Doctoral Dissertations

Weiqun Xu

Abstract

"The dissertation, consisting of four papers, presents the results of the research investigation on environmental effects on polymers and polymer matrix composites. Hygrothermal models were developed that would allow characterization of non-Fickian diffusion coefficients from moisture weight gain data. Hygrothermal testing was also conducted to provide the necessary data for characterizing of model coefficients and model verification. In part 1, a methodology is proposed that would allow characterization of non-Fickian diffusion coefficients from moisture weight gain data for a polymer adhesive below its Tg. Subsequently, these diffusion coefficients are used for predicting moisture concentration profiles through the thickness of a polymer. In part 2, a modeling methodology based on irreversible thermodynamics applied within the framework of composite macro-mechanics is presented, that would allow characterization of non-Fickian diffusion coefficients from moisture weight gain data for laminated composites with distributed uniaxial damage. Comparisons with test data for a 5-hamess satin textile composite with uniaxial micro-cracks are provided for model verifications. In part 3, the same modeling methodology based on irreversible thermodynamics is extended to the case of a bi-axially damaged laminate. The model allows characterization of non-Fickian diffusion coefficients as well as moisture saturation level from moisture weight gain data for laminates with pre-existing damage. Comparisons with test data for a bi-axially damaged Graphite/Epoxy woven composite are provided for model verifications. Finally, in part 4, hygrothermal tests conducted on AS4/PR500 5HS textile composite laminates are summarized. The objectives of the hygrothermal tests are to determine the diffusivity and maximum moisture content of the laminate"--Abstract, page iv.

Advisor(s)

Roy, Samit

Committee Member(s)

Dharani, Lokeswarappa R.
Chandrashekhara, K.
MacSithigh, G. P.
Nanni, Antonio

Department(s)

Mechanical and Aerospace Engineering

Degree Name

Ph. D. in Engineering Mechanics

Comments

This research has been supported by NASA John Glenn Research Center, Oak Ridge National Laboratories, University of Texas-Austin, and Pratt & Whitney.

Publisher

University of Missouri--Rolla

Publication Date

Fall 2000

Journal article titles appearing in thesis/dissertation

  • Anomalous Moisture Diffusion in Viscoelastic Polymers: Modeling and Testing
  • Modeling of Diffusion in the Presence of Damage in Polymer Matrix Composites
  • Modeling of Diffusion in the Presence of Bi-Axial Damage in Polymer Matrix Composite Laminates
  • Experimental Characterization of Hygrothermal Effects in a Textile Composite

Pagination

xi, 115 pages

Note about bibliography

Includes bibliographical references.

Rights

© 2000 Weiqun Xu, All rights reserved.

Document Type

Dissertation - Restricted Access

File Type

text

Language

English

Thesis Number

T 7788

Print OCLC #

48101692

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