Method for producing a fiber composite material

Abstract

The present invention provides a prepreg, a carbon fiber reinforced composite material and a method for producing a prepreg, the method comprising the following steps: (a) providing a fast curing resin composition; (b) forming a film of the resin from step (a) on one side surface of a release substrate sheet; (c) providing a fiber fabric substrate sheet having a cross-sectional thickness in which the fiber unit area weight changes; (d) contacting at least one side surface of the fiber fabric substrate sheet of step (c) with the film of step (b); (e) applying pressure on the other side surface of the release substrate sheet opposite to the resin film of step (b) to impregnate the fiber fabric substrate sheet of step (c) with the resin composition of step (a); and (f) allowing the fiber fabric substrate sheet impregnated with the resin composition of step (e) to partially cure to form a prepreg product. Also provided is an S-shaped winding pressure roller assembly having at least three rollers, wherein the second roller positioned between the other two rollers has an improved diameter.

Description

Technical Field

[0001] The present invention relates to a method for producing a fiber composite material; and more particularly, the present invention relates to a method for preparing a carbon fiber epoxy resin composite material having a varying fiber areal weight. Background Art

[0002] Generally, it is known to produce carbon fiber composites by first impregnating fibers or fabrics with a resin formulation (e.g., an epoxy resin formulation) to form a prepreg structure, and then curing the impregnated prepreg structure to form a carbon fiber composite. Carbon fiber epoxy composites can be used in many applications, including, for example, the manufacture of automotive parts. In automotive applications, it is necessary to produce a carbon fiber epoxy composite having a continuous aligned fabric that can have a fiber area weight (FAW) that varies across the width of the fabric. In order to be used in automotive applications, the impregnated fibers or fabrics need to: (1) be compression molded and cured in less than 5 minutes (min), (2) maintain a high glass transition temperature, and (3) achieve high strength and stiffness properties using an internal release agent to allow the cured part to be easily demolded from the mold.

[0003] To date, impregnation methods for impregnating fabrics, such as the methods disclosed in EP2692783B1 and EP3216496A1, have been performed on prepregs having a uniform FAW, and the known methods assume that the reinforcing layers of the prepreg have a single thickness. Problems arise when using known impregnation methods to impregnate resin into fabrics having varying fiber weights per unit area (varying thicknesses) (i.e., fabrics having high weight per unit area portions and low weight per unit area portions). For example, when known impregnation methods are used for fabrics having varying fiber weight per unit area, the high weight per unit area portions of the fabric become deformed, or the low weight per unit area portions of the fabric are not infused with resin. Typically, a fabric having a variable carbon fiber weight per unit area woven structure has a high fiber weight per unit area (e.g., 588 g / m2) in the center of the fabric. 2 )) and has a low fiber basis weight (e.g., 520 g / m 2 ).

[0004] It would be desirable to provide a method or process for impregnating a carbon fabric with an epoxy resin formulation and subsequently preparing a prepreg from the epoxy resin impregnated carbon fabric without the above-mentioned deformation problems, wherein the carbon fabric has a variable carbon fiber areal weight weave structure. Summary of the invention

[0005] One embodiment of the present invention relates to a method for producing a prepreg product, the method comprising the following steps: (a) providing a fast-curing resin composition; (b) forming a film of the resin from step (a) on the surface of one side of a release substrate sheet; (c) providing a fiber fabric substrate sheet having a cross-sectional thickness in which the fiber weight per unit area varies; (d) contacting the surface of at least one side of the fiber fabric substrate sheet of step (c) with the resin of the resin film sheet of step (b); (e) applying pressure to the surface of the other side of the release substrate sheet opposite to the resin film to impregnate the fiber fabric substrate with the fast-curing resin composition; and (f) allowing the fiber fabric substrate impregnated with the fast-curing resin composition of step (e) to partially cure to form a prepreg product.

[0006] In another embodiment, the method of the present invention includes impregnating an epoxy resin into a carbon fabric having varying fiber basis weights, and then forming a prepreg from the carbon fiber fabric impregnated with the epoxy resin.

[0007] In yet another preferred embodiment, the method of the present invention uses a target average film thickness (e.g., 540 g / m 2 ) is used to pre-impregnate fabrics with variable fiber basis weight carbon fiber structures and to generate equal pressure by adding release paper to the desired locations (low fiber basis weight) to produce uniform pressure required for impregnation without deforming the fabric (for example, over a 12 inch (30.48 centimeters (cm)) width of the fabric).

