Patent Description:
The general inventive concepts described herein relate to fiber reinforced composite materials and, more particularly, to unidirectional laminates with improved tensile and fatigue performance.

<NPL>) relates to the influence of specimen type and reinforcement on measured tension-tension fatigue life of unidirectional GFRP laminates.

Reinforcement fibers are used in a variety of products. The fibers can be used as reinforcements in products such as laminates, reinforced paper and tape, and woven products. During the fiber forming and collecting process, numerous fibers are bundled together as a strand. Several strands can be gathered together to form a fiber bundle used to reinforce a polymer matrix to provide structural support to products, such as molded plastic products.

Reinforcing glass strands are conventionally prepared by mechanically drawing molten glass streams flowing by gravity from multiple orifices of bushings filled with molten glass to form filaments which are gathered together into base strands, and then collected. During the drawing of the glass filaments, and before they are gathered together into strands, the glass filaments are often coated with a sizing composition, generally an aqueous sizing composition, using a rotating roller. The sizing composition (also referred to as "size") is traditionally applied during manufacture of the glass filaments to protect the filaments from the abrasion resulting from the rubbing of the filaments at high speed during the forming and subsequent processes, thus acting as lubricant. It also makes it possible to remove or avoid electrostatic charges generated during this rubbing. Additionally, during the production of reinforced composite materials, the size improves the wetting of the glass and the impregnation of the strand by the material to be reinforced.

After the reinforcing fibers are produced, they are frequently processed on looms or other weaving devices to produce reinforcement fabrics. Many reinforcement fabrics include lengthwise fibers (warp fibers) arranged side by side and substantially parallel to one another, along with cross-wise fibers (weft fibers). Unidirectional fabrics are fabrics with at least approximately <NUM>% of the total fibers in a single direction, generally in the warp direction, also known as the load direction of the laminate. Accordingly, if a unidirectional fabric includes weft fibers, they generally account for less than <NUM>% of the total fibers in the fabric and provide a backing structure to allow for the knitting/stitching of the fabric, thus providing a stable textile structure.

As noted above, the fabric is useful for forming fiber-reinforced structural components. For example, the fabric can be stacked up or otherwise layered to form a spar cap of a blade of a wind energy turbine. In particular, several layers of fabric may be arranged on top of each other to form a laminate-structural component. The fabric layers are arranged within specific areas and regions of a mold. An infusion process introduces a curable matrix material (a resin) into the mold in order to penetrate the layers of the fabric. A vacuum can be applied to the mold during the infusion process to press the layers together and aid the resin in penetrating the layers. Once sufficiently infused through the fabric, the resin is allowed to harden forming the structural component.

Components that employ such a fiber-reinforcement generally require high tensile and fatigue properties. For example, a spar cap of a blade of a wind energy turbine must withstand near constant stress from significant forces (e.g., wind, centripetal force) during its usable lifespan. There remains a need for increasing the modulus of a laminate over a range of fiber weight fraction (FWF), while maintaining or increasing fatigue performance.

In one aspect, the invention provides a unidirectional laminate comprising a glass fiber reinforced composite material, characterized in that: the reinforced composite material has a main relaxation temperature (Tα) in a range between <NUM> and <NUM>. The composite comprises a plurality of unidirectional reinforcement fibers coated with a sizing composition and a matrix resin. The unidirectional laminate has a tensile modulus of at least <NUM> GPa at a fiber volume fraction greater than or equal to <NUM>% and fatigue mechanical performance of at least <NUM> MPa at <NUM> cycles, measured according to ASTM E <NUM>-<NUM>. The reinforcement fibers are glass fibers.

In one embodiment, the unidirectional laminate may comprise a fiber reinforced composite material having a storage modulus drop (ΔE') between about <NUM> and <NUM> GPa, said composite comprising a plurality of unidirectional reinforcement fibers coated with a sizing composition and a matrix resin, wherein the unidirectional laminate has a tensile modulus of at least <NUM> GPa at a fiber volume fraction greater than or equal to <NUM>% and fatigue mechanical performance of at least <NUM> MPa at <NUM> cycles, measured according to ASTM E <NUM>-<NUM>.

In one embodiment, the unidirectional laminate may comprise a fiber reinforced composite material having a main relaxation temperature (Tα) in a range between about <NUM> and <NUM> and a storage modulus drop (ΔE') between about <NUM> and <NUM> GPa, said composite comprising a plurality of unidirectional reinforcement fibers coated with a sizing composition and a matrix resin, wherein the unidirectional laminate has a tensile modulus of at least <NUM> GPa at a fiber volume fraction greater than or equal to <NUM>% and fatigue mechanical performance of at least <NUM> MPa at <NUM> cycles, measured according to ASTM E <NUM>-<NUM>.

The reinforcement fibers are glass fibers. The glass fibers may have an elastic modulus of at least <NUM> GPa. Optionally, the glass fibers may have an elastic modulus of at least <NUM> GPa. Optionally, the glass fibers may have an elastic modulus of at least <NUM> GPa. The glass fibers may have tensile strength of at least <NUM>,<NUM> MPa.

In some exemplary embodiments, the glass fibers may have a glass composition comprising oxides selected from one or more of the group consisting of: SiO<NUM>, Al<NUM>O<NUM>, MgO and CaO. In some exemplary embodiments, the glass fibers may have a glass composition comprising oxides selected from one or more of the group consisting of: SiO<NUM>, Al<NUM>O<NUM>, MgO, CaO, Na<NUM>O, TiO<NUM>, Fe<NUM>O<NUM> and Li<NUM>O.

In some exemplary embodiments, the glass fibers may have a glass composition comprising from approximately <NUM>% by weight to approximately <NUM>% by weight SiO<NUM>. Optionally, the glass composition may comprise from approximately <NUM>% by weight to approximately <NUM>% by weight SiO<NUM>. Optionally, the glass composition may comprise from approximately <NUM>% by weight to approximately <NUM>% by weight SiO<NUM>.

In some exemplary embodiments, the glass fibers may have a glass composition comprising from approximately <NUM>% by weight to approximately <NUM>% by weight Al<NUM>O<NUM>. Optionally, the glass composition may comprise from approximately <NUM>% by weight to approximately <NUM>% by weight Al<NUM>O<NUM>. Optionally, the glass composition may comprise from approximately <NUM>% by weight to approximately <NUM>% by weight Al<NUM>O<NUM>.

In some exemplary embodiments, the glass fibers may have a glass composition comprising from approximately <NUM>% by weight to approximately <NUM>% by weight MgO. Optionally, the glass composition may comprise from approximately <NUM>% by weight to approximately <NUM>% by weight MgO. Optionally, the glass composition may comprise from approximately <NUM>% by weight to approximately <NUM>% by weight MgO.

In some exemplary embodiments, the ratio of the weight percent of Al<NUM>O<NUM> and MgO in the glass composition may be no greater than <NUM>. Optionally, the ratio of the weight percent of Al<NUM>O<NUM> and MgO in the glass composition may be no greater than <NUM>. Optionally, the ratio of the weight percent of Al<NUM>O<NUM> and MgO in the glass composition may be no greater than <NUM>.

In some exemplary embodiments, the glass fibers may have a glass composition comprising from approximately <NUM>% by weight to approximately <NUM>% by weight CaO. Optionally, the glass composition may comprise from approximately <NUM>% by weight to approximately <NUM>% by weight CaO. Optionally, the glass composition may comprise from approximately <NUM>% by weight to approximately <NUM>% by weight CaO.

