Patent Description:
It is known to use composite materials comprising a matrix reinforced with fibre reinforcement material such as carbon fibre for components to provide a desirable combination of properties, such as strength and low weight.

Woven structures of fibre reinforcement material have been proposed for use in the manufacture of composite components, owing to improved properties relating to structural integrity. It is known to use multi-layer (or 3D) weaves, formed by weaving with multiple layers of warp yarn, for providing through-thickness structural integrity to a woven structure.

Looms can be used to make woven structures and can be controlled to separate respective sets of warp tows to define an opening for insertion of a weft tow between them. For example, a set of warp tows may be lifted to an upper side of the opening so as to pass over the weft tow, whereas another set may extend below the opening so as to pass under the weft tow. Automatic looms, which may be computer controlled, are known for creating diverse multi-weave structures.

<CIT> discloses an "Integral Textile Structure for <NUM>-D CMC Turbine Airfoils". It also teaches of the potential difficulties in forming a suitable CMC Airfoil, such as how to form cooling holes and the potential for internal rupture of the structure if inadequate interlacing is performed.

According to various aspects of the disclosure, there is provided a woven structure, a related method for manufacturing a composite component, and a non-transitory computer-readable medium, as set out in the appended claims.

The expression "tow" as used herein refers to a bundle of fibre reinforcement material. In the context of a woven preform or woven structure, the tow is the smallest element of the weave structure to be manipulated to form the weave (as the individual fibres are not manipulated independently of each other). The tow weight as described herein may be characterized by the weight per unit length or by the number of fibres. The tow weight may be variable or may be constant between tows.

A woven preform as described herein is an intermediate product in a composite manufacturing process, for subsequent forming into a near net shape for the component by resin infusion (e.g. resin transfer moulding) and curing etc. The woven preform may be "pre-preg" (i.e. may comprise pre-impregnated fibre reinforcement material).

A woven structure as described herein encompasses both a woven preform and a formed component having a corresponding woven structure. In this invention, all examples of a composite component comprise a woven structure. The expression "component" implies that the woven structure has been formed to the near net shape for the component (and/or finished to adopt the net shape of the component). Net shape is the intended geometry of the component, and is a term of the art.

A composite component comprising a woven structure as described herein may be provided, based on a woven preform, by any suitable method. Example methods include a resin transfer moulding (RTM) process in which a matrix material (such as an epoxy resin or any other suitable matrix material as are known in the art) is infused in the woven structure to provide a composite component of matrix material and fibre-reinforcement material.

As is known in the art, different weaves (i.e. different weave patterns or designs) can be used to achieve different properties of a woven structure. For example, weaves with relatively more interlacing between warp and weft tows may generally be more stable and less compliant to adopt different shapes, whereas weaves with relatively less interlacing between warp and weft tows may generally be less stable and more compliant. Such interlacing tends to result in crimping of tows as they pass under or over the respective other tow, and each crimping location may increase a resistance to relative movement between tows (e.g. by elevated friction). As a simple example, "satin" weaves have a relatively high float number (the number of tows of one type over which a tow of the other type extends between interlacing or crimping locations) compared to some other weave types such as a plain weave. Such "satin" weaves therefore have a reduced stability and are more compliant, and are known in the textile industry to provide an improved drape (i.e. being compliant to conform easily to a shape). Similar concepts apply to more complex structural weaves, including multi-layer weaves. While the expression "stability" is used in the relevant art to refer to the compliance of a weave structure, for the purposes of this invention it may be considered to be interchangeable or equivalent to a stiffness or flexural rigidity (as may be assessed by reference to a flexural modulus or bending modulus of elasticity).

In a multi-layer weave, there are multiple layers of weft tows extending along a weft direction and layered in a thickness direction of the weave, with warp tows extending along a substantially orthogonal warp direction at respective locations along the weft direction.

To aid the further discussion of multi-layer weaves, selected weave terminology is discussed below with reference to <FIG> (comprising Figures 1a-1f). <FIG> shows an example multi-layer woven structure <NUM> comprising a plurality of stacks S which extend along a longitudinal direction P and each have a notional width along a weft direction F, each stack having one or more warp tows A (as shown in <FIG>) which extend along the longitudinal direction within the respective stack (in superposition if there are multiple warp tows). The longitudinal direction may be interchangeably referred to as a warp direction in the present invention. <FIG> shows a cross-sectional slice of the woven structure <NUM> normal to the warp direction P at a longitudinal position, and shows that the woven structure <NUM> further comprises a plurality of weft tows E extending along a weft direction F. The weft tows E are layered in a thickness direction T of the weave, and in this example are provided in a plurality of weft tow layers, each weft tow layer comprising an array of weft tows distributed along the longitudinal direction of the weave so that respective tows are in superposition at respective longitudinal positions.

Each location along the weft direction F occupied by one or more warp tows A superposed on each other through the thickness direction T is referred to herein and in the art as a "stack" S, such that there are a plurality of stacks S defined along the weft direction F by respective sets of one or more warp tows A. A suitable configuration of stacks S in a multi-layer weave is to provide an alternating arrangement of warp (or non-binding) stacks W and binding stacks B, with binding stacks B being stacks in which the or each warp tow A is interlaced with weft tows E (i.e. moving between layers of weft tows, or moving between warp tow positions defined between such layers) to bind the weft tows E, whereas warp (or non-binding) stacks W are stacks in which the or each warp tow A extends without interlacing with weft tows E (e.g. remaining between the same two layers of weft tows E, or remaining at the same warp tow position).

As shown in <FIG>, in a multi-layer weave the interlacing of weft tows means that along the longitudinal direction, the position of each warp tow moves between weft tow layers. Accordingly, at any particular longitudinal direction the upper and/or lower warp tows may not extend over (i.e. on an outer side of) the uppermost or lowermost weft tow respectively. This is manifested in <FIG>, which shows a pattern of unoccupied gaps for warp tows in binding stacks, corresponding to a weave pattern for the binding stacks as will be further described below.

