Patent Application
20230107417
This disclosure relates generally to the field of fiber-composite component manufacture and more specifically to the manufacture of aircraft having fiber-composite airframe components.
Aircraft can be made using lightweight materials in order to optimize performance and fuel economy. For some aircraft, such lightweight materials include fiber-composite materials, in which strong, lightweight fibers are immobilized in a cured resin matrix. Carbon fibers are especially suitable for fiber-composite airframe components. The technology for manufacture of fiber-composite airframe components is relatively new. Accordingly, there remain significant opportunities for improvement of the manufactured components—in terms of strength, weight, cost, etc.—and for improvement in the efficiency of manufacture.
One aspect of this disclosure relates to a method to reinforce a junction of one or more aircraft components, the one or more aircraft components including fiber composite and forming an elongate conduit. The method comprises abrading the junction and applying sealant along the junction from a tool moveable through the conduit, the tool exerting force on an interior surface of the conduit opposite the junction.
Another aspect of this disclosure relates to a tool for reinforcing a junction of one or more aircraft components, the one or more aircraft components including fiber composite and forming an elongate conduit. The tool comprises a translational-bearing element configured to travel an interior surface of the conduit opposite the junction to support movement of the tool through the conduit. The tool also comprises a sealant applicator configured to apply sealant along the junction.
This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is the scope of the claimed subject matter limited to implementations that address any problems or disadvantages noted in any part of this disclosure. The features, functions, and advantages described herein may be achieved independently in some implementations but may be combined in other implementations.
This disclosure will be better understood from reading the following Detailed Description with reference to the attached drawing figures, wherein:
An aircraft may include numerous stiffener members bonded to the aircraft skin and forming long, narrow conduits, with junctions between the bonded components. The stiffener members may comprise fiber-composite material, in some examples. This disclosure provides a series of solutions for reinforcing bonded junctions of fiber-composite material by application of a sealant. The overall approach relies on a system of one or more compact tools that travel down the conduit to enact a series of functions to achieve the reinforcement objective. Such functions include abrading and cleaning an area of incomplete or uneven bonding, applying the sealant, and inspecting the finished seal.
Turning now to the drawings,
The compositions of the fiber-composite materials envisaged herein are not particularly limited. Example fiber-composite materials include carbon fibers immobilized in a polymer. The polymer may be thermosetting in some examples and thermoplastic in other examples. Example thermosetting polymer resins may include one or more of an epoxy-amine resin, a urethane resin, or an acrylamide resin. Such resins may be curable in air. Example thermoplastic polymers include polyetherether ketone (PEEK) and polyetherketoneketone (PEKK), among others.
Hat stringer 320 is bonded to skin 312 of an aircraft wing; it forms, in combination with the skin, an elongate, hollow conduit 328. Flange regions 326 enable bonding between the hat stringer and the skin. The bonding is primarily via an adhesive, such as a thermosetting adhesive polymer film. Examples include AF555 (a product of 3M of Saint Paul, Minn.) or Metlbond 1515 (a product of Solvay of Brussels, Belgium). In the case of thermoplastic matrices, the bonding may be a function of the native matrix. Hardware fasteners (e.g., steel bolts, not shown in the drawings) may also be used in selected locations. For improved resistance to mechanical stresses, conduit 328 includes radius filler 330—a curled or rolled segment of fiber-composite material arranged where skin 312 meets hat stringer 320H at an acute angle. Flange extensions 332 support the radius filler and provide an extended area of adhesive bonding between the hat stringer and the skin. In some examples, a flange extension includes at least two plies of a carbon fiber composite material, for a total thickness of about 16 mils.
