Method for producing a composite structure including a piezoelectric element
First Claim
1. A method of producing a composite structure including a plate-shaped piezoelectric element sandwiched and adhesively bonded between two fiber composite panels, said method comprising the following steps:
- a) applying at least one tensile pre-stressing force to each of said fiber composite panels respectively in a plane of each of said fiber composite panels so as to elongate each of said fiber composite panels in said plane, wherein said at least one pre-stressing force is applied to and is effective along a force direction lying in said plane;
b) while continuing and maintaining said applying of said at least one pre-stressing force, adhesively bonding said fiber composite panels respectively onto opposite surfaces of said piezoelectric element; and
c) after said adhesive bonding has securely bonded said fiber composite panels onto said piezoelectric element, discontinuing said applying of said at least one pre-stressing force, so that said fiber composite panels respectively relax in a direction opposite said force direction in said plane and thereby an internal stress is induced in said piezoelectric element.
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Abstract
A composite structure (3) includes a piezoelectric element (1) sandwiched between fiber composite panels (2). The composite structure can be used as an actuator element. In a method for producing the composite structure, the fiber composite panels are pre-stressed and pre-strained by applying respective pre-stressing forces (F1, F2) in opposite directions along two substantially perpendicular axes in the plane of the panel. The pre-stressed and pre-strained condition of the fiber composite panels (2) is maintained, while the panels are adhesively bonded (5) surfacially onto the piezoelectric element (1). After the bonding is completed, the pre-stressing forces are removed from the fiber composite panels. As a result, in the finished composite structure (3), the fiber composite panels (2) are under internal tension, while the piezoelectric element (1) is under internal compression. The pre-stressing forces (F1, F2) are particularly selected in magnitude and direction to achieve the required resultant balance of tension and compression within the composite structure (3). The pre-compression of the piezoelectric element (1) should be sufficient so that operating loads on the composite structure do not result in tension loading of the piezoceramic element, while substantially maintaining the useful active strain range of the overall composite structure.
43 Citations
27 Claims
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1. A method of producing a composite structure including a plate-shaped piezoelectric element sandwiched and adhesively bonded between two fiber composite panels, said method comprising the following steps:
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a) applying at least one tensile pre-stressing force to each of said fiber composite panels respectively in a plane of each of said fiber composite panels so as to elongate each of said fiber composite panels in said plane, wherein said at least one pre-stressing force is applied to and is effective along a force direction lying in said plane; b) while continuing and maintaining said applying of said at least one pre-stressing force, adhesively bonding said fiber composite panels respectively onto opposite surfaces of said piezoelectric element; and c) after said adhesive bonding has securely bonded said fiber composite panels onto said piezoelectric element, discontinuing said applying of said at least one pre-stressing force, so that said fiber composite panels respectively relax in a direction opposite said force direction in said plane and thereby an internal stress is induced in said piezoelectric element. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23)
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24. A method of producing a composite structure including a plate-shaped piezoelectric element sandwiched and adhesively bonded between two fiber composite panels, said method comprising the following steps:
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a) straining and thereby elongating each of said fiber composite panels into an elongated condition in at least one strain direction respectively in a flat plane of each of said fiber composite panels; b) while holding said fiber composite panels in said elongated condition, adhesively bonding said fiber composite panels respectively onto opposite surfaces of said piezoelectric element; and c) after said step b), discontinuing said holding of said fiber composite panels in said elongated condition and allowing said fiber composite panels to relax opposite said straining in said at least one strain direction, thereby imposing an internal compression stress in said piezoelectric element. - View Dependent Claims (25, 26, 27)
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Specification