GB2453933A - Aircraft leading edge ice protection system comprising a thermoplastic heater mat - Google Patents
Aircraft leading edge ice protection system comprising a thermoplastic heater mat Download PDFInfo
- Publication number
- GB2453933A GB2453933A GB0720416A GB0720416A GB2453933A GB 2453933 A GB2453933 A GB 2453933A GB 0720416 A GB0720416 A GB 0720416A GB 0720416 A GB0720416 A GB 0720416A GB 2453933 A GB2453933 A GB 2453933A
- Authority
- GB
- United Kingdom
- Prior art keywords
- leading edge
- layer
- thermoplastic
- heater element
- aircraft
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
- 229920001169 thermoplastic Polymers 0.000 title claims abstract description 98
- 239000004416 thermosoftening plastic Substances 0.000 title claims abstract description 98
- 238000010438 heat treatment Methods 0.000 claims abstract description 33
- 239000004696 Poly ether ether ketone Substances 0.000 claims abstract description 24
- 229920002530 polyetherether ketone Polymers 0.000 claims abstract description 24
- 230000003019 stabilising effect Effects 0.000 claims abstract description 20
- 239000012815 thermoplastic material Substances 0.000 claims abstract description 17
- 229910052751 metal Inorganic materials 0.000 claims abstract description 16
- 239000002184 metal Substances 0.000 claims abstract description 16
- 239000011521 glass Substances 0.000 claims abstract description 14
- 238000000034 method Methods 0.000 claims description 42
- 230000008569 process Effects 0.000 claims description 18
- 238000004519 manufacturing process Methods 0.000 claims description 9
- 238000005507 spraying Methods 0.000 claims description 8
- 230000001419 dependent effect Effects 0.000 claims description 4
- 238000010791 quenching Methods 0.000 claims description 3
- 230000000171 quenching effect Effects 0.000 claims description 3
- 239000007921 spray Substances 0.000 claims 1
- 239000010410 layer Substances 0.000 description 101
- 239000000853 adhesive Substances 0.000 description 21
- 230000001070 adhesive effect Effects 0.000 description 21
- 239000000463 material Substances 0.000 description 8
- 239000003989 dielectric material Substances 0.000 description 7
- 238000002844 melting Methods 0.000 description 6
- 230000008018 melting Effects 0.000 description 6
- 238000011065 in-situ storage Methods 0.000 description 5
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 4
- 239000011248 coating agent Substances 0.000 description 4
- 238000000576 coating method Methods 0.000 description 4
- 238000001816 cooling Methods 0.000 description 4
- 229910052802 copper Inorganic materials 0.000 description 4
- 239000010949 copper Substances 0.000 description 4
- 239000002657 fibrous material Substances 0.000 description 4
- 230000006641 stabilisation Effects 0.000 description 4
- 238000000059 patterning Methods 0.000 description 3
- 239000004411 aluminium Substances 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 239000006185 dispersion Substances 0.000 description 2
- 239000004744 fabric Substances 0.000 description 2
- 239000000835 fiber Substances 0.000 description 2
- 238000010285 flame spraying Methods 0.000 description 2
- 230000009477 glass transition Effects 0.000 description 2
- 239000000155 melt Substances 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 239000003381 stabilizer Substances 0.000 description 2
- 230000007704 transition Effects 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 239000007767 bonding agent Substances 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000003822 epoxy resin Substances 0.000 description 1
- 238000005530 etching Methods 0.000 description 1
- 238000009472 formulation Methods 0.000 description 1
- 238000007710 freezing Methods 0.000 description 1
- 230000008014 freezing Effects 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 230000000873 masking effect Effects 0.000 description 1
- 230000005012 migration Effects 0.000 description 1
- 238000013508 migration Methods 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 238000007747 plating Methods 0.000 description 1
- 229920001643 poly(ether ketone) Polymers 0.000 description 1
- 229920001660 poly(etherketone-etherketoneketone) Polymers 0.000 description 1
- 229920001652 poly(etherketoneketone) Polymers 0.000 description 1
- 229920003223 poly(pyromellitimide-1,4-diphenyl ether) Polymers 0.000 description 1
- 229920000647 polyepoxide Polymers 0.000 description 1
- 229920001470 polyketone Polymers 0.000 description 1
- 239000011241 protective layer Substances 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B64—AIRCRAFT; AVIATION; COSMONAUTICS
- B64F—GROUND OR AIRCRAFT-CARRIER-DECK INSTALLATIONS SPECIALLY ADAPTED FOR USE IN CONNECTION WITH AIRCRAFT; DESIGNING, MANUFACTURING, ASSEMBLING, CLEANING, MAINTAINING OR REPAIRING AIRCRAFT, NOT OTHERWISE PROVIDED FOR; HANDLING, TRANSPORTING, TESTING OR INSPECTING AIRCRAFT COMPONENTS, NOT OTHERWISE PROVIDED FOR
- B64F5/00—Designing, manufacturing, assembling, cleaning, maintaining or repairing aircraft, not otherwise provided for; Handling, transporting, testing or inspecting aircraft components, not otherwise provided for
- B64F5/30—Cleaning aircraft