Various stack arrangements are shown in <FIG>, each of which show cross-sectional slices of the woven structure <NUM> normal to the weft direction F at lateral positions along the weft direction F (which extends into the page). In order, there is shown a first binding example stack B1, a second example binding stack B2, a first example warp (or non-binding) stack W1, and second example warp (or non-binding) stack W2.

In the binding stacks B1 and B2, one or more warp tows A extends through the thickness direction T of the woven structure between opposing sides to define a multi-layer weave pattern. In the first binding stack B1, the multi-layer weave type is a layer-to-layer angle interlock weave comprising seven binding warp tows A which extend through eight weft tow layers E. In the second binding stack B2, the multi-layer weave type is an orthogonal through-thickness weave having a float number of four, meaning that the (single) binding warp tow A extends through the thickness (in this example eight layers of weft tows E) in the thickness direction T of the woven structure, and passes in the warp direction P over four weft tows E before returning. A further example of a through-thickness weave (comprising a single binding warp tow) is through thickness angle interlock weave, as is known in the art.

In contrast, in the first example warp stack W1, the warp tows A extend along the warp direction P at constant warp tow positions with respect to the thickness direction T of the weave (i.e. each warp tow position being a position defined between adjacent weft tow layers). As such, there is no binding between the warp A and weft tows E, and the stack may be termed a "non-binding" stack.

In the second example warp stack W2, the warp tows A are generally arranged as in the first warp stack W1, with the exception of a centrally-located warp tow A2 which is interlaced between two adjacent warp tow positions. Nevertheless, this warp tow does not act to bind two adjacent weft tow layers together, and so may be considered to be non-binding. In the present invention, a stack in which a majority of the warp tows are non-binding may be considered a non-binding stack.

An example apparatus which may be used for manufacturing a woven structure as disclosed herein comprises a warp tow supply and a loom. The warp tow supply is configured to supply warp tows A to the loom for weaving with weft tows E at a weave location of the loom. The warp tow supply may comprise a plurality of separate tow supply feeds (e.g. separate tow spools on a creel) each configured to independently supply separate warp tows A to the weave location of the loom.

The loom is configured to weave a woven structure, at a weaving location of the loom, using the warp tows A supplied in a longitudinal direction (corresponding to the warp direction P) from the warp tow supply and weft tows E supplied along a generally transverse direction (corresponding to a weft direction F) at the loom. The loom may be of any suitable type as is known in the art, suitable for weaving a multi-layer woven structure. For complex weaves the loom may be programmable (i.e. configured for computer control) to form woven structures with weave patterns based on computer-readable instructions. Such a loom may be referred to as a computer-controlled jacquard loom. The apparatus comprises a loom controller for controlling the loom to weave the woven structure.

As is known in the art, a loom can be controlled to separate respective sets of warp tows A to define an opening for insertion of a weft tow E between them. For example, a set of warp tows A may be lifted to an upper side of the opening so as to pass over the weft tow E, whereas another set may extend below the opening so as to pass under the weft tow E. After insertion of the weft tow E, the same or different sets of warp tows A can then be repositioned to define another opening for reception of a weft tow E.

The woven structure produced by the loom may be referred to herein as woven preform to reflect that it forms an integral part of the component but must be formed to shape and subsequently cured with matrix material (e.g. by a resin transfer moulding (RTM) technique) to form the component.

The woven preform may be referred to herein as having a longitudinal direction corresponding to the path along which it is discharged from the loom, and a lateral direction orthogonal to the longitudinal direction and extending across the woven preform. The longitudinal direction may correspond to the warp direction P of the woven preform (i.e. along which warp tows generally extend). The lateral direction may generally correspond to a weft direction F of the woven preform, while acknowledging that weft tows E may depart from a direction that is precisely orthogonal to the longitudinal and/or warp directions. The weft tows E are interwoven with warp tows A at multiple lateral positions along the weft tows E.

The examples will be described by reference to a component for a gas turbine engine, in particular a stator vane and/or stator vane segment. It will be appreciated that the invention herein may be applicable to other gas turbine engine and aerospace components, or other components in other fields.

It will be appreciated that a woven structure as described herein is implemented in a woven preform and wholly or substantially maintained in a composite component comprising the woven structure and a matrix material (considering that trimming processes may be applied to the woven preform), and as such the following description is with reference to a woven structure per se, rather than with reference to a particular stage of manufacture.

As described herein, a woven preform according to the invention may be suitable for forming a complex component. The invention envisages a woven preform comprising multiple adjacent portions which are longitudinally-separated (i.e. along the warp direction P), with each portion corresponding to a respective part of a complex component. The plurality of adjacent longitudinally-adjacent portions may each have a set of common warp tows extending through the plurality of portions. By varying the weave type and thickness of the interlayer weave between the portions, the respective portions can be configured to have different properties suitable for forming the respective parts of the component. The regions where longitudinally adjacent portions meet may be referred to herein as junctions. This invention provides teaching relating to forming a complex product with one or more junctions between members.

As will be described in further detail below with respect to specific examples, each portion of a woven preform according to the invention may have a single free leaf, or two or more free leaves in superposition. Each free leaf may comprise a multi-layer weave and is free to separate from another free leaf of the same portion throughout the longitudinal extent of the portion.

The woven preform may be configured to transition from a generally flat shape (as produced by the loom) to a forming shape in which the portions deflect from their woven configuration to adopt a near net shape of component. The woven preform may comprise a primary portion comprising a single free leaf and a secondary portion comprising two free leaves. The two free leaves of the secondary portion may be separated to form a near net shape for the component.

In this way, an integrated complex structure having a 3D weave can be formed, without the need for joining/attachment processes to join respective sections.

