METHOD FOR JOINING THERMOSET COMPONENTS

Abstract

A method for joining one or more first-type thermoset components to a second-type thermoset component, each first-type thermoset component being manufactured by providing an uncured starting thermoset component on which a thermoplastic material layer is placed, such that an interpenetrating network forms between the thermoset polymer of the starting thermoset component and the corresponding thermoplastic material layer when each first-type thermoset component is cured; and each first-type thermoset component being then placed on an uncured second-type thermoset component so that when the latter is cured, a further interpenetrating network forms between each thermoplastic material layer and the thermoset polymer of the second-type thermoset component; this results in a strong joint between the first-type and the second-type thermoset components.

Claims

1. A method of joining thermoset components comprising the steps of: providing at least one first-type thermoset component, each at least one first-type thermoset component being manufactured by: providing a starting thermoset component, the starting thermoset component being uncured, placing a thermoplastic material layer on a surface of the starting thermoset component, the thermoplastic material layer having a thermoplastic glass transition temperature, curing the starting thermoset component at a first-type curing temperature, thus giving rise to the first-type thermoset component having, once cured, a filmed surface coated with the thermoplastic material layer, the thermoplastic material layer being joined to the first-type thermoset component by means of a first-type interpenetrating network; providing a second-type thermoset component, the second-type thermoset component being uncured; placing the filmed surface of each at least one first-type thermoset component on the second-type thermoset component; and curing the second-type thermoset component at a second-type curing temperature, so that a second-type interpenetrating network is created between the second-type thermoset component and each at least one thermoplastic material layer, thereby joining each at least one first-type thermoset component with the second-type thermoset component.

2. The method of claim 1, wherein, during the manufacturing of each at least one first-type thermoset component, the first-type curing temperature is less than the thermoplastic glass transition temperature of the thermoplastic material layer; and wherein the second-type curing temperature is less than the thermoplastic glass transition temperature of each at least one thermoplastic material layer.

3. The method of claim 1, wherein the at least one first-type thermoset component and/or the second-type thermoset component are composite materials.

4. The method of claim 3, wherein the at least one first-type thermoset component and/or the second-type thermoset component are carbon fiber reinforced polymers.

5. The method of claim 3, wherein the starting thermoset component of the at least one first-type thermoset component and/or the uncured second-type thermoset component are provided in form of uncured prepreg.

6. The method of claim 3, wherein the starting thermoset component of the at least one first-type thermoset component and/or the uncured second-type thermoset component are manufactured by using liquid composite molding.

7. The method of claim 1, wherein the thermoplastic material of the thermoplastic material layer is an amorphous thermoplastic.

8. The method of claim 7, wherein the amorphous thermoplastic is one of polyetherimide (PEI), polysulfone (PSU), polyether sulfone (PES), Poly(methyl methacrylate) (PMNIA) or polycarbonate (PC).

9. The method of claim 1, wherein the thermoplastic material layer is provided in a multi-layered film.

10. The method of claim 1, wherein an upper and a lower first-type thermoset components are provided, the filmed surface of the upper first-type thermoset component being placed on an upper surface of the second-type thermoset component and the filmed surface of the lower first-type thermoset component being placed on a lower surface of the second-type thermoset component opposite the upper surface.

11. The method of claim 10, wherein the second-type thermoset component is a pure thermoset resin.

12. The method of claim 1, wherein the at least one first-type thermoset component is an aircraft stiffener and the second-type thermoset component is an aircraft skin.

13. The method of claim 12, wherein the aircraft stiffener is a T-stringer.

14. The method of claim 1, wherein the at least one first-type thermoset component is an aircraft flap core and the second-type thermoset component is an aircraft flap.

15. The method of claim 1, wherein at least two first-type thermoset components are provided in form of at least two stacks of different thickness and the filmed surfaces of the at least two stacks of different thickness are placed on a flat surface of the second-type thermoset component.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0052] These and other features and advantages of the invention will become more evident from the following detailed description of preferred embodiments, given only by way of illustrative and non-limiting example, in reference to the attached figures:

[0053] FIG. 1 shows a starting thermoset component before being cured.

[0054] FIG. 2 depicts the first-type interpenetrating network that forms between the first-type thermoset component and the thermoplastic material layer when the former is cured.

[0055] FIG. 3 illustrates an uncured second-type thermoset component.

