Air-ducting component with spread tow fabric

Abstract

In an air-ducting component (2) with a wall (16), which provides an airtight delimitation for an interior space (10) from an exterior space (18) surrounding the component (2), the wall (16) contains at least a first layer (20a) of a two-dimensionally extending prepreg material (22) comprising a fabric (24a,b) which is impregnated with a resin composition (26), wherein, in at least the first layer (20a), the fabric (24a,b) is a spread tow fabric (28), which contains respective spread bands (30) of fibres (32), wherein the bands (30) are woven together in a weave (34). In a method for producing the component (2), the spread tow fabric (24) is integrated as a fabric (24a) into the wall (16) in at least the first layer (20a). Use is made of a spread tow fabric (28) in the component (2) and / or the method.

Description

[0001] Air duct component with spread-tow fabric

[0002] The invention relates to a component designed to guide air from an air conditioning system of a passenger aircraft. In other words, it is an air ducting component that, as part of the aircraft's air conditioning system, transports air to or from the passengers / passenger cabin.

[0003] It is known in practice to manufacture such air duct components with a wall containing one or more layers of prepreg materials. After curing, the finished air duct components are then coated with a sealing varnish to ensure sufficient sealing of the wall against leaks or the passage of air through the wall. The required maximum permissible leakage value is 3 liters of air per minute per square meter.

[0004] The object of the invention is to propose improvements with regard to corresponding components.

[0005] The object is achieved by a component according to patent claim 1. Preferred or advantageous embodiments of the invention and other categories of invention emerge from the further claims, the following description and the attached figures.

[0006] The component is designed to guide air from an air conditioning system on a passenger aircraft.

[0007] The component contains an interior space. The interior space guides the air during operation of the component and is therefore designed for appropriate air flow. The component contains a wall. The wall forms an airtight boundary between the interior space and the surrounding exterior space. "Airtight" is understood here to mean that a permissible leakage value / leakage rate is not exceeded.

[0008] This indicates how much air flows / diffuses through the wall per unit of time. For example, the limit is a maximum of 3 liters of air per minute per square meter. The wall does not completely delimit the interior space, as at least two openings—at least one inlet and at least one outlet—must remain open for air to flow through the interior space or the component formed by the wall.

[0009] The wall contains at least a first layer of a planar prepreg material. Additional layers of prepreg material are optionally possible within the wall. In other words, the prepreg material is layered / sheeted / planar.

[0010] The prepreg material contains a correspondingly extensive fabric. The fabric is impregnated with a resin composition. Strictly speaking, "impregnated" describes a prefabrication or manufacturing state of the prepreg material, in this case a prepreg semi-finished product. In the finished component, the prepreg material is then processed in the usual way, e.g., by thermal treatment / curing of the resin composition, etc. Nevertheless, even then, the fabric is still permeated with or embedded in (cured) resin.

[0011] In at least the first layer, the fabric is a spread-tow fabric. The fabric contains spread tow tapes of fibers. This means that the tapes are formed by several fibers arranged parallel in a plane. This arrangement of the fibers is achieved in particular by a combing process of a bundle of fibers (tow). The tapes have several (at least two) opposite flat sides and, in particular, have a nearly rectangular cross-section. In other words, a fiber bundle is first formed from several fibers, and a combing process is used to align the fibers such that a tape is produced or formed.

[0012] The bands are woven together according to a weave. A weave refers to the systematic interlacing of the individual bands. The interlacings created by a weaving process are typically perpendicular. This means that the interwoven bands are arranged at right angles to each other, thus forming the fabric.

[0013] A corresponding spread tow fabric (spread tow fabric Brück) is known, for example, from "Spread tow fabric", Wikipedia, website, https: / / en. Wikipedia, org / wiki / Spread_tow_fabric, downloaded on October 5, 2022, or as products "TeXtreme (R)" from Oxeon AB, Oxeon AB, Foretagsgatan 24, 504 64 Boras, SWEDEN, see, for example, the website https: / / www. textreme. com / products-services / spread-tow-products / " dated October 6, 2022. In such a fabric, the fibers are first combed and spread to a specific width before the weaving process. The spread tows are further processed into fabrics and then into prepreg. This creates so-called "spread tows." Due to the large width of the tows compared to a round / oval yarn, the resulting fabric exhibits significantly less waviness of the fibers and fewer crossing points.

[0014] According to the invention, the use of spread-tow fabric-reinforced prepreg avoids the need for sealing varnish on air duct components.