In some exemplary embodiments, the ratio of the weight percent of MgO to CaO in the glass composition is at least <NUM>. Optionally, the ratio of the weight percent of MgO to CaO in the glass composition is at least <NUM>.

In some exemplary embodiments, the glass fibers may have a glass composition comprising approximately <NUM>% by weight to approximately <NUM>% by weight Na<NUM>O. Optionally, the glass composition may comprise from approximately <NUM>% by weight to approximately <NUM>% by weight Na<NUM>O. Optionally, the glass composition may comprise from approximately <NUM>% by weight to approximately <NUM>% by weight Na<NUM>O. Optionally, the glass composition may comprise no more than <NUM>% by weight Na<NUM>O. Optionally, the glass composition may comprise no more than <NUM>% by weight Na<NUM>O.

In some exemplary embodiments, the glass fibers may have a glass composition comprising approximately <NUM>% by weight to approximately <NUM>% by weight TiO<NUM>. Optionally, the glass composition may comprise from approximately <NUM>% by weight to approximately <NUM>% by weight TiO<NUM>. Optionally, the glass composition may comprise from approximately <NUM>% by weight to approximately <NUM>% by weight TiO<NUM>. Optionally, the glass composition may comprise no more than <NUM>% by weight TiO<NUM>.

In some exemplary embodiments, the glass fibers may have a glass composition comprising approximately <NUM>% by weight to approximately <NUM>% by weight Fe<NUM>O<NUM>. Optionally, the glass composition may comprise from approximately <NUM>% by weight to approximately <NUM>% by weight Fe<NUM>O<NUM>. Optionally, the glass composition may comprise from approximately <NUM>% by weight to approximately <NUM>% by weight Fe<NUM>O<NUM>. Optionally, the glass composition may comprise no more than <NUM>% by weight Fe<NUM>O<NUM>. Optionally, the glass composition may comprise no more than <NUM>% by weight Fe<NUM>O<NUM>. Optionally, the glass composition may comprise no more than <NUM>% by weight Fe<NUM>O<NUM>.

In some exemplary embodiments, the glass fibers may have a glass composition comprising no more than <NUM>% by weight Li<NUM>O. Optionally, the glass composition may comprise no more than <NUM>% by weight Li<NUM>O. Optionally, the glass composition may comprise no more than <NUM>% by weight Li<NUM>O.

In some exemplary embodiments, the glass fibres may have a glass composition comprising from approximately <NUM>% by weight to approximately <NUM>% by weight SiO<NUM>, from approximately <NUM>% by weight to approximately <NUM>% by weight Al<NUM>O<NUM>, from approximately <NUM>% by weight to approximately <NUM>% by weight MgO, and from approximately <NUM>% by weight to approximately <NUM>% by weight CaO. In some exemplary embodiments, the glass fibres may have a glass composition comprising from approximately <NUM>% by weight to approximately <NUM>% by weight SiO<NUM>, from approximately <NUM>% by weight to approximately <NUM>% by weight Al<NUM>O<NUM>, from approximately <NUM>% by weight to approximately <NUM>% by weight MgO, from approximately <NUM>% by weight to approximately <NUM>% by weight CaO, no more than <NUM>% by weight Na<NUM>O, no more than <NUM>% by weight TiO<NUM>, no more than <NUM>% by weight Fe<NUM>O<NUM>, and no more than <NUM>% by weight Li<NUM>O.

In some exemplary embodiments, the sizing composition comprises an epoxy film former, a silane package, one or more lubricants, and an anti-static agent. In some exemplary embodiments, the sizing composition further includes one or more thermoplastic co-film formers. The thermoplastic co-film formers may be selected from one or more of the group consisting of: an unsaturated polyester co-film former, a functionalized epoxy polyvinyl acetate (PVAc) co-film former, and a polyvinyl pyrrolidone (PVP) co- film former. The thermoplastic co-film former in the sizing composition may be present in an amount from about <NUM> to about <NUM> wt. In some exemplary embodiments, the sizing composition further includes a boron-containing compound.

Additionally, in some exemplary embodiments, the reinforced composite has a storage modulus drop (ΔE') between about <NUM> and <NUM> GPa.

In one embodiment, the unidirectional laminate may comprise:.

wherein the reinforcement fibers are glass fibers having a glass composition comprising from approximately <NUM>% by weight to approximately <NUM>% by weight SiO<NUM>, from approximately <NUM>% by weight to approximately <NUM>% by weight Al<NUM>O<NUM>, from approximately <NUM>% by weight to approximately <NUM>% by weight MgO, and from approximately <NUM>% by weight to approximately <NUM>% by weight CaO, and wherein the sizing composition comprises an epoxy film former, a silane package, one or more lubricants, and an anti-static agent.

However, it should be appreciated that the glass fibers and sizing composition may be selected from any of the glass fibers and sizing compositions as described herein.

In another aspect, the invention provides a wind turbine blade comprising the claimed unidirectional laminate including a plurality of unidirectional reinforcement fibers coated with a sizing composition, and a cured matrix resin. The unidirectional laminate has a modulus of at least <NUM> GPa at a fiber volume fraction greater than or equal to <NUM>% and fatigue mechanical performance of at least <NUM> MPa at <NUM> cycles, measured according to ASTM E <NUM>-<NUM>.

The reinforcement fibers are glass fibers. The glass fibers may have an elastic modulus of at least about <NUM> GPa, including at least about <NUM> GPa, or at least about <NUM> GPa. The glass fibers may have tensile strength of at least <NUM>,<NUM> MPa.

In some exemplary embodiments, the sizing composition comprises an epoxy film former, a silane package, one or more lubricants, and an anti-static agent. In some exemplary embodiments, the sizing composition further includes one or more thermoplastic co-film formers, such as, for example, an unsaturated polyester co-film former, a functionalized epoxy polyvinyl acetate (PVAc) co-film former, or a polyvinyl pyrrolidone (PVP) co- film former. The thermoplastic co-film former in the sizing composition may be present in an amount from about <NUM> to about <NUM> wt. In some exemplary embodiments, the sizing composition further includes a boron-containing compound.

The features and embodiments as described herein apply to each and every aspect and each and every embodiment thereof mutatis mutandis.

Numerous other aspects, advantages, and/or features of the invention will become more readily apparent from the following detailed description of exemplary embodiments and from the accompanying drawings.

The invention, as well as embodiments and advantages thereof, are described below in greater detail, by way of example, with reference to the drawings in which:.

Various exemplary embodiments will now be described more fully, with occasional reference to the accompanying drawings. These exemplary embodiments may, however, be embodied in different forms and should not be construed as being limited to the descriptions set forth herein. Rather, these exemplary embodiments are provided so that this disclosure will be thorough and complete, and will convey the invention to those skilled in the art.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which these exemplary embodiments belong. The terminology used in the description herein is for describing particular exemplary embodiments only and is not intended to be limiting of the exemplary embodiments.

As used in the specification and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

Unless otherwise indicated, all numbers expressing quantities of ingredients, reaction conditions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term "about. " Accordingly, unless indicated to the contrary, the numerical parameters set forth in the specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the present exemplary embodiments. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should be construed in light of the number of significant digits and ordinary rounding approaches.

Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the exemplary embodiments are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements. Every numerical range given throughout this specification and claims will include every narrower numerical range that falls within such broader numerical range, as if such narrower numerical ranges were all expressly written herein. Moreover, any numerical value reported in the Examples may be used to define either an upper or lower end-point of a broader compositional range disclosed herein.

Wind power and the use of wind turbines have gained increased attention as the quest for alternative energy sources continues. Wind power is considered by many to be a clean and environmentally friendly energy source. With an increasing attention towards generating more energy from wind power, technological advances in the art have allowed for increased sizes of wind turbines and new designs of wind turbine components. However, as the physical sizes and availability of wind turbines increase, so does the need to design components that balance high strength-to-weight ratios and long component lifespan to further allow wind power to be cost-competitive with other energy sources.

The size, shape, and weight of the turbine blades contribute significantly to the cost and energy efficiencies of wind turbines. An increase in blade size and decrease in blade weight generally increases the energy efficiency of a wind turbine. However, increasing the size of the blade also contributes to additional forces associated with operation of the turbine. This increase in forces leads to increased strain and fatigue on the components of the blade which, in turn, decreases the lifespan of the blade.

The structural makeup of a wind turbine blade is comprised of a matrix, often a cured resin, and a reinforcement material. The reinforcement material is comprised of a fibrous fabric. Reinforcement fibers used in the manufacture of materials for wind turbine blades include glass fibers, carbon fibers, and mixtures thereof. It is known in the art that bare glass fibers are not compatible with many common resins. That is, the resin will not cure to form a bond with the glass. The resulting composite material will include both materials, but without a strong bond between the two materials, the composite will not perform as well. This issue is overcome by applying a "sizing" to the glass prior to exposing the glass to the resin.

A sizing is a chemical composition (often a liquid, or aqueous composition) that is applied to the surface of the glass during production of glass fibers. The sizing may serve many purposes, one of which being to form a chemical "bridge" between the resin and the surface of the glass, making the two chemically compatible with one another and facilitating bonding between the resin and the glass which, in turn, will form a stronger composite material. Thus, a sizing will include chemical functional groups, one of which interacts with the glass, and another that interacts with the resin.

The invention is based, at least in part, on the discovery that tensile and fatigue properties of a unidirectional laminate are governed by key viscoelastic properties of unidirectional composites, such as, for example, main relaxation temperature Tα (f = <NUM>) and storage modulus drop ΔE' (defined as E' glassy - E' rubbery, normalized to <NUM>% fiber weight fraction (FVF)). These viscoelastic properties can be tuned in various ways, such as by use of a high modulus glass fiber, a particular sizing chemistry, or a combination thereof. In some exemplary embodiments, particularly optimized viscoelastic properties are achieved by the use of a high modulus glass fiber in combination with a high-performance sizing chemistry. By optimizing the viscoelastic properties of a unidirectional composite, a unidirectional laminate may be produced with a modulus of at least <NUM> GPa at a fiber weight fraction (FWF) greater than or equal to <NUM>% and fatigue mechanical performance (stress level extrapolated at <NUM> cycles) measured according to ISO <NUM> (testing) and ASTM E <NUM>-<NUM> (data analysis) of at least <NUM> MPa.

In some exemplary embodiments, the unidirectional fabrics include one or more reinforcement fibers, which may comprise glass fibers, carbon fibers, or hybrid mixtures of glass and carbon fibers. In some exemplary embodiments, the reinforcement fibers comprise glass fiber bundles used in continuous or discontinuous form. In some exemplary embodiments, the reinforcement fiber bundles comprise continuous fibers in the form of unbroken filaments, threads, strands, yarns, or rovings.

The glass may be any conventional glass composition, such as, for example, silica-based glass, borosilicate glasses such as E-glass, high-strength glass such as S-glass; H-glass, R-glass, E-type glass with lower amounts of boron or boron-free glass, E-CR glass, (e.g., Advantex® glass available from Owens Corning), and high modulus glass.

The reinforcement fibers may have an average diameter ranging from about <NUM> microns to about <NUM> microns, including between about <NUM> microns and <NUM> microns, and between about <NUM> microns and <NUM> microns, and between about <NUM> and <NUM> microns. The reinforcement fibers may comprise one or more fiber bundles having a bundle tex of about <NUM> to about <NUM>, including about <NUM> to about <NUM>, and about <NUM> to about <NUM>. In some exemplary embodiments, the reinforcement fibers have an average diameter of <NUM> microns to <NUM> microns. In some exemplary embodiments, the reinforcement fibers have a bundle tex of <NUM> to <NUM> tex. In some exemplary embodiments, the reinforcement fibers have an average diameter of <NUM> microns to <NUM> microns and a bundle tex of <NUM> to <NUM> tex.

As mentioned above, one way to tune the viscoelastic properties of a unidirectional laminate is to select a high modulus glass fiber. By 'high modulus glass fiber," it is meant a glass fiber that achieves an elastic modulus of at least about <NUM> GPa, measured in accordance with the sonic measurement procedure outlined in the report "<NPL>. In some exemplary embodiments, the high modulus glass fiber has an elastic modulus of at least about <NUM> GPa, at least about <NUM> GPa, at least about <NUM> GPa, and at least about <NUM> GPa.

The high modulus glass fiber may be of the type described in <CIT>.

In some exemplary embodiments, the glass composition comprises about <NUM> to about <NUM> % by weight SiO<NUM>, about <NUM> to about <NUM> % by weight Al<NUM>O<NUM>, about <NUM> to about <NUM> % by weight MgO, about <NUM> to about <NUM> % by weight CaO, about <NUM> to about <NUM> % by weight Na<NUM>O, <NUM> to about <NUM> % by weight TiO<NUM>, <NUM> to about <NUM> % by weight Fe<NUM>O<NUM>, and no more than <NUM> % by weight Li<NUM>O. Advantageously, the ratio of the weight percent of alumina oxide and magnesium oxide (Al<NUM>O<NUM>/MgO) is no greater than <NUM>, such as no greater than <NUM>, and no greater than <NUM>. Additionally, the ratio of the weight percent of magnesium oxide to calcium oxide (MgO/CaO) is advantageously at least <NUM>.

In some exemplary embodiments, the glass composition may comprise about <NUM> to about <NUM> % by weight SiO<NUM>, about <NUM> to about <NUM> % by weight Al<NUM>O<NUM>, about <NUM> to about <NUM> % by weight MgO, about <NUM> to about <NUM> % by weight CaO, about <NUM> to about <NUM> % by weight Na<NUM>O, <NUM> to about <NUM> % by weight TiO<NUM>, <NUM> to about <NUM> % by weight Fe<NUM>O<NUM>, and no more than <NUM> % by weight Li<NUM>O. In some exemplary embodiments, the glass composition includes an Al<NUM>O<NUM>/MgO ratio less than <NUM> and an MgO/CaO ratio of at least <NUM>.

In some exemplary embodiments, the glass composition may comprise about <NUM> to about <NUM> % by weight SiO<NUM>, about <NUM> to about <NUM> % by weight Al<NUM>O<NUM>, about <NUM> to about <NUM> % by weight MgO, about <NUM> to about <NUM> % by weight CaO, about <NUM> to about <NUM> % by weight Na<NUM>O, <NUM> to about <NUM> % by weight TiO<NUM>, <NUM> to about <NUM> % by weight Fe<NUM>O<NUM>, and no more than <NUM> % by weight Li<NUM>O. In some exemplary embodiments, the glass composition includes an Al<NUM>O<NUM>/MgO no greater than <NUM> and an MgO/CaO ratio of at least <NUM>.