[0056] FIG. 4 shows the strong attachment between the first-type thermoset component and the second-type thermoset component due to the first-type interpenetrating network between the first-type thermoset component and the thermoplastic material layer and the second-type interpenetrating network between the second-type thermoset component and the thermoplastic material layer.

[0057] FIG. 5 depicts an upper and a lower first-type thermoset components before being joined to a second-type thermoset component.

[0058] FIG. 6 shows the strong attachment between the upper and the lower first-type thermoset components and the second-type thermoset component due to the upper and lower first-type interpenetrating networks respectively formed between the upper first-type thermoset component and the upper thermoplastic material layer and between the lower first-type thermoset component and the lower thermoplastic material layer, and due to the upper and lower second-type interpenetrating networks respectively formed between the upper thermoplastic material layer and the second-type thermoset component and between the lower thermoplastic material layer and the second-type thermoset component.

[0059] FIG. 7 is a representation of a piece of varying thickness obtained by the method of the invention.

[0060] FIG. 8 is a perspective view of an aircraft part manufactured with the method of the invention.

[0061] Figures from 9 to 12 illustrate the steps of reinforcing an aircraft skin with T-stringers using the method of the invention.

[0062] FIG. 13 represents an aircraft flap reinforced with aircraft flap cores made following the method of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0063] FIG. 1 shows an uncured starting thermoset component 11 that will be used to manufacture a first-type thermoset component 1 by curing such starting thermoset component 11. Before curing, a thermoplastic material layer 3 is placed on a surface of the starting thermoset component 11, such that, when the curing takes place, a first-type interpenetrating network 21 forms between the first-type thermoset component 1 and the thermoplastic material layer 3, as is depicted in FIG. 2. In consequence, the first-type thermoset component 1 comprises a filmed surface coated with the thermoplastic material layer 3, the thermoplastic material being strongly joined to the thermoset polymer of the first-type thermoset component 1 due to the first-type interpenetrating network 21 of their interface.

[0064] FIG. 3 illustrates an uncured second-type thermoset component 2 to be joined to the first-type thermoset component 1 of FIG. 2, as indicated in FIG. 4. A surface of the second-type thermoset component 2 and the filmed surface of the first-type thermoset component 1 are brought into contact, so that, when the second-type thermoset component 2 is cured, a second-type interpenetrating network 22 forms between the second-type thermoset component 2 and the thermoplastic material layer 3. As a result, the first-type 1 and second-type 2 thermoset components are strongly attached by means of the interpenetrating networks 21, 22.

[0065] In the embodiment of FIGS. 5 and 6, an upper 1 and a lower 1 first-type thermoset components are joined to the second-type thermoset component 2. Each one of the upper 1 and lower 1 first-type thermoset components is obtained by curing a starting thermoset component 11, as in the previous examplelikewise, before the curing, an upper 3 and a lower 3 thermoplastic material layer are each placed on a surface of the corresponding starting thermoset component 11 so that, once cured, the upper 1 and lower 1 first-type thermoset components each have a filmed surface coated with thermoplastic material respectively resulting from the formation of an upper 21 and a lower 21 first-type interpenetrating network with the upper 3 and lower 3 thermoplastic material layers.

[0066] In the present example, the filmed surface of the upper first-type thermoset component 1 is placed, before the step of curing the second-type thermoset component 2, opposite the filmed surface of the lower first-type thermoset component 1 relative to the second-type thermoset component 2, as shown in FIG. 6. This second-type thermoset component 2 can be used as a joining means to join already manufactured first-type thermoset components 1, 1, and it can be a pure thermoset resin. With this arrangement, when the second-type thermoset component is cured, an upper second-type interpenetrating network 22 is formed between the upper thermoplastic material 3 and the second-type thermoset component 2, and a lower second-type interpenetrating network 22 is formed between the lower thermoplastic material layer 3 and the second-type thermoset component 2.

[0067] In the embodiment of FIG. 7, there are also several first-type thermoset components joined to the second-type thermoset component 202, but in this case they are bonded to the same surface of the second-type thermoset component 102. The first-type thermoset components are stacks of different thickness 101, 101, 101 and the surface of the second-type thermoset component 102 to which they are bonded is a flat surface. This way, the method can be an advantageous way of manufacturing a piece with regions of varying thickness.

