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EFFECTS OF THE THERMO EFFECTS OF THE THERMOEFFECTS OF THE THERMO EFFECTS OF THE THERMOEFFECTS OF THE THERMO EFFECTS OF THE THERMO EFFECTS OF THE THERMO EFFECTS OF THE THERMO EFFECTS OF THE THERMO -MECHANICAL HISTORY ON MECHANICAL HISTORY ON MECHANICAL HISTORY ON MECHANICAL HISTORY ON MECHANICAL HISTORY ON MECHANICAL HISTORY ON MECHANICAL HISTORY ON MECHANICAL HISTORY ON MECHANICAL HISTORY ON MECHANICAL HISTORY ON THE LINEAR SHEAR VISCOELASTIC PROPERTIES OF THE LINEAR SHEAR VISCOELASTIC PROPERTIES OF THE LINEAR SHEAR VISCOELASTIC PROPERTIES OF THE LINEAR SHEAR VISCOELASTIC PROPERTIES OF THE LINEAR SHEAR VISCOELASTIC PROPERTIES OF THE LINEAR SHEAR VISCOELASTIC PROPERTIES OF THE LINEAR SHEAR VISCOELASTIC PROPERTIES OF THE LINEAR SHEAR VISCOELASTIC PROPERTIES OF THE LINEAR SHEAR VISCOELASTIC PROPERTIES OF THE LINEAR SHEAR VISCOELASTIC PROPERTIES OF THE LINEAR SHEAR VISCOELASTIC PROPERTIES OF THE LINEAR SHEAR VISCOELASTIC PROPERTIES OF THE LINEAR SHEAR VISCOELASTIC PROPERTIES OF THE LINEAR SHEAR VISCOELASTIC PROPERTIES OF THE LINEAR SHEAR VISCOELASTIC PROPERTIES OF THE LINEAR SHEAR VISCOELASTIC PROPERTIES OF UNCROSSLINKED ELASTOMERS UNCROSSLINKED ELASTOMERS UNCROSSLINKED ELASTOMERS UNCROSSLINKED ELASTOMERSUNCROSSLINKED ELASTOMERS UNCROSSLINKED ELASTOMERS UNCROSSLINKED ELASTOMERS UNCROSSLINKED ELASTOMERSUNCROSSLINKED ELASTOMERS UNCROSSLINKED ELASTOMERS
by
Daesun Hong Daesun HongDaesun Hong Daesun Hong
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A Dissertation Presented to theA Dissertation Presented to the A Dissertation Presented to the A Dissertation Presented to the A Dissertation Presented to theA Dissertation Presented to theA Dissertation Presented to the A Dissertation Presented to the A Dissertation Presented to the
FACULTY OF THEFACULTY OF THE FACULTY OF THEFACULTY OF THEFACULTY OF THEFACULTY OF THE FACULTY OF THEFACULTY OF THEFACULTY OF THE FACULTY OF THE GRADUATE SCHOOL GRADUATE SCHOOL GRADUATE SCHOOL GRADUATE SCHOOL GRADUATE SCHOOLGRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA UNIVERSITY OF SOUTHERN CALIFORNIAUNIVERSITY OF SOUTHERN CALIFORNIA UNIVERSITY OF SOUTHERN CALIFORNIAUNIVERSITY OF SOUTHERN CALIFORNIAUNIVERSITY OF SOUTHERN CALIFORNIAUNIVERSITY OF SOUTHERN CALIFORNIA UNIVERSITY OF SOUTHERN CALIFORNIAUNIVERSITY OF SOUTHERN CALIFORNIA UNIVERSITY OF SOUTHERN CALIFORNIA UNIVERSITY OF SOUTHERN CALIFORNIA UNIVERSITY OF SOUTHERN CALIFORNIA UNIVERSITY OF SOUTHERN CALIFORNIA UNIVERSITY OF SOUTHERN CALIFORNIAUNIVERSITY OF SOUTHERN CALIFORNIA UNIVERSITY OF SOUTHERN CALIFORNIAUNIVERSITY OF SOUTHERN CALIFORNIA UNIVERSITY OF SOUTHERN CALIFORNIAUNIVERSITY OF SOUTHERN CALIFORNIA
In Partial In Partial In Partial In Partial In Partial FulfillmentFulfillment Fulfillment of the
RequirementRequirementRequirement Requirement s for the Degree the Degreethe Degreethe Degreethe Degreethe Degree
DOCTOR OF PHILOSOPHY DOCTOR OF PHILOSOPHYDOCTOR OF PHILOSOPHYDOCTOR OF PHILOSOPHY DOCTOR OF PHILOSOPHY DOCTOR OF PHILOSOPHYDOCTOR OF PHILOSOPHY DOCTOR OF PHILOSOPHY DOCTOR OF PHILOSOPHYDOCTOR OF PHILOSOPHYDOCTOR OF PHILOSOPHY
(CHEMICAL ENGINEERING) (CHEMICAL ENGINEERING)(CHEMICAL ENGINEERING)(CHEMICAL ENGINEERING)(CHEMICAL ENGINEERING)(CHEMICAL ENGINEERING)(CHEMICAL ENGINEERING) (CHEMICAL ENGINEERING)(CHEMICAL ENGINEERING)(CHEMICAL ENGINEERING) (CHEMICAL ENGINEERING)(CHEMICAL ENGINEERING)(CHEMICAL ENGINEERING)(CHEMICAL ENGINEERING) (CHEMICAL ENGINEERING)
December 2013
Copyright 20Copyright 20 Copyright 20Copyright 20 Copyright 20Copyright 20 13 Daesun Hong Daesun HongDaesun Hong