Any, some, or all of the conduits 328 in an aircraft wing section may accommodate cables (electrical, fiber-optic, mechanical, etc.), compressed-gas lines, and/or vacuum lines (not shown in the drawings). Any, some, or all of the conduits may provide passive pressure equalization across different portions or compartments of a wing section, including fuel-tank portions. It will be noted that the aircraft shown in
Naturally, the structural integrity of an airframe depends on high-quality bonding among airframe components—e.g., between stiffener members and the aircraft skin. In certain scenarios, however, incomplete or uneven bonding may affect the arc discharge capability of the junction. For instance, when an aircraft is struck by lightning, arc discharge may occur around junctions of fiber-composite components that are not smoothly bonded.
Fortunately, technology for detailed imaging of junctions of fiber-composite aircraft components is available. For instance, sonography can be used to detect an area of incomplete or uneven bonding at junction 334, which could allow arc discharge in the event of a lightning strike. Nevertheless, even when such an area is located in conduit 328, the great length and narrow aperture of the conduit make it difficult to reinforce the junction. This disclosure provides a series of tools and methods to address that issue.
In that spirit,
Tool 538 includes one or more translational-bearing elements 544. Each translational-bearing element is configured to travel interior surface 546 of conduit 528, which is opposite junction 534. In examples in which conduit 528 is the same or similar to conduit 320 of
In the illustrated example, each translational-bearing element 544 of tool 538 comprises a wheel 548. Four wheels are shown in
Tool 538 includes translation register 552. The translation register provides an output signal that varies in dependence on a distance of travel of tool 538 through conduit 528. In examples in which tool 538 is manually operated, output signal from the translation register may be reported to the operator of the tool. In examples in which tool 538 is operated via an electronic process controller (vide infra), the electronic process controller may be configured to receive the output signal from the translation register and thereby know the position of the tool within the conduit.
The configuration of translation register 552 is not particularly limited. In some examples, the translation register may include a physical measuring strip or wire attached to a point of reference at one end of the conduit. In some examples, the translation register may include an optical or acoustic time-of-flight or interferometric measurement device. In the illustrated example, the translation register includes a revolution counter 554, which outputs one or more pulses for each revolution of the connected wheel. With knowledge of the current position of tool 538 within conduit 528, the operator or electronic process controller can drive the tool to the location of an area of incomplete or uneven bonding within the conduit.
Continuing in
Tool 538 includes a biasing element 562 arranged between translational-bearing elements 544 and sealant applicator 556. The biasing element is configured to controllably bias the sealant applicator against junction 534 by varying the distance of separation between the sealant applicator and the translational-bearing elements. When the biasing element is actuated, tool 538 exerts an upward force F′ against junction 534 and a downward force F against interior surface 546, where F is the sum of F′ and the weight of the tool. The configuration of the biasing element may vary from one example to another. In some examples, the biasing element may comprise an electromechanical (e.g., solenoid-based) or pneumatic actuator, such as a linear actuator. In the illustrated example, biasing element 562 includes an air bladder 564. When tool 538 is to be moved through conduit 528 with no contact between brushes 560 and junction 534, the air bladder is maintained in a deflated state. When sealant 558 is to be brushed onto the junction at the current position of the tool, the air bladder is inflated and maintained in an inflated state.
In examples in which brush coating is enacted manually, the operator of the tool may manually inflate and deflate the air bladder as needed, using an off-board valve coupled fluidically to a pump or source of compressed air. In the example illustrated in
Recalling the configuration illustrated in
Continuing now in
Sealant may be supplied to nozzle 670 in any suitable manner. In the example illustrated in
Tool 638 also includes, as shown in
In some examples, repeated back-and-forth movement of the tool over the desired interval, with abrasion element 784 engaging junction 734, may provide sufficient abrasion to the area of incomplete or uneven bonding. In other examples, the stage on which the abrasion element is arranged may be a rotating or reciprocating stage, which amplifies the abrasion effect.
In some examples, the surface of the abrasion element that contacts the junction may be substantially planar. In other examples, the surface may be contoured to conform to the junction. Accordingly, in the illustrated example, abrasion element 784 has a raised middle section 786. The step height of the raised middle section corresponds to the thickness of flange extensions 732; the width of the raised middle section corresponds to the gap between the flange extensions in conduit 728.
