Methods for producing a non-crimped fabric having a binder and a composite structure including the non-crimped fabric, and a preform including the non-crimped fabric having a binder.

Abstract

In particular, in the field of non-crimped fabrics and composite preforms, this invention provides a method for manufacturing non-crimped fabrics that enhances the stability of preforms, improves handling efficiency, and optimizes resin injection technology for larger or more complex structures. [Solution] A method for producing a non-crimped fabric includes providing multiple layers of continuous fibers held together by stitch threads, and adding a binder between adjacent layers of the multiple layers of continuous fibers and on the outer layers of the multiple layers of continuous fibers. In this case, the binder has an activation temperature below the melting temperature of the stitch threads.

Description

Technical Field

[0001]

[0001] This application relates to the field of composite materials, and more particularly to non-crimp fabrics designed to be used in high-performance composite structures. Such non-crimp fabrics are used in industries such as aerospace, automotive, and renewable energy.

Background Art

[0002]

[0002] Non-crimp fabrics are widely used in composite manufacturing due to their ability to align continuous fibers without crimping, improving mechanical properties such as the strength and stiffness of the final composite structure. The layers within a non-crimp fabric are typically fixed by stitching, which includes fine filament stitch threads, creating a stable configuration without crimps that supports effective load transfer along the fibers and promotes resin flow during composite processing. Stitching includes various stitching styles such as chain, lock, or tricot stitches that use threads made from one or more yarns twisted and / or coiled to form each thread. The stitch threads can include continuous or discontinuous filaments. This configuration makes non-crimp fabrics valuable in applications where lightweight and high integrity structures are desired.

[0003]

[0003] A common prior art approach for maintaining the stability of a preform of a non-crimp fabric during handling and processing is the application of a tackifying agent. This tackifying agent provides temporary adhesion between layers to hold the preform shape through initial processing. The tackifying agent helps maintain the preform configuration and is particularly useful for small or simple structures. For larger or more complex structures, additional techniques are often utilized to ensure stability over a wide surface area while allowing effective resin flow during resin infusion.

[0004]

[0004] Therefore, those skilled in the art continue to conduct research and development in the field of non-crimped fabric and composite preforms to enhance the stability of preforms, improve handling efficiency, and optimize resin injection technology, especially for larger or more complex structures. [Overview of the Initiative]

[0005]

[0005] A method for manufacturing a non-crimped fabric is disclosed.

[0006]

[0006] In one embodiment, the method of the present disclosure includes providing a plurality of layers of continuous fibers held together by stitch threads, and adding a binder between adjacent layers of the plurality of layers of continuous fibers and on the outer layer of the plurality of layers of continuous fibers. In this case, the binder has an activation temperature below the melting temperature of the stitch threads.

[0007]

[0007] Non-crimp fabrics are also disclosed.

[0008]

[0008] In one embodiment, the non-crimp fabric of the present disclosure includes a plurality of layers of continuous fibers held together by stitch threads, and a binder structure between adjacent layers of the plurality of layers of continuous fibers and on the outer layers of the plurality of layers of continuous fibers. In this case, the binder structure has an activation temperature below the melting temperature of the stitch threads.

[0009]

[0009] A method for manufacturing a composite material structure is also disclosed.

[0010]

[0010] In one embodiment, the method of the present disclosure provides one or more layers of non-crimped fabric, each layer of non-crimped fabric comprising a plurality of layers of continuous fibers held together by stitch threads, and comprising a binder structure between adjacent layers of the plurality of layers of continuous fibers and on the outer layer of the plurality of layers of continuous fibers, wherein the binder structure has an activation temperature below the melting temperature of the stitch threads; arranging one or more layers of non-crimped fabric to produce a preform having a preform shape; and heating the preform to a temperature between the activation temperature of the binder structure and the melting temperature of the stitch threads, thereby activating the binder structure and maintaining the preform shape.

[0011]

[0011] The preform is also disclosed.

[0012]

[0012] In one embodiment, the preform of the present disclosure comprises one or more layers of a non-crimped fabric, each layer of the non-crimped fabric comprising a plurality of layers of continuous fibers held together by stitch threads, and the one or more layers of the non-crimped fabric are arranged to form the shape of the preform, and a binder structure that maintains the shape of the preform, comprising a binder material, and located between adjacent layers of the plurality of layers of continuous fibers and on the outer layers of the plurality of layers of continuous fibers, and having an activation temperature below the melting temperature of the stitch threads. In this case, the stitching in the non-crimped fabric defines the gap spaces between the plurality of layers of continuous fibers that are not bound by the binder material, providing pathways for resin impregnation.

[0013]

[0013] Several other examples of the non-crimp fabrics, preforms, and methods of manufacture of the present disclosure will become apparent from the following detailed description, accompanying drawings, and accompanying claims. [Brief explanation of the drawing]

[0014] [Figure 1]

[0014] This is a schematic diagram of an embodiment of a multilayer non-crimped fabric structure exhibiting a bidirectional configuration having a first layer of continuous fibers oriented in one direction and a second layer oriented in a second direction. The diagram also shows stitch threads that secure the inner layer of continuous fibers and binder structures positioned between adjacent fiber layers and on the outer layer of the non-crimped fabric stack. The diagram further includes optional interlayer reinforcing bale positioned between the layers of continuous fibers to improve impact resistance and durability in the composite structure. [Figure 2]

[0015] This flowchart shows a method for producing a non-crimped fabric according to this description. The method includes the steps of providing a plurality of continuous fiber layers, adding stitch threads to ensure fiber alignment, and adding a binder structure to stabilize the structure of the non-crimped fabric. [Figure 3]

[0016] The lamination is shown as layers of non-crimped fabric are unwound and guided onto a lamination spool to which binder bale is added to both sides. The structure is then heated in an oven to activate the binder and stabilize the non-crimped fabric without affecting the stitch threads. [Figure 4]

[0017] This describes a powder spraying method for adding a binder. The binder powder is sprayed onto the non-crimped fabric as it passes under the nozzle, and is then heated to activate the binder, fixing it to the non-crimped fabric while maintaining stitching integrity. [Figure 5]

