FR3068284A1 - Process for producing thermosetting composite components by forming fibrous preforms injected or infused - Google Patents

Process for producing thermosetting composite components by forming fibrous preforms injected or infused Download PDF

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Publication number
FR3068284A1
FR3068284A1 FR1756098A FR1756098A FR3068284A1 FR 3068284 A1 FR3068284 A1 FR 3068284A1 FR 1756098 A FR1756098 A FR 1756098A FR 1756098 A FR1756098 A FR 1756098A FR 3068284 A1 FR3068284 A1 FR 3068284A1
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France
Prior art keywords
resin
structural
preform
injected
forming
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
FR1756098A
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French (fr)
Inventor
Patrice Lefebure
Maxime Louis
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Airbus Group SAS
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Airbus Group SAS
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Filing date
Publication date
Application filed by Airbus Group SAS filed Critical Airbus Group SAS
Priority to FR1756098A priority Critical patent/FR3068284A1/en
Priority to FR1756098 priority
Publication of FR3068284A1 publication Critical patent/FR3068284A1/en
Pending legal-status Critical Current

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Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C70/00Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
    • B29C70/04Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts comprising reinforcements only, e.g. self-reinforcing plastics
    • B29C70/28Shaping operations therefor
    • B29C70/40Shaping or impregnating by compression not applied
    • B29C70/42Shaping or impregnating by compression not applied for producing articles of definite length, i.e. discrete articles
    • B29C70/46Shaping or impregnating by compression not applied for producing articles of definite length, i.e. discrete articles using matched moulds, e.g. for deforming sheet moulding compounds [SMC] or prepregs
    • B29C70/48Shaping or impregnating by compression not applied for producing articles of definite length, i.e. discrete articles using matched moulds, e.g. for deforming sheet moulding compounds [SMC] or prepregs and impregnating the reinforcements in the closed mould, e.g. resin transfer moulding [RTM], e.g. by vacuum
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C35/00Heating, cooling or curing, e.g. crosslinking or vulcanising; Apparatus therefor
    • B29C35/02Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould
    • B29C35/0222Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould the curing continuing after removal from the mould
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C70/00Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
    • B29C70/04Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts comprising reinforcements only, e.g. self-reinforcing plastics
    • B29C70/28Shaping operations therefor
    • B29C70/40Shaping or impregnating by compression not applied
    • B29C70/42Shaping or impregnating by compression not applied for producing articles of definite length, i.e. discrete articles
    • B29C70/46Shaping or impregnating by compression not applied for producing articles of definite length, i.e. discrete articles using matched moulds, e.g. for deforming sheet moulding compounds [SMC] or prepregs
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C70/00Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
    • B29C70/04Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts comprising reinforcements only, e.g. self-reinforcing plastics
    • B29C70/28Shaping operations therefor
    • B29C70/40Shaping or impregnating by compression not applied
    • B29C70/50Shaping or impregnating by compression not applied for producing articles of indefinite length, e.g. prepregs, sheet moulding compounds [SMC] or cross moulding compounds [XMC]
    • B29C70/52Pultrusion, i.e. forming and compressing by continuously pulling through a die
    • B29C70/523Pultrusion, i.e. forming and compressing by continuously pulling through a die and impregnating the reinforcement in the die

Abstract

The present invention relates to a method for producing a structural part (20) made of composite material by injection-infusion of a resin into a fibrous reinforcement, comprising in the following steps: a step (200) of injecting the resin into a flat textile preform (10); a step (300) of partial cooking of the injected-infused preform to a degree of crosslinking of the resin below a gelling point of said resin; a step (400) of forming the injected pre-infused preform until a final shape of the structural part is obtained; - A step (600) complete cooking off autoclave of the structural part formed to obtain a specific polymerization rate of the resin. The invention also relates to a structural part (20) made by the method.

Description

The present invention belongs to the field of manufacturing parts made of composite materials, it relates more particularly to methods of molding composites by injection-infusion of thermosetting resin.

The present invention applies more generally to the fields of textile composites, composite resin molding technologies by injection of liquid resin, processes for forming the composites and non-autoclave manufacturing techniques.

STATE OF THE ART

The composite molding processes by injection of liquid polymer resin (Liquid Composite Molding abbreviated as LCM in English terminology) represent an established class of techniques for the manufacture of structural or semi-structural parts in composite materials based on reinforced polymer resin. by a fibrous reinforcement.

The known variants of the LCM processes share the same principle: a liquid resin is injected into a mold in which a fibrous preform of dry fibers has been placed beforehand, after complete infusion of the preform, and after baking of the composite mixture, that is that is to say after final polymerization of the resin, which makes it possible to reach an optimal state of stiffening, a composite part is obtained and can be removed from the mold.

