Methods for manufacturing curved omega stringers and Z shaped stringers of composite material and for manufacturing a composite material stiffened panel with curvature

Abstract

A method for manufacturing curved composite material omega stringers, comprising: automatic tape laying-up in an ATL machine, an AFP machine or a FLU machine and automatic cutting of the contour, to achieve a straight preform with reinforcements; flat forming to obtain an omega shape on the straight preform to transform it into a straight omega shaped preform; and curve forming the straight omega shaped preform by placing it in a flexible tool comprising a longitudinally embedded stiff band and a laminate clamping arrangement, the laminate clamping arrangement being located in extreme positions of the flexible tool, the flexible tool being covered by a mechanical closing arrangement, such that a head of the straight omega shaped preform has reinforcements on both extremes, the reinforcements being held by the laminate clamping arrangement during the forming process, and afterwards the straight omega shaped preform is heated and transformed into a curved omega stringer.

Claims

1. A method for manufacturing curved omega stringers of composite material, that comprises the following steps: automatic tape laying-up in an ATL machine or in an AFP machine or in a FLU machine and automatic cutting of a contour, to achieve a straight preform with reinforcements, flat forming to obtain an omega shape on the straight preform to transform the straight preform into a straight omega shaped preform, curve forming the straight omega shaped preform in a forming process by placing the straight omega shaped preform in a flexible tool comprising a longitudinally embedded stiff band and laminate clamping means, the laminate clamping means located in extreme positions of the flexible tool, the flexible tool being covered by mechanical closing means, such that a head of the straight omega shaped preform has the reinforcements on both extremes, the reinforcements being held by the laminate clamping means during the curve forming, and afterward the curve forming, heating the straight omega shaped preform and transforming the straight omega preform into a curved omega stringer.

2. The method for manufacturing curved omega stringers of composite material, according to claim 1, wherein the flat forming step is performed in a press machine.

3. The method for manufacturing curved omega stringers of composite material, according to claim 1, wherein the flat forming step is performed in a hot forming system.

4. The method for manufacturing curved omega stringers of composite material, according to claim 1, wherein the laminate clamping means are abrasive means.

5. The method for manufacturing curved omega stringers of composite material, according to claim 4, wherein the abrasive means are made of abrasive paper.

6. The method for manufacturing curved omega stringers of composite material, according to claim 1, wherein the flexible tool is made of rubber.

7. The method for manufacturing curved omega stringers of composite material, according to claim 1, wherein the mechanical closing means is a vacuum bag.

8. The method for manufacturing curved omega stringers of composite material, according to claim 1, wherein the longitudinally embedded stiff band is a metal band.

9. The method for manufacturing curved omega stringers of composite material, according to claim 1, wherein the flexible member comprises a male tool used to transform the straight omega shaped preform into a curved omega stringer.

10. A method for manufacturing curved Z shaped stringers of composite material, comprising the steps of the method of claim 1, and an additional step in which the curved omega stringer is cut into two parts to obtain two curved Z shaped stringers.

11. A method for manufacturing a composite material stiffened panel with curvature, the panel comprising a skin, comprising the following steps: manufacturing at least one curved omega stringer according to claim 1, curing the at least one curved omega stringer, and integration of the at least one cured curved omega stringer with the skin to obtain a co-bonded composite material stiffened panel with curvature.

12. A method for manufacturing a composite material stiffened panel with curvature, the panel comprising a skin, comprising the following steps: manufacturing at least one curved omega stringer according to claim 1, integrating the at least one cured curved omega stringer with the skin, and co-curing the at least one cured curved omega stringer with the skin to obtain a co-cured composite material stiffened panel with curvature.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is schematic diagram of the method of the invention.

(2) FIG. 2 is a perspective view of the straight preform obtained in intermediate steps of the invention.

(3) FIGS. 3 and 4 show the flexible tool used in the method of the invention.

(4) FIG. 5 shows the assembly of the preform, the flexible tool and the vacuum bag.

(5) FIG. 6 shows the male tool for curve forming and the flexible tool with the preform.

(6) FIG. 7 shows a curved omega stringer manufactured according to the method of the invention.