[0018] This flowchart shows the method for manufacturing a composite structure using non-crimped fabric according to this description. [Figure 6]

[0019] This is a cross-sectional view of a preform structure consisting of multiple layers of non-crimped fabric placed within a mold. [Modes for carrying out the invention]

[0015]

[0020] This description relates to a non-crimped fabric containing multiple layers of continuous fibers held together by stitch threads. This structure includes a binder that is added between adjacent layers of continuous fibers to form a binder structure. The binder is also added to the outermost layer of the multiple layers of continuous fibers. The binder helps maintain the shape of the fabric during handling of the preform by fixing the relative arrangement of the fiber layers or the relative arrangement of the non-crimped fabric within the preform. The activation temperature of this binder is set below the melting temperature of the stitching material, allowing the binder to be activated without affecting the stitch threads. This temperature relationship ensures that the stitch threads do not melt and therefore maintain open channels for resin impregnation. The combined use of stitch threads and binder in a non-crimped fabric supports both mechanical performance and efficient processing, making it possible to apply the material to the manufacture of useful composites with precise fiber alignment and effective resin flow.

[0016]

[0021] In some embodiments, the non-crimped fabric comprises three or more layers of continuous fibers, and a binder structure is placed between each individual layer within the multiple layered structure. Placing the binder between all layers promotes the stability and alignment of the fabric after heating the preform and maintains the intended arrangement of each fiber layer within the preform structure until resin impregnation.

[0017]

[0022] Non-crimped fabrics are structural materials containing continuous layers of fibers aligned without interlacing, resulting in a crimp-free structure. This configuration contrasts with woven fabrics, where fiber interlacing produces crimp, which can affect mechanical properties. The crimp-free alignment of non-crimped fabrics facilitates load transfer along each fiber, improving strength, stiffness, and overall mechanical properties. Non-crimped fabrics are well-suited for composite applications requiring high impact resistance, fatigue resistance, and tensile strength. Furthermore, the open structure facilitates efficient resin flow during composite manufacturing, making these fabrics advantageous for industries such as aerospace, automotive, and wind energy. These industries desire both lightweight materials and reliable structural performance.

[0018]

[0023] Non-crimped fabrics may contain multiple layers of continuous fibers, each layer featuring a specific fiber orientation that contributes to the fabric's mechanical properties. Orientations include unidirectional, bidirectional, and multiaxial configurations, each performing a different structural function. In a unidirectional configuration, all fibers within a layer are aligned parallel to a single direction, optimizing the fabric for high tensile strength along its axis. This configuration is particularly effective for applications experiencing unidirectionally concentrated loads, such as structural beams or reinforcements. In a bidirectional configuration, fibers are oriented at two different angles within the layer (e.g., 0° and 90°), allowing the fabric to withstand loads from two different directions. Multiaxial orientations include fibers aligned at multiple angles, such as 0°, 90°, and ±45°, creating a more versatile fabric structure capable of accommodating complex loads from various directions. This alignment distributes forces more uniformly, increasing the resistance of structures created from such fabrics to shear and torsional stresses. Multiaxial configurations can be used in state-of-the-art composites for applications such as wind turbine blades, automotive components, and aerospace structures. In these applications, multidirectional strength and durability are crucial. Non-crimped fabrics can be further customized by continuously laminating different orientations and / or weights per ply area. By adjusting the number and orientation of layers, properties such as impact resistance and fatigue durability can be influenced.

[0019]

[0024] Non-crimped fabrics can be constructed from a variety of fiber types, each selected based on desired properties such as strength, stiffness, heat resistance, or chemical compatibility. Fiber types include carbon fibers, known for their strength-to-weight ratio and thermal stability, providing cost-effective reinforcement with good tensile strength and moderate weight. Aramid fibers are also included, valued for their impact resistance and energy absorption properties. Hybrid fabrics can also be employed, combining different fiber types within the same layer or across multiple layers to achieve a balance of properties, such as combining raw fibers for stiffness with glass fibers to improve flexibility and elasticity. The choice of fiber composition allows non-crimped fabrics to be designed for specific applications, balancing performance requirements with cost and weight considerations.

[0020]

[0025] In non-crimped fabrics, stitch threads are used to secure multiple layers of continuous fibers together without causing fiber displacement, thus maintaining the structural integrity of the fabric. The stitch threads not only hold the layers in place but also allow for relative movement between fibers. This feature is advantageous during molding, as it allows non-crimped fabrics to be positioned in preforms with specific shapes. The freedom of fiber movement minimizes the strain imposed on the fabric during molding, reducing the possibility of fiber breakage or displacement, and ensuring that the final preform maintains the desired fiber orientation. By maintaining flexibility, the stitch threads support both strength and adaptability, making non-crimped fabrics well-suited for complex composite applications.

[0021]

[0026] The stitching threads within the non-crimp fabric are selected to have a melting temperature above the activation temperature of the binder in order to maintain stability without melting during the activation of the binder. Generally, the melting temperature of the stitching material ranges from 120°C to 400°C or higher, depending on specific performance requirements. The range of 150°C to 300°C can be used for many applications, but for higher heat demands, a range of 300°C to 400°C or higher can be adopted. By selecting a stitching material with a melting temperature within these ranges, the stitching threads firmly hold the fiber layers throughout the process and reduce the risk of fiber displacement or structural damage. Furthermore, by avoiding melting during the activation of the binder, the stitching threads maintain open gaps and enable faster resin injection in subsequent stages.

[0022]

[0027] The stitching material within the non-crimp fabric is selected to provide stability, heat resistance, and compatibility with the composite structure. Suitable stitching materials include high-melting-point polyesters, polyamides, and aramid fibers to ensure stability during binder activation. High-melting-point polyesters have a melting temperature above 250°C and provide thermal stability and durability. Polyamides with melting points in the range of 190 - 350°C provide flexibility and elasticity during processing depending on the type of polyamide and its chemistry, while aramid fibers with melting points above 400°C provide improved heat resistance for applications requiring high-temperature resistance. By selecting a stitching material within these melting temperature ranges, the following is ensured. That is, the stitching maintains structural integrity, firmly holds multiple fiber layers, and clearly maintains a thickness-through path for resin flow during subsequent composite processing.

