Shapeable fabric

Abstract

Described herein is a formable fabric comprising: a first fiber oriented in a first direction; a second fiber oriented in a second direction; and a stitch knitting system comprising an impregnating component and a forming component, the impregnating component and the forming component of the stitch knitting system forming a stitch knitting pattern through the fabric wherein the first fibers comprise glass fibers and / or carbon fibers, the second fibers comprise glass fibers and / or carbon fibers, and the second direction is within 0 degree to 90 degrees of the first direction.

Description

Technical Field

[0001] The present invention relates to formable fabrics comprising glass fibres and / or carbon fibres, in particular formable fabrics for reinforcing structural components such as wind turbine components. Background Art

[0002] It is known to use glass fibers and / or carbon fibers to form reinforcing fabrics to reinforce structural components such as wind turbine blades or related components (eg spar caps).

[0003] Structural components including reinforcing fabric (reinforced structural components) are typically formed by stacking layers of reinforcing fabric in a mold, filling the mold with resin, and curing the resin to form the component. This method can be time consuming.

[0004] As the search for alternative energy sources continues, the use of wind energy and wind turbines has received increasing attention. As interest in harnessing wind energy to generate more energy has grown, technological advances in the field have allowed for increased sizes of wind turbine blades. Increasing the size of wind turbine blades has also increased the time required to produce wind turbine blades.

[0005] It would be desirable to provide improvements in enhancing the efficiency of the production of structural components, such as wind turbine blades. Summary of the invention

[0006] Most generally, the present invention provides a formable fabric comprising: first fibers oriented in a first direction; second fibers oriented in a second direction; and a stitching system including an impregnation component and a forming component, the impregnation component and the forming component of the stitching system forming a stitching pattern through the fabric.

[0007] For example, described herein is a formable fabric comprising:

[0008] first fibers oriented in a first direction;

[0009] second fibers oriented in a second direction; and

[0010] A stitch bonding system comprising an impregnation component and a forming component,

[0011] The impregnation component and the shaping component of the stitchbonding system form a stitch pattern through the fabric,

[0012] The first fibers include glass fibers and / or carbon fibers, the second fibers include glass fibers and / or carbon fibers, and the second direction is within 0 to 90 degrees of the first direction.

[0013] In a first aspect, the present invention provides a formable fabric comprising:

[0014] first fibers oriented in a first direction;

[0015] second fibers oriented in a second direction; and

[0016] A stitch bonding system comprising an impregnation component and a forming component,

[0017] The impregnation component and the shaping component of the stitchbonding system form a stitch pattern through the fabric,

[0018] wherein the first fibers include glass fibers and / or carbon fibers, the second fibers include glass fibers and / or carbon fibers, and the second direction is within 0 to 90 degrees of the first direction, and

[0019] wherein the impregnated component comprises about 15 weight % to about 75 weight % of the stitch bonding system, and the formed component comprises about 25 weight % to about 85 weight % of the stitch bonding system.

[0020] In a second aspect, the present invention provides a fabric laminate comprising at least two layers of a formable fabric as described herein.

[0021] In a third aspect, the present invention provides a shaped part comprising a fabric laminate as described herein.

[0022] In a fourth aspect, the present invention provides a method for producing a formable fabric, the method comprising:

[0023] Providing first fibers oriented in a first direction and second fibers oriented in a second direction, wherein the first fibers include glass fibers and / or carbon fibers, the second fibers include glass fibers and / or carbon fibers, and the second direction is within 0 to 90 degrees of the first direction;

[0024] The first fibers and the second fibers are stitched together using a stitching system comprising an impregnated component and a formed component, wherein the impregnated component comprises about 15 weight % to about 75 weight % of the stitching system and the formed component comprises about 25 weight % to about 85 weight % of the stitching system.

[0025] In a fifth aspect, the present invention provides a method for producing a shaped part, the method comprising:

[0026] stacking a plurality of formable fabric layers as described herein to provide a fabric layup;

[0027] shaping the fabric layup; and

[0028] The fabric laminate is heated at a temperature of up to about 150°C.

[0029] In one aspect, the present invention provides a roll of a formable fabric as described herein.

[0030] The present inventors have discovered that the formable fabrics described herein have excellent processability and provide improvements in the production efficiency of reinforced structural components such as wind turbine blades.

[0031] The present inventors have found that the present invention provides a formable fabric that provides improvements in the production efficiency of reinforced structural components (such as wind turbine blades and related components). This is because these formable fabrics can be stacked and shaped (i.e., pre-formed) before being incorporated into reinforced structural components. It has been found that the provision of formable fabrics as described herein surprisingly increases the speed at which reinforced structural components (e.g., wind turbine blades) can be produced. It has also been found that the formable fabrics as described herein exhibit excellent handleability, in particular the formable fabrics can be rolled, cut and stacked. Even more surprisingly, the present inventors have found that the formable fabrics as described herein can provide improvements in the production efficiency of reinforced structural components (e.g., wind turbine blades) without adversely affecting the impregnation or mechanical properties of the fabric or the final component.

[0032] The inventors have discovered that the formable fabrics described herein can be stacked to form fabric stacks, and the forming components of the stitching system allow the fabric layers of the fabric stack to adhere to each other to form a consolidated fabric stack that exhibits excellent adhesion. The inventors have also discovered that the formable fabrics, fabric stacks, and consolidated fabric stacks described herein can be directly formed, and once formed, the formed fabric or fabric stack retains the formed form (e.g., after being removed from the mold).

[0033] The present invention includes any combination of aspects and preferred features described herein except where such a combination is expressly impermissible or expressly avoided. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Embodiments and experiments illustrating the principles of the present invention will now be discussed with reference to the accompanying drawings, in which:

[0035] Figure 1 is a graph showing the effect of consolidation temperature on interlayer adhesion between fabric layups during formation of the fabric layup. DETAILED DESCRIPTION

[0036] Various aspects and embodiments of the present invention will now be discussed. Additional aspects and embodiments will be apparent to those skilled in the art.

[0037] A formable fabric is described herein, comprising: first fibers oriented in a first direction; second fibers oriented in a second direction; and a stitching system comprising an impregnation component and a forming component, the impregnation component and the forming component of the stitching system forming a stitching pattern through the fabric, wherein the first fibers comprise glass fibers and / or carbon fibers, the second fibers comprise glass fibers and / or carbon fibers, and the second direction is within 0 to 90 degrees of the first direction.

[0038] The first fibers of the formable fabric may be referred to as warp fibers. The first fibers may be arranged side by side and substantially parallel to each other. The second fibers of the formable fabric may be referred to as weft fibers. The second fibers may be arranged side by side and substantially parallel to each other.

[0039] In an embodiment, the formable fabric comprises first fibers oriented in a first direction and second fibers oriented in a second direction, wherein the second direction is within 0 to 90 degrees of the first direction, for example, within about 10 to about 90 degrees of the first direction, within about 20 to about 90 degrees of the first direction, within about 30 to about 90 degrees of the first direction, within about 40 to about 90 degrees of the first direction, within about 45 to about 90 degrees of the first direction, within about 60 to about 90 degrees of the first direction, within about 70 to about 90 degrees of the first direction, within about 80 to about 90 degrees of the first direction, within about 85 to about 90 degrees of the first direction, within about 88 to about 90 degrees of the first direction, or within about 90 degrees of the first direction.

[0040] In an embodiment, the formable fabric may be a unidirectional fabric or a multi-axial fabric, such as a bi-axial fabric.

