Patent Description:
Rotating aerofoil components formed of continuous fibre-reinforced polymer composites, such as gas turbine engine fan or compressor blades, wind turbine blades, helicopter rotor blades, propellors etc., are exposed to a high risk of delamination during operation due to, for example, bird-strike type events. Large amounts of delamination can lead to a loss of structural stiffness and potential catastrophic failure. Z-pins are conventionally used for increasing a delamination resistance of composite laminates, thus delaying or arresting the propagation of interlaminar cracks in the laminates. Typically, they are formed of metallic materials, carbon, carbon-fibre-reinforced resins, glass, ceramic materials, or composites based on such materials. The Z-pins extend across layers of the composite to bridge interlaminar cracks and oppose opening and sliding displacements, significantly increasing the energy necessary for delamination to progress. Depending on requirements, the Z-pins may be embedded in the composite so that they are perpendicular to the layers of the composite, or at an angle from this perpendicular direction. Either way, because Z-pins extend across layers, a Z-pin enters the wake of a growing interlaminar crack to exert a bridging action until it either ruptures or is completely pulled out from the embedding composite laminate. Thus, the damage resulting from in-service events affecting composite laminates and the components they form can be reduced, decreasing the risk of catastrophic failure.

United Kingdom patent application <CIT>, United States patent application <CIT> and United States patent <CIT> disclose methods of inserting Z-pins into composite components, and United Kingdom patent application <CIT> and United States patent <CIT> disclose composite components reinforced with Z-pins.

United States patent application <CIT> relates to a composite component having a body formed from a plurality of fibre reinforced non-metallic layers. The body comprises a delamination region configured so as to permit delamination; and a deflector region configured so as to resist delamination. In the event of delamination, delamination is deflected to and continues to propagate in the delamination region.

Conventionally, Z-pins are embedded in patterns which may require tens of thousands of Z-pins to realise their delamination-resistance function. Embedding this number of pins requires significant manufacturing time and increases the cost of each component. Furthermore, conventional patterns of Z-pins, despite including large numbers of Z-pins, do not always ensure reliable delamination-resistance performance.

Therefore, it is desirable to provide a composite material rotor aerofoil component having an enhanced and reliable delamination resistance achieved by a pattern of Z-pins embedded into the component structure, which pattern is both cost- and time-efficient to manufacture.

According to a first aspect, the present invention provides an aerofoil component as set out in claim <NUM>. Optional features are included in the dependent claims.

Advantageously, the chevron pattern according to option (i) can guide a delamination initially travelling through the aerofoil component radially from its root to its tip towards the component's leading and trailing edges, away from the core of the blade. Keeping the core of the blade protected, even at the cost of possible delamination the peripheral edges of the blade, is important, as it is the core of the blade that forms the main mass, and therefore structural integrity of the blade. Furthermore, the stiffness of the blade core determines the lower order resonant frequencies of the blade, which much be kept as constant as possible, even after (for example) impact events such as bird strikes. The chevron pattern achieves this by providing a highly delamination-resistant barrier to continued delamination travel in the radial direction, but a less delamination-resistant barrier towards the leading and trailing edges. Similarly, a chevron pattern according to option (ii) can guide a delamination initially travelling through the aerofoil component radially from its tip to its root towards the component's leading and trailing edges. Furthermore, the chevron pattern can achieve this effect using substantially fewer Z-pins than conventional patterns.

According to a second aspect, the present invention provides a method of forming the aerofoil component of the first aspect as set out in claim <NUM>.

The method may further include a subsequent step of curing (typically by applying heat and pressure) the pre-preg layers containing the inserted Z-pins.

Optional features of the invention will now be set out. These are applicable singly or in any combination with any aspect of the invention.

The arms of the chevron may form an angle therebetween at the vertex of <NUM>° or more, and preferably of <NUM>° or more, or <NUM>° or more.

The arms of the chevron may form an angle therebetween at the vertex of <NUM>° or less, and preferably of <NUM>° or less, or <NUM>° or less.

