Abstract:
A method and apparatus for evaluating the suitability of an encapsulated electrical circuit for use in a particular service environment provides for immersing the encapsulated circuit in a slightly conductive evaluating fluid whose chemical composition approximates the environment into which the circuit will be placed in service. The thus-immersed circuit is then subjected to a reduced-pressure testing environment to draw air and other retained gases out of internal voids within the encapsulated circuit. The pressure of the testing environment is slowly increased to cause the encapsulated circuit to ingest a quantity of the evaluating fluid. An input signal is then applied to the circuit and the circuit's response to the input signal is monitored over a predetermined time period.
Abstract:
An apparatus (60) or system (30) for determining a differential time derivative of strain in a device that has a low coherence light source (32) coupled to a plurality of Fabry-Perot etalons (62). The reflected signals from the Fabry-Perot etalons are coupled to a beam splitter (44) or acousto-optic modulator (66). A first beam (48) and a second beam (50) from the output (46) of the beam splitter (44) are combined in at least one interferometer (52, 64). The outputs of the interferometers (64) are detected by a plurality of detectors (124). The outputs of the detectors (124) are coupled to a plurality of FM demodulators (127). The output of the FM demodulators (127) are a plurality of signals proportional to the difference in the time derivative strain at the pair of mirrors (94, 96) of one of the Fabry-Perot etalons (62).
Abstract:
A strain sensor (50) combines an intrinsic Fabry-Perot interferometer (IFPI) (60) with an extrinsic Fabry-Perot interferometer (EFPI) (56, 62). The IFPI (60) is between two EFPIs (56, 64) and shares its two air to glass mirrors (58, 64). The outside edges (54, 66) of the two EFPIs (56, 64) are connected to an optical fiber (52). The strain sensor (164) can be implemented on a semiconductor chip (150). A waveguide (156) on the semiconductor chip (150) is etched to form two blocks (158) with an island section (162) between them. The two blocks (158) form the EFPI and the center section (162) forms the IFPI. A strain measurement system (100) that takes advantage of the strain sensor (50) has a laser (102) coupled to an optical fiber (106) containing one or more strain sensors (108). A coupler (104) directs the reflected light from the sensors (108) to a tunable Fabry-Perot etalon (114). The output of the tunable Fabry-Perot etalon (114) is coupled to a photodetector (116). A controller (118) monitors the output of the photodetector (116) and controls the tunable Fabry-Perot etalon (114).
Abstract:
A fiber optic sensing system and method comprise a continuous optical fiber including at least three mirrors defining at least two contiguous optical cavities. Preferably, each optical cavity has a unique length so that the reflected optical signal associated with a given optical cavity will have a unique phase difference or wavelength allowing each of the respective optical signals to be selectively detected. A physical phenomenon acting on a given optical cavity can be sensed by determining changes in the respective optical signal reflected from that optical cavity. This sensing system allows a single optical fiber to include both integrating and point sensors. In addition, this system can be incorporated in smart structures.
Abstract:
A method of repairing a composite material product by adhering a repair patch to the composite material product with an adhesive or epoxy resin that includes magnetic particles. Thus, the adhesive or epoxy resin can be cured by electromagnetically exciting the magnetic particles, such as by microwave heating. The electromagnetically excited magnetic particles internally heat the adhesive or epoxy resin to the predetermined Curie Point temperature of the magnetic particles such that the adhesive or epoxy resin cures in a uniform and inspectable fashion. The magnetic particles can be mixed into an adhesive, such as a paste adhesive, a film adhesive or a foam adhesive, to create a magnetic particle integrated adhesive. The magnetic particle integrated adhesive can then be applied between a precured repair patch and the underlying composite material product. Alternatively, the magnetic particles can be distributed within the organic resin of an uncured repair patch such that the repair patch can be simultaneously cured and adhered to the composite material product by electromagnetically exciting the magnetic particles. In either embodiment, the adhesive or the epoxy resin is adapted to cure within a predetermined range of cure temperatures. Thus, the magnetic particles, such as Ferrous Silicide, should have a predetermined Curie Point temperature within the predetermined range of cure temperatures.