Object Description
| Title | Effects of the thermo-mechanical history on the linear shear viscoelastic properties of uncrosslinked elastomers |
| Author | Hong, Daesun |
| Author email | daehong@usc.edu;daesunhong@gmail.com |
| Degree | Doctor of Philosophy |
| Document type | Dissertation |
| Degree program | Chemical Engineering |
| School | Viterbi School of Engineering |
| Date defended/completed | 2013-10-17 |
| Date submitted | 2013-11-25 |
| Date approved | 2013-11-26 |
| Restricted until | 2013-11-26 |
| Date published | 2013-11-26 |
| Advisor (committee chair) | Chang, Wenji Victor |
| Advisor (committee member) |
Shing, Katherine Hogen-Esch, Thieo |
| Abstract | Linear viscoelastic analysis is an essential tool for any rational design of a polymer-based structure or device. In order to carry out such an analysis, properties such as stress relaxation moduli, or creep compliance functions, or complex dynamic moduli over a wide range of time or frequency are needed. A master curve of any modulus is determined by shifting the experimental data over a wide range of temperature to that at the reference temperature based on the assumption that the material follows the time-temperature superposition principle. In practice, the construction of a master curve for a soft elastomer is somewhat arbitrary and subject to a significant degree of uncertainty. The objective of this thesis is to conduct a thorough study on the validity of the time-temperature superposition principle as applied to soft gum (or uncrosslinked) elastomers. ❧ Four materials were used in this study: SBR1 (commercial name: SBR1502), SBR2 (commercial name: PLF (PLIOFLEX) 1712C, an oil-extended SBR), Silicone rubber (commercial name: SSILCL.125, translucent white), and Silly putty (trademark, manufactured by Crayola LLC.). A Physcia MCR 301 Rheometer (by Anton Paar Co.) was used in this study. A circular disk specimen was placed between two parallel plates and was subjected to a series of stepwise increasing of compressive strains and the corresponding compressive stresses were recorded. At each step, an infinitesimal oscillatory shear deformation in Θ-direction was superimposed to the state of finite compressive strain or stress. The results showed that the shear viscoelastic properties of all the elastomers were very sensitive to the normal (compressive) force, the gap distance between two parallel-plates, the top plate types, geometry of the sample, experimental history, and storage condition, etc. ❧ Our first finding was that contrary to the common practice, reliable data could not be obtained using a specimen with the same diameter as that of the top plate. The diameter of the specimen had to be kept smaller than the top plate even at the highest compression. In order to correct the G’ as reported by the apparatus, the effect of the diameter has to be calculated, which required accurate measurements of density and mass of the specimen. Because of the uncrosslinked specimen contained some trapped air pockets, the density value could change significantly. Therefore, density was measured before and after every test. It was shown that the axial stiffness of the specimen is very sensitive to the density of the same specimen. ❧ Our first objective is to establish a protocol with which reliable and reproducible data can be obtained. It requires an application of sufficiently large compressive stress. Consistency among new specimens with different diameter and thickness, which were cut from