Patent Application
20190030842
The present disclosure relates generally to the field of composite structures and, more particularly, to systems, apparatus, and methods for forming and repairing composite structures.
Composite fuselage and nacelle structures may be subjected to impact damage in various ways: birds, airport service vehicles, equipment, maintenance, lighting strikes, etc. An effective and efficient repair is imperative in order to restore the structural integrity to the composite structure while minimizing aircraft downtime. Conventional approaches to composite structure repairs include two primary types of repair methods: bolted repairs and bonded repairs. While bolted repairs can be performed quickly, bolted repairs require the addition of bolt holes, which damage and weaken the composite structure. Bolted repairs are also aesthetically non-optimal, as they generally result in a visible patch. A bonded repair may be preferable for its aesthetically pleasing and near seamless integration into the composite structure. However, conventional approaches to bonded repairs are often more complex and difficult than performing bolted repairs. As such, despite the drawbacks discussed above, bolted repairs are often the default repair method due to their relatively simplicity and quick turnaround time.
The present disclosure may be embodied in an elastomeric bladder tool that comprises an elastomeric outer wall, an inner cavity at least partially defined by the elastomeric outer wall, and an embedded heating system embedded within the elastomeric outer wall.
In an embodiment, the embedded heating system comprises resistance wire embedded within the elastomeric outer wall.
In an embodiment, the embedded heating system distributes heat throughout the elastomeric outer wall and maintains flexibility of the elastomeric outer wall.
In an embodiment, the embedded heating system further comprises woven glass surrounding the resistance wire.
In an embodiment, the elastomeric bladder tool further comprises one or more raised edge seals positioned along and protruding from the elastomeric outer wall.
In an embodiment, the one or more raised edge seals comprise elastomer material of equal or lower durometer than the elastomeric outer wall.
In an embodiment, the elastomeric outer wall comprises at least one of: fluoroelastomer, silicone, butyl-rubber, or ethylene propylene diene monomer rubber (EPDM).
In an embodiment, the elastomeric outer wall comprises an outermost layer, and the outermost layer comprises an inert polymer to reduce friction during insertion or extraction of the elastomeric bladder tool from a composite structure.
In an embodiment, the elastomeric outer wall is in a collapsed state in normal atmospheric conditions, and the elastomeric outer wall can be expanded into an expanded state by applying positive pressure to the inner cavity.
In an embodiment, the elastomeric bladder tool further comprises an end fitting configured to allow gas or fluid to be inserted into and extracted from the internal cavity.
The present disclosure may also be embodied in a method in which an elastomeric bladder tool is positioned in a collapsed state proximate a repair area of a composite structure. The elastomeric bladder tool comprises an embedded heating system. The elastomeric bladder tool is expanded to an expanded state. In the expanded state, the elastomeric bladder tool provides support for one or more plies placed on the repair area of the composite structure. Heat is applied to the one or more plies using the embedded heating system.
In an embodiment, the elastomeric bladder tool is collapsed to the collapsed state, and the elastomeric bladder tool is extracted from the composite structure in the collapsed state.
In an embodiment, the elastomeric bladder tool comprises one or more raised edge seals positioned along and protruding from an outer surface of the elastomeric bladder tool.
In an embodiment, expanding the elastomeric bladder tool to the expanded state causes the one or more raised edge seals to create an air-tight seal around the repair area.
The present disclosure may also be embodied in a composite structure repair system comprising: a composite structure comprising a repair area to be repaired; one or more plies positioned on the repair area; an elastomeric bladder tool positioned proximate the one or more plies, the elastomeric bladder tool comprising an elastomeric outer wall, an inner cavity at least partially defined by the elastomeric outer wall, and an embedded heating system embedded within the elastomeric outer wall; a pressure regulator in communication with the inner cavity for alternating the elastomeric bladder tool between a collapsed state and an expanded state; and a temperature controller connected to the embedded heating system for controlling a temperature of the embedded heating system.
