SYNTHESIS AND MECHANICAL EVALUATION OF MICRO-SCALE TRUSS STRUCTURES FORMED FROM SELF-PROPAGATING POLYMER WAVEGUIDES by Alan J. Jacobsen A Dissertation Presented to the FACULTY OF THE GRADUATE SCHOOL UNIVERSITY OF SOUTHERN CALIFORNIA In Partial Fulfillment of the Requirements for the Degree DOCTOR OF PHILOSOPHY (MECHANICAL ENGINEERING) December 2007 Copyright 2007 Alan J. Jacobsen |
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