The cross-sectional area of each Z-pin may be <NUM><NUM> or more, and preferably of <NUM><NUM> or more, or <NUM><NUM> or more.

The cross-sectional area of each Z-pin may be <NUM><NUM> or less, and preferably of <NUM><NUM> or less, or <NUM><NUM> or less.

The Z-pins may be arranged in a pattern forming plural nested chevrons on the pressure and/or suction surface of the aerofoil component. This pattern can provide additional protection against delamination growth through the component.

The aerofoil component may be a gas turbine fan blade, a gas turbine compressor blade, a wind turbine blade, a propellor blade, or a helicopter rotor blade.

According to a third aspect, the present invention provides a gas turbine engine as set out in claim <NUM>.

As noted elsewhere herein, the gas turbine engine may comprise a gearbox that receives an input from the core shaft and outputs drive to the fan so as to drive the fan at a lower rotational speed than the core shaft.

The gearbox may be a reduction gearbox (in that the output to the fan is a lower rotational rate than the input from the core shaft). Any type of gearbox may be used. For example, the gearbox may be a "planetary" or "star" gearbox, as described in more detail elsewhere herein. The gearbox may have any desired reduction ratio (defined as the rotational speed of the input shaft divided by the rotational speed of the output shaft), for example greater than <NUM>, for example in the range of from <NUM> to <NUM>, or <NUM> to <NUM>, for example on the order of or at least <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or <NUM>. The gear ratio may be, for example, between any two of the values in the previous sentence. Purely by way of example, the gearbox may be a "star" gearbox having a ratio in the range of from <NUM> or <NUM> to <NUM>. In some arrangements, the gear ratio may be outside these ranges.

Each fan blade may be defined as having a radial span extending from a root (or hub) at a radially inner gas-washed location, or <NUM>% span position, to a tip at a <NUM>% span position. The ratio of the radius of the fan blade at the hub to the radius of the fan blade at the tip may be less than (or on the order of) any of: <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM>. The ratio of the radius of the fan blade at the hub to the radius of the fan blade at the tip may be in an inclusive range bounded by any two of the values in the previous sentence (i.e. the values may form upper or lower bounds), for example in the range of from <NUM> to <NUM>. These ratios may commonly be referred to as the hub-to-tip ratio. The radius at the hub and the radius at the tip may both be measured at the leading edge (or axially forwardmost) part of the blade. The hub-to-tip ratio refers, of course, to the gas-washed portion of the fan blade, i.e. the portion radially outside any platform.

The radius of the fan may be measured between the engine centreline and the tip of a fan blade at its leading edge. The fan diameter (which may simply be twice the radius of the fan) may be greater than (or on the order of) any of: <NUM>, <NUM>, <NUM>, <NUM> (around <NUM> inches), <NUM>, <NUM> (around <NUM> inches), <NUM> (around <NUM> inches), <NUM> (around <NUM> inches), <NUM> (around <NUM> inches), <NUM>, <NUM> (around <NUM> inches), <NUM> (around <NUM> inches), <NUM> (around <NUM> inches), <NUM>, <NUM> (around <NUM> inches), <NUM> (around <NUM> inches), <NUM> (around <NUM> inches) cm, <NUM> (around <NUM> inches), <NUM>, <NUM> (around <NUM> inches) or <NUM> (around <NUM> inches). The fan diameter may be in an inclusive range bounded by any two of the values in the previous sentence (i.e. the values may form upper or lower bounds), for example in the range of from <NUM> to <NUM> or <NUM> to <NUM>.

The rotational speed of the fan may vary in use. Generally, the rotational speed is lower for fans with a higher diameter. Purely by way of non-limitative example, the rotational speed of the fan at cruise conditions may be less than <NUM> rpm, for example less than <NUM> rpm. Purely by way of further non-limitative example, the rotational speed of the fan at cruise conditions for an engine having a fan diameter in the range of from <NUM> to <NUM> (for example <NUM> to <NUM> or <NUM> to <NUM>) may be in the range of from <NUM> rpm to <NUM> rpm, for example in the range of from <NUM> rpm to <NUM> rpm, for example in the range of from <NUM> rpm to <NUM> rpm. Purely by way of further non-limitative example, the rotational speed of the fan at cruise conditions for an engine having a fan diameter in the range of from <NUM> to <NUM> may be in the range of from <NUM> rpm to <NUM> rpm, for example in the range of from <NUM> rpm to <NUM> rpm, for example in the range of from <NUM> rpm to <NUM> rpm.

