Hybrid three-dimensional woven/laminated struts for composite structural applications

ES 2 398 286 T3

DESCRIPTION

Hybrid Woven / Laminate 3-Dimensional Struts for Composite Structural Applications

Background of the invention

Field of the invention

The present invention relates to the geometric configuration of three-dimensional woven preforms for reinforced composite structures that have a quasi-isotropic or multidirectional reinforcement at one or two ends of the structure and an approximately unidirectional reinforcement in the rest of the areas.

Background of the invention

The use of reinforced composite materials to produce structural components is now widespread, particularly in applications in which their desirable characteristics of being light, strong, hard, thermally resistant, self-supporting and with adaptability to form and shape are sought. Such components are used, for example, in the aeronautical, aerospace, satellite and battery industries, as well as for recreational uses such as in boats and racing cars, and in countless other applications. A three-dimensional textile material generally consists of fibers oriented in three directions with each fiber extending along a direction perpendicular to the other fibers, that is, along the axial X, Y and Z directions.

Typically, the components formed from such textile materials consist of reinforcing materials embedded in matrix materials. The reinforcing component can be composed of materials such as glass, carbon, ceramic, aramid (eg, "KEVLAR®"), polyethylene, and / or other materials that exhibit physical, thermal, chemical, and / or other desired properties, among which it stands out a great resistance against stress failure. Through the use of such reinforcing materials, which ultimately become a constituent element of the completed component, the desired characteristics of the reinforcing materials such as very high strength are imparted to the completed composite component. The constituent reinforcing materials can typically be woven, knitted, or otherwise oriented into configurations and shapes desired for the reinforcing preforms. Usually, particular attention is paid to ensure optimal utilization of the properties for which these constituent reinforcing materials have been selected. Generally, such reinforcing preforms are combined with matrix material to form desired finished components or to produce work material for final production of the finished components.

Once a desired reinforcing preform has been constructed, the matrix material can be introduced and combined with the preform, so that the reinforcing preform comes to fit into the matrix material so that the matrix material fills the interstitial areas between the elements. constituents of the reinforcing preform. The matrix material can be any of a wide variety of materials, such as epoxy resin, polyester, vinyl ester, ceramic, carbon, and / or other materials, which also exhibit physical, thermal, chemical, and / or other desired properties. The materials chosen for use as the matrix may or may not be the same as those of the reinforcing preform and may or may not have comparable physical, chemical, thermal, or other properties. Normally, however, they will not be the same materials or have physical, chemical, thermal or other properties comparable to the reinforcing preform, since a common goal sought in the use of composite materials in the first place is to achieve a combination of characteristics in the finished product that cannot be achieved through the use of a constituent material alone.

When combined, the reinforcing preform and matrix material can then be cured and stabilized in the same operation by thermosetting or other known methods, and then subjected to other operations towards the production of the desired component. It is significant to note that after thus cured, the then solidified masses of the matrix material normally adhere very strongly to the reinforcing material (eg, the reinforcing preform). As a result, stress on the finished component, particularly through its matrix material acting as an adhesive between the fibers, can be effectively transferred to and carried by the constituent material of the reinforcing reinforcing preform.

Typically, unidirectional fibers or two-dimensional woven fabrics are produced by a material supplier and shipped to a customer who cuts patterns and laminates the final part fold by fold. The simplest woven materials are flat, substantially two-dimensional structures with fibers in only two directions. They are formed by interlacing two sets of threads perpendicular to each other. In two-dimensional weaving, the 0 ° yarns are called warp fibers or yarns and the 90 ° yarns are called weft or fill fibers or yarns. For resin transfer molding, a series of woven fabrics can be combined to form a dry laminate, which is placed in a mold and injected with resin. These fabrics can be preformed using either a "cut and sew" technique or they can be thermally formed and "basted".

ES 2 398 286 T3 using a resin binder.

