High impact resistant reinforced fibres for leading edge protection of aerodynamic structures.

Abstract

Systems and methods are provided for protecting aerodynamic structures, such as wind turbine blades, rotor blades, aerodynamic aircraft structures, etc. Long fiber reinforced composite materials with helicoidal structures having materials aligned with graded hardness and stiffness are used to develop efficient, highly tunable leading edge protection (LEP) solutions that have longer durability than conventional solutions, while resulting in a lighter, and optionally more environmentally sustainable solution. At least a portion of the multiple plies are helicoidally arranged relative to one another to tailor the stress wave propagation velocity of the aerodynamic blade and provide the aerodynamic blade's load-bearing strength.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority to U.S. Provisional Patent Application No. 63 / 367,085, filed June 27, 2022, the entire contents of which are incorporated herein by reference.

[0002] FIELD OF THE DISCLOSURE

[0002] This disclosure is directed to materials having a helicoidal architecture to protect their aerodynamic profile. [Background technology]

[0003]

[0003] Aerodynamic profiles are highly engineered to provide superior aerodynamic efficiency. This can only be guaranteed if the shape of the aerodynamic profile does not change over time and if the surface of the profile is maintained in its originally manufactured state so that the airflow around the profile does not change. Therefore, erosion of the leading edge (LE) of an aerodynamic profile due to high-frequency impact and the resulting damage from liquid and solid particles, such as rain, oil, water, sand, salt, and dust, can cause a significant reduction in aerodynamic efficiency. For aerostructures, including rotor blades for drones, commercial aircraft, military aircraft, and helicopters, this can lead to increased drag and subsequent fuel consumption. Changes in the aerodynamic properties of the profile can also lead to changes in load distribution, resulting in vibrations and, in some cases, serious structural damage. For rotor blades, this can lead to reduced power generation for a wide range of applications, including wind energy production, jet engine efficiency, power generation for submarine propellers, and stationary gas and hydro turbines. Similar issues affect aerodynamic profiles for marine applications, including but not limited to fins, master poles, and submarine profiles.

[0004]

[0004] In commercial and military aircraft, erosion of aerodynamic surfaces and surfaces exposed to forward-facing flow is highly susceptible to erosion from both liquid and solid-derived particles. These include, but are not limited to, rain, sand, salt, dust, ash, hail, and ice. Forward-facing areas of an aircraft are susceptible to erosion, including, but not limited to, the nose cone, wing leading edges (LEs), engine intakes, pylons, nacelles, vertical and horizontal stabilizers, and rotating blades, including aircraft engine fan, compressor, and turbine blades, as well as propeller blades.

[0005] In marine applications, erosion caused by liquid and / or solid-derived particles can occur on the hydrodynamic and aerodynamic surfaces of boats / vessels. These include, but are not limited to, salt, dust, sand, and debris. Areas such as the forward-facing surfaces of a vessel or boat, including, but not limited to, propeller blades, masts, wings, rudders, keels, hulls, etc., can be damaged by erosion.

[0006]

[0006] Wind turbine rotor blades are key components for capturing and converting wind energy into electricity. To maximize a wind turbine's annual electricity production (AEP), two important parameters must be considered: 1) locations with high and consistent wind speeds, and 2) the capacity and efficiency of the wind turbine design. For these reasons, operators and wind turbine manufacturers have developed larger-capacity turbines with longer rotor blades that result in higher blade speeds and have chosen locations such as offshore areas that experience higher wind environments. As a result, the blades are exposed to more extreme conditions and experience more extreme durability challenges over their lifetime, including impacts, erosion, abrasion, ultraviolet radiation, thermal fluctuations, lightning strikes, ice, and hailstones. AEP is often significantly impacted by these issues, first resulting in reduced aerodynamic efficiency as the blade leading edges begin to erode, then requiring maintenance, and ultimately resulting in a complete blade replacement or wind turbine shutdown if not repaired. A recent study estimated that blade roughness caused by rain erosion reduces aerodynamics, and the severity of the erosion process ultimately reduces power production by 3% to 30% of a wind turbine's capacity. Companies still engage in costly inspection and maintenance programs to repair damaged blades throughout the life of a wind turbine, because maximizing power generation efficiency far outweighs these costs.

