Content area
Abstract
This thesis discusses experimental and analytical aspects of active and passive smart composite materials.
For the experimental purposes of the work, Bragg Grating and Fabry Perot fiber optic strain sensors are embedded in glass- and carbon-fiber-reinforced polymer tendons during pultrusion. The intended application is to embed these smart tendons in civil engineering structures wherein they would act as concrete reinforcements, replacing steel and overcoming the associated corrosion problems. As well, by virtue of the embedded sensors, these tendons would provide remote for health monitoring of these structures. To verify the operation of the embedded sensors, mechanical tests were performed at room temperatures as well as at low (−40°C) and high (+80°C) temperature extremes. The reliability assessment of the fiber optic sensors further involved a detailed examination of their fatigue and creep behavior as well as the combined effect of sustained loads and aggressive chemical solutions. The purpose of these latter tests is to closely simulate conditions encountered in concrete. Other aspects of the work dealt with the use of the fiber optic sensors to monitor the pultrusion process as well as tests performed to investigate the effect of the embedded sensors on the structural integrity of the host composite material.
For the analytical aspects of this thesis, the asymptotic homogenization method was used to develop mathematical models pertaining to (active) smart composite structures with a periodic array of embedded actuators. To make the model more comprehensive, thermal and hygroscopic expansion effects were included. Asymptotic homogenization takes a boundary value problem which is characterized by rapidly oscillating coefficients, and replaces it with a simpler one containing some effective coefficients. This homogenized problem is much more amenable to analytic and numerical treatment than the original one. The effectiveness of the derived models was illustrated by means of two- and three-dimensional examples. The asymptotic homogenization methodology was used also to develop mathematical models describing the behavior of smart composite plates with rapidly varying thickness and a large number of embedded actuators. This model was applied to wafer-reinforced piezoelectric plates. These are plates reinforced with mutually perpendicular ribs or stiffeners. The stiffeners themselves, may, if desired also exhibit piezoelectric characteristics.