[0041] In an embodiment, the formable fabric is a unidirectional fabric. The unidirectional fabric may include a second fiber oriented in a second direction, wherein the second direction is oriented in a direction greater than 0 degrees of the first direction. For example, the unidirectional fabric may include a first fiber oriented in a first direction and a second fiber oriented in a second direction, wherein the second direction is about 0 degrees to 90 degrees of the first direction, for example, within about 45 degrees to about 90 degrees of the first direction, within about 60 degrees to about 90 degrees of the first direction, within about 70 degrees to about 90 degrees of the first direction, within about 80 degrees to about 90 degrees of the first direction, within about 85 degrees to about 90 degrees of the first direction, within about 88 degrees to about 90 degrees of the first direction, or within about 90 degrees of the first direction. In the unidirectional fabric, the first fiber may account for more than about 90% by weight of the formable fabric, for example, more than about 92% by weight of the formable fabric, or at least about 95% by weight of the formable fabric. In a unidirectional fabric, the second fibers may comprise up to about 10% by weight of the formable fabric, such as up to about 8% by weight, or up to about 5% by weight. In a unidirectional fabric, the second direction may be substantially perpendicular to the first direction, the first fibers may comprise greater than 92% by weight of the formable fabric, and the second fibers may comprise up to about 8% by weight of the formable fabric. In an embodiment, the formable fabric is a unidirectional fabric, the second direction is substantially perpendicular to the first direction, and the weight ratio of the first fibers to the second fibers is in the range of 15:1 to 25:1.

[0042] In an embodiment, the formable fabric is a biaxial fabric. In a biaxial fabric, the second direction may be within about 20 degrees to about 90 degrees of the first direction, for example, the second direction may be within about 30 degrees to about 90 degrees of the first direction, the second direction may be within about 40 degrees to about 90 degrees of the first direction, the second direction may be within about 45 degrees to about 90 degrees of the first direction, the second direction may be within about 60 degrees to about 90 degrees of the first direction, within about 70 degrees to about 90 degrees of the first direction, within about 80 degrees to about 90 degrees of the first direction, within about 85 degrees to about 90 degrees of the first direction, within about 88 degrees to about 90 degrees of the first direction, or within about 90 degrees of the first direction. In an embodiment, the formable fabric is a biaxial fabric, wherein the second direction is about 25 degrees to 75 degrees of the first direction, for example, about 45 degrees of the first direction. In an embodiment, the formable fabric is a biaxial fabric, wherein the second direction is at least 45 degrees of the first direction. In an embodiment, the formable fabric is a biaxial fabric, and the second direction is substantially perpendicular to the first direction. In embodiments where the formable fabric is a biaxial fabric, the second fibers comprise greater than 5% by weight of the formable fabric. In embodiments where the formable fabric is a biaxial fabric, the second fibers may comprise at least about 10% by weight of the formable fabric, such as at least about 15% by weight, at least about 20% by weight, or at least about 25% by weight of the formable fabric.

[0043] In embodiments, at least the first fibers or the second fibers comprise, consist essentially of, or consist of glass fibers.

[0044] In embodiments, the first fibers and the second fibers both comprise, consist essentially of, or consist of glass fibers.

[0045] The term "glass fiber" is used herein to refer to a plurality of continuous glass filaments (the term "continuous" as used herein refers to a fiber / filament having a length that is many times its diameter, such as at least about 5000 times its diameter, such as at least about 10000 times its diameter). The glass fiber used in the fabric described herein can be provided as a glass fiber strand (or tow). The glass fiber can be formed by a continuous manufacturing process in which molten glass passes through the holes of a "buffer plate" and the molten glass stream thus formed solidifies into filaments / fibers. The glass fibers described herein (e.g., the glass fibers of the first fiber and / or the second fiber) can include a sizing agent on their surface, such as a sizing agent applied to the glass fibers during fiber formation. The sizing agent can include components that promote the formation of the glass fibers and / or their use in the matrix resin, such as a film former, a lubricant, a coupling agent (to promote compatibility between the glass fibers and the resin used to form a composite product comprising the hybrid fabric described herein), etc. In some embodiments, the glass fibers of the first fibers and / or the second fibers include a polyester compatible sizing or an epoxy compatible sizing.

[0046] As used herein, the term "glass fiber strand" or "glass fiber tow" refers to a bundle of continuous glass filaments. In an embodiment, the glass fiber strand or tow is a plurality of bundles of untwisted glass filaments.

[0047] In an embodiment, the glass fiber strands or glass fiber bundles are provided by glass fiber direct rovings. Glass fiber direct rovings consist of a bundle of continuous untwisted (ie, substantially parallel or parallel) glass filaments bonded (when forming glass filaments) into a single strand and wound onto a bobbin.

[0048] Any suitable glass reinforcing fiber may be used as the first fiber or the second fiber. For example, E glass, E-CR glass (such as Advantex available from Owens Corning) may be used. TM Glass fibers), fibers made of C-glass, H-glass, S-glass, and AR glass types.

[0049] In an embodiment, the linear mass density of the glass fibers referred to herein (e.g., the first fibers that may be glass fibers and / or the second fibers that may be glass fibers) ranges from about 50 tex to about 5000 tex, for example, from about 200 tex to about 4800 tex, from about 300 tex to about 2500 tex, from about 300 tex to about 2400 tex, or from about 600 tex to about 1200 tex.

[0050] The term "carbon fiber" is used herein to refer to a plurality of continuous carbon filaments (the term "continuous" used herein refers to a length that is many times its diameter, for example, at least about 5000 times its diameter, for example, at least about 10000 times its diameter of the fiber / filament). The carbon fiber used in the fabric described herein can be provided as a carbon fiber tow (or strand), which is a plurality of bundles of continuous carbon filaments. The carbon fiber described herein (for example, the carbon fiber of the first fiber and / or the second fiber) may include a sizing agent on their surface, such as a sizing agent applied to the carbon fiber during fiber formation. The sizing agent may include components that promote the formation of carbon fiber and / or its use in the matrix resin, such as a film former, a lubricant, a coupling agent (to promote compatibility between carbon fiber and a resin for forming a composite product comprising a hybrid fabric described herein), etc. In some embodiments, the carbon fiber includes a polyester compatible sizing agent or an epoxy compatible sizing agent.

[0051] In an embodiment, the linear mass density of the carbon fibers ranges from about 100 tex to about 5000 tex, e.g., from about 200 tex to about 5000 tex, from about 400 tex to about 5000 tex, from about 600 tex to about 5000 tex, from about 800 tex to about 5000 tex, from about 100 tex to about 4800 tex, from about 200 tex to about 4800 tex, from 400 tex to about 4800 tex, from about 600 tex to about 4800 tex, 00 tex, about 800 tex to about 4800 tex, about 100 tex to about 2400 tex, about 200 tex to about 2400 tex, about 400 tex to about 2400 tex, about 100 tex to about 2000 tex, about 200 tex to about 2000 tex, about 400 tex to about 2000 tex, about 600 tex to about 2000 tex, about 800 tex to about 2000 tex, or about 1200 tex.

[0052] In an embodiment, the carbon fiber (when present) is provided by a carbon fiber tow (carbon fiber strand). In an embodiment, the size of the carbon fiber tow ranges from 6K to 50K, such as 6K to 24K or 6K to 12K. For example, the first fiber can be fed from one or more carbon fiber tows ranging in size from 6K to 50K, such as 6K to 24K or 6K to 12K. The designation #K means that the carbon tow consists of #×1,000 individual carbon filaments, i.e., a carbon fiber tow of size 6K consists of approximately 6000 carbon fiber filaments / fibers.

[0053] The formable fabric is a non-crepe fabric in which the first fibers and the second fibers are held in their respective orientations by a stitchbonding system (rather than weaving the first fibers and the second fibers together, ie, the non-crepe fabric is a non-woven fabric).