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B64—AIRCRAFT; AVIATION; COSMONAUTICS
- B64D—EQUIPMENT FOR FITTING IN OR TO AIRCRAFT; FLIGHT SUITS; PARACHUTES; ARRANGEMENT OR MOUNTING OF POWER PLANTS OR PROPULSION TRANSMISSIONS IN AIRCRAFT
- B64D15/00—De-icing or preventing icing on exterior surfaces of aircraft
- B64D15/12—De-icing or preventing icing on exterior surfaces of aircraft by electric heating
-
- B64F5/0018—
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B3/00—Ohmic-resistance heating
- H05B3/20—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater
- H05B3/22—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater non-flexible
- H05B3/28—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater non-flexible heating conductor embedded in insulating material
- H05B3/286—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater non-flexible heating conductor embedded in insulating material the insulating material being an organic material, e.g. plastic
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B2214/00—Aspects relating to resistive heating, induction heating and heating using microwaves, covered by groups H05B3/00, H05B6/00
- H05B2214/02—Heaters specially designed for de-icing or protection against icing
Landscapes
- Engineering & Computer Science (AREA)
- Aviation & Aerospace Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Transportation (AREA)
- Resistance Heating (AREA)
- Surface Heating Bodies (AREA)
Abstract
A thermoelectric heater mat 10 comprising an electrically resistive heater element 22 embedded in a thermoplastic layer 16 suitable for use as an aircraft leading edge ice protection system. The heater element 22 may be a sprayed metal layer and the thermoplastic layer 16 may be polyetheretherketone. There may be metallic terminal leads 14 connected to the heater element 22 and these may be partially embedded in the thermoplastic 16. The heater element 22 may be located in between two stabilising layers 21, which may be a glass. The heater mat 10 may have a double-curved shape to conform with the curved surface of an aircraft leading edge, which may be a wing. The heater mat 10 may be formed by applying the heater element 22 to a layer of thermoplastic material 28, adding a second layer of thermoplastic material 26 over the heater element 22, then heating the thermoplastic material, possibly to 360-380{C, to fuse the thermoplastic layers 26,28 to the heater element 22. The heater mat 10 may then be quenched, and the heating may be performed in a vacuum.
Description
HIGH PERFORMANCE HEATER MAT
BACKGROUND OF THE INVENTION
This invention relates to a heater mat and a method of making a heater mat.
Known heater mats such as those that can be used as part of a dc-icing system for a leading edge of an aircraft include a thermoelectric heater element and one or more
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layers of a dielectric material such as Kaptori. The dielectric protects the thermoelectric jo heater element and can serve to electrically insulate it from a metallic surface (such as an inner surface of an aircraft leading edge) to which the heater mat is to be applied.
Heater mats of this kind suffer from a number of problems.
A first problem is that dielectric materials hitherto used in heater mats have limited operating temperatures. The maximum operating temperatures of hitherto used dielectrics limits the amount of heating power known heater mats can produce.
Additionally, the limited temperatures that hitherto used dielectrics limits can withstand exacerbate problems associated with the development of "hot spots" in a heater mat (for example due to internal short circuits or other failures), potentially leading to catastrophic failure.
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Another problem is that the condition of some dielectric materials such as Kapton can deteriorate over time. This can lead to failure of the heater mat on exposure of the thermoelectric heater clement to moisture, and/or can lead to short circuiting of the thermoelectric heater element on a metallic surface to which the heater mat is applied.
This invention has been made in consideration of at least some of the problems indicated above.
SUMMARY OF THE INVENTION
Particular and preferred aspects of the invention are set out in the accompanying independent and dependent claims. Combinations of features from the dependent claims may be combined with features of the independent claims as appropriate and not merely as explicitly set out in the claims.
According to an aspect of the invention, there can be provided an aircraft leading edge ice protection system. The system includes a thermoelectric heater mat. The heater mat includes an electrically resistive heater element embedded in a thermoplastic layer.
According to an aspect of the invention, there can be provided a method of making an aircraft leading edge ice protection system. The method comprises making a heater mat by embedding an electrically resistive heater element in a thermoplastic layer.
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The thermoplastic layer can comprise Polyetheretherketone (PEEK).