In use of the gas turbine engine, the fan (with associated fan blades) rotates about a rotational axis. This rotation results in the tip of the fan blade moving with a velocity Utip. The work done by the fan blades <NUM> on the flow results in an enthalpy rise dH of the flow. A fan tip loading may be defined as dH/Utip2, where dH is the enthalpy rise (for example the <NUM>-D average enthalpy rise) across the fan and Utip is the (translational) velocity of the fan tip, for example at the leading edge of the tip (which may be defined as fan tip radius at leading edge multiplied by angular speed). The fan tip loading at cruise conditions may be greater than (or on the order of) any of: <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or <NUM> (all values being dimensionless ). The fan tip loading may be in an inclusive range bounded by any two of the values in the previous sentence (i.e. the values may form upper or lower bounds), for example in the range of from <NUM> to <NUM>, or <NUM> to <NUM>.

A fan blade and/or aerofoil portion of a fan blade described and/or claimed herein may be manufactured at least in part from a composite, for example an organic matrix composite, such as carbon fibre. However, at least a part of the fan blade and/or aerofoil may be manufactured at least in part from a metal, such as a titanium based metal or an aluminium based material (such as an aluminium-lithium alloy) or a steel based material. The fan blade may comprise at least two regions manufactured using different materials. For example, the fan blade may have a protective leading edge, which may be manufactured using a material that is better able to resist impact (for example from birds, ice or other material) than the rest of the blade. Such a leading edge may, for example, be manufactured using titanium or a titanium-based alloy. Thus, purely by way of example, the fan blade may have a carbon-fibre with a titanium leading edge.

A fan as described and/or claimed herein may comprise a central portion, from which the fan blades may extend, for example in a radial direction. The fan blades may be attached to the central portion in any desired manner. For example, each fan blade may comprise a fixture which may engage a corresponding slot in the hub (or disc). Purely by way of example, such a fixture may be in the form of a dovetail that may slot into and/or engage a corresponding slot in the hub/disc in order to fix the fan blade to the hub/disc. By way of further example, the fan blades maybe formed integrally with a central portion. Such an arrangement may be referred to as a bladed disc or a bladed ring. Any suitable method may be used to manufacture such a bladed disc or bladed ring. For example, at least a part of the fan blades may be machined from a block and/or at least part of the fan blades may be attached to the hub/disc by welding, such as linear friction welding.

Embodiments illustrating the principles of the invention will now be discussed with reference to the accompanying figures in which:.

It will be appreciated that the arrangement shown in <FIG> and <FIG> is by way of example only, and various alternatives are within the scope of the present invention. By way of further example, any suitable arrangement of the bearings between rotating and stationary parts of the engine (for example between the input and output shafts from the gearbox and the fixed structures, such as the gearbox casing) may be used, and the invention is not limited to the exemplary arrangement of <FIG>.

Accordingly, the present invention extends to a gas turbine engine having any arrangement of gearbox styles (for example star or planetary), support structures, input and output shaft arrangement, and bearing locations.

Other gas turbine engines to which the present invention may be applied may have alternative configurations. For example, such engines may have an alternative number of compressors and/or turbines and/or an alternative number of interconnecting shafts. By way of further example, the gas turbine engine shown in <FIG> has a split flow nozzle <NUM>, <NUM> meaning that the flow through the bypass duct <NUM> has its own nozzle <NUM> that is separate to and radially outside the core exhaust nozzle <NUM>. However, this is not limiting, and any aspect of the present invention may also apply to engines in which the flow through the bypass duct <NUM> and the flow through the core <NUM> are mixed, or combined, before (or upstream of) a single nozzle, which may be referred to as a mixed flow nozzle. One or both nozzles (whether mixed or split flow) may have a fixed or variable area. Whilst the described example relates to a turbofan engine, the invention may apply, for example, to any type of gas turbine engine, such as an open rotor (in which the fan stage is not surrounded by a nacelle) or turboprop engine, for example. In some arrangements, the gas turbine engine <NUM> may not comprise a gearbox <NUM>.

