Shaped preform for a face portion of a composite wheel

Abstract

A shaped preform component (200) for a face portion (104) of a composite wheel (100), the shaped preform (200) having a hub (206) extending about a central axis (Y), the shaped preform component (200) being formed of a cured composite fiber material having a compressibility of less than 2% by volume under molding conditions of a hydrostatic pressure of 50 bar and a temperature of 60°C to 200°C.

Description

[0001] This application is a divisional application of patent application number 2018800682045, filed on 17 August 2018, entitled “Shaped preform for face portion of a composite wheel”.

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This application claims priority from Australian provisional patent application No. 2017903324 filed on 18 August 2017, the contents of which are to be taken as incorporated herein by this reference. TECHNICAL FIELD

[0004] The present invention relates generally to shaped preforms for use in the manufacture of face portions of composite wheels. The invention is particularly applicable to composite carbon fibre wheels for vehicles and / or aircraft, and it will be convenient to disclose the invention hereinbelow with respect to such exemplary applications. However, it will be appreciated that the invention is not limited to such applications, and can be used as an aid in the production of a wide variety of composite type wheels. BACKGROUND

[0005] The following discussion of the background of the invention is intended to facilitate an understanding of the invention. However, it should be appreciated that the discussion is not an acknowledgement or admission that any of the material referred to was published, known or part of the common general knowledge as at the priority date of the application.

[0006] Composite wheels generally comprise two main portions, a rim portion and a face portion. The rim portion comprises an annular structure configured to receive and seat a tyre. The face portion comprises a hub for securing the wheel to a vehicle, and a connecting structure, such as a series of spokes or webs, extending between and interconnecting the hub and the rim. Lateral, vertical and torsional loads are transmitted through the tyre to the rim portion of the wheel, and then generate bending and torsional stresses in the connecting structure.

[0007] The applicant of the present application has produced a one-piece composite wheel, such as described in international patent publication WO2010 / 024495A1. Manufacture of a one-piece composite wheel generally requires the use of separate rim portion moulds and associated reinforcements, and face portion moulds and associated reinforcements. The separate rim mould portion and face mould portion are then interconnected in a final forming process, which allows the entire composite wheel to be formed integrally. It is desirable to have a face portion (particularly the hub portion and its interconnection with the spokes) that is rigid, strong and dimensionally stable to provide a mechanically efficient structure that has rigidity and strength, and also efficiently transmits loads generated between the tyre and the ground through the rim to the spokes and all the way to the axle of the vehicle.

[0008] Previously, the hub portion of the face portion of the composite wheel was formed using a layup of selected cut and shaped fibrous sheets or fabric pre- pegs or using cast, machined or hand shaped foam (polyurethane or other high density closed cell foam) inserts. Both methods have been found to not produce a dimensionally stable body when the part is molded and cured. Current foam inserts are not able to support and / or constrain the movement of the upper and lower fibrous layers during subsequent molding and during use loading once laminated between the fibrous layers. Additionally, it has been found that dry fibrous layer layup stacks can create manufacturing defects due to volume shrinkage resulting in surface finish defects and internal cracking.

[0009] Accordingly, it would be desirable to provide an improved or alternative shaped preform for use in forming the face portion of a composite wheel. SUMMARY

[0010] The present invention provides a layup aid for incorporation into the fibrous layup of the face portion of a composite wheel, preferably a carbon fiber wheel.

[0011] The present invention provides, in one aspect, a shaped preform component for the face portion of a composite wheel, the shaped preform having a hub extending about a central axis, the shaped preform component formed of a cured composite fibrous material having a compressibility of less than 2% by volume under molding conditions of a hydrostatic pressure of 50 bar and a temperature (process temperature) of 60°C to 200°C.

[0012] It should be understood that the term "composite material" herein denotes any type of composite material including cured or uncured fibers, regardless of whether the structure is layered or not. Further, cured or uncured preforms and pre-consolidated preforms are important subsets of composites and the main body.

[0013] It should also be understood that the term "cured" in "cured composite fibrous material" denotes that the composite fibrous material has undergone at least a partial curing process, thereby hardening, solidifying or setting the curable matrix material in the composite fibrous material.

[0014] Accordingly, the present invention provides a shaped preform that can be used in the layup and molding process for forming the face portion of a composite wheel and is designed to have minimal volume change. The use of the preform according to the present invention is intended to assist in the necessary construction of the face portion without requiring significant special considerations throughout the wheel molding process. The shaped preform provides a layup aid during the layup of the composite fibers and fabrics of the hub and face portion of the composite wheel.

[0015] The cured composite fiber material provides structural rigidity and / or solidity to the preform, which can be used to maintain the designed configuration of the preform into the shape and form of the entire composite wheel. Thus, the shaped preform has limited compressibility to enable providing the proper volume and minimal volume change during the layup and forming of the face portion of the composite wheel. Accordingly, the use of the shaped preform of the present application in the layup of the face portion of the composite wheel minimizes and more preferably avoids undesirable dimensional and volume changes that can damage the structure of the formed composite wheel. It should be appreciated that the compressibility of the shaped preform is measured as a percentage (%) by volume under forming conditions of hydrostatic pressure (e.g., during resin infusion) of 50 bar and process temperature range of 60°C to 200°C during a resin forming process such as a resin transfer molding (RTM) process.

[0016] The process temperature during the forming conditions can vary depending on the preferred infusion and curing temperatures. The preferred process temperature is about 120°C (typically 120°C + / - 3°C). However, the process temperature can range from 60°C to 180°C, preferably from 60°C to 150°C, more preferably from 60°C to 140°C. In embodiments, the process temperature is from 100°C to 200°C, preferably from 100°C to 150°C, more preferably from 100°C to 130°C. In embodiments, the process temperature is from 110°C to 150°C, preferably from 110°C to 130°C.

[0017] Further, (as explained in further detail below), the use of the cured composite fiber material enables the material to substantially match the composite fiber material used in the wheel, thus, imparting the preform with similar thermal and expansion characteristics as the surrounding composite layup material of the composite wheel.

[0018] The mechanical properties of the shaped preform of the present application can be tailored for the desired application. As noted above, the compressibility of the composite fiber body under forming conditions of hydrostatic pressure of 50 bar must be less than 2% by volume. In some embodiments, the compressibility of the shaped preform under forming conditions of hydrostatic pressure of 50 bar is less than 1.5% by volume, preferably less than 1% by volume. The process temperature of the forming conditions is the same as previously described.

