Claims:WE CLAIM:

What is claimed is:

1. A method of manufacturing a fiber-reinforced compositearticle, comprising:
arranging a plurality of reinforcing fibers in an open mold;
sealing the mold with a vacuum bag and evacuating air therefrom;
preparing a mixture having siliceous particles mixed with a resin material;
infusing the plurality of reinforcing fibers with the prepared mixture in the sealed mold until substantially complete impregnation thereof;
curing the impregnated reinforcing fibers; and
de-molding cured product from the mold.

2. The method of claim 1, wherein the siliceous particles are mixed with the resin material in a weight percentage range of 0.01 to 10 %.

3. The method of claim 1, wherein the plurality of reinforcing fibers are pre-impregnated with a polymer matrix material.

4. The method of claim 1, wherein preparing the mixture further comprises mixing the siliceous particles with a hardener material.

5. The method of claim 4, wherein preparing the mixture comprises mechanically stirringthe siliceous particles with one or more of the resin material and the hardener material in a temperature range of 20-35 °C.

6. The method of claim 1 further comprising placing an infusion mesh in the mold such that the mixture passes through the infusion mesh while entering the mold to facilitate substantially even spreading of the mixture in the mold to be incontact with the plurality of reinforced fibers therein.

7. The method of claim 1 further comprising arranging a bleeder fabric in the mold to facilitate removal of air and volatiles from within the vacuum bag during the curing process.

8. The method of claim 1 further comprising laying a release film on one or more surfaces of the mold to facilitate removal of the cured product from the mold.

9. The method of claim 1, wherein the plurality of reinforcing fibers comprises one or a combination of glass, carbon, aramid, basalt, paper, wood and asbestos.

10. The method of claim 1, wherein the resin material comprises one or more of epoxy, vinylester, cyanoester, bismalmeide, polyimide, polyamide, polyacrylate polyester and phenol formaldehyde based polymers.

11. The method of claim 1, wherein the siliceous particles comprise one or more of halloysite, delaminated clays, diatomaceous earth and nano-clay.

12. The method of claim 1, wherein the mold is sealed to generate pressure of less than 10 millibars therein.

13. The method of claim 1, wherein the plurality of reinforcing fibers are infused with the mixture in the sealed mold in a temperature range of 25-45 °C.

14. The method of claim 1, wherein curing the impregnated reinforcing fibers comprises pre-curing the impregnated reinforcing fibers for 1-4 hours in a temperature range of 50-70 °C and post-curing for 5-10 hours in a temperature range of 60-90 °C.

15. The method of claim 1, wherein the infusion process is carried out at a relative humidity of 25 to 55 %for a period ranging from 1 minute to 2 hours.

16. The method of claim 1, wherein the fiber reinforced composite article is a blade of a wind turbine.

17. A composition for forming a fiber-reinforced composite article, comprising:
a resin material;
a plurality of unidirectional glass reinforcing fibers suspended in the epoxy resin material, wherein the reinforcing fibers are in the range of 40-70 % by volume fraction in the composition; and
a plurality of siliceous particles uniformly dispersed and infused with the unidirectional glass fibers in the epoxy resin material, wherein the siliceous particles are in the range of 0.01-10 % by weight in the composition.

18. The composition of claim 17, wherein the resin material comprises one or more of epoxy, vinylester, cyanoester, bismalmeide, polyimide, polyamide, polyacrylate polyester and phenol formaldehyde based polymers.

19. The composition of claim 17, wherein the siliceous particles comprise one or more of halloysite, delaminated clays, diatomaceous earth and nano-clay.

20. The composition of claim 17, wherein the fiber reinforced composite article is a blade of a wind turbine.
, Description:METHOD OF MANUFACTURING FIBER-REINFORCED COMPOSITE ARTICLE AND COMPOSITION THEREOF

FIELD OF THE PRESENT DISCLOSURE
[0001] The present disclosurerelates to a method of manufacturing a fiber-reinforced composite article and further relates to a composition for a fiber-reinforced composite article, which provides improved strength and fatigue life to be employed in part or full for wind blade structures.