<FIG> are respective schematic views of a pressure or suction surface <NUM> of different versions of a modelled, simplified rotatable aerofoil component <NUM>, such as a gas turbine fan blade or a gas turbine compressor blade for use in the engine <NUM> of <FIG>. Other possible aerofoil components include wind turbine blades, propellor blades, or helicopter rotor blades. Modelling (discussed below) is performed to analyse the effect of an impact with a moving object at region <NUM> of each surface <NUM>. A clamped region <NUM> corresponds to the radially inner root of the aerofoil component <NUM>. The component is modelled to simulate the behaviour of a continuous fibre-reinforced polymer composite created by curing laid up pre-preg layers extending in radial and chordal directions of the aerofoil component.

The modelled, simplified component <NUM> has a length of <NUM> and a width of <NUM>, with the clamped region being <NUM> wide. The thickness of the component is <NUM> at the root, tapering gradually to <NUM> at the tip by means of single-sided laminate tapering.

<FIG> shows a version including Z-pins extending across the layers of the aerofoil component <NUM> to form a double strip pattern on the surface <NUM>, the pattern being formed by two radially-spaced, straight strips <NUM> of Z-pins extending in the chordal direction (i.e. perpendicularly to the radial direction) from the leading edge <NUM> to the trailing edge <NUM> of the component <NUM>.

In <FIG>, the modelled strips <NUM> each have a width, d, of <NUM> and extend fully to the leading <NUM> and trailing <NUM> edges of the component. The two strips are spaced <NUM> apart, with the radially inward edge of the strip closest to the root being spaced <NUM> from the base (i.e. left-hand side as drawn in <FIG>) of the component. Each strip has a <NUM>% areal density of <NUM> diameter Z-pins arranged in a 12x72 array with a square repeating unit cell, the sides of the unit cells being aligned with the length and width directions of the component.

<FIG> shows a version including Z-pins extending across the layers of the aerofoil component <NUM> to form a chevron pattern <NUM> on the surface <NUM>. The chevron is pointed towards the clamped root <NUM> of the component such that one of the arms fully extends radially outwardly from the vertex to meet the leading edge <NUM> of the component, and the other arm fully extends radially outwardly from the vertex to meet the trailing edge <NUM> of the component. The chevron pattern <NUM> in <FIG> is configured to route a delamination travelling from the root along the radial direction of the aerofoil component <NUM> towards the component's leading <NUM> and trailing <NUM> edges. It does this by providing a highly delamination-resistant path as the delamination attempts to progress radially through the Z-pins, but a less delamination-resistant path towards the leading and trailing edges.

In <FIG>, the arms of the modelled chevron <NUM> each have a width, d, of <NUM> (measured along the shortest distance across the arms, i.e. at an angle to the length direction of the component) and they extend fully to the leading <NUM> and trailing <NUM> edges of the component. The vertex of the chevron is spaced <NUM> from the base (i.e. left-hand side as drawn in <FIG>) of the component. The chevron has a <NUM>% areal density of <NUM> diameter Z-pins arranged with a similar or functionally equivalent repeating unit cell as used in the model of <FIG>. The angle between the arms of the chevron is <NUM>°.

<FIG> shows a version with Z-pins arranged in plural nested chevrons. Specifically, the example version of the component <NUM> shown in <FIG> including includes Z-pins extending across the layers of the aerofoil component <NUM> in a double chevron pattern on the surface <NUM>. In <FIG> the pattern is formed by two radially-spaced but nested chevron patterns <NUM> arranged such that both their vertices point towards the clamped root <NUM>. Relative to the single chevron pattern of <FIG>, the double chevron pattern increases the reliability by which the Z-pins can delay or arrest radial delamination propagation through the component. It will be appreciated that further chevrons can be added to further increase the reliability by which the Z-pins can delay or arrest radial delamination propagation through the component, although doing so requires a commensurate increase in the number of Z-pins used to reinforce the component <NUM>.