[0015] For the production of air duct components, prepreg is used, which consists of a resin system and a special, namely a spread-tow reinforcement fabric.

[0016] The invention is based on the following finding:

[0017] The extensive (reinforcing) fabric of the prepregs previously used for such components features a defined intersecting band (weave). At each intersection point, the bands must deflect from one another in a wave-like manner, which locally orients them in the thickness direction, i.e., transversely / obliquely relative to their planar extension area. Due to the crosslinking reaction of the resin (resin composition) during curing, microchannels form within the prepreg. By aligning the bands at the intersection points, the channels can also run through the entire layer structure, thus extending from the interior to the exterior. The air duct components commonly used in practice are made from glass fiber and / or carbon fiber prepregs. Due to the weave used, the reinforcing fabrics exhibit a high degree of waviness in the bands, known as undulation.In air duct components, air can penetrate the wall through the microchannels at the intersection points between the interior and exterior spaces. This compromises the tightness of the component or wall to such an extent that the required leakage value of, for example, 3 l / min / m is not met. 2 can only be achieved by subsequently painting the wall or component with a sealing varnish.

[0018] The invention is based on the discovery that the comparatively large width of the bands in spread-tow fabrics results in significantly less waviness of the fibers and fewer intersection points. In particular, the use of two superimposed spread-tow prepreg layers makes it particularly easy to achieve the required tightness of air duct components.

[0019] The invention is therefore also based on the finding that components currently manufactured in practice, particularly using NDS technology (low-pressure hose technology, see, for example, DE 10 2012 013 289 A1 or DE 10 2016 013 115 A1), must be coated with sealing varnish after curing to achieve the required airtightness. This sealing varnish leads to poorer fire properties and additional costs for material, weight, and processing times.

[0020] According to the invention, thanks to the "spread-tow fabric" material and / or the omission of the sealing varnish, which is no longer required, a weight reduction in the double-digit percentage range is possible compared to a conventional design. According to the invention, air duct components with sufficient tightness can be manufactured thanks to the prepregs reinforced with spread-tow fabric. This eliminates the need for subsequent application of sealing varnish to air duct components.

[0021] For the air duct components, prepregs are used, which consist of or contain a special resin (see below: resin composition according to WO 2019 / 034280 A1) and the special fabric, namely the spread-tow fabric. However, the component can also be manufactured using a different resin, especially if it is a polyaddition resin. By using two superimposed spread-tow prepreg layers, the required tightness of the air duct component can be achieved without the use of additional sealing varnish.

[0022] According to the invention, spread-tow fabric is processed with a particularly flame-retardant resin system to form a prepreg semi-finished product suitable for aviation, which already achieves the required tightness of air duct components, particularly with two superimposed layers.

[0023] The term "passenger aircraft" is to be understood broadly here and also includes, for example, UAM (urban air mobility) aircraft.

[0024] The width of the bands in the spread-tow fabric is in particular greater than 1 cm, especially greater than 2 cm. The grammage of the spread-tow fabric is in particular between 50 g / m 2 and 200 g / m 2 , e.g. 160 g / m 2 , fabric basis weight.

[0025] In a preferred embodiment, at least one, in particular several, in particular all, of the bands has a cross-sectional width-to-height ratio of at least 100 to 1 (100 / 1). The cross-section is oriented transversely to the longitudinal direction of the band. In particular, the ratio is at least 200 to 1 or at least 250 to 1. This allows for the creation of a particularly dense and also flat fabric.

[0026] In a preferred embodiment, the bands are woven at right angles to each other according to the weave. A corresponding fabric can then be produced particularly easily.

[0027] In a preferred variant of this embodiment, the weave is a plain weave. This weave is also particularly easy to produce.

[0028] In a preferred embodiment, the spread-tow fabric has at least one, in particular a plurality of gap points. The wall contains at least one, in particular also several covering agents. The covering agent covers at least one, in particular also several or all of the respective gap points. Such a gap point is a gap in the fabric in the sense that the fabric is weaker, less dense there than at other points. The gap point is therefore a point or region in which fewer or no fibers of a band, or no band at all, are present perpendicular to the extension surface of the fabric. At a gap point, microchannel formation in the resin composition during its curing perpendicular to the wall is possible or the probability is increased, which increases the permeability of air in this region.By covering the gap with the covering agent, the corresponding "gap" in the layer / fabric is closed, preventing or mitigating microchannel formation there as well, or reducing the likelihood of such formation. This improves the airtightness of the wall.