BACKGROUND
[0002] Material sciences related to composite materials have revolutionized the construction and assembly of everyday items. Composite is a material formed with two or more components, combined as a macroscopic structural unit with one component as continuous matrix, and other as fillers or reinforcements. Composite materials, which generally refer to a polymer matrix reinforced with a fiber material, have been used, for example, in the production of various items such as bicycles, vehicles, and airplanes. Such manufactured goods are increasingly relying on large quantities of composite materials in order to reduce weight and/or increase strength. Furthermore, as composite technology has improved, the mechanical properties of composites have been tailored for specific applications, such as a blade of a wind turbine. In case of blade materials, normally, matrix is the material that holds the reinforcements together and has lower strength than the reinforcements. In the fiber reinforced plastics, the polymers, either thermoplastics or thermosetting plastics, act as a matrix and organic or inorganic fibers like carbon/natural fiber and glass fibers are reinforcements. The reinforcing fiber is the main load-carrying component as it provides high strength and stiffness as well as resistance to bending and breaking under the applied stress.
[0003] One of the strategic objectives in wind turbine manufacturing has been to combine design, material and process developments using light-weight materials to create cost-efficient and high strength blades. It is well known that the power generation of a wind turbine can be directly related to the rotor plane area of the blade. The larger the diameter of its blades, the more power it is capable of extracting from the wind. However, the increment in weight of large blades along with harsh environmental conditions (e.g. extreme temperatures, humidity and saline atmosphere) puts the materials used under considerable stress leading to shorter operational life. Notably, this problem has pushed more wind energy companies to embrace carbon fiber based composite materials which in a way ensures retrofitting of the existing turbine designs with longer blades without increased weight.
[0004] However, substituting glass fibers with carbon fibers brings some challenges. For instance, carbon fibers have a low damage tolerance, and the resultant product compressive strength is highly dependent on fiber alignment. Besides the implementation of carbon fibers also brings new processing challenges as well. For instance, carbon fibers require perfect fiber alignment, and must be cured quickly. Small misalignments can lead to a significant reduction of compressive and fatigue strength. Further, achieving carbon fiber wet-out during vacuum infusion is difficult resulting in the use of more expensive Prepreg products. Furthermore, the implementation of carbon fibers has higher upfront cost which may go up to 10 to 20 times higher than use of regular glass fibers.
[0005] Despite these challenges, the demand for high strength, light weight and stable materials at low cost remains the requirement of the wind turbine manufacturers. Therefore, there is a need of a composition for a fiber-reinforced composite article and a method of manufacturing a fiber-reinforced composite article, such a blade of a wind turbine, which substitutes carbon fibers with other suitable material.