The glass composition includes at least <NUM> % by weight, but no greater than <NUM> % by weight SiO<NUM>. Including greater than <NUM> % by weight SiO<NUM> causes the viscosity of the glass composition to increase to an unfavorable level. Moreover, including less than <NUM> % by weight SiO<NUM> increases the liquidus temperature and the crystallization tendency. In some exemplary embodiments, the glass composition includes at least <NUM> % by weight SiO<NUM>, including at least <NUM> % by weight, at least <NUM> % by weight, at least <NUM> % by weight, and at least <NUM> % by weight. In some exemplary embodiments, the glass composition includes no greater than <NUM> % by weight SiO<NUM>, including no greater than <NUM> % by weight, no greater than <NUM> % by weight, no greater than <NUM> % by weight, no greater than <NUM> % by weight, and no greater than <NUM> % by weight.

In some exemplary embodiments, the glass composition has an Al<NUM>O<NUM> concentration of at least <NUM> % by weight and no greater than <NUM> % by weight. Including greater than <NUM> % by weight Al<NUM>O<NUM> causes the glass liquidus to increase to a level above the fiberizing temperature, which results in a negative ΔT. Including less than <NUM> % by weight Al<NUM>O<NUM> forms a glass fiber with an unfavorably low modulus. In some exemplary embodiments, the glass composition includes at least <NUM> % by weight Al<NUM>O<NUM>, including at least <NUM> % by weight, at least <NUM> % by weight, at least <NUM> % by weight, and at least <NUM> % by weight.

The glass composition advantageously includes at least <NUM> % by weight and no greater than <NUM> % by weight MgO. Including greater than <NUM> % by weight MgO will cause the liquidus temperature to increase, which also increases the glass's crystallization tendency. Including less than <NUM> % by weight forms a glass fiber with an unfavorably low modulus if substituted by CaO and an unfavorable increase in viscosity if substituted with SiO<NUM>. In some exemplary embodiments, the glass composition includes at least <NUM> % by weight MgO, including at least <NUM> % by weight, at least <NUM> % by weight, at least <NUM> % by weight, at least <NUM> % by weight, at least <NUM> % by weight, at least <NUM> % by weight, and at least <NUM> % by weight MgO.

Another important aspect of the subject glass composition that makes it possible to achieve the desired mechanical and fiberizing properties, is having an Al<NUM>O<NUM>/MgO ratio of no greater than <NUM>. It has been discovered that glass fibers having compositions with otherwise similar compositional ranges, but with Al<NUM>O<NUM>/MgO ratios greater than <NUM>, are unable to achieve tensile strengths of at least <NUM>,<NUM> MPa. In certain exemplary aspects, the combination of an Al<NUM>O<NUM> concentration of at least <NUM> % by weight and an Al<NUM>O<NUM>/MgO ratio of no greater than <NUM>, such as no greater than <NUM>, and no greater than <NUM>, makes it possible to obtain glass fibers with desirable fiberizing properties and tensile strengths of at least <NUM>,<NUM> MPa.

The glass composition advantageously includes at least <NUM> % by weight and no greater than <NUM>% by weight CaO. Including greater than <NUM> % by weight CaO forms a glass with a low elastic modulus. Including less than <NUM> % by weight will either unfavorably increase the liquidus temperature or viscosity depending on what the CaO is substituted with. In some exemplary embodiments, the glass composition includes at least <NUM> % by weight CaO, including at least <NUM> % by weight, at least <NUM> % by weight, at least <NUM> % by weight, and at least <NUM> % by weight.

In some exemplary embodiments, the combined amounts of SiO<NUM>, Al<NUM>O<NUM>, MgO, and CaO in the glass composition is at least <NUM> % by weight, or at least <NUM> % by weight, and no greater than <NUM> % by weight. In some exemplary embodiments, the combined amounts of SiO<NUM>, Al<NUM>O<NUM>, MgO, and CaO is between <NUM> % by weight and <NUM> % by weight, including between <NUM> % by weight and <NUM> % by weight and <NUM> % by weight and <NUM> % by weight.

In some exemplary embodiments, the total concentration of MgO and CaO in the glass composition is at least <NUM> % by weight and no greater than <NUM> % by weight, including between <NUM> % by weight and <NUM> % by weight and between <NUM> % by weight and <NUM> % by weight. In some exemplary embodiments, the total concentration of MgO and CaO is at least <NUM> % by weight.

The glass composition may include up to about <NUM> % by weight TiO<NUM>. In some exemplary embodiments, the glass composition includes about <NUM> % by weight to about <NUM> % by weight TiO<NUM>, including about <NUM> % by weight to about <NUM> % by weight and about <NUM> to about <NUM> % by weight.

The glass composition may include up to about <NUM> % by weight Fe<NUM>O<NUM>. In some exemplary embodiments, the glass composition includes about <NUM> % by weight to about <NUM> % by weight Fe<NUM>O<NUM>, including about <NUM> % by weight to about <NUM> % by weight and about <NUM> to about <NUM> % by weight.

In some exemplary embodiments, the glass composition includes less than <NUM> % by weight of the alkali metal oxides Na<NUM>O and K<NUM>O, including between <NUM> and <NUM> % by weight. The glass composition may advantageously include both Na<NUM>O and K<NUM>O in an amount greater than <NUM> % by weight of each oxide. In some exemplary embodiments, the glass composition includes about <NUM> to about <NUM> % by weight Na<NUM>O, including about <NUM> to about <NUM> % by weight, about <NUM> to about <NUM> % by weight, and <NUM> to about <NUM> % by weight. In some exemplary embodiments, the glass composition includes about <NUM> to about <NUM> % by weight K<NUM>O, including about <NUM> to about <NUM> % by weight, about <NUM> to about <NUM> % by weight, and <NUM> to about <NUM> % by weight.

As used herein, the terms "weight percent," "% by weight," "wt. %," and "percent by weight" may be used interchangeably and are meant to denote the weight percent (or percent by weight) based on the total composition.

The glass compositions may be free or substantially free of B<NUM>O<NUM>, Li<NUM>O, and fluorine, although either, or any, may be added in small amounts to adjust the fiberizing and finished glass properties and will not adversely impact the properties if maintained below several percent. As used herein, substantially free of B<NUM>O<NUM>, Li<NUM>O, and fluorine means that the sum of the amounts of B<NUM>O<NUM>, Li<NUM>O, and fluorine present is less than <NUM> % by weight of the composition. The sum of the amounts of B<NUM>O<NUM>, Li<NUM>O, and fluorine present may be less than about <NUM> % by weight of the composition, including less than about <NUM> % by weight, less than about <NUM> % by weight, and less than about <NUM> % by weight.

