A comprehensive coupled theory for smart composite structures including delaminations

A general framework is developed for the analysis of smart composite structures with delamination and embedded/surface bonded sensors/actuators. To maintain local accuracy of stress distributions, the trial displacement field is modeled using the superposition of overall first order shear deformation and layerwise functions, accommodating zigzag in-plane warping and interlaminar shear stress continuity. The temperature and electrical fields are modeled using higher order descriptions, which can satisfy surface flux boundary conditions at structural surfaces and equilpotential conditions at electrode surfaces. A variational principle, addressing the two-way interaction between thermal, piezoelectric and mechanical fields, is used to derive the equations of motion. A Linear Quadratic Gaussian control system of composite laminates with surface bonded/segmented piezoelectric actuators is designed to improve the damping characteristics.; The presence of multiple discrete delaminations in composite plate of arbitrary thickness is modeled using Heaviside unit step functions, which are introduced in the layerwise zigzag displacement field. This allows modeling of the separation and slipping effects at the delaminated interface by introducing independent displacement field above and below the delamination. The accuracy of developed theory is validated by comparison with published experimental results as well as results obtained using laser scanning vibrometer.; Next, linear and nonlinear transient implicit algorithms are developed to study the transient response of laminated composite plates with embedded discrete and continuous sensors in the presence of multiple discrete delaminations. The presence of delamination causes changes in tip displacement and sensor voltage output (magnitude and phase). Embedded sensors provide good information about the presence of delamination. Both multiple discrete and continuous sensors provide comparable information regarding existence of delamination.; The contact problem at delaminated interfacial surfaces is modeled in terms of fictitious linear springs to provide an accurate description of the delaminated upper and lower laminates during plate vibration. Geometric nonlinearity due to large deformation and the coupled effect of the large deformation and bimodular behavior of the contact impact of the delaminated interfaces during breathing phenomena are modeled. A potential application of the developed procedure is in structural health monitoring where accurate predictions of dynamic response in the presence of delamination are important issues.