Woven cross directions pdf free download

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You have already reported this. Clear Clear All. These data show that hydroentangling of a wet-laid aramid non-woven sheet from essentially binder-free aramid floc provides densification and additional strengthening of the sheet compared to a sheet that is not hydroentangled, such as the sheets in Examples An aqueous dispersion was made of para-aramid floc, and a wet-laid non-woven sheet was formed from this dispersion on a Deltaformer inclined wire machine.

The material was collected in wet form after leaving the wire and was hydroentangled on a pilot washing machine as in Examples The non-woven material was hydroentangled by consecutive treatment from both sides. One side was treated with water jets from eight manifolds, which had a 0. Another side was treated with water jets from four manifolds, which had a 0.

The properties of the hydroentangled non-woven sheets are shown in Table 3. These data show that wet-laid aramid non-woven sheets of the invention can be successfully hydroentangled before being dried.

Further, when compared with the data in Examples , these data show that the non-woven sheets of the invention can be hydroentangled before or after being dried and still provide acceptable physical properties. An aqueous dispersion was made of weight percent para-aramid floc, and a wet-laid non-woven sheet was formed from this dispersion in a handsheet mold and dried on a metal screen of mesh.

Afterwards, the sheet was hydroentangled, with preliminary wetting, on a pilot washing machine as in Examples The para-aramid floc used was from poly paraphenylene terephthalamide fiber sold by E.

One side was treated with water jets from four manifolds, which had a 0. The properties of the hydroentangled non-woven sheet are shown in Table 3. A wet-laid non-woven sheet was formed as in Example 15 except that the para-aramid floc used was made from poly para-phenylene terephthalamide fiber sold by E. Each side was treated with water jets from four manifolds, which had 0. The properties of the final non-woven sheet are shown in Table 3.

These data show that a reduction in the diameter of the para-aramid floc can lead to some improvement in the mechanical properties of a hydroentangled sheet made from a wet-laid non-woven of essentially binder-free aramid floc.

Two wet-laid non-woven sheets of different basis weights were formed and hydroentangled as in Example In addition, the sheets were hot calendered at C.

The properties of the calendered sheets are shown in Table 4. When compared with the data in Table 3, these data show that calendering dramatically increases the strength of an aramid non-woven sheet of this invention. Also, the data indicate that it is possible to produce an aramid non-woven sheet having about the same strength in both the machine and the cross directions of the sheet.

A wet-laid non-woven sheet was formed and hydroentangled as in Example 12 and was calendered as in Example The sheet was impregnated on a vertical prepregging tower using an epoxy resin system with Tg about C. The epoxy resin system used was L sold by Fortin Industries, Inc.

A 2 ply copper clad laminate was produced using a vacuum press. The final laminate contained What is claimed is: 1. A wet-laid non-woven sheet comprising essentially binder-free aramid floc, wherein the aramid floc includes at least 25 percent by weight of para-aramid floc based on the total weight of aramid floc only. The wet-laid non-woven sheet of claim 1 , wherein the aramid floc includes at least 50 percent by weight of para-aramid floc based on the total weight of aramid floc only.

The wet-laid non-woven sheet of claim 1 , wherein the aramid floc includes at least 75 percent by weight of para-aramid floc based on the total weight of aramid floc only.

The wet-laid non-woven sheet of claim 1 , wherein the aramid floc includes percent by weight of para-aramid floc based on the total weight of aramid floc only. The wet-laid non-woven sheet of claim 1 , wherein the aramid floc has an average length of from 3 to 13 millimeters. The wet-laid non-woven sheet of claim 1 , wherein the floc has been hydroentangled. The wet-laid non-woven sheet of claim 1 , which has been hot calendered. The wet-laid non-woven sheet of claim 6 , which has been hot calendered.

The wet-laid non-woven sheet of claim 1 , wherein the aramid floc comprises para-aramid floc and meta-aramid floc. A prepreg that includes the wet-laid non-woven sheet of claim 1.

A prepreg that includes the wet-laid non-woven sheet of claim 7. A prepreg that includes the wet-laid non-woven sheet of claim 8. A laminate made from the prepreg of claim A printed wiring board that includes the laminate of claim A process for making a sheet of essentially binder-free aramid floc, wherein the aramid floc includes at least 25 percent by weight of para-aramid floc based on the total weight of aramid floc only, comprising the steps of: a preparing an aqueous dispersion of 0.

The process of claim 19 wherein the aramid floc has an average length of from 3 to 13 millimeters. The process of claim 19 further comprising the step of hydroentangling the non-woven sheet before or after the non-woven sheet is dried. The process of claim 19 further comprising the step of hot calendering the dried sheet of essentially binder-free aramid floc. The process of claim 21 further comprising the step of hot calendering the dried sheet of essentially binder-free aramid floc.

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At Dusk by Erica Jackman. Share this site with a friend! Free pattern! This limits the possible strength of the material. One possible solution is to increase the fiber size. Another is to use multiple layers, or plies. An additional advantage of using multiple layers is that some layers may be oriented such that the warp and weft axes of different layers are in different directions, thereby acting like the previously discussed bias fibers.

If these layers are a stack of single layers laminated together with the resin, however, then the problem of de-lamination arises. If the layers are sewn together, then many of the woven fibers may be damaged during the sewing process and the overall tensile strength may suffer.

