High impact reinforcement fibers for leading edge protection of aerodynamic structures

Abstract

Systems and methods for protecting aerodynamic structures, such as wind turbine blades, rotor blades, aerodynamic aircraft structures, and the like, are provided. A long fiber reinforced composite material having a helical structure is employed that is consistent with graded hardness and stiffness to develop an efficient and height adjustable leading edge protection (LEP) scheme with longer durability compared to conventional schemes while obtaining a lighter, optionally more environmentally friendly scheme. At least a portion of the plurality of layers are helically arranged relative to each other to adjust a stress wave propagation velocity of the aerodynamic blade and provide a load bearing strength for the aerodynamic blade.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Provisional Patent Application No. 63 / 367,085, filed on June 27, 2022, the entire contents of which are incorporated by reference into this application. Technical Field

[0003] The present invention relates to materials having a helical structure for protecting aerodynamic profiles. Background Art

[0004] Aerodynamic profiles are carefully designed to provide excellent aerodynamic efficiency. Efficiency is only guaranteed if the shape of the aerodynamic profile does not change over time and the surface of the profile remains intact to avoid changes in the airflow around the profile. To this end, a serious loss of aerodynamic efficiency occurs due to erosion of the leading edge (LE) of the aerodynamic profile due to high-frequency impact of particles generated by liquids and solids (such as rain, oil, water, sand, salt and dust) and the resulting damage. For aerostructures including drones, commercial aircraft, military aircraft and helicopter rotor blades, this leads to increased drag and thus increased fuel consumption. Changes in the characteristics of the aerodynamic profile also lead to changes in load distribution, which in turn lead to vibrations and, in some cases, severe structural damage. For rotor blades, this leads to reduced power generation in various applications including wind energy production, reduced efficiency in jet engines, reduced power production in submarine propellers and stationary gas and water turbines. Similar problems affect aerodynamic profiles for marine applications, including but not limited to fins, main rods and submarine profiles.

[0005] In commercial and military aviation, aerodynamic surfaces and surfaces exposed to the forward flow are subject to severe erosion from liquid and solid generated particles. These particles include, but are not limited to, rain, sand, salt, dust, ash, hail and ice. The forward facing areas of the aircraft are more susceptible to erosion including, but not limited to, nose cone, wing leading edge (LE), engine air inlets, pylons, nacelles, vertical and horizontal stabilizers and rotating blades (including fan, compressor and turbine blades of aircraft engines) and propeller blades.

[0006] In marine applications, erosion caused by particles generated by liquids and / or solids can occur on the hydrodynamic and aerodynamic surfaces of a vessel / ship. These particles include, but are not limited to, salt, dust, sand, rock debris. Areas such as the forward-facing surfaces of a vessel or ship can be damaged by erosion, including, but not limited to, propeller blades, masts, wings, rudders, keels, hulls, etc.

[0007] The blades of a wind turbine rotor are a key component in capturing wind energy and converting it into electrical energy. To maximize the annual energy production (AEP) of a wind turbine, it is very important to consider two parameters: 1) the location where wind speeds are high and sustained, and 2) the capacity and efficiency of the wind turbine design. For these reasons, operators and wind turbine manufacturers have been developing higher capacity turbines with longer rotor blades (resulting in higher blade speeds) and choosing locations such as offshore areas where the wind is stronger. As a result, blades are exposed to more extreme conditions during their service life and face more extreme durability challenges: impact, erosion, delamination, UV exposure, thermal fluctuations, lightning strikes, ice, hail, etc. AEP is often severely affected by these problems, initially due to the erosion that starts at the leading edge of the blade, reducing aerodynamic efficiency, and subsequently requiring maintenance that, if not repaired, will eventually require complete blade replacement or termination of wind turbine operation. Recent studies estimate that blade roughness caused by rain erosion can reduce aerodynamic performance and ultimately reduce wind turbine capacity by 3% to 30% depending on the severity of the erosion process. Throughout the life of a wind turbine, companies are also required to conduct expensive inspection and maintenance programs to repair damaged blades, as maximizing power generation efficiency far outweighs these costs.

[0008] With more knowledge and experience with blade dynamics, the industry has been able to increase the length of rotor blades to achieve tip speeds of 130-160 meters per second. At these high speeds, critical areas of the blades require increased performance due to extreme deteriorating effects: rain erosion at the leading edge of the blade, impacts from pressure side objects (hail, birds, bugs, rain, hail, salt, etc.), and high stresses on the blade structure. Specifically, during operation, the blades will experience varying degrees of damage, ranging from surface damage that affects efficiency to structural damage that can cause complete failure and premature end of life.

