Date of Award

2008

Level of Access Assigned by Author

Open-Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Civil Engineering

Advisor

Roberto Lopez-Anido

Second Committee Member

William Davids

Third Committee Member

Eric Landis

Abstract

This dissertation involved several research activities with the common goal of developing a structural health monitoring methodology. The research activities encompass: composites fabrication, numerical modeling and a mechanical experimental program using a state-of-the-art sensing technology. The first part of the dissertation presents an analytical and experimental effort to characterize the bending response of sandwich composite plates. A general expression for the shear correction factor for laminated plates was derived using the principle of strain energy equivalence. It was proved that the first-order shear deformation theory (FSDT) can be confidently used in the elastic analysis of sandwich composite plates with lowdensity core using the proposed shear factor. A correlation between the experimental response of sandwich composite plates under transverse load and analytical predictions was conducted. The good agreement obtained provides an experimental validation of the developed analytical method and enhances the test method for simply supported sandwich composite plates subjected to a distributed load (ASTM D6416). The second part of the dissertation deals with structural health monitoring using embedded fiber optic strain sensors. A long-term monitoring of wood structural members of the AEWC Center new office building expansion was conducted using Extrinsic Fabry-Perot Interferometric (EFPI) fiber optic sensors embedded in a FRP laminate. A one-year cyclic variation of the longitudinal strain in the beams was observed, which is attributed to the variation of relative humidity during the year. The major research work of this dissertation presented a fatigue crack monitoring study of composite doubler plate joints using embedded fiber Bragg grating strain sensors was conducted. A methodology for the structural health monitoring and detection of delamination growth of composite joints based on strain measurements was developed. Secondary bonded woven Eglass/ vinyl ester composite doubler plate joints were subjected to fatigue tension loading. The feasibility of monitoring delamination using embedded sensors was investigated. The experimental plan, finite element modeling and the fabrication methodology of the specimens through Vacuum Assisted Resin Transfer Molding (VARTM) processing are presented. The proposed methodology allows detecting a one quarter inch delamination length, which is a common criterion used in marine construction for damage tolerance in service conditions.

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