[0019] Other mechanical properties of the shaped preform of interest include:

[0020] • Density - which is preferably between 600 kg / m 3 and 1300 kg / m 3 , and more preferably from 800 kg / m 3 to 1200 kg / m 3 . In some embodiments, the density of the shaped preform is from 500 kg / m 3to 1500 kg / m 3 In some embodiments, the density of the shaped preform is from 600 kg / m 3 to 1400 kg / m 3 In some embodiments, the density of the shaped preform is from 800 kg / m 3 to 1500 kg / m 3 .

[0021] • Tensile strength - which is preferably between 20 MPa and 80 MPa, more preferably from 20 MPa to 60 MPa. In some embodiments, the tensile strength is from 30 MPa to 80 MPa, preferably from 30 MPa to 60 MPa. In some embodiments, the tensile strength is from 20 MPa to 70 MPa, preferably from 40 MPa to 70 MPa.

[0022] • Stiffness - which is preferably from 1.5 GPa to 30 GPa, preferably from 5 GPa to 30 GPa, more preferably from 8 GPa to 30 GPa, yet more preferably 10 GPa to 25 GPa. In some embodiments, the stiffness is from 1.5 GPa to 10 GPa. In other embodiments, the stiffness is from 8 GPa to 25 GPa. In some embodiments, the stiffness is from 2 GPa to 30 GPa, preferably from 10 GPa to 25 GPa.

[0023] In some embodiments, the shaped preform has a stiffness of about 4 GPa and a tensile strength of about 50 MPa.

[0024] The surface of the shaped preform preferably has a rough surface with a roughness of at least Ra = 0.2 μιη. This surface roughness facilitates the bonding of the shaped preform to the surrounding material of the hub portion of the composite wheel when placed in the fiber layup of the hub portion. The rough surface can be formed by any suitable means. In some embodiments, the rough surface comprises a chemically etched surface, a mechanically abraded surface, or a specially textured surface.

[0025] The thermal expansion properties of the shaped preform are preferably designed to be similar, preferably substantially matched, to the thermal expansion properties of the overall composite material of the face portion of the composite wheel in which the shaped preform is configured to be included. Similar or substantially matched thermal expansion properties of the shaped preform and the surrounding material (typically a laminate) avoid material damage such as delamination at the surface of the shaped preform during the post-cure process. Thus, the thermal properties (and mechanical properties) of the shaped preform are matched to the surrounding wheel structure.

[0026] The shaped preform can be formed from any number of different materials, including a curable matrix material or can be constrained by a curable matrix material, such as a resin, to form a cured composite fiber material.

[0027] In some embodiments, the shaped preform is formed from resin (pure resin) or substantially only resin.

[0028] In some embodiments, the shaped preform is formed from at least one of: a custom fiber-implanted veil or preform; one or more layers of unidirectional fiber- oriented veils (unidirectional); one or more layers of multidirectional fiber veils (e.g., stitched non-crimp fabric); or a fiber patch-implanted (FPP) preform, such as CEVOTECH technology; a non-woven isotropic or anisotropic fiber layer, such as RECATEX regenerated carbon fiber non-woven; an isotropic fiber arrangement; a filler; glass microspheres; a hydrophobic fumed silica; an epoxy resin / curing agent; milled carbon fiber, chopped carbon fiber (e.g., shredded or cut carbon fiber), or combinations thereof.

[0029] In example embodiments, the shaped preform component is formed from:

[0030] (i) a mixture of resin, milled carbon fiber, and hollow glass microspheres;

[0031] (ii) a mixture of resin and milled carbon fiber;

[0032] (iii) a mixture of resin and chopped carbon fiber (preferably shredded carbon fiber); or

[0033] (iv) substantially only resin.

[0034] It will be appreciated that the resin further includes a content of hardener.

[0035] In some embodiments, the composition further includes 1 wt% (mass percent) to 5 wt%, preferably 1 wt% to 2 wt%, of hydrophobic fumed silica.

[0036] It will be appreciated that any suitable milled carbon fiber can be used. In some embodiments, the milled carbon fiber has a length of less than 500 pm, preferably less than 100 pm, more preferably between 50 pm and 200 pm. For example, milled carbon fiber having a length of 100 pm can be used, such as Carbiso TM MF. However, it will be appreciated that any brand of milled carbon fiber is suitable. Other fiber types of similar length can be used.

[0037] In other embodiments, comminuted carbon fibers, for example, chopped carbon fibers, can be used. The comminuted carbon fibers can have a length of less than 20 mm, preferably less than 15 mm, more preferably between 1 mm and 15 mm. For example, comminuted carbon fibers having a length of about 12 mm can be used. Other fiber types of similar length can be used.

[0038] The preferred material (Option A, B or C) is a mixture of resin and hardener, hollow glass microspheres, ground carbon fibers, and hydrophobic fumed silica in the following ratios (parts by mass):

[0039]

[0040] * 12 mm chopped carbon fibers

[0041] In an exemplary embodiment, the shaped preform component is formed from a material including a mixture of resin: ground carbon fibers: hollow glass microspheres in a ratio (parts by mass) of 3.75: 1 :0.56. In embodiments, the ratio (parts by mass) of resin: ground carbon fibers is from 2.5: 1 to 5: 1, preferably between 3: 1 and 4: 1. In embodiments, the ratio (parts by mass) of ground carbon fibers: hollow glass microspheres is from 1 :0.4 to 1 :0.7, preferably between 1 :0.5 and 1 :0.6.

[0042] Various suitable hollow glass microspheres can be used in the constituents of the shaped preform. The hollow glass microspheres preferably include hollow glass spheres having thin walls. The hollow glass microspheres can be formed from a variety of glass materials, including but not limited to Soda-lime-borate silicate glass. The softening temperature of the hollow glass microspheres is preferably at least 500°C, more preferably at least 600°C, and still more preferably about 600°C. The size of the hollow glass microspheres is preferably from 10 μιη to 200 μιη, more preferably from 18 μιη to 65 μιη. Further, the target crush strength (90% residual by volume) of the hollow glass microspheres is preferably from 250 psi to 28,000 psi, more preferably from 250 psi to 6,000 psi, and still more preferably from 250 psi to 3,000 psi. Additionally, the true density of the hollow glass microspheres is preferably 0.125 g / cc to 0.60 g / cc, more preferably from 0.125 g / cc to 0.4 g / cc, and still more preferably from 0.125 g / cc to 0.28 g / cc. In one exemplary embodiment, the hollow glass microspheres include 3M S28HS glass bubbles (available from 3M Advanced Material Division) having an average diameter of 30 μιη and a crush strength (90% residual by volume) of 3,000 psi and a true density of 0.28 g / cc. However, it should be appreciated that other similar microspheres can also be used. For example, alternative hollow microspheres such as 3M K1 bubbles having a target crush strength of 250 psi and a true density of 0.125 g / cc, or 3M IM30K (or similar) having a crush strength of 28,000 psi and a true density of 0.60 g / cc can be used.