[0054] In an embodiment, the formable fabric has a thickness of about 200 g / m 2 About 2500g / m 2 In the range of, for example, about 300g / m 2 About 2500g / m 2 , for example, about 400 g / m 2 About 2000g / m 2 , for example, about 300 g / m 2 About 2000g / m 2 , for example, about 500 g / m 2 About 1500g / m 2 , for example, about 500 g / m 2 About 1300g / m 2 , for example, about 1300 g / m 2 About 2500g / m 2 The unit area weight of a formable fabric can be determined according to ISO 3374.

[0055] Stitching system

[0056] The stitch bonding systems employed in the formable fabrics described herein include, consist essentially of, or consist of an impregnation component and a forming component.

[0057] In an embodiment, the stitching system comprises, consists essentially of, or consists of: about 15% to about 75% by weight of an impregnated component and about 25% to about 85% by weight of a formed component, based on the total weight of the stitching system; for example, about 20% to about 75% by weight of an impregnated component and about 25% to about 80% by weight of a formed component, based on the total weight of the stitching system; about 25% to about 75% by weight of an impregnated component and about 25% to about 75% by weight of a formed component; about 20% by weight of an impregnated component and about 25% to about 80% by weight of a formed component, based on the total weight of the stitching system; To about 60% by weight of the impregnated parts and about 40% by weight to about 80% by weight of the formed parts; about 25% by weight to about 60% by weight of the impregnated parts and about 40% by weight to about 75% by weight of the formed parts; or about 25% by weight to about 50% by weight of the impregnated parts and about 50% by weight to about 75% by weight of the formed parts; about 20% by weight to about 50% by weight of the impregnated parts and about 50% by weight to about 80% by weight of the formed parts; or about 20% by weight to about 45% by weight of the impregnated parts and about 55% by weight to about 80% by weight of the formed parts.

[0058] In an embodiment, the stitchbonding system comprises from about 0.1% to about 20% by weight of the formable fabric; for example, from about 0.1% to about 15% by weight of the formable fabric; from about 0.1% to about 10% by weight of the formable fabric; from about 0.1% to about 5% by weight of the formable fabric; from about 0.1% to about 3% by weight of the formable fabric; from about 0.25% to about 15% by weight of the formable fabric; from about 0.25% to about 10% by weight of the formable fabric; from about 0.25% to about 5% by weight of the formable fabric; from about 0.25% to about 3% by weight of the formable fabric; from about 0.5% to about 15% by weight of the formable fabric; from about 0.5% to about 10% by weight of the formable fabric; from about 0.5% to about 5% by weight of the formable fabric; or from about 0.5% to about 3% by weight of the formable fabric.

[0059] In embodiments, the forming component of the stitch bonding system comprises about 0.25 wt % to about 4 wt % of the formable fabric; and / or the impregnation component of the stitch bonding system comprises about 0.25 wt % to about 2 wt % of the formable fabric.

[0060] In an embodiment, the stitching system forms a stitching pattern through the fabric, wherein the stitching pattern is selected from a tricot stitching pattern, a symmetrical double tricot stitching pattern, an asymmetrical double tricot stitching pattern, a symmetrical stitching pattern, and an asymmetrical stitching pattern. In an embodiment, the stitching system forms a stitching pattern through the fabric, and the stitching pattern is a tricot stitching pattern. In an embodiment, the stitching system limits a stitch length, and the range of the stitch length is from about 2 mm to about 7 mm, for example, from about 3 mm to about 5 mm.

[0061] Impregnation parts

[0062] In an embodiment, the impregnated component of the stitching system has a melting point of at least about 200°C (e.g., at least about 220°C). In an embodiment, the impregnated component of the stitching system has a melting point in the range of about 200°C to about 350°C or about 220°C to about 330°C. In some embodiments, the impregnated component of the stitching system has a melting point of about 250°C. The melting point of the impregnated component can be determined by differential scanning calorimetry (i.e., the temperature of the peak heat flow obtained by DSC analysis). The melting point of the impregnated component can be determined using differential scanning calorimetry (DSC) according to EN ISO 11357-3:2018 (determination of temperature and enthalpy of melting and crystallization). The melting point of the impregnated component can be determined using differential scanning calorimetry (DSC) according to EN ISO 11357-3:2018 (determination of temperature and enthalpy of melting and crystallization), wherein the melting point is determined as the value provided in the second heating cycle. The melting point of the impregnated part can be determined according to the EN ISO 11357-3:2018 test method by heating the impregnated part at a heating rate of 10 K / min from -60°C to 300°C at an air flow rate of 80 mL / min. In an embodiment, the melting point of the impregnated part can be determined according to the EN ISO 11357-3:2018 test method by heating the impregnated part at a heating rate of 10 K / min from -60°C to 300°C at an air flow rate of 80 mL / min, then holding at 300°C for 5 minutes, then cooling from 300°C to -60°C at a cooling rate of 10 K / min, then holding at -60°C for 5 minutes, then heating again from -60°C to 300°C at a heating rate of 10 K / min, and the melting point is determined as the value provided by the second heating cycle.

[0063] In an embodiment, the impregnated component of the stitchbonding system has a linear density in the range of about 50 dtex to about 200 dtex, for example, a linear density in the range of about 70 dtex to about 200 dtex, a linear density in the range of about 70 dtex to about 175 dtex, or a linear density in the range of about 76 dtex to about 167 dtex.

[0064] In embodiments, the impregnated component comprises, consists essentially of, or consists of a polyester stitching yarn having a melting point in the range of about 200°C to about 350°C and a linear density in the range of about 50 dtex to about 200 dtex.

[0065] Formed parts

[0066] In an embodiment, the forming component of the stitching system has a melting point of less than about 120°C, such as less than about 100°C, less than about 90°C, less than about 80°C, less than about 75°C, less than about 70°C, or less than about 65°C. In an embodiment, the forming component of the stitching system has a melting point in the range of about 40°C to about 120°C, such as about 50°C to about 100°C, about 50°C to about 90°C, about 55°C to about 75°C, or about 55°C to about 65°C. The melting point of the forming component can be determined by differential scanning calorimetry (i.e., the temperature of the peak heat flow obtained by DSC analysis). The melting point of the forming component can be determined using differential scanning calorimetry (DSC) according to EN ISO 11357-3:2018 (Determination of temperature and enthalpy of melting and crystallization). The melting point of the shaped part can be determined using differential scanning calorimetry (DSC) according to EN ISO 11357-3:2018 (Determination of temperature and enthalpy of melting and crystallization), wherein the melting point is determined as the value provided in the second heating cycle. The melting point of the shaped part can be determined according to the EN ISO 11357-3:2018 test method by heating the shaped part from -60°C to 150°C at a heating rate of 10 K / min at an air flow of 80 mL / min. In an embodiment, the melting point of the shaped part can be determined according to the EN ISO 11357-3:2018 test method by heating the shaped part at a heating rate of 10K / min at an air flow rate of 80mL / min, heating from -60°C to 150°C, then holding at 150°C for 5 minutes, then cooling from 150°C to -60°C at a cooling rate of 10K / min, then holding at -60°C for 5 minutes, then heating again from -60°C to 150°C at a heating rate of 10K / min, and the melting point is determined as the value provided by the second heating cycle.

[0067] In an embodiment, the forming component of the stitchbonding system has a linear density in the range of about 50 dtex to about 400 dtex, for example, a linear density in the range of about 100 dtex to about 400 dtex, a linear density in the range of about 100 dtex to about 350 dtex, or a linear density in the range of about 110 dtex to about 330 dtex.