[0009] Therefore, to ensure maximum performance and energy output during service operation, blades require expensive maintenance and repairs, while incurring additional downtime costs. Therefore, for a cost-benefit analysis, blades are monitored and maintained to maximize power generation and ensure mechanical robustness of the structure. The wind turbine industry has been working to improve the overall durability of blades. The area of ​​greatest concern is the leading edge protection (LEP).

[0010] Current LEP products, including those for wind rotor blades and aircraft structures, have proven unsatisfactory due to challenging applications and disappointing life results, including those subject to impact damage caused by rain, sand, dust, debris, oil, salt, hail, and bird strikes. Rather than relying on ineffective LEP, most OEMs have resorted to overbuilding minimum wall thicknesses to improve impact resistance or applying metal shields (particularly in aerospace-related applications). Both of these options increase blade cost, make blades heavier, result in difficulties achieving good bonds between dissimilar materials, and present challenges in matching dissimilar materials to have similar bending properties required during operation. The added weight of the blades then requires more energy to turn in order to turn the propeller and blades, which also reduces their overall energy efficiency and power generation. Additionally, for fixed aerodynamic surfaces, such as the leading edge of an aircraft wing, the overall weight of the structure increases, leading to increased overall manufacturing costs and increased fuel consumption during operation.

[0011] The most common solutions to improve the robustness of leading edge erosion resistance for aerospace-related applications rely on the use of metal shields, and for wind power and helicopter blades, the solution relies on the use of polymer-based coatings and paints, such as 3M Wind Blade Protection Coating W4600 and W4601, ReNEW W Series, HC05XP1 (provided by Hontek in South Windsor, Connecticut), or RELEST Wind Coatings (provided by BASF in Ludwigshafen, Germany). The thicker the coating, the longer it can resist rain erosion. However, increasing the thickness during the manufacturing process requires several layers of coating, and drying time is required between coats. This leads to: 1) increased labor costs; 2) the introduction of weak interfaces between the layers of the coating, resulting in loss of protection; 3) the coating often peels off, resulting in a flying part that reduces aerodynamic efficiency and increases noise; 4) while the use of such coatings helps to resist erosion, they cannot prevent more severe impact damage caused by hail, birds or lightning strikes; and 5) because these coatings are applied manually using brush or spray techniques, they usually result in different thicknesses of each coating, resulting in a loss of geometric stability and aerodynamic performance. This last aspect can be eliminated by using masking tape. However, this option has the same limitations as 1-4 above.

[0012] Other solutions proposed, such as those described in WO 2008 / 157013 and WO 2013 / 092211, make use of shrouds and covers manufactured before being placed on the finished blade. The main disadvantages of these solutions are as follows: 1) it is difficult to ensure the correct geometric stability of such thin and elongated shrouds; 2) it is difficult to handle small and thin covers during assembly, because the blade shrouds are very flexible due to their long dimensions; 3) they require additional manufacturing steps, which require additional molds to shape the shell to the complex LE contour; and 4) the increased number of parts increases the manufacturing complexity, cost and the risk of defects due to imperfect integration.

[0013] Additionally, WO 2017 / 198167 describes a proposed solution using a co-curing process, where the engineered LEP is co-manufactured with the rest of the profile. The proposed solution utilizes one or more layers of short fiber mats or fabrics impregnated with a paint or coating material, while using fiber reinforcements to increase thickness and avoid inconsistencies in the coating process, thereby providing more uniform protection. This thicker fabric also helps reduce crack propagation and prevent more severe damage, such as that caused by hail impact.

[0014] It is noteworthy that erosion phenomena produced by liquids and solids are usually viewed as a surface problem rather than a low energy, high repetitive impact problem. The high tip speeds reached by the blades (up to 160 m / s) lead to impact fatigue phenomena, which are repeated high frequency, low mass (0.015 g), low energy (~0.12 J) impacts on the blade surface. In the case of droplets, the impact of the droplets produces strong water hammer pressures, peaking at ~134 MPa, which is close to (if not higher than) the strength of the standard polymer resins used in the FRP that constitutes the blade skin (usually made of glass fiber NCF embedded in a thermosetting resin for wind rotor blade applications).