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Thermoplastics such as PEEK have excellent mechanical properties that make them resilient against the kinds of deterioration that can çfet the kinds of dielectrics hitherto used in heater mats. Thermoplastics such as PEEK can also withstand higher temperatures than the hitherto employed dielectric materials, allowing heater mats according to an embodiment of the invention to output more heating power than known heater mats.
The electrically resistive heater element can be conveniently formed using a metal spraying process.
Metallic terminal leads (e.g. copper terminal leads) can he connected to the electrically resistive heater element and then embedded in the thermoplastic layer along with the electrically resistive heater element.
The heater mat can further comprise a stabilising layer embedded in the thermoplastic layer. This can improve the stability of for example, a metal sprayed electrically resistive heater element and of the thermoplastic during the heating process.
In one example, the heater element can be sprayed directly onto the stabilising layer using the metal spraying process described above.
In some embodiments, more than one such stabilising layer can be provided. In one embodiment, the heater element can be located in between two stabilising layers.
The stab ilising layer can, for example, comprise a glass. I0
The heater mat can be provided with a double-curved shape to conform with a corresponding double-curved surface of an aircraft leading edge component to which the heater mat is to be applied. This double curved shape can be achieved using a mould. In another example, the appropriate double-curved shape can be achieved by making the i5 heater mat "in-situ" on the double-curved surface of an aircraft leading edge component.
An example of a method of making the heater mat can include applying the electrically resistive heater element to a first layer of thermoplastic material; placing a second layer of thermoplastic material over the electrically resistive heater element; and applying heat to fuse the thermoplastic material with the electrically resistive heater element. In particular, the thermoplastic material and the electrically resistive heater element can be heated to a temperature in the range 36O38O0 C. Following heating, the heater mat can be quenched (rapidly cooled), to ensure that the thermoplastic retains a glassy internal structure.
The heating can be performed in a vacuum to prevent oxidisation. Where a mould is used (whereby air is excluded), it may not be necessary to apply a vacuum.
According to a further aspect of the invention, there can be provided an aircraft leading edge component comprising an aircraft leading edge ice protection system of the --4 kind described above. The aircraft leading edge component may, for example, comprise an aircraft wing.
According to another aspect of the invention, there can be provided an aircraft comprising an aircraft leading edge component of the kind described above.
BRIEF DESCRIPTION OF THE DRAWINGS
For a better understanding of the invention and to show how the same may be carried into effect reference is now made by way of example only to the accompanying drawings in which like reference signs relate to like elements and in which: Figures I and 2 show different views of an example of a heater mat in accordance with an embodiment of the invention; Figure 3 illustrates an example of a process for making a heater mat in accordance with an embodiment of the invention; Figures 4 and 5 show examples of a heater mat incorporating an adhesive receiving layer in accordance with an embodiment of the invention; Figure 6 illustrates an example of the use of a heater mat as a bonding means in accordance with an embodiment of the invention; is Figure 7 schematically shows an example of a wing slat comprising a plurality of supporting ribs attached a skin using a heater mat in accordance with an embodiment of the invention; Figure 8 shows an example of a double curved object with a heater mat applied thereto in accordance with an embodiment of the invention; and Figure 9 shows an example of the manufacture of a double curved heater mat in accordance with an embodiment of the invention.
While the invention is susceptible to various modifications and alternative forms, specific embodiments are shown by way of example in the drawings and are herein described in detail. It should be understood, however, that drawings and detailed description thereto are not intended to limit the invention to the particular form disclosed, but on the contrary, the invention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the present invention as defined by the appended claims.
DESCRIPTION OF PARTICULAR EMBODIMENTS
Particular embodiments will now be described by way of example only in the following with reference to the accompanying drawings.
According to an embodiment of this invention, there can be provided an aircraft leading edge ice protection system. The system includes thermoelectric heater mat that has a thermoplastic layer, within which is embedded an electrically resistive heater element. Embodiments of this invention also provide methods of making such a heater mat.
Thermoplastics are characterised by their material properties as a function of temperature. In particular, thermoplastic materials are plastic (deformable) in a temperature between an upper transition temperature Tm and a lower transition temperature T8. Above i'm, thermoplastic materials melt to form a liquid. Below T they enter a brittle, glassy state. In the temperature range between T and Tm, thermoplastics typically include a mixture of amorphous and crystalline regions. It is the amorphous regions that contribute to the elasticity/deformability of a thermoplastic in this phase.
It should be noted that T and Tm may not be well defined in practice, and freezing to the glassy state below T and melting above Tm may actually take place over a temperature range or window centred on T8 and Tm, respectively.
As described herein, thermoplastic materials exhibit good mechanical qualities and can operate at relatively high temperatures, due to their high melting points.