In <FIG>, the arms of each modelled chevron <NUM> each have a width, d, of <NUM> (measured along the shortest distance across the arms, i.e. at an angle to the length direction of the component) and they extend fully to the leading and trailing edges of the component. The two chevrons are spaced <NUM> apart measured in the length direction of the component (which equates to <NUM> apart measured in the direction of width d), with the vertex of the chevron closest to the root being spaced <NUM> from the base (i.e. left-hand side as drawn in <FIG>) of the component. Each chevron has a <NUM>% areal density of <NUM> diameter Z-pins arranged with a similar or functionally equivalent repeating unit cell as used in the models of <FIG>. The angle between the arms of each chevron is <NUM>°.

Although the chevrons of <FIG> are pointed towards the root <NUM> of the aerofoil component <NUM>, in other components where it is wanted to delay or arrest delamination propagation travelling from tip to root, the chevrons can be pointed instead towards the tip of the component, as will be described.

More generally, the areal density of Z-pins in the chevrons <NUM> may be <NUM>% or more and/or <NUM>% or less. The cross-sectional area of the individual Z-pins in the patterns may be <NUM><NUM> or more and/or <NUM><NUM> or less. The arms of the chevron <NUM> may form an angle therebetween at the vertex of <NUM>° or more and/or <NUM>° or less. The width of each of the arms on the pressure and/or suction surface of the chevron may be <NUM> or more and/or <NUM> or less.

<FIG> show respective modelled time-evolution plots A to F of the propagation of delamination through the rotatable aerofoil components <NUM> of <FIG>. The delamination of the component could be caused by an impact with an object moving at a pre-determined velocity, for example a bird. The modelling was performed using the LS-DYNA™ finite element program available from Ansys, Inc.

In these examples, the impacting object is modelled as a smooth particle hydrodynamic (SPH) projectile having an average mass of <NUM> and an average impact velocity of <NUM>/s. The region <NUM> of impact is in the top right corner of the pressure or suction surface <NUM>, near the tip of the component. The model integrates a mass-based damping coefficient having a value of <NUM>, and attributes interlamellar fracture toughnesses of <NUM> N/mm and <NUM> N/mm respectively to the unpinned and pinned regions of the surface <NUM>. The growth of the delamination with time is indicated by the increasing extent of the coloured area across the surface <NUM>, the delamination typically initiating at bottom left near the root <NUM>. The level of delamination is indicated by colour-coding with no delamination (level <NUM>) being uncoloured, fully delaminated (level <NUM>) being magenta and <NUM>, and levels in between being coloured according to the legends provided above the plots.

<FIG> shows the delamination time evolution for the component <NUM> of <FIG> having the double strip pattern of Z-pins. The double strip pattern slows down the delamination propagation, such that by <NUM> after impact the delamination has spread through only about half the component <NUM> and is subsequently arrested by the pattern. However, the delamination has fully penetrated about <NUM>% of the first strip at <NUM>, and is close to penetrating the second strip.

<FIG> shows the delamination time evolution for the component <NUM> of <FIG> having the single chevron pattern of Z-pins. The delamination progresses from the root <NUM> until it meets the chevron <NUM> by <NUM>. The delamination then continues to grow on the root side of the chevron, but is unable to pass through the chevron, being encouraged instead to grow towards the leading <NUM> and trailing <NUM> edges of the component. By <NUM> after the initial impact, the delamination is arrested, with the delaminated area being successfully contained to the root side of the chevron.

<FIG> shows the delamination time evolution for the component <NUM> of <FIG> having the double chevron pattern of Z-pins. This pattern also successfully arrests the propagation of the delamination. By <NUM> after the initial impact, the delamination is halted with the delaminated area being encouraged towards the leading <NUM> and trailing <NUM> edges of the component and successfully contained to the root side of the first of the chevrons <NUM>. This pattern provides additional insurance against complete delamination in that the second chevron can further delay or arrest the delamination propagation even if the first chevron is penetrated.