Two-dimensional woven structures, however, have limitations. The preforming stage requires extensive manual work on layering. Two-dimensional woven structures are not as strong or resistant to elongation along axes other than 0 ° and 90 °, particularly at angles further away from the fiber axes. One method of reducing this possible limitation is to add cross fibers to the fabric, woven fibers that cut through the fabric at an intermediate angle, preferably ± 45 ° relative to the axis of the filler fibers.

Simple woven preforms are also single layer. This limits the possible strength of the material. One possible solution is to increase the size of the fiber. Another is to use multiple layers or pleats. An additional advantage of using multiple layers is that some layers can be oriented so that the warp and weft axes of different layers are in different directions, thereby acting like the crossed fibers discussed above. If these layers are a stack of individual layers laminated together with the resin, however, then the problem of exfoliation arises. If the layers are sewn together, then many of the woven fibers can be damaged during the sewing process and the overall tensile strength can suffer. Furthermore, for both lamination and multi-ply stitching, a laminating operation by hand is usually necessary to align the layers. Alternatively, the layers can be interwoven as part of the weaving process. The creation of multiple interwoven layers of textile material, particularly with integrated cross-fibers, has been a difficult problem.

An example of where composite materials are used to produce structural components is in the production of struts and tie rods. Struts and braces typically comprise a central column that has lugs at each end of the frame. These lugs can be either male or female (hairpin) configurations and are used to attach the strut or strut to the structure being reinforced or propped up. As discussed above, in order to achieve increased strength of the composite structure, multiple layers or pleats are used for the lug and column portions of the struts and struts. Although the use of multiple layers is advantageous since individual layers can be oriented to provide reinforcement in the 0 ° and 90 ° directions as well as they can be oriented diagonally to provide reinforcement in additional directions, such as the ± 45 ° directions, if laminated together with resin, exfoliation of the layers can be problematic. Alternatively, if the layers are stitched together, then as discussed above, many of the woven fibers can be damaged during the stitching process, reducing the overall tensile strength of the final structure.

There are many examples of laminated lugs, using some hybrid materials (i.e. alternating carbon and titanium pleats), but laminated lugs have not been combined with a three-dimensional woven column. The feasibility of laminated composite lugs for very highly loaded structures has been demonstrated in several government funded programs. However, to the applicant's knowledge, none of these programs considered the use of three-dimensional woven preforms.

Thus, three-dimensional preforms are desirable for use in struts and struts, having laminated lug ends or portions and a monolithic three-dimensional woven center column. The advantages of using a three-dimensional construction in the center of the preform are that it reduces the work required to cut and gather all the pleats required for a thick composite material and that it provides better tolerance to damage than conventional laminated composites. The advantage of separate end layers is that the laminate can be tailored to have specific properties.

US Patent Publication No. 4,739,798 describes a three-dimensional, non-corrugated, integrated woven reinforcement for structural components formed as an integrated woven assembly of warp and fill fibers, for example graphite fibers, in a multiplicity of layers, with lightweight bonding wire, for example fiberglass, that passes from one side of the laminated system to the other. Woven reinforcing shapes of various conformations such as a double T-beam can be produced using a specified percentage of 0 degree fibers (warp) and 90 degree fibers (fill), for example graphite, to form a plurality of layers comprising the web and the flanges of the double T-beam reinforcement, and which has the desired number of layers and the desired thickness in both the web and the flanges, and passing connecting wire, for example fiberglass, back and forth from one side of the web to the other, and in the same way from one side of the flanges to the other, and extending longitudinally in the warp direction of the material. The woven assembly is then impregnated with resin, for example "B" phase epoxy resin, placed in a suitable mold and heated and cured in the conventional manner.