Thermoplastics that may be used in accordance with an embodiment of this
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invention include polyarylketones such as PEEK, PEK, PEKEKK and PEKK. Other examples of suitable thermoplastics include polyarylsulphones and polyarylim ides. -7
While, according to an embodiment of the invention, thermoplastics have been found to constitute a significant improvement on the kinds of material previously used, the mechanical resilience and high temperature performance of the thermoplastic
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Polyetheretherketone (PEEK, and also known as polyketone) makes it particularly suitable for use in a heater mat of the kind described herein.
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PEEK has a melting point Tm 350°C, which allows it to be used in heater mats that operate at relatively high temperatures. The typical operating temperature of a thermoelectric heater mat may be of the order of 300 C. Nevertheless, under some operating conditions (such as where short burst of heat are apIi), the upper operating temperature may be as high as 2600 C or more. Unusually, PEEK has two glass transition temperatures (Tg RLI3-lSO°C; T 260-290°C), depending on the cure cycle and formulation of the PEEK.
Due to the provision of a thermoplastic layer, a heater mat according to an embodiment of this invention is more mechanically robust than known heater mats. A heater mat according to an embodiment of the invention can also provide greater heating power than known heater mats due to the high temperature capability of thermoplastics such as PEEK.
According to an embodiment of the invention, it has been found that the combination of a high through thickness strength, a high Young's modulus (E 3700 MPa), a high tensile sFtth (a 90 MPa), a high melting point (Tm 350°C) and good wear resistance of PEEK make it particularly useful in the context of heater mats for ice protection systems for aircraft leading edges. .Iescribed below, the high through thickness strength of thermoplastics such as PEEK can allow the use of a heater mat according to an embodiment of the invention to be used to bond together structural, load bearing components (in particular, a supporting rib and a skin) of an aircraft leading edge.
Figures 1 and 2 show a top view and a side view (respectively) of an example of a heater mat 10 in accordance with an embodiment of the invention.
Heater mats of this kind find particular application in the field of ice protection systems for aircraft, although other uses are envisaged. When used as part of an ice protection system for an aircraft, a heater mat according to an embodiment of the invention can be attached (e.g. fused or adhered) to an inner surface of a leading edge component of the aircraft. Heat produced by the heater mat is transferred to the leading edge, thereby preventing a build up of ice which would otherwise degrade the aerodynamic performance of the leading edge.
The example heater mat 10 shown in Figure I includes an electrically resistive heater element 12. The heater element 12 may typically comprise a layer of electrically resistive material, such as a metal. In use, an electric current is passed through the heater element 12 to produce Joule heating. The heater element 12 can be made from any suitable electrically resistive material, typically a metal such as copper or aluminium. A is typical thickness of the heater element can be approximately 0.1 mm in the case of a sprayed metal heater mat (see below). Other kinds of heater element (for example an element manufactured by plating) may be as thin as 0.001 mm..
In this example, the heater element 12 is patterned in a series of interconnected strips, forming a current path. In other examples, a different patterning can be selected in accordance with design requirements. Alternatively, the patterning may be omitted.
The electrically resistive heater element 12 is embedded in a thermoplastic layer 16. As shown in Figure 2, in this example, the heater element 10 is completely embedded in the thermoplastic layer 16. In other examples, portions of the heater element 12 may not be entirely embedded within the thermoplastic layer 16. For example, a portion of the heater element 12 may protrude from the thermoplastic layer 16 to allow the attachment of current carrying leads. In the present example, separate current carrying leads 14 are provided to allow connection of a completely embedded heater element to an external current supply (not shown). As illustrated in Figures I and 2, the leads 14 in this example extend into the heater mat from a position at the periphery of the thermoplastic layer 16, to form terminations 15 with the heater element 12.
The leads can be made from, for example, copper or any other suitable conductor.
In this regard, it is noted that copper leads have been found to form an excellent electrical
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contact with a heater element embedded in a PEEK thermoplastic layer.
A heater mat of the kind described herein can be applied (e.g. adhered) to a surface to which heating power is to be supplied. An example of such a surface is an inner surface of an aircraft leading edge component (for example the leading edge of a wing slat or engine nacelle). The heater element 12 is electrically insulated from the surface (which may be metallic) by the thermoplastic layer 16.
Figure 3 illustrates an example of a process for making a heater mat 10 in accordance with an embodiment of the invention. In particular, the process illustrated in Figure 3 is suitable for construction of a heater mat 10 of the kind shown in Figure I. As shown in Figure 3, the heater mat 10 can be constructed by applying an electrically resistive heater element 22 to a first thermoplastic layer 28. The heater element 22 can be applied by a variety of methods, such as by a metal spraying process.
If required, the heater element 22 can be patterned as described above in relation to Figure I. The patterning can be achieved using a masking and/or etching process.