[0015] A better performing solution is to dissipate energy quickly in a plane rather than throughout the thickness to avoid localized damage and ultimately have a high damping coefficient to further dissipate the energy carried by this stress wave. Stress wave propagation can be controlled by changing the impedance of the impacted material (i.e., LEP) by changing the composition of the material or changing the structure of how these components are arranged (i.e., microstructure). In the case of this stress wave-dominated problem, reinforcing materials such as short fibers and woven composites (related to WO2017 / 198167) are not the best choice. The curling in woven materials and the fiber ends in short fiber composites represent locations of stress concentration and areas that are reflected by stress waves. This in turn leads to increased damage to the substrate under rain impact and large mass impact. In addition, the weaving and short fiber structure leads to the formation of several resin-covered areas. Due to the impedance changes between the fiber-covered areas and the resin-covered areas, these areas act as crack nucleation points.

[0016] Another problem associated with current LEP programs is the requirement to use higher performance materials that unfortunately have a negative environmental footprint, such as fiberglass or high-strength metal shields. In fact, there is currently no program that utilizes bio-based products for both polymers and reinforcements.

[0017] In view of the above shortcomings of previously known systems and methods, a technology that enables the use of these materials in applications where aerodynamic profiles are subject to water / sand / dust erosion (such as wind blades, aerodynamic surfaces of aerostructures, and rotor blade applications) is needed because it will achieve acceptable performance while providing an improved environmental footprint. Sustainable materials such as natural fiber composites have an estimated 50% lower carbon footprint compared to glass fiber composites and up to 70% less greenhouse gas emissions compared to functionally equivalent fossil-based materials.

[0018] It is also desirable to provide a LEP solution that can adjust the stress wave propagation speed of an aerodynamic structure and also provide load-bearing strength to the aerodynamic structure. Summary of the invention

[0019] The present invention overcomes the shortcomings of previously known systems and methods by providing a LEP solution that achieves better rain / sand / dust / water erosion protection using a long fiber spiral laminate with graded material properties.

[0020] For example, a device for protecting an aerodynamic profile having a length and a leading edge is provided. The device may include multiple layers of parallel reinforcing fibers extending along at least a portion of the length of the aerodynamic profile and extending at least on the leading edge of the aerodynamic profile, and a resin matrix including resin permeated between the reinforcing fibers of each layer of the multiple layers and between adjacent layers of the multiple layers. In addition, at least a portion of the multiple layers may be arranged spirally relative to each other to adjust the stress wave propagation velocity and acoustic impedance of the aerodynamic profile, provide load-bearing strength for the aerodynamic profile, and suppress high-frequency impacts generated by impacts on the aerodynamic profile. For example, the impact may be at least one of raindrops, hail, dust, ice, sand, or salt.

[0021] Aerodynamic profile can be the fixed leading edge of wind turbine blade, aircraft, open rotor blade, helicopter blade, front cone, engine air inlet, pylon, cabin, vertical and horizontal stabilizer, propeller blade, fan blade, mast, keel, rudder, wing or the forward area of ​​hull.Parallel reinforcing fibers can comprise unidirectional long fiber composite material and / or non-crimped fabric.For example, non-crimped fabric can comprise biaxial configuration and / or four-axis configuration, can also comprise at least one of alkali-free glass or natural fiber material.For example, natural fiber material can comprise at least one of flax, sisal, hemp, kenaf or bamboo.In addition, parallel reinforcing fibers can comprise at least one of carbon fiber, glass fiber, aramid fiber, ultra-high molecular weight polyethylene (UHMWPE) fiber, polypropylene (PP) fiber or natural fiber.

[0022] The resin may include at least one of a thermosetting resin or a thermoplastic resin. In addition, the elastic modulus between the resin and the parallel reinforcing fibers may differ by at least ten times. At least a portion of the multilayer may be arranged spirally relative to each other in an asymmetric and / or unbalanced manner. At least a portion of the multilayer extending on the leading edge of the aerodynamic profile may include a pitch angle of 20 to 30 degrees. In addition, at least one of the resin system, fiber reinforcement or fiber treatment of the device may be selected to adjust the hardness of the aerodynamic profile, thereby adjusting the stress wave propagation velocity and acoustic impedance of the aerodynamic profile.

[0023] In addition, the multilayer may include a first parallel reinforcing fiber multilayer that is not arranged in a spiral relationship to provide load-bearing strength for an aerodynamic profile, such that the angle between the orientation directions of a first pair of adjacent layers of the first multilayer may be 30° or greater. In addition, the angle between the orientation directions of at least another pair of adjacent layers of the first multilayer may be 30° or greater. The multilayer may also include a second parallel reinforcing fiber multilayer that is arranged in a spiral relationship such that the angle between the orientation directions of at least two adjacent layers may be greater than 0° and less than about 30° to provide impact resistance for an enhanced composite structure (e.g., an aerodynamic profile). The device may also include a top coating coupled to the multilayer. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1A Various views of a wind energy blade leading edge structure are shown.