[0008] In yet another preferred embodiment, the present invention comprises a roll assembly apparatus for producing a resin impregnated prepreg product.

[0009] The present invention utilizes a single layer (with all fiber angles contained within the same prepreg) broadgood prepreg having varying thickness across the width to mold complex cross-sectional tubular shapes having non-uniform diameters.

[0010] Advantageously, the prepreg produced by the method of the present invention may be moulded to form moulded fibre reinforced composite structures having complex cross-sections, such as tubular non-uniform diameter sections. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It can be used to form prepreg products (such as the following Figure 3 A perspective view of a schematic diagram of an S-shaped roller system apparatus for the prepreg shown in FIG.

[0012] Figure 2 is along Figure 1 A cross-sectional view taken along line 2-2.

[0013] Figure 3 is used Figure 1 An enlarged cross-sectional view of a "dumbbell" shaped prepreg product formed by impregnating a carbon fiber fabric substrate with epoxy resin.

[0014] Figure 4 is an enlarged cross-sectional view of another shaped prepreg product formed by impregnating a carbon fiber fabric substrate with an epoxy resin. DETAILED DESCRIPTION

[0015] "Broadweave" is a term used in the textile industry for cloth woven in standard or wider widths, particularly as distinguished from tapes, strips, or trims; it generally includes woven fabrics over 18 inches (450 mm) wide.

[0016] With respect to the resin composition contacting the fiber material, "infusion," "impregnation," and "pre-preg" are used interchangeably herein and mean herein causing the resin composition to flow into the body of the fiber material to fill, permeate or saturate the fiber material with the resin composition.

[0017] In a broad embodiment, a method for producing a prepreg product of the present invention comprises impregnating a fiber fabric substrate having a cross-sectional thickness with a varying fiber weight per unit area with a fast-curing resin composition; applying a varying pressure along a horizontal axis of the resin-impregnated fiber fabric substrate; and partially curing the fiber fabric substrate impregnated with the fast-curing resin composition to form a prepreg product.

[0018] The fast curing resin composition that can be used in the method of the present invention may include, for example, a fast curing epoxy resin system, formulation or composition. In a preferred embodiment, for example, the fast curing epoxy resin composition described in WO2017066056 can be used in the method of the present invention. The fast curing epoxy resin composition that can be used in the present invention includes an epoxy resin composition that more evenly infuses the resin into the fiber material to form a prepreg or composite material product.

[0019] As described in WO2017066056, the fast curing epoxy resin composition that can be used in the present invention includes an epoxy resin composition, the epoxy resin composition comprising a solid epoxy resin containing oxazolidinone as a first epoxy component; a soluble latent catalyst and a latent hardener as a second epoxy component, the latent hardener having a particle distribution in which at least 35 weight percent (wt%) of the particles have an average particle size of less than 2 microns (μm) based on the total weight of the hardener. By using a latent hardener having a desired particle distribution (e.g., at least 35% (%) of the particles have a diameter less than 2 μm), it is possible to achieve a more uniform infusion of the epoxy resin composition into the fiber material. This in turn provides an epoxy resin composition with a faster curing rate, which reduces the molding cycle time and thereby increases the rate at which articles and components molded from prepregs can be prepared.

[0020] In a general embodiment, it is desirable that the epoxy resin composition selected for infusion have a glass transition temperature (Tg) of 0 degrees Celsius (° C.) to less than 15° C. At these Tg levels, advantageously, the epoxy resin composition can be rapidly infused into the fiber material while minimizing and reducing void spaces (e.g., bubble pockets) within the prepreg.

[0021] The epoxy formulations described above advantageously provide: (1) prepregs with relatively fast cure rates (e.g., curable within 3 minutes (min) at 150°C); (2) provide carbon fiber prepregs with low to negligible tack; (3) provide prepregs with long shelf lives (e.g., greater than 40 days at 23°C and at least 1 year at -20°C); and (4) provide final cured fiber reinforced composites with high Tg (onset), e.g., greater than 100°C; and Tg (peak Tan δ), e.g., greater than 140°C. Another benefit of using the epoxy resin system described above is that the resin is curable without the use of an external mold release agent.