In the aeronautical and space industries, the manufacture of high performance composite structures molded by liquid injection relies on highly complex technologies which generate significant costs, in part because of the use of temperature resins (class 180 ° C). high glass transition compared to those used in the automotive industry for example, and the high demand in terms of health of the parts and respect for the geometry of the structures manufactured. In addition, these technologies are generally intended for parts with significant thicknesses.

These different aspects generally imply:

- A complex injection or infusion tool;

- Very long injection and cooking cycles;

- Final pressure cooking of the parts;

- Premature aging of the resin at room temperature in the case of single-component resins usually used in the aeronautical environment, hence the need for their storage in freezers before use;

- Manufacturing constraints due to the recovery of moisture from textile preforms and resin before injection or infusion.

In view of the complications listed below, it is necessary to perform certain steps in order to obtain good quality structural parts by LCM processes. It is mainly about:

- Draping of the different folds of the textile preform;

- Put in place the preform of the structural part to be manufactured, formed of textile folds, in the injection mold;

- Carry out a hot compaction, at medium to high temperature, of the 3D textile preform, which can be difficult, long and costly depending on the nature of the textiles used;

- Use injection molds of complex geometry, in blocks, in order to limit the effects of expansion of the parts, removal of the resin and possible leaks during the injection operation;

- Control the exothermic problems linked to thick parts;

- Check the thermal gradients in the case of large rooms;

- Systematically operate non-destructive checks on the parts manufactured, in order to detect any injection problem;

- Complete cooking, or post cooking, of the parts at high temperature, generally under pressure within the mold in order to limit the formation and growth of porosities in said parts;

- Control the cooling phase to avoid the appearance of significant residual thermal and mechanical stresses in the structure, which can lead to the creation of geometric defects or porosities and delamination.

Conventional LCM processes therefore have many limitations and major drawbacks in terms of efficiency and speed. It therefore appears essential in certain industries with high recurrent costs to adopt innovative processes which derive from the LCM process and which make it possible to reduce the manufacturing costs of the majority of structural parts produced in these industries.

PRESENTATION OF THE INVENTION

The main object of the present invention is to overcome the limitations of the prior art by simplifying the process and the production chain for structural parts made of composite materials by injection-infusion of liquid resin, while improving the quality of the parts produced and reducing the time and cost of production, and describes a process for producing a structural part in composite material by injection-infusion of a resin in a fibrous reinforcement.

The process is remarkable in that it comprises the following steps in order:

- an injection-infusion step of the resin in a flat preform;

- a partial cooking step of the injected-infused preform up to a rate of crosslinking of the resin below a gel point of said resin;

- a step of forming the pre-injected-infused preform until a final shape of the structural composite part is obtained;

- a complete baking step outside the autoclave of the structural part formed to obtain a determined rate of polymerization of the resin, making it possible to obtain optimal mechanical and thermomechanical properties.

Advantageously, the injection-infusion step of the resin in the planar preform is carried out at a low to medium temperature compared to a complete baking temperature of the structural part.

According to an advantageous embodiment, the thermosetting resin is polymerized at a rate, below a gelling point of the resin, of between 25% and 50% depending on the chemo-rheological behavior of the resin, at the stage of partial baking of the injected flat textile preform.

In addition, the partial firing step of the injected planar preform is carried out at a temperature equal to or close to an injection temperature of the resin in the injection step.

Similarly, the pre-baked preform is formed at a low to medium temperature compared to a complete baking temperature of the structural composite part.

For example, the complete cooking step outside the autoclave is carried out under vacuum in a conventional oven.

According to one embodiment, the method comprises a step of placing and compacting the planar preform before the step of injecting the resin into said preform, and a step of storing the structural part at ambient temperature, obtained after forming, before the complete baking step of said structural part.

Preferably the planar preform is of a textile nature, and the resin is a thermosetting resin.

The step of forming the injected preform is for example carried out using a press, or a diaphragm-type forming process, or continuous forming processes, such as pultrusion or roll-forming.

The invention also relates to a structural part made of composite material, of three-dimensional geometry, manufactured by the process as described.

Such a part can be a stiffener with an Ω, U, L, etc. profile, but also a spar, any beam, rib elements for example.

The fundamental concepts of the invention having just been exposed above in their most elementary form, other details and characteristics will emerge more clearly on reading the description which follows and with reference to the appended drawings, giving by way of 'nonlimiting example of embodiments of a process for manufacturing a part made of composite material and a part obtained by said process in accordance with the principles of the invention.

BRIEF DESCRIPTION OF THE FIGURES

The different figures and the elements of the same figure are not necessarily shown on the same scale. In all of the figures, identical elements have the same reference.