SUMMARY
[0006] In an aspect, a method of manufacturing a fiber-reinforced composite article is disclosed. The method comprises arranging a plurality of reinforcing fibers in an open mold. The method further comprises sealing the mold with a vacuum bag and evacuating air therefrom. The method further comprises preparing a mixture having siliceous particles mixed with a resin material. The method further comprises infusing the plurality of reinforcing fibers with the prepared mixture in the sealed mold until substantially complete impregnation thereof. The method further comprises curing the impregnated reinforcing fibers. The method further comprises de-molding cured product from the mold.
[0007] In one or more embodiments, the siliceous particles are mixed with the resin material in a weight percentage range of 0.01 to 10 %.
[0008] In one or more embodiments, the plurality of reinforcing fibers are pre-impregnated with a polymer matrix material.
[0009] In one or more embodiments,preparing the mixture further comprises mixing the siliceous particles with a hardener material.
[0010] In one or more embodiments,preparing the mixture comprises mechanically stirring the siliceous particles with one or more of the resin material and the hardener material in a temperature range of 20-35 °C.
[0011] In one or more embodiments, the method further comprises placing an infusion mesh in the mold such that the mixture passes through the infusion mesh while entering the mold to facilitate substantially even spreading of the mixture in the mold to be in contact with the plurality of reinforced fibers therein.
[0012] In one or more embodiments, the method further comprises arranging a bleeder fabric in the mold to facilitate removal of air and volatiles from within the vacuum bag during the curing process.
[0013] In one or more embodiments, the method further comprises laying a release film on one or more surfaces of the mold to facilitate removal of the cured product from the mold.
[0014] In one or more embodiments, the plurality of reinforcing fibers comprises one or a combination of glass, carbon, aramid, basalt, paper, wood and asbestos.
[0015] In one or more embodiments, the resin material comprises one or more of epoxy, vinylester, cyanoester, bismalmeide, polyimide, polyamide, polyacrylate polyester and phenol formaldehyde based polymers.
[0016] In one or more embodiments, the siliceous particles comprise one or more of halloysite, delaminated clays, diatomaceous earth and nano-clay.
[0017] In one or more embodiments, the mold is sealed to generate pressure of less than 10 millibars therein.
[0018] In one or more embodiments, the plurality of reinforcing fibers are infused with the mixture in the sealed mold in a temperature range of 25-45 °C.
[0019] In one or more embodiments, curing the impregnated reinforcing fibers comprises pre-curing the impregnated reinforcing fibers for 1-4 hours in a temperature range of 50-70 °C and post-curing for 5-10 hours in a temperature range of 60-90 °C.
[0020] In one or more embodiments, the infusion process is carried out at a relative humidity of 25 to 55 % for a period ranging from 1 minute to 2 hours.
[0021] In one or more embodiments, the fiber reinforced composite article is a blade of a wind turbine.
[0022] In another aspect, a composition for forming a fiber-reinforced composite article is disclosed. The composition comprises a resin material. The composition also comprises a plurality of unidirectional glass reinforcing fibers suspended in the epoxy resin material, such that the reinforcing fibers are in the range of 40-70 % by volume fraction in the composition. The composition further comprises a plurality of siliceous particles uniformly dispersed and infused with the unidirectional glass fibers in the epoxy resin material, such that the siliceous particles are in the range of 0.01-10 % by weight in the composition.
[0023] In one or more embodiments, the resin material comprises one or more of epoxy, vinylester, cyanoester, bismalmeide, polyimide, polyamide, polyacrylate polyester and phenol formaldehyde based polymers.
[0024] In one or more embodiments, the siliceous particles comprise one or more of halloysite, delaminated clays, diatomaceous earth and nano-clay.
[0025] In one or more embodiments, the fiber reinforced composite article is a blade of a wind turbine.
[0026] The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.

BRIEF DESCRIPTION OF THE FIGURES
[0027] For a more complete understanding of example embodiments of the present disclosure, reference is now made to the following descriptions taken in connection with the accompanying drawings in which:
[0028] FIG. 1 illustrates a schematic view of a setup for manufacturing a fiber-reinforced composite article, in accordance with one or more embodiments of the present disclosure;
[0029] FIG. 2 illustrates a flowchart depicting the steps involved in manufacturing the fiber-reinforced composite article, in accordance with one or more embodiments of the present disclosure;
[0030] FIG. 3 illustrates a schematic of crack propagation in an exemplary microscopic plan view of a composite article, in accordance with prior-art; and
[0031] FIG. 4 illustrates a schematic of crack propagation in an exemplary microscopic plan view of the fiber-reinforced composite article, in accordance with one or more embodiments of the present disclosure.

