TECHNOLOGY AREAS: Materials/Processes, Sensors

OBJECTIVE: To develop a new class of fiber optic connectors and other fiber optic components (such as beam splitters, 90 degree reflectors, stress relief elements, fiber conduits, etc) targeted for structural health monitoring applications of military assets (such as submarines, ships and aircrafts). These connectors and components will be very light, have a small foot print; they will be very thin and flexible, easy to interconnect, easy to mount on the surfaces of materials; and finally, they will be reliable and durable.

DESCRIPTION: As a result of the limited amount of resources for buying new military systems, many of our platforms are going through life extension programs (in some cases going well beyond their original design life). As a result there has been a need to increase the number and extent of inspections in order to maintain a minimum level of safety. This in turn has led to reduced readiness and increased costs for fleet operations and support. To address many of these challenges the Navy has been investigating new approaches to maintenance and inspections. Some of these include Condition Based Maintenance (CBM), Reliability Centered Maintenance (RCM), Health and Usage Monitoring (HUMS), and Prognosis. Most of these approaches rely on the use of distributed sensors (accelerometers, thermometers, ultrasonic sensors, strain gauges, fiber optic sensors) which monitor key parameters of the components and structures.

Fiber Optic sensors (such as fiber Bragg Gratings (BG), Fiber Fabry Perrot Interferometers (FFPI), and Long Period Gratings (LPG) to name a few) have been successfully demonstrated for many structural health monitoring applications. Despite their tremendous potential in this area, they have not transitioned to major applications. One of the problems associated with these sensors is with the interconnections that are required in large scale structures. Currently these interconnects are large, heavy, and difficult to mount to the surfaces of materials. Also, they require specialized equipment and expertise when applied to optical fibers in the field. In turn, this makes field repairs of optical fibers difficult. This effort seeks new ideas which would address these difficulties. Intuitively one would want connectors that are easy to apply to fibers, are light, have small foot prints, are flexible, yet make connections that have low losses and are robust.

PHASE I: Demonstrate, in a laboratory environment, a new optical fiber connector. Demonstrate its easiness to attach to an optical fiber, to interconnect between fibers with low insertion losses (typical of standard optical fiber connects) and to surface mount onto a structural component. The contractor shall demonstrate connector robustness and reliability under shock and vibration environments (MIL-SPEC-810). It is advisable that the small business contractor collaborate or coordinate with a major fiber optic connector manufacturer from the inception of the program to facilitate the transition if the program becomes successful.

PHASE II: Develop other fiber optic components such as 90o reflectors and conduits for optical fibers. The 90o reflectors will also be light, thin, with small foot print and easy to interconnect with optical fibers. The conduits are for carrying optical fibers loosely inside of them between two sensing point. These conduits serve the purpose of protecting the fiber, of constraining them from freely moving throughout the structure while providing some room for them to accommodate large strains in the structure. Finally, the contractor will demonstrate mass production capabilities for these fiber optic components.

PHASE III: Retrofit a fiber optic health monitoring system aboard a ship, submarine or aircraft and demonstrate its robustness, repairability, and reliability.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: The requirement for structural health monitoring is applicable to the commercial world. Widespread fatigue damage, corrosion damage and engine maintenance have been determined to be a major source of problems for commercial ship and aviation systems. These systems require health monitoring. Therefore, commercial ship and aviation industries would benefit significantly from these fiber optic components as well.

REFERENCES:
1 ) E.Udd, "Fiber Sensors for Smart Structures", Optical Fiber Sensors: Proceedings of the 6th International Conference, OFS 89, ed. H. J. Arditty, J. P. Dakin, and R. Th. Kersten, Springer-Verlag Berlin Heidelberg pp392-399 (1989).
2) D. W. Jensen, J. Pascual and J. A. August, "Performance of graphite/bismaleimide laminates with embedded optical fibers. Part I: uniaxial tension", Smart Materials and Structures 1(1) pp24-30 (1992).
3) James S. Sirkis, "Optical and mechanical isotropies in embedded fibre optic sensors", Smart Materials and Structures 2(4) pp255-259 (1993).
4) B. A. Sjögren, "Static strength of CFRP laminates with embedded fiber-optic edge connectors", Composites part A: applied science and manufacturing 32(2) pp189-196 (2001).
5) A K Green and E Shafir, "Termination and connection methods for optical fibres embedded in aerospace composite components", Smart Materials and Structures 8(2) pp269-273 (1999).

KEYWORDS: Fiber, Optic, Connectors, CBM, Sensors, Structural Health Monitoring

TPOC: Ignacio Perez
Phone: (703)696-0688
Fax: (703)696-0934
Email: [email protected]
2nd TPOC: Mark Seaver
Phone: (202)767-3590
Fax: (202)767-5790
Email: [email protected]

** TOPIC AUTHOR (TPOC) **

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