Method of fabricating both a woven fiber preform and a composite material part

Abstract

A method of fabricating a woven fiber preform that is impregnated with a matrix-precursor resin, the resin, in the raw state, presenting a glass transition temperature Tg.sup.0, includes: impregnating yarns or strands with the resin; feeding a loom with the impregnated yarns or strands maintained at a temperature in the range Tg.sup.0 to Tg.sup.0+10 C.; and weaving the yarns or strands in the loom in order to obtain the resin-impregnated woven fiber preform.

Claims

1. A method of fabricating a woven fiber preform that is impregnated with a matrix-precursor resin, said resin, in the raw state, presenting a glass transition temperature Tg.sup.0, the method comprising: impregnating yarns or strands with the resin; feeding a loom with the impregnated yarns or strands maintained at a temperature in the range Tg.sup.0 to Tg.sup.0+10 C.; and weaving the yarns or strands in the loom in order to obtain the resin-impregnated woven fiber preform.

2. A method according to claim 1, wherein the yarns or strands are made of carbon or of silicon carbide.

3. A method according to claim 1, wherein the resin is a thermosetting epoxy resin.

4. A method according to claim 1, wherein the resin-impregnated yarns or strands are present in a refrigerated enclosure feeding the loom with resin-impregnated yarns or strands.

5. A method according to claim 1, wherein the yarns or strands are woven by three-dimensional weaving.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Other characteristics and advantages of the present invention appear from the following description given with reference to the accompanying drawings, which show an implementation having no limiting character. In the figures:

(2) FIG. 1 is a highly diagrammatic view of an example installation for performing a method of the invention for fabricating a resin-impregnated woven fiber preform;

(3) FIGS. 2A to 2D show various steps in an example method of the invention for fabricating a composite material part; and

(4) FIGS. 3A to 3C show various steps in a variant method of the invention for fabricating a composite material part.

DETAILED DESCRIPTION OF THE INVENTION

(5) FIG. 1 is a highly diagrammatic view of an installation 1 for making a resin-impregnated fiber preform 10. The installation 1 comprises a loom 20, e.g. of the Jacquard type, and an enclosure 30 situated upstream from the loom (in the travel direction of the yarns for weaving going towards the loom). Rolls 40 of yarns or strands 41 that are pre-impregnated with resin are stored inside the enclosure 30. The enclosure 30 has an opening 31 allowing the yarns or strands on the rollers 40 to be fed to the loom 20. In accordance with the invention, the temperature inside the enclosure 30 lies in the range from the glass transition temperature Tg.sup.0 of the resin in the raw state to Tg.sup.0+10 C. such that the yarns or strands 41 that are fed to the loom 20 are at the temperature of the enclosure 30.

(6) In a variant that is not shown, the installation may comprise the loom 20, the rollers 40, and an enclosure cooled to a temperature lying in the range Tg.sup.0 to Tg.sup.0+10 C. in which the loom 20 and the rollers 40 are present.

(7) Still in a variant that is not shown, the yarns or strands 41 may be dry on the rollers 40 and may pass through a bath of resin while they are being conveyed to the loom so as to impregnate them with resin before they are woven. Under such circumstances, care should be taken that the impregnated yarns or strands are at the right temperature before being woven.

(8) The yarns or strands 41 may be made of carbon, of ceramic such as silicon carbide SiC, of glass, or indeed of aramid. The resin may be selected from epoxy resins, and it may possibly include additives for increasing its toughness.

(9) In order to obtain a resin-impregnated woven fiber preform, the pre-impregnated yarns or strands 41 coming from the rollers 40 stored in the enclosure 30 are woven by using the loom 20. The temperature at which said yarns or strands 41 are maintained enables them to be woven without clogging the loom 20 since the resin is neither too brittle nor too liquid or sticky. As mentioned above, the weaving may be three-dimensional, but it could equally well be multilayer or two-dimensional. In the example shown, the three-dimensional weaving may be weaving with an interlock weave, in known manner. Other known types of multilayer weaving could be used, such as in particular those described in Document WO 2006/136755.

(10) An example of a method of the invention for fabricating a composite material part is described below with reference to FIGS. 2A to 2D.