[0025] Figure 1B A composite sandwich structure is shown.

[0026] Figure 1C A schematic diagram showing areas on an aircraft that are exposed to liquid and / or solid particle impact, which may result in erosion of aerodynamic surfaces.

[0027] Figure 1DVarious blades and aerodynamic profiles that may benefit from reducing the effects of erosion caused by liquids or solids in accordance with the principles of the present invention are shown.

[0028] FIG2 illustrates an exemplary blade manufacturing process.

[0029] Figure 3 An example of a spiral geometry is shown.

[0030] Figure 4 A stack of fiber layers arranged in a spiral formation in accordance with the principles of the present invention is shown.

[0031] Figure 5A A spiral preform made with straight fibers placed on a 3D curved shape according to the principles of the present invention is shown.

[0032] Figure 5B A spiral preform made with bent fibers placed on a 2D shape according to the principles of the present invention is shown.

[0033] Figure 6 A spiral laminate stack is shown.

[0034] Fig. 7A shows a unidirectional material form, Figure 7B A non-crimped multiaxial material form is shown.

[0035] Figure 8 Shown are the results of a rain erosion test (ASTM G76) on two aerodynamic profiles representing the leading edge of a wind rotor blade.

[0036] Fig. 9 A schematic diagram of a possible structure of a leading edge protection is shown, having an at least partially helically arranged fiber reinforcement structure according to the principles of the invention.

[0037] Figures 10A to 10C It is a schematic diagram of the structure including impact resistance and bearing strength.

[0038] Fig.11 is a flow chart illustrating exemplary method steps for forming an aerodynamic blade having a helical structure according to the principles of the present invention. DETAILED DESCRIPTION

[0039] The present invention overcomes the shortcomings of previously known systems and methods by providing a universal aerodynamic profile LEP solution that achieves improved erosion and impact protection using a long fiber spiral laminate with graded material properties. Figure 1A FIG. 4 shows an LE structure used in a wind energy blade (e.g., a wind turbine blade). Figure 1AAs shown, the wind turbine blade 100 may include a leading edge (LE), a trailing edge (TE), a spar cap (SC) and a shear web (SW). The structure of the leading edge (LE) may include a monolithic composite material. For example, the leading edge structure may include a 500-1000 μm filler (putty) sandwiched between 2-3 layers of 500-1000 μm LEP coating and 2 layers of 0.8-1.6 mm biaxial glass fiber (epoxy resin). In addition, the leading edge (LE) of the wind turbine blade 100 may include a bonded joint. In addition, the shell structure of the wind turbine blade 100 may include a sandwich composite material formed by a foam core layer (FC) sandwiched between adjacent FRP panel layers.

[0040] For example, Figure 1B As shown, placing materials (including, for example, polymer layers) on foam materials between composite laminate face sheets produces a synergistic structural configuration in which the face sheets provide bending stiffness and the sandwich material provides shear stiffness and bending resistance. Sandwich panels may exhibit improved strength-to-weight ratios, sound insulation, fatigue capabilities, thermal insulation, and impact / damage resistance compared to monolithic laminate composites. Sandwich panels may have better impact performance than laminates because some of the energy associated with the impact may be dissipated with elastic deformation, there is no matrix and / or fiber damage, and / or the core layer can buffer inertial loads while the face sheets absorb energy. However, while laminate composites may deform, coatings commonly used in these applications do not have the same bending properties, which can cause cracking of the coating, significantly reducing its performance and leading to premature end of life. Laminate face sheet configuration, core type / structural properties, and boundary conditions control impact behavior. Typically, in a sandwich design, the face sheets are relatively thin and the core layer is bonded to the face sheets by adhesives. Structural and failure mechanisms that make sandwich unsuitable for some applications include: a) facesheets may prematurely separate from the core during impact due to limited bond area and strength; b) due to the thinness of facesheets relative to equivalent laminate designs, fiber breakage, fiber-matrix debonding, and laminate delamination can occur at lower impact levels; c) core layers can crush or deform in shear; and d) replacing laminate plies with sandwich materials can degrade in-plane structural properties such as compression, tension, strength, and stiffness.

