WO2005096759A2

WO2005096759A2 - Braided composite structures

Info

Publication number: WO2005096759A2
Application number: PCT/US2005/011172
Authority: WO
Inventors: Christopher D. Toto; Stephen D. Koehler; Thomas Brice Langston
Original assignee: Greene, Tweed Of Delaware, Inc.
Priority date: 2004-04-01
Filing date: 2005-04-01
Publication date: 2005-10-20
Also published as: WO2005096759A3

Abstract

A fibrous braid (8) is impregnated with a thermoplastic and/or a thermosetting polymer and is heated in order to forma composite capable of a wide variety of uses. The resulting composite is capable of being machined. The resulting composite can be used to form rings or ring portions which are radiolucent and which can be used in orthopedic braces and bone fixators.

Description

TITLE OF THE INVENTION [0001] Braided Composite Structures

CROSS-REFERENCE TO RELATED APPLICATIONS [0002] This patent application claims the benefit of Provisional United States Patent Application Number 60/558,788, filed April 1, 2004, the entire disclosure of which is incoiporated herein by reference.

BACKGROUND OF THE INVENTION [0003] The repair of traumatized bone or the repair or reshaping of defective bone can be accomplished by the use of an external bone fixator device that often includes a number of curved rings or curved half rings. These rings or half rings are spaced apart and are structurally connected using a plurality of tie rods or other connecting devices, such as wires or cords. These connecting devices may be attached to the ring by insertion in the rings through holes present in each of the rings or half rings and or by threading the connectors through hooks, rivets or loops that are affixed to the rings or half rings. For example, curved rings, half rings, and/or connectors are used in the "Ilizarov" method of external fixation of severely damaged or severely traumatized bone. The Ilizarov method can be used for lengthening various congenital and acquired shortenings and other defects of skeletal segments wherein the rings and tie rods form part of a compression distraction apparatus.

[0004] Often the rings and connectors of many bone fixation and other medical devices, including Ilizarov devices, are made of metal. Metals are amenable to sterilization procedures (by heat or chemical agents) and are non-antigenic. Metals also possess the physical properties necessary for many bone fixator apparatuses, for bone or body stabilization apparatuses (such as halos) or for other medical devices, such as strength and a relatively high flexural modulus, for example, 10,000,000 pounds per square inch (psi) (68,948 MPa) for aluminum. [0005] However, metals, while useful, have some disadvantages in such applications. Metal apparatuses can be heavy and consequently unwieldy, potentially hindering a surgeon's dexterity in device insertion or manipulation during a procedure. A patient fitted with a metal-containing device may experience additional discomfort because of the mass of the device, the cold feeling of metal against the skin, and/or the potential for certain types of metal to discolor or irritate the skin. More significantly when considered from the perspective of patient care, metal is not radio-opaque. Bone fixators or other devices secured to a patient may obstruct the passage of diagnostic X-rays, potentially hindering the physician in diagnosis and treatment of the patient. [0006] Plastics (including thermoplastic and thermoset) are generally radiolucent, can be subjected to most sterilization procedures, and do not provoke immune responses in humans. They are not, however, feasible replacements for the rings and half rings used in bone fixators and other medical devices as most do not possess desired tensile strength and flexural modulus properties comparable to metal.

[0007] Because the rings or ring portions used in most bone fixators and other, similar medical devices require the physical properties similar to those of metal as well as radiolucency, attempts have been made to increase the physical properties of plastic polymers by incorporating various fillers, or by lining the peripheral edges of for example, fixation rings with woven or braided fibers, prior to forming the rings through plastic molding. While these measures serve to reinforce the rings to some degree, they are still not adequate in most cases in terms of being comparable to metal in that the portions of the ring subjected to the most force, i.e., those points at which the connectors are attached, remain unreinforced and physical properties are not uniform across the ring. Additionally, some composites and/or plastics are hydrophilic and are not amenable to repeated steam sterilization, such as by autoclaving, because when exposed to steam they can degrade and generally, their mechanical properties become compromised. Therefore, there remains a need in the art for a method of preparing a ring or portion of a ring wherein the entire structure of the ring is reinforced substantially uniformly, but wherein the materials used are radiolucent and are amenable to steam sterilization.

BRIEF SUMMARY OF THE INVENTION [0008] The invention includes a composite comprising a polymer selected from the group consisting of a thermoplastic and a thermosetting polymer; and a fibrous braid; wherein the fibrous braid is impregnated with the polymer and the composite is capable of being machined. [0009] The invention further includes a composite comprising a fibrous braid comprising at least one commingled yarn, wherein the at least one commingled yarn comprises thermoplastic fibers and carbon fibers, wherein the fibrous braid is heated and consolidated to form the composite and the composite is capable of having at least one aperture machined therethrough. [0010] A method of forming a composite structure is also within the scope of the invention and comprises providing a fibrous braid formed by at least one yarn, providing a thermoplastic, applying heat to the fibrous braid and the thermoplastic to impregnate the fibrous braid and to form the composite structure, and machining the composite structure.