In one embodiment, one or more stabilising layers 21 can be provided in the heater mat 10. The purpose of the stabilising layer(s) 21 is to stabilise the material making up the heater element 22 so that when the assembly is, heated (as described below), migration of the heater element material is inhibited. It has also been found that the stabilising layer(s) can serve to enhance the thermal conductivity of the heater mat 10 during use.
In one example, the stabilising layer(s) 21 can comprise a glass. The glass can be added as a thin layer 2 I adjacent the heater element 22. Where more than one stabilising layer 21 is used, a layer of glass can be provided on either side of the heater element 22 as shown in the example of Figure 3.
In one embodiment, the heater element 22 can be applied (e.g. using a metal spraying process) to a layer of glass 2 I that is laid over the first thermoplastic layer 28.
A second layer of glass 21 can optionally be laid of the sprayed metal heater element 12 and then the second layer of thermoplastic 26 can be laid over the second layer of glass 21. The resulting thermoplastic/stabiliser/heater/stabiliser/thermoplastic sandwich structure can then be heated as described below.
It should be noted that the inclusion of a stabilising layer 21 such as a glass layer in the heater mat can reduce the flexibility of the mat. Accordingly, a thin layer of glass may be preferred, which can add stability during the manufacture process without having an overly adverse affect on the flexibility of the resulting heater mat.
As described above, leads 24 can be provided to form terminations 25 with the heater element 22. In some examples, the leads 24 can be formed using the same process as that used to provide the heater element itself. In the present example however, the leads 24 are provided as separate copper strips that are laid over the heater element 22 and the first thermoplastic layer 28.
Once the heater element 22 (and, if appropriate, the leads 24 and the stabilisation layer(s) 21) are in place, a second thermoplastic layer 26 can be applied to the assembly.
The assembly is then heated to fuse the first (28) and second (26) layers of thermoplastic together. The heating can be applied by, for example, laying the assembly including the first and second thermoplastic layers on a heating plate (e.g. a metallic plate). Typically, the assembly is heated to a temperature above the melting point of the thermoplastic (e.g. when PEEK is used, the heating temperature is typically in the region of 360-380°C), to allow the fusing process to take place. After heating, the assembly is cooled below the -11 glass transition temperature T8, whereby the thermoplastic enters a glassy state. In some examples, the cooling can take place rapidly (quenching), to prevent unwanted crystallisation of the thermoplastic.
Following heating, then cooling, the first (28) and second (26) layers of thermoplastic become fused together, forming a single thermoplastic layer (e.g. layer 16 in Figure I) within which the heater element 22 and optional leads 24 and stabilisation layer(s) 21 are embedded.
The heating described above can be performed in a vacuum to prevent unwanted oxidisation. In some examples, the process may be performed in an autoclave. In another example, the process can be performed by placing the assembly including the first (28) and second (26) layers of thermoplastic and the heater element 22 and leads 24 in a vacuum bag (not shown in Figure 3) prior to heating. The vacuum bag should be suitable for withstanding the desired heating temperature. For example, the vacuum bag can be an aluminium vacuum bag.
Accordingly, there has been described a process for making a heater mat of the kind shown in Figures I and 2.
As described herein, a heater mat 10 in accordance with an embodiment of the invention can be attached to a leading edge component of an aircraft, for example a wing slat. In accordance with an embodiment of the invention, the heater mat 10 includes a
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thermoplastic outer surface. Thermoplastics such as PEEK are generally difficult to attach to a surface using an adhesive, since adhesives do not typically form a good bond with a PEEK surface. In order to mitigate this problem, in accordance with an embodiment of this invention, the heater mat 10 can be provided with one or more adhesive receiving layers. Examples of this are now described in relation to Figures 4 and 5. -12
The example heater mats 10 shown in Figures 4 and 5 are generally similar to the heater mat shown in Figure I, but each example further includes an adhesive receiving layer 1 8 as described above. In accordance with an embodiment of the invention, the adhesive receiving layer(s) described herein can comprise a fibrous material. The fibrous material can be selected such that it can be effectively wetted by the thermoplastic of the thermoplastic layer. Examples of suitable fibrous materials include glass cloth, Kevl1M carbon fibre and S ceramic fibre.
In the example of Figure 4, the adhesive receiving layer 18 is partially embedded within the thermoplastic layer 16 of' the heater mat 10, and protrudes from surface of the heater mat 10. The protruding portion of the adhesive receiving layer 18 can thus receive an adhesive 20 (e.g. epoxy resin) for adhering the heater mat tO to a surface 30.
The adhesive receiving layer 18 can be added to the heater mat 10 during manufacture, by laying it over one of the layers of thermoplastic (e.g. the layer 26 or the layer 28 shown in Figure 3) prior to heating. During heating, the thermoplastic melts and partially receives the adhesive receiving layer 18, although a portion of the layer 18 is left to protrude from the surface of the heater mat JO as described above.