DETAILED DESCRIPTION
[0032] In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. It will be apparent, however, to one skilled in the art that the present disclosure is not limited to these specific details.
[0033] Reference in this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present disclosure. The appearance of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Further, the terms “a” and “an” herein do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item. Moreover, various features are described which may be exhibited by some embodiments and not by others. Similarly, various requirements are described which may be requirements for some embodiments but not for other embodiments.
[0034] The present disclosure provides an approach of uniformly dispersing low cost siliceous particles into epoxy resin material during infusion of glass fiber sheets to form a fiber-reinforced composite article, such as a blade of a wind turbine. The siliceous particles can be formed of an individual or a combination of materials such as halloysite, diatomaceous earth, delaminated clay and/or nano-clay which can be introduced in the epoxy resin via Vacuum Assisted Resin Infusion Molding (VARIM) process under controlled processing conditions of dispersion, infusion and curing such that there is a significant improvement in the strength, fatigue life and stiffness, and resulting in composites with high strength to weight ratio.
[0035] FIG. 1 illustrates an exemplary set-up 100 for manufacturing a fiber-reinforced composite article (hereinafter, sometimes simply referred to as “composite article”), in accordance with one or more embodiments of the present disclosure. As illustrated, the set-up 100 includes a mold 102. The mold 102 may be designed to be in the shape of the composite article to be manufactured. For example, in case of the composite article being a blade of a wind turbine, the mold 102 may be designed to be in the shape of the blade of the wind turbine. In the exemplary drawings, the mold 102 is shown to be of rectangular shape only for the sake of illustration and such shape shall not be construed as limiting to the present disclosure. The mold 102 may be of appropriate size in order to allow the manufacturing process to be properly carried out. The mold 102 may be made of suitable materials to withstand, and facilitate to most extent, the manufacturing process of the present disclosure. In one or more embodiments, the mold 102 is an open mold with one open side for introduction of materials therein, as desired.
[0036] Also, as illustrated, the set-up 100 also includes a vacuum pump 104 in fluid communication with the mold 102. The vacuum pump 104 may be of required specification to generate partial vacuum inside the mold 102 within limits of desired pressure range. The vacuum pump 104 may be of any known type, such as, but not limited to, rotary vane pump, diaphragm pump, piston pump, scroll pump, etc. The set-up 100 further includes a bleeder fabric 106 (also, generally known as “breather fabric”) arranged in the mold 102 to facilitate removal of air and volatiles therefrom (as will be discussed later in the description). In one or more examples, the bleeder fabric 106 may be non-woven fabric as known in the art.
[0037] Further, as illustrated in FIG. 1, the set-up 100 includes a reservoir 108 which may be in the form of a container of sufficient volume to store, primarily, a resin material (as discussed later), generally in viscous liquid form, therein. The reservoir 108 may be disposed in fluid communication with the mold 102 by means of a tube 110 and further by a suction pump 112. The suction pump 112 may create vacuum pressure to suck the resin material from the reservoir 108 and transfer to the mold 102, via the tube 110. In some examples, the suction pump 112 may not be provided and the vacuum pressure as created by the vacuum pump 104 may be sufficient enough and thereby utilized for transfer of the resin material from the reservoir 108 to the mold 102. In one or more examples, the resin material includes one or more of epoxy, vinylester, cyanoester, bismalmeide, polyimide, polyamide, polyacrylate polyester and phenol formaldehyde based polymers.
[0038] Furthermore, as illustrated, the set-up 100 may include a release film 114 which may be laid on one or more surfaces of the mold 102 to facilitate removal of the cured product from the mold 102 (as discussed later). It may be contemplated that the release film 114 may be placed inside the mold 102 and the mixture may be poured on top thereof in the mold 102. In some examples, the release film 114 may be replaced by a peel-ply (which are well known in the art) without affecting the scope of the present disclosure. In one or more embodiments, the set-up 100 may also include an infusion mesh 116 placed in the mold 102 such that when a mixture (as discussed later) is introduced inside the mold 102, the mixture passes through the infusion mesh 116 while entering the mold 102 to facilitate substantially even spreading of the mixture in the mold 102. It may be appreciated that, herein, the infusion mesh 116 may be a highly permeable layer placed on top of the mold 102 to facilitate spreading of the mixture quickly over the lateral extent of the mold 102.
