Method And Needle for Reinforcing Cellular Materials

Abstract

A method for reinforcing a cellular material includes producing a through-hole in the cellular material that extends from a first surface of the cellular material to a second surface of the cellular material; reaching through the through-hole from the first surface of the cellular material to the second surface of the cellular material; taking hold of at least one fiber bundle at the second surface of the cellular material; and pulling the at least one fiber bundle into the through-hole in the cellular material. Producing the through-hole in the cellular material includes perforating the cellular material with a rotating and/or oscillating needle.

Claims

1. A method for reinforcing a cellular material, comprising: producing a through-hole in the cellular material that extends from a first surface of the cellular material to a second surface of the cellular material by perforating the cellular material with a rotating and/or oscillating needle; reaching through the through-hole from the first surface of the cellular material to the second surface of the cellular material; taking hold of at least one fiber bundle at the second surface of the cellular material; and pulling the at least one fiber bundle into the through-hole in the cellular material.

2. The method of claim 1, wherein the needle drills into the cellular material to produce the through-hole.

3. The method of claim 1, wherein producing the through-hole in the cellular material includes pre-drilling the through-hole.

4. The method of claim 1, wherein the at least one fiber bundle is taken hold of by being hooked in the needle.

5. The method of claim 4, wherein the at least one fiber bundle is hooked in a groove integrated into the needle.

6. The method of claim 1, wherein the needle is heated prior to and/or during producing the through-hole.

7. The method of claim 1, wherein pulling the at least one fiber bundle into the through-hole includes pulling the needle into the through-hole such that it is followed by the least one fiber bundle.

8. The method of claim 1, wherein the through-hole is produced with a cross-sectional surface that is smaller than double the thickness of the fiber bundle to be pulled therethrough such that the fiber bundle is compressed while being pulled through.

9. The method of claim 1, further comprising: shearing off the at least one fiber bundle pulled into the through-hole such that it ends flush with at least one of the first surface and the second surface; or placing the at least one fiber bundle pulled into the through-hole against at least one of the first surface and the second surface.

10. The method of claim 1, further comprising: forming a cover layer on at least one of the first surface and the second surface.

11. The method of claim 1, further comprising: filling the through-hole containing the at least one fiber bundle with a matrix material.

12. A needle for reinforcing a cellular material with a method according to claim 1, the needle comprising: a cylindrical shaft; a cutting edge at a tip of the cylindrical shaft; and a hook integrated into the cylindrical shaft to take hold of the fiber bundle.

13. The needle of claim 12, wherein the cylindrical shaft is formed with at least one helical flute.

14. The needle of claim 12, wherein the hook is formed as a groove within the cylindrical shaft.

15. The needle of claim 14, wherein the groove is at least partly running around a lateral surface of the cylindrical shaft.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The invention will be explained in greater detail with reference to exemplary embodiments depicted in the drawings as appended.

[0035] The accompanying drawings are included to provide a further understanding of the present invention and are incorporated in and constitute a part of this specification. The drawings illustrate the embodiments of the present invention and together with the description serve to explain the principles of the invention. Other embodiments of the present invention and many of the intended advantages of the present invention will be readily appreciated as they become better understood by reference to the following detailed description. The elements of the drawings are not necessarily to scale relative to each other. In the figures, like reference numerals denote like or functionally like components, unless indicated otherwise.

[0036] FIG. 1 shows an initial state of a method according to an embodiment of the invention.

[0037] FIG. 2 shows several steps of the method following the initial state in FIG. 1.

[0038] FIG. 3 shows a further step of the method following the steps in FIG. 2.

[0039] FIG. 4 shows a cellular material with an introduced fiber bundle after the steps in FIGS. 2 to 3.

[0040] FIG. 5 shows a sandwich-type component reinforced with a method according to another embodiment of the invention.

[0041] FIG. 6 shows a sandwich-type component reinforced with a method according to yet another embodiment of the invention.

[0042] FIG. 7 shows a needle according to a further embodiment of the invention.

[0043] FIG. 8 schematically shows selected steps of the method of FIGS. 1 to 4.

DETAILED DESCRIPTION

[0044] Although specific embodiments are illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations may be substituted for the specific embodiments shown and described without departing from the scope of the present invention. Generally, this application is intended to cover any adaptations or variations of the specific embodiments discussed herein.