[0068] In an embodiment, the forming part comprises or consists of polyester or polyamide. For example, the forming part may consist of polycaprolactone or copolyamide. For example, the forming part may be selected from polyester yarns or filaments, and polyamide yarns or filaments. For example, the forming part may be selected from polyester yarns or filaments, and polyamide yarns or filaments, and the forming part has a melting point in the range of about 40°C to about 120°C, such as about 50°C to about 100°C, about 50°C to about 90°C, about 55°C to about 75°C, or about 55°C to about 65°C.

[0069] In an embodiment, the forming component comprises, consists essentially of, or consists of polycaprolactone filaments or yarns having a melting point in the range of about 55°C to about 65°C and a linear density in the range of about 100 dtex to about 400 dtex.

[0070] Formable fabrics

[0071] In an embodiment, the formable fabric has a fabric surface, and at least 50% by weight of the forming components are present on the fabric surface, such as at least about 60% by weight of the forming components are present on the fabric surface, at least about 70% by weight of the forming components are present on the fabric surface, or at least about 75% by weight of the forming components are present on the fabric surface. The term "fabric surface" as used herein can be used to refer to the first side of a fabric formed by a first fiber, wherein the first fiber forms a first layer of the fabric and is arranged on a second layer of the fabric formed by a second fiber, and the first side is the side of the first layer opposite to the second layer formed by the second fiber. The amount of the forming components present on the fabric surface can be determined in the following manner: first, the total amount of the components of the stitching system on the first side is determined by the geometry of the stitching pattern on the first side of the fabric, the stitch length of the impregnated components and the forming components, and the total line density, and then the amount of the forming components present on the surface is determined by the relative amount of the impregnated components and the forming components constituting the stitching system.

[0072] In an embodiment, the formable fabric comprises:

[0073] first fibers oriented in a first direction;

[0074] second fibers oriented in a second direction; and

[0075] A stitch bonding system comprising an impregnation component and a forming component,

[0076] The impregnation components and the shaping components of the stitchbonding system form a stitch pattern through the fabric,

[0077] wherein the first fiber comprises glass fiber and / or carbon fiber, the second fiber comprises glass fiber and / or carbon fiber, and the second direction is within 0 to 90 degrees of the first direction, and

[0078] wherein the impregnated component comprises from about 15% to about 75% by weight of the stitching system, and the formed component comprises from about 25% to about 85% by weight of the stitching system, and

[0079] Wherein the forming component of the stitch bonding system has a melting point of less than about 120°C, and wherein the impregnating component of the stitch bonding system has a melting point of at least about 200°C.

[0080] In an embodiment, the formable fabric comprises:

[0081] first fibers oriented in a first direction;

[0082] second fibers oriented in a second direction; and

[0083] A stitch bonding system comprising an impregnation component and a forming component,

[0084] The impregnation components and the shaping components of the stitchbonding system form a stitch pattern through the fabric,

[0085] wherein the first fiber comprises a glass fiber, the second fiber comprises a glass fiber, and the second direction is within 0 degrees to 90 degrees of the first direction, and

[0086] wherein the impregnated component comprises from about 15% to about 75% by weight of the stitching system, and the formed component comprises from about 25% to about 85% by weight of the stitching system, and

[0087] Wherein the forming component of the stitch bonding system has a melting point of less than about 120°C, and wherein the impregnating component of the stitch bonding system has a melting point of at least about 200°C.

[0088] In an embodiment, the formable fabric comprises:

[0089] first fibers oriented in a first direction;

[0090] second fibers oriented in a second direction; and

[0091] A stitch bonding system comprising an impregnation component and a forming component,

[0092] The impregnation components and the shaping components of the stitchbonding system form a stitch pattern through the fabric,

[0093] wherein the first fiber comprises glass fiber and / or carbon fiber, the second fiber comprises glass fiber and / or carbon fiber, and the second direction is within 0 to 90 degrees of the first direction, and

[0094] wherein the impregnated component comprises from about 25% to about 75% by weight of the stitching system, and the formed component comprises from about 25% to about 75% by weight of the stitching system, and

[0095] Wherein the forming component of the stitch bonding system has a melting point of less than about 120°C, and wherein the impregnating component of the stitch bonding system has a melting point of at least about 200°C.

[0096] In an embodiment, the formable fabric comprises:

[0097] first fibers oriented in a first direction;

[0098] second fibers oriented in a second direction; and

[0099] A stitch bonding system comprising an impregnation component and a forming component,

[0100] The impregnation components and the shaping components of the stitchbonding system form a stitch pattern through the fabric,

[0101] wherein the first fiber comprises a glass fiber, the second fiber comprises a glass fiber, and the second direction is within 0 degrees to 90 degrees of the first direction, and

[0102] wherein the impregnated component comprises from about 25% to about 75% by weight of the stitching system, and the formed component comprises from about 25% to about 75% by weight of the stitching system, and

[0103] Wherein the forming component of the stitch bonding system has a melting point of less than about 120°C, and wherein the impregnating component of the stitch bonding system has a melting point of at least about 200°C.

[0104] In an embodiment, the formable fabric comprises:

[0105] first fibers oriented in a first direction;

[0106] second fibers oriented in a second direction; and

[0107] A stitch bonding system comprising an impregnation component and a forming component,

[0108] The impregnation components and the shaping components of the stitchbonding system form a stitch pattern through the fabric,

[0109] wherein the first fiber comprises glass fiber and / or carbon fiber, the second fiber comprises glass fiber and / or carbon fiber, and the second direction is within 0 to 90 degrees of the first direction, and

[0110] wherein the impregnated component comprises from about 25% to about 75% by weight of the stitching system, and the formed component comprises from about 25% to about 75% by weight of the stitching system, and

[0111] wherein the stitchbonding system comprises from about 0.1% to about 10% by weight of the formable fabric, and

[0112] Wherein the forming component of the stitch bonding system has a melting point of less than about 120°C, and wherein the impregnating component of the stitch bonding system has a melting point of at least about 200°C.

[0113] In an embodiment, the formable fabric comprises:

[0114] first fibers oriented in a first direction;

[0115] second fibers oriented in a second direction; and

[0116] A stitch bonding system comprising an impregnation component and a forming component,

[0117] The impregnation components and the shaping components of the stitchbonding system form a stitch pattern through the fabric,

[0118] wherein the first fiber comprises a glass fiber, the second fiber comprises a glass fiber, and the second direction is within 0 degrees to 90 degrees of the first direction, and

[0119] wherein the impregnated component comprises from about 25% to about 75% by weight of the stitching system, and the formed component comprises from about 25% to about 75% by weight of the stitching system, and

[0120] wherein the stitchbonding system comprises from about 0.1% to about 10% by weight of the formable fabric, and

[0121] Wherein the forming component of the stitch bonding system has a melting point of less than about 120°C, and wherein the impregnating component of the stitch bonding system has a melting point of at least about 200°C.

[0122] In an embodiment, the formable fabric comprises:

[0123] first fibers oriented in a first direction;

[0124] second fibers oriented in a second direction; and

[0125] A stitch bonding system comprising an impregnation component and a forming component,

[0126] The impregnation components and the shaping components of the stitchbonding system form a stitch pattern through the fabric,

[0127] wherein the first fiber comprises glass fiber and / or carbon fiber, the second fiber comprises glass fiber and / or carbon fiber, and the second direction is within 0 to 90 degrees of the first direction, and

[0128] wherein the impregnated component comprises from about 25% to about 75% by weight of the stitching system, and the formed component comprises from about 25% to about 75% by weight of the stitching system, and

[0129] wherein the stitchbonding system comprises from about 0.1% to about 5% by weight of the formable fabric, and

[0130] Wherein the forming component of the stitch bonding system has a melting point of less than about 120°C, and wherein the impregnating component of the stitch bonding system has a melting point of at least about 200°C.