[0043] In the case of using fiber-based materials, the shaped preform can be formed from at least one of the following: a fiber layer, a fiber ply, a prepreg, a semipreg, a woven or nonwoven fabric, a mat, a preform, a preconsolidated preform, individual or grouped fibers, a tow, a tow prep.

[0044] It should be understood that a prepreg refers to a collection of fibers, fiber tows, woven or nonwoven fabrics, etc. that are substantially or completely impregnated. Similarly, it should be understood that a semipreg refers to a collection of fibers or fiber tows that are partially impregnated. Partial impregnation provides for enhanced removal of gas through or along the dry fibers during consolidation and / or curing. An example of a semipreg is a partially impregnated fiber layer.

[0045] It should be understood that the woven or nonwoven fabric is a collection of individual fibers or fiber tows that are substantially dry (i.e., not impregnated with a matrix material such as a resin). It should also be understood that a fiber tow is a bundle of a large number of individual fibers (e.g., 1000, 10,000, or 100,000 fibers). A tow prep is a fiber tow that is at least partially impregnated.

[0046] A wide variety of fibers can be used in the present invention, including but not limited to fibers selected from the group consisting of carbon fibers, glass fibers, aramid fibers, synthetic fibers (such as acrylic, polyester, PAN, PET, PE, PP, or PBO fibers, etc.), biofibers (such as hemp, jute, cellulose fibers, etc.), mineral fibers (e.g., Rockwool, etc.), metal fibers (e.g., steel, aluminum, brass, copper, etc.), boron fibers, or any combination thereof. In preferred embodiments, the fibers include carbon fibers. The fibers can be provided in any desired orientation in the transition region, such as unidirectional, biaxial, or random, or a combination of these. However, the fibers are preferably oriented to reduce stresses between the composite members and to reinforce areas of the final structure that will experience higher stresses during use. The orientation of the fibers can be the same or can be different in all of the layers containing fibers within the transition region. For example, if a stress analysis suggests a multi-axial fiber orientation, one or more layers of fibers can be oriented in a different manner than the other layers. However, in other embodiments, the fibers can be oriented substantially the same in all of the fiber layers.

[0047] It should be appreciated that the shaped preform component should be formed from a material that ensures minimal volume change when used to form the face portion of the composite wheel. Where the material includes a fiber arrangement (e.g., an isotropic fiber arrangement), a fiber layer, a fiber ply, a prepreg, a semipreg, a woven or nonwoven fabric, a mat, a preform, a preconsolidated preform, individual or grouped fibers, a tow, or a tow prep, the material is preferably treated to provide the necessary compressibility, thereby providing minimal volume change in subsequent processing steps.

[0048] The method of forming a shaped preform generally involves the following general steps:

[0049] laying up or otherwise forming a shaped preform of the desired shape in a co- forming mold with a selected composite fiber material;

[0050] providing a matrix material in contact with the laid up material in the mold to form a body of introduced matrix material; and

[0051] curing the body of introduced matrix material.

[0052] The ply material is typically infused with a matrix material such that the matrix material penetrates through the material. Thus, the shaped preform typically further includes a curable matrix material that surrounds the constituent components of the shaped preform. Once molded and shaped into the shaped preform, the shaped preform includes a matrix material that binds the fibers together with the other constituent materials. During the layup (up to the point of consolidation and / or setting, curing, etc. of the matrix material), it is not necessary to include matrix material in the layers that include fibers (e.g., prepreg or semipreg) or between layers that include fibers. However, the matrix material should form a continuous matrix prior to setting occurs. Suitable matrix materials can be selected from, but are not limited to, resins based on unsaturated polyesters, polyurethanes, polyvinyl esters, epoxy resins, thermoplastics, or combinations thereof.

[0053] It will be appreciated that the curing step can be controlled to provide desired mechanical properties, including stiffness and compressibility. The mechanical properties of the shaped preform can be designed to suit a particular application. These properties can be varied by selecting the constituent materials that form the shaped preform, the matrix material, the amount of matrix material infused or included therein, and the curing regime (curing time, temperature, whether the body is fully cured). In some cases, it is desirable to stop the curing process prior to the shaped preform being fully cured in order to produce surface properties that facilitate the adhesion of subsequent ply materials when used in the layup of the face portion of a composite wheel.

[0054] Advantageously, the surface of the shaped preform is preferably designed to adhere to the remainder of the structure used to form the composite wheel. In embodiments, the surface of the shaped preform is configured to facilitate the adhesion of carbon fibers or carbon fiber- containing materials. As noted above, the surface of the shaped preform preferably has a rough surface with a roughness of at least Ra = 0.2 pm. The rough surface can be formed by any suitable means. In some embodiments, the rough surface includes a chemically etched surface, a mechanically abraded surface, or a mechanically featured surface.

[0055] The surface properties of the shaped preform can be modified by varying the curing properties and regime of the shaped preform. In some embodiments, the shaped preform includes an incomplete or incompletely cured preform. However, it will also be appreciated that the shaped preform is cured and otherwise processed to provide a selected compressibility that can provide minimal volume change in subsequent fiber layup and molding processing steps.

[0056] The shaped preform is generally formed with a designed shape and geometry that provides a basis for the geometry, in some cases a complex geometry, of the face portion (hub and spokes) of the desired composite wheel to be formed. As can be appreciated, a number of features are required to be included in the face portion, and in particular the hub, to meet the functional requirements of attaching the composite wheel to the wheel mount of the wheel, and including branding or other indicia. For example, the hub preferably includes at least one hole. The hole can be used to receive a wheel bolt or center locking bolt or a branding or indicia button, insert or cap. Any number of holes can be included in the hub. In embodiments, the hub includes at least three holes spaced about a central axis, preferably at least four holes spaced about a central axis, preferably at least five holes. In some embodiments, the hub includes a central hole. The central hole can have a smooth inner wall, or in preferred embodiments, where a body such as a cap or plug is to be retained, the central hole can include a step forming a rim or flange at one end of the hole. The rim or flange forms a stop to prevent the cap or plug from passing through the hole.