[0045] FIG. 1 shows a needle 8 before the perforation of a cellular material 1. The needle 8 features an eyelet region on its tip that is open on one side and that serves as a hook 11 for holding a fiber bundle 3 (cf. FIGS. 2 and 3). The cellular material 1 consists, for example, of a PMI rigid cellular material or a cellular material of lower quality, for example, a cellular PVC material or a cellular polyurethane material. The cellular material 1 may also consist of a textile material such as, for example, a felt or any other non-woven fabric. According to FIG. 1, the needle 8 is aligned relative to the vertical line by an angle . The angle a can be varied between 0 and 90 in order to introduce a fiber bundle into the cellular material 1 at an arbitrary angle . This may make it possible to achieve a custom-tailored reinforcement so as to take especially into account certain load situations, to which the cellular material 1 will be subjected in the sandwich construction. Although the angle is merely illustrated two-dimensionally due to the two-dimensional figure, this angle naturally may also be a solid angle such that the through-hole and the fiber bundle subsequently situated therein can be arranged in the cellular material 1 at an arbitrary solid angle.

[0046] In one embodiment the needle 8 may have a circular shaft 9 that this tapered to a tip of the needle 8. In the region of the tip, the needle 8 may feature an eyelet that, however, is provided with an opening on one side in order to the thusly introduce a fiber bundle 3 into the eyelet region of the needle 8. The eyelet region of the needle 8 therefore may consist of a first limb that continuously extends to the tip and a second limb that extends back in the direction of the circular shaft 9, however, without reaching said shaft from the tip (in a convexly curved fashion). However, as will be explained in conjunction with FIG. 7, the needle 8 may be configured in various different ways, in particular it may be formed as a drilling needle combining features of a sewing needle with those of a drill bit. Arrows indicate in FIG. 1 the perforating motion of the needle 8 as it will be further detailed in conjunction with FIG. 2 below. This particularly includes a rotating and/or vibrating and/or oscillating motion of the needle 8.

[0047] FIG. 2 shows a stage of the method M, in which the needle 8 has just penetrated the cellular material 1 with its point. Due to this penetration, a through-hole 2 was produced in the cellular material 1 that extends through the cellular material 1 at a solid angle . A fiber bundle 3 (for example, a 24K roving) that was shaped into a loop in the immediate vicinity of the underside of the cellular material 1 is situated underneath the cellular material 1 in the region of the exit point of the needle 8. This loop of the fiber bundle 3 therefore can be taken hold of or grasped by the needle 8 in order to pull the fiber bundle 3 into the cellular material 1 when the needle 8 is retracted.

[0048] As it is indicated by arrows in FIG. 2, perforating the cellular material 1 with the needle 8 includes rotating and/or vibrating and/or oscillating the needle 8. The rotating and/or vibrating motion of the needle 8 effectively reduces the force needed to penetrate the cellular material 1 and thus open up the possibility to manufacture higher core densities and thicknesses without any significant cost or weight increase. The needle 8 may be configured as shown in FIG. 2. Alternatively, the needle 8 may however also be shaped similar to a drill, e.g. as shown in FIG. 7, for achieving a better penetration performance by drilling the through-hole 2. To further ease the penetration of the cellular material 1, the method M may further comprise heating the needle 8 and/or pre-drilling the through-hole 2 with a separate drill or the like, e.g. in form of a mechanical drill or a laser or similar. For example, the through-hole 2 may be pre-drilled with a separate drill and then be widened in a second drill and/or a piercing step with a needle 8 that may be formed similar to a drill bit.

[0049] Although the fiber bundle 3 is illustrated in the form of a loop in FIG. 2 for reasons of clearness, the fiber bundle 3 may actually be arranged underneath the cellular material 1 and stretched straight parallel thereto in order to take hold of this stretched fiber bundle 3 underneath the cellular material 1 with the aid of the needle 8. The fiber bundle 3 may have a single thickness S such that the looped fiber bundle section according to FIG. 2 approximately has a double thickness 2S.

[0050] In FIG. 3, the needle 8 is already retracted again from the cellular material 1. Due to this retraction, the fiber bundle 3 taken hold of or grabbed by the needle 8 is pulled into the through-hole 2 on the underside of the cellular material 1. The fiber bundle 3 may be compressed when it penetrates into the through-hole. This compression may occur in case the needle 8 and therefore the through-hole 2 have a cross-sectional surface that is smaller than the double thickness 2S of the fiber bundle being pulled through. The individual fibers of the fiber bundle 3 are essentially aligned straight and tightly pressed against one another in the through-opening 2 due to this compression and the tensile force exerted upon the fiber bundle by the needle 8 such that only very fine intermediate spaces remain between the individual fibers.

[0051] In FIG. 4, the entire fiber bundle 3 is pulled into the cellular material 1 at the angle , wherein the needle 8 was already decoupled from the fiber bundle 3. For example, the fiber bundle 3 can now be cut off flush with both sides of the cellular material 1 in order to subsequently infiltrate the through-hole 2 with a resin, as shown in FIG. 5. Alternatively, the ends of the fiber bundle 3 shown in FIG. 4 can be placed against both surfaces of the cellular material 1 and bonded thereto. The bonding can be realized, for example, by laminating cover layers 7 that, however, are not illustrated in FIG. 5 to both surfaces of the cellular material such that the ends of the fiber bundles 3 tightly adjoin and are bonded to the surfaces of the cellular material 1.

