FIELD
The present invention relates to a method of fabricating a textile structure of varying thickness that can be used particularly, but not exclusively, for making the fiber reinforcement of an aeroengine fan casing out of composite material (fiber reinforcement densified by a matrix).
BACKGROUND
As shown in FIG. 1, such a textile structure is made from a fiber texture 500 obtained by three-dimensional weaving between a plurality of layers of warp yarns or (twisted) strands in the longitudinal direction of the texture that are interlinked by weft yarns or strands in the transverse direction of the texture. On leaving the loom, the fiber texture presents a portion 501 of greater thickness and a portion 502 of smaller thickness. The fiber texture 500 is woven in “shape”, i.e. the ratio between the lengths of the warp yarns or strands is adapted to the profile of the final part. The portion of greater thickness 501 is made by using warp yarns or strands presenting a size or weight that is greater in that portion of the fiber texture than in the portion 502. On leaving the loom, the fiber texture is wound onto a storage mandrel 550 for transporting subsequently to a winder machine that is to wind the fiber texture onto an injection mold.
The fiber texture 500 is wound onto the mandrel 550 under tension. This winding under tension serves firstly to apply a little takeup tension on the warp yarns or strands for weaving, and secondly to apply a large amount of tension in the winding needed to debulk the preform. The tension exerted by the mandrel 550 on the fiber texture 500 should preferably be constant throughout weaving so as to avoid any undesirable stresses and deformations in the texture.
In order to keep tension constant and uniform over the fiber texture throughout its weaving, it is necessary to control the length of the warp yarns or strands taken up during weaving. When the fiber texture for winding is of varying thickness, it becomes difficult to control the length of the warp yarns or strands as winding progresses. As shown in FIG. 2, the taken-up length of the warp yarns or strands 510a present in the greater-thickness portion 501 increases more than the taken-up length of the warp yarns or strands 510b present in the smaller-thickness portion 502, with this effect itself increasing with increasing number of winding turns. Consequently, the ratio L510a/L510b of the length L510a of the warp yarns or strands 510a situated in the greater-thickness portion 501 over the length L510b of the warp yarns or strands 510b situated in the portion 502 is not constant throughout weaving and winding of the fiber texture 500.
SUMMARY
An aspect of the invention seeks to avoid such drawbacks, and for this purpose it proposes a method of fabricating a textile structure of varying thickness, the method comprising using a loom to weave a fiber texture in the form of a strip extending lengthwise along a longitudinal axis and widthwise along an axis perpendicular to the longitudinal axis, and winding the fiber texture under tension at the outlet from the loom onto a mandrel, the fiber texture including a greater-thickness portion presenting greater thickness, the method being characterized in that, during winding of the fiber texture on the mandrel, an interleaving element is interposed between adjacent turns of the fiber texture on the mandrel, the interleaving element extending in the width direction of the fiber texture over a portion of the texture that lies outside the greater-thickness portion and, over the portion of the texture situated outside the greater-thickness portion, it presents a thickness that corresponds at least to the difference between the thickness of said greater-thickness portion and the thickness of the portion of the texture situated outside said at least one greater-thickness portion. The interleaving element is made of a material that is deformable and waterproof. The material may in particular be an elastomer such as neoprene.
Thus, the method of an embodiment of the invention makes it possible to compensate for the thickness variation present in the fiber texture while it is being wound, thus avoiding any increase in the taken-up length of the warp yarns or strands in the greater-thickness portion compared with the taken-up length of the warp yarns or strands present in the portion(s) of texture situated outside the greater-thickness portion. Consequently, the ratio between the length of the warp yarns or strands present in the greater-thickness portion over the length of the warp yarns or strands present in the portion(s) situated outside the greater-thickness portion remains constant throughout the weaving and winding of the fiber texture.
An aspect of the invention also provides a textile structure of varying thickness comprising a fiber texture wound on a mandrel and including a greater-thickness portion presenting greater thickness, the structure being characterized in that an interleaving element is interposed between adjacent turns of the fiber texture on the mandrel, the interleaving element extending in the width direction of the fiber texture over a portion of the texture that lies outside the greater-thickness portion and, over the portion of the texture situated outside the greater-thickness portion, it presents a thickness that corresponds at least to the difference between the thickness of the greater-thickness portion and the thickness of the portion of the texture situated outside said greater-thickness portion. The interleaving element is made of a material that is deformable and waterproof, which material may in particular be constituted by an elastomer.
BRIEF DESCRIPTION OF THE DRAWINGS
Other characteristics and benefits of the invention appear from the following description of particular implementations of the invention given as non-limiting examples, with reference to the accompanying drawings, in which:
FIG. 1 is a diagrammatic perspective view showing a fiber texture of varying thickness being wound onto a storage mandrel in the prior art;
FIG. 2 is a diagrammatic section view showing the textile structure obtained after winding the FIG. 1 fiber texture;
FIG. 3 is a diagrammatic perspective view of a loom showing the weaving of a fiber texture of varying thickness;
FIG. 4 is a diagrammatic perspective view showing the fiber texture leaving the FIG. 3 loom and being wound onto a storage mandrel in accordance with an implementation of the method of the invention; and
FIG. 5 is a diagrammatic section view showing a textile structure obtained after winding the fiber texture in the manner shown in FIG. 4.