[0007]

[0007] As knowledge and experience regarding blade dynamics has increased, the industry has been able to increase rotor blade lengths, resulting in tip speeds of up to 130-160 meters per second. At these high speeds, extreme deteriorating phenomena—rain erosion on the blade's leading edge, impacts with objects (e.g., hailstones, birds, insects, rain, hail, salt) on the pressure side, and high stresses on the blade structure—demand high performance from critical areas of the blade. Specifically, during operation, blades are subject to damage at varying levels of severity, from surface damage that impacts efficiency to structural damage that can lead to complete failure and premature end of life.

[0008]

[0008] Therefore, blades require expensive maintenance and repair to ensure maximum performance and energy output during service operation, along with the cost of additional downtime. Therefore, monitoring and maintaining blades to maximize electrical production and ensure a mechanically robust structure is constantly monitored for cost-benefit analysis. The wind turbine industry has focused on improving the overall durability of blades. The area that has received the most focus and attention is Leading Edge Protection (LEP).

[0009] Current LEP products, including solutions for wind rotor blades and aviation structures, have proven unsatisfactory due to difficult applications and disappointing lifespan results, including those affected by impact damage caused by rain, sand, dust, hash, oil, salt, hail, and bird strikes. Rather than relying on ineffective LEPs, most OEMs have adopted minimal wall thickness or metal shielding (particularly in aerospace applications) to improve impact resistance. Both solutions increase blade costs, make the blade heavier, and create challenges in achieving good bonding between dissimilar materials and matching dissimilar materials to achieve similar bending characteristics required during operation. Subsequently, for rotating propellers and blades, adding weight to the blade requires more energy to rotate the blade, thereby reducing overall energy efficiency and power production. Furthermore, for fixed aerodynamic surfaces, such as the leading edge of an aircraft wing, increases the overall weight of the structure, thereby increasing overall manufacturing costs and fuel consumption during operation.

[0010] The most common solutions proposed to increase leading edge robustness against erosion rely on the use of metal shields in aerospace applications, and polymer-based coatings and paints such as 3M Wind Blade Protection Coating W4600 and W4601, ReNEW W-Series, HC05XP1 (available from Hontek, South Windsor, Connecticut), or RELEST Wind coat (available from BASF, Ludwigshafen, Germany) for wind energy generation and helicopter blade solutions. The thicker the coating, the longer the protection against rain erosion. However, increasing the thickness during manufacturing requires multiple coats with drying times between them. The results are: 1) increased labor costs; 2) weak interfaces between coating layers impair protection; 3) coatings often delaminate, resulting in flying parts that reduce aerodynamic efficiency and increase noise; 4) while the use of such coatings helps with erosion resistance, they fail to protect against more severe impact damage from hailstones, birds, or lightning strikes; and 5) because these coatings are applied by hand using brush or spray techniques, the thickness of the coating layer often varies, resulting in impaired geometric stability and aerodynamic performance. This last aspect can be prevented by using protective tape. However, this option presents the same limitations as 1-4 above.

[0011] Other proposed solutions, such as those described in WO 2008 / 157013 and WO 2013 / 092211, use shields and covers that are manufactured before being placed on the finished blade. The main drawbacks of such solutions are: 1) the difficulty of ensuring the correct geometric stability of such thin and narrow protective covers; 2) the difficulty of handling small and thin covers during assembly, with the blade shield being very flexible due to its long dimension; 3) the need for an additional manufacturing step, requiring an additional mold to form the shell into the complex LE profile; and 4) the increased number of parts increases manufacturing complexity, cost, and the risk of defects due to imperfect integration.

[0012] Additionally, WO 2017 / 198167 describes a proposed solution using a co-curing process in which the proposed LEP is constructed together with the rest of the profile. The proposed solution uses one or more layers of short-fiber mats or woven fabrics impregnated with paint or coating material, while fiber reinforcement is used to build thickness and avoid inconsistencies in the coating, leading to more uniform protection. This thicker fabric also helps reduce crack propagation and protects against more severe damage, such as damage from hailstone impacts.

[0013]

[0013] In particular, liquid- and solid-induced erosion phenomena have often been treated as surface problems, but not as low-energy, high-repetition impact problems. The high tip speeds (up to 160 m / s) reached by blades lead to impact fatigue phenomena, where high-frequency, low-mass (0.015 g), low-energy (approximately 0.12 J) impacts occur on the blade surface. In the case of liquid droplets, the droplet impact generates powerful water hammer pressures of up to approximately 134 MPa, which approach, if not exceed, the strength of the standard polymer resins used in the FRP (commonly made by embedding glass fibers in thermosetting resins in wind rotor blade applications) that make up the blade skin.

