1. Field of the Invention
Sensors for critical stress diagnostic in real time and smart skin especially for aircraft and space vehicles.
2. Description of the Related Art
U.S. Pat. No. 5,797,623 (Hubbard, Aug. 25, 1998) discloses the Smart skin sensor for real time side impact detection. However, no patents or applications are known for sensor or smart skin based on the proposed physical phenomena.
A new family of multifunctional smart coatings based on diamond-like atomic-scale composite (DL ASC) materials developed over the past decade. The coatings will provide a real-time control of the surface stress distribution and potentially dangerous stress diagnostic for the most critical parts of flying vehicles.
a, b, and c shows shift of critical electrical field under stress: compressive stress shifts the threshold to the lower values of applied fields, while tensile stress shifts this threshold in the direction of higher fields.
FIG. 3,a shows array on electrically conducting substrate:
FIG. 3,b shows array on dielectric substrate:
FIG. 3,c shows the array with lateral electrodes:
Joint electron-structural phase transition (the static Jan-Teller effect) occurs in diamond-like stabilized carbon at critical electrical field. When electrical field exceeds some certain critical point, typically E*=2×105 V/cm, the local fine structure of diamond-like matrix suddenly changes. The mean distance between nucleus of carbon atoms in certain atomic groups decreases, and electronic structure of those groups changes as well, adjusting to a new atomic arrangement. Such a joint electron-structural phase transition results with a sharp jump-like reversible increase of electrical conductivity of diamond-like dielectric on 3 to 4 orders of magnitude (
This physical phenomena was previously known as “the static Jan-Teller effect” by the names of two physicists who theoretically predicted it (H. Jahn and E. Teller, 1937). Although static Jan-Teller effect is found in many crystals, usually it observed by certain particularities of optical spectra, ultrasonic waves propagation, or electronic paramagnetic resonance. Strong and sharp change of electrical conductivity first observed in diamond-like carbon is unusual or even unique phenomena, and it is due to specific combination of electronic and mechanical properties of this low-density diamond-like carbon structures.
Under external pressure or stretching force, or under internal compressive or tensile stress, the critical field is slightly changes (
In accordance with present invention, silica-stabilized dielectric film is used as sensitive material for detection and diagnostics of dangerous stress and its location in structures, such as aircraft. This sensitive material may be used in individual sensors, and as a basic sensitive material for sensor arrays for smart skin technology (
a–c shows 3 different approaches for electrical connection of diamond-like dielectric sensors into array:
a shows array on electrically conducting substrate:
1—diamondlike dielectric layer (sensitive material), 2—conducting substrate, 3, 4—top electrodes and connecting lines, 5—bus to substrate.
b shows array on dielectric substrate: 1-diamondlike electric layer (sensitive material), 2-dielectric substrate, 3-top electrodes and connecting lines, 4, 5-address buses, 6-electrically conducting sub-layer.
c shows the array with lateral electrodes: 1—diamondlike dielectric layer (sensitive material), 2—substrate (dielectric or conductor), 7, 8—lateral electrodes.
Typically, the electrical field is applied cross the sensitive film thickness, and said thickness is typically in the range from a few hundred nanometers to a few micrometers. Depending on electrical properties of diagnosing surface, the different array geometry and connection between individual sensors may be applied, as it shown on
It can sense stress space distribution along the entire surface of the structure, such as internal and/or external surface of the aircraft wing, in real time i.e., fractions of a millisecond. The sensors may be deposited directly upon the wing surface. The electrodes may be deposited after the sensitive material layer using the same technology and equipment while introducing metals in diamond-like carbon matrix. Both dielectric and conducting materials possess exceptionally high adhesion, abrasion and chemical resistance, excellent smoothness and tribological properties, thus simultaneously providing protection and improving aerodynamic properties of the wings.
The sensors is simple to manufacture and deposit along the entire structure.
For “smart skin” application, the advantage of Jan-Teller transition is completely dielectric state of sensitive smart film: it allows using a continuous “smart skin” sensitive in any point where a dangerous stress occurred (
Furthermore, the absolute value of the applied electrical voltage may be controllably varied through the sensor array, and the stress measurements, both compressive and tensile may be scanned along the entire smart skin in a reasonable proximity of critical value.
The coated body may be conductive or insulating. In the last case, a conducting sub-layer as a ground electrode (
A process for depositing the coating system may be shown in the following example:
1. The electrically conducting subject (
2. The subject to be coated with smart skin is located in vacuum deposition chamber.
3. Air is pumped out of said deposition chamber up to about 1.0×10−5 Torr.
4. The chamber is filled with argon up to pressure of about 5×10−5 Torr, and the surface to be coated cleaned in the argon low pressure discharge during about 10 minutes.
5. Unalloyed stabilized diamond-like carbon 0.5 micrometer thick dielectric layer is deposited upon the surface of the structure (
6. Chromium-alloyed diamond-like Me-C 1-micrometer thick conducting layer (as it shown in cross-section on
7. The chamber is filled with air up to atmospheric pressure and opened, the subject removed from chamber.
8. The patterning of electrodes and conducting lines (
9. The operations 2,3,4,5 repeated, and top dielectric layer deposited as a final protective layer of smart skin.
10. Operation 7 repeated.
11. The conducting lines connected with electronic control systems using standard technique known from the prior art.
The present invention, therefore, is well adopted to carry out the objects and attain the ends and advantages mentioned. While preferred embodiments of the present invention have been described for the purpose of disclosure, numerous other changes in the details of the material structure, composition, graded functionality and device designs can be carried out without departing from the spirit of the present invention which is intended to be limited only by the scope of the appended claims.
This application claims priority on U.S. Provisional Application Ser. No. 60/414,198 filed on Sep. 27, 2002 entitled: METHOD AND APPARATUS FOR DIELECTRIC SENSORS AND SMART SKIN FOR AIRCRAFT AND SPACE VEHICLES.
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