[0022] Once the above-mentioned epoxy resin composition is prepared, the epoxy resin composition can be poured into the fiber material in the form of tow or fabric (such as carbon fiber fabric roll) to form the prepreg according to the inventive method. The above-mentioned epoxy resin composition according to the embodiment of the present invention can be combined with a variety of different reinforcing fibers. The fiber of the fabric used in the present invention can include, for example, carbon fiber, graphite fiber, glass fiber, ceramic fiber, aramid fiber, natural fiber (such as basalt, hemp, seaweed, hay, flax, straw, jute or coconut). In a preferred embodiment, the carbon fiber used can be in the form of fabric and can be in the form of random, knitted, non-woven, multi-axial (such as, no crimped fabric), braided or any other suitable pattern. Fabric should be thermodynamically and chemically stable under the condition of prepreg formation (such as, curing epoxy resin composition); and fabric should be compatible with the selected resin for use in the infusion process of fabric.

[0023] In a preferred embodiment, the method of the present invention for producing a prepreg product comprises the following steps: (a) providing a fast-curing resin composition; (b) forming a film of the resin from step (a) on the surface of one side of a release substrate sheet; (c) providing a fiber fabric substrate sheet having a cross-sectional thickness in which the fiber weight per unit area varies; (d) contacting the surface of at least one side of the fiber fabric substrate sheet of step (c) with the resin of the resin film sheet of step (b); (e) applying pressure to the surface of the other side of the release substrate sheet opposite to the resin film to impregnate the fiber fabric substrate with the fast-curing resin composition; and (f) allowing the fiber fabric substrate impregnated with the fast-curing resin composition of step (e) to partially cure to form a prepreg product.

[0024] Typically, the method for preparing the prepreg of the present invention includes forming a film or sheet of the above-mentioned fast curing resin composition from the above-mentioned step (a) on the surface of one side of the sheet material. For example, this step (b) can be achieved by extruding a resin composition (e.g., epoxy resin) onto the sheet material to form a film resin coating on the sheet material. The resulting thickness of the film resin can vary according to the final prepreg product produced. For example, in a general embodiment and not limited thereto, the thickness of the FAW material can be 0.0119 inches (0.03cm) to 0.0125 inches (0.032cm). Typically, in one embodiment, the thickness of the film resin can be such that the resin is at least 30% to 50% by weight of the prepreg composite material; and in another embodiment, 35% to 45% by weight. In a preferred embodiment, the thickness of the film resin can be at least 40% by weight of the prepreg composite material; and the fiber substrate can be at least 60% by weight of the prepreg composite material.

[0025] The sheet material may be a release film or paper from which the film coating of the epoxy resin composition will be transferred to the fiber material during the contacting step (pre-impregnation) of the method. The sheet material including the film or paper may be made of, for example, a paper sheet or a Teflon material sheet coated with a release agent, etc. In a general embodiment but not limited thereto, the thickness of the sheet material may be, in one embodiment, 0.007 inches (0.018 cm) to 0.009 inches (0.023 cm).

[0026] After the film of the epoxy resin composition has been deposited on the sheet material, the sheet material with the film resin coating can be passed through a cooling roller to cool the epoxy resin composition. The sheet material with the cooled epoxy resin composition can then be wound on a roller for immediate use or future use. In a preferred embodiment, the release paper or film on which the epoxy resin composition is coated as a film can be rewound on a roller for later use after the step of cooling the epoxy resin composition.

[0027] In one embodiment of the method, the sheet material having the epoxy resin composition film coating can be brought into contact with the surface of the above-mentioned fiber fabric substrate or fiber material (e.g., NCF, woven fabric or unidirectional fabric) from the above-mentioned step (c). Then, the fiber material and the sheet material having the epoxy resin composition film coating can be subjected to pressure after or during the contacting step to infuse the epoxy resin into the fiber material.

[0028] Standard conventional prepreg production lines and auxiliary equipment for prepreg production lines known in the art can be used for the contacting step and the subsequent or simultaneous impregnation step. The prepreg production line used in the method of the present invention can be any known prepreg production line, including, for example, (1) an unwinding station, (2) a heating table (with an insulating mat), (3) an S-shaped winding pressure roller, and (4) a speed-controlled traction roller.

