1 Introduction; 1.1 Adaptive Structural Systems; 1.2 Objective and Scope; 1.3 Outline and Overview; 2 Helicopter Applications; 2.1 Noise and Vibration; 2.1.1 Generation; 2.1.2 Areas of Relevance; 2.2 Main Rotor; 2.2.1 Rotational Sources; 2.2.2 Impulsive Sources; 2.2.3 Broadband Sources; 2.3 Passive Concepts; 2.3.1 External Devices; 2.3.2 Aeroelastic Conformability; 2.4 Active and Adaptive Concepts; 2.4.1 Pitch Control at the Blade Root; 2.4.2 Discrete Flap Actuation; 2.4.3 Integral Blade Actuation; 2.5 Adaptive Beam Aspects; 2.5.1 Beam Actuation Concepts; 2.5.2 Adaptive System Concepts; 2.5.3 Development Status; 3 Fundament a1 Considerations; 3.1 Mathematical Preliminaries; 3.1.1 Euclidean Vectors; 3.1.2 Tensor Representation; 3.1.3 Matrix Representation; 3.2 Deformable Structures . Mechanical Fields; 3.2.1 Loads; 3.2.2 Stresses; 3.2.3 Mechanical Equilibrium; 3.2.4 Strains; 3.2.5 Transformations; 3.3 Dielectric Domains - Electrostatic Fields; 3.3.1 Electric Charge; 3.3.2 Electric Flux Density; 3.3.3 Electrostatic Equilibrium; 3.3.4 Electric Field Strengths; 3.4 Principle of Viual Work; 3.4.1 General Principle of Virtual Work; 3.4.2 Principle of Virtual Displacements; 3.4.3 Principle of Virtual Loads; 3.4.4 Principle of Virtual Electric Potential; 3.4.5 D'Alembert's Principle in the Lagrangian Version; 3.4.6 Summation of Virtual Work Contributions; 3.5 Other Variational Principles; 3.5.1 Extended Dirichlet's Principle of Minimum Potential Energy; 3.5.2 Extended General Hamilton's Principle; 4 Piezoelectric Materials; 4.1 Piezoelectric Effect; 4.1.1 Historical Development; 4.1.2 Crystal Structures; 4.2 Constitutive Formulation; 4.2.1 Mechanical Fields; 4.2.2 Electrostatic Fields; 4.2.3 Electromechanical Coupling; 4.2.4 Spatial Rotation; 4.2.5 Analogy of Electrically and Thermally Induced Deformations; 4.3 Constitutive Examination; 4.3.1 Constitutive Relation; 4.3.2 Converse Piezoelectric Effect; 4.3.3 Direct Piezoelectric Effect;4.4 Constitutive Reduction; 4.4.1 Unidirectional Electrostatic Fields; 4.4.2 Planar Mechanical Fields; 4.4.3 Planar Rotation; 4.4.4 Negated Electric Field Strength; 4.5 Actuator and Sensor Conditions; 4.5.1 Actuator Application with Voltage and Current Source; 4.5.2 Sensor Application with Voltage and Current Measurement; 5 Piezoelectric Composites; 5.1 Classification of General Composites; 5.1.1 Topology of the Inclusion Phase; 5.1.2 Laminated Composites and Laminated Fiber Composites; 5.2 Conception of Piezoelectric Composites; 5.2.1 Interdigitated Electrodes and Piezoelectric Fibers; 5.2.2 Electroding Implications; 5.2.3 Development Status; 5.2.4 Representative Volume Element and Fiber Geometry; 5.2.5 Modeling Preliminaries; 5.3 Micro-Electromechanics with Equivalent Inclusions; 5.3.1 Mean Fields and Concentration Matrices; 5.3.2 Elementary Rules of Mixture; 5.3.3 Equivalence of Inclusion and Inhomogenity'5.3.4 Non-Dilute Concentrations; 5.4 Micro-Electromechanics with Sequential Stacking; 5.4.1 Stacking of Constituents with Uniform Fields; 5.4.2 Normal Mode Stacking Coefficients; 5.4.3 Shear Mode Stacking Coefficients; 5.4.4 Stacking Sequences; 5.4.5 Non-Homogeneous Electrostatic Fields; 5.4.6 Stacking Sequences for Non-Homogeneous Electrostatic Fields; 5.5 Validation of the Micro-Electromechanics; 5.5.1 Experiments and Finite Element Models; 5.5.2 Dielectric, Piezoelectric, and Mechanical Properties; 6 Adaptive Laminated Composite Shells; 6.1 Macro-Electromechanics; 6.1.1 Lamination Theory; 6.1.2 Laminates with Groups of Electrically Paralleled Laminae; 6.2 Kinematics and Equilibrium; 6.2.1 General Thin Shell Kinematics; 6.2.2 Cylindrical Thin Shell Kinematics; 6.2.3 Cylindrical Thin Shell Equilibrium; 6.3 Constitutive Reduction; 6.3.1 Negligence of Strain and Stress Components; 6.3.2 Potential Energy Considerations; 7 Adaptive Thin-Walled Beams; 7.1 General Beam Kinematics; 7.1.1 Positions and Displacements; 7.1.2 Rotations; 7.1.3