[0039] Referring now to FIG. 2, a flowchart depicting the steps involved in a method 200 of manufacturing a fiber-reinforced composite article is illustrated. The method 200 of the present disclosure is a Vacuum Assisted Resin Infusion Molding (VARIM), also sometimes interchangeably known as Vacuum Assisted Resin Transfer Molding (VARTM), based composite manufacturing process to produce high-quality large-scale components. VARIM based process is implemented in order to produce large size components, such as the fiber-reinforced composite article, with a shorten curing cycle time.
[0040] At step 202, the method 200 includes arranging a plurality of reinforcing fibers in the open mold 102. In one or more embodiments of the present disclosure, the plurality of reinforcing fibers comprises one or a combination of glass, carbon, aramid, basalt, paper, wood and asbestos. The dry glass fabrics may be of desired shape and size. In a preferred embodiment, the reinforcing fibers are unidirectional dry glass fibers. The number of layers of reinforcing fibers may vary from 1-100. In one or more embodiments, the plurality of reinforcing fibers are pre-impregnated with a polymer matrix material. That is, the reinforcing fibers are in the form of prepregs (as known in the art) in which a polymer matrix material is already present. In some examples of the fiber reinforced plastics, the polymers, either thermoplastics or thermosetting plastics, act as a matrix, and organic or inorganic fibers like carbon/natural fiber and glass fibers act as reinforcements. In one or more embodiments, the method 200 may includelaying a release film (such as, the release film 114) on one or more surfaces of the mold 102 before arranging the plurality of reinforcing fibers in the mold 102.
[0041] At step 204, the method 200 includes sealing the mold 102 with a vacuum bag (such as, a vacuum bag 118 as shown in FIG. 1). The vacuum bag 118 may be placed over the open-side of the mold 102. The vacuum bag 118 may be of appropriate size to fully cover the open-side of the mold 102. In some examples, the vacuum bag 118, in the form of a film or the like, may be sealed to edges of the mold 102 with some sealant, such as sealant tape (like, a sealant tape 120 as shown in FIG. 1) to create a closed system. The sealant, like the sealant tape 120, are used to provide a vacuum tight seal between the vacuum bag 118 and the mold 102. Further at step 204, the method 200 includes evacuating air from the mold 102. This involves activating the vacuum pump 104 to suck any air from the mold 102. In one or more examples, the mold 102 is sealed to generate pressure of less than 10 millibars therein. In a preferred embodiment, the partial vacuum pressure is less than 1 millibar in the sealed mold 102.
[0042] At step 206, the method 200 includes preparing a mixture having siliceous particles mixed with the resin material. In particular, the siliceous particles are dispersed in the resin material. As discussed earlier, the resin material may include one or more of epoxy, vinylester, cyanoester, bismalmeide, polyimide, polyamide, polyacrylate polyester and phenol formaldehyde based polymers. Further, in the present examples, the siliceous particles may include, but not limited to, one or more of halloysite, delaminated clays, diatomaceous earth and nano-clay. Herein, the siliceous particles are in the form of siliceous nanoparticles with diameters, generally, less than 500 nanometers which are well known in the art and thus have not been described herein. In one or more embodiments, the siliceous particles are mixed with the resin material in a weight percentage range of 0.01 to 10 %.
[0043] In some examples, preparing the mixture further comprises mixing the siliceous particles with a hardener material. Herein, the hardener material is used as a curing component. Further, the hardener material is used to increase the resilience of the mixture once it sets. The hardener material further acts as a catalyst in the chemical reaction that occurs during the mixing process. Examples of the hardener material includes, but not limited to, anhydride-based, amine-based, polyamide, aliphatic and cycloaliphatic epoxy hardeners. In one embodiment, the mixture is prepared by mechanically stirring the siliceous particles with one or more of the resin material and the hardener material in a temperature range of 20-35 °C. It may be appreciated that the mixture may be prepared in the reservoir 108 itself. This ensures that the dispersion is uniform and agglomeration is limited.
[0044] At step 208, the method 200 includes infusing the plurality of reinforcing fibers with the prepared mixture in the sealed mold 102 until substantially complete impregnation thereof. In some examples, an infusion mesh (such as the infusion mesh 116 as shown in FIG. 1) is placed in the mold 102 such that the mixture, when introduced in the mold 102, passes through the infusion mesh 116 while entering the mold 102 to facilitate substantially even spreading of the mixture in the mold 102 to be in contact with the plurality of reinforced fibers therein. In the present examples, the catalyzed, low viscosity resin mixture is drawn from the reservoir 108 into the mold 102 aided by the vacuum, displacing the air at the edgesuntil the mold 102 is filled, and is, thereby, infused with the reinforcing fibers in the mold 102. In one or more embodiments, the plurality of reinforcing fibers are infused with the mixture in the sealed mold 102 in a temperature range of 25-45 °C. Also, in one or more embodiments, the infusion process is carried out at a relative humidity of 25 to 55 %. Further, in one or more embodiments, the infusion process is carried out for a period ranging from 1 minute to 2 hours. It may be appreciated that the given parameters are exemplary only, and shall not be construed as limiting to the present disclosure.