US Patent Publication No. 4,622,254 describes a fiber material for reinforcing plastics prepared by laminating at least a first fiber substrate in which the reinforcing fibers extend in two directions including the longitudinal direction and the transverse direction that are cut into each other at a substantially right angle, with at least one second fiber substrate in which the reinforcing fibers extend in two directions including directions having angles of +/- (25-65) degrees relative to the direction

ES 2 398 286 T3 longitudinal. Or, a fiber material for reinforcing plastics prepared by laminating at least a first fiber substrate in which the reinforcing fibers extend in at least one of two directions including the longitudinal direction and the transverse direction intersecting each other at an angle. substantially straight, at least one second fiber substrate in which the reinforcing fibers extend in a direction having an angle of (2565) degrees relative to the longitudinal direction, and at least a third fiber substrate in which the reinforcing fibers extend in a direction having an angle of - (25-65) degrees relative to the longitudinal direction. The above rolled moldings are integrated with each other by repeatedly passing sewing threads in the rolling direction.

US Patent Publication No. US 2002/056484 describes a solid structural material using a three-dimensional five-axis woven fabric W. In weaving a three-dimensional five-axis woven textile W using a three-dimensional weaving machine, divisibly woven sections S1 are formed into parts of a three-dimensional five-axis woven textile material manufactured by alternately driving upper insertion elements 2, 3 and bottom to insert a vertical Z thread from above and below respectively, such that each of the insertion elements and a warp insertion needle are actuated at different times.

Accordingly, a need exists for a woven preform having an integrally woven three-dimensional center portion with laminated ear ends comprised of separate woven layers.

Summary of the invention

Therefore, a primary object of the invention is to provide a three-dimensional woven preform having an interwoven column portion and a stack of individually woven textiles at the ear ends for use in a composite structure.

A further object of the invention is to provide a woven preform for a thick composite structure having a quasi-isotropic or multidirectional reinforcement at one or two ends and a quasi-unidirectional reinforcement in the rest of the areas.

Still another object of the invention is to provide a composite structure that can be used to carry large concentrated loads.

These and other objects and advantages are provided by the present invention. In this regard, the present invention relates to a woven preform that is used to reinforce a composite structure according to claim 1 and to a method of manufacturing such a preform according to claim 9.

The various features of novelty which characterize the invention are pointed out with particularity in the claims appended to and forming a part of this description. For a better understanding of the invention, its operating advantages and specific objects achieved through its uses, reference is made to the accompanying descriptive content in which preferred embodiments of the invention are illustrated in the accompanying drawings in which the corresponding components are identified by the same reference numbers.

Brief description of the drawings

The following detailed description, given by way of example and not intended to limit the present invention solely thereto, will be better appreciated in conjunction with the accompanying drawings, in which like reference numerals indicate like elements and parts, in which:

Figure 1 is a plan view of a composite structure having a column portion with lug ends having a male configuration;

Figure 2 is a plan view of a composite structure having a column portion with lug ends having a female or hairpin configuration;

Figure 3 is a plan view of a blank constructed in accordance with one embodiment of the present invention;

Figure 4A is a plan view of a blank having lug ends with a symmetrical configuration constructed in accordance with one embodiment of the present invention;

Figure 4B is a plan view of a blank having lug ends with a symmetrical configuration constructed in accordance with one embodiment of the present invention;

Figure 4C is a plan view of a blank having lug ends with an asymmetric configuration constructed in accordance with one embodiment of the present invention;

Figure 4D is a plan view of a blank having lug ends with an asymmetrical configuration constructed in accordance with one embodiment of the present invention; and Figure 5 is a plan view of a blank constructed in accordance with one embodiment of the present invention.

Detailed description of the preferred embodiments

The present invention will now be more fully described hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention can, however, be carried out in many different ways and should not be considered limited to the illustrated embodiments set forth herein. Rather, these illustrated embodiments are provided so that this discussion is comprehensive and complete, and fully expresses the scope of the invention to those skilled in the art.

In the following description, like reference characters designate like or corresponding parts throughout the figures. Additionally, in the following description, terms such as "top", "bottom", "top" and "bottom" and the like are understood to be words of convenience and are not intended to be limiting terms.