It is thus illustrated in:

Figure 1a: a perspective view of a planar preform according to the invention;

Figure 1b: a perspective view of a structural part obtained from the preform of Figure 1a by the method of the invention;

Figure 2: a diagram of the main steps of the method according to the invention; Figure 3: the process steps according to an embodiment of the invention;

DETAILED DESCRIPTION OF EMBODIMENTS

The present invention describes a new approach for carrying out the LCM process for the manufacture of a structural part made of composite material based on a resin, preferably thermosetting, and a fibrous reinforcement.

The method according to the invention is mainly intended for the manufacture of elements of substructures, for example stiffeners, of so-called stiffened structures, very common in the industry, and in particular in aeronautics and space construction. These structures provide the desired mechanical strength while limiting the size and total mass of the assemblies. They are thus commonly found in the form of stiffened composite panels in sections of aircraft fuselages, for example.

This application is only an example for the implementation of the method and cannot be limiting of the scope of the invention. The method as it will be described is easily transposable to the manufacture of other types of composite structural parts, not stiffened, in other industrial sectors.

In the following, any structural part made of composite material manufactured by an injection-infusion molding process of liquid resin will be designated injected-infused composite part, or LCM structure.

It should be noted that the expressions “pre-cooking” and “post-cooking”, as well as the expressions derived therefrom, can be used to denote partial cooking and complete or final cooking respectively.

The method makes it possible, starting from a fibrous reinforcement in the form of a planar preform 10, shown in FIG. 1a, to produce a structural part 20 of three-dimensional geometry, as shown in FIG. 1b.

The process for manufacturing an injected composite part, according to the invention, comprises the following main steps in order:

injection or infusion of thermosetting resin into a flat textile preform 10, accompanied by a pre-curing of the resin up to a median cross-linking rate, in which case we speak of semi-curing, this rate in fact makes it possible to confer on the preform injected sufficient dimensional and physicochemical stability to allow it to be handled in the workshop without damaging its integrity and to retain its formability properties, and nevertheless the ability to form new intermolecular bonds, in the event of subsequent assembly with another part composite whose constituent resin is chemically compatible;

- Forming of the injected-infused and semi-baked planar preform at low to medium temperatures compared to a temperature of the following stage, by a forming process of the thermoplastic composite sheet forming type;

- post-autoclave cooking of the injected-infused and semi-cooked part obtained up to a desired polymerization rate for the finished structural part.

The process, as schematically illustrated in FIG. 2, is therefore characterized by a preparation of semi-baked planar textile preforms which are then formed using tools and ad-hoc forming means, in order to take the final shapes of the parts. structural desired, the formed parts are ultimately post-fired to a determined resin polymerization rate.

This approach primarily avoids the use of 3D tools for compaction and injection. Indeed, the parts are first manufactured in the form of flat sheets before taking their three-dimensional shapes by a mechanical forming operation.

According to an embodiment of the invention, illustrated in FIG. 3, the method comprises the following steps in order, numbered according to the references in FIG.

- A step 100 of setting up in a tool and compacting a flat textile preform;

a step 200 of injecting resin under pressure into the flat textile preform at a low to medium temperature compared to the final baking temperature;

a step 300 of pre-cooking the injected planar preform, the injection being completed, at a temperature equal to or close to the injection temperature, up to a rate of crosslinking of the resin determined below the gelling point of said resin, 50% for example;

a step 400 of forming the planar preform injected and precooked obtained in the previous step, at a low to medium temperature;

- A step 500 of storing the injected part at room temperature before the final manufacturing step;

a step 600 of post-baking, outside the autoclave, of the precooked injected part until a determined polymerization rate.

Step 600 can be replaced by a step of assembling the semi-cooked LCM substructure obtained with a main structure of panel or skin type before a final post-baking of the assembly, as described in the French patent application having for title "Process for manufacturing structures in thermosetting composite materials by assembling composite elementary parts molded by injection of liquid resin infusion" and one of whose inventors is Patrice Lefébure.

In another embodiment, the injection step 200 is replaced by a step 210 of vacuum infusion of the resin into the planar preform for better cost reduction.

The pre-baking step 300 of the injected preform is preferably carried out up to a polymerization rate just below a rate corresponding to the gelling point of the resin, which is often close to 50% in the case of resin. epoxide. In this case, the resin is semi-cured.

In addition, the pre-cooking step 300 is carried out after injection or complete infusion, this condition corresponding to a transition A in the sequential diagram of the process given in FIG. 3.

The step 400 of forming the preform injected and precooked (LCM side) can be carried out using a press or any means for forming composite sheets, for example a diaphragm type system.

Rapid compaction in step 100 of compaction helps to limit training problems. In addition, if the compaction is carried out hot, the thermal inertia of the tool becomes negligible.

The process of the invention is characterized by a simple injection which does not require any tool of complex geometry, without fear of dry areas and problems of leaks during the injection.