[0029] In a preferred embodiment, the fiber material sheet can be sandwiched between two sheets, and the film coating of the epoxy resin composition is deposited on the sheet; and the fiber material and the sheet material coated with the epoxy resin composition can be provided as continuous belts from respective supply rollers. The contacting step of the method of the present invention can be carried out in the above-mentioned film-forming equipment for forming the sheet, and the sheets of different substrates are pressed together using an S-shaped winding roller gap pressing roller system equipment. However, in a preferred embodiment of the present invention, the equipment is improved to accommodate the desired fiber fabric substrate with a varying fiber unit area weight. In addition, the equipment is improved to provide uniform pressure along the thickness of the fiber fabric substrate with a varying fiber unit area weight.

[0030] Reference Figure 1 and Figure 2, shows a preferred improved embodiment of the S-shaped winding pressure roller used in the present invention, which is generally indicated by the reference numeral 10 and includes a series of rollers, such as a top roller 11, a middle roller 12 and a bottom roller 13. In one embodiment, as shown by the direction arrow A, the sandwich material is fed into the roller system 10. The sandwich material passes / rotates through the roller system 10 (such as the direction shown by the turning arrows B and C). Figure 2 ). and the infused fibrous material exits the roller system 10 as shown by directional arrow D.

[0031] In a preferred improved embodiment of the S-shaped winding pressure roller, the size of the intermediate roller 12 varies as shown in the edge portions 12a and 12b; and is integral with the middle portion 12c. Generally, the shape of the roller member 12 can be described as two cylindrical members connected together by an intermediate rod section and integral with the intermediate rod section; or simply put, when the roller member 12 is formed from the outer edge portion 12a and 12b, the outer edge portion 12c is formed from the inner edge portion 12c; and the outer edge portion 12c is formed from the inner edge portion 12c. Figure 1 The roller component 12 may be in the shape of a "dumb bellweight" or "dumbbell" component 12 when the component 12 is viewed in the front perspective view shown in FIG. The intermediate roller 12 may be formed by using one or more release papers of a predetermined thickness on the edges of a regular roller having a constant diameter and length, and "increasing" the diameter of the edges 12a and 12b of the roller 12 to the desired diameter to provide the preferred shape of the roller 12 to accommodate the resin impregnated fiber fabric.

[0032] The dumbbell-shaped roller, namely the intermediate roller 12 disposed between the rollers 11 and 13, provides a first gap 14 and a second gap 15, which allows the required pressure to be applied to the supply film 21 (eg Figure 2 shown).

[0033] After the contacting step of bringing the sandwich material (i.e., the combined sheets of resin and fiber material) together, the sandwich material can be passed through a pair of rollers that press the epoxy resin composition into the opposing surfaces of the fiber material. The prepreg of the present invention can be prepared by applying pressure to the sandwich material to infuse (or impregnate) the fiber material (or carbon fiber fabric substrate) with the epoxy resin composition. In a preferred embodiment, the step (e) of applying pressure is a step carried out by impregnating (or infusing) the carbon fiber fabric substrate with a fast-curing epoxy resin composition. In another embodiment, a fiber fabric substrate having a variable fiber weight per unit area region is impregnated with a fast-curing resin composition to obtain uniform impregnation over the width of the variable fiber weight per unit area composite material. "Uniform impregnation" with respect to impregnating the resin into the fiber material means in this article that the predetermined level of impregnation is the same over the entire width of the variable fiber weight per unit area composite material, including in low fiber weight per unit area regions and high fiber weight per unit area regions.

[0034] In the method of impregnating the above-mentioned carbon fiber fabric substrate having a varying fiber unit area weight with the above-mentioned epoxy resin composition, the above-mentioned roller system can be used to provide the desired impregnated fiber fabric to form a prepreg. The impregnation step of the method of the present invention includes, for example, feeding the carbon fiber fabric substrate disposed between two sheets of fast-curing epoxy resin composition films into the roller system (e.g., Figure 1 The carbon fiber fabric substrate impregnated with the fast curing epoxy resin composition then leaves the roller system (as shown by arrow A in FIG. 1 ), wherein the resin of the top resin sheet contacts the top surface of the fiber fabric substrate, and the resin of the bottom resin sheet contacts the bottom side surface of the fiber fabric substrate. Figure 1 as indicated by arrow D in FIG.