[0045] At step 210, the method 200 includes curing the impregnated reinforcing fibers. The curing process involves first pre-curing the impregnated reinforcing fibers for 1-4 hours in a temperature range of 50-70 °C. Further, the curing process involves post-curing the impregnated reinforcing fibers for 5-10 hours in a temperature range of 60-90 °C. It may be appreciated by a person skilled in the art that the pre- and post- curing steps all curing to take place at higher temperatures in order to enhance the physical and performance properties of the cured product formed thereby, while also resulting in longer life of the mold 102. In one or more embodiments, a bleeder fabric (such as, the bleeder fabric 106 as shown in FIG. 1) is arranged in the mold 102 to facilitate removal of air and volatiles from within the vacuum bag 118 during the curing process. The bleeder fabric 106 may further help to absorb excess resin present in the lay-ups in the mold 102.
[0046] At step 212, the method 200 includes de-molding cured product from the mold 102. The cured product is de-molded resulting into a finished product of desired dimensions and geometry. Herein, the cured product may be formed as the desired fiber reinforced composite article. For instance, in the present examples, the cured product is a blade of a wind turbine. The resultant product has composition in which the siliceous material ranges from 0.01-10 % by weight of the resin material with the hardener material, and the volume fraction of the reinforcing fibers in the resin material matrix varies from 40-70 %.
[0047] As discussed earlier, a release film (such as, the release film 114 as shown in FIG. 1) may facilitate removal of the cured product from the mold 102. The release film 114 may help in the release of the cured product from the mold 102 easily and further obtain a smooth surface finish for the cured product. It may be contemplated by a person skilled in the art that the release film 114 may further help with removal of the air bubbles and aid with the flow of the resin material in the mold 102.
[0048] Thereby, the present disclosure provides the fiber-reinforced composite article, such as the blade of a wind turbine, with the composition including a resin material; a plurality of unidirectional glass reinforcing fibers suspended in the epoxy resin material, wherein the reinforcing fibers are in the range of 40-70 % by volume fraction in the composition; anda plurality of siliceous particles uniformly dispersed and infused with the unidirectional glass fibers in the epoxy resin material, wherein the siliceous particles are in the range of 0.01-10 % by weight in the composition. It will be appreciated that although the present examples describe the disclosed composition to be used for manufacturing of the blade of the wind turbine, the same composition can also be implemented for manufacturing of, but not limited to, bodies of automobiles, furniture, kitchen appliances, etc.without any limitations.
[0049] In the present case of blades for the wind turbine, which are primarily plastic based composites, the thermosetting polymers such epoxy resin, act as a matrix and glass fiber as reinforcement. It may be understood that the reinforcing glass fiber becomes the main load-carrying component in the composites and gives high strength and stiffness as well as resistance to bending and breaking under the applied stresses. Since, the matrix holds the reinforcements together and has lower strength than the reinforcements; it becomes a critical strength controlling parameter prior to the reinforcements fracture. The addition of low density siliceous material like halloysite, delaminated clay and/or diatomaceous earth, when uniformly dispersed in the matrix,makes the blade tougher by increasing the strength and fatigue lifethereof. The present composition and manufacturing method also increase the strength to weight ratio of the blade structure by reducing the glass fabric layer requirement. This allows to manufacture the bladeswith thinner sections while still maintaining the required strength for its desired applications for both land-based and offshore wind turbine systems.
[0050] In the present embodiments, the siliceous particles can be of any morphology exhibiting 1D, 2D and/or 3D structures and are crucial to prevent the crack propagation from the matrix to the reinforcements across the interface, thereby improving the fracture toughness and fatigue properties of the blade. FIG. 3 illustrates a schematic presentation of crack propagation (shown in white) in pristine glass fiber reinforced epoxy composite as known in the art under tension. Further, FIG. 4 illustrates a schematic presentation of crack propagation (shown in white) in the siliceous material embedded glass fiber reinforced epoxy composite of the present disclosure under tension. As may be seen, in the first scenario of FIG. 3 (i.e. conventional composite materials), the crack length from fibers through epoxy matrix is less as compared to second scenario of FIG. 4 (i.e. the siliceous material embedded glass fiber reinforced epoxy composite of the present disclosure) where the crack deflection and resistance from the siliceous materials (represented by the numeral 402), suspended in the resin material (represented by the numeral 404), comes into picture which limits the crack propagation to the glass fibers (represented by the numeral 406), and thus strengthens the formed compositearticle.