[0014] A better solution would be to quickly dissipate energy in-plane rather than through-thickness to avoid damage localization, and ultimately to have a high damping coefficient to further dissipate the energy carried by such stress waves. Stress wave propagation can be controlled by changing the impedance of the impacted material (i.e., LEP) by altering the components that make up the material or the structure (i.e., microstructure) of how such components are arranged. In such stress wave-dominated problem scenarios, reinforcements such as short fiber and woven composites (as per WO 2017 / 198167) are not the optimal choice. Crimps in woven materials and fiber ends in short fiber composites present sites of stress concentration and areas subject to stress wave reflection. This results in increased damage formation in substrates subjected to both rain impact and larger mass impact. Furthermore, woven and short fiber structures create several resin-reached regions. These act as crack nucleation sites due to the change in impedance between the fiber-reached and resin-reached regions.

[0015] An additional problem with current LEP solutions is the requirement to use higher performance materials, such as fiberglass or high strength metal shielding, which unfortunately have a negative impact on the environmental footprint. Indeed, no solutions are available that use bio-based products for both the polymer and the reinforcement.

[0016]

[0016] In view of the aforementioned shortcomings of previously known systems and methods, a need exists for a technology that can utilize materials that allow acceptable performance while providing an improved environmental footprint in applications where aerodynamic profiles are subject to water / sand / dust erosion, such as wind blades, aerodynamic surfaces of aircraft structures, and rotor blade applications. Sustainable materials such as natural fiber composites are estimated to have a 50% lower carbon footprint compared to glass fiber composites and exhibit up to 70% reduction in greenhouse gas emissions compared to functionally equivalent fossil-based counterparts.

[0017] It would be further desirable to provide an LEP solution that can tailor the stress wave propagation velocity of the aerodynamic structure and also provide load-bearing strength for the aerodynamic structure. Summary of the Invention

[0018]

[0018] The present disclosure overcomes the shortcomings of previously known systems and methods by providing an LEP solution that utilizes the use of long fiber helicoidal laminates with gradient material properties to provide better rain / sand / dust / water erosion protection.

[0019] For example, an apparatus for protecting an aerodynamic profile having a length and a leading edge is provided. The apparatus may include a plurality of plies (also referred to as layers) of parallel reinforcing fibers extending along at least a portion of the length of the aerodynamic profile and across at least the leading edge of the aerodynamic profile, and a resin matrix including a resin impregnated between the reinforcing fibers of each of the plurality of plies and between adjacent plies of the plurality of plies. Furthermore, at least a portion of the plurality of plies may be helicoidally arranged relative to one another to adjust the stress wave propagation velocity and acoustic impedance of the aerodynamic profile, impart load-bearing strength to the aerodynamic profile, and attenuate high-frequency shocks generated by an impact on the aerodynamic profile. For example, the impact may be at least one of raindrops, hail, dust, ice, sand, or salt.

[0020] The aerodynamic profile may be a wind turbine blade, an aircraft fixed leading edge, an open rotor blade, a helicopter blade, a nose cone, an engine intake, a pylon, a nacelle, vertical and horizontal stabilizers, a propeller blade, a fan blade, a mast, a keel, a rudder, a wing, or a forward-facing area of a ship's hull. The parallel reinforcing fibers may include a unidirectional long-fiber composite material and / or a non-crimp fabric. For example, the non-crimp fabric may include a biaxial and / or a quadaxial configuration and may include at least one of E-glass or a natural fiber material. For example, the natural fiber material may include at least one of flax, sisal, hemp, kenaf, or bamboo. Additionally, the parallel reinforcing fibers may include at least one of carbon, glass, aramid, ultra-high molecular weight polyethylene (UHMWPE), polypropylene (PP), or a natural fiber.

[0021] The resin may include at least one of a thermosetting resin or a thermoplastic resin. Furthermore, the difference in modulus between the resin and the parallel reinforcing fibers may be at least 10 times. At least a portion of the plurality of plies may be helicoidally arranged relative to one another in an asymmetric and / or unbalanced manner. At least a portion of the plurality of plies extending across the leading edge of the aerodynamic profile may include a pitch angle between 20 and 30 degrees. Additionally, at least one of the resin system, fiber reinforcement, or fiber treatment of the device may be selected to adjust the stiffness of the aerodynamic profile, thereby adjusting the stress wave propagation velocity and acoustic impedance of the aerodynamic profile.