[0041] Figure 1C Areas of aircraft structure that may be improved by the invention disclosed herein are shown. Figure 1D Other types of blades and aerodynamic profiles found in other industrial applications are shown which would benefit from the disclosed invention to reduce the effects of liquid or solid erosion. These include, but are not limited to, propeller blades, wing leading edges, air engine inlets, engine nacelles, nose cones, helicopter blades, compressor / turbine blades, and open rotor propellers for aviation and marine applications.

[0042] The approach described herein is based on the use of long (>2 mm) fiber reinforced composites with a helical structure, such as those described in U.S. 2021 / 0316528 and U.S. 2021 / 0339499, both of which are assigned to the assignee of the present application and are incorporated herein by reference in their entirety, with materials consistent with graded hardness and stiffness to develop efficient, highly tunable LEP approaches that are more durable than traditional approaches while resulting in a lighter and optionally more environmentally friendly approach.

[0043] Reference now Figures 2A to 2D , describes an example of a blade manufacturing process for a wind rotor blade. The long fiber reinforced composite material having a spiral structure can be applied to a wind turbine blade in the material preparation process of the fiber, core layer, etc. of the wind turbine blade, such as Figure 2A As shown in Figure 1. Using this high impact fiber reinforced LEP has the potential to reduce the amount of coating required to protect against rain erosion, bird or lightning strikes and other catastrophic events, and further reduce the structural weight of the blade, which can lead to longer blades that produce higher energy. As described in further detail below, resin infusion can be performed on both the suction side and the pressure side of a wind turbine blade, such as Figure 2B In addition, Figure 2C As shown, each shell and shear web of a wind turbine blade may be assembled by adhesive, such as Figure 2D As shown, the wind turbine blade can be demoulded, trimmed and polished.

[0044] In contrast to the solutions proposed in the past which utilized braided long fiber composites, the present invention utilizes hierarchical long fiber composites having a helical structure, e.g. Figure 3 As used herein, the term "spiral" refers to a stacked arrangement of fiber layers, such as Figure 4 As shown, the fibers of at least one layer define an orientation direction relative to the orientation direction of the fibers of an adjacent layer and provide an angle greater than 0 degrees and less than about 30 degrees. The stacked arrangement can include adjacent layers that define an angle outside of this range, the stacked arrangement can have a full rotation of less than 360 degrees, or can have more than one full rotation. The fiber orientation direction of one or more layers can be straight or curved. For example, Figure 5A A spiral preform made of straight fibers placed on a 3D curved shape is shown. Figure 5B A spiral preform made of bent fibers placed on a 2D shape is shown.

[0045] For example, Figure 6A fiber-reinforced elastic composite material layer stacking method is shown, in which each layer is rotated at a predetermined angle along the longitudinal or x-direction axis relative to the adjacent layer to form a z-direction spiral fiber orientation stack. The left image uses a single line to represent each layer (thin layer), and this figure highlights the z-direction spiral formed. The right image uses a fiber bundle (usually a bundle consisting of 3000 to 50000 or more fibers) to more realistically show the structural layer of the spiral layup. The subsequent enlarged view shows how a single laminated layer formed by a fiber bundle and a resin forms a spiral laminate stack. The spiral clockwise direction can be selected to produce a specific pitch or circularly polarized z-direction fiber, which is close enough to show a significant interlayer direct load distribution between the laminated fibers.

[0046] The ability of the fibers to share loads directly between laminate layers is an important factor in the ability of spiral laminates to absorb and dissipate impact forces more effectively than conventional composite layups and minimize the effects of impact fatigue. In addition, the spirals formed by the assembly of these tilted fibers can be tuned to specific wavelengths to suppress propagating shock waves initiated by impact forces on aerodynamic profiles, and can also be filled with a matrix containing microspheres or toughening particles to further prevent or arrest the propagation of catastrophic fractures, and the difference in elastic modulus between the fibers and the resin can be exploited to further arrest fractures initiated by blunt or sharp impacts.

[0047] Additionally, graded long fiber composites can be in the form of unidirectional (UD) and / or non-crimp fabrics (NCF), which will allow: 1) fibers to remain straight and avoid areas where stress waves generated during erosion may be blocked and reflected to cause damage (such as in crimped areas of the fabric or at the ends of short fibers); 2) more uniform in-plane stress wave dispersion to allow stress waves to disperse quickly; and 3) customized through-thickness stress wave dispersion for optimal suppression in 3D space. For example, Fig. 7A shows UD manufacturing, Figure 7B An example of a non-crimped multiaxial fabric is shown. Overall, the combined effect of these features will allow the material to: 1) relax quickly before subsequent impact events; 2) better withstand high frequency impacts from repeated water drops, sand, or salt; and 3) better spread the energy in the plane, thereby reducing localized damage.