Referring now to <FIG> (comprising <FIG>), a woven structure <NUM> for a stator vane with root and tip platforms will be described. <FIG> shows a cross section through the woven structure <NUM>, normal to a lateral or weft direction. The woven structure <NUM> comprises a primary portion <NUM> and two secondary portions <NUM>, <NUM>. The primary portion <NUM> corresponds to an aerofoil section of the vane, and the secondary portions <NUM>, <NUM> each correspond to a platform (such as a tip and a root of the vane respectively). The primary portion <NUM> and the secondary portions <NUM>, <NUM> meet at junctions <NUM> along a longitudinal direction of the woven structure. Although the primary portions <NUM> and the secondary portions <NUM>, <NUM> are shown at meeting at an angle at the junctions <NUM> (for ease of showing the different portions in the Figures), it will be understood that the woven structure <NUM>, after being formed by the loom, is a substantially planar arrangement.

The primary portion <NUM> may be solid or hollow, and may be a shell portion as will be described in further detail below.

In this example, the primary portion <NUM> comprises a single free leaf. The cross-section of <FIG> shows what appears to be two leaves of the primary portion that are not joined at the respective lateral position of the cross-section. However, as will be discussed below, the primary portion is actually made of a single free leaf, and what <FIG> shows is two sections of the same free leaf. The two sections are joined in the primary portion out of the plane of the figure (e.g. at edges of the primary portion not shown in the cross-section of <FIG>). Therefore the primary portion <NUM> of this example does not comprise a plurality of free leaves, but rather a single free leaf.

The secondary portions <NUM>, <NUM> each comprise two free leaves 204a, 204b, 206a, 206b. The expression "free leaf" or "free leaves" is used to indicate that the respective elements of the woven structure are separable from one another at locations away from the junction <NUM>, despite being woven at the same longitudinal position of a woven preform using a multi-layer weave. Unlike the primary portion <NUM>, the free leaves 204a, 204b, 206a, 206b at each secondary portion <NUM>, <NUM> are not joined to each other.

<FIG> shows a cross-section of the woven structure <NUM> after a shaping process to adopt a near net shape for the component. In this drawing, the two leaves of the primary portion <NUM> are shown in the figure as being separated along a thickness direction at the lateral location of the cross-section (but as explained previously, they are actually joined elsewhere in the primary portion, as will be discussed further below). The free leaves of the secondary portions <NUM>, <NUM> have been shaped to adopt a near net shape of the respective platforms (the tip and root section respectively) of the vane.

As shown in <FIG> (comprising <FIG>), the woven structure <NUM> as shown in <FIG> may be part of a woven structure <NUM> comprising a repeating unit which is joined end-to-end in a continuous woven structure. In this way it will be understood that a section comprising a plurality of vanes can be made from a single woven preform.

For instance, the woven structure <NUM> shown in <FIG> comprises two woven structure units <NUM>, each of which corresponds to the woven structure described above with reference to <FIG>. As above for <FIG>, it will be understood that the woven structure <NUM>, when formed by the loom is substantially planar, and the junctions are only shown here at angles for ease of reference to each adjacent section.

To form the woven structure <NUM> into the near net shape as shown in <FIG>, the woven structure <NUM> can be cut at a cut point <NUM>, whilst remaining attached at a join point <NUM>. The top half (or one longitudinal end portion) of the woven structure <NUM> (comprising a single woven structure unit <NUM>) can then be moved relative to the lower half of the woven structure <NUM> (e.g. in the direction of the arrow A), and the two leaves of each of the secondary portions can be separated as described above. If the upper portion of <FIG> corresponds to a tip of the vane and the lower portion corresponds to the root, then it will be appreciated that to form a continuous root platform between the two units only requires a single join between distal ends of opposing free leaves of the secondary portions <NUM>, <NUM>, at a new lower join point <NUM>. In this way, the woven structure <NUM> is formed into a near net shape for a complex component in which two members (e.g. two vanes) extend between two support structure (e.g. two platforms), as shown in <FIG>.

Although the woven structure <NUM> shows only two such woven structure units <NUM> and corresponds to only two vanes, it will be understood that, by repeating the structure <NUM> in a longitudinal direction and cutting at suitable cut regions on alternating sides of the woven structure <NUM>, a vane segment comprising any number of multiple vanes can be formed by "unfolding" the woven structure units in a "concertina" fashion.

In some examples, the vane may be a ribbed vane (i.e. with one or more support beams bridging the aerofoil surfaces). The rib may only extend along a mid-portion of the span, thereby terminating in the respective primary portion <NUM> before the respective junctions <NUM> with secondary portions <NUM>, <NUM> that form the respective platforms. This may avoid forming defects that could occur in a transition between a platform (such as a root or tip) and fully-ribbed vane.

In this example, each of the primary and secondary portions <NUM>, <NUM>, <NUM> of the preform <NUM> comprises a multi-layer weave structure. Examples of multi-layer weave structures which may provide these properties will now be described with reference to <FIG> (comprising <FIG>).

In the secondary portions of a preform <NUM> as described above, binding warp tows A in binding stacks of the weave may only extend between warp tow positions associated with the respective leaf, such that the leaves are not interwoven and remain separable. Two examples of such weave structures are shown in <FIG>, in which the two leaves of each example <NUM>, <NUM> are marked 402a, 402b, 404a and 404b respectively. It can be seen that each binding stack for the respective pairs of leaves 402a, 402b, 404a, 404b has two separate sets of one or more binding warp tows A associated with respective halves of the woven structure corresponding to the leaves. Each set of binding warp tows A extend between warp tow positions across the entire thickness of the respective leaf to bind the respective weft tows, but do not transition into warp tow positions associated with the other half (i.e. the other leaf). This permits the respective leaves to be separatable after weaving.

In the first example <NUM>, the leaves 402a, 402b each comprise an orthogonal through-thickness weave (where the expression "thickness" in this instance refers to the thickness of the leaf, not the woven structure as a whole) extending through the thickness (in this example four layers of weft tows E), with a float number of four (i.e. extending over four weft tows E before returning, as described above with respect to <FIG>). In the second example <NUM>, each leaf 404a, 404b comprises a layer-to-layer angle interlock weave for three binding warp tows A through four layers of weft tows E, as described above for <FIG>. It will be appreciated that other binding stack arrangements may be used, and that each leaf 402a, 402b, 404a, 404b may comprise different types of weave, or a different number of warp tows A or weft tows E, depending upon the requirements of the woven structure to be formed.

