Fiber optic impact detection system

• US 7,189,959 B1
• Filed: 03/18/2005
• Issued: 03/13/2007
• Est. Priority Date: 03/18/2004
• Status: Expired due to Fees

• Current Assignee: Fiber Optic Systems Technology Incorporated
• Original Assignee: Fiber Optic Systems Technology Incorporated
• Inventors: Cherpillod, Thierry, Tennyson, Roderick C., Morison, W. Donald
• Primary Examiner(s): Luu; Thanh X.
• Assistant Examiner(s): Ko; Tony
• Application Number:
  US11/082,849
• Time in Patent Office: 725 Days
• Field of Search: 25022714-22716, 340/550, 340/555, 340/541, 385/13
• US Class Current: 250/227.14
• CPC Class Codes: G01L 5/0052 measuring forces due to impact G01L5/0061, G01L5/14 take precedence; impact testing of structures G01M7/08; impact testing of material G01N3/00
• CPC Class Codes: G01M 11/085 the optical fiber being on or near the surface of the DUT
• CPC Class Codes: G01M 11/086 Details about the embedment of the optical fiber within the DUT
• CPC Class Codes: G01M 5/0033 by determining damage, crack or wear
• CPC Class Codes: G01M 5/0091 by using electromagnetic excitation or detection
• CPC Class Codes: G01M 7/08 Shock-testing
• CPC Class Codes: G01V 8/24 using optical fibres

Abstract

Closely spaced conventional optical fibers are arranged in a grid placed between a first surface and a second surface. A penetrating impact onto the first surface results in a hole of a size proportional to the diameter and velocity of the impacting object. The size and shape of the debris plume that travels between the first and second surfaces is also proportional to the diameter and velocity of the impacting object. If the debris plume is sufficiently energetic, a number of the fibers in the grid are broken. The size and shape of the area defined by the broken fibers can be determined simply by determining which fibers are no longer transmitting light. Analytical methods are then used to relate the extent of the damaged area to the location of an MOD impact, the direction from which the impact occurred, and the size of the impacting object.

Claims

1. A fiber optic impact detection system for sensing damage to structures due to impact of debris plumes from high energy objects and MOD particles, said system comprising:

a carrier mesh structure;

a plurality of optical fibers woven into a grid pattern through the carrier mesh structure, each of the plurality of optical fibers having a first end and a second end, the grid pattern defining an x-direction and a y-direction, the plurality of optical fibers comprising a first set of optical fibers extending in the x-direction and a second set of optical fibers extending in the y-direction;

a first multi-fiber optical fiber cable that is fanned out to join to the first end of each of the first set optical fibers;

a second multi-fiber optical fiber cable that is fanned out to join to the first end of each of the second set of optical fibers;

a third multi-fiber optical fiber cable that is fanned out to join to the second end of each of the first set of said optical fibers;

a fourth multi-fiber optical fiber cable that is fanned out to join to the second end of each of the second set of said optical fibers;

a sensor instrument comprising a plurality of light sources that are connected to said first and second multi-fiber optical cables to supply light to said optical fibers in said grid, said instrument also comprising a plurality of optical detectors that are connected to said third and fourth multi-fiber cables to detect light coming through said optical fibers in the grid, said instrument sensing any change in light passing through said fibers, locating the change, and measuring an extent of damage indicated by the change in light; and

a carrier material to which said mesh is attached, said carrier material being capable of being attached to or embedded in a structure to be monitored where said debris plume, produced by a perpendicular incidence impacting object, is detected, located and measured by said sensor instrument by sensing a change in said light conducted by said multitude of optical fibers in said carrier mesh over an approximately rectangular area and converting said rectangular area into an equivalent circular or elliptical area, and converting said circular or elliptical area into a diameter of said impacting object and a diameter of the entry hole for impacts on metal and composite materials.

2. The fiber optic impact detection system recited in claim 1, wherein said multitude of optical fibers is comprised of single-mode or multi-mode telecommunication grade fibers.

3. The fiber optic impact detection system recited in claim 1, wherein said carrier mesh is comprised of an open weave or fabric that allows said multitude of optical fibers to be woven in at a spacing such that the light being conducted through the plurality of fibers in said grid pattern is affected by said debris plumes.