The chevron pattern and the double chevron pattern both display significantly improved delamination-resistance performance compared to the double strip pattern. Experiments and the computational modelling described above suggest that, relative to simple straight strips of Z-pins and other known patterns, arranging the Z-pins in chevrons can provide similar levels of delamination protection but using about <NUM>% fewer Z-pins. Thus the chevrons enable substantial reductions in manufacturing times and costs of Z-pin protected, polymer composite aerofoil components.

<FIG> show a non-claimed embodiment of the component <NUM> where one of the arms of the chevron created by the Z-pins extends radially outwardly from the vertex towards the leading edge <NUM> of the component, and the other arm extends radially outwardly from the vertex towards the trailing edge <NUM> of the component.

The chevron pattern <NUM> in <FIG> is configured to route a delamination travelling along the core of the component from the tip along the radial direction of the aerofoil component <NUM> towards the component's leading <NUM> and trailing <NUM> edges.

The example versions of the component <NUM> of <FIG> may be useful where it is desired to use the smallest number of Z pins, and therefore the chevron pattern is used to clamp together the most central part of the aerofoil component <NUM> where delamination poses the greatest risk to the core of the blade. Alternatively, versions such as those shown in the examples of <FIG> could be used where a second means of delamination resistance is incorporated into the aerofoil at the leading <NUM> and trailing <NUM> edge, such as an edge cap, meaning it is only the central portion that benefits from use of the pins.

In the optional version of the component <NUM> of <FIG>, according to the present invention, the Z-pins create a chevron which is pointed away from the clamped root <NUM> of the component. The chevron is constructed such that one of the arms fully extends from the vertex radially outwardly to meet the leading edge <NUM> of the component, and the other arm fully extends from the vertex radially outwardly to meet the trailing edge <NUM> of the component. By comparison with the examples shown in <FIG>, the chevron pattern of <FIG>, like those of <FIG>, provide increased resistance to delamination, but at the expense of adding further Z-pins.

<FIG> shows a non-claimed embodiment where one of the arms extends radially outwardly from the vertex until it meets the leading edge <NUM> of the component, and the other arm extends radially outwardly from the vertex towards the trailing edge <NUM> of the component. The example version of the component <NUM> in <FIG> may be of use where it is expected that delamination is more likely to travel up one edge of the aerofoil component than the other. For example, if more objects are expected to impact the aerofoil such that delamination is most likely to occur on the leading edge, more Z pins can be deployed towards the leading edge as shown in <FIG>, thus optimising the use of Z-pins to provide the best protection against delamination with the use of the fewest Z-pins.

In the non-claimed embodiment of the component <NUM> shown in <FIG> the pattern is formed by two radially-spaced but nested chevron patterns <NUM> arranged such that both their vertices point away from the clamped root <NUM>. In <FIG> one of the chevron patterns has arms which extend towards the leading <NUM> and trailing <NUM> edges of the blade, whilst the other has arms which reach both the leading <NUM> and trailing <NUM> edges of the blade. In <FIG>, each chevron has one arm which extends towards, but does not reach, either the leading edge <NUM> or trailing edge <NUM> of the blade, and the other arm extending to and reaching the trailing edge <NUM> or leading edge <NUM> of the blade.

Versions with the arrangement of Z-pins shown in <FIG> direct the creep of delamination away from the middle of the aerofoil component towards the leading <NUM> and trailing <NUM> edges in two stages; firstly with a chevron that directs the delamination towards the edges, but can allow for some bypass of the chevron, which is then stopped by a second chevron with arms which right up to the leading <NUM> and trailing <NUM> edges of the aerofoil component. In the example version of <FIG>, the chevrons are arranged pointing away from the root <NUM> so as to prevent delamination spreading down the aerofoil component <NUM> towards the root from the tip, but it will be appreciated the order and direction of the chevrons could be reversed so as to prevent delamination spreading up the aerofoil component <NUM> from the root <NUM> instead.

