Systems, methods and tools for the interrogation of composite strength members
Systems, methods and tools for the interrogation of fiber-reinforced composite strength members to assess the structural integrity of the strength members. The systems and methods utilize the transmission of light through optical fibers that are embedded along the length of the strength members. The inability to detect light through one or more of the optical fibers may be an indication that the structural integrity of the A strength member is compromised. The systems and methods may be implemented without great difficulty and may be implemented at any time in the life cycle of the strength member, from production through installation. The systems and methods have particular applicability to bare overhead electrical cables that include a fiber-reinforced strength member.
1. A system configured for the detection of a defect in an elongate fiber-reinforced composite strength member, comprising:
a fiber-reinforced composite strength member, the strength member comprising at least a first strength element, the first strength element comprising:
a binding matrix;
a plurality of reinforcing fibers operatively disposed within the binding matrix to form a fiber-reinforced composite;
at least a first optical fiber embedded within the fiber-reinforced composite and extending from a first end of the fiber-reinforced composite to a second end of the fiber-reinforced composite, the first optical fiber having a first end and a second end; and
a light transmitting device operatively connected to a first end of the strength member, the light transmitting device comprising a light source that is operatively connected to a power source and that is configured to transmit light having a wavelength of at least about 300 nm and not greater than about 1700 nm into the first end of the first optical fiber; and
a light detecting device operatively connected to a second end of the strength member, the light detecting device comprising a light detector that is configured to detect the light emitted by the light source through the second end of the first optical fiber.
2. The system recited in claim 1 , wherein the light source is configured to emit light having a primary wavelength in the infrared region.
3. The system recited in claim 1 , wherein the light source is configured to emit light having a primary wavelength of at least about 800 nm.
4. The system recited in claim 1 , wherein the light source is configured to emit light having a primary wavelength of not greater than about 1000 nm.
5. The system recited in claim 1 , wherein the strength element includes at least a second optical fiber embedded within the fiber-reinforced composite and extending from the first end of the fiber-reinforced composite to the second end of the fiber-reinforced composite, the second optical fiber having a first end and a second end.
6. The system recited in claim 5 , wherein the strength element includes at least a third optical fiber embedded within the fiber-reinforced composite and extending from the first end of the fiber-reinforced composite to the second end of the fiber-reinforced composite, the third optical fiber having a first end and a second end.
7. The system recited in claim 6 , wherein the strength element includes at least a fourth optical fiber embedded within fiber-reinforced composite and extending from the first end of the fiber-reinforced composite to the second end of the fiber-reinforced composite, the fourth optical fiber having a first end and a second end.
8. The system recited in claim 1 , wherein an electrical conductor is disposed around and supported by the strength member to form an electrical cable.
9. The system recited in claim 8 , wherein the electrical cable has a length of at least about 100 meters.
10. The system recited in claim 8 , wherein the electrical cable has a length of not greater than about 3500 meters.
11. The system recited in claim 1 , wherein the first optical fiber is a single mode optical fiber.
12. The system recited in claim 1 , wherein the light source comprises a light-emitting diode (LED).
13. The system recited in claim 1 , wherein the light detecting device comprises a concave lens that is disposed between the end of the composite strength member and the light sensor and is configured to focus the transmitted light onto the light sensor.
14. The system recited in claim 1 , wherein the light sensor is selected from a CCD sensor and a CMOS sensor.
15. The system recited in claim 1 , further comprising an index-matching material disposed on at least the first end of the fiber-reinforced composite.
16. The system recited in claim 15 , wherein the index-matching material has a refractive index of at least about 1.40 and not greater than about 1.50.
17. The system recited in claim 1 , wherein the light source is an incoherent light source.
18. The system recited in claim 1 , wherein the first optical fiber does not extend beyond the first end of the fiber-reinforced composite.
19. The system recited in claim 18 , wherein the first optical fiber does not extend beyond the second end of the fiber-reinforced composite.
20. The system recited in claim 19 , wherein the first and second ends of the strength element each comprise a smooth planar surface.
21. The system recited in claim 5 , wherein the second optical fiber does not extend beyond the first end of the fiber-reinforced composite and does not extend beyond the second end of the fiber-reinforced composite.
22. A system configured for the detection of a defect in an elongate fiber-reinforced composite strength member, comprising:
a fiber-reinforced composite strength member, the strength member comprising at least a first strength element, the first strength element comprising:
a binding matrix;
a plurality of reinforcing fibers operatively disposed within the binding matrix to form a fiber-reinforced composite;
at least a first optical fiber embedded within the fiber-reinforced composite and extending from a first end of the fiber-reinforced composite to a second end of the fiber-reinforced composite, the first end and the second end each comprising a smooth and planar surface, the first optical fiber having a first end and a second end, wherein the first end of the optical fiber does not extend beyond the first end of the fiber-reinforced composite and the second end of the optical fiber does not extend beyond the second end of the fiber-reinforced composite; and
a light transmitting device operatively connected to a first end of the strength member, the light transmitting device comprising a light-emitting diode that is operatively connected to a power source and that is configured to transmit incoherent light having a wavelength of at least about 300 nm and not greater than about 1700 nm into the first end of the first optical fiber; and
a light detecting device operatively connected to a second end of the strength member, the light detecting device comprising a light detector that is configured to detect the light emitted by the light-emitting diode through the second end of the first optical fiber.