The glass compositions may further include impurities and/or trace materials without adversely affecting the glasses or the fibers. These impurities may enter the glass as raw material impurities or may be products formed by the chemical reaction of the molten glass with furnace components. Non-limiting examples of trace materials include zinc, strontium, barium, and combinations thereof. The trace materials may be present in their oxide forms and may further include fluorine and/or chlorine. In some exemplary embodiments, the inventive glass compositions contain less than <NUM> % by weight, including less than <NUM> % by weight, less than <NUM> % by weight, and less than <NUM> % by weight of each of BaO, SrO, ZnO, ZrO<NUM>, P<NUM>O<NUM>, and SO<NUM>. Particularly, the glass composition may include less than about <NUM> % by weight of BaO, SrO, ZnO, ZrO<NUM>, P<NUM>O<NUM>, and/or SO<NUM> combined, wherein each of BaO, SrO, ZnO, ZrO<NUM>, P<NUM>O<NUM>, and SO<NUM> if present at all, is present in an amount of less than <NUM> % by weight.

The fiber tensile strength is also referred herein simply as "strength. " In some exemplary embodiments, the tensile strength is measured on pristine fibers (i.e., unsized and untouched laboratory produced fibers) using an Instron tensile testing apparatus according to ASTM D2343-<NUM>. Exemplary glass fibers formed form the above described inventive glass composition may have a fiber tensile strength of at least <NUM>,<NUM> MPa, including at least <NUM>,<NUM> MPa, at least <NUM>,<NUM> MPa, at least <NUM>,<NUM> MPa, at least <NUM>,<NUM> MPa, at least <NUM>,<NUM> MPa, at least <NUM>,<NUM> MPa, at least <NUM>,<NUM> MPa, at least <NUM>,<NUM> MPa, and at least <NUM>,<NUM> MPa. In some exemplary embodiments, the glass fibers formed from the above described composition have a fiber tensile strength of from about <NUM> to about <NUM> MPa, including about <NUM> MPa to about <NUM>,<NUM>, about <NUM>,<NUM> to about <NUM>,<NUM> MPa.

The glass fibers may be formed by any means known and traditionally used in the art. In some exemplary embodiments, the glass fibers are formed by obtaining raw ingredients and mixing the ingredients in the appropriate quantities to give the desired weight percentages of the final composition.

The components of the glass composition may be obtained from suitable ingredients or raw materials including, but not limited to, sand or pyrophyllite for SiO<NUM>, limestone, burnt lime, wollastonite, or dolomite for CaO, kaolin, alumina or pyrophyllite for Al<NUM>O<NUM>, dolomite, dolomitic quicklime, brucite, enstatite, talc, burnt magnesite, or magnesite for MgO, and sodium carbonate, sodium feldspar or sodium sulfate for the Na<NUM>O. In some exemplary embodiments, glass cullet may be used to supply one or more of the needed oxides.

In some exemplary embodiments, the continuous glass fibers are formed by drawing molten glass filaments from a bushing and coating the glass filaments with a sizing composition prior to gathering the glass filaments into a bundle, forming a fiber bundle.

When a high modulus glass fiber, having an elastic modulus of at least <NUM> GPa, is used in the unidirectional laminate, the sizing composition may comprise any conventional sizing composition known in the art, such as Owens Corning sizing compositions: SE <NUM>, WS <NUM>, WS2000, WS3200, and SE1200.

However as mentioned above, to allow for a wider variety of glass fiber compositions to be used in manufacturing a unidirectional laminate, another way to tune the viscoelastic properties of a composite is by way of a high-performance sizing chemistry, such as that disclosed in <CIT>.

The high-performance sizing composition described herein may be used with any glass composition, while still demonstrating improved viscoelastic properties. In some exemplary embodiments, the high-performance sizing composition includes an epoxy film former, a silane package that includes an aminosilane coupling agent and an epoxy silane coupling agent, one or more lubricants, and an antistatic agent. In some exemplary embodiments, the high-performance sizing composition includes an epoxy film former, a silane package that includes an aminosilane coupling agent and an epoxy silane coupling agent, one or more lubricants, an antistatic agent, and at least one acid. In addition, the high-performance sizing composition may also contain a polyurethane or epoxy/polyurethane film former.

In some exemplary embodiments, the high-performance sizing composition includes an epoxy film forming polymer component. The epoxy film forming polymer component of the sizing composition may include epoxy resin emulsions that contain a low molecular weight epoxy resin and at least one surfactant. The film former functions to protect the fibers from damage during processing and imparts compatibility of the fibers with the matrix resin. In some exemplary embodiments, the epoxy resin has a molecular weight from <NUM>-<NUM> and an epoxy equivalent weight from <NUM>-<NUM>, or a molecular weight <NUM>-<NUM> and an epoxy equivalent weight from <NUM>-<NUM>, and or a molecular weight of <NUM>-<NUM> and an epoxy equivalent weight from <NUM>-<NUM>. "Epoxy equivalent weight", as used herein, is defined by the molecular weight of the epoxy resin divided by the number of epoxy groups present in the compound. Useful epoxy resins contain at least one epoxy or oxirane group in the molecule, such as polyglycidyl ethers of polyhydric alcohols or thiols. Examples of suitable epoxy film forming resins include Epon® <NUM> (available from Hexion Specialties Chemicals Incorporated), DER <NUM> (available from Dow Chemicals), Araldite <NUM> (available from Huntsman), and Epotuf <NUM>-<NUM> (available from Reichhold Chemical Co) and similar commercial emulsions like , Epi-rez <NUM>-w-<NUM> and Epi-rez <NUM>-w-<NUM> both from Hexion.

In some exemplary embodiments, the high-performance sizing composition includes one or more thermoplastic co-film formers, such as, for example, unsaturated polyester co-film former, functionalized epoxy polyvinyl acetate (PVAc) co-film formers, and polyvinyl pyrrolidone (PVP) co- film formers, such as Resyn <NUM> from Celanese & PVP K90 from Ashland, respectively. In some exemplary embodiments, the co-film former is present in the sizing composition in an amount from about <NUM> to about <NUM> wt. % solids, based on the total solid content of the sizing composition. In some exemplary embodiments, the co-film former is present in the sizing composition in an amount from about <NUM> to about <NUM> wt. In some exemplary embodiments, the co-film former is present in the sizing composition in an amount from about <NUM> to about <NUM> wt.

Examples of suitable surfactants for use in the epoxy resin emulsion include, but are not limited to, Triton X-<NUM>, an octylphenoxypolyethoxyethanol (available from Union Carbide Corp. ), Pluronic P103, an ethylene oxide/propylene oxide block copolymer (available from BASF), Pluronic F77, an ethylene oxide/propylene oxide block copolymer (available from BASF), Pluronic 10R5, an ethylene oxide/propylene oxide block copolymer (available from BASF), a block copolymer of ethylene oxide and propylene oxide such as Pluronic L101 (available from BASF), a polyoxyethylene-polyoxypropylene block copolymer such as Pluronic P105 (available from BASF), and an ethylene oxide/propylene oxide copolymer (available from BASF). Preferably, the epoxy resin emulsion contains two or more surfactants. In a preferred embodiment, a combination of (<NUM>) a block copolymer of ethylene oxide and propylene oxide and (<NUM>) a polyoxyethylene-polyoxypropylene block copolymer (such as Pluronic L101 and Pluronic P105) is used in the epoxy resin emulsion. The surfactant or surfactants may be present in the epoxy resin emulsion in an amount from <NUM>-<NUM>%, or in an amount of from <NUM>-<NUM>%, such as, for example about <NUM>%.

In various exemplary embodiments, the epoxy resin emulsion is present in the high-performance sizing composition in an amount from about <NUM> to about <NUM>% by weight solids, such as, for example, from about <NUM>-<NUM>% by weight solids.