[0029] In a preferred variant of this embodiment, at least one of the gap points is an intersection point of the respective side edges of two intersecting bands. "Side" here again refers to the surface area of ​​the fabric. Such a gap point arises, for example, in the middle of four intersecting bands, with two of the bands lying parallel to each other and ideally directly adjacent to each other. Even with this configuration, space may remain in the middle of the intersection area for a passage channel, since the bands may not fit perfectly against each other. Particularly with a plain weave, such a tight, completely sealed fit is simply impossible due to the necessary intersections. Sealing with a covering agent is therefore particularly effective at such locations.

[0030] In a preferred variant of this embodiment, the covering agent covers at least two, in particular more than two, in particular all of the gap points of the first layer together. In particular, several or all of the gap points of the first layer are thus covered jointly by the covering agent. This achieves a particularly tight wall (fabric with sealant).

[0031] In a preferred variant of this embodiment, the covering agent is another prepreg material. This can be applied in the form of local "patches," for example, one patch per gap point to cover it. However, it is also particularly suitable as a complete layer (see below).

[0032] In a preferred variant of this embodiment, the additional prepreg material also contains a spread-tow fabric. This allows for a particularly dense wall. Two superimposed layers of spread-tow fabric are sufficient in practice to meet even the strictest airtightness requirements, as already mentioned above.

[0033] In a preferred embodiment, the covering agent is a further layer of the additional prepreg material that completely covers the first layer. Particularly with identical fabrics in both layers, it is then only necessary to ensure that the respective gap points of both layers do not overlap. In practice, this is easily achieved by appropriate offsetting and leads to particularly high levels of tightness.

[0034] In a preferred embodiment, the wall has a leakage / leakage rate / leakage rate of air between the interior and exterior of at most 3 l / min / m 2 , in particular not more than 1.5 I / min / m 2 at a pressure difference of 40 mbar between the interior and exterior. This also meets particularly strict sealing requirements for air duct components.

[0035] In a preferred embodiment, the resin composition is one for a prepreg resin, comprising: - a phosphorus-modified epoxy resin, - another epoxy resin component, - a hardener, - an imidazolium salt as initiator, wherein the resin composition comprises a reactive diluent in a proportion of 2 to 5 percent by weight to accelerate the curing of the phosphorus-modified epoxy resin.

[0036] Such a resin composition is one according to document WO 2019 / 034280 A1, International Application Number PCT / EP2018 / 000393, of the applicant Diehl Aviation Laupheim GmbH, published on February 21, 2019, to which reference is made here. The following technical features of the referenced document are intended to be part of the teaching of the invention: the resin composition and the method for its production, as well as the prepreg material comprising a fiber material impregnated with the resin composition. By reference, the document is therefore incorporated into the disclosure of the invention. In other words, the present component can be or can be produced using this resin composition.

[0037] The object of the invention is also achieved by a method according to claim 13. This method serves to produce a component according to the invention. In the method, the spread-tow fabric is integrated into the wall in at least the first layer as a fabric. The integration is carried out in particular by baking, in particular according to the low-pressure hose construction / NDS technology, as already mentioned above.

[0038] The method and at least some of its possible embodiments as well as the respective advantages have already been explained in connection with the component according to the invention.

[0039] In a preferred embodiment of the method in conjunction with the above-mentioned embodiment concerning the gap points, at least one of the gap points is covered with the covering agent, wherein the covering agent is integrated into the wall. In particular, the covering agent is impregnated with the resin composition of the first layer and / or enclosed by it. In particular, during production, an additional spread-tow fabric is applied as a covering agent to the first layer of the fabric. This creates a particularly tight air duct component.

[0040] The object of the invention is also achieved by a use according to patent claim 15. A spread tow fabric is used in the component according to the invention or in the method according to the invention.

[0041] Further features, effects, and advantages of the invention will become apparent from the following description of a preferred embodiment of the invention and the accompanying figures. Each of these figures shows a schematic diagram:

[0042] Figure 1 shows an air duct component according to the invention in a highly stylized representation in perspective view,

[0043] Figure 2 shows section II of Figure 1 in more detail,

[0044] Figure 3 is a plan view of the two fabric layers from Figure 2 in the direction of arrow III.