(11) After obtaining a fiber preform 10 that has been woven and that is impregnated with resin as described above, the preform 10 is trimmed and yarns projecting out from layers are cut away, and then the preform 10 is positioned in a mold 50. The mold 50 that is shown diagrammatically in the figures comprises a support-forming portion 51 and a countermold 52 that between them define a hollow cavity 53 in which the preform 10 is placed. The cavity 53 presents a shape and dimensions that correspond to the part that is to be fabricated. The part forming the support 51 in this example has gaskets 54 to provide the mold 50 with sealing when it is closed. In the example shown, the mold 50 also has a vent 55.

(12) Thereafter, the mold 50 may be closed progressively, as shown in FIG. 2B. Beforehand, after or during closure of the mold 50, the preform 10 is heated to the softening temperature of the resin. When the mold 50 is closed in sealed manner and the resin present in the preform 10 has softened or liquefied, it is then possible to eliminate the air present in the cavity 53 by pumping a vacuum. In this example, air is evacuated from the cavity 53 via the vent 55. After these steps, a preform 10 is obtained that is impregnated with resin throughout all of its internal pores and that is exempt from bubbles of air.

(13) Thereafter, a compacting pressure may be applied on the mold 50 in order to shape the preform and expel surplus resin present in the preform, as shown in FIG. 2C. This surplus may be removed via the vent 55 by means that are not shown. In addition, it is possible to maintain a uniform pressure inside the cavity 53 by reinjecting a fraction of the resin that has been removed during compacting.

(14) Finally, the mold 50 is heated, preferably in uniform manner, so as to initiate polymerization (curing) of the resin present in the preform 10 and densify the preform 10 (FIG. 2D). After curing, this produces a composite material part that can subsequently be unmolded and on which it is possible to perform finishing operations.

(15) Another implementation of a method of the invention is shown in FIGS. 3A to 3C.

(16) In this implementation, the mold 50 is placed in a sealed enclosure 60 that is provided with a vent 61. Unlike the implementation shown in FIGS. 2A to 2D, the air present in the impregnated preform 10 is eliminated by evacuating the enclosure 60 (FIG. 3A) and not directly by evacuating the inside of the closed mold 50. As a result, the mold 50 may be closed after the step of eliminating the air present in the preform 10. As above, the mold is then closed, and a compacting pressure is applied on the mold 50 (FIG. 3B) in order to shape the preform and expel the surplus resin. Finally, the mold 50 is heated in order to polymerize the resin, densify the preform 10, and obtain the final part (FIG. 3C).

(17) The part can then be unmolded.

(18) The method of the invention for fabricating a composite material part is shown above by using a mold comprising a portion forming a support and together with a countermold. It should be observed that in a variant it is possible to use other known means for densifying the preform, for example an installation having a vacuum diaphragm arranged in an autoclave.

(19) In the present disclosure, the term lying in the range . . . to . . . should be understood as including the bounds.

EXAMPLE

(20) An aviation turbine engine fan blade is to be fabricated out of organic matrix composite material by a method of the invention. The following steps are performed in succession: impregnating carbon fiber strands with a resin sold under the reference HexPly 8552 from the supplier Hexcel, the glass transition temperature Tg.sup.0 of the resin in the raw state as given by its manufacturer and as obtained by DSC being about 4 C. (3.95 C.); placing strands in the form of a roll in a chest refrigerated to 0 C., the chest having openings allowing a loom to be fed with said strands; weaving the strands maintained at 0 C. in the loom by three-dimensional weaving so as to obtain a resin-impregnated woven fiber preform for a blade; optionally using shears to cut the woven preform; placing the preform in the cavity of the mold having the shape of the blade that is to be fabricated; heating the mold to a temperature of 100 C. in order to soften the resin; closing the mold and evacuating the inside of the cavity so as to remove the air present in the preform; applying a compacting pressure on the mold in order to shape the preform and impart uniform pressure within the mold cavity, possibly reinjecting resin that has been discharged from the preform during this step, should that be required; heating the mold up to 110 C. for 150 minutes after a progressive rise in temperature in order to polymerize the resin; unmolding the resulting blade; and optionally performing finishing operations.