In the alternative example shown in Figure 5, an intermediate layer 19 is provided, for attaching the adhesive receiving layer 18 to the thermoplastic layer 16. The intermediate layer 19 typically comprises a material which forms a good bond with both the thermoplastic layer 16 and the adhesive receiving layer 18. By way of example, the intermediate layer 19 may comprise a different thermoplastic to the thermoplastic making up the layer 16. In particular, the thermoplastic of the intermediate layer 19 may comprise a thermoplastic that makes a better bond with a given adhesive than does ifM thermoplastic of the layer 16. In one such example, the layer 16 may comprise PEEK, while the intermediate layer 19 may comprise a polyarylsolphone.
In accordance with an embodiment of the invention, the heater mat 10 can be provided with more than one adhesive receiving layer. By way of example, an adhesive --13 receiving layer such as that described in relation to Figures 4 and 5 can be provided on both an upper and lower surface of the thermoplastic layer 16. This can allow the heater mat 10 to be adhered to the surface of an aircraft leading edge component while also allowing a further object (for example, further insulating/protective layers) to be adhered to the upper surface of the mat 10. In one example, one or more conducting/resistive layers can be adhered to the upper surface to form a damage/failure system. Such layers can be provided to detect electrical breakdown should the heater mat 10 suffer mechanical damage caused by outside influences (for example, mechanical failure of the structure it is attached to).
As an alternative to using an adhesive as described above, in accordance with an embodiment of the invention a heater mat comprising a thermoplastic layer can be attached to a surface by heating the thermoplastic above Tm, whereby the thermoplastic fuses to the surface. In some examples, the surface (which may typically be metallic) can be treated (e.g. roughened) beforehand, to improve the bond to the thermoplastic of the is heater mat.
It has been found that a bond formed in this manner, between the thermoplastic of the heater mat and the surface of a leading edge component, is extremely strong.
Moreover, thermo plastic has a high through thickness strength. In accordance with an embodiment of the invention, the thermoplastic layer of a heater mat can itself be used as a bonding agent, for assembling two or more parts of a leading edge structure.
The parts to be assembled may typically comprise a skin of the leading edge and a supporting member such as a rib (e.g. an aerodynamic cardinal or rib), longeron or stringer.
By way of example, the arrangement shown in Figure 6 allows the attachment of a supporting rib 40 to the inside surface of a leading edge 30 of an aircraft.
In the example shown in Figure 6, the heater mat 10 is interposed between the rib and the leading edge 30 to form the bond. The thermoplastic layer of the heater mat has been fused (by heating the thermoplastic above its melting point Tm) to both the rib 40 and the leading edge 30.
Bonds of this kind can, in some examples, replace the provision of conventional attachment means such as rivets. This has the additional advantage that no (typically metallic) rivets or such like are required to pass through a heater mat provided between the rib 40 and the leading edge 30, whereby possible short circuiting within the heater element is avoided.
Moreover, the use of a heater mat 10 to provide a bond as shown in Figure 6 allows heating to be applied directly to the portion of the leading edge 30 below the rib 40, even though it is covered by, for example, a flange 42 of the rib 40. In conventional arrangements, heater mats 10 have been provided over the flange 42, whereby heat produced by the heater mat is required to pass through the flange 42 before reaching the leading edge 30. Accordingly, the heating power produced in conventional arrangements is substantially reduced owing to the temperature gradient across the rib flange 42.
Figure 7 schematically shows a portion of an aircraft wing slat. The leading edge of the slat is provided with a plurality of spaced supporting ribs. In this example, the ribs include a plurality of cardinal ribs 70 and a plurality of aerodynamic ribs 72. The aerodynamic ribs 72 are spaced in between adjacent cardinal ribs 70. As can be seen from Figure 7, the ribs in conventional arrangements, which are typically provided with flanges for attachment as discussed above, may inhibit access to many portions of the leading edge 30 for the purposes of ice-protection by heating. However, by employing an arrangement of the kind described above in relation to Figure 6, this problem can be solved, while simultaneously providing strong and robust bonding of the ribs 70, 72 to the leading edge 30.
Leading edges structures in aircraft may typically comprise surfaces that are curved in more than one direction. To conform with the double-curved shape of a surface in an aircraft leading edge component, a heater mat according to an embodiment of the invention can also be provided with a double curved shape. This can allow an ice-protection system including one or more heater mats of the kind described herein to apply even and effective heating across the surface of the leading edge.