[0023]

[0028] Stitching within the non-crimp fabric can be performed using a fiber machine designed to attach the fiber layers without disturbing the alignment of the plurality of fiber layers. This process involves laying each fiber layer according to a desired orientation and then stitching them together in a continuous thread path that avoids introducing tension or distortion. Automated stitching devices, which are often equipped with computer-aided design (CAD) control, enable precise stitching placement and accommodate different stitch types and patterns. Various stitching patterns are used within the non-crimp fabric to achieve specific mechanical properties and facilitate resin infusion during composite processing. Common patterns include tricot, which provides lightweight support and flexibility, and chain stitching, which enhances robustness for applications requiring improved durability. In some cases, lock stitching is also employed for its strength and stability in high-stress applications. The choice of stitching pattern can affect the flexibility of the fabric and the flow of the resin, as certain patterns create small through-thickness channels that aid in uniform resin distribution.

[0024]

[0029] The binder structure within the non-crimp fabric is incorporated to maintain the shape of the preform after the non-crimp fabric has been placed in its intended configuration. The binder structure can be any permeable configuration of binder material placed between adjacent layers of continuous fibers and / or on the outermost layer of the non-crimp fabric. This structure activates at a temperature below the melting point of the stitching material, joining the fiber layers to maintain the shape and stability of the preform while allowing an open path for resin impregnation. This can be added in various forms, such as powder, non-woven veil, or hybrid configurations, providing bonding and, in some cases, additional strengthening functions.

[0025]

[0030] This binder structure remains inert during molding, allowing continuous fiber layers within the non-crimped fabric to move relative to one another. This minimizes distortion during molding and reduces the possibility of fiber misalignment or breakage. Once the preform shape is determined, the binder is activated by heating to a specific temperature, bonding the structure and fixing the preform shape in place. The binder structure (1) is positioned between adjacent layers of continuous fibers to form internal bonds that restrict movement between each fiber layer after activation, helping to maintain alignment and stability, and (2) is positioned on one or both of the outer layers of the fiber layer stacks to help fix the preform by restricting movement between the non-crimped fabric and any adjacent material (such as another layer of the non-crimped fabric) once activated. By controlling both the placement and activation of the binder structure, the preform achieves stability while avoiding unnecessary distortion during molding and supports the alignment and preparation of the fabric for subsequent composite manufacturing steps such as resin injection and curing.

[0026]

[0031] The activation temperature of the binder structure is the temperature at which the binder material softens or melts to form a bond between adjacent fiber layers, and once set, it fixes the preform shape. This activation temperature is selected to be below the melting temperature of the stitching material, ensuring that the binder is activated without affecting the stitch threads. Typical activation temperatures for binder materials range widely from 70°C to 180°C, depending on the intended bonding requirements. This selective activation stabilizes the preform structure while maintaining open through-thickness channels for resin injection during composite processing.

[0027]

[0032] The binder structure within a non-crimped fabric can be added in powder form. This allows for a uniform distribution and precise control of the coating between continuous fiber layers. Placed between adjacent fiber layers or on the outer layers, this powder binder activates when heated to a specific activation temperature, bonding multiple layers and maintaining the shape of the preform. The powder form provides flexibility in the addition process, ensuring uniform bonding across complex or uneven preforms, and allowing the binder to be tailored to the specific bonding needs of the composite structure.

[0028]

[0033] The composition of the powder binder is formulated to exhibit little to no tack (adhesion) at room temperature, allowing for easy handling and placement of non-crimp fabric layers without prematurely bonding adjacent fiber layers to each other. This low tack ensures that the layers remain freely adjustable during assembly, allowing for precise alignment until the preform shape is finalized. Suitable powder binder compositions include, but are not limited to, thermosetting materials such as epoxy, bismaleimide, polyester, acrylic, and vinyl esters, as well as thermoplastic materials such as riamide, polyester, polysulfone, polyetherketone, polyurethane, and polyimide. In some embodiments, it is preferable that the binder reacts with the matrix resin injected into the preform, thereby chemically incorporating it into the polymer backbone of the matrix resin. Upon reaching its activation temperature, the powder binder softens or melts, fixing the fiber layers in place while maintaining an open path for efficient resin injection during subsequent composite processing.

[0029]

[0034] The binder structure can also be implemented as a nonwoven bale, a thin, flexible sheet, placed between fiber layers and optionally on the outer layer of the fabric stack. When heated to its activation temperature, the nonwoven bale bonds the fabric layers in place to maintain the preform shape. This bale structure allows for uniform bonding coverage across the fabric, conforming to complex contours and ensuring uniform adhesion. Furthermore, the open structure of the nonwoven bale supports resin permeability, making it suitable for composite applications requiring both stable bonding and resin flow.

[0030]

[0035] The binder structure of the nonwoven bale consists of thermoplastic fibers that are activated at a specific temperature to form bonds between the fiber layers without interfering with the flow of the resin. Suitable materials for nonwoven bale include polyamide, polyimide, polyamide-imide, polyester, polybutadiene, polyurethane, polypropylene, polyetherimide, polysulfone, polyethersulfone, polyphenylene sulfide, polyetherketone, polyetherketone, polyarylamide, polyketone, polyphthalamide, polyphenylene ether, polybutylene terephthalate, polyethylene terephthalate, and polyester polyarylate (e.g., VECTRAN®). The open structure of these bale ensures that the resin can effectively permeate through the bonded layers, making these compositions suitable for applications requiring both stable bonding and efficient resin injection during composite material manufacturing.

[0031]

[0036] Interlaminar reinforcing bale can also be placed between adjacent layers of continuous fibers within a non-crimped fabric to improve impact resistance and toughness. The interlaminar reinforcing bale can be placed together with the binder structure of the nonwoven bale in the same interlaminar space. When placed together with the binder structure of the nonwoven bale in the same interlaminar space, the two bale can work together to provide both bonding and reinforcing functions within a single layer. Alternatively, by placing the interlaminar reinforcing bale separately, independent reinforcement is possible, allowing for independent reinforcement functions where additional impact resistance is required without affecting the main bonding locations of the binder structure. This arrangement provides flexibility in design, allowing for precise control over the composite structure and impact properties while maintaining open paths for resin flow during processing.