The example arrangement shown in <FIG> of the chevrons created by the Z-pins is a further alternative achieving many of the benefits of the double chevron pattern shown in <FIG> and <FIG>, but achieved using fewer Z-pins. In the example version of <FIG>, the chevrons are arranged pointing away from the root <NUM> so as to prevent delamination spreading down the aerofoil component <NUM> towards the root from the tip, but it will be appreciated the order and direction of the chevrons could be reversed so as to prevent delamination spreading up the aerofoil component <NUM> from the root <NUM> instead.

As previously noted, it will be appreciated that further chevrons can be added to further increase the reliability by which the Z-pins can delay or arrest radial delamination propagation through the component. Such a plurality of chevrons can be formed from any combination of those described in the present disclosure, including chevrons where both arms extend towards the edges of the aerofoil component without reaching it, chevrons where one arm extends towards the edge of the aerofoil component without reaching it and the other arm reaches the edge of the aerofoil component, and, according to the present invention, chevrons where both first and second arms reach the edge of the aerofoil component, according to the expected operating conditions, predicted failure modes, and/or desired design parameters of the user.

It is envisaged that the Z-pins forming the chevron patterns can be made of any suitable reinforcement material, for example carbon, glass, metallic materials, ceramic materials, plastic materials, or composites based on such materials.

The aerofoil component <NUM> is formed by providing laid up pre-preg layers of fibre-reinforced polymer precursor, the layers extending in radial and chordal directions of the aerofoil component. Then, guide holes are formed in the pre-preg layers extending across the planes of the layers. The guide holes form a chevron <NUM> pattern on the pressure and/or suction surface <NUM> of the aerofoil component <NUM>, such as the chevron patterns of <FIG>. Next, the Z-pins are inserted into the guide holes by , for example, feeding Z-pin rod-stock material into the pilot holes, the rod-stock being cropped to length and tamped to be flush with the preform surface.

However, it is also envisaged that the Z-pins may be inserted into the laid up pre-preg layers via any suitable method, including for example ultrasonically assisted Z-pin insertion methods, employing an ultrasonic hammer or ultrasonic gun. Another option is to insert the Z-pins into the guide holes using a hollow needle located in each guide hole as an insertion guide for each Z-pin.

Subsequent to Z-pin insertion, the pre-preg layers containing the inserted Z-pins are cured to form the component.

While the invention has been described in conjunction with the exemplary embodiments described above, many variations will be apparent to those skilled in the art when given this invention. Accordingly, the exemplary embodiments of the invention set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the scope of the invention.

Claim 1:
An aerofoil component (<NUM>) of a rotor, the aerofoil component being formed of continuous fibre-reinforced polymer composite created by curing laid up pre-preg layers extending in radial and chordal directions of the aerofoil component (<NUM>), the aerofoil component (<NUM>) further including a plurality of Z-pins extending across the layers of the aerofoil component (<NUM>) to pin the layers together, wherein:
the Z-pins are arranged in a pattern forming a chevron (<NUM>) on the pressure and/or suction surface (<NUM>) of the aerofoil component (<NUM>), the chevron (<NUM>) having a vertex and a first arm and a second arm extending at an angle from each other away from the vertex; and
the chevron (<NUM>) is pointed either (i) towards the radially inner root (<NUM>) of the aerofoil component (<NUM>) such that the first arm extends radially outwardly from the vertex towards a leading edge (<NUM>) of the aerofoil component (<NUM>), and the second arm extends radially outwardly from the vertex towards a trailing edge (<NUM>) of the aerofoil component (<NUM>), or (ii) towards the radially outer tip of the aerofoil component (<NUM>) such that the first arm extends radially inwardly from the vertex towards a trailing edge (<NUM>) of the aerofoil component (<NUM>), and the second arm extends radially inwardly from the vertex towards a leading edge (<NUM>) of the aerofoil component (<NUM>);
characterised in that the first arm extends fully to the leading edge (<NUM>) and the second arm extends fully to the trailing edge (<NUM>).