Tool 838 also includes a mechanical-testing element 888 configured for mechanically testing the integrity of the seal applied to junction 834. The shape and form of the mechanical-testing element are not particularly limited. In some examples, the mechanical-testing element is a mostly rigid structure with a soft, tacky tip, like a pencil eraser. The mechanical-testing element is coupled to the biasing element, so that when the biasing element is activated the tip makes contact with junction 734. When the biasing element is deactivated, the tip is released from the junction. Accordingly, when the biasing element is actuated, tool 838 exerts an upward force F′ against junction 834 and a downward force F against interior surface 846, where F is the sum of F′ and the weight of the tool. By controlling actuator 766 of the biasing element and concurrently moving the tool over the area of the junction that was sealed, the mechanical-testing element can be made to selectively rub on the sealed portion of the junction. By analyzing the image from camera 880, the operator or electronic process controller can determine whether any portion of the seal has lifted off of the junction pursuant to the rubbing.
At optional step 942D an area of incomplete or uneven bonding in the junction is located. The area can be located by imaging the conduit, plural conduits, or portions thereof, as examples. The imaging or other locating mechanism is calibrated to provide a reliable position reference, at least along the length of the conduit, and is detailed enough to reveal at least some of the internal structure of the conduit. In some examples the imaging comprises sonography—e.g., ultrasonic imaging. In other examples the imaging may comprise one or more diffraction techniques.
At 942E of method 940 the junction is abraded. In methods that include location of an area of incomplete or uneven bonding (e.g., 942D of method 940), abrasion may be localized to the area. More specifically, if such an area extends from Z1 to Z2 on the right or left junction of the conduit, then an interval from Z1−δ to Z2+δ may be abraded. In some examples, the abrasion step may be enacted using a tool such as tool 738, having an abrasion element 784.
At 942F, subsequent to abrasion and prior to application of sealant, the junction is cleaned. Cleaning is done to remove grit and other particulates released in the abrasion. In some examples, the cleaning includes vacuum cleaning. In some examples the cleaning includes wiping with a cloth—e.g., a particulate-trapping cloth. In some examples one or more moistened cloths may be used. Such moistened cloths may be moistened with water, a detergent solution, or a solvent. Suitable solvents include ketone solvents such as acetone, methylethyl ketone, and methylpropyl ketone, as non-limiting examples. In some examples the cleaning operation may be localized to the abraded area or areas of the conduit and may be enacted via a tool inserted down the conduit, akin to the tools described herein. In examples that involve wetting the interior of the conduit, the conduit is allowed to dry before processing is continued. Drying may be achieved by forcing air through the conduit, in some examples.
As noted hereinabove, any, some, or all of the functions of method 940 may be enacted via a system of tools that travel down the conduit to the location of an area of incomplete or uneven bonding. Furthermore, any, some, or all of the tools may include an electronic process controller that automates one or more of the functions. Automated travel of a tool to a position of incomplete or uneven bonding will now be described with reference to a sealant-application tool. It will be understood, however, that an analogous description applies equally to any of the other tools and functions.
At 942G of method 940, an electronic process controller of the sealant application tool receives a signal that varies in dependence on a distance of travel of the tool through the conduit. The signal may be the output of a translation register, such as translation register 552 or translation register 652. As noted above, the electronic process controller is provided a target position of an area of incomplete or uneven bonding in the junction along the conduit. The electronic process controller also maintains the current position of the tool within the conduit. Based on the difference between the target position and the current position, the electronic process controller starts the tool moving in the appropriate direction, while updating the current position based on the output of the translation register. When the tool reaches a desired distance from the incomplete or uneven bonding, the electronic process controller energizes the actuator that triggers application of the sealant.