In contrast, in the primary portion, at least some (e.g. all) of the binding stacks are bound throughout the thickness of the woven structure, by one or more binding warp tows which extend throughout the thickness of the portion. One suitable example weave structure is shown in <FIG>, which shows a layer-to-layer angle interlock weave for seven binding warp tows A through eight layers of weft tows E. As above, it will be understood that the number of warp A and weft tows E may be varied according to the desired thickness and properties of the primary portion.

Although a woven structure and woven preform has been described above with respect to primary and secondary portions having different numbers of free leaves, the invention envisages other types of woven preforms and woven structures having one portion (e.g. only a primary portion), or any number of multiple portions, as will become clear from the following description.

<FIG> is a cross-sectional view of a shell portion <NUM> of a woven preform which may be used for forming a hollow aerofoil portion of a vane. The shell portion <NUM> is woven as a substantially planar woven preform comprising two superposed leaves <NUM>, <NUM>, each leaf <NUM>, <NUM> having a multi-layer weave substantially as described above. The leaves <NUM>, <NUM> are bound at two edge regions <NUM>, <NUM> such that the shell portion <NUM> as a whole forms a single leaf (according to the terminology set out above). In a central region <NUM> of the shell portion, the leaves <NUM>, <NUM> are not bound to each other and are therefore free to separate from each between the edge regions <NUM>, to form an inter-leaf channel <NUM> therebetween (as best shown in <FIG>). To form the shell portion, binding stacks <NUM> in the edge regions <NUM>, <NUM> bind weft tow layers of the respective leaves together, whereas binding stacks <NUM> in the central region <NUM> do not bind weft tow layers of the respective leaves together. The stacks are schematically illustrated in <FIG> as the through-thickness extent by which the binding warp tows extend in the respective stack, and while only a minority of stacks are shown for clarity of the drawing, it should be appreciated that there is a full array of stacks along the lateral direction of the woven structure.

In this example, the edge regions <NUM>, <NUM> correspond to a leading or trailing edge of a vane. The weave arrangement (i.e. the stacks) in the edge regions <NUM>, <NUM> will be described in further detail below.

The shell portion <NUM> has a longitudinal extent along the longitudinal direction (or warp direction) P corresponding to a span of the aerofoil portion of the vane. This corresponds to a direction along which a preform comprising the shell portion <NUM> would be drawn during a manufacturing process. The shell portion <NUM> has an orthogonal lateral direction F, corresponding to a chordwise direction of the vane (which may generally correspond to a weft direction of the shell portion <NUM>).

The bound edge regions <NUM>, <NUM> of the shell portion <NUM> are at lateral sides of the shell portion <NUM>. In this example, the bound edge regions <NUM>, <NUM> primarily extend along the entire longitudinal extent of the shell portion <NUM>, although in other examples the edge regions may terminate before the longitudinal extremes of the shell portion <NUM> (for example to permit further separation of the leaves there). Accordingly, the edge regions <NUM>, <NUM> have a component in the longitudinal direction which is much greater than a component in the lateral direction F. In the edge regions <NUM>, <NUM>, binding tows extend between the leaves <NUM>, <NUM> to join the leaves together as will be described in further detail below with reference to <FIG> and <FIG>.

As shown in <FIG>, a forming element, in this example a mandrel <NUM> which has a near net surface corresponding to a desired shape of an internal surface of the vane, may be placed between the leaves <NUM>, <NUM> into the inter-leaf channel <NUM> of the shell portion <NUM>, to form the shell portion <NUM> into the near net shape.

The expression "near net surface" is a term of the art, and is intended to refer to the mandrel defining a profile which is close to the final shape of the composite component to be manufactured (e.g. except for relatively minor finishing and machining), such that the reader understands that the action of forming the woven preform into the shape of the component is conducted by applying the preform to the mandrel (or inserting the mandrel in the preform).

The mandrel <NUM> may have a tapered end for insertion into the inter-leaf channel, and a forming portion for locating in the inter-leaf channel <NUM> and defining the near net surface. The forming portion is the portion of the mandrel which causes the shell portion <NUM> to adopt a near net shape for the component as described above.

<FIG> shows an example woven structure <NUM> (a woven preform) which includes a shell portion <NUM> as described above, together with two free portions <NUM>, <NUM>, each longitudinally adjacent to an end of the shell portion <NUM>. The free portions <NUM>, <NUM> substantially correspond to the "secondary portions" as described above with reference to <FIG>, whereas the shell portion substantially corresponds to the "primary portion" as describe above with reference to <FIG>.

As shown in plan view (i.e. normal to a thickness direction of the woven preform), the woven preform <NUM> is substantially the shape of a dumbbell, or an English capital I (with serifs) or H. The woven structure <NUM> is shown after a trimming operation in which portions of the preform have been removed including trimmed portions laterally adjacent to the shell region <NUM> on each side and longitudinally between the laterally-protruding regions of the free portions <NUM>, <NUM>. Before trimming, these trimmed portions would define the lateral sides of the woven preform. In this particular example, lateral sides 702a, 702b, 704a, 704b of the free portions <NUM>, <NUM> correspond to the lateral sides of the woven preform, before trimming.

The edge regions <NUM>, <NUM> extend along the longitudinal extent (length) of the shell portion <NUM>. As can be seen from <FIG>, the edge regions <NUM>, <NUM> are laterally offset from lateral sides of the preform (i.e. the untrimmed preform). Accordingly, the free portions <NUM>, <NUM> generally have a greater lateral extent than the shell portion, and extend laterally beyond junctions <NUM> between the shell portion <NUM> and the free portions <NUM>, <NUM>. The free portions <NUM>, <NUM> each correspond to an integrated platform (such as a tip and a root of the vane respectively).