Figure 8 shows an example of a double curved object in conjunction with which a heater mat JO according to an embodiment of the invention can be used. The double curved surfacein this example is a portion of an aircraft wing slat 50. It is envisaged that heater mats according to this invention can be used with other kinds of object having a double curved surface. I0
As shown in Figure 8, a heater mat JO is applied to an inner surface 54 of the aircraft wing slat 50. With reference to the Cartesian axes shown in Figure 8, the surface 54 is curved around the x-axis and the z-axis (which extends from the plane of the page).
Accordingly, the surface 54 in this example is double curved.
In some examples, the heater mat 10 may be constructed in situ on the double curved surface. For example, the heater mat may be constructed by applying a first thermoplastic layer to the double curved surface, then applying the heater element to the first thermoplastic layer (optionally, the first thermoplastic layer may be heated to fuse it to the surface, prior to the application of the heater element), then applying a second thermoplastic layer and heating the assembly. It should be noted that these methods may also be used to make flat heater mats in situ.
The heater element may be applied using the methods described above (e.g. using a metal spraying process).
The thermoplastic layers may be applied in a number of ways. For example, each thermoplastic layer may be applied as a powder coating, which melts during the heating process. Alternative methods include flame spraying and dispersion coating.
As described above, during heating, the thermoplastic can fuse directly to the surface 54. As described above, the thermoplastic can be heated to a temperature in the range 360-380°C. On cooling (which may take place rapidly (quenching) as described above), the thermoplastic enters its glassy state, resulting in a double curved heater mat that follows the double curved shape of the surface 54.
In an alternative method, the heater mat can be constructed using a mould that corresponds to the intended shape. The moulded heater mat can then be applied to the double curved surface, using, br example, an adhesive. As described above in relation to Figures 4 and 5, one or more adhesive receiving layers can be provided (e.g. a fibrous material such as glass cloth) to receive the adhesive. Adhesive receiving layers can be used in situations where it is not practical to construct the heater mat in situ (e.g. because vacuum conditions may be required). An example of this is illustrated in Figure 9.
In Figure 9, a first layer of thermoplastic 28 is applied to a mould section 62 bearing a double curved surface that corresponds to the intended shape. A second layer of thermoplastic 26 is also applied to a mould section 60 bearing a double curved surface that corresponds to the intended shape. The thermoplastic layers can, for example, be applied using powder coating, flame spraying or dispersion coating as described above in relation to Figure 8.
A heater element 22 can then be applied to one of the thermoplastic layers (in this example, the second thermoplastic layer 26), and any desired connection leads and stabilisation layers can be put in place.
The two sections (60, 62) of the mould are then brought together as depicted by the arrows in Figure 9, and the assembly is heated to allow the thermoplastic layers to fuse. It is noted that when a mould is used in this fashion, no special provision need be made to apply a vacuum during heating, as the mould itself excludes air from contacting the thermoplastic.
Following cooling (which, again, may be rapid), the resulting heater mat, with its double curved shape can be removed from the mould and applied to the intended double curved surface as described above.
Whether the double curved heater mat is made in situ or is made using a mould, stabilisation layers can be included in much the same way as is described above in relation to Figure 3.
Accordingly there has been described a thermoelectric heater mat. The heater mat comprises an electrically resistive heater element that is embedded in a thermoplastic layer. There has also been described a method of making a thermoelectric heater mat.
The method comprises embedding an electrically resistive heater element in a
RTM
thermoplastic layer. The thermoplastic can comprise a Polyetheretherketone (PEEK) material.
Claims (29)
- I. An aircraft leading edge ice protection system, the system comprising: a thermoelectric heater mat comprising an electrically resistive heater element embedded in a thermoplastic layer.
- 2. The aircraft leading edge ice protection system of claim 1, wherein the thermoplastic layer comprises Polyetheretherketone (PEEK).
- 3. The aircraft leading edge ice protection system of any preceding claim, wherein the electrically resistive heater element comprises a sprayed metal layer.
- 4. The aircraft leading edge ice protection system of any preceding claim, wherein the heater mat comprises metallic terminal leads connected to the electrically Is resistive heater element, wherein the leads are at least partially embedded in the thermoplastic layer.
- 5. The aircraft leading edge ice protection system of any preceding claim, wherein the heater mat further comprises a stabilising layer embedded in the thermoplastic layer.
- 6. The aircraft leading edge ice protection system of claim 5, wherein the heater mat comprises first and second stabilising layers embedded in the thermoplastic layer, wherein the heater element is located in between the stabilising layers.
- 7. The aircraft leading edge ice protection system of claim 5 or claim 6, wherein the stabilising layer comprises a glass.
- 8. The aircraft leading edge ice protection system of any preceding claim, wherein the heater mat has double-curved shape to conform with a corresponding double-curved surface of an aircraft leading edge component to which the heater mat is to be applied.
