FIBER COMPOSITE MATERIAL, A METHOD OF MANUFACTURING A COMPOSITE STRUCTURE AND COMPOSITE STRUCTURE

Abstract

A fiber composite material containing at least one layer of reinforcing fibers embedded in a polymer matrix, with the polymer matrix being formed by a curable resin and including at least one first region having a first curing property of the resin and at least one second region having a second curing property of the resin, wherein the at least one first curing property is different from the at least one second curing property, a method of manufacturing a composite structure, and a composite structure manufactured in the method.

Claims

1. A fiber composite material containing at least one layer of reinforcing fibers embedded in a polymer matrix, with the polymer matrix being formed by a curable resin and comprising at least one first region having a first curing property of the resin and at least one second region having a second curing property of the resin, wherein the at least one first curing property is different from the at least one second curing property.

2. The fiber composite material according to claim 1, wherein the curing property of the resin in the first region and the second region is controllable by at least one of a chemical parameter, a thermal parameter and a physical parameter or a combination thereof.

3. The fiber composite material according to claim 1, wherein the curing property is controllable by an addition of at least one additive in the resin for one of accelerating and decelerating curing.

4. The fiber composite material according to claim 1, wherein the curing property is controllable by one of an increase and a decrease of temperature following a gradient during curing.

5. The fiber composite material according to claim 1, wherein the reinforcing fibers are provided as one of fibers pre-impregnated with the resin having the at least one first curing property or the at least one second curing property or as dry fibers to be impregnated with the resin having the at least one first curing property or the at least one second curing property after placement in a composite structure or combinations thereof.

6. A method of manufacturing a composite structure, comprising at least a first and a second substructure each comprising or consisting of the fiber composite material according to claim 1, the method comprising: curing the first region of the at least one first substructure and the first region of the at least one second sub-structure; contacting the at least one first substructure with the at least one second substructure; and co-curing the second region of the at least one first substructure and the second region of the at least one second substructure after contacting to form the composite structure.

7. The method according to claim 6, wherein the at least one first substructure and the at least one second substructure each has a layered arrangement of the first region and the second region, and the second regions are provided on sides of the substructures facing each other.

8. The method according to claim 6, wherein the second regions are provided in a longitudinal extension direction of the substructures wherein contacting is achieved by overlapping or abutting the second regions of the respective substructures or by overlapping or abutting the second region of the at least one first substructure with the second region of the at least one second substructure.

9. The method according to claim 6, wherein the second region of the at least one first substructure is interposed between first regions of the at least one second substructure.

10. The method according to claim 6, wherein at least one connecting layer comprising fibers embedded in an uncured polymer matrix is interposed between the at least one first substructure and the at least one second substructure before co-curing with the connecting layer being co-cured with the second regions.

11. The method according to claim 6, wherein the first regions and the second regions of at least one of the substructures are formed in a fiber or tape placement process wherein at least on first layer of fibers pre-impregnated with a resin having a first curing property is positioned adjacent to at least one second layer of fibers pre-impregnated with a resin having a second curing property in one of a layered configuration and a configuration having the second layer positioned in a longitudinal extension of the first layer or combinations thereof.

12. A composite structure manufactured in the method according to claim 6.

13. The composite structure according to claim 12, wherein the composite structure is configured as a tank structure, having a first substructure configured as a dome part and a second substructure configured as a cylindrical part, wherein the dome part is connected to the cylindrical part in an overlapping area, wherein the second region provided in the cylindrical part and the second region provided in the dome part facing each other are positioned in the overlapping area forming a bondline between the dome part and the cylindrical part.

14. The composite structure according to claim 13, wherein the dome part comprises a longitudinally protruding skirt portion with the overlapping area being extended into the skirt portion.

15. The composite structure according to claim 13, wherein the tank structure is configured as a liquid hydrogen tank in an aircraft and/or wherein the tank structure is manufactured from fiber reinforced plastic or carbon fiber reinforced plastic.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The disclosure herein will be explained in greater detail with reference to example embodiments depicted in the drawings as appended.

[0030] FIG. 1a schematically depicts a fiber composite material according to an embodiment of the disclosure herein;

[0031] FIG. 1b depicts a flowchart of a method of manufacturing a composite structure according to an embodiment of the disclosure herein;

[0032] FIG. 2 schematically depicts composite structures according to embodiments of the disclosure herein;

[0033] FIG. 3a-d schematically depict composite structures according to other embodiments of the disclosure herein;

[0034] FIG. 4 schematically depicts a composite structure according to another embodiment of the disclosure herein; and

[0035] FIG. 5 schematically depicts a section of a composite structure according to an embodiment of the disclosure herein configured as a tank structure.