[0057] The hub can have any suitable configuration. In embodiments, the hub is generally circular in shape about a central axis. However, it should be appreciated that the hub can have any number of other shapes, in particular regular polygonal shapes, including square, pentagonal, hexagonal, octagonal, etc. In some embodiments, the hub includes a first side having a generally planar surface and a second side opposite the first side having a generally concave or recessed surface.

[0058] In preferred embodiments, the shaped preform includes a plurality of fingers spaced annularly about the central axis and extending radially outwardly away from the central axis from the periphery of the hub. The function of the fingers is to provide a connection member that joins the spokes of the face portion to the hub thereof. Thus, the number of fingers preferably corresponds to the number of spokes formed in the face portion of the composite wheel. The fingers can similarly have any suitable configuration. In some embodiments, the fingers include tapered projections extending outwardly from the periphery of the hub. Each finger is preferably equally spaced about the central axis from each other. Each finger preferably has a curved portion between each adjacent finger. In some embodiments, the fingers include a surface sloping downwardly from the periphery of the planar surface of the hub towards the distal end of the respective finger.

[0059] The shaped preform can additionally include a number of features designed to facilitate the subsequent formation and layup of the face portion of the composite wheel. These features include, but are not limited to:

[0060] Fiber ply retention structures;

[0061] Guidelines visually indicating where the edges of the plies should be located; or

[0062] A holding / manipulating structure for optimizing the handling of a shaped preform.

[0063] The invention provides in a second aspect a method of forming a face portion of a composite wheel, comprising:

[0064] positioning the shaped preform according to any of the preceding claims in a hub portion of a fibre lay-up of the face portion of the composite wheel; and

[0065] laying up a fibre element around the shaped preform, thereby forming a preform structure of the face portion of the composite wheel.

[0066] Preferably, the shaped preform, the fibres of the fibre lay-up of the face portion and the fibre element are infused and / or impregnated with a matrix material, and then cured, solidified, etc. Thus, the face portion preferably further comprises a matrix material surrounding the fibre lay-up and containing the fibres and the fibre element. Any suitable matrix material can be used. In some embodiments, a resin is used. The resin is preferably based on unsaturated polyester, polyurethane, polyvinyl ester, epoxy, thermoplastic, similar compounds or combinations thereof. In preferred embodiments, the resin is epoxy based. In other embodiments, the matrix material comprises a metal matrix which, upon solidification, forms a composite metal matrix with the fibres. The metal matrix material is preferably selected from the group consisting of aluminium, magnesium, titanium, iron and combinations, alloys and mixtures thereof. Once shaped and formed into a composite wheel, the face portion comprises a matrix material such as resin, metal and fibres.

[0067] The fibre lay-up of the face portion is preferably infused and / or impregnated with a curable matrix material, and then cured and / or solidified. Thus, the method preferably further comprises the steps of:

[0068] providing a matrix material in contact with the preform structure of the face portion; and

[0069] curing the face portion.

[0070] Preferably, the surface of the shaped preform is activated to enable the surface to bond with the surrounding material when the matrix material is infused and / or impregnated. Activation is typically a surface marking process, for example, this can be achieved by chemical etching, mechanical abrasion, etc.

[0071] The shaped preform is preferably integrally formed with the composite wheel. Furthermore, the composite wheel is preferably formed as an integral body. This typically involves simultaneous infusion and / or impregnation of the matrix material, and then curing, solidification, etc. of each portion of the composite wheel. In such embodiments, each of the rim portion and the face portion is preferably at least not fully cured when the preparation of the connection portion is made. The connection portion is preferably integrally formed with the composite wheel. In such embodiments, the method further comprises the steps of:

[0072] simultaneously with each of the rim portion and the face portion of the wheel; and

[0073] simultaneously curing the rim portion and the face portion of the wheel.

[0074] It will be appreciated that curing of the matrix material and associated parts, such as the face portion, the rim portion, the one-piece composite wheel, or the like, includes curing, solidifying, drying, or the like.

[0075] In the event that the matrix material comprises a resin, a variety of resin delivery systems can be used with the method of the second aspect. In some embodiments, at least a portion of the resin is provided by resin infusion and / or resin transfer molding and / or vacuum assisted resin transfer molding.

[0076] The fibers and fiber elements of the fiber layup of the face portion of the composite wheel preferably comprise carbon fibers. However, it will also be appreciated that a wide variety of fibers can be used in the present invention, including but not limited to fibers selected from the group consisting of carbon fibers, glass fibers, aramid fibers, synthetic fibers (such as acrylic, polyester, PAN, PET, PE, PP, or PBO fibers, etc.), biofibers (such as hemp, jute, cellulose fibers, etc.), mineral fibers (e.g., rock wool, etc.), metal fibers (e.g., steel, aluminum, brass, copper, etc.), boron fibers, or any combination thereof. In preferred embodiments, the fibers comprise carbon fibers. The fibers can be provided in any desired orientation in the transition region, such as unidirectional, biaxial, or random, or a combination of these. However, the fibers are preferably oriented to reduce stresses between the composite components and to reinforce areas of the final structure that will experience higher stresses during use. The orientation of the fibers can be the same or can be different in all of the layers containing fibers within the transition region. For example, if a stress analysis suggests a multi-axial fiber orientation, one or more layers of fibers can be oriented in a different manner than the other layers. However, in other embodiments, the fibers can be oriented substantially the same way in all of the fiber layers.

[0077] The fiber elements can be provided in any suitable form, including prepreg, semipreg, woven or non-woven fabric, mat, preform, pre-consolidated preform, individual or grouped fibers, tows, towpreg, etc. In embodiments, the fiber elements are provided as at least one fabric sheet, preferably a multi-axial fabric. It is not necessary for the layers comprising fibers (e.g., prepreg or semipreg) to contain matrix material during the layup of the connection (up to the point in time prior to consolidation and / or solidification, curing, etc. of the matrix material). However, the matrix material should form a continuous matrix prior to solidification occurring.

