Patent Application
20190061073
The present disclosure relates to lap joints, and more specifically, to methods of separating adhesively bonded lap joints.
Mechanical separation of two components that are adhesively bonded together generally is destructive to one or both components. For example, mechanically separating a sheath from an airfoil often damages both the sheath and the airfoil to such an extent that either the parts need extensive restoration in order to be salvaged or both parts are extensively damaged such that neither part is re-usable.
In various embodiments, the present disclosure provides a method of separating a lap joint assembly. The method includes positioning a fluid emitter relative to the lap joint assembly, wherein the lap joint assembly comprises an adhesive lap joint between a first component and a second component, according to various embodiments. The method further includes emitting a cryogenic fluid stream from the fluid emitter at the adhesive lap joint, according to various embodiments. Positioning the fluid emitter and emitting the cryogenic fluid stream may include orienting the fluid emitter such that an angle between the cryogenic fluid stream and the adhesive lap joint is less than 45 degrees.
In various embodiments, positioning the fluid emitter and emitting the cryogenic fluid stream include orienting the fluid emitter such that the angle between the cryogenic fluid stream and the adhesive lap joint is less than 30 degrees. In various embodiments, positioning the fluid emitter and emitting the cryogenic fluid stream include orienting the fluid emitter such that the angle between the cryogenic fluid stream and the adhesive lap joint is less than 20 degrees. In various embodiments, the method also includes positioning a deflector relative to the lap joint assembly such that the cryogenic fluid stream diverts off the deflector before impinging the adhesive lap joint. In various embodiments, the deflector has a curved deflection surface to facilitate focusing the cryogenic fluid stream at the adhesive lap joint. In various embodiments, the cryogenic fluid stream comprises liquid nitrogen. In various embodiments, the first component is an airfoil body and the second component is a sheath disposed along a leading edge of the airfoil body.
Also disclosed herein, according to various embodiments, is a method of repairing an airfoil assembly. The method may include positioning a fluid emitter relative to an airfoil body, wherein a sheath is adhesively bonded to the airfoil body via an adhesive lap joint. The method may also include emitting a cryogenic fluid stream from the fluid emitter at the adhesive lap joint. Still further, the method may include, in response to removing at least a portion of adhesive material from the adhesive lap joint via the emitting the cryogenic fluid stream, mechanically removing the sheath from the airfoil body. Also, the method may include, in response to removing the sheath from the airfoil body, adhesively bonding a replacement sheath to the airfoil body.
The foregoing features and elements may be combined in various combinations without exclusivity, unless expressly indicated herein otherwise. These features and elements as well as the operation of the disclosed embodiments will become more apparent in light of the following description and accompanying drawings.
The subject matter of the present disclosure is particularly pointed out and distinctly claimed in the concluding portion of the specification. A more complete understanding of the present disclosure, however, may best be obtained by referring to the detailed description and claims when considered in connection with the drawing figures, wherein like numerals denote like elements.
The detailed description of exemplary embodiments herein makes reference to the accompanying drawings, which show exemplary embodiments by way of illustration. While these exemplary embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosure, it should be understood that other embodiments may be realized and that logical changes and adaptations in design and construction may be made in accordance with this disclosure and the teachings herein without departing from the spirit and scope of the disclosure. Thus, the detailed description herein is presented for purposes of illustration only and not of limitation.
There are various reasons why nondestructively separating two components that have been joined together via an adhesive lap joint would be beneficial. For example, if the components were improperly aligned during assembly or if the adhesive didn't properly bond to the components, it may be desirable to separate the two components with at least one of the components remaining sufficiently intact for re-use. Accordingly, disclosed herein, is a non-destructive method for separating adhesively bonded lap joints that tends to preserve at least one of the two bonded components undamaged (or with minimal damage) so that the undamaged component can be re-used/re-deployed, according to various embodiments. For example, the method(s) described herein may be utilized to separate a sheath from an airfoil body, in response to a manufacturing defect or damage occurring during use that allows for the airfoil body to be re-used. While numerous details are included herein pertaining to separating an adhesive lap joint between a sheath and an airfoil body of a gas turbine engine, the scope of the present disclosure is not limited to airfoils of gas turbine engines. Thus, the separating method provided herein may be utilized with a variety of adhesively bonded joint assemblies.