[0131] In an embodiment, the formable fabric comprises:

[0132] first fibers oriented in a first direction;

[0133] second fibers oriented in a second direction; and

[0134] A stitch bonding system comprising an impregnation component and a forming component,

[0135] The impregnation components and the shaping components of the stitchbonding system form a stitch pattern through the fabric,

[0136] wherein the first fiber comprises a glass fiber, the second fiber comprises a glass fiber, and the second direction is within 0 degrees to 90 degrees of the first direction, and

[0137] wherein the impregnated component comprises from about 25% to about 75% by weight of the stitching system, and the formed component comprises from about 25% to about 75% by weight of the stitching system, and

[0138] wherein the stitchbonding system comprises from about 0.1% to about 5% by weight of the formable fabric, and

[0139] Wherein the forming component of the stitch bonding system has a melting point of less than about 120°C, and wherein the impregnating component of the stitch bonding system has a melting point of at least about 200°C.

[0140] In an embodiment, the formable fabric comprises:

[0141] first fibers oriented in a first direction;

[0142] second fibers oriented in a second direction; and

[0143] A stitch bonding system comprising an impregnation component and a forming component,

[0144] The impregnation components and the shaping components of the stitchbonding system form a stitch pattern through the fabric,

[0145] wherein the first fiber comprises glass fiber and / or carbon fiber, the second fiber comprises glass fiber and / or carbon fiber, and the second direction is within 0 to 90 degrees of the first direction, and

[0146] wherein the impregnated component comprises from about 25% to about 75% by weight of the stitching system, and the formed component comprises from about 25% to about 75% by weight of the stitching system, and

[0147] wherein the stitchbonding system comprises from about 0.1% to about 10% by weight of the formable fabric, and

[0148] Wherein the forming component of the stitch bonding system has a melting point of less than about 100°C, and wherein the impregnating component of the stitch bonding system has a melting point in the range of about 200°C to about 350°C.

[0149] In an embodiment, the formable fabric comprises:

[0150] first fibers oriented in a first direction;

[0151] second fibers oriented in a second direction; and

[0152] A stitch bonding system comprising an impregnation component and a forming component,

[0153] The impregnation components and the shaping components of the stitchbonding system form a stitch pattern through the fabric,

[0154] wherein the first fiber comprises glass fiber and / or carbon fiber, the second fiber comprises glass fiber and / or carbon fiber, and the second direction is within 0 to 90 degrees of the first direction, and

[0155] wherein the impregnated component comprises about 20% to about 60% by weight of the stitching system, and the formed component comprises about 40% to about 80% by weight of the stitching system, and

[0156] wherein the stitchbonding system comprises from about 0.1% to about 10% by weight of the formable fabric, and

[0157] Wherein the forming component of the stitch bonding system has a melting point of less than about 100°C, and wherein the impregnating component of the stitch bonding system has a melting point in the range of about 200°C to about 350°C.

[0158] In an embodiment, the formable fabric comprises:

[0159] first fibers oriented in a first direction;

[0160] second fibers oriented in a second direction; and

[0161] A stitch bonding system comprising an impregnation component and a forming component,

[0162] The impregnation components and the shaping components of the stitchbonding system form a stitch pattern through the fabric,

[0163] wherein the first fiber comprises glass fiber and / or carbon fiber, the second fiber comprises glass fiber and / or carbon fiber, and the second direction is within 0 to 90 degrees of the first direction, and

[0164] wherein the impregnated component comprises from about 25% to about 60% by weight of the stitching system, and the formed component comprises from about 40% to about 75% by weight of the stitching system, and

[0165] wherein the stitchbonding system comprises from about 0.1% to about 10% by weight of the formable fabric, and

[0166] Wherein the forming component of the stitch bonding system has a melting point of less than about 100°C, and wherein the impregnating component of the stitch bonding system has a melting point in the range of about 200°C to about 350°C.

[0167] Fabric Lamination

[0168] The fabric laminate comprises at least two formable fabric layers as described herein.

[0169] In an embodiment, a fabric laminate comprises at least two formable fabric layers as described herein, wherein one formable fabric layer is directly disposed on another formable fabric layer. In an embodiment, a fabric laminate comprises at least 3 formable fabric layers as described herein, for example at least 4, at least 5, at least 6 or at least 8 formable fabric layers as described herein. In an embodiment, a fabric laminate comprises at most 50 formable fabric layers as described herein, for example at most 30, at most 25, at most 20, at most 15, at most 10 formable fabric layers as described herein. In an embodiment, a fabric laminate comprises 2 to 50 formable fabric layers as described herein, for example 4 to 30 or 6 to 25 formable fabric layers as described herein. In an embodiment, a fabric laminate comprises a plurality of formable fabric layers as described herein, wherein each layer in a plurality of formable fabric layers is directly disposed on another layer in a plurality of formable fabric layers.

[0170] In an embodiment, the layers of the fabric laminate are adhered to each other. A fabric laminate in which the layers of the fabric laminate are adhered to each other may be referred to herein as a "consolidated fabric laminate".

[0171] In an embodiment, the layers of the fabric laminate may be adhered to each other by suitable treatments such as heating, curing, or exposure to UV radiation. In an embodiment, the layers of the fabric laminate may be adhered to each other by heating the fabric laminate so that the forming components of the stitching system of the first formable fabric layer adhere the first formable fabric layer to the second formable fabric layer.

[0172] In an embodiment, the layers of the fabric laminate may be adhered to each other by heating the fabric laminate to a temperature of at least the melting point of the forming component of the stitching system, such as heating to a temperature at least about 5°C higher than the melting point of the forming component of the stitching system, heating to a temperature at least about 10°C higher than the melting point of the forming component of the stitching system, or heating to a temperature at least about 15°C higher than the melting point of the forming component of the stitching system. In an embodiment, the layers of the fabric laminate may be adhered to each other by heating the fabric laminate to a temperature of at least about 60°C, such as at least about 65°C, at least about 70°C, or at least about 80°C. In an embodiment, the layers of the fabric laminate may be adhered to each other by heating the fabric laminate to a temperature of up to about 150°C, such as up to about 130°C, up to about 120°C, or up to about 100°C. In an embodiment, the layers of the fabric laminate may be adhered to each other by heating the fabric laminate to a temperature in the range of about 60°C to about 120°C, such as about 65°C to about 100°C. In an embodiment, the layers of the fabric laminate may be adhered to one another by heating the fabric laminate as described above for a period of about 1 minute or more, such as up to about 1 hour.

[0173] In embodiments, the consolidated fabric laminate may be produced by vacuum heating the fabric laminate, for example, heating the fabric laminate at a pressure below atmospheric pressure (e.g., a pressure ranging from about 100 mbar to about 1000 mbar, or from about 100 mbar to about 900 mbar, from about 100 mbar to about 800 mbar, from about 100 mbar to about 700 mbar, from about 100 mbar to about 600 mbar, or from about 100 mbar to about 400 mbar).

[0174] In embodiments, the fabric laminate is exposed to elevated temperature (ie, heat) and / or reduced pressure for a period of up to about 5 hours, such as up to about 3 hours, up to about 2 hours, or up to about 1 hour, to form a consolidated fabric laminate.

[0175] In embodiments, the interlayer bond strength between successive layers of the consolidated fabric laminates described herein is at least about 5 N / 50 mm, such as at least about 6 N / 50 mm, or at least about 8 N / 50 mm. Interlayer adhesion may be determined according to the T-peel ISO 11339 standard test method or similar methods.