Each free portion <NUM>, <NUM> has two opposing free leaves in superposition (not shown in this plan view - best shown in <FIG> and <FIG>), each opposing free leaf <NUM>, <NUM> having a multi-layer weave with warp tows corresponding to, and continuously extending from, a respective leaf of the shell portion <NUM>. The leaves <NUM>, <NUM> of the free portions <NUM>, <NUM> are free to separate from one another throughout their longitudinal and lateral extents (i.e. along the span and chordwise directions of the vane), while remaining attached to the respective leaves of the shell portion <NUM> at the junctions <NUM>. This is best illustrated in <FIG>, which shows the preform of <FIG> in perspective view, with the leaves <NUM>, <NUM> separating from one another away from the shell portion <NUM>, and illustrating how a forming element can be inserted between the leaves <NUM>, <NUM> and extend through the shell portion. When the shell portion <NUM> is expanded as noted above, the junction <NUM> forms a closed loop boundary having two loop segments associated with each of the leaves of the shell portion <NUM>, and the respective leaves <NUM>, <NUM> extend from these loop segments.

The lateral sides 704a, 704b of the free portion correspond to lateral sides of the respective portion of the composite component. The above definitions of the shell portion <NUM> and free portions may apply to the woven preform after any trimming operation to prepare the woven preform for forming the composite component, for example. For example, it may be that the woven preform has trim portions (for removal) at lateral edges of the preform laterally adjacent to the free portions and which bind through a thickness of the woven structure (e.g. binding the respective leaves together). However, after trimming, the respective free leaves <NUM>, <NUM> would be free to separate from one another throughout their longitudinal and lateral extents.

By forming a preform in this way, hollow components can be formed using a multi-layer weave, without requiring a post-weave join between (i) opposing leaves/portions of the hollow component; and/or (ii) the hollow portion and adjoining support structures, such as the platforms described above. While a simple mandrel is shown in <FIG> which may necessitate a non-reentrant geometry (e.g. with a <NUM> or positive drafting angle to facilitate removal), it is envisaged that more complex mandrels (e.g. with retractable/extendable parts) or an inflatable mandrel may be provided to enable forming of re-entrant geometry.

As shown in <FIG>, the example woven preform <NUM> comprises four tab portions <NUM>, each tab portion <NUM> having a multi-layer weave continuous with and extending longitudinally from a respective leaf <NUM>, <NUM> of the respective free portion <NUM>, <NUM>. As can be seen in <FIG>, the tab portions <NUM> extend longitudinally beyond the unbound boundary <NUM> (i.e. junction) of the shell portion <NUM>, to be laterally adjacent the shell portion <NUM>. In this example, the tab portions <NUM> have no warp tows in common with the shell portion <NUM>, but in other examples the shell portion <NUM> may extend laterally along a mid-span (i.e. away from the junction <NUM>) to have an overlapping lateral extent with one or more tab portions at longitudinal positions away from the tab portions, such that there may be common warp tows between them. Nevertheless, following trimming between the tab portions and the shell portion, would separate the respective portions of the warp tows.

The tab portions <NUM> in this example are for forming a join with a corresponding tab portion <NUM> on the opposing leaf (i.e. the tab portion <NUM> of each leaf <NUM> and <NUM> of the free portions are configured to be joined together), as will be further described below. In other examples, the tab portion <NUM> may be for directly joining with the opposing leaf.

As noted above, the shape of woven preform <NUM> of <FIG> reflects a post-weaving trimming operation, and the woven preform <NUM> is derived from a larger woven preform <NUM> as originally woven, which is trimmed along edges woven preform <NUM> (as indicated by the solid lines in <FIG>) to form the outline of the I shaped woven preform. During the trimming operation, the woven preform <NUM> is also trimmed between each of the tab portions <NUM> and the shell portion <NUM> to define a lateral side of each of the tab portions <NUM> (and a lateral side of the shell portion <NUM>). Such a trim permits deflection of the tab portions <NUM> relative to the laterally-adjacent shell portion <NUM>.

As shown in <FIG> and in <FIG>, during manipulation of the free leaves <NUM>, <NUM> of the free portions, the tab portions <NUM> are overlaid joined along a join <NUM>. By folding of the free leaves <NUM>, <NUM> and tab portions <NUM> relative to the shell portion <NUM>, the platform region is formed.

As can be seen in <FIG>, in this particular example a thickness of the tab portion <NUM> tapers in a stepwise manner along the longitudinal extent of the tab portions <NUM>. In this way, a tapered join portion <NUM> is formed when the tab portions <NUM> are joined, a tapered join being a join between overlapping portions, one or both of which tapers in thickness along a direction corresponding to an overlapping extent of the join. The tapering of the tab portions <NUM> results in good structural bond (due to a high contact area) between the tab portions <NUM> without adding thickness.

The thickness of the tab portions <NUM> is defined by a weave structure in the tab portion <NUM>, in particular, a multi-layer bound thickness of the woven preform <NUM>. As such, the taper is formed in a stepped structure, corresponding to each layer of the tows. The multi-layer bound thickness is defined by the number of weft tows E bound by binding warp tows A. Accordingly, the thickness of the tab portions <NUM> can be altered by altering the weave structure, in particular the number of weft tows E bound by binding warp tows A.

Tapering of a thickness of the tab portions may be achieved, for example, by selectively trimming the warp tows at staggered locations along the tab portion, and/or be defining a weave for binding stacks in the tab portions over which a number of weft tow layers bound by the respective binding warp tows progressively reduces. After trimming of free weft tows, this progressively reduces the thickness of the portion.

The joined free leaves <NUM>, <NUM> and tab portions <NUM> together form a platform (also known as a support member, e.g., for a root and/or tip of a vane) which is integral with the shell portion <NUM> (e.g. the aerofoil part of the vane). Although the platforms each comprise two free leaves, when these are joined at the join portion, the resulting platform has relatively high structural integrity.

