Honeycomb structure made of a non-woven made of recycled carbon fibers

Abstract

A honeycomb structure comprising carbon-fiber non-woven, sandwich structure comprising the honeycomb structure, and process for the production of the honeycomb structure.

Claims

1. A honeycomb structure comprising carbon-fiber non-woven and unidirectional fibers wherein a ratio by mass of carbon-fiber non-woven to unidirectional fibers is greater than 10:1.

2. The honeycomb structure according to claim 1, wherein the honeycomb structure is composed predominantly of carbon-fiber non-woven.

3. The honeycomb structure according to claim 1, wherein the carbon-fiber non-woven comprises reclaimed carbon fibers.

4. The honeycomb structure according to claim 1, wherein a length of the fibers of the carbon-fiber non-woven is from 6 to 50 mm.

5. The honeycomb structure according to claim 1, wherein the fibers of the carbon-fiber non-woven are predominantly unoriented.

6. The honeycomb structure according to claim 5, wherein the fibers of the carbon-fiber non-woven have a random orientation.

7. The honeycomb structure according to claim 1, wherein the honeycomb structure is impregnated with synthetic resin.

8. The honeycomb structure according to claim 1, wherein the honeycomb structure additionally comprises fire-retardant additives.

9. A sandwich structure comprising a honeycomb structure comprising carbon-fiber non-woven and unidirectional fibers wherein a ratio by mass of carbon-fiber non-woven to unidirectional fibers is greater than 10:1.

10. The sandwich structure according to claim 9 moreover comprising two substantially parallel-arranged outer layers, between which the honeycomb structure is arranged, wherein the walls of the honeycomb structure are arranged so as to be substantially orthogonal to the outer layers.

11. The sandwich structure according to claim 9, wherein the outer layers are composed of at least one of GRP, CFRP and metal.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1a shows a layer of nonwoven.

(2) FIG. 1b shows beads of adhesive applied to the layer of nonwoven of FIG. 1a.

(3) FIG. 1c shows a second layer of nonwoven applied to the beads of adhesive of FIG. 1b.

(4) FIG. 1d shows a second application of adhesive beads on the second layer of nonwoven of FIG. 1c.

(5) FIG. 1e shows a third layer of nonwoven applied to the beads of adhesive of FIG. 1d.

(6) FIG. 1f shows a third application of adhesive beads on the third layer of nonwoven of FIG. 1e.

(7) FIG. 2a shows a longitudinal section of a stack of layers of nonwoven prior to the application of tensile forces.

(8) FIG. 2b shows the longitudinal section of the stack of layers after the application of tensile forces creating a hexagonal honeycomb structure.

(9) FIG. 2c shows the longitudinal section of the stack of layers after the application of tensile forces creating a honeycomb structure with rounded edges.

(10) FIG. 3 shows a perspective view of the honeycomb structure of FIG. 2b.

(11) FIG. 4 shows a perspective view of a honeycomb sheet cut from the honeycomb structure of FIG. 3.

(12) FIG. 5 shows the honeycomb sheet of FIG. 4 being assembled with two outer sheets.

(13) FIG. 6 shows the honeycomb sheet and outer sheets of FIG. 5 in an assembled state.

(14) FIG. 7 shows a longitudinal partial sectional view of the structure of FIG. 6.

(15) FIG. 8 shows an enlarged junction area of the structure of FIG. 7.

(16) FIG. 9a shows a plan view of a 90/0 multiaxial laid scrim.

(17) FIG. 9b shows a plan view of a 45/45 multiaxial laid scrim.

(18) FIG. 9c shows a plan view of a carbon-fiber non-woven.

(19) FIG. 9d shows a plan view of a carbon-fiber paper.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(20) FIGS. 1a-1f show the production of a precursor from which it is possible to produce honeycomb structures of the invention made of carbon-fiber non-woven.

(21) A first layer of carbon-fiber non-woven (1) is provided. A plurality of first, parallel-arranged beads (3) of adhesive are applied substantially with regular separations onto the upper side (2a) thereof. The underside (2b) of the first layer of carbon-fiber non-woven remains free from the said beads of adhesive. For this, the rheology of the adhesive can be adjusted in such a way that, under the application conditions, no significant quantity of adhesive penetrates through the carbon-fiber non-woven and no adhesive is present on the underside of the first layer (1). The arrangement can have carbon-fiber paper on the underside of each layer in order that, under the application conditions, no significant quantity of adhesive penetrates through the carbon-fiber non-woven and no adhesive is present on the underside of the first layer (1). Another possibility is that beads of adhesive applied take the form of thermoplastic adhesive similar to an adhesive tape so that, under the application conditions, no significant quantity of adhesive penetrates through the carbon-fiber non-woven and no adhesive is present on the underside of the first layer (1).