[0022] Further, the plurality of plies may include a first plurality of plies of parallel reinforcing fibers not arranged in a helicoidal relationship to impart load-bearing strength to the aerodynamic profile, such that the included angle between the orientation directions of a first pair of adjacent plies of the first plurality of plies may be 30° or greater. Additionally, the included angle between the orientation directions of at least one other adjacent pair of plies of the first plurality of plies may be 30° or greater. The plurality of plies may include a second plurality of plies of parallel reinforcing fibers arranged in a helicoidal relationship, such that the included angle between the orientation directions of at least two adjacent plies may be greater than 0° and less than about 30° to impart impact resistance to the reinforced composite structure, e.g., the aerodynamic profile. The device may further include a top coating bonded to the plurality of plies. [Brief explanation of the drawings]

[0023] [Figure 1A]

[0023] Various views of the leading edge structure of a wind energy blade. [Figure 1B]

[0024] FIG. 1 is a diagram of a composite sandwich structure. [Figure 1C]

[0025] 1 is a schematic diagram of areas of an aircraft that are subject to liquid and / or solid particle impacts that can lead to erosion of aerodynamic surfaces. [Figure 1D]

[0026] 1A-1C are diagrams of various blades and aerodynamic profiles that can benefit from reducing the effects of liquid-borne or solid-borne erosion in accordance with the principles of the present disclosure. [Figure 2]

[0027] 1 is a diagram of an exemplary blade manufacturing process. [Figure 3]

[0028] FIG. 10 is a diagram illustrating an example of a helicoid shape. [Figure 4]

[0029] FIG. 1 is a diagram of a stack of fiber layers arranged in a helicoidal pattern in accordance with the principles of the present disclosure. [Figure 5]

[0030] FIG. 5A is a diagram of a helicoidal preform made by arranging straight fibers into a 3D curved shape in accordance with the principles of the present disclosure.

[0031] FIG. 5B is a diagram of a helicoid preform made by arranging curved fibers in a 2D shape in accordance with the principles of the present disclosure. [Figure 6]

[0032] FIG. 1 is a diagram of a helicoidal laminate stack. [Figure 7]

[0033] Figure 7A is a diagram of a unidirectional material configuration, and Figure 7B is a diagram of a non-crimped multiaxial material configuration. [Figure 8]

[0034] FIG. 1 shows the results of rain erosion tests (ASTM G76) performed on two aerodynamic profiles representative of the leading edge of a wind rotor blade. [Figure 9]

[0035] 1 is a schematic diagram of a possible configuration of a leading edge protection having at least a partially helicoidally arranged fiber reinforcement structure in accordance with the principles of the present disclosure; [Figure 10]

[0036] Figure 10A is a schematic diagram of a structure that includes both impact resistance and load-bearing strength; Figure 10B is a schematic diagram of a structure that includes both impact resistance and load-bearing strength; and Figure 10C is a schematic diagram of a structure that includes both impact resistance and load-bearing strength. [Figure 11]

[0037] 3 is a flowchart illustrating exemplary method steps for forming an aerodynamic blade having a helicoidal configuration in accordance with the principles of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0024]

[0038] The present disclosure overcomes the shortcomings of previously known systems and methods by providing a LEP solution for a general aerodynamic profile that utilizes the use of long-fiber helicoidal laminates with graded material properties, leading to improved erosion and impact protection. Figure 1A illustrates an LE structure employed in a wind energy blade, such as a wind turbine blade. As shown in Figure 1A, 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 leading edge (LE) structure may include a monolithic composite material. For example, the leading edge structure may include 500-1000 μm of filler material (putty) sandwiched between two to three layers of a 500-1000 μm LEP coating and a 0.8-1.6 mm biaxial layer of glass fiber (epoxy). Additionally, the leading edge (LE) of the wind turbine blade 100 may include a bonded joint. Additionally, the shell structure of the wind turbine blade 100 may include a sandwich composite formed by a foam core (FC) sandwiched between adjacent layers of FRP facings.