[0045] Figure 1 shows a component 2, here an air duct component of an air conditioning system 4 (not shown in detail) of a passenger aircraft 6. The component 2 serves to guide air 8 through the component 2 in the direction of the arrow 9. For this purpose, the component 2 has an interior space 10 which extends from an inlet 12 to an outlet 14 of the component 2. The interior space 10 serves to actually guide the air 8 from the inlet 12 to the outlet 14 when the component 2 is in operation, ie when air 8 flows through it.

[0046] The interior 10 of the component is surrounded by a wall 16, with inlet 12 and outlet 14 left free by the wall 16. The wall 16 therefore forms an airtight boundary between the interior 10 and an exterior 18, or rather, the surroundings of the component 2. "Airtight" here means that, at a corresponding differential pressure dp between the interior 10 and the exterior 18, the following leaks L occur.

[0047] This means that the component is well below the maximum permissible leakage L of 1.96 l / min / m 2 .

[0048] The comparatively high level of airtightness is achieved as follows: In this case, the wall 16 contains a first layer 20a and a second layer 20b of a prepreg material 22. The prepreg material 22 extends over a surface, namely along a surface in the shape of a straight circular cylinder. The size and thickness ratios of the wall 16 and the layers 20a, b are shown highly distorted in the figures for the sake of clarity. Each of the layers 20a, b or each of the prepreg materials 22 contains a correspondingly extensive fabric 24a, b, which is impregnated with a resin composition 26. In the example shown, the two prepreg materials 22 have already been finished to form the wall 16, i.e., baked into an overall composite in the form of the wall 16 using a standard thermal process, which will not be explained in detail here.The two fabrics 24a, b are therefore cast, pressed, or integrated into the resin composition 26 in their baked form. In the present case, both fabrics 24a, b are respective spread-tow fabrics 28.

[0049] Figure 2 shows section II of Figure 1. This schematically illustrates the structure of the spread-tow fabric 28. Each of the spread-tow fabrics 28 contains, in the usual manner, respective spread bands 30 of fibers 32, which are only symbolically indicated here. The bands 30 are woven together according to a weave 34. In this case, the weave 34 is a plain weave.

[0050] To clarify the bond, the bands 30 running in the circumferential direction of the cylindrical shape of component 2 are shown hatched in Figure 2. The bands running in the axial direction are shown without hatching.

[0051] In Figure 2, a cross-section 36 of a band 30 is indicated by hatching, transverse to its longitudinal direction; here, as an example, for an axially extending band 30. The cross-section 36 thus extends in the radial circumferential plane. Its ratio V of its width B to its height H is at least 100 to 1, in the present case, namely 200 to 1.

[0052] According to the plain weave in the form of weave 34, the bands 30 are woven at right angles to each other (circumferential direction to axial direction). In particular, the fabric 24a of the first layer 20a (in the example, however, both fabrics 24a, b) has gap points 40. The gap points 40 are located at the respective intersection points of the side edges 42 of the bands 30.

[0053] For clarity, Figure 3 shows a top view of layer 20b or fabric 24b, viewed in the direction of arrow II in Figure 2. The underlying fabric 24a is shown in dashed lines. The side edges 42 of the bands 30 of layer 20a, shown in dashed lines, thus intersect, creating corresponding gaps 40. This is because the bands 30 do not adjoin one another seamlessly, which is a necessary consequence of the respective overlap of the bands 30 due to the plain weave.

[0054] At these locations of the gap points 40 or "gaps," the problem arises that—if only layer 20a is present—microchannels can form in the resin composition 26 through layer 20a or the "gaps" between the bands 30, which could extend essentially in the radial direction of the component 2, i.e., between the interior 10 and the exterior 18. This would result in the microchannels representing connecting channels for the flow of air 8, which would greatly reduce the airtightness of the wall 16.

[0055] For this reason, layer 20b is arranged over layer 20a as follows. Layer 20b forms a covering means 44 for the gap points 40: Each of the bands 30 of layer 20b covers one of the gap points 40 in the center, thus preventing the formation of the aforementioned air channels. Thus, maximum tightness of the wall 16 can be achieved with just two layers 20a, b, here both spread-tow fabric 28. In the example, the covering means 44 in the form of layer 20b therefore covers all gap points 40 of layer 20a together. In the present example, the reverse also applies, because layer 20b also has gap points 40 that are diagonally offset from layer 20a, which in turn are covered or closed by layer 20a as the covering means 44. For the sake of clarity, however, this is not indicated again by reference numerals in the figures.