After forming the shell portion <NUM> into a near net shape using the mandrel <NUM> as described above, the leaves <NUM>, <NUM> of the free portions <NUM>, <NUM> are separated to form a near net shape for the component, with the free portions <NUM>, <NUM> forming the platforms (i.e. tip and root) of the vane, as described above with reference to <FIG>. The free portions <NUM>, <NUM> can be formed into near net shape using respective portions of a forming structure. In this way, the leaves <NUM>, <NUM> of the free portions <NUM>, <NUM> are separated and received on respective portions of the forming structure to adopt the near net shape for the component. The forming structure may also facilitate the superposition and joining of the tab portions <NUM>, and or be configured to maintain the mandrel in a fixed relationship relative to the forming structure.

After forming the woven preform <NUM> into the near net shape of the component, a resin infusion operation may be conducted on the preform to provide matrix material, and the infused woven structure may then be cured and/or compacted using any suitable procedure as is known in the art. It may be that the tows of fibre-reinforcement material are pre-impregnated with matrix material, permitting forming of the component (e.g. using a compacting and/or curing process) without a resin infusion operation.

A plurality of shell portions <NUM> (or woven preforms <NUM> comprising shell portions <NUM>, free portions <NUM>, <NUM> and/or tab portions <NUM>) may be manufactured as part of a single woven preform <NUM>, to form a vane segment as described above with reference to <FIG>.

Referring back to <FIG>, as noted above the example shell portion <NUM> of the woven preform <NUM> comprises lateral edge regions <NUM>, <NUM>, which correspond to a leading and/or trailing edge of the vane respectively. It will therefore be appreciated that the edge regions <NUM>, <NUM> join two leaves <NUM>, <NUM> as described above (i. e when the desired component is hollow). In other examples, the lateral edge regions <NUM>, <NUM> may be part of a single leaf which is bound through its thickness along its lateral extent, such that there is no inter-leaf opening for forming a hollow structure.

A schematic close-up view of the fibre tows in one of the edge regions <NUM> is shown in <FIG> (normal to the warp direction), and a schematic plan view is shown in <FIG> (normal to the thickness direction). It will be appreciated that in <FIG>, the vertical direction P corresponds to a longitudinal (spanwise) direction of the vane, in which the warp fibres A extend, and the horizontal direction F corresponds to a lateral or transverse (chordwise) direction of the vane, in which weft fibres E generally extend. It will also be appreciated that whilst only one edge region <NUM> is shown in <FIG>, the following description is equally applicable to the other edge region <NUM> of the shell portion <NUM> of the woven preform <NUM> as described above.

As can be seen in <FIG>, the edge region <NUM> is configured to taper in a thickness direction T towards the respective lateral side. An example arrangement of tows in this region to provide such a thickness reduction will now be described with reference to <FIG>, which shows a cross-sectional view of the edge region <NUM> normal to a weft direction.

As previously, the weft tows are indicated by E, and the weft direction is indicated by F. It can be seen that in this example, seven weft fibres E extend in the weft direction F.

As shown in Figure 5a, the shell portion <NUM> comprises a series of laterally adjacent stacks, each stack extending in the longitudinal (or warp) direction P. Typically, the stacks are arranged in an alternating configuration of warp (non-binding) stacks and binding stacks, as discussed above. Each stack B as shown in Figure 5a corresponds to a warp tow position along the lateral direction F, and similar stack positions are indicated in <FIG> with reference numeral B. Each stack B comprises one or more warp tows A in superposition within the stack B. In binding stacks, the warp tows A are interlaced with the weft tows of a plurality of weft tow layers to bind the weft tow layers, for example in a layer-to-layer angle interlock weave, as described with reference to B<NUM> in <FIG>. It will be appreciated that in other examples. The weave pattern will be described in more detail below with reference to <FIG> and <FIG>.

The number of weft tow layers bound by (one or a plurality of warp tows in) a respective stack B is defined as a weft binding number. The extent by which a stack binds weft tow layers is schematically illustrated in <FIG> by the dashed box corresponding to the stack with reference numeral B, such that when a warp tow extends through the dashed box this indicates that the respective stack binds those weft tows (weft tow layers). It can be seen in <FIG> that from left to right (towards the lateral side of the edge region), the binding stacks B as schematically illustrated generally decrease in weft binding number. In this example, the stacks B from left to right have a weft binding number of <NUM>, <NUM>, <NUM>, <NUM>.

As shown in <FIG>, some of the weft tows E towards the upper and lower portions of the weave therefore comprises a bound portion (which is bound by a binding stack B, as indicated by the dashed lines) and an unbound portion which extends laterally beyond a bound region of the stacks B. For example, the weft tow indicated by E in <FIG> has a bound portion E1 and an unbound portion E2. It will be appreciated that only a portion of the edge region <NUM> is shown here and therefore that the bound portion may extend generally further in the direction away from the edge region <NUM>. The weft tow indicated at E can be considered a partially bound weft tow. It can be seen from <FIG> that the unbound portion E<NUM> extends toward the lateral side of the shell portion <NUM>, beyond the last respective binding stack (indicated by the stack marked B) by which it is bound. The lateral extent of the unbound portion E<NUM> corresponds to at least one stack B of the multi-layer weave.

After forming of the woven preform <NUM> comprising the shell portion <NUM>, the woven preform <NUM> can be trimmed as discussed above with reference to <FIG>. <FIG> shows the edge region <NUM> after trimming along the trim line L, such that each of the weft tows (and thereby weft tow layers) layers have a common trimming location which corresponds to a lateral side of the shell portion <NUM>. The present invention envisages a single trimming action being conducted for all weft tow layers at a respective longitudinal position, and a trimming action may proceed along the lateral sides of the shell portion in a single action to swiftly perform trimming. With the single trimming line L, the partially bound weft tows E retain their unbound portion E2 after trimming, and any unbound portions E2 are ultimately retained in the formed component by a resin material that encapsulates the fibre reinforcement material. This is in contrast with previously known techniques in which a woven preform may be trimmed at locations corresponding to where they are last bound, to prevent loose ends of weft tows extending beyond a bound portion of the structure. According to such previously-considered methods, the entire unbound portion E2 of weft fibre E would be trimmed. The trimming described herein may be performed with an apparatus to conduct a single trimming action along the trim line L, for example a cutting press. The ability to use such a press for a woven structure that tapers in thickness represents a simplification and efficiency improvement over previously-considered methods which may require that trimming is performed manually or with an intricately programmed robot. Therefore, as a result of the method described herein, the method of manufacture is more reliable and efficient.