[0025]

[0039] For example, as shown in Figure 1B, placing a material, such as a polymer layer, on a foam between skins in a composite laminate creates a synergistic structural morphology in which the skins provide bending stiffness and the sandwich material provides shear stiffness and buckling resistance. Compared to monolithic laminate composites, sandwich panels can exhibit improved strength-to-weight ratios, sound damping, fatigue resistance, thermal insulation, and impact / damage resistance. The crash performance of sandwich panels can be superior to laminates because some of the energy associated with an impact can be dissipated as elastic deformation instead of matrix and / or fiber damage, and / or the core can cushion inertial loads while the skins absorb the energy. However, while laminate composites can deform, the coatings often used in these applications do not have the same bending properties, which can result in cracks that substantially reduce performance and premature endurance. The morphology of the skins, the type / structural properties of the core, and the boundary conditions of the laminate govern crash behavior. Typically, in sandwich designs, the skins are relatively thin, and the core is bonded to the skins with adhesives. Structural and failure mechanisms that make sandwiches unsuitable for some applications include: a) limited bond area and strength may cause the skins to separate prematurely from the core during an impact, b) the skins are thinner than comparable laminate designs, which may initiate fiber breakage, fiber matrix delamination, and laminate delamination at lower impact levels, c) the core may collapse or shear, and d) in-plane structural properties such as compression, tensile, strength, and stiffness may be degraded by replacing laminate plies with sandwich material.

[0026]

[0040] Figure 1C illustrates areas of aircraft structures that can be improved using the inventions disclosed herein. Figure 1D illustrates other types of blades and aerodynamic profile structures found in other industrial applications that would benefit from the disclosed inventions to reduce the effects of liquid- or solid-induced erosion. These include, but are not limited to, propeller blades, wing leading edges, aircraft engine inlets, engine nacelles, nose cones, helicopter blades, compressor / turbine blades, and open-rotor propellers in aviation and marine applications.

[0027]

[0041] The solution described herein is based on the use of long (>2 mm) fiber-reinforced composite materials with helicoidal structures, such as those described in U.S. Patent Application Publication Nos. 2021 / 0316528 and 2021 / 0339499, assigned to the assignee of the present application and each of which is incorporated herein by reference in its entirety, in which the materials are aligned with graded hardness and stiffness, to develop an efficient and highly tunable LEP solution that has longer durability than conventional solutions, while resulting in a lighter, and optionally more environmentally sustainable solution.

[0028]

[0042] Next, referring to Figures 2A-2D, an example of a blade manufacturing process will be described for a wind turbine rotor blade. Long-fiber-reinforced composite materials with helicoidal structures may be applied to wind turbine blades during material preparation, such as the fiber core, as shown in Figure 2A. The use of such high-impact-resistant fiber-reinforced LEP reduces the amount of coating required to protect against rain erosion, protects against more catastrophic events such as bird strikes or lightning strikes, and holds the potential to further reduce the structural weight of the blade, which could result in longer blades with higher energy production. As described in more detail below, resin infusion may be performed on the absorption and pressure sides of the wind turbine blade, as shown in Figure 2B. Furthermore, the shells and shear webs of the wind turbine blade may be assembled, for example, with adhesives, as shown in Figure 2C, and the wind turbine blade may be demolded, shaped, and polished as shown in Figure 2D.

[0029]

[0043] Contrary to previously proposed solutions using woven long fiber composites, the present disclosure uses gradient long fiber composites with a helicoidal structure, such as the helicoidal shape shown in FIG. 3. As used herein, the term "helicoidal" refers to a stacked construction of fiber plies in which the fibers of at least one ply define an orientation direction that forms an included angle greater than 0 degrees and less than about 30 degrees with respect to the orientation direction of the fibers of an adjacent ply, as shown in FIG. 4. The stacked construction may include adjacent plies that define included angles outside this range, and the stacked construction may have an angle less than one full 360-degree revolution or greater than one full revolution. The fiber orientation direction of one or more plies may be straight or curved. For example, FIG. 5A shows a helicoidal preform made with straight fibers arranged in a 3D curved shape, and FIG. 5B shows a helicoidal preform made with curved fibers arranged in a 2D shape.

[0030]

[0044] For example, Figure 6 illustrates a fiber-reinforced elastic composite ply layup scheme in which individual plies are rotated along the longitudinal or x-axis at a predetermined angle relative to adjacent plies to produce a z-directional helicoidal fiber-oriented laminate. The image on the left uses a single line to represent each ply layer (lamina), highlighting the resulting z-directional helicoidal spiral. The image on the right more realistically illustrates the constituent layers of the helicoidal layup using fiber bundles (typically tows consisting of 3,000 to 50,000 or more fibers). Subsequent close-up views show how the helicoidal laminate stack is formed from the individual lamina formed with the fiber tows and resin. The helicoidal clocking may be selected to produce a specific helical pitch or circularly polarized z-oriented fibers that are sufficiently close together to exhibit significant interlaminar direct load sharing between the laminate fibers.