In an embodiment, in the expanded state, the elastomeric bladder tool provides support for the one or more plies.
In an embodiment, in the expanded state, the elastomeric bladder tool is configured to apply heat to an interior surface of the one or more plies using the embedded heating system.
In an embodiment, the elastomeric bladder tool further comprises one or more raised edge seals positioned along and protruding from the elastomeric outer wall.
In an embodiment, the one or more raised edge seals comprise elastomer material of equal or lower durometer than the elastomeric outer wall.
Although various combinations of limitations have been disclosed respecting each of the systems and methods described above, it should be appreciated that these do not constitute every limitation disclosed herein, nor do they constitute every possible combination of limitations. As such, it should be appreciated that additional limitations and different combinations of limitations presented within this disclosure remain within the scope of the disclosed invention.
These and other features and advantages of the invention should become more readily apparent from the detailed description of the preferred embodiments set forth below taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention.
The drawings are provided for purposes of illustration only and merely depict typical or example implementations. One skilled in the art will readily recognize from the following discussion that alternative embodiments of the structures and methods illustrated in the figures can be employed without departing from the principles of the disclosed technology described herein. These drawings are provided to facilitate the reader's understanding and shall not be considered limiting of the breadth, scope, or applicability of the disclosure. For clarity and ease of illustration, these drawings are not necessarily drawn to scale.
Composite fuselage and nacelle structures may be subjected to impact damage in various ways: birds, airport service vehicles, equipment, maintenance, lighting strikes, etc. An effective and efficient repair is imperative in order to restore the structural integrity to the composite structure while minimizing aircraft downtime. Conventional approaches to composite structure repairs include two primary types of repair methods: bolted repairs and bonded repairs.
In general, a bolted repair can provide a quick turnaround and substantially minimize aircraft downtime. Typically, in bolted repairs, a damaged area of a composite structure is assessed to determine the extent of the needed repair. A patch panel can be fabricated to bolt over the damaged area. Typically, patch panels are constructed from titanium or aluminum sheets. The repair area is prepared before the patch panel is installed. Cracks are typically drilled to prevent further crack propagation and panel bolt patterns are predrilled.
One advantage of a bolted repair, compared to conventional bonded repairs, is that the aircraft can be repaired easily in the field. One disadvantage of a bolted repair is that the damaged area on a composite structure is made larger and the composite structure is further weakened by drilling outside the damaged area. Furthermore, the additional bolt holes weaken the composite structure by introducing point stress concentrations. Another drawback to bolted repairs includes the fact that bolts and the patch panel affect the aerodynamic properties of the composite structure. This may be particularly important, for example, if the composite structure makes up a portion of an aircraft or other vehicle. In sum, bolted repairs are convenient because they can be performed quickly, but there are significant disadvantages in terms of structural integrity and aerodynamic performance.
A bonded repair is typically the most effective approach to repair a composite structure. Bonded repairs avoid additional damage to the composite structure and provide a superior surface finish. Rather than using a patch panel made of titanium or aluminum, a bonded repair can use a composite material that is similar or identical to the material in the composite structure. This ensures a better coefficient of thermal expansion and mechanical property matching to the repair area for more optimal long-term performance. Another advantage of the bonded repair is that the repair zone is kept minimal, since there is no need for fasteners. With bonded repairs, the aerodynamic properties of the composite structure are generally not materially compromised, since the repair area remains relatively flush with the original surface. Additionally, the finish of a bonded repair is more aesthetically appealing when compared to bolted repairs.
In bonded repairs, the edges of a repair area (e.g., a damaged area) of a composite structure can be sanded at a predetermined angle to increase the bonding area and allow better load transfer. Then, new uncured plies can be placed over the repair area and cured using known composite fabrication procedures. Conventional approaches to bonded repairs may utilize flat heating blankets and a vacuum bag system. A common issue with using flat heating blankets is that the edges of the flat heating blankets often do not reach adequate temperature and the blanket does not conform, for example, to stringers used to stiffen large composite structures (such as aircraft structures) near surface features such as radii or inside the stringers. Porosity and insufficient consolidation can occur at the radii. Another problem often arising with conventional approaches to bonded repairs is that the inner vacuum bag of the vacuum bag system can tear during extraction and Foreign Object Debris (FOD) can be trapped within the repair. This FOD must then be removed, which adds to repair time and cost.