[0176] In embodiments, the fabric layups described herein may be impregnated with a resin and the resin cured to form a composite article.

[0177] Method for producing a formable fabric

[0178] A method for producing a formable fabric may include:

[0179] Providing first fibers oriented in a first direction and second fibers oriented in a second direction, wherein the first fibers include glass fibers and / or carbon fibers, the second fibers include glass fibers and / or carbon fibers, and the second direction is within 0 to 90 degrees of the first direction; and

[0180] The first fiber and the second fiber are stitched together using a stitching system, the stitching system comprising an impregnated component and a formed component, wherein the stitching system comprises about 25 weight % to about 85 weight % of the impregnated component and about 15 weight % to about 75 weight % of the formed component based on the total weight of the stitching system.

[0181] In an embodiment, stitching the first fibers and the second fibers together using the stitching system includes stitching the first fibers and the second fibers together with the impregnation component and the forming component simultaneously.

[0182] Formed parts

[0183] The shaped part comprises a fabric layup as described herein.

[0184] Formed parts can be produced by the following steps:

[0185] a) providing a fabric laminate as described herein;

[0186] b) shaping the fabric laminate; and

[0187] c) heating the shaped stack at a temperature of, for example, up to about 150°C.

[0188] In an embodiment, heating the fabric laminate comprises heating the fabric laminate at a temperature of at least about 50° C., such as at least about 60° C., at least about 70° C., at least about 80° C., at least about 90° C., or at least about 100° C. In an embodiment, heating the fabric laminate comprises heating the fabric laminate at a temperature of up to about 150° C., such as up to about 130° C., or up to about 120° C. In an embodiment, heating the fabric laminate comprises heating the fabric laminate at a temperature in the range of about 50° C. to about 150° C., such as about 70° C. to about 130° C., or about 80° C. to about 120° C.

[0189] In an embodiment, producing the formed part may include vacuum heating the fabric stack, for example, heating the fabric stack at a pressure below atmospheric pressure (e.g., a pressure ranging from about 100 mbar to about 1000 mbar, or from about 100 mbar to about 900 mbar, from about 100 mbar to about 800 mbar, from about 100 mbar to about 700 mbar, from about 100 mbar to about 600 mbar, or from about 100 mbar to about 400 mbar).

[0190] In an embodiment, the fabric laminate is exposed to an elevated temperature (i.e., heated) and / or reduced pressure for a period of up to about 5 hours, e.g., up to about 3 hours, up to about 2 hours, or up to about 1 hour, to form a shaped article. In an embodiment, the fabric laminate is exposed to an elevated temperature (i.e., heated) and / or reduced pressure for a period of at least about 10 minutes, e.g., at least about 30 minutes, to form a shaped article. In an embodiment, the fabric laminate is exposed to an elevated temperature (i.e., heated) and / or reduced pressure for a period of about 10 minutes to about 5 hours, e.g., about 30 minutes to about 2 hours or about 30 minutes to about 1 hour.

[0191] In an embodiment, shaping the fabric layup involves placing the fabric layup on or in a mold. In an embodiment, shaping the fabric layup involves placing the fabric layup on or in a mold and applying increased heat and / or reduced pressure to the fabric layup.

[0192] In embodiments, a shaped part described herein may be impregnated with a resin, such as an epoxy or polyester resin, and the resin cured to form a composite article.

[0193] Example

[0194] The following are examples of fabrics and related aspects described herein. Therefore, these examples should not be considered as limiting the present disclosure, but are only used to teach how to implement the methods of the present disclosure and obtain the products of the present disclosure.

[0195] Stitch bonding system used in the examples

[0196] Impregnated part - An impregnated polyester stitching yarn with a linear density of 76 dtex was used as the impregnated part in the stitching system used in the following embodiments. The impregnated polyester stitching yarn has a melting point in the range of 250°C-260°C, which is determined by differential scanning calorimetry as the temperature at which the polyester stitching yarn is completely melted (i.e., the temperature of the peak heat flow obtained by DSC analysis). The melting point of the impregnated part is determined according to the EN ISO 11357-3:2018 test method in the following manner: the impregnated part is heated at a heating rate of 10K / min at an air flow rate of 80mL / min, from -60°C to 300°C, then maintained at 300°C for 5 minutes, then cooled from 300°C to -60°C at a cooling rate of 10K / min, then maintained at -60°C for 5 minutes, then heated again from -60°C to 300°C at a heating rate of 10K / min, and the melting point is determined as the value provided by the second heating cycle.

[0197] Forming Part - A polyester forming yarn (specifically, a polycaprolactone yarn consisting of 34 filaments, each filament having a diameter of 21 μm) having a linear density of 167 dtex and a melting point of about 60°C (determined by differential scanning calorimetry as the temperature at which the polyester stitching yarn is completely melted (i.e., the temperature of the peak heat flow obtained by DSC analysis)) was used as a forming part in the stitching system used in the following examples. The melting point of the forming part was determined according to the EN ISO 11357-3:2018 test method by heating the forming part at a heating rate of 10 K / min at an air flow rate of 80 mL / min, from -60°C to 120°C, then holding at 120°C for 5 minutes, then cooling from 120°C to -60°C at a cooling rate of 10 K / min, then holding at -60°C for 5 minutes, then heating again from -60°C to 120°C at a heating rate of 10 K / min, and the melting point was determined as the value provided by the second heating cycle.

[0198] Example 1

[0199] A formable unidirectional fabric is produced by providing a first layer of first glass fibers oriented in a 0° direction (i.e., aligned with the length of the fabric), the first layer being disposed on a second layer of second glass fibers oriented substantially perpendicular to the 0° direction (i.e., substantially perpendicular to the length of the fabric), and stitching the first fibers and the second fibers together using a stitching system. The first fibers have a unit weight of 1322 g / m 2 , and the second fiber has a unit area weight of 75 g / m 2 . As described above, the stitching system is composed of a polyester impregnated yarn and a polycaprolactone forming yarn. First, the first glass fiber and the second glass fiber are stitched together using the polyester stitching yarn and the polycaprolactone yarn simultaneously to maintain their respective orientations. The weight ratio of the polycaprolactone forming yarn to the polyester impregnated yarn of the provided stitching system is 2:1. Using the impregnation component and the forming component of the stitching system, a double equal column tricot warp knitted fabric stitching pattern is used to stitch the first fiber and the second fiber together, so that the double equal column tricot warp knitted fabric stitching pattern (a symmetrical combination of column and tricot warp knitted fabric stitches) is formed through the formable fabric in a direction substantially perpendicular to the 0° direction.

[0200] Example 2

[0201] A formable fabric is produced as described in Example 1, except that a double tricot stitch pattern is used to stitch the first fibers and the second fibers together using the impregnation component and the forming component of the stitching system such that the double tricot stitch pattern is formed through the formable fabric.

[0202] Comparative Example 3

[0203] A formable fabric was produced as described in Example 1, except that the stitchbonding system consisted of forming components only, ie no impregnation components were used.

[0204] Comparative Example 4

[0205] A formable fabric was produced as described in Example 2, except that the stitchbonding system consisted of forming components only, ie no impregnation components were used.

[0206] Example 5

[0207] A formable fabric is produced as described in Example 1, except that the weight ratio of the polycaprolactone forming yarn to the polyester impregnated yarn of the provided stitching system is 1:1, and using the impregnation component and the forming component of the stitching system, an asymmetric double tricot warp knitted fabric stitching pattern is used to stitch the first fiber and the second fiber together, so that the asymmetric double tricot warp knitted fabric pattern is formed through the formable fabric.

