Report No.

SSRP06/15

June 2006

STRUCTURAL SYSTEMS

RESEARCH PROJECT

HYGROTHERMAL EFFECTS ON DURABILITY AND MOISTURE KINETICS OF FIBER-REINFORCED POLYMER COMPOSITES

by

PADMAVATHI SURATHI

VISTASP M. KARBHARI

Interim Report Submitted to the California Department of Transportation Under Contract No. 59A0309.

Department of Structural Engineering University of California, San Diego La Jolla, California 92093-0085

University of California, San Diego

Department of Structural Engineering

Structural Systems Research Project

Report No. SSRP06/15

Hygrothermal Effects on Durability and moisture Kinetics of Fiber-Reinforced Polymer Composites

by

Padmavathi Surathi

Graduate Student Researcher

Vistasp M. Karbhari

Professor of Structural Engineering

Interim Report Submitted to the California Department of Transportation

Under Contract No. 59A0309

Department of Structural Engineering

University of California, San Diego

La Jolla, California 92093-0085

June 2006

Technical Report Documentation Page 1. Report No.

FHWA/CA/ES-07/01 2. Government Accession No. 3. Recipients Catalog No.

4. Title and Subtitle

Hygrothermal Effects on Durability and Moisture Kinetics of Fiber-Reinforced Polymer Composites

5. Report Date

June 2006

6. Performing Organization Code

7. Author(s)

Padmavathi Surathi and Vistasp M. Karbhari 8. Performing Organization Report No.

UCSD / SSRP-06/15

9. Performing Organization Name and Address

Department of Structural Engineering School of Engineering University of California, San Diego La Jolla, California 92093-0085

10. Work Unit No. (TRAIS)

11. Contract or Grant No.

59A0309

12. Sponsoring Agency Name and Address

California Department of Transportation Division of Engineering Services 1801 30th St., West Building MS-9-2/5I Sacramento, California 95807

13. Type of Report and Period Covered

Interim Report

14. Sponsoring Agency Code

15. Supplementary Notes

Prepared in cooperation with the State of California Department of Transportation. This report is one of a series of reports

16. Abstract Fiber-Reinforced Polymer (FRP) composites offer many advantages over conventional materials for

applications in the marine and civil infrastructure areas. Their increasing widespread use emphasizes the need to predict their performance over long periods of time after being subjected to exposure to different environmental conditions. The kinetics of fluid sorption E-glass/vinylester composites is studied widely using the Fickian and Langmuir diffusion models. The time and temperature dependence of the rate of diffusion and maximum moisture content are analyzed and moisture kinetics data is assessed is assessed for use in performance predictions.

It is seen that various processes of degradation, both reversible and irreversible, are induced in the composite materials on exposure to moisture. The durability characteristics of unidirectional E-glass-Vinylester composites under the influence of relative humidity and immersion in water at different temperatures are investigated. The correlation between tensile and flexural strength data is investigated using statistical models. This research attempts to analyze the behavior of FRP composites exposed to the aforementioned environments and theoretically model their effects on the mechanical properties (tensile strength, tensile modulus, flexural strength and short beam shear strength) of the FRP composites, for purposes of long-term prediction. This study attempts to develop an initial correlation between effects due to immersion in deionized water with those due to exposure to humidity to further develop techniques for prediction of durability of these materials under field conditions.

17. Key Words

Durability; E-Glass; Moisture; Temperature; Humidity; Mechanical Properties; Deterioration

18. Distribution Statement

No restrictions. This document is available to the public through the National Technical Information Service, Springfield, Virginia 22161

19. Security Classification (of this report)

Unclassified

20. Security Classification (of this page)

Unclassified

21. No. of Pages

291 22. Price

Form DOT F 1700.7 (8-72) Reproduction of completed page authorized

Disclaimer

The contents of this report reflect the views of the authors who are responsible for

the facts and the accuracy of the data presented herein. The contents do not

necessarily reflect the official views or policies of the State of California or the

Federal Highway Administration. This report does not constitute a standard,

specification, or regulation.

The United States Government does not endorse products or manufacturers.

Trade and manufacturers names appear in this report only because they are

considered essential to the object of the document.

Table of Contents

Table of Contents.......................................................................................................... ii

List of Figures............................................................................................................ viii

List of Tables .............................................................................................................. xv

Abstract.................................................................................................................... xxiii

Chapter 1 Introduction........................................................................................... 1

1.1 Background................................................................................................... 1

1.2 Objectives of the Research............................................................................ 3

1.3 Overview of the Thesis ................................................................................. 3

1.4 References..................................................................................................... 6

Chapter 2 Literature Review ................................................................................. 8

2.1 Moisture Absorption in Polymeric Composites............................................ 8

2.1.1 Classical Fickian Diffusion............................................................................ 9

2.1.2 Non- Fickian Diffusion ................................................................................ 10

2.1.3 Factors Affecting the Diffusion Coefficient ................................................ 13

2.1.4 Factors Affecting Equilibrium Moisture Content ........................................ 14

2.2 Hygrothermal Ageing of Composites ......................................................... 14

2.2.1 Hygrothermal Effects on Polymer Matrices ................................................ 15

2.2.2 Hygrothermal Effects on Fibers................................................................... 18

2.2.3 Hygrothermal Effects on the Interfacial Region.......................................... 19

2.2.4 Effect of Humidity on Composites .............................................................. 21

2.2.5 Summary of Previous Research ................................................................... 23

2.3 Performance Prediction Models.................................................................. 28

2.3.1 Arrhenius Prediction Model......................................................................... 28

2.3.2 Phani and Bose Prediction Model................................................................ 29

2.3.3 Time and Temperature Superposition Model .............................................. 30

2.3.4 Pritchard and Speake Prediction Model....................................................... 32

2.3.5 Phillips Prediction Model ............................................................................ 33

2.4 References................................................................................................... 35

Chapter 3 Materials and Test Procedures ................................................................... 41

3.1 Material Constituents .................................................................................. 41

3.1.1. Glass Fiber Properties .................................................................................. 41

3.1.2 Vinylester Matrix Properties........................................................................ 41

3.1.3 Fabrication Method...................................................................................... 42

3.2 Environmental Conditions .......................................................................... 42

3.3 Test Procedures........................................................................................... 44

3.3.1 Moisture Sorption ........................................................................................ 44

3.3.2 Tensile Characterization .............................................................................. 45

3.3.3 Flexure Characterization.............................................................................. 45

3.3.4 Short Beam Shear Characterization ............................................................. 46

3.3.5 Dynamic Mechanical Thermal Analysis...................................................... 47

3.