[0035] refer to Figure 3 , there is shown a shaped prepreg, generally indicated by the reference numeral 30 , comprising a resin matrix 31 infused into a fabric of fibers 32 . Figure 3 The prepreg shown in Figure 1 The resulting prepreg is processed by the S-shaped winding roller system 10 shown in FIG. The top release paper 33 and the bottom release paper 34 are arranged to sandwich the prepreg 30 between the top layer 33 and the bottom layer 34, respectively. The prepreg 30 includes an edge portion generally indicated by the reference numeral 40A and an edge portion generally indicated by the reference numeral 40B, both of which are integrated with a middle portion generally indicated by the reference numeral 50. Figure 3 As shown in FIG. 5 , edge portions 40A and 40B are more compressed than middle portion 50 .

[0036] refer to Figure 4 , shows another embodiment of a shaped prepreg, generally indicated by the reference numeral 60, comprising a resin matrix 61 infused into a fabric of fibers 62. A top release paper 63 and a bottom release paper 64 are provided to sandwich the prepreg 60 between the top layer 63 and the bottom layer 64, respectively. The prepreg 60 includes an edge portion generally indicated by the reference numeral 70A and an edge portion generally indicated by the reference numeral 70B, both of which are integral with a middle portion generally indicated by the reference numeral 80. As shown in FIG. Figure 4 As shown in FIG. 8 , the middle portion 80 is more compressed than the edge portions 70A and 70B. Figure 4 The prepreg shown in may also be the resulting prepreg processed by another alternative S-shaped winding roller system (not shown), wherein the S-shaped winding roller system has a series of rollers (not shown), such as a top roller, a middle roller and a bottom roller, which provides a modified middle roller (not shown) in the roller system to provide the shape of the middle portion 80 of the prepreg 60.

[0037] In one embodiment, the infusion process can be carried out at an elevated temperature so that the viscosity of the epoxy resin composition can be further reduced; therefore, the heating step can promote the rapid infusion of the epoxy resin composition into the fiber material. For example, the interlayer material can be subjected to heating to increase the temperature of the epoxy resin composition by passing the combination of the fiber material and the epoxy resin composition through a heating plate to heat the epoxy resin composition. However, the temperature cannot be so hot over an extended period of time that an undesirable level of curing of the epoxy resin composition occurs. For example, during the impregnation step (e), the infusion of the epoxy resin composition into the fiber material can be carried out at a temperature in the range of 100°C to 130°C in one embodiment, at a temperature in the range of 100°C to 125°C in another embodiment; and at a temperature in the range of 110°C to 120°C in yet another embodiment. The above-mentioned heating for infusing the epoxy resin composition into the fiber material can be carried out using a heating table and a heated roller.

[0038] It should be recognized that temperature ranges outside the above ranges may also be used. However, the use of higher or lower infusion temperatures generally requires adjustment of the machine speed at which the infusion process is performed. For example, at temperatures above about 120°C, it may be necessary to perform the infusion process at a higher machine speed to reduce the duration of exposure of the epoxy resin composition to the high temperature, thereby avoiding undesirable crosslinking of the epoxy resin composition. Similarly, in order to obtain the desired level of infusion and thereby reduce the void space in the prepreg, the use of a lower infusion temperature will generally require a lower machine speed to infuse the epoxy resin composition into the fiber material. In a preferred embodiment, the epoxy resin composition can be applied to the fiber material at a temperature within the above range; and the epoxy resin composition can be consolidated into the fiber material by pressure. For example, the pressure applied to the fiber material and the resin composition can be applied by passing the composition through one or more pairs of rollers.

[0039] In a preferred embodiment, the combination of the fiber material and the epoxy resin composition may be subjected to the further steps of passing the combination through a heated plate and then passing the combination through a second roller gap to further infuse the epoxy resin composition into the fiber material to form a resin-infused prepreg. The prepreg may then be cooled, for example, by passing the material through a cooling roller or cooling plate. After cooling, the prepreg may be wound onto a supply roll for future use.

[0040] As mentioned above, the pouring step can be carried out at an elevated temperature to reduce the viscosity of the epoxy resin composition. In addition, the epoxy resin composition poured can be subjected to a partial curing step (advancing) to improve the glass transition temperature of the epoxy resin composition in the prepreg. The prepreg can then be packaged, stored or transported as required. As previously discussed, in some embodiments, it may also be desirable to subject the prepreg to a propulsion step to improve the Tg of epoxy resin and thus reduce the viscosity of the prepreg.