DETAILED DESCRIPTION

[0036] The accompanying drawings are included to provide a further understanding of the disclosure herein and are incorporated in and constitute a part of this specification. The drawings illustrate the embodiments of the disclosure herein and together with the description serve to explain the principles of the disclosure herein. Other embodiments of the disclosure herein and many of the intended advantages of the disclosure herein will be readily appreciated as they become better understood by reference to the 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.

[0037] 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 disclosure herein. Generally, this application is intended to cover any adaptations or variations of the specific embodiments discussed herein.

[0038] In the figures of the drawings, identical elements, features, and components that have the same function, and the same effect are each given the same reference signs, unless otherwise specified.

[0039] FIG. 1a schematically depicts a fiber composite material 10 containing at least one layer of reinforcing fibers embedded in a polymer matrix 11, with the polymer matrix 11 being formed by a curable resin, whereas FIG. 1b depicts a flowchart of a method of manufacturing a composite structure according to an embodiment of the disclosure herein. The fiber composite material 10 comprises at a first region 100 having a first curing property of the resin and a second region 200 having a second curing property of the resin. In the first step 1 of the method the uncured fiber composite material 10 is provide before curing wherein in the second step 2 the first region 100 has undergone a first temperature profile that triggers curing of the resin material placed in the first region 100. The second region 200 provided as a second layer in the fiber composite material 10 of FIG. 1a comprises a resin in the polymer matrix 11 that cures at a different, increased temperature compared to the resin of the first region 100. In the third step 3 two fiber composite materials 10 are positioned adjacent with the second regions 200 facing each other. In this step the un-cured or semi-cured resins of the second regions 200 contact each other and are subject to diffusion and formation of a chemical/covalent binding interface between the resin of the second regions 200. In the fourth step 4 the entire composite structure 12 is cured at a second temperature which differs from the first curing temperature and which triggers curing of the resin in the polymer matrix 11 of the second regions 200 to form a highly reliable and tight joint in the second regions 200.

[0040] FIG. 2 schematically depicts composite structures 12 according to further embodiments of the disclosure herein. Therein, first substructures 13a and second substructure 13b each comprising or consisting of a polymer matrix 11 having resin impregnated fibers embedded therein, are about to be joined in the respective second regions 200 of the substructures 13a, b, whereas the second regions 200 are provided in a longitudinal extension direction of the fiber composite material 10 forming the substructures 13a, b. Contacting is achieved by overlapping or abutting the second regions 200 of the respective substructures 13a, b. The embodiments presented in FIG. 2 address a performance relevant gap management. Due to manufacturing related geometrical tolerances, a bondline gap 14 can occur that can be compensated by using the fiber composite material 10 of the disclosure herein. The design options presented in FIG. 2 apply locally cured second regions 200 to compensate for manufacturing tolerances or to close gaps 14 between the substructures 13a, b when manufacturing a composite structure 12. While first regions 100 in the respective substructures 13a, b to be joined are fully cured due to the curing properties provide in the resin of the polymer matrix 11 and the respective treatment (chemically and/or thermal) of the first regions 100. The second regions 200 remain plastic due to different curing properties of the polymer matrix material applied in the second regions 200. After contacting the second regions 200 of the substructures 13a, b and compensation of manufacturing tolerances or closing of gaps 14 the composite structure 12 is cured at a second temperature to ultimately join the substructures 13a, b. The embodiments in the upper part of FIG. 2 depict the situation with an overlapping and gap/tolerance compensation using the second regions 200 before I and after II joining the substructures 13a, b. In the embodiments shown in the lower part of FIG. 2 the second regions 200 are contacted by abutting the longitudinal ends 15a, b of the respective substructures 13a, b and a gap 14 compensation is effected by contacting the ends 15a, b of abutting second regions 200 with a further substructure 13c provide below the contacted second regions 200 of the first and second substructure 13a, b. The third substructure 13c has the same configuration as the embodiments shown in FIG. 1a with a second region 200 on the side facing the contact region 16 of the second regions 200 of the first and second substructure 13a, b. During gap 14 compensation III, the second regions 200 of the first and second substructure 13a, b, while still plastic are bend towards the third substructure 13c to contact the second region 200 in the third substructure 13c and to compensate a gap 14 as well as manufacturing tolerances. After contacting, the entire composite structure 12 is cured at a second temperature to trigger curing of the resin in the polymer matrix 11 in the second regions 200 thus forming the final composite structure 12 having gap 14 and manufacturing tolerances eliminated IV.