In various embodiments and with reference to
Gas turbine engine 20 may generally comprise a low speed spool 30 and a high speed spool 32 mounted for rotation about an engine central longitudinal axis A-A′ relative to an engine static structure 36 or engine case via several bearing systems 38, 38-1, and 38-2. Engine central longitudinal axis A-A′ is oriented in the z direction (axial direction) on the provided xyz axis. The y direction on the provided xyz axis refers to radial directions and the x direction on the provided xyz axis refers to the circumferential direction. It should be understood that various bearing systems 38 at various locations may alternatively or additionally be provided, including for example, bearing system 38, bearing system 38-1, and bearing system 38-2.
Low speed spool 30 may generally comprise an inner shaft 40 that interconnects a fan 42, a low pressure compressor 44 and a low pressure turbine 46. Inner shaft 40 may be connected to fan 42 through a geared architecture 48 that can drive fan 42 at a lower speed than low speed spool 30. Geared architecture 48 may comprise a gear assembly 60 enclosed within a gear housing 62. Gear assembly 60 couples inner shaft 40 to a rotating fan structure. High speed spool 32 may comprise an outer shaft 50 that interconnects a high pressure compressor 52 and high pressure turbine 54.
A combustor 56 may be located between high pressure compressor 52 and high pressure turbine 54. The combustor section 26 may have an annular wall assembly having inner and outer shells that support respective inner and outer heat shielding liners. The heat shield liners may include a plurality of combustor panels that collectively define the annular combustion chamber of the combustor 56. An annular cooling cavity is defined between the respective shells and combustor panels for supplying cooling air. Impingement holes are located in the shell to supply the cooling air from an outer air plenum and into the annular cooling cavity.
A mid-turbine frame 57 of engine static structure 36 may be located generally between high pressure turbine 54 and low pressure turbine 46. Mid-turbine frame 57 may support one or more bearing systems 38 in turbine section 28. Inner shaft 40 and outer shaft 50 may be concentric and rotate via bearing systems 38 about the engine central longitudinal axis A-A′, which is collinear with their longitudinal axes. As used herein, a “high pressure” compressor or turbine experiences a higher pressure than a corresponding “low pressure” compressor or turbine.
The core airflow C may be compressed by low pressure compressor 44 and then high pressure compressor 52, mixed and burned with fuel in combustor 56, then expanded over high pressure turbine 54 and low pressure turbine 46. Turbines 46, 54 rotationally drive the respective low speed spool 30 and high speed spool 32 in response to the expansion.
In various embodiments, geared architecture 48 may be an epicyclic gear train, such as a star gear system (sun gear in meshing engagement with a plurality of star gears supported by a carrier and in meshing engagement with a ring gear) or other gear system. Geared architecture 48 may have a gear reduction ratio of greater than about 2.3 and low pressure turbine 46 may have a pressure ratio that is greater than about five (5). In various embodiments, the bypass ratio of gas turbine engine 20 is greater than about ten (10:1). In various embodiments, the diameter of fan 42 may be significantly larger than that of the low pressure compressor 44, and the low pressure turbine 46 may have a pressure ratio that is greater than about five (5:1). Low pressure turbine 46 pressure ratio may be measured prior to inlet of low pressure turbine 46 as related to the pressure at the outlet of low pressure turbine 46 prior to an exhaust nozzle. It should be understood, however, that the above parameters are exemplary of various embodiments of a suitable geared architecture engine and that the present disclosure contemplates other gas turbine engines including direct drive turbofans. A gas turbine engine may comprise an industrial gas turbine (IGT) or a geared aircraft engine, such as a geared turbofan, or non-geared aircraft engine, such as a turbofan, or may comprise any gas turbine engine as desired.
Airfoils, such as rotor blades and stator vanes, are often utilized in various sections of gas turbine engines to direct, condition, and affect the flow of fluids (e.g., air and/or combustion gases) through the gas turbine engine. Some airfoils, such as fan blades, often include one or more sheaths or cover panels that are bonded to the airfoil body. If the bonded joints in such airfoils were to be compromised, either due to an identified manufacturing defect or due to damage that occurs during use (e.g., a bird strike), the provided method allows for the adhesive lap joint to be separated and for at least the airfoil body to be re-used/repaired.
