Nonlinear Field-Coupling Responses of Adaptive Functionally Graded Structures

Texas A&M Engineering Experiment Station, College Station TX

Investigators

Abstract

Adaptive structures made of composite materials that can respond and adapt to various external stimuli are appealing for the development of multi-tasking intelligent systems. This study focuses on characterizing nonlinear properties and understanding performance of adaptive structures subjected to elevated temperatures, mechanical loading, and high electric field. The adaptive composite structures to be studied consist of ferroelectric ceramic and metal constituents whose compositions and micro-structural arrangements vary continuously through the thickness - such systems are known as functionally graded materials or FGMs. The nonlinearity is due to thermo-electro-mechanical coupling effects. For example, ferroelectric ceramics can experience polarization switching under high compressive stresses and hysteresis electric fields. The objectives of this investigation are to manufacture adaptive functionally graded composites using a powder metallurgy method; test the composite samples at different thermo-electro-mechanical histories, including quasi-static, creep-relaxation, and hysteresis loading; and establish an analytical and computational framework for predicting nonlinear response and simulating shape changes in adaptive structures in response to various external stimuli. An investigation of the thermo-electro-mechanical coupling effects will open an opportunity to further explore long-term material degradation due to oxidation and aging, and fatigue failure mechanisms in intelligent structures. These research activities will contribute to a graduate course development in multifunctional materials and structures, creating visualization and animation of shape changes in adaptive structures, and involving undergraduate and graduate students as well as high school teachers in scientific research. The analysis tools and characterization methods can benefit many industries that manufacture and use devices made from adaptive composite materials, by reducing cost and effort in material characterization requirements.