[0032]

[0037] The interlaminar reinforcing veil is selected to have a melting temperature above the activation temperature of any binder, ensuring stability during binder activation. This stabilization allows the interlaminar reinforcing veil to provide structural reinforcement without impairing the bonding function of the binder structure. The melting temperature of the interlaminar reinforcing veil is generally in the range of 120°C to 300°C, depending on the specific thermal and mechanical requirements of the composite material. For applications requiring moderate heat resistance, a melting temperature range of 150°C to 250°C may be used, while for higher thermal requirements, materials with a melting temperature above 250°C may be preferable. By selecting an appropriate melting temperature for the interlaminar reinforcing veil, it can effectively perform its reinforcing function without interfering with the activation of the binder.

[0033]

[0038] Interlaminar reinforcement veils consist of fibers or materials specifically selected to improve the toughness and durability of the composite. Suitable materials include polyamides, polyimides, polyamide-imides, polyesters, polybutadienes, polyurethanes, polypropylenes, polyetherimides, polysulfones, polyethersulfones, polyphenylsulfones, polyetherketones, polyarylamides, polyketones, polyphenylene ethers, polybutylene terephthalate, polyethylene terephthalate, polyester polyarylate (e.g., VECTRAN®), polyaramids (e.g., KEVLAR®), polybenzoxazoles (e.g., ZYLON®), viscose (e.g., RAYON®), carbon fibers, and glass fibers.

[0034]

[0039] Hybrid bale can be incorporated to provide both bonding and reinforcement within a non-crimped fabric. This hybrid bale includes a combination of low-melting-point and high-melting-point components, each playing a specific role. The low-melting-point component acts as a binder, with an activation temperature below the melting point of the stitching material, allowing adjacent fiber layers to bond without affecting the stitch threads. The high-melting-point component acts as an interlayer reinforcing bale, with a melting temperature above the binder's activation range to maintain stability during bonding, improving impact resistance and durability. Hybrid bale can be constructed by alternating or blending low-melting-point and high-melting-point fibers within a single nonwoven structure, or by laminating separate sheets of each material to form a multifunctional bale. For example, a hybrid bale could incorporate low-melting-point polyester fibers (activation range 100°C to 140°C) as the binder component and aramid fibers (melting above 400°C) as the reinforcing component. Low-melting-point polyester fibers are activated when heated to bond the layers, while aramid fibers remain intact and provide structural reinforcement. Similarly, two-component bales can be produced by combining two different polyamide variants, for example, a low-melting-point copolyamide containing one part and a different high-melting-point polyamide or copolyamide containing the other part, as described above. By combining these components, hybrid bales enable integrated bonding and reinforcement within a single layer, optimizing both structural integrity and impact resistance within the composite. Hybrid bales can be placed between adjacent fiber layers or on the outer surface of the fabric stack, providing flexibility in composite design and improving the performance of non-crimped fabrics in demanding applications.

[0035]

[0040] Figure 1 shows an embodiment of the multilayer non-crimped fabric structure described herein. In this embodiment, the non-crimped fabric structure includes a first layer (10) of continuous fibers aligned in parallel and a second layer (20) of continuous fibers also aligned in parallel. In particular, the fibers in the first layer are arranged perpendicular to the fibers in the second layer, providing a bidirectional configuration. However, those skilled in the art will understand that further layers may be added, and other orientations of fiber alignment (e.g., unidirectional or multiaxial configurations) may be implemented to achieve specific mechanical properties tailored to the application. The stitch threads (30) shown in Figure 1 are provided to fasten multiple layers together, and the arrangement of threads shown here is for illustrative purposes only. Depending on the number of layers, the specific fiber orientation, and the type of fiber used, various stitching patterns may be employed. Such variations will be well understood by those skilled in the art, who can select an appropriate stitching pattern based on the intended performance requirements of the composite structure.

[0036]

[0041] A typical binder structure (40) is shown in Figure 1, positioned between the first and second layers of continuous fibers, and is represented as a binder bale layer. This binder structure helps maintain the structural integrity of the non-crimped fabric structure by stabilizing the relative arrangement of the fiber layers during preform handling and subsequent processing stages. Although the binder structure is illustrated as a bale, it should be understood that a powder binder structure may also be used as an alternative, depending on the processing requirements and desired properties. The binder structure (40) can also be positioned on the outermost layer of continuous fibers to improve stability during handling and processing. The binder has an activation temperature lower than the melting temperature of the stitch threads, allowing it to activate and permanently bond the layers without compromising the integrity of the stitch threads.

[0037]

[0042] In addition, Figure 1 may also include an optional interlaminar reinforcing veil (50) positioned between continuous fiber layers. This reinforcing veil is designed to improve the impact resistance and durability of the composite by providing further reinforcement between the fiber layers. While the interlaminar reinforcing veil (50) is illustrated here, it should be understood that this veil may also be included in other configurations of the non-crimp fabric if improved toughness is desired. Furthermore, Figure 1 may incorporate a hybrid veil that provides both bonding and reinforcing functions. Such a hybrid veil may include a low-melting-point component that acts as a binder and a high-melting-point component that acts as an interlaminar reinforcing veil. This dual-function veil may be positioned between adjacent fiber layers or on the outer surface of the fiber stack, providing design flexibility and improving the performance of the non-crimp fabric in demanding applications.

[0038]

[0043] Figure 2 provides a flowchart illustrating method 100 for the manufacture of a non-crimp fabric according to this description, consistent with the steps of claim 1. Step 110 begins by providing multiple layers of continuous fibers. The continuous fibers within each layer may be aligned without interlacing to maintain a crimp-free structure and optimize load transfer characteristics. The multiple layers are stitched together to fix them while maintaining their orientation using a stitching material having a melting point above the activation temperature of the binder. Step 120 includes adding a binder structure between adjacent layers of continuous fibers or on the outer layer of the fiber stack of the layers of continuous fibers. The binder structure may be added either before or after the stitch threads, in powder form, as a nonwoven bale, or as a hybrid bale having low-melting-point and high-melting-point components. Its activation temperature is set below the melting temperature of the stitch threads, allowing activation without compromising the integrity of the stitch threads. This binder structure stabilizes the preform while maintaining flexibility for molding, further details of which are provided below.

