Composites for structural control

• US 5,869,189 A
• Filed: 07/26/1996
• Issued: 02/09/1999
• Est. Priority Date: 04/19/1994
• Status: Expired due to Term

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Bent, Aaron A., Hagood, Nesbitt W. IV
• Primary Examiner(s): Krynski, William
• Assistant Examiner(s): GRAY, JILL M
• Application Number:
  US08/687,827
• Time in Patent Office: 928 Days
• Field of Search: 428/461, 428/689, 428/692, 310/357, 310/358
• US Class Current: 428/461
• CPC Class Codes: B64C 2027/7222 using airfoil deformation
• CPC Class Codes: B64C 27/72 Means acting on blades
• CPC Class Codes: H10N 30/1061 based on piezoelectric or electrostrictive fibres
• CPC Class Codes: H10N 30/204 using bending displacement, e.g. unimorph, bimorph or multimorph cantilever or membrane benders
• CPC Class Codes: H10N 30/208 using shear or torsion displacement, e.g. d15 type devices
• CPC Class Codes: H10N 30/702 based on piezoelectric or electrostrictive fibres
• CPC Class Codes: H10N 30/852 Composite materials, e.g. having 1-3 or 2-2 type connectivity
• CPC Class Codes: Y02T 50/30 Wing lift efficiency
• CPC Class Codes: Y10T 428/31692 Next to addition polymer from unsaturated monomers

Abstract

Composites for actuating or sensing deformation. In embodiments, the composites have a series of flexible, elongated piezoelectric fibers arranged in a parallel array with adjacent fibers separated by relatively soft polymer. The piezoelectric fibers have a common poling direction transverse to their axial extension. The composite further includes flexible conductive material along the axial extension of the fibers for imposing or detecting an electric field.

Claims

1. A composite for actuating or sensing deformation of a structural member, comprising:

a series of flexible, elongated electro-ceramic fibers arranged in a parallel array, each fiber substantially in parallel with each other, with adjacent fibers separated by relatively soft deformable polymer having additives to vary the electric or elasticity properties of the polymer, each fiber having a common poling direction, and said composite having a length and width greater than a thickness of the composite and axial extension of said fibers being along the length of said composite, said composite further including flexible conductive electrode material along the axial extension of said fibers for imposing or detecting electric fields, said electrode material having an interdigitated pattern forming electrodes of opposite polarity that are spaced alternately and configured to apply a field having compounds along the axis of the fibers, said polymer being interposed between said electrode and said fibers.

2. The composite of claim 1 wherein said additives increase the dielectric constant of the polymer.

3. The composite of claim 1 wherein the polymer has a Young'"'"'s modulus of about 6 GPa.

4. The composite of claim 1 or 3 wherein the polymer has a Young'"'"'s modulus that is at least five times less than the Young'"'"'s modulus of the fibers.

5. The composite of claim 1 wherein said elongated electro-ceramic fibers comprise a piezoelectric material.

6. The composite of claim 1 wherein the fibers have a circular cross section.

7. The composite of claim 1 wherein the fibers have a rectangular cross section.

8. The composite of claim 1 wherein the additives are selected from the group consisting of graphite, metal, ceramic, and electro-ceramic materials.

9. The composite of claim 1 further comprising reinforcement fibers disposed within the polymer.

10. The composite of claim 9 wherein the reinforcement fibers are along the length of the composite and oriented transverse to the axial extension of the electro-ceramic fibers.