[0078] A face portion can be formed from a custom fiber preform having a desired shape and fiber orientation including the shaped preform of the present application. The custom fiber preform is formed to have a desired shape and fiber orientation. It should be understood that the preform is a composite material including fibers. In some cases, the preform can also include an uncured matrix material such as a resin. Some preforms can include substantially dry fibers without a matrix material. Adhesives can be used to help hold the plies together prior to infusion of the matrix material.

[0079] A third aspect of the present application provides a composite wheel including a shaped preform according to the first aspect of the present application. In some embodiments, the composite wheel is formed about a central wheel axis. BRIEF DESCRIPTION OF DRAWINGS

[0080] The present application will now be described with reference to the drawings, which illustrate particular preferred embodiments of the application, in which:

[0081] Figure 1 is a perspective view of a composite wheel including a connection between its face portion and rim portion according to an embodiment of the present application.

[0082] Figure 2 is a perspective view of a composite wheel including a connection between its face portion and rim portion according to an embodiment of the present application. Figure 1 is a more detailed view of the rim-to-face connection area of the composite wheel shown.

[0083] Figure 2A A cross-sectional view of a center-locked composite wheel construction is provided.

[0084] Figure 3 An isometric top view of a shaped preform according to an embodiment of the present application is provided.

[0085] Figure 4 An isometric top view of a shaped preform according to an embodiment of the present application is provided. Figure 3 is a side cross-sectional view of the shaped preform shown.

[0086] Figure 5 A schematic diagram is provided showing the stresses that form a curved beam due to an applied force.

[0087] Figure 6 A schematic diagram is provided showing a core-hollowed body.

[0088] Figure 7 A schematic diagram is provided showing a core-filled body (including a shaped preform). DETAILED DESCRIPTION

[0089] Referring first to Figure 1Fig. 1 shows a perspective view of a composite wheel 100 which has been formed and integrally comprises a shaped preform 200 of the present application. The applicant of the present application has developed the composite wheel 100 shown as a composite wheel formed as a one-piece body. The general process of manufacturing the composite wheel 100 is described in International Patent Publication WO 2010 / 024495 Al, the contents of which should be understood to be incorporated herein by this reference.

[0090] The composite wheel 100 shown comprises two main parts:

[0091] A) a rim portion 102 comprising an annular structure onto which a tyre (not shown) is mounted; and

[0092] B) a face portion 104 comprising a circular hub 106 and a series of spokes 108. The hub 106 comprises five fastening holes 107 Figure 1 and Figure 2 shown in place with fastening bolts 107A) configured to receive fastening bolts (not shown) for securing the wheel to a vehicle wheel carrier (not shown). The spokes 108 comprise elongate arms connected at one end to the hub 106 and at the other end to the rim portion 102.

[0093] It will be appreciated that other composite wheel configurations are possible, for example, a centre lock composite wheel 100A having a face portion 104A comprising a hub 106A having a centre lock hole 107A configured to receive a centre lock fastening bolt (not shown) for securing the wheel to a centre lock wheel carrier of a vehicle (not shown).

[0094] As described in International Patent Publication WO 2010 / 024495 Al, the manufacture of such a one-piece composite wheel 100 requires the use of a separate rim portion mould (not shown) and a face portion mould (not shown). In use, the rim portion 102 is formed by laying down a first set of fibres (typically embodied as a reinforcing fabric placed in the rim portion mould) and the face portion 104 is formed by separately laying down a second set of fibres (typically embodied as a reinforcing fabric placed in the face portion mould). The rim portion mould comprises an inner barrel mould and an outer cylindrical mould. The reinforcing fabrics from the rim portion mould and the face portion mould are then assembled together in a combined mould in the state of the separate portions being interconnected at the connection point 110. A final forming process is then carried out in which a matrix material such as a resin is injected and / or infused into the reinforcing in the form of the whole wheel to produce the formed one-piece wheel 100.

[0095] The shape and configuration of the face portion 104, particularly the hub 106, can be formed from the layup in the face portion mold. However, in the case of the present application, by using a shaped preform 200 Figure 3 and Figure 4 ) that can be positioned in place in the mold and forming the layup around the shaped preform 200, it can be helpful in forming the features in the layup.

[0096] Figure 3 and Figure 4 One example of a shaped preform insert 200 for layup and forming of a face portion 104 of a composite wheel 100, such as shown in Figure 1 and Figure 2 is shown. The shown shaped preform 200 is used to provide the shape and configuration of the hub 106 of the face portion 104 and the connection of the hub 106 to the spokes 108. Thus, the shown shaped preform has a circular hub portion 206 extending about a central axis Y-Y, and a spoke connection portion 208 including a plurality of fingers 209 spaced annularly about the central axis Y-Y and extending radially outwardly away from the central axis Y-Y from a periphery of the hub portion 2016. It should be appreciated that as an alternative, the shaped preform can be configured to provide the shape and configuration required for the center lock wheel 100A shown in Figure 2A .

[0097] The exact geometry of the hub portion 206 and the spoke connection portion 208 depends on the intended configuration of the composite wheel 200. For example, the number of spokes 108 can vary, affecting the configuration of the spoke connection portion 208. In addition, the type of wheel mount fitting can vary depending on the functional requirements for attaching the composite wheel 100 to a vehicle wheel mount, and including branding or other indicia in the wheel configuration. For example, a center lock wheel mount will have a different configuration than a bolt-on wheel mount. The number and configuration of wheel bolts can also vary. In the shown embodiment, the hub portion 206 includes five holes 207 spaced about the central axis Y-Y for forming fastener holes 107 Figure 1 and Figure 2 , and a central hole 211. The central hole 211 includes a step 212 forming a rim or flange that provides a stop that can be used to retain and prevent a cap or plug from passing through the central hole 211. The hub includes a first side 220 having a generally planar surface that forms the rear side of the hub 106 in the composite wheel 100, and a second, concave or recessed side 222 that forms the features of the front side of the hub 106 in the composite wheel 100.