The surfactants, plasticizing agents, and dispersing agents may include aliphatic or aromatic polyalkoxylated compounds that are optionally halogenated, such as ethoxylated/propoxylated alkylphenols or ethoxylated/propoxylated fatty alcohols. These polyalkoxylated compounds can be block or random copolymers; amine-comprising compounds, for example amines, which are optionally alkoxylated, amine oxides, alkylamides, succinates and taurates, sugar derivatives, in particular of sorbitan, alkyl sulphates, which are optionally alkoxylated, alkyl phosphates and ether phosphates, which are optionally alkylated or alkoxylated. The sizing compositions may also include antistatic agents, such as specific organic cationic or non-ionic agents, such as fatty quaternary amines or imidazolinium derivatives, to avoid static electricity accumulation due to friction on guiding devices, such as ceramic guiding eyes.

The total amount of surfactant, plasticizing agent, dispersing agent, or combinations thereof in the high-performance sizing composition (dry solids content) may be in the range from about <NUM>% by weight to about <NUM>% by weight, or from about <NUM>% by weight to about <NUM>% by weight of the dry solids content. In some exemplary embodiments, a surfactant is present in about <NUM>% to <NUM>% by weight of solids content. In some exemplary embodiments, a plasticizer is present in <NUM> to about <NUM>% by weight of solids content. In some exemplary embodiments, a dispersing agent is present in about <NUM>% to <NUM>% by weight of solids content. In some exemplary embodiments, antistatic agents are present in <NUM> to <NUM>% by weight of solids content.

The coupling agent facilitates the adhesion of the size to the surface of the glass by inducing covalent bond with the film forming agents. The coupling agents may further generate covalent bonding or at least an interpenetrated network with the polymeric matrix in the case of non-reactive polymeric matrix. Another function of the coupling agents is to form a polysiloxane layer on the glass fiber that improves the durability in aggressive aging conditions like in wet, acidic or high temperature environment. The coupling agent may be a hydrolysable compound, for example a compound which can be hydrolyzed in the presence of an acid, such as acetic, lactic, citric, formic, tartaric, oxalic acids.

In one exemplary embodiment, the coupling agent comprises a silane package that includes at least one aminosilane coupling agent and at least one epoxy silane coupling agent. The coupling agents used in the silane package of the size composition may have hydrolyzable groups that can react with the glass surface to remove unwanted hydroxyl groups and one or more groups that can react with the film-forming polymer to chemically link the polymer with the glass surface. In particular, the coupling agents preferably include <NUM>-<NUM> hydrolyzable functional groups that can interact with the surface of the glass fibers and one or more organic groups that are compatible with the polymer matrix.

Suitable coupling agents for use in the silane package have a readily hydrolyzable bond to a silicon atom of the silane, or hydrolysis products thereof. Silane coupling agents which may be used in the present size composition may be characterized by the functional groups amino, epoxy, azido, vinyl, methacryloxy, ureido, and isocyanato. In addition, the coupling agents may include an acrylyl or methacrylyl group linked through non-hydrolyzable bonds to a silicon atom of the silane.

Coupling agents for use in the silane package include monosilanes containing the structure Si(OR)<NUM>, where R is an organic group such as an alkyl group. Lower alkyl groups such as methyl, ethyl, and isopropyl are preferred. Silane coupling agents function to enhance the adhesion of the film forming agent to the glass fibers and to reduce the level of fuzz, or broken fiber filaments, during subsequent processing. Examples of suitable aminosilane coupling agents for use in the silane package include, but are not limited to aminopropyltriethoxysilane (A-<NUM> from GE Silicones), N-β-aminoethyl-γ-aminopropyltrimethoxysilane (A-<NUM> from GE Silicones), N-phenyl-γ-aminopropyltrimethoxysilane (Y-<NUM> from GE Silicones), and bis-γ-trimethoxysilylpropylamine (A-<NUM> from GE Silicones). Preferably, the aminosilane coupling agent is aminopropyltriethoxysilane (A-<NUM> from GE Silicones). The amino silane coupling agent may be present in the high-performance sizing composition in an amount from <NUM>-<NUM>% by weight solids, such as in an amount from <NUM>-<NUM>% by weight solids. Although not wishing to be bound by theory, it is believed that the presence of a minimal amount of aminosilane coupling agent in the sizing composition improves the mechanical properties of the final product. Too much aminosilane coupling agent added to the sizing composition may deteriorate mechanical properties.

Non-limiting examples of suitable epoxy silane coupling agents include a glycidoxy polymethylenetrialkoxysilane such as <NUM>-glycidoxy-<NUM>-propyl-trimethoxysilane, an acryloxy or methacrylyloxypolymethylenetrialkoysilane such as <NUM>-methacrylyloxy-<NUM>-propyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane (A-<NUM> available from GE Silicones), γ-methacryloxypropyltrimethoxysilane (A-<NUM> available from GE Silicones), α-chloropropyltrimethoxysilane (KBM-<NUM> available from Shin-Etsu Chemical Co. ), α-glycidoxypropylmethyldiethoxysilane (A-<NUM> available from GE Silicones), and vinyl-tris-(<NUM>-methoxyethoxy)silane (A-<NUM> from available GE Silicones). In at least one preferred embodiment, the epoxy silane coupling agent is γ-glycidoxypropyltrimethoxysilane (A-<NUM>) described above. The use of methacryloxy silanes such as A-<NUM> improves the compatibility of the sized fibers with vinyl ester and polyester resins. The epoxy silane coupling agent may be present in the sizing composition in an amount from <NUM>-<NUM>% by weight solids, or from <NUM>-<NUM>% by weight solids, or from <NUM>-<NUM>% by weight solids.

Additionally, the high-performance sizing composition contains at least one non-ionic lubricant. The non-ionic lubricant in the sizing composition acts as a "wet lubricant" and provides additional protection to the fibers during the filament winding process. In addition, the non-ionic lubricant helps to reduce the occurrence of fuzz. Especially suitable examples of non-ionic lubricants include PEG <NUM> Monolaurate (a polyethylene glycol fatty acid ester commercially available from Cognis) and PEG <NUM> Monooleate (Cognis). Other non-limiting examples include a polyalkylene glycol fatty acid such as PEG <NUM> Monostearate (a polyethylene glycol monostearate available from Cognis), PEG <NUM> Monostearate (Cognis), PEG <NUM> Monooleate (Cognis), and PEG <NUM> Monolaurate (Cognis). In a most preferred embodiment, the non-ionic lubricant is PEG <NUM> Monolaurate. The non-ionic lubricant may be present in the size composition in an amount from approximately <NUM>-<NUM>% by weight solids, preferably from <NUM>-<NUM>% by weight solids.