[0056] In the example, the covering material 44 is also a prepreg material 22 in the form of a spread-tow fabric 28. The covering material 44 is also a further layer 20b of the prepreg material 22 that completely covers the first layer 20a.

[0057] In a method for manufacturing component 2, the spread-tow fabric 28 is integrated into the wall 16 in the first layer 20a as fabric 24a, namely baked in as described above. Furthermore, all gap points 40 in layer 20a are covered by the covering agent 44, and the covering agent 44 is also integrated into the wall 16 in the form of the second layer 20b, namely baked in the same way.

[0058] In other words, the spread tow fabric 28 is used in component 2 and in the described method for its production.

[0059] 2 component

[0060] 4 Air conditioning

[0061] 6 passenger aircraft

[0062] 8 Air

[0063] 9 Arrow

[0064] 10 Interior

[0065] 12 Entrance

[0066] 14 Outlet

[0067] 16 wall

[0068] 18 Outdoor space

[0069] 20a, b location

[0070] 22 Prepreg material

[0071] 24a, b tissue

[0072] 26 Resin composition

[0073] 28 Spread-Tow fabric

[0074] 30 volumes

[0075] 32 fibers

[0076] 34 Binding

[0077] 36 cross section

[0078] 40 gaps point

[0079] 42 margin

[0080] 44 covering agents

[0081] L Leakage dp Differential pressure

[0082] B Width

[0083] H Height

[0084] V ratio

Claims

PATENT CLAIMS 1. Component (2) which is designed to guide air (8) of an air conditioning system (4) of a passenger aircraft (6), - with an interior (10) which carries the air (8) during operation, - with a wall (16) which airtightly defines the interior space (10) from an exterior space (18) surrounding the component (2), - wherein the wall (16) contains at least a first layer (20a) of a planar prepreg material (22), - wherein the respective prepreg material (22) contains a planar fabric (24a, b) impregnated with a resin composition (26), - wherein in at least the first layer (20a) the fabric (24a, b) is a spread-tow fabric (28) containing respective spread bands (30) of fibers (32), the bands (30) being woven together according to a weave (34).

2. Component (2) according to claim 1, characterized in that at least one of the bands (30) in the cross section (36) has a ratio (V) of its width (B) to its height (H) of at least 100 to 1.

3. Component (2) according to one of the preceding claims, characterized in that the bands (30) are woven at right angles to one another according to the weave (34).

4. Component (2) according to claim 3, characterized in that the weave (34) is a plain weave.

5. Component (2) according to one of the preceding claims, characterized in that the spread tow fabric (28) has at least one gap point (40) and the wall (16) contains at least one covering means (44) which covers at least one respective one of the gap points (40).

6. Component (2) according to claim 5, characterized in that at least one of the gap points (40) is an intersection point of respective side edges (42) of two intersecting bands (30).

7. Component (2) according to one of claims 5 to 6, characterized in that the covering means (44) covers at least two of the gap points (40) of the first layer (20a) together.

8. Component (2) according to one of claims 5 to 7, characterized in that the covering agent (44) is a further prepreg material (22).

9. Component (2) according to claim 8, characterized in that the further prepreg material (22) also contains a spread tow fabric (28).

10. Component (2) according to one of claims 5 to 9, characterized in that the covering means (44) is a further layer (20b) of the further prepreg material (22) completely covering the first layer (20a).

11. Component (2) according to one of the preceding claims, characterized in that the wall (16) has a leakage (L) of air between the interior (10) and the exterior (18) of at most 3 l / min / m 2 at a pressure difference of 40 mbar.

12. Component (2) according to one of the preceding claims, characterized in that the resin composition (26) is one for a prepreg resin, comprising: - a phosphorus-modified epoxy resin, - another epoxy resin component, - a hardener, - an imidazolium salt as initiator, wherein the resin composition comprises a reactive diluent in a proportion of 2 to 5 percent by weight to accelerate the curing of the phosphorus-modified epoxy resin.

13. A method for producing a component (2) according to one of the preceding Claims, in which in at least the first layer (20a) the spread tow fabric (28) is integrated into the wall (16) as fabric (24a).

14. Method according to claim 13 in conjunction with claim 5, characterized in that at least one of the gap points (40) is covered with the covering means (44), wherein the covering means (44) is integrated into the wall (16).

15. Use of a spread tow fabric (28) in a component (2) according to one of claims 1 to 12 and / or in a method according to one of claims 13 to 14.

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