With reference to
It will be noted that airfoils for gas turbine engines may be provided in the variety of sizes, shapes and geometries. Accordingly, the airfoil assembly 100 of the present disclosure is not limited to the specific geometry, size, and shape shown in the figures. Further, as mentioned above, the disclosed airfoil assembly 100 is not necessarily limited to the fan section 22 of a gas turbine engine 20, but instead may be implemented in other sections of the gas turbine engine 20 and/or may be adapted for use in other types of jet engines, propellers, rotors, etc. In various embodiments, the body 110 of the airfoil assembly 100 may be fabricated from a metallic material, such as a metal and/or a metal alloy. In various embodiments, for example, the body 110 of the airfoil assembly 100 may be fabricated from aluminum, an aluminum alloy, titanium, and/or a titanium alloy, among other suitable metallic materials.
With reference to
In various embodiments, the body 110 of the airfoil assembly 100 may be made from a first metallic material and the sheath 120 may be made from a second metallic material. In various embodiments one or both of the body 110 and the sheath 120 may be made from composite materials. In various embodiments, a cover 130 may be attached to the airfoil body 110. In various embodiments, the cover 130 may be fabricated from a composite material such as carbon fiber, fiber-reinforced polymer (e.g., fiber glass), para-aramid fiber, and/or aramid fiber. In various embodiments, the cover 130 may be fabricated from a fiber metal laminate (“FML”). For example, the cover 130 may include metal layers comprising titanium and/or a titanium alloy and the composite material layers in the FML may comprise carbon fiber, such as graphite fiber. An FML comprising titanium and/or a titanium alloy and graphite fiber is commonly known in the industry as “TiGr.” In various embodiments, in which an FML comprises metal layers comprising aluminum and/or an aluminum alloy, the composite material layers in the FML may comprise fiber-reinforced polymer (e.g., fiber glass), para-aramid fiber, and/or aramid fiber. An FML comprising aluminum and/or an aluminum alloy and fiber glass is commonly known by the industry standard designation of “GLARE.” Though FMLs described above include specific examples of metals, metal alloys, and/or composite materials, it would not be outside the scope of this disclosure to include any FML comprising any metal, metal alloy, and/or composite material, in any arrangement of layers.
In various embodiments, and with reference to
In various embodiments, and with reference to
In various embodiments, the cryogenic fluid stream 451 is substantially non-abrasive. Accordingly, the structural integrity of the components 401, 402 may be maintained because the cryogenic fluid stream 451 is not utilizing conventional solid particle abrasion to wear away the adhesive. For brittle adhesive materials, such as epoxy and phenolic adhesives, the fluid stream may be somewhat erosive via the fluid stream impacting the target area, creating fractures in the brittle adhesive until the area exfoliates. In various embodiments, debris does not build at the site of impact (which could insulate/shield the areas not yet damaged) because the fluid stream flushes away the exfoliated material. For both elastomeric adhesive materials and brittle adhesive materials, the components 401, 402 may be exposed to tensile forces, in addition to directing the cryogenic fluid stream at the adhesive lap joint 403. Because the lap joint 403 has higher shear strength than tensile strength, the integrity of the lap joint 403 may be diminished.
In various embodiments, in response to chilling the adhesive via the cryogenic fluid stream, the resilience and/or adhesion properties of the adhesive material is diminished so that it fails more preferentially. In various embodiments, many adhesive materials go thru one or more ductile to brittle transitions in response to being exposed to the temperatures of the cryogenic fluid stream 451. In various embodiments, thermally induced strain facilitates separation of the lap joint assembly 400. For example, the chilling of the lap joint assembly 400 produces thermal strains, both between the adhesive and the components 401, 402 and within the adhesive material itself. In various embodiments, the more-brittle adhesive is less able to sustain those strains and thus separation is facilitated. In various embodiments, in response to injecting the cryogenic fluid stream 451 into the tight space of the lap joint 403, the expansion associated with the transition from a liquid to a vapor also induces extra opening loads on the joint (in flatwise and in peel) that further facilitate the separation.