The present invention is a preform concept for a composite structure or beam that has a quasi-isotropic or multidirectional reinforcement at one or two ends and a quasi-unidirectional reinforcement in the rest of the areas. This configuration is desirable for structures that have to carry large concentrated loads, such as struts and tie rods. The quasi-isotropic or multidirectional reinforced ends provide good supporting properties and balanced tension, compression and shear strength, making them good choices for the lug ends of the structure. These lug ends can have either male or female (hairpin) configurations. The unidirectional part provides high axial stiffness, which is good for preventing sagging or crippling of the column, making it a good choice for the main column of a strut or tie. In FIG. 1 a strut or strut 2 is shown having lug ends 4 and a three-dimensional main column portion 6. The lug ends 4 in Figure 1 have a male configuration. Figure 2 depicts a strut 8 with a three-dimensional main column portion 10 and lug ends 12 having a female or hairpin configuration.

The advantages of using a three-dimensional construction in the center of the preform are that it reduces the work required to cut and gather all the pleats required for a thick composite material and that it provides better tolerance to damage than conventional laminated composites. The advantage of the separate layers at the ends of the structure is that the laminate can be tailored to have specific properties. As disclosed, the lug ends are considered quasi-isotropically or multi-directionally reinforced, but could have virtually any laminated configuration.

The present preform comprises a three-dimensional woven part consisting of several layers and a similar number of independent diagonal layers. In the central or column part of the three-dimensional woven piece, all the layers are interwoven or woven integrally with each other forming a monolithic block of woven material. The fiber architecture used in this part can be any conventional pattern for a thick preform, including, but not limited to, pleat-to-pleat, through-thickness, angled interlocking, or orthogonal architectures. At the ends of the structure, the individual layers are woven independently of each other to form a stack of textile materials with reinforcement in the 0 ° and 90 ° directions, with 0 ° being along the length of the structure. Diagonal pleats or layers, which are constructed separately to provide reinforcement in additional directions to the 0 ° / 90 ° direction such as in the ± 45 ° direction, are sandwiched between the layers of textile materials at 0 ° / 90 ° to form a more conventional laminate material. The diagonal pleats or layers may be woven using warp and weft fibers or yarns or may be nonwoven, knitted, or a series of MD or CD fibers or yarns. In the following figures, the warp direction is along the 0 ° direction or along the length of the frame and is indicated by arrow 100.

All the layers that comprise the preform, including the central or column part, are woven with fibers or warp yarns and fibers or weft or fill yarns using a Jacquard loom and captured shuttle, however, any weaving technique can be used. conventional to weave the layers. The fibers or yarns can be either synthetic or natural materials such as, but not limited to, carbon, nylon, rayon, polyester, fiberglass, cotton, glass, ceramic, aramid ("KEVLAR®"), and polyethylene. The completed woven preform is then processed into a composite woven / laminated structure with the introduction of a matrix material such as, but not limited to, epoxy resin, polyester, vinyl ester, ceramic, carbon, and / or other materials, which also show physical, thermal, chemical and / or other desired properties, using

ES 2 398 286 T3 conventional techniques such as, but not limited to, resin transfer molding or vapor phase chemical infiltration.

According to one embodiment of the present invention, Figure 3 depicts a segment of a frame 14 having a thick central portion 16 that is integrated with two thinner male lug ends 18 that are positioned on each side of the central portion 16. As can be seen in Figure 3, the thick core 16 is a monolithic, three-dimensional woven column comprising a plurality of woven layers 20 that are interwoven or woven together. In order to form the thinner male lug ends 18, layers of warp fibers from the thick center column 16 are no longer woven from the preform to provide a tapered transition 22 from the column 16 to the narrower lug ends 18. thin.