In addition to the non-ionic lubricant, the high-performance sizing composition also contains at least one cationic lubricant and at least one antistatic agent. The cationic lubricant aids in the reduction of interfilament abrasion. Suitable examples of cationic lubricants include, but are not limited to, a polyethyleneimine polyamide salt commercially available from Cognis under the trade name Emery <NUM>, a stearic ethanolamide such as Lubesize K-<NUM> (AOC), Cirrasol 185AE (Unichemie), and Cirrasol 185AN (Unichemie). The amount of cationic lubricant present in the sizing composition is preferably an amount sufficient to provide a level of the active lubricant that will form a coating with low fuzz development. In at least one exemplary embodiment, the cationic lubricant is present in the size composition in an amount from <NUM>-<NUM>% by weight solids, preferably from <NUM>-<NUM>% by weight solids. Antistatic agents especially suitable for use herein include antistatic agents that are soluble in the sizing composition. Examples of suitable antistatic agents include compounds such as Emerstat™ 6660A and Emerstat™ <NUM> (quaternary ammonium antistatic agents available from Emery Industries, Inc. ), and Larostat 264A (a quaternary ammonium antistatic agent available from BASF), tetraethylammonium chloride, and lithium chloride. Antistatic agents may be present in the sizing composition in an amount from <NUM>-<NUM>% by weight solids, preferably from <NUM>-<NUM>% by weight solids.

The total amount of the cationic lubricant and the antistatic agent that is present in the size composition may range from <NUM>-<NUM>% by weight solids, preferably from <NUM>-<NUM>% by weight solids. In some exemplary embodiments, the amount of cationic lubricant and antistatic agent present in the sizing composition is an amount that is less than or equal to approximately <NUM>% by weight solids.

Further, the high-performance sizing composition may contain a small amount of at least one weak organic acid. Although not wishing to be bound by theory, it is believed that citric acid, a conventional acid additive for sizing compositions used to adjust the pH, may prematurely open the epoxy groups in the film formers and epoxy silanes if used in large amounts during the drying of the glass fibers, which may result in a reduction of mechanical properties. A trace amount of acetic acid, formic acid, succinic acid, and/or citric acid may be added to the inventive sizing composition to hydrolyze the silane in the coupling agent without prematurely opening the epoxy groups. In some exemplary embodiments, the organic acid is acetic acid. The organic acid (such as acetic acid) may be present in the size composition in an amount from <NUM>-<NUM>% by weight solids, or from <NUM>-<NUM>% by weight solids.

In addition, the high-performance sizing composition may contain a boron-containing compound that is capable of providing boron atoms to the size composition. It is hypothesized that the boron atoms released from the boron-containing compound act with the aminosilane at the glass interface to assist in adhering the remaining sizing components to the glass fiber. The combination of a boron containing compound such as boric acid in the sizing composition, together with an aminosilane (e.g., A-<NUM>), and an epoxy silane (e.g., A-<NUM>), improves the mechanical properties of the final product. Non-limiting examples of suitable boron-containing compounds include boric acid and borate salts such as boron oxide, sodium tetraborate, potassium metaborate, potassium tetraborate, ammonium biborate, ammonium tetrafluoroborate, butylammonium tetrafluoroborate, calcium tetrafluoroborate, lithium fluoroborate, potassium tetrafluoroborate, sodium tetrafluoroborate, tetrabutylammonium tetrafluoroborate, tetraethylammonium tetrafluoroborate, and zinc tetrafluoroborate. In some exemplary embodiments, the boron-containing compound is boric acid. The boron-containing compound may be present in the sizing composition in an amount from <NUM>-<NUM>% by weight solids, such as from <NUM>-<NUM>% by weight solids, or from <NUM>-<NUM>% by weight solids.

The combination of the organic acid (e.g., acetic acid) and boric acid in the size composition desirably imparts a pH from <NUM>-<NUM>, such as a pH from <NUM>-<NUM> to the sizing composition.

Optionally, the high-performance sizing composition may contain a polyurethane film former such as Baybond <NUM> (Bayer), Baybond PU403 (Bayer), and W-<NUM> (Chemtura) or an epoxy/polyurethane film former such as Epi-Rez <NUM>-W-<NUM> (Hexion Specialties Chemicals Incorporated).

The polyurethane film former increases strand integrity and the mechanical fatigue performance by toughening the resin/size interphase. The toughened resin interphase results in a final composite product that has an improved resistance to cracking and has increased or improved mechanical properties such as improved strength. The urethane film former may be present in the sizing composition an amount from about <NUM> to about <NUM>% by weight solids, such as an amount from <NUM>-<NUM>% by weight solids, or about <NUM>% by weight solids. Suitable polyurethane dispersions include polyurethane emulsions such as Hydrosize® U1-<NUM>, U1-<NUM>, U2-<NUM>, U4-<NUM>, U5-<NUM>, U6-<NUM>, U6-<NUM> and U7-<NUM> available from Hydrosize® Technologies, Inc (Raleigh, N.

The high-performance sizing composition further includes water to dissolve or disperse the active solids for coating. Water may be added in amounts sufficient to dilute the aqueous sizing composition to a viscosity that is suitable for its application to glass fibers and to achieve the desired solids content on the fibers. The mix solids content of the size may be from about <NUM> to about <NUM>%, such as from about <NUM> to about <NUM>%, or from about <NUM> to about <NUM>%. In some exemplary embodiments, the sizing composition may contain up to approximately <NUM>% water.

The high-performance sizing composition may optionally include one more additives. In some exemplary embodiments, the additives include fire retardants, nanoparticles, lubricants, such as a fatty acid ester, a fatty alcohol, fatty amine salts, a mineral oil, or mixtures thereof; complexing agents, such as an EDTA derivative, a gallic acid derivative or a phosphonic acid derivative; antifoaming agents, such as a silicone or a vegetable oil; a polyol; an acid used to control the pH during the hydrolysis of the coupling agent, for example acetic acid, lactic acid or citric acid; cationic polymers; emulsifiers; viscosity modifiers; stabilizers; acids; and other bases.

In some embodiments, the total content of additives in the sizing composition is in the range from about <NUM> to about <NUM>% by weight, in some embodiments from <NUM> to <NUM>% by weight (dry extract solids content).

A conventional system <NUM> for forming a structural laminate made from a composite material, will be described with reference to <FIG>. In the system <NUM>, a machine <NUM> continuously produces a fiber reinforced material in the form of an infusible fabric <NUM>. The fabric includes substantially unidirectional fibers, meaning that at least <NUM>% of the fibers extend in a single direction (generally in the warp direction). In some exemplary embodiments, the fabric is a <NUM>% unidirectional fabric. In some exemplary embodiments, the fabric includes less than <NUM>% weft fibers, or less than <NUM>% weft fibers, or less than <NUM>% weft fibers. In some exemplary embodiments, the fabric includes <NUM>% unidirectional fibers and is free of weft fibers.

As noted above, the fabric <NUM> includes unidirectional fibers that extend substantially along a length of the fabric <NUM> (i.e., parallel to the arrow <NUM>). As the fabric <NUM> exits the machine <NUM> and travels in a direction indicated by the arrow <NUM>, the fabric <NUM> is wound at a roll area <NUM>. A winder or other conveying means pulls the fabric <NUM> from the machine <NUM> to the roll area <NUM>. Blades or other cutting means form slits <NUM> in the fabric <NUM> prior to the roll area <NUM>. In this manner, discrete rolls <NUM> of the fabric <NUM> are formed.

Once a predetermined quantity of the fabric <NUM> has been wound to the roll area <NUM>, a manual cut <NUM> is made across the width of the fabric <NUM>, thereby separating the rolls <NUM> from the fabric <NUM> exiting the machine <NUM>. When it is time to form the laminate, one or more rolls <NUM> are layered into a mold (not pictured). Once a desired thickness and shape is obtained within the mold, a resin is introduced, such as by an infusion process, and cured to form a laminate.