As mentioned above, the procedure of the present disclosure may also be utilized with GLARE and TIGR materials. While the fibers in these systems may be not be as easily fractured, the incidence angle 452, as described further below, can be selected in order to minimize/reduce undercutting of the fibers. The pressure and/or intensity of the cryogenic fluid stream 451 may also be reduced versus those utilized with metallic assemblies. In various embodiments, in response to the fibers loosening, the fibers contribution as a break wall will be reduced or eliminated, causing the material to exfoliate.
In various embodiments, the pressure of the cryogenic fluid is between about 12,000 psi (80 megapascals) and about 52,000 psi (360 megapascals). In various embodiments, the pressure of the cryogenic fluid is about 20,000 psi (140 megapascals). As used in this context only, the term “about” refers to plus or minus 10% of the indicated value. In various embodiments, a nozzle having a single orifice or multiple orifices may be utilized. The nozzle may be non-rotating or may be configured to rotate up to 80 rotations per minute. The nozzle may be positioned about 0.10 inches to about 0.75 inches away from the lap joint. As used in this context only, the term “about” refers to plus or minus 5% of the indicated value.
In various embodiments, the fluid emitter 450 is oriented and positioned so as to direct the cryogenic fluid stream 451 at a shallow angle 452 relative to the adhesive lap joint 403. The adhesive lap joint 403, according to various embodiments, has a joint axis 455 that extends centrally through the adhesive layer and parallel to the respective surfaces of the adjoining components 401, 402. The angle 452 of the cryogenic fluid stream 451 emitted from the fluid emitter 450 is relative to the joint axis 455, according to various embodiments. Accordingly, when the fluid emitter 450 is utilized to separate the sheath 120 from the airfoil body 110 (with momentary reference to
In various embodiments, the angle 452 is less than 45 degrees. In various embodiments, the angle 452 is less than 30 degrees. In various embodiments, the angle 452 is less than 20 degrees. In various embodiments, and with reference to
In various embodiments, and with reference to
In various embodiments, and with reference to
In various embodiments, and with reference to
Benefits, other advantages, and solutions to problems have been described herein with regard to specific embodiments. Furthermore, the connecting lines shown in the various figures contained herein are intended to represent exemplary functional relationships and/or physical couplings between the various elements. It should be noted that many alternative or additional functional relationships or physical connections may be present in a practical system. However, the benefits, advantages, solutions to problems, and any elements that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as critical, required, or essential features or elements of the disclosure.
The scope of the disclosure is accordingly to be limited by nothing other than the appended claims, in which reference to an element in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more.” It is to be understood that unless specifically stated otherwise, references to “a,” “an,” and/or “the” may include one or more than one and that reference to an item in the singular may also include the item in the plural. All ranges and ratio limits disclosed herein may be combined.
Moreover, where a phrase similar to “at least one of A, B, and C” is used in the claims, it is intended that the phrase be interpreted to mean that A alone may be present in an embodiment, B alone may be present in an embodiment, C alone may be present in an embodiment, or that any combination of the elements A, B and C may be present in a single embodiment; for example, A and B, A and C, B and C, or A and B and C. Different cross-hatching is used throughout the figures to denote different parts but not necessarily to denote the same or different materials.
The steps recited in any of the method or process descriptions may be executed in any order and are not necessarily limited to the order presented. Furthermore, any reference to singular includes plural embodiments, and any reference to more than one component or step may include a singular embodiment or step. Elements and steps in the figures are illustrated for simplicity and clarity and have not necessarily been rendered according to any particular sequence. For example, steps that may be performed concurrently or in different order are illustrated in the figures to help to improve understanding of embodiments of the present disclosure.
Any reference to attached, fixed, connected or the like may include permanent, removable, temporary, partial, full and/or any other possible attachment option. Additionally, any reference to without contact (or similar phrases) may also include reduced contact or minimal contact. Surface shading lines may be used throughout the figures to denote different parts or areas but not necessarily to denote the same or different materials. In some cases, reference coordinates may be specific to each figure.
Systems, methods and apparatus are provided herein. In the detailed description herein, references to “one embodiment,” “an embodiment,” “various embodiments,” etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it may be within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described. After reading the description, it will be apparent to one skilled in the relevant art(s) how to implement the disclosure in alternative embodiments.
Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims. No claim element is intended to invoke 35 U.S.C. 112(f) unless the element is expressly recited using the phrase “means for.” As used herein, the terms “comprises,” “comprising,” or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