[0031]

[0045] The ability of the fibers to share loads directly between the thin plies is a significant contributor to the ability of helicoidal laminates to absorb and dissipate impact forces more efficiently than traditional composite layups and minimize the effects of impact fatigue. Furthermore, the spirals formed from these angled fiber assemblies can be tuned to specific wavelengths to attenuate propagating shock waves initiated by impact forces on aerodynamic profiles, can be filled with matrices containing microspheres or reinforcing particles to further prevent or arrest the propagation of catastrophic fractures, and can be made to exploit differences in modulus between the fibers and resin to further arrest fractures generated from blunt or sharp impacts.

[0032]

[0046] Additionally, gradient long-fiber composites can be in the form of unidirectional (UD) and / or non-crimp fabrics (NCF), which allow for: 1) fibers to remain straight, avoiding areas where stress waves generated during the erosion process are blocked and reflected (such as by crimped areas in the fabric or the ends of short fibers) and create damage; 2) more uniform in-plane stress wave distribution, allowing for rapid dispersal of stress waves; and 3) tailoring stress wave distribution through the thickness for optimal attenuation in 3D space. For example, Figure 7A shows an example of a UD fabric, and Figure 7B shows an example of a non-crimp multiaxial fabric. Overall, the combined effect of these features allows the material to: 1) relax quickly before subsequent impact events; 2) better attenuate high-frequency impacts generated by repeated water droplets, sand, or salt; and 3) better spread energy in-plane, resulting in less localized damage.

[0033]

[0047] The fiber structure of the layup should include, at least in part, a helicoidal layup. In the context of wind rotor blades, using ASTM G76 testing, it was demonstrated that the helicoidal layup described herein can significantly reduce eroded mass by approximately 34% compared to conventional layups used in wind blade applications, as shown in Figure 8. This is achieved by the helicoidal fiber construct being able to better attenuate stress waves, thereby dissipating them away from the impact location and diffusing damage in-plane by forming subcritical matrix damage that can dissipate impact energy while maintaining structural integrity. Figure 8 shows one profile utilizing conventionally constructed NCF fibers used in field applications and an aerodynamic profile featuring helicoidally arranged NCF fibers.

[0034]

[0048] Figure 9 shows a schematic of a possible structure of leading edge protection with at least a partially helicoidally arranged fiber reinforcement structure, potentially in combination with other material components, to tailor the stress wave propagation characteristics of multiple material solutions, with the aim of improving erosion and impact resistance.

[0035]

[0049] In some embodiments, the helicoidal layup may be asymmetric and / or unbalanced. For example, the LEP region has high curvature and is limited to a small region of a much larger structure, so the effects of rigid bonding may not be relevant. Furthermore, the pitch angle may be held constant or varied to tailor performance. This is to promote specific types of damage within the composite, such as delamination between the helicoidal plies, which further aids in dissipating energy and reducing damage. For example, using a larger pitch angle (between 20° and 30°) on the side of the LEP closer to the blade surface can prevent cracks from initially forming on the top or outer surface of the blade.

[0036]

[0050] As explained above, gradient long fiber composites with helicoidal structures, such as helicoidal stacks, can be made using NCFs. Long fiber NCFs are typical fabrics used in the manufacture of wind blade skins and aircraft wing skins, making LEPs easier to manufacture and handle. NCFs can be biaxial (BX), such as X° / -X° plies slightly rotated to create a helicoidal layup, or X° / X°+α / X°+2α / X°+3α / ... / X°+n * This can be achieved by developing a multiaxial (MX) fabric with a layup of α, where α represents the inter-ply angle between adjacent plies to form a helicoidal layup, and n+1 represents the total number of plies that make up the MX fabric. MX-specific designs already incorporate a partial helicoid. This allows for the production of LEPs using only a few layers of material during layup, minimizing waste and reducing labor costs and manufacturing complexity.

[0037]

[0051] Suitable fibers that can be used in LEPs include, for example, carbon, glass, aramid, ultra-high molecular weight polyethylene (UHMWPE), polypropylene (PP), and various natural fibers. Additionally, suitable resin systems include thermoset, thermoplastic, vitrimer, and self-healing polymer resins formed from either synthetic or natural polymer precursors. To favor the activation of fracture mechanisms, including non-critical damage formation and spiral cracking, the difference in elastic modulus between the resin and fiber should be at least 10 times. This activates the crack deflection mechanism, which is crucial for helicoidal damage propagation.