[0041] FIG. 3a to d present other design concepts of fiber composite material 10 and composite structures 12 using the same to achieve bonding in the various substructures 13a, b, c. FIG. 3a depicts substructures 13a, b, c having the first regions 100 and second regions 200 provided in a layered orientation of the fiber composite material 10. By contacting the second regions 200 of the substructures 13a, b, c and curing the composite structure 12 thus formed a tight bond between the substructures 13a, b, c can be achieved. The first and second regions 100, 200 have different curing properties that are either achieved by applying differing curing agents in the respective first and second regions 100, 200. While the first regions 100 comprise a resin in the polymer matrix 11 having an accelerating agent in the resin material, in the second regions 200 a decelerator is added to the resin as an additive. Due to this chemical adaptation, curing properties can be controlled to ensure curing of the first and second regions 100, 200, respectively in a timed matter and/or by applying a modified thermal gradient during curing. In the embodiment as depicted in FIG. 3b, the second regions 200 are provided in a dedicated areas of the substructures 13a, b thus allowing to adapt the design of the curable first and second regions 100, 200 to the specific needs set out by the configuration and design of the final composite structure 12 formed therewith.

[0042] FIG. 3c depicts a further embodiment of a composite structure 12 formed by joining substructures 13a, b having a design with each substructure 13a, b being provided with first and second regions 100, 200 having different curing properties. Whereas the first substructure 13a consist of a main part 17 consisting of or providing the first region 100, manufactured from a fiber composite material 10 with first curing property. Herein a fast-curing resin is used in the polymer matrix 11 that cures at a first condition or temperature or cures faster than the resin used in the second regions 200. The main part 17 further comprises second regions 200 formed on the inner sides 18 of extending portions 19a, b of the main part 17 and formed by a polymer matrix 11 having fibers embedded therein. The resin used in the polymer matrix 11 has decelerators added to set a second property during curing, i.e. a slower or later curing than the resin in the polymer matrix 11 of the main part 17. The uncured second regions 200 are contacted by the second region 200 of a second substructure 13b that is provide in a longitudinal extension with respect to the first already cured region 100 of the second substructure 13b. After insertion of the second region 200 of the second substructure 13b in the gap 14 formed in the main part 17, the second regions 200 of the main part 17 and the second region 200 of the second substructure 13b are contacted and joined by curing. During and after insertion and before curing covalent or chemical bonds are formed in the uncured second regions 200. Furthermore, diffusion of the resin molecules between the second regions 200 occurs. This supports tight and reliable bonding of the substructures 13a, b without the requirement of using additional adhesives to ensure proper bonding.

[0043] FIG. 3d presents a further option of joining substructures 13a, b, c consisting of uncured material with substructures 13a, b, c comprising first cured regions 100 and second uncured regions 200. The first substructure 13a consists entirely of a resin material in the fiber composite material 10 having a reduced curing speed and formed as a winded belt 20, whereas the second and third substructures 13b, c have the configuration as described in connection with the previous embodiments. After joining the second regions 200 of the substructures 13a, b, c the entire composite structure 12 is cured and hence the substructures 13a, b, c joint in a tight and reliable way, eliminating the requirement to provide second load paths in the structure by adding e.g. rivets or bolts in critical regions of the composite structure 12.

[0044] FIG. 4 presents a further design option that uses substructures 13a, b, having a layered configuration of first and second regions 100, 200. To join the substructures 13a, b, an intermediate layer 21 of uncured material, having the same or equivalent curing properties as the second regions 200 of the substructures 13a, b is interposed between the substructures 13a, b and co-cured with the second regions 200 thus forming a joining region or bondline between the substructures 13a, b. Before curing the intermediate layer 21 and the second regions 200 form covalent or chemical bonds. Furthermore, a diffusion of resin or matrix materials or molecules is initiated when contacting the intermediate layer 21 and the second regions 200. The bonding formed pre-curing are strengthened and fixed during curing to form the final composite structure 12.