Abstract:
An improved warp/knit stitch reinforced multi-axial non-crimp layered fabric sheet used in structural applications, as for example, in aircraft and water applications, e.g., the skin of an airplane wing or fuselage structure, in water applications, e.g., skins of surfboards and boats, and in other areas where high strength and relatively light weight is required. The fabric is comprised of a plurality of plies facewise disposed upon one another and knitted or stitched to form a structural sheet. Each fabric ply is made of strands of aligned structural fibers which can be later impregnated and even pre-impregnated with a resin curable matrix. The improved sheet is formed by applying unidirectional non-crimp and non-woven plies of different angular relationship to one another, e.g., a +45 DEG , a 90 DEG and a -45 DEG ply and locating 0 DEG plies in essentially any position in the ply arrangement such that the 0 DEG ply can be on the bottom of the sheet, on top of the sheet, or interposed between plural ply layers of the sheet. The sheets are then knitted or stitched together to make a stock of multiaxial fabric layers. The fiber weight and thickness can also be varied throughout the sheets by using plies of different thicknesses or differing weights of fibers. Moreover, the percentage of a certain type of fiber in a particular ply can be varied. In addition, damage tolerance can be built into the cured laminate. Further, doublers and local area reinforcements can also be included in the sheet. In addition, a warp/knit, or warp/stitched fabric may be made to a desired width without otherwise affecting the structural properties of the sheet. An apparatus and a method for producing the fabric is disclosed.
Abstract:
An optical switch network (10) which includes a plurality N of cascaded optical switching stages, each mth one of the switching stages including 2 Mach-Zehnder interferometers (12) where m = 1 through N. The input port of the Mach-Zehnder interferometer (12) of the first one of the optical switching stages receives an optical input signal, and the 2 Mach-Zehnder interferometers (12) of the Nth one of the optical switching stages provide a total of 2 output ports. Each of the Mach-Zehnder interferometers is preferably an unbalanced Mach-Zehnder interferometer, and the optical input signal preferably has a wavelength which is a selected one of 2 selectable wavelengths. Also disclosed is an optical time delay network (30) comprised of an optical switch network as described above, and a plurality 2 of optical delay lines of different lengths coupled to respective ones of the 2 output ports of the Nth one of the optical switching stages, each of the optical delay lines (30) being comprised of an optical waveguide having a light reflecting end.
Abstract:
A system and method to fanout, breakout and splice into optical fibers in a ribbon cable trunkline extending throughout an aircraft with optical minimal loss. Boxes are positioned at strategic locations along the aircraft's fiber optic trunkline. Within each box, one or more fanout cable assemblies are supported and terminated whereby the optical fibers in the ribbon cable are transitioned into individually jacketed fibers for connection to separate locations. When an optical fiber circuit needs to be broken out at the location of a particular box, the proper individually jacket fiber is cut and the end that results is permanently connected to a breakout connector, also positioned through the box, so that the optical circuit appears on the breakout connector outside the box where a mating connector can be used to further route the optical circuit being broken out.
Abstract:
A robust mechanical reversion system which provides the ability to fly and land in the absence of any fly-by-wire controls and which is transparent to the pilot during normal operation. The described invention provides a mechanism which includes redundant linear variable differential transmitters (LVDT) (7, 39) which generates a transmitted signal (8, 40) in proportion to the displacement of the control apparatus (3, 4, 78, 79) in the cockpit. The signal is fed to the flight control computer which determines the magnitude of the change represented by the signal and in turn, commands both the control surface servo actuators as well as an electrical mechanical servo actuator (EMA) (24, 47) located in close proximity to the flight compartment and coupled to the mechanical system to move in proportion to the change. An Electromagnetic Actuator drives the disconnected mechanical system in synchronization with the position of the cockpit controls in the fly-by-wire mode for a given control surface each time the servo actuator(s) for the control surface are electrically commanded by the flight computer (1). This causes the mechanical system to remain in phase with the position of the control elements as if connected thereto. In the event of a failure of the fly-by-wire system the mechanical systemis automatically coupled into the control system through locking actuators which release a coupling mechanism including a interlocking pin, locking cams, clutch or other engagement device and clamps or locks the pilots input to the mechanical control loop thus providing direct mechanical control to the surface actuators (2, 77) with very little transient effects.
Abstract:
A method for providing a ceramic coating on a ceramic or metallic substrate and the ceramic coating composition useful therein. The coating composition comprises a putty-like material comprising a colloidal silica, a base for gelling the silica, a filler, and no more than 50 wt.% of a volatile solvent or solvents. The putty-like material is rolled onto the desired substrate and cured to form a protective ceramic coating of any desired thickness. The cured coating may be fired, if desired.