[0039]

[0044] One approach is that non-crimp fabrics can be manufactured using any standard method known in the art. Typically, non-crimp fabrics are constructed by arranging multiple layers of continuous fibers in a specific orientation to achieve a crimp-free structure. These continuous fibers can be aligned in a unidirectional, bidirectional, or multiaxial configuration, depending on the desired mechanical properties of the final composite. Each layer is aligned in parallel without interlacing to avoid crimping and to maximize load transfer along the fibers. Once the fiber layers are aligned, they are secured via stitch threads. Depending on the number of layers, fiber orientation, and the type of fiber used, various stitch patterns such as tricot, chain stitch, or lock stitch may be employed. The stitching is performed in a manner that minimizes fiber displacement, thus maintaining the structural integrity of the fabric and supporting flexibility for molding into a preform. The stitching material is typically selected for its high melting point so that it remains stable during the activation of any subsequent binder. After stitching, the non-crimped fabric structure is ready for further processing or the addition of a binder structure.

[0040]

[0045] In certain embodiments, the binder structure is added on the outermost layer of a previously manufactured non-crimped fabric. The binder structure may be positioned on one or both sides of the non-crimped fabric to improve the stability of the preform during preform handling and subsequent composite processing. The binder structure may be added using a variety of exemplary methods. In one approach, a powdered binder is sprayed onto one or more outer surfaces of the non-crimped fabric to allow for controlled distribution across the fabric. Alternatively, a nonwoven binder bale may be laminated onto one or both outer surfaces of the non-crimped fabric. This lamination method provides uniform coverage and increased bonding strength. These may be advantageous for applications requiring improved stability. After the binder structure is added, a heat treatment is performed to permanently bond the binder structure to the outer layer of the non-crimped fabric. During this step, the non-crimped fabric is heated to a temperature above the activation temperature of the binder, but below the melting temperature of the stitch threads and any optional interlayer reinforcing veil. This selective heating ensures that the binder is activated and bonded to the fiber layers without compromising the integrity of the stitch threads or other structural components. By performing this heat treatment, the binder structure is effectively bonded to the (one or more) outer layers of the non-crimped fabric, increasing the stability of the fabric and fixing the preform shape.

[0041]

[0046] Figures 3 and 4 illustrate two different methods for adding binder to each layer of non-crimped fabric before stitching, ensuring the binder remains inert for flexibility during preformation. In one approach, fibers are taken from a spool, spread in a band, cut to length, and then held in place (generally by clamps) at both ends of the band in the machine bed. This process is repeated for each layer, except for continuous 0-degree fibers along the length of the machine bed. Figure 3 shows the lamination of the fabric. In this case, the binder, in the form of a nonwoven bale, is added to the top and / or bottom of each individual layer of continuous fibers when placed on the machine bed, rather than after the complete layer has been unwound. Each fiber layer with binder is then lightly heated to fix the binder to its single layer without fully activating it. This low level of heat treatment simply attaches the binder to each fiber layer for handling and stitching, preventing premature bonding that could limit drape. Once all layers are positioned with the binder and lightly bonded, they are stitched together by stitch threads (30). The stitch threads (30) maintain alignment without restricting interlayer movement. After stitching, the non-crimped fabric with the inert binder is wound onto an output spool (90) for transport. In a subsequent processing step, after the non-crimped fabric has been formed into a preform, controlled heating is applied to activate the binder and stabilize the preform shape.

[0042]

[0047] Figure 4 illustrates an alternative approach using a powder spraying method to apply a binder to each individual layer of continuous fibers before stitching. Here, each layer in the non-crimped fabric is unwound from an input spool (60) and transported under a spray nozzle (92). The spray nozzle (92) disperses the powder binder onto one side of each layer. By applying the binder to only one side, the potential challenges associated with coating both sides are avoided. Once the layers are assembled, the binder becomes available between each ply, providing proper bonding during subsequent processing. After powder application, each layer passes through an oven (80). The oven (80) provides light heating sufficient to adhere the binder powder to the surface of the fibers without fully activating the binder powder. Similar to the lamination method, this heat treatment simply fixes the binder for lamination and stitching. In some configurations, the addition of the binder can be carried out continuously, but this can also be done by preparing a unidirectional fabric that is subsequently bound with binder and supplied to a warp-knitting machine to produce a non-crimp fabric. Once each layer is processed, the multiple layers are stacked and stitched together by stitch threads (30) to maintain the binder arrangement between each layer while allowing flexibility. The finished non-crimp fabric structure with inert binder is then wound onto an output spool (90) for transport. Later, after the non-crimp fabric has been formed into a preform, the binder is activated via controlled heating to fix the preform shape.

[0043]

[0048] Another approach to manufacturing non-crimp fabrics may involve modifying the process to incorporate a binder structure between selected substacks of continuous fiber layers during assembly. This keeps the binder inactive throughout this stage. While this integrated approach may provide internal bonding capabilities within the fabric structure and improve post-molding stability and fiber alignment, it may reduce the flexibility or drape of non-crimp fabrics essential for molding complex preforms. Conventional non-crimp fabric manufacturing machines are typically not designed to stitch individual layers using a binder structure between them, but instead may stitch two or more substacks together. However, stitching substacks with a binder between them can make the fabric too rigid in certain applications where high drape is required to conform to complex preform shapes. To produce non-crimp fabrics, continuous fibers such as carbon, glass, or aramid are selected based on the required mechanical properties of the final composite. These fibers are prepared in continuous lengths, aligned to avoid crimping, and support effective load transfer along the fibers. Each continuous layer of fibers is laid in a specific orientation, such as unidirectional, bidirectional, or multiaxial, according to the intended properties of the non-crimp fabric. Once each fiber layer is supplied onto the machine bed of the warp knitting machine, a binder structure may be introduced between adjacent substacks, either in powder form (uniformly distributed across each fiber layer) or as a nonwoven bale. The formation of continuous fiber layers and the insertion of binder structures are continued as needed to achieve the desired stack configuration. Various stitch patterns, such as chain stitch, lock stitch, or tricot, may be employed depending on the number of layers, fiber type, and orientation. The stitching material is selected for its high melting point to ensure stability during subsequent processing. The stitch threads fix the layers in place and maintain the alignment and flexibility of the fibers within the non-crimp fabric structure.After all layers and binder structures are in place and secured with stitching threads, the non-crimped fabric structure is prepared to be molded into the desired preform. At this stage, the binder structures remain inert, allowing the fabric to retain its flexibility and move relative to each other as needed for molding. By incorporating the binder structures at the ply level and keeping them inert, the non-crimped fabric achieves some internal stability while maintaining sufficient adaptability for molding; however, several applications requiring high drape may benefit from alternative configurations.