[0208] Table 1 below summarizes the stitching system used on the first side of the formable fabric (the first side is the surface of the first layer opposite the second fiber) and the amount of the impregnated component and the shaping component. The amount of yarn on the first side (in a unidirectional fabric, the first side is selected as the side formed by the first fiber, and the first fiber is present in an amount of at least 90% by weight of the fabric in a unidirectional fabric) is determined by the geometry of the stitching pattern on the first side of the impregnated component and the shaping component, the stitch length and the total number of threads.

[0209] For example, the yarn count of the stitching system on the first side of the formable fabric produced in Example 2 was determined as follows:

[0210] The length of a single stitch is determined using the Pythagorean theorem from the stitch length of the stitch pattern (measured along the 0° direction) and the stitch width of the stitch pattern (measured along the 90° direction).

[0211] The total stitch yarn weight at the surface of the formable fabric can then be calculated as follows:

[0212] Total stitching yarn weight at the surface =

[0213] Total number of stitches per meter of fabric × length of single stitch × linear density of stitching yarn

[0214] The relative amounts of the forming component and the impregnating component can then be used to determine the amount of the forming component on the first side of the fabric.

[0215] The amount of yarn on the first side of the fabric is determined by the stitching pattern used to stitch the first fibers and the second fibers together with the stitching system.

[0216] Table 1

[0217]

[0218]

[0219] Immersion test

[0220] The formable fabrics produced according to Examples 1, 2 and 5 and Comparative Examples 2 and 3 were then formed into a fabric laminate by stacking 5 layers, with a different fabric laminate being formed for each of the formable fabrics of Examples 1, 2 and 5 and Comparative Example 2. The fabric laminate was consolidated by placing under vacuum (pressure reduction of 0.6 bar) and heating at 65° C. for 1 hour. The consolidated fabric laminate was then cooled to room temperature and removed from the vacuum. The cooled consolidated fabric laminate was then impregnated with this polyester resin under vacuum (pressure reduction of 0.6 bar), and the impregnation speed was measured in the first direction and the second direction.

[0221] It was found that the formable fabrics of Examples 1, 2 and 5 provided consolidated fabric laminates with good impregnation properties in both the first and second directions (similar to those of the reference fabric prepared according to Example 1 but comprising a stitching system without a forming component). It was found that the impregnation properties of the formable fabrics of Examples 1, 2 and 5 were greatly improved in the second direction compared to the formable fabrics produced according to Comparative Examples 3 and 4 (fabrics comprising a stitching system without an impregnation component).

[0222] Forming test

[0223] The formable fabric was then formed into a fabric stack by stacking 6 layers on a V-shaped mold. The formed stack was heated at 65°C for 1 hour, and a different fabric stack was formed for each of the formable fabrics of Examples 1, 2, and 5 to form a formed part. All of the formed parts showed good shape retention and stiffness. Compared to the formed part formed from the formable fabric of Example 5, the formed parts formed from the formable fabrics of Examples 1 and 2 were found to have improved stiffness when handled because a larger amount of forming parts were used in the fabrics of Examples 1 and 2.

[0224] Stiffness test

[0225] The formable fabrics produced according to Examples 1, 2 and 5 and Comparative Examples 2 and 3 were then formed into fabric stacks by stacking 2 layers (each layer having a size of 50 mm x 20 mm), with a different fabric stack being formed for each of the formable fabrics of Examples 1, 2 and 5 and Comparative Example 2. The fabric stack was consolidated by placing under vacuum (pressure reduction of 0.6 bar) and heating at 65° C. for 1 hour. The consolidated fabric stack was then cooled to room temperature and removed from the vacuum.

[0226] Each cooled consolidated fabric stack was then subjected to a stiffness test using a bending tester (standard DIN 53121). This was repeated once for each sample to avoid memory effects of the specimen block after the first bending. During the test, the bending angle was set to 5° and the test length was 25 mm (distance between the clamp and the sensor).

[0227] It was found that the stiffness of the fabric laminate is directly related to the total amount of forming components used in the stitching system, but the amount of forming components on the first side of the fabric also affects the stiffness, which results in the fabric laminate of Example 2 having a greater stiffness than the fabric laminate of Example 1 due to the greater amount of forming components on the first side of the fabric.

[0228] Thus, the present inventors have discovered that providing a wrinkle-free fabric using a stitchbonding system comprising both an impregnation component and a forming component as described herein provides a formable fabric that exhibits good impregnation and stiffness properties.

[0229] Fatigue resistance

[0230] The fatigue properties discussed below may be determined under cyclic loading conditions using a test method performed in accordance with ISO 13003:2003 or any other similar method.

[0231] The inventors have also found that the formable fabrics described herein (e.g., the formable fabrics of Examples 1, 2, and 5) can be incorporated into composite articles to produce composite articles with good fatigue resistance. For example, the formable fabrics of Examples 1, 2, and 5 are formed into fabric stacks as described above for the impregnation test and impregnated with a polyester resin as described above for the impregnation test to form a composite sheet. Composite sheets containing the formable fabrics of the above embodiments were subjected to fatigue testing and were found to have a maximum strain in the range of 0.7% to 0.9% for 1 million cycles and a maximum stress in the range of 250 MPa to 350 MPa for 1 million cycles. The results obtained by the inventors for the maximum strain and stress of the test samples also indicate (by the slope of the fatigue curve obtained from the results) that excellent fatigue performance is expected at even higher cycle numbers.

[0232] After the above fatigue testing, the inventors have surprisingly discovered that composite articles comprising the formable fabrics described herein (e.g., the formable fabrics of Examples 1, 2, and 5) exhibit greatly improved fatigue resistance compared to comparative composite articles comprising standard control fabrics (i.e., fabrics such as those described in Examples 1, 2, and 5, but the stitching system does not contain a forming component).

[0233] Interlayer Adhesion

[0234] The inventors have also discovered that the formable fabrics described herein (e.g., the formable fabrics of Examples 1, 2, and 5) exhibit excellent interlayer adhesion between successive layers of formable fabric that have been consolidated by exposure to temperatures near or above the melting point of the forming components of the stitching system.

[0235] The interlayer adhesion can be determined according to the T peel ISO11339 standard test method or a similar method. This test method is used to evaluate the interlayer adhesion of a consolidated fabric laminate formed by a formable fabric layer produced according to Examples 1, 2 and 5. The fabric laminate is consolidated by placing it under vacuum (pressure reduction of 0.6 bar) and heating at 65°C for 1 hour. The consolidated fabric laminate is then cooled to room temperature and removed from the vacuum. The interlayer adhesion of each consolidated laminate is then evaluated. It was found that the consolidated fabric laminate produced by the fabric described herein (e.g., as described in Examples 1, 2 and 5) exhibited excellent interlayer adhesion, and the bond strength increased with the increase in the amount of forming yarn. Surprisingly, it was found that the bond strength was very good after consolidation at a very low temperature (65°C).

[0236] The interlayer adhesion of consolidated fabric laminates formed from formable fabric layers produced according to Example 2 was further investigated. The fabric laminates were consolidated by placing under vacuum (pressure reduction of 0.6 bar) and heating for 1 hour, wherein each fabric laminate was heated to a different temperature in the range of 60°C to 140°C. The consolidated fabric laminates were then cooled to room temperature and removed from the vacuum. The interlayer adhesion of each consolidated laminate was then evaluated according to a test method based on the T-peel ISO 11339 standard test method. The results are shown in Figure 1 A graph is provided showing the relationship between the bond strength (T peel strength in N / 50 mm) and the temperature at which the fabric laminate is consolidated. Not only was it surprising to find that the bond strength was so good after consolidation at a very low temperature (65°C), but it was further surprising that by increasing the consolidation temperature from 60°C to 80°C, the increase in interlayer adhesion increased significantly.