[0038]

[0052] In some embodiments, the helicoidal stack can be made using E-glass, a typical material used to make blade skins in the wind rotor market, or NCF reinforcement made from natural fiber materials such as flax, sisal, hemp, kenaf, and bamboo, which are characterized by their excellent damping properties. Because glass fiber has high performance and is less susceptible to environmental influences such as moisture absorption, it would be very difficult to completely replace blades with natural fibers with comparable or better performance. However, because LEP only covers a small portion of the blade surface, this represents a cost-effective solution for introducing more sustainable materials to the wind blade market. Furthermore, LEP replacement during maintenance reduces the environmental footprint of the proposed solution by generating less waste and using a higher grade of recyclable and bio-based materials.

[0039]

[0053] In another embodiment, the helicoidal stack can be made using an NCF carbon fiber UD prepreg stack, which would be more relevant to aerostructures that make more extensive use of carbon fiber materials.

[0040]

[0054] The graded hardness of the helicoidal LEP protection can be achieved by hybridizing the fiber types used within the helicoidal layup. For example, using flax hybridized with glass fiber in a helicoidal configuration can provide superior impact resistance compared to traditional glass-only solutions. Furthermore, a hybrid NCF helicoidal LEP using glass fiber / epoxy materials in the outermost layers (only a few layers) of the LEP can provide the appropriate hardness for rapid stress wave propagation, supported by a highly damping material such as a flax-epoxy composite. In this way, 1) the graded hardness allows for faster dissipation of stress waves at the impact point, and 2) some of the less recyclable and heavier glass material can be replaced with a lighter flax material, which is a better environmental solution and also provides damping. All of the aforementioned layers are at least partially configured into a helicoidal layup as described herein. In another embodiment, layers of different fiber types may be distributed within the thickness of the laminate rather than being formed together in specific areas of the laminate.

[0041]

[0055] Helicoidal reinforcement can also be constructed using materials with a graded hardness achieved by varying the material composition rather than the fiber structure / layup. This may allow for quicker stress wave dispersion when, for example, a raindrop impacts the surface, thereby delaying the onset of cracks at the surface. For example, such a graded material can be achieved using either: 1) a different resin system (e.g., a wet layup procedure when placing each layer of LEP, pre- or post-cure treatment, or varying the resin-to-catalyst mix ratio to increase hardness or add additional phases to the matrix), or 2) different fiber reinforcement and / or fiber treatment. Having stiffer fibers can help increase stress wave propagation velocity, depending on the new ratio of longitudinal modulus to bulk modulus relative to the new density of the stiffer fibers. This can be beneficial, for example, in helping the material relax during high-frequency impacts of raindrops. Another example of a graded helicoidal material can be achieved by targeting density differences between helicoidal layers. For example, this can be achieved by using NCF or UD fabrics with the same fiber areal weight but different yarn sizes. For the same grams per square meter (gsm), using a lower count yarn results in a more uniform distribution of fibers, while a higher count yarn results in a less "consistent" fabric. Thus, for fabrics of the same fiber areal weight, the density distribution in each ply will be more uniform at 68 tex, but will vary periodically at 200 tex.

[0042]

[0056] In some embodiments, the gradient hardness helicoidal protection can be achieved by grading the hardness characteristics between the helicoidal composite substrate and the top coating. For example, this can be achieved by spreading the coating over the surface of the helicoidal composite substrate to create two distinct regions characterized by uniform, homogenized hardness.

[0043]

[0057] The helicoidal materials described herein can be used to create an aerodynamic profile to prevent cracks from propagating along a substructure. For example, FIGS. 10A-10C show schematic diagrams of ply configurations for a fiber-reinforced composite structure 1000 according to an embodiment of the present disclosure. FIG. 10B depicts a cross-section of the structure shown in perspective in FIGS. 10A and 10C. The composite structure 1000 can have a first plurality of plies 1002 of reinforcing fibers defining a first region of the fiber-reinforced composite structure, the plies having parallel fibers and arranged to provide load-bearing strength to the reinforced composite structure. In the illustrated example, the first plurality of plies 1002 includes five plies. The bottom two plies are arranged at +80° / -80°, and the three plies above them are all arranged at 0°. In this example, the 0° plies are arranged along the axis of an axisymmetric section, such as a tubular structure, to provide strength in the direction of the primary load. The +80° / -80° plies reinforce the 0° plies and serve to resist buckling in axisymmetric sections, which can be advantageous in slender tubular structures.