4. The fiber optic impact detection system recited in claim 1, wherein a plurality of said carrier meshes and optical fiber grids are multiplexed together in communication with the same said sensor instrument.

5. The fiber optic impact detection system recited in claim 1, wherein said multitude of light detectors are CCDs (charge coupled devices) in which said multitude of optical fibers in said multi-fiber cables are mechanically positioned over a plurality of pixels in said CCDs.

6. The fiber optic impact detection system recited in claim 1, wherein said carrier material is flexible.

7. The fiber optic impact detection system recited in claim 1, wherein the instrument senses the change in the light at user-selectable scanning rates and modes.

8. The fiber optic impact detection system recited in claim 1, wherein the instrument also performs one of storing a detection result, displaying the detection result and triggering alarms to warn of the damage.

9. A method for sensing damage to structures due to impact of debris plumes from high energy objects and MOD particles, said method comprising:

(a) providing a fiber optic detection system comprising;

a carrier mesh structure;

a plurality of optical fibers woven into a grid pattern through the carrier mesh structure, each of the plurality of optical fibers having a first end and a second end, the grid pattern defining an x-direction and a y-direction, the plurality of optical fibers comprising a first set of optical fibers extending in the x-direction and a second set of optical fibers extending in the y-direction;

a first multi-fiber optical fiber cable that is fanned out to join to the first end of each of the first set optical fibers;

a second multi-fiber optical fiber cable that is fanned out to join to the first end of each of the second set of optical fibers;

a third multi-fiber optical fiber cable that is fanned out to join to the second end of each of the first set of said optical fibers;

a fourth multi-fiber optical fiber cable that is fanned out to join to the second end of each of the second set of said optical fibers;

a sensor instrument comprising a plurality of light sources that are connected to said first and second multi-fiber optical cables to supply light to said optical fibers in said grid, said instrument also comprising a plurality of optical detectors that are connected to said third and fourth multi-fiber cables to detect light coming through said optical fibers in the grid, said instrument sensing any change in light passing through said fibers, locating the change, and measuring an extent of damage indicated by the change in light; and

a carrier material to which said mesh is attached, said carrier material being capable of being attached to or embedded in a structure to be monitored;

(b) attaching said mesh to, or embedding said mesh in, the structure to be monitored; and

(c) using said instrument to measure the extent of the damage wherein, when said debris plume is produced by perpendicular incidence impacting object, step (c) comprises detecting, locating, and measuring said debris plume by sensing a change in said light conducted by said multitude of optical fibers in said carrier mesh over an approximately rectangular area and converting said rectangular area into an equivalent circular or elliptical area, and converting said circular and elliptical area into the a diameter of said impacting object and a diameter of the entry hole for impacts on metal and composite materials.

10. The method recited in claim 9, wherein said multitude of optical fibers is comprised of single-mode or multi-mode telecommunication grade fibers.

11. The method recited in claim 9, wherein said carrier mesh is comprised of an open weave or fabric that allows said multitude of optical fibers to be woven in at a spacing such that the light being conducted through the plurality of fibers in said grid pattern is affected by said debris plumes.

12. The method recited in claim 9, wherein a plurality of said carrier meshes and optical fiber grids are multiplexed together in communication with the same said sensor instrument.

13. The method recited in claim 9, wherein said multitude of light detectors are CCDs (charge coupled devices) in which said multitude of optical fibers in said multi-fiber cables are mechanically positioned over a plurality of pixels in said CCDs.

14. The method recited in claim 9, wherein said carrier material is flexible.

15. The method recited in claim 9, wherein step (c) is performed at user-selectable scanning rates and modes.

16. The method recited in claim 9, further comprising one of storing a detection result, displaying the detection result and triggering alarms to warn of the damage.

17. The method of claim 9, wherein step (b) comprises retrofitting the structure to be monitored with the carrier mesh.

18. The method of claim 17, wherein the structure to be monitored is a spacecraft.

19. The method of claim 9, wherein the structure to be monitored is a spacecraft.