[0098] The spoke connecting portion 208 includes ten annularly spaced apart fingers 209. The function of the fingers 209 is to provide a connecting member that links the spokes of the face portion to the hub thereof. The number of fingers 209 corresponds to the number of spokes formed in the face portion 104 of the composite wheel 100. As shown, the fingers 209 include tapered projections that extend outwardly from the perimeter of the hub portion 206. As shown on the first side 220, the fingers 209 are downwardly angled from the perimeter of the planar surface of the hub portion 206 toward the distal end of each finger 209. A similar angle is provided on the second side 222 away from the perimeter of the concave surface of the hub portion 206. Each finger 209 is separated by an arcuate recess about the axis Y-Y. Figure 3

[0099] While not shown, the shaped preform 206 can be shaped / configured to include a plurality of additional features designed to aid in the subsequent forming and layup of the face portion of the composite wheel. These features include, but are not limited to, fiber ply retention structures such as steps, recesses, slots, etc.; guide lines to visually indicate where the edges of the plies should be located; or retention / manipulation structures such as recesses, flanges, holes, ribs, hooks, projections, etc. to optimize handling of the shaped preform.

[0100] The shaped preform 200 is formed from a cured composite fiber material having a compressibility of less than 2% by volume, preferably less than 1%, under forming conditions of hydrostatic pressure of 50 bar, process temperature of 60°C to 200°C, preferably 60°C to 150°C, more preferably 60°C to 140°C. By cured, it is understood that the cured composite fiber material has undergone at least a partial curing process to harden or cure the curable matrix material, such as resin, in the composite fiber material. The cured composite fiber material provides structural rigidity and / or robustness to the preform, thereby providing limited compressibility to enable proper and minimal volume changes during layup and forming of the face portion of the composite wheel.

[0101] While not wishing to be bound by any one theory, the shaped preform 200 is designed to provide a core material (see Figure 7 ) that can be used in the layup and curing process of the composite wheel 100 to provide an alternate load path for forces in the structure of the hub portion 206. The mechanical and material properties of the shaped preform are also selected to minimize structural loading and stresses due to material incompatibility and volume changes during layup, curing, and post-curing processes when forming the composite wheel.

[0102] The beam (e.g., Figure 5 ​The flanges 305 of the beam 300 carry bending due to tensile and opposite compressive stresses in the members of the beam 300 that are away from the neutral axis of the beam 300 (the flanges 305). When the beam 300 has a bending region, these tensile and compressive stresses along the axis of the beam 300 in turn create through thickness stresses that are tensile or compressive depending on the loading direction (bending moment M), as shown in Figure 5 .

[0103] The beam 350 with a hollow or soft core configuration has similar behavior to the beam 300, where the sum of the through thickness tensile stresses creates forces that have a tendency to separate the outer flanges 355 from the rest of the body 350. These forces can create stresses in the connections 362 between the flanges 355 and the sidewalls 360 of the body 350, which can be a limiting factor in the bending strength of the body 350, as shown in Figure 6 . This limitation is particularly evident for composites where the strength in the axial direction can be significantly less than the strength in the thickness direction. The degree of the limitation depends significantly on the cross-sectional proportions of the body. The greater the width of the body compared to its height, the greater the forces that tend to separate the flanges from the sidewalls.

[0104] The present invention seeks to address this limitation by adding an appropriate core 382 inside the body 380 (i.e., the shaped preform 200). The purpose of the core 382 is to provide an alternative load path for the forces that seek to separate the flanges 385 of the body 380 from the rest of the body. A portion of this separation force can be directly transferred to the core as a tensile stress (e.g., as a tension 393 between the flanges and the core), which partially unloads the connections 392 between the flanges 385 and the sidewalls 390. By partially unloading the connections 392 between the flanges and the sidewalls, the strength of the body 380 is increased and thus the load capacity is increased, as shown in Figure 7 .

[0105] The mechanical properties of the shaped preform 200 are designed to achieve the best mechanical and material performance. A shaped preform 200 that does not have enough tensile modulus in the thickness direction of the body will not effectively unload the connections between the flanges and the sidewalls, and thus has little structural value. A shaped preform 200 that has too much tensile modulus in the thickness direction of the body will cause excessive through thickness stresses in the flanges when the flanges seek to separate from the shaped preform 200, and cause failure either within the flanges themselves or at the connections between the flanges and the shaped preform 200. A properly designed shaped preform 200 will unload the connections between the flanges and the sidewalls without creating excessive through thickness stresses in the flanges.

[0106] Any number of different composite fibre materials can be used, which include a curable matrix material or can be constrained by a curable matrix material, such as a resin, to form a cured composite fibre material. In some embodiments, the shaped preform is formed from, or is substantially formed from, resin (neat resin). In embodiments, the shaped preform is formed from at least one of: a custom fibre implant veil or preform; one or more layers of unidirectional fibre veils (unidirectional); one or more layers of multidirectional fibre veils (e.g. stitched non-crimp fabric); or a fibre patch placement (FPP) preform, such as the CEVOTECH technology; a non-woven isotropic or anisotropic fibre layer, such as the RECATEX recycled carbon fibre non-woven; an isotropic fibre array; a filler; glass microspheres; a hydrophobic fumed silica; an epoxy resin / curing agent; milled carbon fibre, or a combination thereof.

[0107] In preferred forms, the shaped preform component is formed from:

[0108] (i) a mixture of resin, milled carbon fibre and hollow glass microspheres.

[0109] (ii) a mixture of resin and milled carbon fibre.

[0110] (iii) a mixture of resin and comminuted carbon fibre.

[0111] Each of (i) and (ii) can optionally include 1 wt% to 5 wt%, preferably 1 wt% to 2 wt%, of hydrophobic fumed silica. It will be appreciated that the resin in the above preferred forms also includes an amount of hardener.

[0112] In some embodiments, the milled carbon fibre has a length of less than 500 pm, preferably less than 100 pm. For example, milled carbon fibre of 100 pm in length can be used, such as Carbiso TM MF. However, it will be appreciated that milled carbon fibre of any brand is suitable. Other fibre types of similar length can be used.

[0113] In embodiments, the comminuted carbon fibre includes chopped carbon fibre having a length of less than 20 mm, preferably less than 15 mm (e.g. between 1 mm and 15 mm). In particular embodiments, comminuted carbon fibre of about 12 mm in length can be used.

[0114] A preferred material (the units of the ratios are mass parts) is provided below in Table 1 as Option A and Option B:

[0115] Table 1 : Exemplary shaped preform ingredients

[0116]

[0117] In more detail, Option C can include:

[0118] 3.75 parts of epoxy resin;

[0119] 1 part of 100 pm length milled carbon fiber; and

[0120] 0.5 parts of hollow glass microspheres.

[0121] In more detail, Option D can include:

[0122] 3 parts of epoxy resin and hardener; and

[0123] 1 part of 12 mm length chopped carbon fiber.