[0048] The fiber structure of the laminate should at least partially consist of a spiral laminate. In the case of a wind rotor blade, e.g. Figure 8 As shown in ASTM G76 testing, the spiral laminate described herein can significantly reduce erosion mass by approximately 34% compared to conventional laminates used in wind blade applications. This is due to the spiral fiber arrangement being able to better dampen stress waves, thereby dissipating them away from the impact location and propagating damage in-plane by forming subcritical matrix damage, thereby dissipating impact energy while maintaining structural integrity. Figure 8Shown are a profile utilizing NCF fibers in a conventional structure used in field applications, and an aerodynamic profile featuring helically arranged NCF fibers.

[0049] Fig. 9 Schematic diagram showing a possible structure of a leading edge protection, with an at least partially helically arranged fiber reinforcement structure, possibly combined with other material components to adjust the stress wave propagation characteristics of the multi-material solution, with the aim of improving erosion resistance and impact resistance.

[0050] In some embodiments, the spiral stack can be asymmetric and / or unbalanced. For example, since the LEP region has high curvature and is confined to a smaller area of ​​the larger structure, the effects of stiffness coupling may not be significant. In addition, the pitch angle can be kept constant or variable to provide customized performance. This is to promote certain types of damage within the composite material, such as delamination between spiral layers, which will further help dissipate energy and reduce damage. For example, using a larger pitch angle (20° to 30°) on the side of the LEP close to the blade surface will prevent the final crack from starting to form on the top or outer surface of the blade.

[0051] As mentioned above, graded long fiber composites with a helical structure (e.g., a spiral stack) can be manufactured using NCF. Since long fiber NCF is a typical fabric used to manufacture wind blade skins and aircraft wing skins, this will make the manufacture and processing of LEP easier. NCF can be biaxial (BX), such as the X° / -X° layers are slightly rotated to form a spiral stack, or by developing a multiaxial (MX) fabric with a stack of layers X° / X°+α / X°+2α / X°+3α / … / X°+n*α (where α represents the inter-ply angle between adjacent layers) to form a spiral stack, and n+1 represents the total number of layers that make up the MX fabric. The inherent design of the MX already has a partial spiral embedded. In this way, LEP can be produced using only a few layers of material during the layup process, thereby reducing waste, labor costs and manufacturing complexity.

[0052] Suitable fibers that can be used for LEP can include, for example, carbon fibers, glass fibers, aramid fibers, ultra-high molecular weight polyethylene (UHMWPE) fibers, polypropylene (PP) fibers, and various natural fibers. In addition, suitable resin systems can include thermosetting, thermoplastic, glass-like, and self-healing polymer resins formed from synthetic or natural polymer precursors. In order to promote the initiation of failure mechanisms including subcritical damage formation and spiral cracks, the elastic modulus between the resin and the fiber should differ by at least a factor of 10. This will initiate a crack deflection mechanism, which is critical for spirally propagating damage.

[0053] In some embodiments, the spiral stack can be manufactured from NCF reinforcements made from E-glass, which is a typical material used to manufacture blade skins in the wind rotor market, or from natural fiber materials such as flax, sisal, hemp, kenaf, bamboo, etc., which are characterized by excellent damping properties. Since glass fibers have higher performance and are less susceptible to environmental influences such as hygroscopicity, it would be very challenging to completely replace the blades with natural fibers with the same or better performance. However, since LEP only covers a small part of the blade surface, this is a cost-effective solution to introduce a more sustainable material in the wind blade market. In addition, the LEP replaced during maintenance will generate less waste and have a higher grade of recyclable bio-based materials, thereby reducing the environmental footprint of the proposed solution.

[0054] In another embodiment, the spiral stack can be made using a carbon fiber UD prepreg stack of NCF. This will be more relevant to aerospace structures that use carbon fiber materials more widely.

[0055] Graded stiffness for spiral LEP protection can be achieved by mixing the fiber types used in the spiral stack. For example, using flax mixed with glass fibers in a spiral form provides superior impact resistance compared to solutions using only traditional glass. In addition, a hybrid NCF spiral LEP using glass fiber / epoxy materials in the outermost layers of the LEP (only a few layers) can provide appropriate stiffness for rapid stress wave propagation supported by high damping materials (such as flax-epoxy composites). In this way: 1) the graded stiffness will allow the stress wave at the impact point to dissipate faster; 2) part of the glass material, which is poorly recyclable and heavy, can be replaced with flax material, which is a better environmental solution and a lighter material that also provides damping. As described herein, all of the above layers will be at least partially arranged in a spiral stack. In another embodiment, the layers of different fiber types can be dispersed within the thickness of the laminate, rather than being locked together in specific areas of the laminate.