In certain embodiments, the matrix resin is comprised of a resin selected from: polyester resins, vinylester resins, polyurethane resins, a bio-based resin, and a styrene-free resin.

The unidirectional laminate has a high fiber loading of at least <NUM>% fiber weight fraction (FWF), or at least <NUM>% by volume, or at least <NUM>% by volume. In some exemplary embodiments, the unidirectional laminate has a fiber weight fraction of at least <NUM>%, such as at least <NUM>%, at least <NUM>%, or at least <NUM>% by volume.

In certain exemplary embodiments, the invention relates to the discovery of a correlation between fatigue performance and tensile modulus of a unidirectional laminate and the viscoelastic properties of the composite material making up the laminate. Accordingly, by tuning the viscoelastic properties of a composite material, fatigue performance and tensile modulus of a unidirectional laminate produced therefrom is optimized.

The particular viscoelastic properties in question include the composite's main relaxation temperature (Tα) and storage modulus drop (ΔE'). These viscoelastic properties are governed by the glass composition, glass fiber/matrix interface properties, resin type, and manufacturing process. If at least these viscoelastic properties are tuned within specific ranges, high tensile modulus (at least about <NUM> MPa) and fatigue performance are achieved in unidirectional laminates at a fiber volume fraction of at least <NUM>% by volume.

The particular composite viscoelastic properties include tuning the composite's main relaxation temperature (Tα) to a range between about <NUM> and <NUM>, such as between <NUM> and <NUM>, <NUM> and <NUM>, <NUM> and <NUM>, and <NUM> and <NUM>. Optionally, the composite's main relaxation temperature (Tα) may be in a range between about <NUM> and <NUM>. Additionally, the storage modulus drop (ΔE') is tuned to achieve a modulus between about <NUM> and <NUM> GPa, including between about <NUM> GPa and <NUM> GPa, and <NUM> and <NUM> GPa. Optionally, the composite's storage modulus drop (ΔE') may be between about <NUM> and <NUM> GPa. By selecting materials that achieve the above defined viscoelastic properties, a unidirectional laminate may be formed having a tensile modulus of at least about <NUM> GPa and a fatigue performance of at least <NUM> MPa at <NUM> cycles. In some exemplary embodiments, the unidirectional laminate formed by meeting the above-described viscoelastic properties have a tensile modulus of at least <NUM> GPa, including at least <NUM> GPa, at least <NUM> GPa, at least <NUM> GPa, at least <NUM> GPa, and at least <NUM> GPa. In some exemplary embodiments, the unidirectional laminate formed by meeting the above-described viscoelastic properties have a fatigue performance of at least <NUM> MPa, or at least <NUM> MPa, or at least <NUM> MPa, or at least <NUM> MPa, at <NUM> cycles.

The following paragraphs describe and demonstrate exemplary embodiments of the high fatigue and modulus unidirectional laminate. The exemplary embodiments are provided solely for the purpose of illustration and are not to be construed as limitations of the present disclosure, as many variations thereof are possible without departing from the spirit and scope of the present disclosure.

<FIG> graphically illustrates the relationship between laminate modulus and the laminate fiber volume fraction, using both a theoretical and experimental model. The theoretical modulus was calculated based on the law of mixtures using EH-Glass = <NUM> Gpa; ENGH-Glass = <NUM> Gpa; Ematrix = <NUM> Gpa in the following equation: <MAT>.

Where Ef represents the modulus of the fibers, Em represents the modulus of the matrix and Vf represents the volume fraction of the fibers.

As illustrated in <FIG>, at a FVF between <NUM>% and <NUM>%, the laminates demonstrated a <NUM>° Young's modulus between about <NUM> GPa and <NUM> GPa, under both the theoretical and experimental models.

Unidirectional fiberglass reinforced polyester laminates with thicknesses of about <NUM> were obtained by vacuum infusion of filament wound continuous reinforcements composed of <NUM>-micron diameter single fibers. The laminates were cured for <NUM> hours at room temperature and the post-cured for <NUM> hours at <NUM>. The laminates were vacuum infused with a resin system. The resin system is defined as a medium reactive orthophthalic polyester resin with relatively high heat resistance and mechanical properties. Typical resin cast properties for this material are a tensile modulus of <NUM> GPa and a tensile elongation between <NUM>% and <NUM>%.

Dynamic mechanical analysis (DMA) was conducted on coupons measuring <NUM> (l) x <NUM> (w) using the <NUM>-point bending mode. Temperature sweep parameters included a frequency of <NUM> and a temperature range of <NUM>/min. The amplitude was set to ensure measurements within the linear viscoelasticity domain. Typical DMA scans for this type of laminate range from <NUM> to <NUM>. Tα was determined on tanδ curve (peak maximum).

High fatigue performances (at least <NUM> GPa after <NUM> Cycle, per ASTM E <NUM>-<NUM> were achieved when the reinforcement was optimized by tuning the glass composition and/or the size chemistry, impacting the viscoelastic properties in the following ranges: Tg between <NUM> and <NUM>, ΔE' between <NUM> and <NUM> GPa.

Such tuned viscoelastic properties are illustrated in <FIG> illustrates the range of DMA properties, Tα and ΔE'. The Tα is the position of the peak on the tanδ curve. The ΔE NORM is the E' glassy - E' rubbery, normalized to <NUM>% FVF. As illustrated in <FIG>, the Tα is between a range of <NUM>-<NUM> at a ΔE' NORM of <NUM>-<NUM> GPa. In <FIG>, E" illustrates the loss modulus: loss response of the material.

The examples demonstrated that low fatigue values may be seen when one or a combination of the following factors: Tα greater than <NUM> C; FVF greater than <NUM>%, use of a sizing composition without an epoxy film former; and/or a sizing composition without boron salt.

All references to singular characteristics or limitations of the present disclosure shall include the corresponding plural characteristic or limitation, and vice versa, unless otherwise specified or clearly implied to the contrary by the context in which the reference is made.

All combinations of method or process steps as used herein can be performed in any order, unless otherwise specified or clearly implied to the contrary by the context in which the referenced combination is made.

The composite materials, structural components, and corresponding manufacturing methods of the present disclosure can comprise, consist of, or consist essentially of the essential elements and limitations of the disclosure as described herein, as well as any additional or optional components, or limitations described herein or otherwise useful in fiber-reinforced composite materials.

To the extent that the terms "include," "includes," or "including" are used in the specification or the claims, they are intended to be inclusive in a manner similar to the term "comprising" as that term is interpreted when employed as a transitional word in a claim. Furthermore, to the extent that the term "or" is employed (e.g., A or B), it is intended to mean "A or B or both A and B. " When the applicants intend to indicate "only A or B but not both," then the term "only A or B but not both" will be employed. Thus, use of the term "or" herein is the inclusive, and not the exclusive use.

Claim 1:
A unidirectional laminate comprising a glass fiber reinforced composite material, characterized in that:
the reinforced composite material has a main relaxation temperature (Tα) in a range between <NUM> and <NUM>, said composite comprising a plurality of unidirectional reinforcement fibers coated with a sizing composition and a matrix resin,
wherein the unidirectional laminate has a tensile modulus of at least <NUM> GPa at a fiber volume fraction greater than or equal to <NUM>% and fatigue mechanical performance of at least <NUM> MPa at <NUM> cycles, measured according to ASTM E <NUM>-<NUM>,
wherein the reinforcement fibers are glass fibers.