Once the desired number of preform warp fiber layers have ceased to be woven to obtain the tapering section of the column to the desired ear thickness, additional layers of preform warp fibers are stopped weaving at the ends 18 thinner lugs to provide a gap or space for diagonal folds of textile material. The remaining warp fibers in the thinner lug ends 18, which are woven integrally with the plurality of layers 20 in the column or core 16 and are continuous along the length of the structure, form individual layers of pleats 24 that are woven independently of one another. This stack of pleats or textile materials provides reinforcement at the thinner ear ends 18 in the 0 ° and 90 ° directions. Since the pleats 24 at 0 ° / 90 ° are not interwoven, the diagonal pleats 26 that provide reinforcement in additional directions, such as the ± 45 ° direction, can be sandwiched in the gaps between the pleats 24 at 0 °. / 90 °, forming a stack of textile materials which, when a matrix material is applied, forms a laminated structure that provides quasi-isotropic or multidirectional reinforcement at the thinner lug ends 18. Furthermore, as depicted in FIG. 3, the structure has a continuous surface fiber 28 that is the result of the outermost warp fibers in the thick column 16.

If desired, unlike the structure disclosed above for this embodiment which has a central portion 16 with two thinner lug ends 18 on either side of the central portion 16, a frame may be constructed having only one end 18 of thinner lug according to the disclosed embodiment. In this case, the structure will comprise an end similar to the monolithic three-dimensional woven center portion 16 and a thinner ear end 18 as disclosed above. A structure constructed in this way will more closely resemble Figure 3.

Another embodiment of the present invention is depicted in Figures 4A-4D, which show a segment of a frame 30 comprising two lug ends 32 that are thicker than the monolithic three-dimensional woven center column portion 34 of frame 30 As in the case of the previous embodiment, the central column portion 34 comprises a plurality of woven layers 35 that are interwoven or woven together. In this configuration, however, there is no need to stop weaving warp fibers 36 from the column portion 34 in order to form the thicker ear ends 32. Instead, all of the warp fibers 36 used to construct the column portion 34 are used to construct the thicker ear ends 32. The warp fibers 36 from the column portion 24, however, are not interwoven together at the thicker ear ends 32. This allows the diagonal pleats 38 to be sandwiched between the warp fibers 40 at the thicker ear ends 32, which are the pleats that provide reinforcement in the 0 ° / 90 ° direction. Thus, the thicker lug ends 32 have a stack of textiles consisting of pleats or textiles oriented at 0 ° / 90 ° and separately constructed pleats oriented in other directions than the 0 ° / 90 ° direction, for example pleats or textiles oriented at ± 45 ° which, when a matrix material is applied, results in a laminated ear having a quasi-isotropic or multidirectional reinforcement. Furthermore, as can be seen in Figures 4A-4D, structures constructed in accordance with this embodiment will have a stepped transition 42 from the thicker rolled ear end 32 to the monolithic column portion 34, thereby enhancing load transfer from one part to the other.

As can be seen in Figures 4A-4D, the length and placement of the pleats 38 diagonally varies from figure to figure. Figures 4A and 4B depict a lug end 32 having a symmetrical configuration. That is, the length and placement of the diagonal folds 38 at the ear end 32 are symmetrical about the center line or longitudinal axis AA. Figure 4A depicts a symmetrical configuration in which the length of successive diagonal folds 38 increases in the upper half 39 and lower half 41 of the lug end 32 as one moves from the center line AA towards the upper surface 43 and the lower surface 45 of the ear end 32. Figure 4B depicts a symmetrical configuration in which the length of successive diagonal folds 38 decreases in both halves 39 and 41 of lug end 32 as one moves from center line AA toward upper surface 43 and lower surface 45 of the ear end 32.

Figures 4C and 4D depict a lug end 32 having an asymmetric configuration. That is, the length of successive diagonal folds 38 at lug end 32 only increases or decreases as one moves from lower surface 45 to upper surface 43 of lug end 32. Figure 4C shows an asymmetric configuration in which the length of successive diagonal folds 38 at the end 32 of

The lug increases as one moves from the lower surface 45 to the upper surface 43 of the lug end 32. As shown in FIG. 4D, an asymmetric lug end 32 can also be constructed in which the length of successive diagonal folds 38 decreases as one moves from the lower surface 45 towards the upper surface 43 of the lug end 32.