[0056] Spiral reinforcement can also be made with materials that gradually increase in hardness by changing the material composition rather than the fiber structure / ply. This can allow stress waves (e.g., raindrops hitting the surface) to disperse faster, resulting in delayed crack initiation at the surface. For example, such graded materials can be achieved by any of the following ways: 1) different resin systems (e.g., wet layup procedures during each layer of LEP placement before curing or post-curing treatment, or a changed resin and catalyst mixture to increase hardness, or by adding additional phases to the matrix); or 2) different fiber reinforcement and / or fiber treatment. Having harder fibers may help increase the speed of stress wave propagation, depending on the new ratio of the longitudinal modulus and bulk modulus to the new density of the harder fibers. This may help to help the material relax during high-frequency impacts such as raindrops. Another example of a graded spiral material can be achieved by the density difference between the spiral layers. For example, this can be achieved by using NCF or UD fabrics with the same fiber area weight but different deniers. For the same grams per square meter (gsm), the use of low fiber count yarns results in a more uniform fiber distribution, while high fiber count yarns result in a more "inconsistent" fabric. Therefore, for the same fabric fiber area weight, the density distribution of each layer is more uniform at 68 tex, while it has periodic changes at 200 tex.

[0057] In some embodiments, graded hardness spiral protection can be achieved by a step change in hardness characteristics between the spiral composite substrate and the top coating. For example, this can be achieved by applying a coating on the surface of the spiral composite substrate to produce two different regions characterized by uniform hardness.

[0058] The spiral materials described herein can be used to form aerodynamic profiles to prevent cracks from propagating along the underlying structure. For example, Figures 10A to 10C A schematic diagram showing the layer arrangement of a fiber reinforced composite structure 1000 according to an embodiment of the present invention is shown. Fig. 10B yes Fig. 10A and 10C 1000 is a cross-section of a structure shown in perspective. Composite structure 1000 can have a first reinforcing fiber multilayer 1002 defining a first region of a fiber reinforced composite structure, the layer having parallel fibers, and wherein the layer is arranged to provide load-bearing strength for the reinforced composite structure. In the example shown, the first multilayer 1002 includes five layers. The two layers at the bottom are arranged at +80 degrees / -80 degrees, and the three layers thereon are arranged at 0 degrees. In this example, the 0 degree layer is arranged along the axis of an axisymmetric component (e.g., a tubular structure) and provides strength in the main load direction. The +80 degree / -80 degree layer is used to reinforce the 0 degree layer and resist the bending of the axisymmetric component, which may be advantageous in a long and thin tubular structure.

[0059] The second reinforcing fiber multilayer 1004 defines the second region of the fiber reinforced composite material structure, and is arranged in a spiral relationship, wherein the angle between the orientation direction of at least two adjacent layers is greater than 0 degree and less than about 30 degree, so as to provide impact resistance for the enhanced composite structure. In the illustrated example, the layer (starting from the top downwards) is arranged with 70 degree, 65 degree, 60 degree, 55 degree, 50 degree, 45 degree, 40 degree, 30 degree, 20 degree and 10 degree. As described herein, this spiral relationship provides impact resistance for the structure below. Although the second spiral multilayer is illustrated with unidirectional thin layer (TPUD), other layers are illustrated with thick layers, which has advantages in impact resistance, main load bearing capacity and reducing lamination time, but the thickness of each layer can be identical.

[0060] Reference now Fig.11 , an exemplary method 1100 for forming an aerodynamic profile using a reinforced fiber composite material with a spiral structure is provided. The method 1100 can be implemented in a general cost-effective manner using currently used manufacturing techniques and methods, which can be easily integrated in the manufacturing process of the aerodynamic structure to reduce complexity and simplify maintenance operations. In step 1102, a patch of multiple layers of parallel reinforcing fibers can be applied along at least a portion of the length of the aerodynamic profile and on at least the LE of the aerodynamic profile, so that at least a portion of the multiple layers are spirally arranged relative to each other to adjust the stress wave propagation speed and acoustic impedance of the aerodynamic profile and provide load-bearing strength for the aerodynamic profile. In step 1104, the aerodynamic profile can be infused with resin between the reinforcing fibers of each layer of the multiple layers and between adjacent layers of the multiple layers to form a resin matrix. Then, each shell and shear web of the aerodynamic profile can be assembled, for example, by an adhesive. The aerodynamic profile can then be demoulded, trimmed and polished. Alternatively, the patch of spiral graded material can be directly applied to the aerodynamic profile that has already been manufactured for quick replacement and maintenance. This can also protect the aerodynamic profile that is currently in operation and extend its durability and production capacity.