[0044]

[0049] This description also encompasses a method for manufacturing a composite structure. The method involves forming a preform using multiple layers of non-crimped fabric. The method leverages the structural advantages of non-crimped fabric, combining it with a binder structure that stabilizes the shape of the preform during processing to provide multiple layers of continuous, crimpless fibers held together by stitch threads. Several steps involved in manufacturing the composite structure are illustrated in the flowchart of Figure 5.

[0045]

[0050] Figure 5 shows a method (200) which is a process for manufacturing a composite structure using multiple layers of non-crimped fabric. The method begins with step (210) which includes providing one or more layers of non-crimped fabric. Each layer of non-crimped fabric includes multiple continuous fiber layers aligned in a non-crimped configuration, held together by stitch threads that maintain fiber alignment and structural integrity. Binder structures are also included, positioned between adjacent fiber layers or on the outermost layer. These binder structures have an activation temperature below the melting temperature of the stitch threads, allowing for selective activation without affecting the stitch threads.

[0046]

[0051] Following the preparation of multiple layers of non-crimped fabric, step (220) includes arranging the multiple layers into a preform shape suitable for composite processing. The stitch threads within the multiple layers of non-crimped fabric provide the flexibility necessary to form the multiple layers while maintaining fiber alignment and stability. This enables a precise preform design tailored to the intended structural requirements of the composite.

[0047]

[0052] In step (230), the preform is heated to a controlled temperature between the activation temperature of the binder structure and the melting temperature of the stitch threads. This selective heating activates the binder structure and bonds the multiple fiber layers together while maintaining the stitch threads. This maintains open gap channels for resin impregnation in subsequent steps. This controlled activation stabilizes the preform, allowing it to maintain its shape through subsequent processing.

[0048]

[0053] Following the activation of the binder structure, step (240) includes impregnating the preform with resin to complete the composite structure. Open gap channels maintained by stitch threads facilitate the flow of resin through the thickness, allowing for rapid and uniform impregnation throughout all fiber layers. Depending on the desired mechanical properties, thermal stability, and environmental resistance of the final composite, various types of resins may be used. Suitable resins include, but are not limited to, epoxy resins, polybenzoxazines, bismaleimides, polyimides, polyester resins, vinyl ester resins, mixtures of various suitable resin types (such as epoxy and benzoxazines), and phenolic resins. Epoxy resins are generally used for their high mechanical strength and chemical resistance, making them ideal for applications requiring durability under stress. Polyester resins provide cost-effective reinforcement with excellent tensile properties, while vinyl ester resins offer enhanced chemical and thermal resistance suitable for harsh environments. Phenolic resins can be selected for applications requiring high fire resistance and low smoke emission. The resin is added to the preform by injection, which can be achieved using vacuum-assisted resin transfer molding (VARTM), resin transfer molding (RTM), or other suitable impregnation techniques. During injection, the resin is drawn into the preform under controlled pressure, ensuring complete wet-out of fibers within each layer of the non-crimped fabric. Vacuum or pressure helps minimize voids in the composite structure, promoting consistency and mechanical reliability. Impregnation can be carried out at ambient temperature or high temperature, depending on the viscosity, reactivity, and flow characteristics of the resin. These should be optimized to achieve a complete and uniform resin distribution throughout the preform.

[0049]

[0054] Once the preform is completely impregnated with resin, step (250) includes curing the resin to harden the structure and finish the mechanical properties of the composite. Curing can be performed at ambient temperature or at a high temperature, depending on the resin system. For example, epoxy resins may require curing temperatures ranging from 80°C to 180°C, typically held for 30 minutes to 6 hours, depending on the specific formulation and thickness of the composite structure. High-temperature curing can be performed using an oven, autoclave, or heated press to ensure consistent heat distribution and complete polymerization of the resin. Some resins, such as room-temperature curing epoxy or polyester resins, can be cured at ambient conditions for extended periods. This may be advantageous for applications requiring lower energy input or for manufacturing larger parts. In such cases, curing agents or accelerators can be added to the resin to control the curing rate and optimize the properties of the final composite. In particular, curing under pressure in an autoclave or closed mold can improve the quality of the composite by reducing porosity, increasing fiber-to-resin contact, and improving mechanical properties. Complete curing solidifies the resin, firmly bonding the preform layers and fixing the fiber alignment initially established by the non-crimped fabric and stitching threads. This results in a one-piece, high-strength composite structure suitable for a variety of demanding applications requiring improved load-bearing capacity, durability, and environmental resistance. Thus, the method provides a robust approach to producing composites with controlled fiber alignment, resin impregnation, and curing, resulting in composite structures with optimal mechanical and structural performance.

[0050]

[0055] In another embodiment, this description relates to a preform structure used as an intermediate product in the manufacture of composite materials. Figure 6 shows an embodiment of this preform, which consists of one or more layers of non-crimped fabric arranged to form a stable, shape-retaining structure designed to facilitate efficient resin impregnation and composite processing.