(7) FIG. 8 shows the flexible tool with the laminate clamping means.

(8) FIG. 9 shows a Z shape stringer manufactured according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(9) In FIG. 1, the method for manufacturing curved omega stringers 1 of composite material of the invention is summarized. The main steps of this method are: automatic tape lay-up in an ATL machine or in an AFP machine or in a FLU machine and automatic cutting of the contour, after which a straight preform with reinforcements 7 is achieved, flat forming to get an omega shape on the straight preform to transform it into a straight omega shaped preform 2, and a curve forming step, to obtain a curved omega stringer 1.

(10) The omega stringer 1 with high curvature can be cured and then integrated with the skin of stiffened panels with curvature or an aircraft fuselage to get a cobonded part (as in current prior art processes), or it can be directly integrated with the skin to get a cocured part.

(11) The first step comprises an automatic tape lay-up and automatic cutting. The preform of omega stringer is laying up automatically by an ATL machine or an AFP machine or in a FLU machine and the contour is cut. Several preforms can be laying up at the same time and the preforms will be achieved after the cutting step. This saves recurrent cost and lead time.

(12) The plies in the 0° direction can only be located in the head of the stringer to be able to do the hot-forming process without wrinkles.

(13) The second step comprises a flat forming to get an omega shape 3 on the straight preform (see FIG. 2), transforming it into a straight omega shaped preform 2. A hot forming system can be used, or a press machine.

(14) The curve forming step allows to get the high curvature in the stringer. In this step, the straight omega shaped preform 2 is located in a flexible tool 4 (FIGS. 3 and 4) to be able to form the stringer without wrinkles or waves.

(15) The flexible tool 4 contains a longitudinally embedded stiff band 9 to avoid any deformation in the length of the head of the stringer and assure the correct geometry after the forming process.

(16) The flexible tool 4 can comprise two parts, as shown in FIGS. 3 and 4.

(17) The longitudinally embedded stiff band 9 can be a metal band.

(18) The stringer (as a straight omega shaped preform 2 at this stage) is placed in the flexible tool 4 and covered by mechanical closing means, preferably a vacuum bag 5, to create a rigid solid with vacuum and to avoid wrinkles (see FIG. 5).

(19) In addition, some laminate clamping means 8 are located in the extremes of the flexible tool 4 (see FIG. 8) to erase the waves or the wrinkles that appear in the extreme reinforcements 7 of the head of the stringer. The reinforcements 7 can be made with a stagger and longer than the laminate to be hold by the laminate clamping means 8 during the forming process.

(20) Preferably, the laminate clamping means 8 can be abrasive means; for instance, they can be made of abrasive paper.

(21) Then, it is heated up and transformed into a curved omega stringer 1 on the tool. It is necessary to have enough vacuum during the forming in order to avoid wrinkles.

(22) The abrasive means can be abrasive films and the flexible tool 4 can be made of rubber.

(23) Preferably a male tool 6 is used to transform the straight omega shaped preform 2 into a curved omega stringer 1 (see FIGS. 6 and 7).

(24) The curved omega stringers 1 manufactured according to the above described method can be cut into two parts to obtain two curved Z shaped stringers 10.

(25) A method for manufacturing a composite material stiffened panel with curvature, the panel comprising a skin, comprises the following steps: manufacturing at least one curved omega stringer 1 according to the above described methods, curing the at least one curved omega stringer 1, and integration of the at least one cured curved omega stringer 1 with the skin to get a cobonded composite material stiffened panel with curvature.

(26) Another method for manufacturing a composite material stiffened panel with curvature, the panel comprising a skin, comprises the following steps: manufacturing at least one curved omega stringer 1 according to the above described methods, integration of the at least one cured curved omega stringer 1 with the skin, and cocuring of the at least one cured curved omega stringer 1 with the skin to get a cocured composite material stiffened panel with curvature.

(27) Although the present invention has been fully described in connection with preferred embodiments, it is evident that modifications may be introduced within the scope thereof, not considering this as limited by these embodiments, but by the contents of the following claims.

(28) 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.