[0051] It may be contemplated that usually strength of a composite material along the direction of applied stress is governed by the ultimate strain of the fibers. The initial failure that is most likely to happen is a fiber break which is accompanied by loss of effective fiber length and high interfacial shear stress near the break. This fiber break is followed by failure in the surrounding matrix, i.e., transverse cracking in the matrix extending up to surface. As the load increases the size of these failure sites remains relatively unchanged but their number increases throughout the composite causing cumulative weakening. Ultimate failure occurs when the number of localized fractures increases to provide a weak path for complete fracture to occur. The presence of siliceous materials in the epoxy matrix of the presently disclosed composite material can delay the fracture. Since these siliceous material are relatively stiff material (higher elastic modulus compare to epoxy), the crack initiation in the epoxy can be delayed by resisting or deflecting the crack (by increasing the crack propagation length) as schematically represented in FIG. 4. This mechanism can improve the strength and fatigue like of the composite material, as thereby of the fiber reinforced composite article, such as a blade of a wind turbine, formed therefrom.
[0052] It may be appreciated that as blades grow larger in size, the idea of forming structural areas of the blade instead from glass to significantly lighter and stiffer composite materials make sense. Currently, the most widely used composite materials use carbon fibers which are mainly introduced in the spar sections, or structural segments, of blades of the wind turbines longer than 45m for both land-based and offshore systems. The high stiffness and low density of carbon fiber gives an advantage of making thinner blades which are stronger and lighter. Carbon fibers can offer at least 20 percent weight reduction when moving from an all-glass blade to one with a carbon fiber-reinforced spars. However, as discussed earlier, these carbon fibers based composite materials have higher upfront cost (e.g., 10 to 20 times higher than glass). Besides the use of carbon fibers also brings new processing challenges as well. For instance, carbon requires perfect fiber alignment, and must be cured quickly. Small misalignments can lead to a significant reduction of compressive and fatigue strength. Further, achieving carbon fiber wet-out during vacuum infusion is difficult resulting in the use of more expensive prepreg products.
[0053] In contradistinction, the siliceous fillers have shown to trigger significant properties improvement when introduced in fiber reinforced polymer materials in which they are dispersed. Amongst those properties, a large increase in stiffness, tensile and fatigue strength, toughness and impact properties are achieved at filler contents as low as 1% weight. The present disclosed manufacturing method provide light-weight siliceous material embedded glass fiber reinforced epoxy composite material with low density, and high durability at a fraction of cost of making the carbon-fiber based composite. As discussed, the present high performance material can include polymers like epoxy, cyanoester, bismalmeide, polyimide, vinylester, polyamide, polyacrylate, and others as matrix in the carbon fiber-reinforced or glass fiber-reinforced composite. Further, the fillers for the matrix may include one or two or all, of the following siliceous components, such as hallyosite, delaminated clay and/or diatomaceous earth, nano-clays which are low-density material.
[0054] Thus, it may be concluded that the addition of siliceous materials in glass fiber reinforced composite, as disclosed in the present disclosure, improves the strength and fatigue life which will be used in part or full for blade structures. Due to the increased strength to weight ratio of the composite material, the blades could be made light-weight compared to traditional blade structures. Further, the fatigue strength of the blades will increase. The present manufacturing process is also cost-effective because the number fabric layer required would be less for comparable increase in the strength with respect to the traditional blade structures.
[0055] The foregoing descriptions of specific embodiments of the present disclosure have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the present disclosure to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The exemplary embodiment was chosen and described in order to best explain the principles of the present disclosure and its practical application, to thereby enable others skilled in the art to best utilize the present disclosure and various embodiments with various modifications as are suited to the particular use contemplated.