US 4,849,668 A · Embedded piezoelectric structure and control

Abstract

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.

Claims11

Dependent claims

A structure formed of plies of conductive composite material which is assembled and then hardened by curing at elevated temperature or pressure, such structure comprising an assembly of

plural plies of conductive composite structural material arranged to form a body of said structure, at least one ply including a coupling face,
a piezoelectric element incorporated within said body and having an electrically actuable surface bounded by said coupling face, and
a film formed of electrically insulative sheet material located between the electrically actuable surface of said element and the coupling face for electrically insulating the surface from the conductive composite, said film being cemented to said electrically actuable surface with a cement which hardens during the curing of said plies of composite structural material to provide a mechanical shear coupling for the transmission of shear forces between the piezoelectric element and the coupling face, whereby said cured assembly forms a conductive structure of substantially homogeneous mechanical properties with a piezoelectric element effectively coupled to apply strain to the coupling face without shorting.

Dependencies are inferred from the claim text.

Embedded piezoelectric structure and control

Life of this patent

Embedded piezoelectric structure and control

Life of this patent

Abstract

Claims11