[0052] Instead of merely producing one through-hole 2 in the core of the sandwich-type component in the above-described fashion in order to pull through a fiber bundle 3, it is also possible to additionally penetrate the cover layers 7 with the needle 8 as shown in FIG. 6 in order to subsequently pull a fiber bundle 3 through the entire sandwich-type component 5, wherein the ends of said fiber bundle may once again be flatly placed against and bonded to the cover layers 7 or cut off flush with the cover layers 7 as shown in FIG. 6. The sandwich-type type component 5 may be, for example, a part of the interior lining of a passenger cabin of an aircraft or spacecraft. Alternatively, the sandwich-type component 5 may be part of a flap, a rudder or a general fuselage structure of the aircraft or spacecraft.

[0053] FIG. 7 shows a needle 8 according to a further embodiment of the invention. This needle 8 may alternatively be employed in the method M shown in FIGS. 1 to 4. Contrary to the needle 8 shown in FIG. 2, the needle 8 in FIG. 7 is formed as a drilling needle. The needle 8 features a cylindrical shaft 9 that has helical flutes 12 encircling a lateral surface of the cylindrical shaft 9. At a tip of the cylindrical shaft 9 a cutting edge 10 is provided. Near the tip of the cylindrical shaft 9 a hook 11 is integrated into the cylindrical shaft 9 to take hold of a (looped) fiber bundle 3. The hook 11 is formed as a groove 13 within the cylindrical shaft 9, which is at least partly circulating the lateral surface of the cylindrical shaft 9. The groove 13 is similarly formed to the helical flutes 12, however it is arranged under a different inclination angle than the helical flutes 12. The person of skill will be aware that multiple different embodiments of the hook 11 may be provided that serve the purpose of hooking in a fiber bundle 3 and that the depicted configuration is of purely exemplary nature.

[0054] FIG. 8 schematically shows selected steps of the method M of FIGS. 1 to 4. The method M comprises under M1 producing a through-hole 2 in a cellular material 1 that extends from a first surface of the cellular material 1 to a second surface of the cellular material 1. This step includes perforating the cellular material 1 with a needle 8 that is rotating and/or oscillating. In particular, the needle 8 may drill into the cellular material 1 to produce the through-hole 2. To this end, the at least one fiber bundle 3 may be taken hold of by being hooked in a groove 13 integrated into the needle 8. Optionally, the needle 8 may additionally be heated. The heating may be done prior to and/or during perforating the cellular material 1. Further, the through-hole 2 may be optionally pre-drilled before the cellular material 1 is perforated with the needle 8.

[0055] The method M further comprises under M2 reaching through the through-hole 2 from the first surface of the cellular material 1 to the second surface of the cellular material 1. The method M further comprises under M3 taking hold of at least one fiber bundle 3 at the second surface of the cellular material 1. The method M further comprises under M4 pulling the at least one fiber bundle 3 into the through-hole 2 in the cellular material 1.

[0056] Optionally, the method M may comprise under M5 shearing off the at least one fiber bundle 3 pulled into the through-hole 2 such that it ends flush with at least one of the first surface and the second surface. Alternatively, the method M may optionally comprise under M5 placing the at least one fiber bundle 3 pulled into the through-hole 2 against at least one of the first surface and the second surface. Further, the method M may optionally comprise under M6 forming a cover layer 7 on at least one of the first surface and the second surface. Further, the method M may optionally comprise under M7 filling the through-hole 2 containing the at least one fiber bundle 3 with a matrix material.

[0057] In the foregoing detailed description, various features are grouped together in one or more examples or examples with the purpose of streamlining the disclosure. It is to be understood that the above description is intended to be illustrative, and not restrictive. It is intended to cover all alternatives, modifications and equivalents. Many other examples will be apparent to one skilled in the art upon reviewing the above specification.

[0058] The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. Many other examples will be apparent to one skilled in the art upon reviewing the above specification.

[0059] While at least one exemplary embodiment of the present invention(s) is disclosed herein, it should be understood that modifications, substitutions and alternatives may be apparent to one of ordinary skill in the art and can be made without departing from the scope of this disclosure. This disclosure is intended to cover any adaptations or variations of the exemplary embodiment(s). In addition, in this disclosure, the terms comprise or comprising do not exclude other elements or steps, the terms a or one do not exclude a plural number, and the term or means either or both. Furthermore, characteristics or steps which have been described may also be used in combination with other characteristics or steps and in any order unless the disclosure or context suggests otherwise. This disclosure hereby incorporates by reference the complete disclosure of any patent or application from which it claims benefit or priority.