In addition, for both lamination and sewing of multiple plies, a hand lay-up operation usually is necessary to align the layers. Alternatively, the layers may be interwoven as part of the weaving process.

Creating multiple interwoven layers of fabric, particularly with integral bias fibers, has been a difficult problem. One example of where composite materials are used to produce structural components is in the production of struts and braces. Struts and braces typically comprise a central column having lugs on each end of the structure. These lugs can have either male or female clevis configurations and are used to attach the strut or brace to the structure it is reinforcing or bracing.

As previously discussed, in order to achieve increased strength of the composite structure, multiple layers or plies are used for the lug and column portions of the struts and braces.

Many examples of laminated lugs exist, some using hybrid materials i. The viability 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 for use in struts and braces, having laminated lug ends or portions and a monolithic three-dimensional woven central column are desirable.

The advantages of using a three-dimensional construction in the central portion of the preform are that it reduces the labor required to cut and collate all of the plies required for a thick composite, and it provides better damage tolerance than conventional laminated composites. The advantage of the independent layers in the ends is that the laminate can be tailored to have specific properties. Specifically, a portion or the preform in whole can be reinforced in a thickness direction by inserting reinforcement fibers at one or more angles.

Accordingly, a need exists for a woven preform having an integrally woven three-dimensional central portion with reinforced laminated lug ends comprised of independent, woven layers. It is therefore a principal object of the invention to provide a three-dimensional woven preform having an interwoven column portion and a stack of individually woven fabrics at the lug ends for use in a composite structure.

It is a further object of the invention to provide a woven preform for a thick composite structure that has quasi-isotropic or multi-directional reinforcement on one or two ends and nearly unidirectional reinforcement in all other areas. It is another object of the invention to provide a woven perform having thickness reinforcement on either or both the lug ends to increase damage tolerance and to improve the through thickness properties.

Yet 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 instant invention. In this regard, the instant invention is directed to a woven preform that is used to reinforce a composite structure and a method of manufacturing such a preform.

The woven preform comprises a central portion with a plurality of layers woven together. The preform includes a first end portion having a plurality of independently woven layers that are integrally woven with the plurality of interwoven layers in the central portion and which extend along the entire length of the preform.

The preform also includes a second end portion having a plurality of independently woven layers that are integrally woven with the plurality of interwoven layers in the central portion and which extend along the entire length of the preform.

Interspersed between the plurality of independently woven layers in the first and second end portions are bias plies. In addition, a woven preform having a single lug end and a column portion end can be constructed according to any of the disclosed embodiments. Another aspect of the instant invention is directed to a three-dimensional woven preform having through thickness reinforcement added to the independently woven layers and the bias plies in the first and second end portions.

Such thickness reinforcement results in an increase in the compressive strength of the preform by reducing the amount of localized buckling that changes the micromechanics and cause premature failure. In addition, the through thickness reinforcement can improve the damage tolerance of the composites part by localizing the amount of delamination associated with impact damage, as well as increase the through thickness strength and stiffness, and the shear strength.

Yet, another aspect of the instant invention is directed to a three-dimensional reinforced composite structure constructed using a woven preform disclosed herein.

The reinforced composite structure comprises a central portion that has unidirectional reinforcement and first and second end portions that are quasi-isotropically or multi-directionally reinforced. Alternatively, the first and second portions may have thickness reinforcement comprising reinforcement fibers inserted at an angle in a thickness direction of the preform.

The reinforced composite structure may also be constructed to have a column portion at one end and a lug portion at the other end. The various features of novelty which characterize the invention are pointed out in particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying descriptive matter in which preferred embodiments of the invention are illustrated in the accompanying drawings in which corresponding components are identified by the same reference numerals.

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

The instant invention will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the illustrated embodiments set forth herein. Rather, these illustrated embodiments are provided so that this disclosure will be thorough and complete, and will fully convey 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. The instant invention is a preform concept for a composite structure or beam that has quasi-isotropic or multi-directional reinforcement on one or two ends and nearly unidirectional reinforcement in all other areas. This configuration is desirable for structures that have to carry large concentrated loads, such as struts and braces.

The quasi-isotropic or multi-directionally reinforced ends provide good bearing properties and more balanced tension, compression, and shear strengths, making them good choices for the lug ends of the structure.

These lug ends can have either male or female clevis configurations. The unidirectional portion provides high axial stiffness, which is good for preventing column buckling or crippling, making it a good choice for the main column of a strut or brace. Depicted in FIG. The lug ends 4 in FIG. The advantages of using a three-dimensional construction in the central portion of the preform are that it reduces the labor required to cut and collate all of the plies required for a thick composite and it provides better damage tolerance than conventional laminated composites.

The advantage of the independent 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 to be quasi-isotropic or multi-directionally reinforced, but they could be practically any laminate configuration.

The instant preform is comprised of a three-dimensional woven portion consisting of a number of layers and a similar number of independent bias layers. In the central or column portion of the three-dimensional woven piece, all of the layers are interwoven or integrally woven together forming a monolithic block of woven material. The fiber architecture used in this portion can be any conventional pattern for a thick preform, including, but not limited to, ply-to-ply, through thickness, angle interlock, or orthogonal architectures.

All of the layers that comprise the preform, including the central or column portion, are woven with warp fibers or yarns and weft or fill fibers or yarns using a Jacquard loom and captured shuttle; however, any conventional weaving technique may be used 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 and polyethylene.