[0068] Before joining the stacks of different thickness 101, 101, 101 to the flat surface of the second-type thermoset component 102, these stacks 101, 101, 101 undergo the same making process of any first-type thermoset componenteach of the stacks 101, 101, 101 is first brought into contact with a thermoplastic material layer 103, 103, 103 and then cured so that a first-type interpenetrating network 121, 121, 121 forms between the thermoset polymer of the stacks 101, 101, 101 and the thermoplastic material of the layers 103, 103, 103.

[0069] Likewise, the step of joining of the stacks 101, 101, 101 to the second-type thermoset component 102 is carried out by placing the filmed surface of each stack 101, 101, 101 on the flat surface of the second-type thermoset component 102 and by curing this second-type thermoset component 102, thus forming second-type interpenetrating networks 122, 122, 122 between the thermoset polymer of the second-type thermoset component 102 and the thermoplastic material of the layers 103, 103, 103.

[0070] The inventive method can also be used for manufacturing aircraft parts having a skin 202 and one or more stiffeners 201 for reinforcing the skin 202, as depicted in FIG. 8. In such case, the process consists in first fabricating the stiffeners 201, which are first-type thermoset components, and then placing their filmed surfaces on the adequate surface of the skin 202, which constitutes the second-type thermoset component. As always, the final step comes down to curing the skin 202 for achieving the strong joint between the thermoset components.

[0071] This embodiment is detailed in figures from 9 to 12 for the example wherein the stiffeners are T-stringers 202. A starting thermoset T-stringer 211, represented in FIG. 9, is provided uncured, as any starting thermoset component. A thermoplastic material layer 203 is placed on a flat surface of a base of the starting thermoset T-stringer 211.

[0072] In the next step, shown in FIG. 10, the starting thermoset T-stringer 211 is cured, giving rise to a first-type interpenetrating network 221 that strongly joins the thermoset polymer of the T-stringer 201, which is a first-type thermoset component, and the thermoplastic material layer 203.

[0073] In the step of FIG. 11, the flat filmed surface of the cured T-stringer is placed on an uncured aircraft skin 202, playing the role of second-type thermoset component.

[0074] As illustrated in FIG. 12, when the step of curing the skin 202 is performed, a second-type interpenetrating network 222 extends between the thermoplastic material layer 203 and the thermoset polymer of the skin 202, and therefore the skin 202 is strongly attached to the T-stringer by means of the first-type 221 and second-type 222 interpenetrating networks.

[0075] In FIG. 13, an aircraft flap 302 reinforced with aircraft flap cores 301 is depicted. The aircraft flap cores 301 are first-type thermoset components which result from the curing of a starting thermoset component 11 in contact with a thermoplastic material layer 3. These aircraft flap cores 301, manufactured independently and without the need of expensive tools, are then placed in the appropriate position between the spars 305 of the uncured aircraft flap 302. When this aircraft flap 302 is cured, the final reinforced piece is obtained and the strength of the attachment is determined by the first-type 21 and second-type 22 interpenetrating networks.

[0076] In all the depicted embodiments, the thermoplastic material layers 3, 3, 3, 103, 103, 103, 203 maintain their original solid shape -that is, the thermoplastic materials are kept in their glassy phasewhen the curing steps take place, since the first-type curing temperature or temperatures and the second-type curing temperature are inferior to the thermoplastic glass transition temperature of the thermoplastic material layer or layers 3, 3, 103, 103, 103, 203.

REFERENCES

[0077] 1. First-type thermoset component

[0078] 1. Upper first-type thermoset component

[0079] 1.Lower first-type thermoset component

[0080] 2, 102.Second-type thermoset component

[0081] 3, 103, 103, 103, 203.Thermoplastic material layer

[0082] 3.Upper thermoplastic material layer

[0083] 3.Lower thermoplastic material layer

[0084] 11.Starting thermoset component

[0085] 21, 121, 121, 121, 221.First-type interpenetrating network

[0086] 21.Upper first-type interpenetrating network

[0087] 21.Lower first-type interpenetrating network

[0088] 22, 122, 122, 122, 222.Second-type interpenetrating network

[0089] 22.Upper second-type interpenetrating network

[0090] 22.Lower second-type interpenetrating network

[0091] 101, 101, 101.Thermoset stacks of different thickness

[0092] 201.Aircraft stiffener

[0093] 202.Aircraft skin

[0094] 211.Starting thermoset T-stringer

[0095] 301.Aircraft flap core

[0096] 302.Aircraft flap

[0097] 305.Aircraft flap spar