[0237] The present inventors have found that the formable fabrics described herein have low stiffness during layup and molding while providing excellent inter-ply adhesion after consolidation. These properties make the formable fabrics described herein very useful in providing reinforced structural components such as wind turbine blades.

[0238] The inventors also studied the porosity of laminates formed using fabric stacks formed from the fabrics of each of Examples 1 to 5 above, which were impregnated with a polyester resin to form laminates. Using the standard Archimedean method, each laminate (containing the fabrics of Examples 1 to 5) was found to have an acceptable average porosity value (between 0% and 2%), demonstrating that the inclusion of the shaped yarn does not adversely affect the porosity.

[0239] The inventors anticipate that fabrics similar to the fabrics of Examples 1-5 but containing polyamide forming yarns having a melting temperature of about 85°C will provide similarly improved results as the formable fabrics produced according to Examples 1-5, although slightly higher temperatures of 85°C-90°C are required for consolidation / forming.

[0240] The inventors contemplate that formable fabrics having other configurations, such as biaxial fabrics, as described herein provide formable fabrics that provide similar advantages as the unidirectional formable fabrics employed in these embodiments.

[0241] In addition, the inventors have discovered that the fabric layups or formed parts described herein can be used to significantly improve the layup speed of a composite article comprising the formed parts described herein. For example, a formed part comprising the formable fabric described herein can be employed during the manufacture of a wind turbine blade by directly incorporating the formed part into the wind turbine blade during the layup process.

[0242] The features disclosed in the foregoing description or in the following claims, expressed in their specific form or in terms of means for performing the disclosed functions or methods or processes for obtaining the disclosed results, may, where appropriate, be used alone or in any combination of these features to implement the invention in its various forms.

[0243] Although the present invention has been described in conjunction with the above exemplary embodiments, many equivalent modifications and variations will be apparent to those skilled in the art when this disclosure is given. Therefore, the exemplary embodiments of the present invention set forth above are considered to be illustrative rather than restrictive. Various changes may be made to the described embodiments without departing from the spirit and scope of the present invention.

[0244] For the avoidance of any doubt, any theoretical explanations provided herein are intended to enhance the reader's understanding. The inventors do not wish to be bound by any of these theoretical explanations.

[0245] Any section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described.

[0246] If a standard test is referred to herein, the version of the test referred to is the most recent version at the time this patent application was filed, unless otherwise stated.

[0247] Throughout this specification, including the claims that follow, unless the context requires otherwise, the words "comprise" and "comprising" and variations such as "have" and "containing", will be understood to imply the inclusion of stated integers or steps or groups of integers or steps but not the exclusion of any other integers or steps or groups of integers or steps.

[0248] It must be noted that, as used in the specification and the appended claims, the singular forms "a", "an", and "the" include plural referents unless the context clearly indicates otherwise. Ranges may be expressed herein as from "about" one particular value and / or to "about" another particular value. When such a range is expressed, another embodiment includes from the one particular value and / or to the other particular value. Similarly, when a value is expressed as an approximation by using the antecedent "about", it should be understood that the particular value forms another embodiment. The term "about" in relation to a numerical value is optional and means, for example, + / - 10%.

Claims

1. A formable fabric, comprising: first fibers oriented in a first direction; second fibers oriented in a second direction; and A stitch bonding system comprising an impregnation component and a forming component, The impregnation component and the shaping component of the stitching system form a stitching pattern through the fabric, wherein the first fibers include glass fibers and / or carbon fibers, the second fibers include glass fibers and / or carbon fibers, and the second direction is within 0 to 90 degrees of the first direction, and The impregnation component comprises about 15% to about 75% by weight of the stitching system, and the forming component comprises about 25% to about 85% by weight of the stitching system.

2. The formable fabric of claim 1, wherein the forming components of the stitch bonding system have a melting point of less than about 100°C.

3. A formable fabric according to claim 1 or claim 2, wherein the impregnated component of the stitch bonding system has a melting point in the range of about 200°C to about 350°C.

4. A formable fabric according to any one of the preceding claims, wherein the impregnated component comprises from about 20% to about 60% by weight of the stitching system, and the forming component comprises from about 40% to about 80% by weight of the stitching system.

5. The formable fabric of any one of claims 1 to 3, wherein the impregnated component comprises about 25% to about 75% by weight of the stitching system, and the forming component comprises about 25% to about 75% by weight of the stitching system.

6. A formable fabric according to any one of the preceding claims, wherein the formable fabric has a fabric surface and at least 50% by weight of the forming component is present on the fabric surface.

7. A formable fabric according to any one of the preceding claims, wherein the shaping member is comprised of polyester or polyamide.

8. A formable fabric according to any one of the preceding claims, wherein the formable fabric has a thickness of about 300 g / m 2 About 2500g / m 2 Weight per unit area within the range.

9. The formable fabric of any one of the preceding claims, wherein the stitchbonding system comprises from about 0.1% to about 20% by weight of the formable fabric.

10. A formable fabric according to any one of the preceding claims, wherein the impregnated component of the stitchbonding system has a linear density in the range of about 50 dtex to about 200 dtex.

11. A formable fabric according to any one of the preceding claims, wherein the forming components of the stitch bonding system have a linear density in the range of about 50 dtex to about 400 dtex.

12. A formable fabric according to any of the preceding claims, wherein the forming component of the stitching system accounts for about 0.25 weight % to about 4 weight % of the formable fabric; and / or the impregnation component of the stitching system accounts for about 0.25 weight % to about 2 weight % of the formable fabric.

13. A fabric laminate comprising at least two layers of a formable fabric according to any one of claims 1 to 12, wherein one layer of a formable fabric according to any one of claims 1 to 12 is directly disposed on another layer of a formable fabric according to any one of claims 1 to 12.

14. The fabric laminate according to claim 13, wherein the fabric laminate is a consolidated fabric laminate and the interlayer bond strength between consecutive layers of the consolidated fabric laminate is at least about 6 N / 50 mm.

15. A shaped component comprising a fabric layup according to claim 13 or claim 14.

16. A method for producing a formable fabric, the method comprising: Providing first fibers oriented in a first direction and second fibers oriented in a second direction, wherein the first fibers include glass fibers and / or carbon fibers, the second fibers include glass fibers and / or carbon fibers, and the second direction is within 0 to 90 degrees of the first direction; as well as The first fibers and the second fibers are stitched together using a stitching system, the stitching system comprising an impregnated component and a formed component, wherein the impregnated component accounts for about 15 weight % to about 75 weight % of the stitching system, and the formed component accounts for about 25 weight % to about 85 weight % of the stitching system.

17. The method of claim 16, wherein the forming component of the stitch bonding system has a melting point of less than about 100°C.

18. The method of claim 16 or 17, wherein the impregnated component of the stitchbonding system has a melting point in the range of about 200°C to about 350°C.

19. The method of any one of claims 16 to 18, wherein the impregnated component comprises about 25% to about 75% by weight of the stitching system, and the formed component comprises about 25% to about 75% by weight of the stitching system.

20. A method for producing a shaped part, the method comprising: stacking a plurality of layers of a formable fabric according to any one of claims 1 to 12 to provide a fabric layup; shaping the fabric laminate; as well as The fabric laminate is heated at a temperature of up to about 150°C.

21. The method of claim 20, comprising heating the fabric layup at a temperature of up to about 150°C under vacuum.

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