DETAILED DESCRIPTION
The invention applies in general to fabricating textile structures obtained from woven fiber textures having at least one portion of greater thickness, which fiber textures are made by three-dimensional weaving between a plurality of layers of warp yarns or strands and a plurality of layers of weft yarns or strands, and they are then wound onto a mandrel at the outlet from a loom.
As shown in FIG. 3, a fiber texture 100 is made in conventional manner by weaving using a Jacquard type loom 10 having arranged thereon a bundle of warp yarns or strands 20 in a plurality of layers, the warp yarns being interlinked by weft yarns or strands 30. The fiber texture is made by three-dimensional weaving. The term “three-dimensional” or “3D” weaving is used herein to mean a weaving technique whereby at least some of the weft yarns interlink warp yarns occupying a plurality of layers of warp yarns, or vice versa. An example of three-dimensional weaving is weaving with a so-called “interlock” weave. The term “interlock” is used herein of weaving to designate a weave in which each layer of warp yarns interlink a plurality of layers of weft yarns with all of the yarns in a given weft column presenting the same movement in the weave plane.
As shown in FIGS. 3 and 4, the fiber texture 100 is in the form of a strip that extends lengthwise in a direction X corresponding to the travel direction of the warp yarns or strands 20 and widthwise or transversely in a direction Y corresponding to the direction of the weft yarns or strands 30.
As shown in FIG. 4, the fiber texture 100 has a greater-thickness portion 101 of thickness that is different from that of a portion 102 of the texture that lies outside the portion 101. The greater-thickness portion 101 is obtained by using warp yarns or strands in this portion that are of greater size or weight than those in the portion 102. On leaving the loom 10, the fiber texture 100 is wound on a storage mandrel 50. The fiber texture 100 is wound onto the mandrel 50 under tension. For this purpose, the end 103 of the fiber texture is fastened to the mandrel 50, which is itself coupled to a rotary drive system (not shown in FIG. 4). Such winding under tension makes it possible firstly to apply low takeup tension on the warp yarns or strands for weaving, and secondly to apply high winding tension as is, needed for debulking the preform. The tension exerted by the mandrel 50 on the fiber texture 100 is, in an embodiment, constant throughout its weaving.
In accordance with an embodiment of the invention, and as shown in FIG. 4, an interleaving element, in this example a layer of elastomer 60 such as neoprene, for example, is placed on the fiber texture 100 from the beginning of winding the texture portion 102 that lies outside the portion 101. The elastomer layer 60 is in the form of a strip of width λ60 that extends in the Y direction corresponding to the axis of the mandrel 50 and that corresponds to the width λ102 over which the portion 102 extends. The length of the elastomer layer that extends in the direction X is determined as a function of the length of the fiber texture 100 that is to be wound onto the mandrel 50. The elastomer layer 60 presents a thickness e60 that corresponds to the difference between the thickness e101 of the greater-thickness portion 101 and the thickness e102 of the portion 102 of the texture that lies outside the portion 101, so as to fill in the thickness variation between the portions 101 and 102 during winding of the fiber texture.
FIG. 5 shows a textile structure 160 that results from winding a plurality of turns (six turns in the example shown) of the fiber texture 100 on the mandrel 50 with the elastomer layer 60 being interposed between adjacent turns of the texture 100 as described above. It can be seen that by interposing the elastomer layer 60, the warp yarns or strands of a same layer and present in each turn of the winding of the fiber texture 100 are all approximately at the radial distance from the rotational axis 50a of the mandrel 50. More precisely, a warp yarn or strand 30a situated in the greater-thickness portion 101 is located in each winding turn at the same level as a warp yarn or strand 30b situated in the portion 102 of the texture lying outside the portion 101. Consequently, the ratio L30a/L30b of the length L30a of the warp yarns or strands 30a situated in the greater-thickness portion 101 over the length L30b of the warp yarns or strands 30b situated in the portion 102 remains approximately constant throughout the weaving and the winding of the fiber texture 100.
The use of an elastomer layer as an interleaving element is beneficial in that it is easily deformable around the radius of the mandrel while presenting good resistance to compression in the thickness direction. The elastomer layer is easily manufactured to have a variety of shapes so as to match the shape and/or the varying thickness of the fiber texture.
The interleaving element used in the method of the invention for compensating the thickness difference in the fiber texture while it is being wound on the storage mandrel may be made using elements other than a layer of elastomer. In general manner, any element presenting at least the following properties can be used:
capacity for deforming to match the radius of the storage mandrel;
poorly or completely incompressible under the tensions applied in weaving; and
no risk of damaging fibers of the texture.
Patent Application
20170198421