[0124] The microspheres include 3M S28HS glass bubbles available from 3M Advanced Material Division. These glass bubbles include hollow spheres with thin walls having an average diameter of 30 pm, a crush strength (90% residual by volume) of 3000 psi, and a true density of 0.28 g / cc made from a soda-lime-borate silicate glass. However, it should be appreciated that other similar microspheres can also be used. For example, alternative hollow microspheres such as 3M K1 bubbles having a target crush strength of 250 psi and a true density of 0.125 g / cc, or 3M IM30K (or similar) having a crush strength of 28000 psi and a true density of 0.60 g / cc can be used. Options for possible 3M microspheres that can be used are provided in Table 2:

[0125] Table 2: 3M Hollow Glass Microspheres (Glass Bubbles) that can also be used by the present invention:

[0126]

[0127] It should be appreciated that alternative mixing ratios to those provided in Options A and B above can also provide satisfactory compositions.

[0128] In an exemplary embodiment, the shaped preform component is formed from a mixture having a resin:milled carbon fiber:hollow glass microspheres ratio (parts by mass) of 3.75:1:0.56.

[0129] In the illustrated embodiment, the fibers in the cured composite fiber material of the composite wheel 100 include carbon fibers. However, it should be appreciated that a wide variety of fibers can be used in the present application, including but not limited to fibers selected from the group consisting of carbon fibers, glass fibers, aramid fibers, synthetic fibers (such as acrylic, polyester, PAN, PET, PE, PP, or PBO fibers, etc.), biofibers (such as hemp, jute, cellulose fibers, etc.), mineral fibers (e.g., rock wool, etc.), metal fibers (e.g., steel, aluminum, brass, copper, etc.), boron fibers, or any combination thereof.

[0130] It should be appreciated that the thermal expansion properties of the shaped preform 200 are designed to be similar to and preferably substantially match the thermal properties of the overall composite material of the face portion of the composite wheel (into which the shaped preform 200 is configured to be included). By matching the thermal expansion properties, damage such as delamination of the parts (the shaped preform and surrounding laminate material during curing) is avoided.

[0131] The composite material (typically a carbon fiber laminate) formed adjacent to the shaped preform in the molding process must be adhered to the shaped preform. The shaped preform material type must be able to accomplish this, for example, the shaped preform can use an epoxy resin, but typically should not use polypropylene. After molding of the shaped preform, and prior to the layup of the shaped preform, the surface of the shaped preform must be activated to enable it to be combined with the subsequent infusion operation (which can be accomplished by chemical etching, mechanical abrasion, etc.).

[0132] Other mechanical properties of the shaped preform 200 of interest include:

[0133] • Density - which is preferably between 600 kg / m 3 and 1300 kg / m 3 , and more preferably from 800 kg / m 3 to 1200 kg / m 3 ;

[0134] • Tensile strength - which is preferably between 20 MPa and 80 MPa, more preferably from 20 MPa to 60 MPa;

[0135] • Stiffness - which is preferably from 1.5 GPa to 30 GPa, more preferably from 10 GPa to 25 GPa. In some embodiments, the stiffness is from 1.5 GPa to 10 GPa. In other embodiments, the stiffness is from 8 GPa to 30 GPa.

[0136] In some embodiments, the shaped preform has a stiffness of about 4 GPa and a tensile strength of about 50 MPa. However, it should be appreciated that these properties can vary depending on the material of the particular composite wheel, the wheel construction, and the desired properties.

[0137] The illustrated shaped preform 200 is formed by a standard composite molding process. In this process, the preferred material constituents described in Table 1 are metered and mixed, and then injected into a closed heated mold. The mold is at 120°C and once filled, the mold is held at 120°C for 10 minutes to allow the resin to cure. The puck is then de-molded and moved to the surface preparation step. The co-molded mold has a mold cavity shaped to provide the desired shape and construction of the shaped preform 200. Suitable matrix materials can be selected from, but are not limited to, resins based on unsaturated polyesters, polyurethanes, polyvinyl esters, epoxy resins, thermoplastics, and combinations thereof.

[0138] The curing step can be controlled to provide desired mechanical properties, including stiffness, surface properties, and compressibility. Thus, the mechanical properties of the shaped preform 200 can be designed to suit a particular application. However, it must be appreciated that the shaped preform 200 is cured and otherwise treated to provide a selected compressibility that provides minimal volume change in the subsequent fiber layup of the face portion 104 step of the molding process step of forming the composite wheel 200.

[0139] As described above, the cured shaped preform 200 is used as a layup aid or insert in the layup of the face portion 104 of the composite wheel 100. In this process, the shaped preform 200 is positioned in the hub portion of the fiber layup of the face portion mold; and the composite fiber elements of the face portion 104 are laid up around the shaped preform 200, thereby forming a preformed structure of the face portion of the composite fiber wheel.

[0140] Likewise, the fiber elements of the face portion layup can be provided in any suitable form, including prepreg, semipreg, woven or non-woven fabric, mat, preform, preconsolidated preform, individual or grouped fibers, tows, tow prep, etc. It is not required that a matrix material such as a resin be included in or between the layers comprising fibers during the layup. However, the matrix material should form a continuous matrix after curing.

[0141] The illustrated composite wheel 100( Figure 1 and Figure 2) intended to be formed as a unitary body. This involves simultaneously injecting and / or impregnating a matrix material (in the exemplary embodiment, a resin) into all of the parts comprising the rim portion 102 and the face portion 104, and then curing each portion of the composite wheel 100. The resin used is preferably epoxy-based. However, it should be appreciated that any suitable resin can be used, such as, for example, unsaturated polyester, polyurethane, polyvinyl ester, epoxy, thermoplastic, similar compounds, or combinations thereof. A variety of resin delivery systems can be used, including but not limited to resin infusion and / or resin transfer molding and / or vacuum assisted resin transfer molding.

[0142] In constructing the composite wheel shown in Figure 1 and Figure 2 The wheel comprises three main mold faces. First is a face mold oriented generally radially with respect to the rotational axis X-X of the wheel. Second is an inner barrel-shaped mold face forming the inner side 140( Figure 2 ) of the wheel. The inner barrel-shaped mold face comprises a front face forming a rear mold wall of the face portion oriented radially with respect to the rotational axis X-X of the wheel, and a sidewall forming a rear mold wall of the rim portion in axial alignment with the rotational axis X-X of the wheel. Third is a rim mold substantially axially aligned with the rotational axis X-X of the wheel.