If desired, unlike the structures disclosed above for this embodiment which have a central portion 34 with two thicker lug ends 32 on each side of the central portion 34, a frame may be constructed having only one end 32 of thicker lug according to the disclosed embodiment. In this case, the structure will comprise a monolithic three-dimensional woven center-like end 34 and a thicker tab end 32 as described above. A structure constructed in this manner will more closely resemble the structures depicted in Figures 4A-4D.

In another embodiment of the present invention, Figure 5 depicts a segment of a frame 44 having a monolithic three-dimensional woven center column portion 46 with two female lugs or hairpins 48. As can be seen in Figure 5, the Female ear ends 48 are angled relative to center column portion 46 such that female ear ends 48 are not in line or collinear with center column portion 46. Similar to the previous embodiments, the center column portion 46 comprises a plurality of woven layers 50 that are interwoven or woven together. In order to form the female lug ends or hairpins 48, the monolithic column portion 46 is woven so that it branches 52 to form both halves of the hairpins. The 0 ° / 90 ° layers 54 in the first angled portion 56 of each fork half continue to interweave with each other.

In order to provide a gap between the reinforcing layers 58 at 0 ° / 90 ° for the folds 60 of textile material diagonally in the end or parallel parts 62 of the hairpin, the warp fibers of the parts 56 are no longer woven. angle of the preform. The remaining warp fibers in the lug ends 48, which are woven integrally with the plurality of layers 50 woven in the center column portion 46 and the angled portions 54, form individual layers that are woven independently of one another and provide reinforcement on fork 48 in the 0 ° and 90 ° directions. Since the 0 ° / 90 ° layers 58 are not interwoven with each other, reinforcement is provided in directions other than the 0 ° / 90 ° direction, for example in the ± 45 ° direction, by the diagonal folds 60 that they are sandwiched between the pleats 58 at 0 ° / 90 °, forming stacks of textile material in the forks that provide quasi-isotropic or multidirectional reinforcement when a matrix material is added to the preform.

If desired, unlike the structure disclosed above for this embodiment having a central portion 46 with two female lug ends or hairpins 48 on each side of the central portion 46, a structure having only one end 48 can be constructed. female lug according to the disclosed embodiment. In this case, the structure will comprise a monolithic three-dimensional woven center-like end 46 and a female ear or hairpin end 48 as disclosed above. A structure constructed in this way will more closely resemble the structure depicted in Figure 5.

In all disclosed embodiments, once the pleats are inserted diagonally into the ear ends, the woven preform can be overbraided with a pleat of glass material in order to improve the abrasion resistance of the preform.

As is apparent to those skilled in the art, the structures disclosed above can take many shapes in addition to those disclosed herein. For example, the structures may have a thick, monolithic, three-dimensional, woven column with female ear or hairpin configurations. The structure may also have a thick monolithic three-dimensional woven column with a male lug at one end and a female lug at the other end. In addition, the structure may have a thin monolithic three-dimensional woven column with female lugs at each end or a male lug at one end and a female lug at the other end. Finally, all configurations can have: both lugs in line with or collinear with the main column part; both lugs angled in relation to the main column part; or a lug can be collinear with the main part and a lug can be angled relative to the main part. Although as previously disclosed, the lug ends are considered to be quasi-isotropically or multi-directionally reinforced, the lug ends can have virtually any rolled configuration. Thus, the present structures, for example a strut or strut, can be designed to have different configurations in order to provide various types of reinforcement or shoring based on a specific structure need or desired use.

Although a preferred embodiment of the present invention and modifications thereof have been described in detail herein, it is to be understood that this invention is not limited to this embodiment and precise modifications, and that other modifications may be made by one skilled in the art. and variations without departing from the scope of the invention as defined in the appended claims.