Yet another disadvantage of conventional approaches to bonded repair is the complexity of the process, which often requires specially trained personnel and special equipment. Furthermore, preparing the repair area for repair can be meticulous and time consuming. As a result, bonded repairs can be significantly slower and more difficult than bolted repairs. Additionally, the surrounding composite structure around a repair area may have a limit for how long it can be heated without impacting its mechanical properties.
The presently disclosed technologies improve, simplify, and aid the bonded repair process. Various embodiments of the disclosed technologies can reduce the complexity of bonded repairs by generating a more uniform temperature and pressure distribution across a composite structure repair area, and can reduce porosity. Furthermore, various embodiments of the present disclosure allow for easier installation and extraction of elastomeric bladder tooling used in bonded repair, and can eliminate the problematic internal bag component from a bonded repair vacuum bag system. Various embodiments of the present disclosure can also enable repair of composite structures around trapped cavities. By removing these issues that commonly arise in conventional approaches to bonded repair of composite structures, the quality of the bonded repair can be improved and the process can be made more efficient and effective. Various aspects of the disclosed technologies are described in greater detail herein.
In an embodiment, the elastomeric bladder tool 100 is open on at least one end to allow for one or more gas or fluid connections. A collapsed elastomeric bladder tool 100 can be deployed into its active (or expanded) state by applying positive pressure to the interior of the elastomeric bladder tool 100 through an end fitting 108, as shown most clearly in
A common problem with conventional vented bladders is that uncured plies placed over a repair area of a composite structure may remain unstable. In some cases, vacuum pressure applied by a conventional vacuum bag system is not enough to support the uncured plies. With the presently disclosed technologies, the elastomeric bladder tool 100 can be collapsed to have a smaller cross-sectional area during insertion into a repair area and extraction from a repair area, and once the elastomeric bladder tool 100 is inserted into a composite structure, it can be expanded into its active state. By providing positive pressure to the elastomeric bladder tool 100 from inside the cavity, the elastomeric bladder tool 100, in its active, expanded state, can stabilize uncured plies during the curing process. Furthermore, heating elements 102 embedded into the elastomeric bladder tool 100 can be used to apply direct heat to a repair area from inside a composite structure, which was not possible with conventional heated blankets, which could only be laid over a repair area from outside the composite structure.
In the embodiment depicted in
The elastomeric bladder tool 100 can also include one or more raised edge seals 120 on an outer surface of the outer wall 104. In various embodiments, as will be described in greater detail below, the edge seals 120 can be used to eliminate the need for an interior vacuum bag. When the elastomeric bladder tool 100 is inserted into a repair area, and then is inflated to fill and support the repair area, the raised edge seals 120 can tightly seal off the repair area. In this way, the edge seals 120 can eliminate the need for an interior vacuum bag on an interior surface of the repair area. In an embodiment, the edge seal 120 comprises a protruding elastomer strip of equal or lower durometer than the rest of the outer wall 104.
In certain embodiments, the elastomeric bladder tool 100 can be inserted inside a cavity, such as the stringer 402, and placed directly under the repair area 404. As discussed above, the elastomeric bladder tool 100 can be in a collapsed state when inserted into the stringer 402. Positive pressure can be introduced to the elastomeric bladder tool 100 (e.g., via end fitting 108) to expand the elastomeric bladder tool into an expanded state. In the expanded state, the elastomeric bladder tool 100 can support uncured plies laid on the repair area 404 during layup. Heating elements embedded within the elastomeric bladder tool can be warmed in order to apply heat to an interior surface of the repair area 404 in order to more quickly and more effectively cure uncured plies laid on the repair area 404. Raised edge seals 120 allow the elastomeric bladder tool 100 to seal off the interior of the stringer to avoid the use of an inner vacuum bag during the curing process. After the outer vacuum bag system is in place with new uncured plies, the heating elements within the elastomeric bladder tool 100 can be activated to bring the system up to temperature.