[0051]

[0056] Each layer of non-crimped fabric within the preform structure may consist of multiple layers of continuous fibers. These layers are held together by stitch threads within the non-crimped fabric. This ensures fiber alignment and maintains a crimp-free structure. As shown in Figures 1 and 2, this internal structure of each non-crimped fabric maintains optimal load transfer characteristics and mechanical performance. In this case, the stitch threads fix each layer of continuous fibers without affecting the flexibility between layers. The preform (7) consists of multiple layers of non-crimped fabric represented by a first layer (1) and a second layer (2) placed in a mold (3) of a desired shape for composite processing, as shown in Figure 6.

[0052]

[0057] To stabilize and maintain the shape of the preform, a binder structure is incorporated within the non-crimped fabric. This binder structure may be placed between adjacent layers of continuous fibers within each non-crimped fabric, or on the outermost layer. The binder is activated at a temperature below the melting point of the stitching material, ensuring that the binder can fix the fiber layers in the desired shape without compromising the integrity of the stitching. Selective activation of the binder structure fixes the fiber layers within each layer of the non-crimped fabric into the preform shape and maintains stability through handling and resin impregnation.

[0053]

[0058] The preform contains void spaces between continuous fiber layers within each non-crimped fabric, and these void spaces are free of binder material. These open channels, penetrating the thickness, are crucial for resin flow during subsequent resin impregnation, enabling rapid and uniform resin dispersion through the fiber structure. This resin permeability minimizes voids and contributes to the creation of a strongly cohesive composite structure.

[0054]

[0059] In some configurations, the binder structure is added as a powder, allowing for controlled dispersion and coating between the fiber layers. This powder binder can be formulated at room temperature with little to no tack, facilitating easy handling and precise placement of each non-crimped fabric layer during preform assembly. When heated, the powder binder softens or melts, permanently bonding the fiber layers and stabilizing the preform.

[0055]

[0060] Alternatively, the binder structure can be implemented as a thin, flexible sheet that can be placed between multiple layers of continuous fibers within each layer of the non-crimped fabric, or on the outer surface of the stack of non-crimped fabric. This non-woven bale provides uniform bonding across the fabric surface, conforms to the complex contours within the preform, maintains open channels for resin flow through the thickness, and allows for efficient impregnation in subsequent stages.

[0056]

[0061] For applications requiring additional impact resistance and toughness, interlaminar reinforcing bale can be incorporated into the preform, positioned between individual layers of continuous fibers within each non-crimped fabric layer, or between adjacent non-crimped fabric layers. This reinforcing bale has a melting temperature above the binder activation temperature, ensuring stability during binder activation. Its inclusion reinforces the preform structure, improving the durability and impact resistance of the final composite.

[0057]

[0062] In certain configurations, the binder structure can be a hybrid veil containing both low-melting-point and high-melting-point components. The low-melting-point components are activated at lower temperatures to bond the fiber layers within each layer of the non-crimped fabric, while the high-melting-point components act as an interlaminar reinforcing veil, providing additional strength and resilience. This dual-function hybrid veil allows the preform to effectively maintain its shape while providing enhanced toughness, meeting the requirements of high-performance composite applications.

[0058]

[0063] The described preform structure integrates the advantages of non-crimped fabrics with a selectively activatable binder structure to produce a morphologically stable, resin-permeable intermediate. This design allows the preform to be customized for specific applications by incorporating powder binders, nonwoven bales, or hybrid reinforcing layers. By maintaining open resin flow channels and improving structural stability, this preform structure supports efficient composite processing, making it suitable for applications in aerospace, automotive, wind energy, and other industries where high structural integrity and processing efficiency are desired.

[0059]

[0064] In summary, the described non-crimped fabric and preform configurations present an innovative approach to achieving precise fiber alignment, enhanced structural stability, and efficient resin impregnation for composite material manufacturing. Each layer of the non-crimped fabric contains multiple layers of continuous fibers held together by stitch threads, maintaining a crimp-free structure that optimizes load transfer and mechanical integrity. This layered structure allows for various fiber orientations, including unidirectional, bidirectional, and multiaxial configurations. These orientations can be customized to improve strength, stiffness, impact resistance, and fatigue durability to suit specific application requirements.

[0060]

[0065] A selectively activated binder structure, positioned between continuous fiber layers or on the outermost surface of a non-crimped fabric, offers advantages in stabilizing the shape of the preform during molding, handling, and processing. The activation temperature of the binder structure is adjusted to be below the melting point of the stitching material, allowing the preform shape to be fixed in place without compromising open channels for resin flow. This ensures that the integrity of the stitch threads and the alignment of the fiber layers are maintained throughout the processing.

[0061]

[0066] Various embodiments of binder structures, including powder binders, nonwoven bales, and hybrid bales, enable adaptable preform configurations. Each embodiment supports open void spaces between fiber layers for effective resin impregnation and bonding during composite material manufacturing. In addition, interlayer-reinforced bales or hybrid bales having both low-melting-point and high-melting-point components improve impact resistance and durability, enabling these preforms to meet the demanding application requirements in industries such as aerospace, automotive, and renewable energy.

[0062]

[0067] The method of the present disclosure for manufacturing composite structures further optimizes the impregnation and curing of preforms. By controlling the activation of the binder structure and ensuring the availability of resin channels that penetrate the open thickness, the method achieves rapid and uniform resin dispersion across all fiber layers. Subsequent resin curing can be performed at ambient temperature or high temperature to complete the mechanical properties of the composite and produce a high-strength, cohesive structure. In this case, the void content is reduced and the load-bearing capacity is improved.

[0063]

[0068] In certain embodiments, the binder structure is formulated to chemically react with the resin used to impregnate the preform. During curing, the binder structure interacts with the resin and is chemically incorporated into the matrix resin. This reactive bonding further enhances the cohesion between the fiber layers, creating an integrated composite structure with improved mechanical integrity. By forming covalent bonds with the matrix resin, the binder contributes to the overall stability and durability of the final composite. This reactive bonding allows for more seamless integration between the binder and the resin, reducing the possibility of delamination within the composite structure and improving load transfer across the fiber layers.