- 9. An aircraft leading edge component comprising the aircraft leading edge ice protection system of any preceding claim.
- 10. The aircraft leading edge component of claim 8, wherein the component comprises a leading edge of an aircraft wing.
- II. An aircraft comprising the aircraft leading edge component of claim 9 or claim 10.
- 12. A method of making an aircraft leading edge ice protection system, the method comprising making a heater mat by: IS embedding an electrically resistive heater element in a thermoplastic layer.
- 13. The method of claim 12, wherein the thermoplastic layer comprisesRTMPolyetherethcrkctone (PEEK).
- 14. The method of claim 12 or claim 13, comprising connecting metallic terminal leads to the electrically resistive heater element and at least partially embedding the metallic terminal leads in the thermoplastic layer.
- 15. The method of any of claims 12 to 14, comprising adding a stabilising layer to the mat.
- 16. The method of any of claims 12 to 15, comprising forming the electrically resistive heater element by a metal spraying process.
- 17. The method of claim 16 when dependent on claim 15, the method comprising using the metal spraying process to spray metal onto the stabilising layer.-,-. 20
- 18. The method of claim 17, comprising placing a further stabilising layer over the heater element subsequent to performing said metal spraying process.
- 19. The method of claim 15 or any claim dependent thereon, where the or each stabilising layer comprises a glass.
- 20. The method of any of claims II to 19, comprising: applying the electrically resistive heater element to a first layer of thermoplastic material; placing a second layer of thermoplastic material over the electrically resistive heater element; and applying heat to fuse the thermoplastic material with the electrically resistive heater element.
- 21. The method of claim 20 comprising heating the thermoplastic material and the electrically resistive heater element to a temperature in the range 360-380° C.
- 22. The method of claim 20 or claim 21, further comprising quenching the heater mat following said heating.
- 23. The method of any of claims 20 to 22, wherein said heating is performed in a vacuum.
- 24. The method of any of claims 20 to 23 comprising using a mould to shape said first and second layers of thermoplastic material to have a double-curved shape that corresponds to a double-curved surface of an aircraft leading edge component to which the heater matt is to be applied.
- 25. The method of any of claims 20 to 23 comprising applying the first layer of thermoplastic material to a double curved surface of an aircraft leading edge component prior to applying the electrically resistive heater element to the first layer of thermoplastic material.
- 26. An aircraft leading edge ice protection system substantially as hereinbefore described with reference to the accompanying drawings.
- 27. An aircraft leading edge substantially as hereinbefore described with reference to the accompanying drawings.Ia
- 28. An aircraft substantially as hereinbefore described with reference to the accompanying drawings.
- 29. An method of making an aircraft leading edge ice protection system, the method being substantially as hereinbefore described with reference to the accompanying drawings.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB0720416A GB2453933A (en) | 2007-10-18 | 2007-10-18 | Aircraft leading edge ice protection system comprising a thermoplastic heater mat |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB0720416A GB2453933A (en) | 2007-10-18 | 2007-10-18 | Aircraft leading edge ice protection system comprising a thermoplastic heater mat |
Publications (2)
Publication Number | Publication Date |
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GB0720416D0 GB0720416D0 (en) | 2007-11-28 |
GB2453933A true GB2453933A (en) | 2009-04-29 |
Family
ID=38814074
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
GB0720416A Withdrawn GB2453933A (en) | 2007-10-18 | 2007-10-18 | Aircraft leading edge ice protection system comprising a thermoplastic heater mat |
Country Status (1)
Country | Link |
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GB (1) | GB2453933A (en) |
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WO2011092483A1 (en) * | 2010-01-29 | 2011-08-04 | Gkn Aerospace Services Limited | Electrothermal heater mat |
US9267715B2 (en) | 2012-02-03 | 2016-02-23 | Airbus Operations Gmbh | Icing protection system for an aircraft and method for operating an icing protection system |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
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CN114878201B (en) * | 2022-07-11 | 2022-10-28 | 中国飞机强度研究所 | Heat load test system suitable for aerospace plane curved surface appearance |
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WO2011092483A1 (en) * | 2010-01-29 | 2011-08-04 | Gkn Aerospace Services Limited | Electrothermal heater mat |
CN102822056A (en) * | 2010-01-29 | 2012-12-12 | 吉凯恩航空服务有限公司 | Electrothermal heater mat |
US8807483B2 (en) | 2010-01-29 | 2014-08-19 | Gkn Aerospace Services Limited | Electrothermal heater mat |
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US9267715B2 (en) | 2012-02-03 | 2016-02-23 | Airbus Operations Gmbh | Icing protection system for an aircraft and method for operating an icing protection system |
Also Published As
Publication number | Publication date |
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GB0720416D0 (en) | 2007-11-28 |
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