[0041] In another preferred embodiment, during the impregnation step (e), a pinch roller "nip" operation may be used. During the pinch roller "nip" operation of a standard prepreg production line, additional pressure must be applied to the thinner portions of the prepreg. The nip gap is set to accommodate the thickest portion to reduce the deformation seen in this area. A portion of release paper having a predetermined thickness (e.g., 0.008 inches (0.02 cm) thick) may be added to the middle roller in the thinner area of ​​the wide article (S-shaped winding operation with 3 rollers allowing 2 nip gaps). The use of release paper allows for uniform pressure, regardless of thickness variations, to provide optimal infusion of epoxy resin into the carbon fiber fabric substrate, thereby forming a prepreg with minimal deformation.

[0042] The conditions of the impregnation process of the present invention may vary and may depend on various factors including, for example, the type of fabric used, the size of the fabric used, the FAW of the fabric used, and the design and size of the prepreg product to be produced. As an illustration of the process of the present invention, but not limited thereto, in one specific embodiment, a wide article carbon fiber fabric sheet is fed between two epoxy resin films deposited on one side of each of two release papers, wherein the resin contacts the fabric. The combined sheet is fed into an S-shaped winding roll assembly apparatus, and the infusion or prepreg step is performed, for example, as follows:

[0043] (1) The nip temperature may range, for example, from 100°C to 130°C in one embodiment, from 100°C to 125°C in another embodiment; and from 110°C to 120°C in yet another embodiment.

[0044] (2) The table temperature may range from 100°C to 130°C in one embodiment, from 100°C to 125°C in another embodiment; and from 110°C to 120°C in yet another embodiment.

[0045] (3) The first roll gap between the upper roll and the middle roll and between the lower roll and the middle roll (at Figure 1 The thickness of the substrate (generally indicated by reference numeral 14) can be from 0.022 inches to 0.026 inches (0.056 cm to 0.066 cm) in one embodiment.

[0046] (4) The second roll gap between the upper roll and the middle roll and between the lower roll and the middle roll (at Figure 1 The thickness of the substrate (generally indicated by reference numeral 15) can be from 0.022 inches to 0.025 inches (0.056 cm to 0.064 cm) in one embodiment.

[0047] (5) The speed at which the material is fed into the roller system can be from 1.0 ft / min to 2.4 ft / min (0.305 m / min to 0.732 m / min) in one embodiment; from 1.0 ft / min to 2.0 ft / min (0.305 m / min to 0.610 m / min) in another embodiment; and from 1.5 ft / min to 2.0 ft / min (0.457 m / min to 0.610 m / min) in yet another embodiment.

[0048] In one embodiment, the release paper used in the method can have a thickness of, for example, 0.007 inches (0.018 cm) to 0.009 inches (0.023 cm). Any standard release paper known in the art can be used in the present invention. Release paper can be used so that the material being processed does not stick to the metal roller. Alternatively, the hold-down roller can be changed to account for the change in thickness. For example, instead of adding release paper to the metal roller, the metal roller can be machined in a manner that compensates for the change in thickness.

[0049] Parameters that can be used in the present invention can be "fixed" parameters, i.e., parameters that do not change in a set of processing runs of the fabric and resin sheet. For example, the above-mentioned roller gap temperature and workbench temperature can be fixed parameters. To illustrate the present invention but not to be limited thereto, in one embodiment, a roller gap range of 0.023 inches to 0.026 inches (0.058 cm to 0.066 cm), added release paper, and a slower speed of 1.8 ft / min (0.549 m / min) can be used to demonstrate the practicality of the present invention. The roller gap temperature and workbench temperature can remain fixed throughout the present invention.

[0050] Once the fiber fabric substrate impregnated with the fast curing epoxy resin composition of step (e) leaves the roller system, the impregnated fabric is allowed to partially cure to form a prepreg product. Thereafter, the produced prepreg can be rolled onto a core; the prepreg roll can then be transported to storage (where it is stable, as described above) or the prepreg can be used in a molding process.

[0051] The prepreg prepared by the method of the present invention advantageously exhibits low tack, ie the prepreg is easy to handle; and when used or stored in rolls, the prepreg does not stick together at room temperature.

[0052] Using the method of the present invention, the prepreg is advantageously not over-crosslinked, i.e. the prepreg does not exhibit problems such as the creation of voids in the prepreg as the prepreg has a Tg below 20° C. Using an infusion processed prepreg at high prepreg temperatures can result in an undesirable "overcooked" prepreg which has a Tg above 20° C., can exhibit undesirable surface qualities, and can become stiff and difficult to process.