the same sheet, was established by the agreement of their limiting damping factor values over a frequency range from 0.2 rad/s to 200 rad/s. And most of the repeated experiments of the same specimen were reproducible in damping factor values, except those had been subjected to a severe thermal-mechanical history. ❧ Effect of the gap level (distance between the two plates), which measures the extent of compression, on the superimposed shear storage modulus, after a correction to the effect of the sample diameter, was studied at a fixed frequency such as 10.4 rad/s. As the gap decreased the corrected shear storage modulus G’ value first increased, reached a maximum and then decreased rapidly. Both the peak value and its corresponding compression ratio, which is defined as final gap/initial thickness, decreased with increasing value of the initial shape factor, which is defined as Diameter/(4×Height). We postulate that the measured corrected G’ depends on the following factors: the contact condition between the specimen surface and the corresponding plate, the shear storage modulus of the material at zero (infinitesimal) strain, and the state of the internal strain in the specimen. As the internal strain increases, the corrected G’ decreases. ❧ In the earlier stage of compression, the interfacial contact increases by forcing the elastomer to conform to the surface of the measurement plate, and the main body of the specimen is subjected to very little strain. After the best contact is reached the lateral surface of the specimen is forced to bulge and the shape of the lateral surface becomes parabolic, which can be calculated based on stress analysis with a non-slippage boundary condition. However, upon further compression, the tangential stress becomes large enough such that the slippage occurs, which causes the strain state in the specimens to change completely, leading to a rapid decrease in the corrected G’. Specimens with different shape factor have different tendency to slip and hence exhibit different behavior. ❧ The effect of the type of the top plate was studied. And it was found out that there was no difference in limiting damping factor values, but corrected G’ measured by the serrated top plate was smaller than that by the flat smooth top plates. ❧ Silicone rubber has the lowest friction coefficient, which makes it most likely to slip. The corrected G’ showed much less decrease after reached the maximum, similar to the behavior of SBR with a large initial shape factor. This further supports our theoretical argument that the specimen with a larger shape factor has higher tendency to slip. ❧ A very thorough and systematic research over four years on the effect of different thermo-mechanical histories on the superimposed linear viscoelastic properties was carried out. This set of data will be extremely valuable to us as well as to any future researchers to further study the dependence of the corrected G’ on the internal strain in the material. One type of the tests is the relaxation experiment. With the normal stress reduced at the constant gap, damping factor decreased slightly, whereas corrected G’ increased, supporting the hypothesis that the corrected G’ increases as the internal strain decreases. On the other hand, a rest without the application of an external load stresses caused an opposite change that G’ decreased and tan δ increased. A series of experiments on introducing large internal strain in the specimens by applying severe deformation clearly showed the significant effect