[0044]

[0058] A second plurality of plies 1004 of reinforcing fibers defines a second region of the fiber-reinforced composite structure and is arranged in a helicoidal relationship, with the included angle between the orientation directions of at least two adjacent plies being greater than 0 degrees and less than about 30 degrees to provide impact resistance to the reinforced composite structure. In the illustrated example, the plies are arranged (from top to bottom) at 70 degrees, 65 degrees, 60 degrees, 55 degrees, 50 degrees, 45 degrees, 40 degrees, 30 degrees, 20 degrees, and 10 degrees. As described herein, this helicoidal relationship provides impact resistance to the underlying structure. While the second plurality of helicoidal plies are shown as thin ply unidirectional (TPUD) plies and the other plies are shown as thick plies, which provides advantages in terms of impact resistance, primary load carrying capacity, and reduced layup time, the ply thickness may be the same for each ply.

[0045]

[0059] Referring now to FIG. 11 , an exemplary method 1100 for forming an aerodynamic profile from a reinforced fiber composite material having a helicoidal 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 incorporated into the manufacturing process of aerodynamic structures to reduce complexity and facilitate maintenance operations. In step 1102, patches of multiple plies of parallel reinforcing fibers can be applied along at least a portion of the length of the aerodynamic profile, spanning at least the LE of the aerodynamic profile, so that at least a portion of the multiple plies are helicoidally arranged relative to each other to adjust the stress wave propagation velocity and acoustic impedance of the aerodynamic profile and impart load-bearing strength to the aerodynamic profile. In step 1104, the aerodynamic profile can be co-injected with resin between the reinforcing fibers of each ply of the multiple plies and between adjacent plies of the multiple plies to form a resin matrix. The shells and shear webs of the aerodynamic profile can then be assembled, for example, by adhesive. The aerodynamic profile can then be demolded, shaped, and polished. Alternatively, patches of helicoidal gradient material can be applied directly to already manufactured aerodynamic profiles for quick replacement and maintenance, thereby protecting currently operational aerodynamic profiles and improving their durability and productivity.

[0046]

[0060] While various illustrative embodiments of the present invention have been described above, it will be apparent to those skilled in the art that various changes and modifications can be made thereto without departing from the invention. It is intended that the appended claims cover all such changes and modifications that fall within the true scope of the invention.

Claims

1. 1. An apparatus for protecting an aerodynamic profile having a length and a leading edge, comprising: a plurality of plies of parallel reinforcing fibers configured to extend across at least the leading edge of the aerodynamic profile along at least a portion of the length of the aerodynamic profile; a resin matrix containing a resin infiltrated between the reinforcing fibers of each of the plurality of plies and between adjacent plies of the plurality of plies; Equipped with an apparatus, wherein at least a portion of the plurality of plies are helicoidally arranged relative to one another to adjust the stress wave propagation velocity and acoustic impedance of the aerodynamic profile, provide load-bearing strength to the aerodynamic profile, and attenuate high-frequency shocks generated by impacts on the aerodynamic profile.

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

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

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

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

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

7. 5. The apparatus of claim 4, wherein the non-crimp fabric comprises at least one of E-glass or natural fiber material.

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

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

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

11. 10. The apparatus of claim 1, wherein the difference in modulus between the resin and the parallel reinforcing fibers is at least 10 times.

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

13. The apparatus of claim 1 , wherein at least a portion of the plurality of plies are helicoidally disposed relative to one another in an asymmetrical manner.

14. The apparatus of claim 1 , wherein at least a portion of the plurality of plies are helicoidally disposed relative to one another in an unbalanced manner.

15. The apparatus of claim 1 , wherein at least a portion of the plurality of plies extending across the leading edge of the aerodynamic profile include a pitch angle between 20 and 30 degrees.

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

17. 2. The apparatus of claim 1, wherein the plurality of plies includes a first plurality of plies of parallel reinforcing fibers not arranged in a helicoidal relationship to provide load-bearing strength to the aerodynamic profile; the included angle between orientation directions of a first pair of adjacent plies of the first plurality of plies is 30° or greater.

18. 18. The apparatus of claim 17, wherein an included angle between orientation directions of at least one other adjacent pair of plies of the first plurality of plies is 30 degrees or greater.

19. 18. The apparatus of claim 17, wherein the plurality of plies includes a second plurality of plies of parallel reinforcing fibers arranged in a helicoidal relationship; The apparatus, wherein an included angle between orientation directions of at least two adjacent plies is greater than 0° and less than about 30° to provide crashworthiness to said aerodynamic profile.

20. The apparatus of claim 1 further comprising a top coating bonded to the plurality of plies.

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