[0045] FIG. 5 schematically depicts a section of a composite structure 12 according to an embodiment of the disclosure herein configured as a tank structure 30. By simplified illustration only a part of the tank structure 30 is presented herein. In this embodiment, the tank structure 30 has a cylindrical geometry, without being limited thereto. The tank structure 30 is in some circumstances used for the storage of liquid hydrogen (LH2) under cryogenic conditions and consists of a fiber composite material 10 or laminate such as laminate consisting of carbon fiber reinforced plastic CFRP, in particular when used in the aircraft industry due to the requirement of weight saving. Use of fiber composite materials 10 or laminates is preferred for aviation purposes due to high strength-to-weight ratios. Employing the fiber composite material 10 of the disclosure herein in the tank structure 30, the function of ensuring tightness of the tank structure 30 in particular in the bondline 32 between the dome part 33 and the cylindrical part 34 is brought by the fiber composite material 10 of the disclosure herein itself and does not have to be incorporated in an extra step during manufacturing. Any tolerance compensation in the overlapping area 35 is achieved by using the fiber composite material 10 of the disclosure herein having first and second regions 100,200 with different curing properties.

[0046] The tank structure 30 has a two-part configuration with a first part configured as a dome part 33 comprising a longitudinally protruding skirt portion 36 and a second part configured as a cylindrical part 34. The second part overlaps the first part in the skirt portion 36, after introduction of the first part into the second part. The first and the second part are manufactured from a fiber composite material 10 having a first region 100 fully cured due to enrichment of the resin of the polymer matrix 11 with an additive accelerating curing at a first curing condition i.e. curing temperature thus stabilising the geometry of the parts. A second region 200 is provided on the inner surface 31 of the cylindrical part 34 and the outer surface 37 of the dome part 33. These surfaces 31, 37 overlap during assembly. The uncured or semi-cured second regions 200 provide in the overlapping area 35 are contacted during assembly and immediately form covalent/chemical bonds between the molecules of the resin in the polymer matrix 11 and diffusion occurs within the second regions 200. Having fully assembled the two parts, the tank structure 30 is cured and the resin in the polymer matrix 11 of the second regions 200 settle thus providing a tight and reliable bondline 32 between the two parts. The curing properties of the second regions 200 are modified to cure slower or at a curing temperature that is higher than the temperature applied to cure the first regions 100. Modification is achieved by adding decelerating additives to the resin. In the pre-curing or open phase of the resin tolerance compensation can be made and manufacturing accuracy and efficiency be further improved. The tank structure 30 provided eliminates the need to provide bolts or rivets passing through the skirt portion 36 since the bondline 32 is sufficiently reliable and tight due to chemical/covalent bonds established in the second regions 200 after curing.

[0047] The formation of second regions 200 is not limited to the bondline 32 but can also be applied to the entire overlapping area 35 of the two parts forming the final tank structure 30. The tank structure 30 as described herein has several advantages. Since tank systems need to be segmented to enable system installation to the inner of the tank the method and fiber composite material 10 forming the tank structure 30 provide a safe and reliable joining technology and makes the use of thermosetting (TS) adhesive joining or thermoplastic (TP) welding, both not considered qualified to meet in particular aviation demands, obsolete. Furthermore bolting/riveting, undesirable as it perforates the tank, thereby being prone to leakage in the bolt area, is not required.

[0048] 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. The embodiments were chosen and described to best explain the principles of the disclosure herein and its practical applications, to thereby enable others skilled in the art to best utilize the disclosure herein and various embodiments with various modifications as are suited to the particular use contemplated.

[0049] While at least one example 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 example embodiment(s). In addition, in this disclosure, the terms comprise or comprising do not exclude other elements or steps, the terms a, an 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 SIGNS

[0050] 1 first step [0051] 2 second step [0052] 3 third step [0053] 4 fourth step [0054] 10 fiber composite material [0055] 11 polymer matrix [0056] 12 composite structure [0057] 13a, b, c substructure [0058] 14 gap [0059] 15a, b end [0060] 16 contact region [0061] 17 main part [0062] 18 inner side [0063] 19a, b extending portion [0064] 20 winded belt [0065] 21 intermediate layer [0066] 30 tank structure [0067] 31 inner surface [0068] 32 bondline [0069] 33 dome part [0070] 34 cylindrical part [0071] 35 overlapping area [0072] 36 skirt portion [0073] 37 outer surface [0074] 100 first region [0075] 200 second region