of the internal strain. ❧ A protocol was developed to apply the time-temperature superposition principle for the construction of the master curves for soft elastomers. This protocol was successfully applied to SBR1, SBR2 and silly putty. The horizontally shift factors and the corresponding WLF constants were determined from the damping factors at different temperatures. As expected from the previous discussions, empirical vertical shift factors are needed in order to obtain a master curve for the corrected G’ to take into account of different internal strains in the specimen at different temperatures. While we are not able to determine the true G’ at the zero strain state yet, further theoretical analysis on the internal strain based on an proven constitutive equation, such as the CBT equation may allow us to calculate the true value. In the meantime, this well-defined and consistent approach at least allows us to obtain a reasonably reproducible value and provides a reasonable estimation of the true G’. It also provides a basis for comparing data from different researchers in different laboratories. Using this procedure we are able to compare the G’ at the ultrasonic frequency of 2.08E08 rad/s as determined by the ultrasonic impedance technique with the value calculated based on the master curve, and the agreement is within the experimental uncertainties in the two approaches. |
| Keyword | linear viscoelastic property; rheometer; thermomechanical history; soft material; elastomer; modulus; stepwise compression; gap; superposition; SBR; parallel plate; internal strain; damping factor; loss tangent; WLF; finite compression; DMA; slippage; geometry factor |
| Language | English |
| Format (imt) | application/pdf |
| 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 |
| Provenance | Electronically uploaded by the author |
| Type | texts |
| Legacy record ID | usctheses-m |
| Contributing entity | University of Southern California |
| Rights | Hong, Daesun |
| Access conditions | The author retains rights to his/her dissertation, thesis or other graduate work according to U.S. copyright law. Electronic access is being provided by the USC Libraries in agreement with the author, as the original true and official version of the work, but does not grant the reader permission to use the work if the desired use is covered by copyright. It is the author, as rights holder, who must provide use permission if such use is covered by copyright. The original signature page accompanying the original submission of the work to the USC Libraries is retained by the USC Libraries and a copy of it may be obtained by authorized requesters contacting the repository e-mail address given. |
| Repository name | University of Southern California Digital Library |
| Repository address | USC Digital Library, University of Southern California, University Park Campus MC 7002, 106 University Village, Los Angeles, California 90089-7002, USA |
| Repository email | cisadmin@usc.edu |
| Filename | etd-HongDaesun-2185.pdf |
| Archival file | uscthesesreloadpub_Volume8/etd-HongDaesun-2185.pdf |
Description
| Title | Page 1 |
