Image Number 2 for United States Patent #4849668.
A composite structural member includes multiple layers with one or more embedded piezoelectric elements. In a conductive member, an insulating sheath electrically isolates each piezoelectric element while mechanically coupling it to the surrounding layers, forming a unitary structure with substantially homogeneous mechanical properties. In a graphite fiber composite structure, the piezoelectric elements are fitted in recesses in one or more interior layers, and located away from strain nodes of the structural members. Preferably pairs of elements are placed on opposite sides of a node and are driven in opposing phases to induce displacement of the structure. In a preferred prototype structure Kapton film insulates the piezoelectric elements, maintaining its integrity during a high temperature, high pressure curing process. An acrylic cement secures the insulator to the elements. Systems according to the invention include vibration damping systems, and aerodynamic lift surfaces or RF reflective surfaces with high authority control. A tubular truss member with axial control characteristics is described.