(22) The separations between the beads (3) of adhesive are such that the resultant separation (4) between the individual beads (3) of adhesive is about three to nine, particularly preferably from five to seven, widths of the beads of adhesive. The parallel-arranged beads (3) of adhesive therefore cover about to 1/10, particularly preferably to , of the upper-side area of the first layer of carbon-fiber non-woven (1). A half honeycomb can subsequently be produced by folding along the edges (5) of the beads of adhesive, and also along the broken lines (5). In the next step a second layer of carbon-fiber non-woven (7) is placed onto the said first layer (6) with beads of adhesive. A plurality of further, parallel-arranged beads (8) of adhesive are in turn applied with substantially regular separations onto the upper-side area of the uppermost layer of carbon-fiber non-woven (7), whereupon the further, parallel-arranged beads (8) of adhesive likewise cover from to 1/10, particularly preferably from to , of the area of the further layer of carbon-fiber non-woven (7), being arranged parallel, and also centrally offset with respect to the aforementioned, between the beads (3) of adhesive located under the uppermost layer of carbon-fiber non-woven. The underside of the further layer of carbon-fiber non-woven (7) in turn remains free from the said beads of adhesive. A further layer of carbon-fiber non-woven (9) is then placed onto the material. Repetitions of the last two steps produce a stack of layers of carbon-fiber non-woven between which there are parallel layers of beads of adhesive. The positions of the beads of adhesive of alternate layers (3) and (10) here are directly above one another in the direction orthogonal to the layers of carbon-fiber non-woven.

(23) FIGS. 2a-2c show a detail of this arrangement in longitudinal section, where the arrangement has an outer layer (11) above the final layer of beads (10) of adhesive. After the hardening of the beads of adhesive, the arrangement can be expanded via tensile forces (12) directed so as to be orthogonal to the layers of carbon-fiber non-woven and incident on the first and the final layer of carbon-fiber non-woven, and give a honeycomb structure as depicted in FIG. 3.

(24) FIG. 3 shows an expanded honeycomb structure made of the corrugated individual layers (1), (7), (9) and (11) bonded to one another by the beads of adhesive. The beads (3) of adhesive bond only some parts of the undermost layer of carbon-fiber non-woven (1) to the layer (7) situated thereabove, and specifically in such a way that a honeycomb (13) is formed from the sections located in the layers of carbon-fiber non-woven (1) and (7) between two beads (14) of adhesive. The said honeycomb can have the shape of a hexagon. To this end, at the two sections located between the beads (14) of adhesive in the layers of carbon-fiber non-woven (1) and (7) there can in each case be four sharp bends (15) which in each case form two adjacent angles of the hexagon; within a honeycomb, these pairs of angles are located opposite to one another. The remaining two angles are formed by the layers of carbon-fiber non-woven (1) and (7) held together by the beads of adhesive, and specifically in each case at the edges of the beads of adhesive.

(25) The hexagon (13) that forms the honeycomb is thus formed.

(26) FIG. 2c shows another embodiment of the honeycombs of the invention, with a greater degree of edge-rounding.

(27) FIG. 3 shows an expanded honeycomb structure (17) in the form of a block, said structure having been impregnated with resin and cured. It is composed of a multiplicity of parallel honeycombs (18) of approximately equal dimensions.

(28) FIG. 4 shows a honeycomb sheet 19 which has been cut to size from an expanded honeycomb structure (17), for example by sawing. The cut here is made perpendicularly to the longitudinal direction of the individual tubes of the honeycomb.

(29) FIG. 5 shows a honeycomb sheet (19), and also two outer sheets (20) and (21) which are placed upon the two sides of the honeycomb sheet (19); this arrangement has the walls (22) of the honeycombs perpendicular to the outer sheets (20) and (21). The outer sheets (20), (21) are composed of at least one of GRP, CFRP and metal.

(30) FIG. 6 shows a sandwich structure made of a honeycomb sheet (19) provided with two outer sheets (20) and (21). There is frictional bonding here between the honeycombs and the outer sheets.

(31) FIG. 7 shows a cross section through a sandwich structure made of a honeycomb sheet (19) provided with two outer sheets (20) and (21). The bond (23) bonds the walls of the honeycombs (22) to the outer sheet (29).

(32) FIG. 8 is an enlargement of the bond (23) between the walls of the honeycombs (22) and the outer sheet (29). An adhesive (24) provides a frictional bond here between the walls of the honeycombs (22) and the outer sheet (29), giving a fillet joint.

(33) FIGS. 9a-9d depict a 90/0 multiaxial laid scrim (25), a 45/45 multiaxial laid scrim (26), a carbon-fiber non-woven (27), and a carbon-fiber paper (28).

(34) 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.

LIST OF REFERENCE CHARACTERS

(35) (1) First layer of carbon-fiber non-woven (2a) Upper side of first layer of carbon-fiber non-woven (2b) Underside of first layer of carbon-fiber non-woven (3) Beads of adhesive (4) Separation between individual beads of adhesive (5) Edges of beads of adhesive (6) First layer with beads of adhesive (7) Second layer of carbon-fiber non-woven (8) Further beads of adhesive (9) Further layer of carbon-fiber non-woven (10) Beads of adhesive of the respective alternate layer (11) Outer layer (12) Tensile forces (13) Hexagonal honeycomb (14) Beads of adhesive arranged so as to be mutually superposed (15) One layer of carbon-fiber non-woven (16) Sharp bends formed by two bonded layers (17) Expanded honeycomb structure in block form (18) Parallel honeycombs (19) Honeycomb sheet (20) Upper outer sheet (21) Lower outer sheet (22) Walls of honeycombs (23) Bond between honeycomb and outer sheet (24) Adhesive (25) 90/0 multiaxial laid scrim (26) 45/45 multiaxial laid scrim (27) Carbon-fiber non-woven (28) Carbon-fiber paper