| Full text | EFFECTS OF THE THERMO EFFECTS OF THE THERMOEFFECTS OF THE THERMO EFFECTS OF THE THERMOEFFECTS OF THE THERMO EFFECTS OF THE THERMO EFFECTS OF THE THERMO EFFECTS OF THE THERMO EFFECTS OF THE THERMO -MECHANICAL HISTORY ON MECHANICAL HISTORY ON MECHANICAL HISTORY ON MECHANICAL HISTORY ON MECHANICAL HISTORY ON MECHANICAL HISTORY ON MECHANICAL HISTORY ON MECHANICAL HISTORY ON MECHANICAL HISTORY ON MECHANICAL HISTORY ON THE LINEAR SHEAR VISCOELASTIC PROPERTIES OF THE LINEAR SHEAR VISCOELASTIC PROPERTIES OF THE LINEAR SHEAR VISCOELASTIC PROPERTIES OF THE LINEAR SHEAR VISCOELASTIC PROPERTIES OF THE LINEAR SHEAR VISCOELASTIC PROPERTIES OF THE LINEAR SHEAR VISCOELASTIC PROPERTIES OF THE LINEAR SHEAR VISCOELASTIC PROPERTIES OF THE LINEAR SHEAR VISCOELASTIC PROPERTIES OF THE LINEAR SHEAR VISCOELASTIC PROPERTIES OF THE LINEAR SHEAR VISCOELASTIC PROPERTIES OF THE LINEAR SHEAR VISCOELASTIC PROPERTIES OF THE LINEAR SHEAR VISCOELASTIC PROPERTIES OF THE LINEAR SHEAR VISCOELASTIC PROPERTIES OF THE LINEAR SHEAR VISCOELASTIC PROPERTIES OF THE LINEAR SHEAR VISCOELASTIC PROPERTIES OF THE LINEAR SHEAR VISCOELASTIC PROPERTIES OF UNCROSSLINKED ELASTOMERS UNCROSSLINKED ELASTOMERS UNCROSSLINKED ELASTOMERS UNCROSSLINKED ELASTOMERSUNCROSSLINKED ELASTOMERS UNCROSSLINKED ELASTOMERS UNCROSSLINKED ELASTOMERS UNCROSSLINKED ELASTOMERSUNCROSSLINKED ELASTOMERS UNCROSSLINKED ELASTOMERS by Daesun Hong Daesun HongDaesun Hong Daesun Hong ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ _______________________________________________________________________________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ _______________________________________________________________________________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ _______________________________________________________________________________________________________________________________________________ A Dissertation Presented to theA Dissertation Presented to the A Dissertation Presented to the A Dissertation Presented to the A Dissertation Presented to theA Dissertation Presented to theA Dissertation Presented to the A Dissertation Presented to the A Dissertation Presented to the FACULTY OF THEFACULTY OF THE FACULTY OF THEFACULTY OF THEFACULTY OF THEFACULTY OF THE FACULTY OF THEFACULTY OF THEFACULTY OF THE FACULTY OF THE GRADUATE SCHOOL GRADUATE SCHOOL GRADUATE SCHOOL GRADUATE SCHOOL GRADUATE SCHOOLGRADUATE SCHOOL UNIVERSITY OF SOUTHERN CALIFORNIA UNIVERSITY OF SOUTHERN CALIFORNIAUNIVERSITY OF SOUTHERN CALIFORNIA UNIVERSITY OF SOUTHERN CALIFORNIAUNIVERSITY OF SOUTHERN CALIFORNIAUNIVERSITY OF SOUTHERN CALIFORNIAUNIVERSITY OF SOUTHERN CALIFORNIA UNIVERSITY OF SOUTHERN CALIFORNIAUNIVERSITY OF SOUTHERN CALIFORNIA UNIVERSITY OF SOUTHERN CALIFORNIA UNIVERSITY OF SOUTHERN CALIFORNIA UNIVERSITY OF SOUTHERN CALIFORNIA UNIVERSITY OF SOUTHERN CALIFORNIA UNIVERSITY OF SOUTHERN CALIFORNIAUNIVERSITY OF SOUTHERN CALIFORNIA UNIVERSITY OF SOUTHERN CALIFORNIAUNIVERSITY OF SOUTHERN CALIFORNIA UNIVERSITY OF SOUTHERN CALIFORNIAUNIVERSITY OF SOUTHERN CALIFORNIA In Partial In Partial In Partial In Partial In Partial FulfillmentFulfillment Fulfillment of the RequirementRequirementRequirement Requirement s for the Degree the Degreethe Degreethe Degreethe Degreethe Degree DOCTOR OF PHILOSOPHY DOCTOR OF PHILOSOPHYDOCTOR OF PHILOSOPHYDOCTOR OF PHILOSOPHY DOCTOR OF PHILOSOPHY DOCTOR OF PHILOSOPHYDOCTOR OF PHILOSOPHY DOCTOR OF PHILOSOPHY DOCTOR OF PHILOSOPHYDOCTOR OF PHILOSOPHYDOCTOR OF PHILOSOPHY (CHEMICAL ENGINEERING) (CHEMICAL ENGINEERING)(CHEMICAL ENGINEERING)(CHEMICAL ENGINEERING)(CHEMICAL ENGINEERING)(CHEMICAL ENGINEERING)(CHEMICAL ENGINEERING) (CHEMICAL ENGINEERING)(CHEMICAL ENGINEERING)(CHEMICAL ENGINEERING) (CHEMICAL ENGINEERING)(CHEMICAL ENGINEERING)(CHEMICAL ENGINEERING)(CHEMICAL ENGINEERING) (CHEMICAL ENGINEERING) December 2013 Copyright 20Copyright 20 Copyright 20Copyright 20 Copyright 20Copyright 20 13 Daesun Hong Daesun HongDaesun Hong |