The compacting, injection and pre-baking stages allow to reach a nominal quality and thickness at all points of the parts before the forming stage, which then makes it possible to improve the homogeneity of said parts, since the flow of resin is very limited.

The process also allows a significant gain in productivity, in particular thanks to the possibility of forming several pieces per day, the forming operations being generally quite rapid.

In addition, the temperatures, low to medium, of execution of the stages preceding the post-baking make it possible to drastically reduce the cost of using the auxiliary manufacturing products, compared to those used for the injection and baking of parts with high temperatures.

Other advantages emerge from the implementation of the process of the invention, such as for example the possibility of storing the parts at ambient temperature thanks to the pre-polymerized state of the resin, due to the weak effects of the sorption phenomena of water, and the physico-chemical stability of the material, before the forming and post-curing stages.

The LCM structural parts manufacturing process thus described can easily be used in a production site, thanks to the implementation of a specific assembly line, for the production of 3D geometry composite substructures for wing boxes, fuselages, wings and similar structures for example.

For optimal industrialization of the process, the assembly line must be divided into several stations and group together LCM molding, forming, post-baking operations, as well as the health control of the parts manufactured. Other operations can be added as needed.

After the injection and pre-baking steps, the structural parts obtained can be used to make stiffened structures, obtained by assembling parts made with composite skins for example.

Advantageously, the industrialization of such a process makes it possible to improve productivity, reduce tooling costs and auxiliary products, limit manufacturing waste, lower non-recurring costs thanks to the storage of parts at room temperature. , and to cancel the major investments in autoclaves.

One can also imagine, in the context of a gain in productivity, to subcontract to a supplier the manufacture of LCM semi-baked sheets before forming and final baking, due to the low added value of the in-house production of this preliminary step.

Claims (10)

1. Method for producing a structural part (20) of composite material by injecting a resin into a fibrous reinforcement, characterized in that it comprises the following steps in order:
- A step (200) of injection-infusion of the resin into a flat textile preform (10);
- a step (300) of partial baking of the injected-infused preform until a rate of crosslinking of the resin below a gel point of said resin;
- a step (400) of forming the pre-injected-infused preform until a final shape of the structural part is obtained;
- A step (600) of complete baking, outside the autoclave, of the structural part formed to obtain a determined polymerization rate of the resin, making it possible to acquire the desired mechanical and thermomechanical properties.
2. Method according to claim 1, wherein the step of injecting the resin into the planar preform is carried out at a temperature below a complete baking temperature of the structural part.
3. Method according to claim 1 or 2, wherein the resin is polymerized at a rate, below a gel point of the resin, between 25% and 50% in the partial firing step of the planar preform injected.
4. Method according to any one of the preceding claims, in which the step of partially cooking the injected planar preform is carried out at a temperature equal to or close to an injection temperature of the resin in the injection step. .
5. Method according to any one of the preceding claims, in which the pre-baked preform is formed at a temperature below a complete baking temperature of the structural part.
6. Method according to any one of the preceding claims, in which the complete cooking step without autoclave is carried out under vacuum in a conventional oven.
7. Method according to any one of the preceding claims, characterized in that it comprises a step (100) of placing and compacting the planar preform before the step (200) of injecting the resin into said preform, and a step (500) of storage at room temperature of the structural part, obtained after forming, before step (600) of complete baking of said structural part.
8. Method according to any one of the preceding claims, in which the resin is a thermosetting resin.
9. Method according to any one of the preceding claims, in which the step of forming the injected preform is carried out using a press or a diaphragm type process, or continuous forming type processes, such than a rolling-forming process or a pultrusion process.
10. Structural part (20) of composite material, of three-dimensional geometry, characterized in that it is manufactured by a process according to any one of the preceding claims.
FR1756098A 2017-06-30 2017-06-30 Process for producing thermosetting composite components by forming fibrous preforms injected or infused Pending FR3068284A1 (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
FR1756098A FR3068284A1 (en) 2017-06-30 2017-06-30 Process for producing thermosetting composite components by forming fibrous preforms injected or infused
FR1756098 2017-06-30

Applications Claiming Priority (1)

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FR1756098A FR3068284A1 (en) 2017-06-30 2017-06-30 Process for producing thermosetting composite components by forming fibrous preforms injected or infused

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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1621323A1 (en) * 2004-07-27 2006-02-01 Hexcel Composites GmbH Continuous pultrusion process for producing high performance structural profiles
US20160159057A1 (en) * 2014-12-05 2016-06-09 The Boeing Company Forming of staged thermoset composite materials

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1621323A1 (en) * 2004-07-27 2006-02-01 Hexcel Composites GmbH Continuous pultrusion process for producing high performance structural profiles
US20160159057A1 (en) * 2014-12-05 2016-06-09 The Boeing Company Forming of staged thermoset composite materials

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