[0061] Although various exemplary embodiments of the present invention have been described above, it is apparent to those skilled in the art that various changes and modifications may be made therein without departing from the present invention. The appended claims are intended to cover all such changes and modifications that fall within the true scope of the present invention.

Claims

1. A device for protecting an aerodynamic profile having a length and a leading edge, the device comprising: a plurality of parallel reinforcing fibers configured to extend along at least a portion of the length of the aerodynamic profile and at least over a leading edge of the aerodynamic profile; and a resin matrix comprising a resin that permeates between the reinforcing fibers of each of the multiple layers and between adjacent layers of the multiple layers, At least a portion of the multiple layers are spirally arranged relative to each other to adjust the stress wave propagation speed and acoustic impedance of the aerodynamic profile, provide load-bearing strength to the aerodynamic profile, and suppress high-frequency impacts generated by impacts on the aerodynamic profile.

2. The apparatus of claim 1 , wherein the aerodynamic profile comprises a wind turbine blade, a fixed leading edge of an aircraft, an open rotor blade, a helicopter blade, a nose cone, an engine air inlet, a pylon, a nacelle, vertical and horizontal stabilizers, propeller blades, fan blades, a mast, a keel, a rudder, a wing, or a forward region of a ship's hull.

3. The apparatus of claim 1, wherein the parallel reinforcing fibers comprise a unidirectional long fiber composite material.

4. The apparatus of claim 1, wherein the parallel reinforcement fibers comprise a non-crimped fabric.

5. The apparatus of claim 4, wherein the non-crimped fabric comprises a biaxial configuration.

6. The apparatus of claim 4, wherein the non-crimped fabric comprises a four-axis configuration.

7. The apparatus of claim 4, wherein the non-crimped fabric comprises at least one of alkali-free glass or a natural fiber material.

8. The device of claim 7, wherein the natural fiber material comprises at least one of flax, sisal, hemp, kenaf, or bamboo.

9. The apparatus of claim 1, wherein the parallel reinforcing fibers comprise at least one of carbon fibers, glass fibers, aramid fibers, ultra-high molecular weight polyethylene (UHMWPE) fibers, polypropylene (PP) fibers, or natural fibers.

10. The device of claim 1, wherein the resin comprises at least one of a thermosetting resin or a thermoplastic resin.

11. The device of claim 1 , wherein the difference in elastic modulus between the resin and the parallel reinforcing fibers is at least ten times.

12. The apparatus of claim 1, wherein the impact comprises at least one of raindrops, hail, dust, ice, sand, or salt.

13. The device of claim 1, wherein at least a portion of the multiple layers are spirally arranged relative to each other in an asymmetrical manner.

14. The device of claim 1, wherein at least a portion of the multiple layers are spirally arranged relative to each other in an unbalanced manner.

15. The apparatus of claim 1, wherein at least a portion of the multiple layers extending over the leading edge of the aerodynamic profile includes a pitch angle of 20 to 30 degrees.

16. The device of claim 1, wherein at least one of a resin system, fiber reinforcement, or fiber treatment of the device is selected to adjust the stiffness of the aerodynamic profile to adjust the stress wave propagation speed and acoustic impedance of the aerodynamic profile.

17. The device of claim 1, wherein the plurality of layers comprises a first plurality of layers of parallel reinforcing fibers that are not arranged in a spiral relationship to provide load bearing strength for an aerodynamic profile, and The angle between the orientation directions of a first pair of adjacent layers of the first multilayer is 30° or greater.

18. The device according to claim 17, wherein the angle between the orientation directions of at least another pair of adjacent layers of the first multilayer is 30° or more.

19. The apparatus of claim 17, wherein the plurality of layers comprises a plurality of layers of second parallel reinforcing fibers arranged in a spiral relationship, and The angle between the orientation directions of at least two adjacent layers is greater than 0° and less than about 30° to provide impact resistance to the aerodynamic profile.

20. The device of claim 1, further comprising a top coating coupled to the multiple layers.

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