Dimensions determination for insulating coatings

• US 7,795,878 B2
• Filed: 10/22/2007
• Issued: 09/14/2010
• Est. Priority Date: 10/22/2007
• Status: Active Grant

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Clements, J. Sidney, Ward, Theresa N., Bennett, Julie K., Anderson, Michael G., Purdy, Aaron T.
• Primary Examiner(s): Dole; Timothy J
• Assistant Examiner(s): HOQUE, FARHANA AKHTER
• Application Number:
  US11/876,574
• Publication Number:
  US 20090102486A1
• Time in Patent Office: 1,058 Days
• Field of Search: 324/72, 324/72.5, 324/536, 324/551, 324/554, 324452-458
• US Class Current: 324/536
• CPC Class Codes: G01N 27/61 Investigating the presence of flaws
• CPC Class Codes: G01R 31/1227 of components, parts or materials G01R31/1209, G01R31/1218, G01R31/18 take precedence; circuits therefor G01R31/14; testing vessels of electrodes G01R31/16

Abstract

Systems and methods for determining the dimensions of insulating coating sections applied to a conductive component are disclosed. The method includes providing a specimen having an insulating coating section of a first surface area and a first thickness. The method further includes conducting a test of the specimen for propagating brush discharges. If the specimen exhibits propagating brush discharges, the method further includes reducing at least one of the first surface area and the first thickness to produce at least one of a second surface area or a second thickness, or reducing a first maximum distance that any portion of the insulating coating may extend from an adjacent static dissipative feature to produced a second maximum distance. In additional embodiments, insulating coating patterns may be established on the component based on at least one of the dimensions of the second surface area, the second thickness, or the second maximum distance.

Claims

1. A method for mitigating a propagating brush discharge from an insulating coating covered component, comprising:

providing a carbon fiber reinforced plastic (CFRP) specimen that represents the component for testing, the CFRP specimen being at least partially covered by a non-conductive insulating coating section of a first surface area and a first thickness;

conducting a test of the CFRP specimen for a propagating brush discharge that results from a capacitance charge in the specimen; and

reducing at least one of the first surface area, the first thickness, a first distance to produce at least one of a second surface area, a second thickness, or a second distance when the CFRP specimen exhibits the propagating brush discharge,

wherein the first distance is a maximum distance any portion of the non-conductive insulating coating section is located from an adjacent static dissipative feature.

2. The method of claim 1, further comprising increasing at least one of the first surface area, the first thickness, or the first distance to produce at least one of a third surface area, a third thickness, or a third distance when the CFRP specimen does not exhibit the propagating brush discharge.

3. The method of claim 2, further comprising:

conducting another test of the CFRP specimen for an additional propagating brush discharge; and

reducing at least one of the third surface area or the third thickness to produce at least one of a fourth surface area, a fourth thickness, or a fourth distance when the CFRP specimen exhibits the additional propagating brush discharge,

wherein the fourth surface area is greater than the first surface area, and the fourth thickness is greater than the first thickness, and the fourth distance is less than the first distance.

4. The method of claim 3, further comprising establishing patterns for the non-conductive insulating coating on the component based on one of (1) at least one of the second surface area, the second thickness, or the second distance, (2) at least one of the third surface area, the third thickness, or the third distance, or (3) at least one of the fourth area, the fourth thickness, or the fourth distance.

5. The method of claim 1, further comprising:

conducting another test of the CFRP specimen for an additional propagating brush discharge, the CFRP specimen including the non-conductive insulating coating section of at least one of the second surface area, the second thickness, or the second distance; and

increasing at least one of the second surface area, the second thickness, or the second distance to produce at least one of a third surface area a third thickness, or a third distance when the CFRP specimen does not exhibit the additional propagating brush discharge,

wherein the third surface area is less than the first surface area, the third thickness is less than the first thickness, and the third distance is greater than the first distance.

6. The method of claim 1, wherein the static dissipative features includes at least one of a bare component surface, a bare fastener, a pin hole that extends to the component, an insulating coating with a dielectric discharge voltage of less than or approximately 4 Kilovolts (kV), or another component with a charge relaxation time constants of one second or less.

7. The method of claim 1, further comprising determining a suitability of the component for a propagating brush discharge test prior to providing the CFRP specimen that represents the component for testing, wherein the determination is made based on at least one of a presence of a electric double layer on the component, a dielectric withstand voltage of the component, or a charge decay time constant of the non-conductive insulating coating section of the specimen.

8. The method of claim 7, wherein the electric double layer is present when the component is grounded, the non-conductive insulating coating is less than a predetermined maximum thickness, and the insulating coating is to separate the component from a source of electrostatic charge.

9. The method of claim 8, wherein the predetermined maximum thickness is 8-10 millimeters.

10. The method of claim 7, the dielectric withstand voltage of the component is determined based on a measured voltage plateau of the component during the application of an increasing electrical potential to the component.

11. The method of claim 7, wherein determining a suitability of the component includes determining that the component is suitable for a propagating brush discharge test when at least one of an electric double layer is present on the component, a dielectric withstand voltage of the components exceeds a predetermined voltage threshold, or the charge decay time constant of the non-conductive insulating coating section is greater than approximately one second.

12. The method of claim 11, wherein the predetermined voltage threshold is approximately 4 Kilovolts.

13. The method of claim 1, wherein conducting a test includes conducting a test of the CFRP specimen for the propagating brush discharge at a relative humidity of less than 30%.

14. The method of claim 1, wherein conducting the test of the CFRP specimen for the propagating brush discharge includes:

Discharging the CFRP specimen that was charged from a predetermined distance; and

determining an occurrence of the propagating brush discharge based on the corresponding discharge pattern produced by the propagating brush discharge.

15. The method of claim 14, wherein conducting the test of the specimen for the propagating brush discharge further includes drying the CFRP specimen for 24 to 72 hours at less than 25% relatively humidity prior to discharging the specimen.

16. The method of claim 14, wherein the predetermined distance is 1.5 inches to 1.75 inches.

17. The method of claim 14, wherein determining the occurrences of the propagating brush discharge includes determining that propagating brush discharge occurred when the one or more discharge patterns includes at least one of a Lichtenberg pattern or a Lichtenberg discharge leader.

18. A method for propagating brush discharge testing, comprising:

discharging a carbon fiber reinforced plastic (CFRP) specimen that was charged from a predetermined distance, the CFRP specimen being at least partially covered by a non-conductive insulating coating section of a first surface area and a first thickness; and

observing a discharge pattern from the CFRP specimen for at least one of a Lichtenberg pattern or a Lichtenberg discharge leader of a propagating brush discharge;

reducing at least one of the first surface area, the first thickness, a first distance to produce at least one of a second surface area, a second thickness, or a second distance when the CFRP specimen exhibits the at least one of the Lichtenberg pattern or the Lichtenberg discharge leader of the propagating discharge;

increasing at least one of the first surface area, the first thickness, or the first distance to produce at least one of a third surface area, a third thickness, or a third distance when the CFRP specimen does not exhibit the at least one of the Lichtenberg pattern or the Lichtenberg discharge leader of the propagating brush discharge,

wherein the first distance is a maximum distance any portion of the non-conductive insulating coating section is located from an adjacent static dissipative feature.