[0143] In use, the rim portion 102 and the face portion 104 are laid up with reinforcement, and then the connection between the rim portion 102 and the face portion 104 is laid up with reinforcement. After the connection is formed, resin is injected and / or impregnated into the reinforcement of each of the rim portion 102, the face portion 104 of the wheel 100, and then cured.

[0144] Those skilled in the art will appreciate that the application described herein is susceptible to variations and modifications other than those specifically described. It is to be understood that the application includes all such variations and modifications which fall within the spirit and scope of the present application.

[0145] The terms "comprise", "comprising", "include", "including", "comprises" or "comprising" when used in this specification and including the claims are not to be interpreted in an exclusive or exhaustive sense.

Claims

1. A carbon fiber wheel comprising a shaped preform, the shaped preform comprising a shaped preform component for a face portion of the carbon fiber wheel, the face portion comprising a circular hub portion and a series of spokes, the shaped preform having a hub extending around a central axis and located in the circular hub portion of the face portion, the hub being circular around the central axis, the shaped preform component being formed from a cured composite fiber material having a compressibility of less than 2% by volume under forming conditions of hydrostatic pressure of 50 bar and temperature of 60°C to 200°C, And wherein, the shaped preform being formed from: (i) a mixture of a resin, milled carbon fibers, and hollow glass microspheres; (ii) a mixture of a resin and milled carbon fibers; (iii) a mixture of a resin and pulverized carbon fibers.

2. The carbon fiber wheel of claim 1, wherein, the shaped preform component further comprising a plurality of fingers spaced annularly around the central axis and extending radially outwardly away from the central axis from a periphery of the hub.

3. The carbon fiber wheel of claim 1, wherein, the compressibility of the shaped preform under forming conditions of hydrostatic pressure of 50 bar is less than 1% by volume.

4. The carbon fiber wheel of claim 1, wherein, The density of the shaped preform is between 600 and 1300 kg / m 3 3 ​​ 5. The carbon fiber wheel of claim 1, wherein, the shaped preform having: • a tensile strength between 20 MPa and 80 MPa; and / or • a stiffness from 1.5 GPa to 30 GPa.

6. The carbon fiber wheel of any one of claims 1-5, wherein, a surface of the shaped preform has a rough surface having a roughness of at least Ra = 0.2 pm.

7. The carbon fiber wheel of claim 6, wherein, the rough surface comprises a chemically etched surface or a mechanically abraded surface.

8. The carbon fiber wheel of any one of claims 1-5, wherein, the shaped preform further comprising 1 wt% to 5 wt% of a hydrophobic fumed silica.

9. The carbon fiber wheel of any one of claims 1-5, wherein, the milled carbon fibers have a length of: between 1 mm and 15 mm; or between 50 pm and 200 pm.

10. The carbon fiber wheel of any one of claims 1 to 5, further comprising a curable matrix material surrounding the constituent components of the shaped preform.

11. The carbon fiber wheel of claim 10, wherein, the matrix material comprises a resin based on unsaturated polyesters, polyurethanes, epoxy resins, thermoplastics, and combinations thereof.

12. The carbon fiber wheel of claim 11, wherein, the thermoplastic is a polyvinyl ester.

13. The carbon fiber wheel of any one of claims 1-5, wherein, the shaped preform comprises an incomplete or incompletely cured preform.

14. The carbon fiber wheel of any one of claims 1-5, wherein, the hub comprises one or more holes.

15. The carbon fiber wheel of any one of claims 1-5, wherein, the hub comprises three or more holes spaced around the central axis.

16. The carbon fiber wheel of any one of claims 1-5, wherein, the hub comprises a central hole.

17. The carbon fiber wheel of claim 16, wherein, the central hole comprises a step forming a rim or flange at one end of the central hole.

18. The carbon fiber wheel of any one of claims 1-5, wherein, the hub comprises a first side having a planar surface and a second side opposite the first side having a concave or recessed surface.

19. The carbon fiber wheel of claim 2, wherein, the fingers comprise a surface that tapers or slopes downwardly from a periphery of the planar surface of the hub toward a distal end of each finger.

20. The carbon fiber wheel of claim 2, wherein, the number of fingers corresponds to the number of spokes formed in the face portion of the carbon fiber wheel.

21. The carbon fiber wheel of claim 2, wherein, the fingers are equally spaced around the central axis.

22. The carbon fiber wheel of any one of claims 1 to 5, comprising one or more of the following features: a fiber ply retention structure; a guide line visually indicating where the edge of a ply should be located; or A holding / manipulating structure for optimizing the processing of the shaped preform.

23. The carbon fiber wheel of any one of claims 1-5, wherein, The shaped preform is integrally formed with the carbon fiber wheel.

24. A method of forming a face portion of a carbon fiber wheel, comprising: positioning a shaped preform in a hub portion of a fiber layup of a face portion of a carbon fiber wheel, the shaped preform having a hub extending about a central axis, the shaped preform component being formed of a cured composite fiber material having a compressibility of less than 2% by volume under molding conditions of a hydrostatic pressure of 50 bar and a temperature of 60°C to 200°C, wherein the shaped preform is formed of: (i) a mixture of a resin, milled carbon fibers, and hollow glass microspheres; (ii) a mixture of a resin and milled carbon fibers; (iii) a mixture of a resin and pulverized carbon fibers; and laying up composite fiber elements about the shaped preform, thereby forming a preform structure of a face portion of a carbon fiber wheel.

25. The method of claim 24, further comprising the steps of: providing a matrix material in contact with the preform structure of the face portion; and curing the face portion.

26. The method of claim 24, wherein, The method further comprises the steps of: simultaneously providing a matrix material in contact with each of a rim portion and a face portion of the carbon fiber wheel; and simultaneously curing the rim portion and the face portion of the carbon fiber wheel.

27. The method of any one of claims 24-26, wherein, The fiber elements of the fiber layup of the face portion of the carbon fiber wheel comprise carbon fibers.

28. The method of any one of claims 24 to 26, wherein, The fiber elements are provided as prepreg, semipreg, woven or nonwoven fabric, mat, preform, individual or grouped fibers, tows, towpreg, or combinations thereof.

29. The method of claim 28, wherein, The preform is a preconsolidated preform.

30. The method of any one of claims 24 to 26, wherein, The fiber elements are provided as one or more fabric plies.

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