A thickness of an edge of a component, formed using the weave structure of the edge region <NUM> as described above, may reduce towards the respective lateral side of the component despite retention of the unbound portions of the weft tows. For example, as will be described in further detail below, the number of warp tows in successive stacks towards the respective side may reduce, thereby reducing the fibre volume towards the respective side.

After a forming operation (e.g. a resin infusion operation and/or a curing operation to form the woven structure into the near net shape of the component), the woven structure comprises both matrix and fibre reinforcement material, and is cured to form a resulting composite component. A partial cross-sectional view of an example component <NUM>, corresponding to the edge region <NUM> as depicted in <FIG>, is shown in <FIG>. This shows the weave structure (stacks B and weft fibre tows E) within the matrix <NUM>. It can be seen in <FIG> that the unbound portions E<NUM> of the weft tows E are retained in the matrix material <NUM>. In this way, a relatively high fibre volume fraction is retained towards the lateral edge <NUM>, despite any reduction in the number of binding warp tows A (and in the weft binding number). As a result, the mechanical properties in the edge region <NUM> may be improved in comparison with a component which has a lower fibre volume fraction at a comparable (e.g. tapering) edge region <NUM>.

A thickness reduction as described above can be achieved by varying the weave structure in the stacks towards the edge region, as will now be discussed with reference to <FIG> and <FIG>. Although the reduction in thickness and provision of unbound portions of the weft tows in a matrix complement each other and may be provided in a single woven structure, it will be appreciated that each of these features may also be implemented in example woven structures independently of the other.

Referring to <FIG>, various pairs of stacks for use in an edge region to result in a reduction of thickness towards the respective lateral side will now be described. In each of the pairs of weave stacks, a property of the weave structure is varied between the stacks to reduce the thickness. Recalling the discussion of <FIG> above, it will be appreciated that in the various examples of <FIG>, the weft tows E extend out of the page, and the warp tows A follow the pattern along the warp direction P as shown. It will be appreciated that any region which includes a tapering thickness may include one or more of these variations in the structure in combination.

In each of the following examples, the variation between the first stack and the second stack is such that the second stack permits a reduction in thickness relative to the first stack. The first stack is the upper stack in the respective drawing, and the second stack is the lower stack.

<FIG> shows a first example pair in which a first (upper) stack has seven warp tows which are interwoven with eight weft tow layers in a layer-to-layer angle interlock weave. In the second (lower) stack, only six warp tows are present, again interwoven with eight weft tow layers. The weave structure in this case remains generally layer-to-layer angle interlock. In addition to reducing the number of warp tows, the second stack also incorporates a multi-weft step, which will be described in further detail below, to bind the same number of weft tows with a reduction in the number of warp tows. By reducing the number of warp tows, a thickness can be reduced.

In <FIG>, the first stack has seven warp tows which are interwoven with eight weft tows in a layer-to-layer angle interlock weave. However, in the second stack, the weave type is changed to an orthogonal through-thickness weave as described above with reference to <FIG>. In the second stack, the change in weave type means that the same number (seven) of weft tows can be bound with only a single warp tow. Accordingly, it will be understood that by varying the weave type, the thickness of the weave is reduced.

In <FIG>, the first stack has seven warp tows which are interwoven with eight weft tow layers in a layer-to-layer angle interlock weave. However, in the second stack, the weave type is changed to a through-thickness angle interlock weave. Again, in the second stack, the change in weave type means that the same number of weft tows (eight) can be interwoven with only a single warp tow. Accordingly, it will be understood that by varying the weave type, the local thickness of the structure can be reduced.

In <FIG>, the first stack has a single warp tow interwoven with eight weft tows in an orthogonal through-thickness weave. In the lower stack, the weave type remains the same, but the single warp tow binds only five weft tows. By reducing the number of bound weft tows (defined above as a weft binding number), a thickness can be reduced.

In <FIG>, the first stack (the left-most stack in the drawing) has seven warp tows which are interwoven with eight weft tows in a layer-to-layer angle interlock weave.

In the second stack (the right-most stack in the drawing), six warp tows are interwoven with eight weft tows, in a layer-to-layer angle interlock weave including a multi-weft step. In particular, it can be seen that, at different positions along the warp, a pair of warp tows (the second and third warp tows A<NUM>, A<NUM> from the top) each include a step or jump along a thickness direction to bind two (or more) weft layers at a single longitudinal position, instead of a single weft tow as is standard for a layer-to-layer angle interlock weave. By increasing a number of binding warp tows having a multi-layer step in a respective repeating pattern (i.e. in this example from zero to one), a thickness can be reduced.

Referring to <FIG>, the thickness of the edge region may also be reduced in a lateral direction towards the side by varying the stack arrangement in the edge region <NUM>.

As noted above, it is typical to provide an alternating arrangement of warp (non-binding) stacks and binding stacks along a weft direction of a woven preform. As noted above in the discussion of <FIG>, a warp stack may comprise a warp tow extending in each warp tow position in the weave (e.g. at each and every location between weft tow layers). Accordingly, the amount of fibre in a warp stack may be relatively high compared with some arrangements of a binding stack (particularly through-thickness binding stacks having a single warp tow).

An example stack arrangement for an edge region as discussed above is shown in <FIG>, which comprises an alternating arrangement of binding B and warp (non-binding) W stacks. As described above with reference to <FIG>, and as shown in <FIG>, a warp stack comprises a plurality of warp tows A which extend substantially longitudinally through the stack without being interwoven between the weft tows E (i.e. the warp tows A remain substantially at a single thickness position).