[0053] In a broad embodiment, the carbon fiber reinforced composite material of the present invention is a fully cured composite material formed by fully curing the prepreg produced as described above. For example, in a broad embodiment, the method for preparing a carbon fiber reinforced composite material comprises the following steps: (A) providing a resin impregnated fabric prepreg prepared by the above method; and (B) curing the impregnated fabric prepreg of step (A) to form a fiber reinforced composite product.

[0054] In one embodiment, the curing step (or advancing step) of fully curing the prepreg may be performed by heating the prepreg at a temperature of 140° C. to 155° C. for a curing time of 3 min to 5 min.

[0055] An object of the present invention is to manufacture a fiber reinforced composite material (e.g., a carbon fiber reinforced composite material) having a variable cross section along the width of the composite material. For example, in a preferred embodiment, the fiber reinforced composite material can be a tubular member having a variable cross section along the diameter. To date, it has been impossible to produce the carbon fiber reinforced composite material with FAW of the present invention using the methods of the prior art. Advantageously, the carbon fiber composite material of the present invention can now be used to manufacture automotive composite materials, such as for interior and exterior components, wherein these components have different shapes, sizes and dimensions. For example, in a preferred embodiment, the carbon fiber composite material of the present invention can be used to manufacture a composite component, which in turn can be used for an automotive steering column.

[0056] Example

[0057] The following examples are provided to further illustrate the present invention in detail but should not be construed as limiting the scope of the claims.All parts and percentages are by weight unless otherwise indicated.

[0058] The following Inventive Examples (Inv. Ex.) and Comparative Examples (Comp. Ex.) are explained in Table I below.

[0059] Table I - Raw Materials

[0060]

[0061] Examples 1 and 2 and Comparative Examples AC

[0062] To use VORAFUSE TM P6300 resin system and carbon fiber hybrid wide products provided by A&P are used to make prepregs, using an experimental prepreg production line under standard prepreg conditions for making conventional prepregs. This results in poor infusion on the outside (thin area) and deformation in the middle (thick area), which is related to the appearance / deformation level. The material is tested only when it reaches an acceptable subjective visible appearance, as determined according to the rating scale (described below). The roller gap is then set for the average thickness of the prepreg (Comparative Example B). Similar results were seen in the first attempt (Comparative Example A). Release paper is then added to the middle roller to compensate for the variable fiber unit area weight on the material width, and the roller gap is opened to be set at the thickest part of the material (Comparative Example C). This shows a slight improvement compared to (Comparative Example A) and (Comparative Example B). For additional pressure and time, at temperatures that improve impregnation and deformation, the roller gap is reduced and the speed is slowed down (Example 1 of the present invention). The acceptance and deformation levels are acceptable, and the material has been tested in the lower and higher FAW regions. In the final run, the nip gap was opened slightly to further reduce the deformation (Inventive Example 2). This further improved the appearance level and the material was tested again. However, due to the uniqueness of the material, the material was tested in the direction of the expected part (horizontal vs. vertical in previous tests), so the difference in storage modulus was expected (more fibers extended in the test direction).

[0063]

[0064] A rating scale was developed to indicate the "Appearance / Deformation Level" of a sample to determine if the sample passed the necessary criteria to subject the sample to further testing. The rating scale includes a numerical rating scale of "1" to "4", where "1" is the least acceptable and "4" is the most acceptable. A more detailed description of ratings 1-4 is described in Table IV. For further testing of the sample, a sample with an appearance / deformation rating of 3 is required.

[0065] Table IV - Appearance / Deformation Rating Scale

[0066]

Claims

1. A method for producing a prepreg product, the method comprising the following steps: (a) providing a fast curing resin composition; (b) forming a film of the resin from step (a) on a surface of one side of the release substrate sheet; (c) providing a fiber fabric substrate sheet having a cross-sectional thickness with varying fiber basis weight; (d) contacting at least one surface of the fiber fabric substrate sheet of step (c) with the resin side of the resin film sheet of step (b) so that the resin contacts the fiber fabric substrate; (e) applying pressure to the surface of the release substrate sheet on the other side opposite to the resin film to impregnate the fiber fabric substrate with the fast-curing resin composition and obtain uniform impregnation of the resin over the width of the fiber fabric substrate sheet having a cross-sectional thickness with a varying fiber basis weight; as well as (f) allowing the fiber fabric substrate impregnated with the fast curing resin composition of step (e) to at least partially cure the resin to form a prepreg product.