The composite structure repair system 500 includes a vacuum connector 514 that is installed on the exterior bag 512 and connected to a vacuum gage 516. The vacuum gage 516 is connected to a two-way valve 518 and a vacuum pump 520. The vacuum pump 520 can be configured to evacuate air within the vacuum bag system 504 to ensure that the new plies 502 maintain contact with the damaged area 404 of the composite structure being repaired during the curing process. At one end, the elastomeric bladder tool 100 is connected to a pressure regulator 522 via an end fitting (e.g., end fitting 108 of
While various embodiments of the disclosed technology have been described above, it should be understood that they have been presented by way of example only, and not of limitation. Likewise, the various diagrams may depict an example structure or configuration for the disclosed technology, which is done to aid in understanding the features and functionality that can be included in the disclosed technology. The disclosed technology is not restricted to the illustrated example structures or configurations, but the desired features can be implemented using a variety of alternative structure and configurations. Indeed, it will be apparent to one of skill in the art how alternative functional, logical or physical partitioning and configurations can be implemented to implement the desired features of the technology disclosed herein. Additionally, with regard to flow diagrams, operational descriptions and method claims, the order in which the steps are presented herein shall not mandate that various embodiments be implemented to perform the recited functionality in the same order unless the context dictates otherwise.
Although the disclosed technology is described above in terms of various exemplary embodiments and implementations, it should be understood that the various features, aspects and functionality described in one or more of the individual embodiments are not limited in their applicability to the particular embodiment with which they are described, but instead can be applied, alone or in various combinations, to one or more of the other embodiments of the disclosed technology, whether or not such embodiments are described and whether or not such features are presented as being a part of a described embodiment. Thus, the breadth and scope of the technology disclosed herein should not be limited by any of the above-described exemplary embodiments.
Terms and phrases used in this document, and variations thereof, unless otherwise expressly stated, should be construed as open ended as opposed to limiting. As examples of the foregoing: the term “including” should be read as meaning “including, without limitation” or the like; the term “example” is used to provide exemplary instances of the item in discussion, not an exhaustive or limiting list thereof; the terms “a” or “an” should be read as meaning “at least one,” “one or more” or the like; and adjectives such as “conventional,” “traditional,” “normal,” “standard,” “known” and terms of similar meaning should not be construed as limiting the item described to a given time period or to an item available as of a given time, but instead should be read to encompass conventional, traditional, normal, or standard technologies that may be available or known now or at any time in the future. Likewise, where this document refers to technologies that would be apparent or known to one of ordinary skill in the art, such technologies encompass those apparent or known to the skilled artisan now or at any time in the future.
The presence of broadening words and phrases such as “one or more,” “at least,” “but not limited to” or other like phrases in some instances shall not be read to mean that the narrower case is intended or required in instances where such broadening phrases may be absent. Additionally, various embodiments set forth herein are described in terms of exemplary block diagrams, flow charts and other illustrations. As will become apparent to one of ordinary skill in the art after reading this document, the illustrated embodiments and their various alternatives can be implemented without confinement to the illustrated examples. For example, block diagrams and their accompanying description should not be construed as mandating a particular structure or configuration.
Although the disclosure has been presented with reference only to the presently preferred embodiments, those of ordinary skill in the art will appreciate that various modifications can be made without departing from this disclosure. As such, the disclosure is defined only by the following claims and recited limitations.
The present application claims priority to U.S. Provisional Application No. 62/537,886, filed on Jul. 27, 2017, the entire contents of which are incorporated by reference as if fully set forth herein.
| Number | Date | Country | |
|---|---|---|---|
| 62537886 | Jul 2017 | US |