In the binding stack marked B<NUM>, the stack has a binding arrangement (e.g. in a layer-to-layer angle interlock weave), in particular having seven warp tows, binding eight weft tows. In the binding stack marked B<NUM>, the number of warp tows is decreased to four (for example as discussed above with reference to <FIG>), whilst the number of weft tows remains the same. In the binding stack marked B<NUM>, the number of warp tows is again decreased to two, whilst the number of weft tows remains the same. By providing an alternating structure of binding and warp stacks, the warp stacks may regulate direction of the weft tows through the woven structure, which may help retain a desired shape of the woven structure. This arrangement of alternating binding and warp stacks may be most suitable for components which have an appreciable edge region over which the taper is implemented - e.g. a thicker vane.

An alternative to the arrangement of <FIG> is shown in <FIG>. In this arrangement, the edge region comprises an alternating arrangement of binding stacks B and at least one intermediate stack I.

An intermediate stack as referred to herein is a binding stack comprising a through-thickness angle interlock or through-thickness orthogonal interlock (e.g. as described above with reference to stack B2 of <FIG>). The adjacent binding stacks may comprise a different weave type, for example a weave type having two or more warp tows (e.g. a layer-to-layer angle interlock, optionally with a multi-weft jump as described above). By providing an intermediate stack I as described above between binding stacks B, a relatively greater thickness reduction may achieved over a relatively shorter lateral extent. Such an arrangement may be suitable for a component having a relative short lateral extent for a thickness reduction, such as a hollow component with a relatively thin wall (shell). Although there may be a relatively large change in fibre volume between the binding and intermediate stacks, the disclosed arrangement is considered to permit a desired thickness reduction and adequate overall volume fraction in the formed component within the edge region.

A method <NUM> of forming a component comprising a woven structure as described above will now be described in greater detail with reference to <FIG>.

In a first step <NUM>, weave data is input to a loom controller of a loom to be used for weaving the preform. The weave data may comprise model data and/or instructions for conducting a weaving operation, such as weave types for respective stacks and portions of the preform. In a second step <NUM>, the loom conducts the weaving operation to weave the preform according to the weave data. For example, the loom uses the weave data to conduct the weaving operation to form the rectangular woven preform <NUM> as shown in <FIG> (including shell portion <NUM>, free portions <NUM>, <NUM>, tab portions <NUM> and trim portions to be trimmed). In other examples, it will be appreciated that the loom may receive weave data to produce a plurality of woven preforms <NUM> which are joined together, for example as described with respect to <FIG>, a plurality of separable woven preforms for forming discrete components.

In step <NUM>, the preform from the loom is trimmed to the required shape, and to separate any portions (e.g. between shell and tab portions as described above). As noted above, trimming along boundaries of respective portions (e.g. at the lateral sides of the shell) may be carried out in a single action, such as by a cutting press. As described above with reference to <FIG>, the trimming step may include trimming between any tab portions <NUM> and shell portions <NUM>, such that these portions can be moved relative to each other. In an example where a plurality of woven preforms <NUM> to be joined together are formed by the loom, this trimming step may comprise cutting the preform at the cut point <NUM> as discussed with respect to <FIG>.

In step <NUM>, the woven preform is applied to a forming structure, optionally including a mandrel (where the woven preform comprises a shell portion), to adopt a near net shape for the component. The woven preform and forming structure may then be placed in a sealing structure or mould for resin transfer moulding. For example, a mandrel may be inserted between two leaves of any shell portion <NUM>, and any free portions <NUM>, <NUM> may be arranged on a respective portion of the forming structure. Any tab portions <NUM> may be folded over and placed adjacent to corresponding opposing tab portions <NUM> such that the tab portions <NUM> overlay each other, on corresponding portion of the mandrel to enable the tab portions <NUM> to be joined in the next step.

In an example where a plurality of woven preforms <NUM> which are joined together are formed by the loom, this shaping step may comprise moving each woven preform <NUM> relative to the next (i.e. unfolding the sequence of woven preforms <NUM> as described with reference to <FIG>).

Claim 1:
A method for manufacturing a composite component, comprising:
weaving a multi-layer woven preform (<NUM>, <NUM>) for the component from warp and weft tows (A,E) of fibre-reinforcement material, so that the woven preform (<NUM>) comprises:
a longitudinal direction (P) corresponding to an elongate extent of warp tows (A) of the woven preform (<NUM>, <NUM>);
a lateral direction (F) transverse to the longitudinal direction (P);
a multi-layer weave comprising:
a plurality of weft tow layers, each layer comprising an array of weft tows (E) distributed along the longitudinal direction (P), arranged so that weft tows (E) from each weft tow layer are superposed at longitudinally-distributed positions in the multi-layer weave;
a plurality of laterally-adjacent stacks (S) extending along the longitudinal direction (P), wherein each stack corresponds to a warp tow position along the lateral direction and comprises one or more warp tows in superposition within the stack (S);
a primary portion (<NUM>) having a longitudinal extent along the woven preform, the primary portion (<NUM>) having one or more edge regions (<NUM>, <NUM>) each defining a respective lateral side of the primary portion (<NUM>);
wherein for the or each edge region (<NUM>, <NUM>):
the multi-layer weave defines at least the edge region (<NUM>, <NUM>);
a plurality of stacks in the edge region (<NUM>, <NUM>) are binding stacks (<NUM>) in which one or more warp tows are interlaced to bind a respective plurality of weft tow layers;
a weave property differs between binding stacks (<NUM>) in the edge region (<NUM>, <NUM>) to reduce a thickness of the edge region (<NUM>, <NUM>) towards the respective lateral side; wherein
the step of weaving the woven preform (<NUM>, <NUM>) is conducted so that, in the or each edge region (<NUM>, <NUM>):
the binding stacks (<NUM>) each have a plurality of warp tows which are interlaced to bind a respective plurality of weft tow layers; and
the multi-layer weave has an alternating pattern of binding stacks and one or more intermediate stacks, characterized in that each intermediate stack comprising a through-thickness angle interlock or through-thickness orthogonal interlock type of multi-layer weave.