Experimental, numerical and analytical studies of smart composite materials and their applications

The thesis discusses the experimental, numerical and analytical aspects pertaining to active and passive smart composite materials. Several applications of these smart materials are illustrated.

The experimental part of the research is guided by the objective to design and develop a long-term structural health monitoring system for civil engineering based infrastructure. This is primarily accomplished by the successful design, manufacturing and processing of smart glass fiber reinforced polymer (GFRP) composite tendons with embedded Fabry-Perot fiber optic sensors. The smart tendons are fabricated using pultrusion. Previous research has assessed the behavior of these smart composites in both laboratory and other ambient conditions using different tests (quasi-static, fatigue, short- and long-term creep). This thesis continues that work by examining the performance of the tendons in reinforced concrete beams. For this purpose, a number of concrete beams with embedded smart GFRP tendons are designed, analyzed and fabricated in laboratory conditions. The novel use of smart GFRP/steel reinforcements (referred to as 'hybrid' reinforcements) in concrete structures is examined. A comprehensive testing program is followed for the beams, including thermal exposure during and after concrete curing phases, static and cyclic failure-induced loadings, and long-term creep loadings. The strain rate and deformation of the beams during loading are monitored by the embedded sensors as well as by conventional monitoring devices. The results show that the smart GFRP rebars are capable of fulfilling a dual role---reinforcing elements by virtue of their mechanical properties and long-term structural strain monitoring devices by virtue of the embedded Fabry-Perot fiber optic sensors.

To compliment this work, nonlinear finite element (FE) models pertaining to the smart concrete beams are developed. The FE models are shown to be effective in predicting various parameters of interest such as failure modes, crack patterns, failure loads, strains and stresses. The strain and deformation values computed by the FE models agree well with the readings of the embedded Fabry-Perot fiber optic sensors.

For the analytical part of the thesis, closed-form solutions, based on a modified asymptotic homogenization composite shell model, are obtained for the static three-dimensional deformations of piezoelectric composite shells with a periodic structure. The model makes it possible to determine both the local fields and the effective properties of piezoelectric shell structures by means of solutions of the derived three-dimensional local 'unit-cell' problems. (Abstract shortened by UMI.)