At 942H, accordingly, sealant is applied along the junction from a tool moveable through the conduit. During sealant application the tool exerts force on the interior surface of the conduit opposite the junction. As noted hereinabove, the tool may be one of a plurality of tools moveable through the conduit and configured to exert force on the interior surface of the conduit opposite the junction. In methods that include location of an area of incomplete or uneven bonding (e.g., 942D of method 940) the sealant may be applied to only the area or areas. The sealant may be applied along a suitable length interval, as described above in the context of the abrading operation.
In some examples, application of the sealant includes, as shown at 942I, brush coating a film of the sealant along the junction. In some examples, application of the sealant includes, as shown at 942J, laying a bead of the sealant. In some examples, the bead is lain subsequent to the brush coating. Accordingly, the bead may be lain over a film of sealant previously applied via brush coating. One advantage of the combined approach is that the brushing action helps to stir up particulates from abrasion (at 942E) that may remain on the junction even after cleaning (at 942F). Such particulates are thereby distributed into the bulk of the sealant, where they are less likely to compromise the quality of the seal than if left on the surface. Accordingly, when the sealant bead is subsequently applied, it is received onto a pristine surface, for reliable adhesion. In some examples the film may be allowed to fully or partially cure before the bead coating is enacted. In some examples, sealant application includes an intermediate deglossing step 942K between brush coating and bead coating, where, for example, a solvent-moistened cloth is wiped over the cured film prior to bead coating. In examples in which brush coating and bead coating are both used, the bead coating may be enacted by the same tool as the brush coating, or by a different tool. One or both of these steps may be controlled via an electronic process controller.
At 942L the junction is inspected after reinforcement. In some examples, inspection of the junction includes remotely inspecting an image of the junction. In some examples, inspection of the junction includes inspecting the quality of adhesion of the cured sealant to the junction via mechanical testing. Mechanical testing may be enacted using a mechanical-testing tool, such as tool 838.
This disclosure contemplates a scenario in which plural areas of incomplete or uneven bonding are located within a given conduit, and in which the various functions of abrading, cleaning, sealing, and inspecting the junction are performed iteratively over each of the areas. For example, after the sealant is applied, at 942H of method 940, the process flow returns to 942G, where the electronic process controller advances to the next area, continuing to receive output signal from the translation register and updating the position of the tool. In some examples, the area of incomplete or uneven bonding farthest from the conduit end through which the tool is inserted is sealed first. Thereafter the tool is backed out of the conduit, sealing the remaining areas as encountered. This strategy avoids a situation in which the tool has to be moved over uncured sealant. Method 940 also indicates iteration through plural areas for area location, abrasion, cleaning, and inspection steps. It will be noted, however, that a conduit may be cleaned all at once, in some examples.
No aspect of the foregoing drawings or description should be understood in a limiting sense, because numerous variations, extensions, and omissions are also envisaged. For instance, while tools having on-board drive mechanisms are emphasized above, a tool fixed to the end of a pushrod also falls within the spirit and scope of this disclosure. In such examples, the pushrod may be actuated via an electronic process controller located outside of the conduit, or actuated directly by a human operator. The tools illustrated in
This disclosure is presented by way of example. Components, process steps, and other elements that may be substantially the same in one or more of the figures are identified coordinately and described with minimal repetition. It will be noted, however, that elements identified coordinately may also differ to some degree. It will be further noted that the figures are schematic and generally not drawn to scale. Rather, the various drawing scales, aspect ratios, and numbers of components shown in the figures may be purposely distorted to make certain features or relationships easier to see.
It will be understood that the configurations and/or approaches described herein are exemplary in nature, and that these specific embodiments or examples are not to be considered in a limiting sense, because numerous variations are possible. The specific routines or processes described herein may represent one or more of any number of processing strategies. As such, various acts illustrated and/or described may be performed in the sequence illustrated and/or described, in other sequences, in parallel, or omitted. Likewise, the order of the above-described processes may be changed.
The subject matter of the present disclosure includes all novel and non-obvious combinations and sub-combinations of the various processes, systems and configurations, and other features, functions, acts, and/or properties disclosed herein, as well as any and all equivalents thereof.