2. The method of claim 1, wherein the fast curing resin composition is an epoxy polymer.

3. The method of claim 1, wherein the fiber fabric substrate is a carbon fiber fabric substrate.

4. The method of claim 1, wherein the fiber fabric substrate impregnated with the fast curing resin composition of step (f) is heated at a temperature sufficient to at least partially cure the resin to form a prepreg product.

5. The method of claim 4, wherein the temperature is 100°C to 130°C.

6. The method according to claim 1, wherein the fiber fabric substrate is a wide-width product of hybrid carbon fibers with a fiber unit area weight.

7. A method for producing a fiber-reinforced composite product, the method comprising: (A) providing a resin-impregnated textile prepreg by a process comprising the steps of: (a) providing a fast curing resin composition; (b) forming a film of the resin from step (a) on a surface of one side of the release substrate sheet; (c) providing a fiber fabric substrate sheet having a cross-sectional thickness with varying fiber basis weight; (d) contacting at least one surface of the fiber fabric substrate sheet of step (c) with the resin side of the resin film sheet of step (b) so that the resin contacts the fiber fabric substrate; (e) applying pressure to the surface of the release substrate sheet on the other side opposite to the resin film to impregnate the fiber fabric substrate with the fast-curing resin composition and obtain uniform impregnation of the resin over the width of the fiber fabric substrate sheet having a cross-sectional thickness with a varying fiber basis weight; as well as (f) allowing the fiber fabric substrate impregnated with the fast-curing resin composition of step (e) to at least partially cure the resin to form a prepreg product; as well as (B) curing the impregnated textile prepreg of step (A) to form a fiber-reinforced composite product.

8. The method of claim 7, wherein the fiber reinforced composite article is a molded fiber reinforced composite article.

9. A method for preparing a carbon fiber reinforced composite material, the method comprising: (a) providing a fast curing resin composition; (b) forming a film of the resin from step (a) on a surface of one side of the release substrate sheet; (c) providing a fiber fabric substrate sheet having a cross-sectional thickness in which the fiber basis weight varies, wherein the fiber fabric substrate is a carbon fiber; (d) contacting at least one surface of the fiber fabric substrate sheet of step (c) with the resin of the resin film sheet of step (b); (e) applying pressure to the surface of the release substrate sheet on the other side opposite to the resin film to impregnate the fiber fabric substrate with the fast-curing resin composition and obtain uniform impregnation of the resin over the width of the fiber fabric substrate sheet having a cross-sectional thickness with a varying fiber basis weight; (f) allowing the fiber fabric substrate impregnated with the fast-curing resin composition of step (e) to partially cure to form a prepreg product; and (g) curing the prepreg product of step (f) to form a cured carbon fiber reinforced composite material.

10. The method of claim 9, wherein the temperature of the curing step (g) is 140°C to 155°C.

11. The method of claim 9, wherein the curing time of the curing step (g) is 3 minutes to 5 minutes.

12. The method according to claim 1 or 9, wherein a roller assembly device is used to produce the resin-impregnated prepreg product; the roller assembly device comprises: An S-shaped wrapping pinch roller assembly including a combination of at least a first roller, a second roller, and a third roller in rotational contact with one another; wherein the second roller is disposed at a sandwich position between the first roller and the third roller; wherein the second roller has a certain diameter, and the diameter is modified to provide uniform pressure on the surface of the side of the release substrate sheet opposite to the side of the resin film, so as to impregnate the fiber fabric substrate with the fast-curing resin composition and obtain uniform impregnation of the resin over the width of the fiber fabric substrate sheet having a cross-sectional thickness with a fiber unit area weight varying, The first roller gap between the first roller and the second roller and between the third roller and the second roller is 0.056 cm to 0.066 cm; The second roller gap between the first roller and the second roller and between the third roller and the second roller is 0.056 cm to 0.064 cm; and The material feed rate into the roller assembly device is 0.305 m / min to 0.610 m / min.

13. The method according to claim 12, wherein the material feed rate into the roll assembly device is 0.457 m / min to 0.610 m / min.

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