[0064]

[0069] The non-crimped fabric preforms and composite manufacturing methods described represent a robust solution for the production of high-performance composites. By utilizing a combination of precise fiber alignment, customizable binder structures, and efficient resin flow paths, multiple embodiments of this disclosure enable composite structures with optimized mechanical and thermal properties. This versatility makes the inventions of this disclosure suitable for a wide range of applications where structural integrity, impact resistance, and processing efficiency are desired.

[0065]

[0070] While various embodiments of the non-crimped fabrics, preforms formed therefrom, and methods for manufacturing composite structures of the present disclosure have been illustrated and described, it will be understood by those skilled in the art that multiple modifications can be made without departing from the scope and intent of the present invention. This application includes such modifications and is limited only by the claims.

Claims

1. A method for manufacturing a non-crimped fabric (1), To provide multiple layers (10, 20) of continuous fibers held together by stitch threads (30), and A method comprising adding a binder between adjacent layers of the plurality of continuous fiber layers (10, 20) and on the outer layer of the plurality of continuous fiber layers (10, 20), wherein the binder has an activation temperature below the melting temperature of the stitch thread.

2. The method according to claim 1, wherein the binder is added in front of the stitch thread (30).

3. The method according to claim 2, wherein the binder is added to the outer layer of the plurality of continuous fiber layers (10, 20) after the stitch thread (30) has been added.

4. The method according to claim 1, wherein the binder is in the form of a powder.

5. The method according to claim 4, wherein the powder has little to no tack at room temperature.

6. The method according to claim 1, wherein the binder is in the form of a nonwoven bale.

7. The method according to claim 1, wherein an interlayer reinforcing veil (50) is provided between adjacent layers of the plurality of continuous fiber layers (10, 20), and the interlayer reinforcing veil has a melting temperature exceeding the activation temperature of the binder.

8. The method according to claim 1, wherein adding the binder includes adding a veil having a low-melting-point component and a high-melting-point component, the low-melting-point component of the veil acts as the binder and the high-melting-point component acts as an interlayer strengthening veil.

9. Non-crimped fabric (1), Multiple layers (10, 20) of continuous fibers held together by stitch threads (30), and A non-crimp fabric comprising a binder structure (40) between adjacent layers of the plurality of continuous fiber layers and on the outer layer of the plurality of continuous fiber layers, wherein the binder structure (40) has an activation temperature below the melting temperature of the stitch threads.

10. The non-crimp fabric according to claim 9, wherein the binder structure (40) is in the form of a powder.

11. The powder is a non-crimp fabric according to claim 10, having little to no tackiness at room temperature.

12. The non-crimp fabric according to claim 9, wherein the binder structure (40) is in the form of a nonwoven bale.

13. The non-crimp fabric according to claim 9, further comprising interlayer reinforcing veils (50) between adjacent layers of the plurality of continuous fiber layers, wherein the interlayer reinforcing veils have a melting temperature exceeding the activation temperature of the binder structure.

14. The non-crimp fabric according to claim 9, wherein the binder structure (40) comprises a low-melting-point component and a high-melting-point component, the low-melting-point component of the binder structure acts as the binder, and the high-melting-point component acts as an interlayer reinforcing veil.

15. A method for manufacturing a composite material structure, To provide one or more layers (1, 2) of a non-crimped fabric, each layer of the non-crimped fabric comprising a plurality of layers (10, 20) of continuous fibers held together by stitch threads (30), and comprising a binder structure (40) between adjacent layers of the plurality of continuous fibers and on the outer layer of the plurality of continuous fibers, wherein the binder structure (40) has an activation temperature lower than the melting temperature of the stitch threads, To generate a preform (7) having a preform shape, one or more layers of the non-crimped fabric are arranged, and A method comprising heating the preform to a temperature between the activation temperature of the binder structure (40) and the melting temperature of the stitch threads (30), thereby activating the binder structure (40) and maintaining the shape of the preform.

16. The method according to claim 15, wherein the binder structure (40) is in the form of a powder.

17. The method according to claim 16, wherein the powder has little to no tack at room temperature.

18. The method according to claim 15, wherein the binder structure (40) is in the form of a nonwoven bale.

19. The method according to claim 15, wherein an interlayer reinforcing veil (50) is placed between adjacent layers of the plurality of continuous fiber layers (10, 20), and the interlayer reinforcing veil has a melting temperature that exceeds the activation temperature of the binder structure (40).

20. The method according to claim 15, wherein the binder structure (40) comprises a low-melting-point component and a high-melting-point component, the low-melting-point component acting as the binder and the high-melting-point component acting as an interlayer strengthening veil.

21. The method according to claim 15, further comprising impregnating the preform (7) with a resin.

22. The method according to claim 21, further comprising curing the resin.

23. The method according to claim 22, wherein the binder structure reacts with the resin while the resin is curing.

24. It is a preform, One or more layers (1, 2) of non-crimped fabric, each layer of non-crimped fabric comprising multiple layers (10, 20) of continuous fibers held together by stitch threads (30), and the one or more layers of non-crimped fabric are arranged to form the shape of the preform (7), A binder structure (40) that maintains the shape of the preform, comprising a binder material and having an activation temperature below the melting temperature of the stitch threads (30), between adjacent layers of the plurality of continuous fiber layers and on the outer layer of the plurality of continuous fiber layers, The non-crimped fabric (1, 2) is a preform that defines the gap spaces between the multiple layers (10, 20) of continuous fibers that lack the binder material, providing pathways for resin impregnation.

25. The preform according to claim 24, wherein the binder structure (40) is in the form of a powder.

26. The powder is a preform according to claim 25, wherein the powder has little or no tack at room temperature.

27. The preform according to claim 24, wherein the binder structure (40) is in the form of a nonwoven bale.

28. The preform according to claim 24, further comprising interlayer reinforcing veils (50) between adjacent layers of the plurality of continuous fiber layers (10, 20), wherein the interlayer reinforcing veils (50) have a melting temperature exceeding the activation temperature of the binder structure (40).

29. The preform according to claim 24, wherein the binder structure (40) comprises a low-melting-point component and a high-melting-point component, the low-melting-point component acting as the binder and the high-melting-point component acting as an interlayer strengthening veil.

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