[0011] One embodiment includes an orthopedic ring comprising a composite that comprises a thermoplastic and a fibrous braid, wherein the braid is impregnated with the thermoplastic the composite is capable of being machined, wherein the composite has a configuration of an orthopedic ring having at least one aperture extending longitudinally therethrough. [0012] Also within the invention is a composite comprising a thermoplastic polymer; and a fibrous braid; wherein the fibrous braid is impregnated with the thermoplastic and the composite is capable of being machined. ^' BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0013] The foregoing summary, as well as the following detailed description of the invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there are shown in the drawings embodiments which are presently preferred. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown.

[0014] In the drawings:

[0015] Fig. 1 is a top plan view of an embodiment of a ring portion as described herein;

[0016] Fig. 2 is a cross-sectional view of the ring portion in Fig. 1 taken along the line 2-2;

[0017] Fig. 3 a is a perspective view of the ring portion of Fig. 1; [0018] Fig. 3b is a perspective view of a ring portion described herein;

[0019] Fig. 4 is a photograph of non-limiting examples commingled yarns that include polyetheretherketone fibers and carbon fibers;

[0020] Fig. 5 is a photograph of a top view of a fibrous braid useful for forming composites as described herein; [0021] Fig. 5a is a magnified view of the fibrous braid of Fig. 5;

[0022] Fig. 5b is a perspective view of a fibrous braid;

[0023] Fig. 6 is a braiding diagram as described in the specification and referred herein in the Examples; and

[0024] Fig. 7 is a perspective view of orthopedic rings or ring portions as described herein incorporated into a non-limiting example of an orthopedic brace on a patient.

DETAILED DESCRIPTION OF THE INVENTION [0025] Certain terminology is used in the following description for convenience only and is not limiting. Words such as "right," "left," "upper," and "lower" or similar words may be used to designate directions or other information in the drawings to which reference is made. The terminology includes the words above specifically mentioned, derivatives thereof, and words of similar import.

[0026] The present invention includes many embodiments of composites for medical and other uses. The composites are useful for a variety of applications including, without limitation, aerospace applications; medical devices and tools, such as halos, X-ray cassettes, nail guides, X- ray accessories, bone fixators of all types, bone screws, bone plates, stabilizers, braces, structural components of casts; surgical tools such as drills, scalpels, forceps, tweezers, and retractors. Other potential applications include use of the composites to make parts for use in fluid handling applications, industrial applications, biotechnological applications, oilfield applications, semiconductor applications and shipping containers. For the purposes of convenience, the composite will be described herein with respect to rings or ring portions that can be used in orthopedic braces or bone fixation devices. However, it should be understood that the composite can be used to form a wide variety of shapes. [0027] The composite may be made of a thermoplastic polymer or a thermosetting polymer, but is preferably formed from thermoplastic polymer. The composite as described in one preferred embodiment includes at least one thermoplastic. Non-limiting examples of suitable thermoplastics include polyethylene, polyethylene chlorinates, polyaryl ether ketones (such as polyetherketone, polyetherketoneketone and polyetheretherketone), polyamides (such as NYLON 6, NYLON 12), acrylonitrile-butadiene-styrene (ABS), cellulosic resins (such as ethyl cellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, and cellulose nitrate), ethylene vinyl alcohol, fluoroplastics (such as polytetrafluoroethylene (PTFE), fluorinated ethylene propylene copolymer (FEP), perfluoro-alkylalkane (PFA), poly(chlorotrifluoroethylene), ethyl chlorotrifluoroethylene (ECTFE), ethyltrifluoroethylene (ETFE), and polyvinylidene fluoride (PVDF), polyvinyl chlorides (PVC), polyvinylidene chlorides, thermoplastic elastomers (such as ethylene propylene diene elastomers (EPDM), ethylene-propylene rubber (EPR) and polyurethane elastomers), liquid crystalline polymer (LCP), thermoplastic polyesters, ionomers, polyacetals, polyacrylates, polyacrylonitirile, polyamideimides, polybutadienes, polybutylenes, polycarbonates, polyketones, polyetheramides, sulfones (such as polysulfone, polyethersulfone and polyphenylsulfone), polyimides, polymethylpentenes, polyphenylene oxides, polyphenylene sulfides, polyphthalamides, polypropylenes, polystyrenes, polyurethanes, and/or co-polymers and/or derivatives or combinations of these or any other known or to be developed thermoplastic polymers. [0028] The preferred thermoplastics include polyaryl ether ketones (such as polyetherketone, polyetherketoneketone and polyetheretherketone), sulfones (such as polysulfone, polyethersulfone and polyphenylsulfone), and polyphenylene sulfides and/or copolymers and/or derivatives and/or combinations of these or any other known or to be developed thermoplastics. The composite may also include combinations or blends of one or more of the above thermoplastics. [0029] By impregnated, it is meant that the thermoplastic is incorporated intimately into the braid by any acceptable process. For example, the thermoplastic may be incorporated into the braid as a thermoplastic fiber within a yarn or commingled yarn and then heated and consolidated. Alternatively, or in addition to such method, the thermoplastic can be incorporated into the fibrous braid by injection molding or distributed within the braid as powder or pellets which can be heated and consolidated and/or compression molded into the fibrous braid. The thermoplastic can also be incorporated by a combination of these techniques. [0030] The composite has a continuous structure that is formed from entwining at least one yarn. Entwining can be accomplished by any means known in the art, such as knitting, weaving, twisting or braiding. Braiding is preferred. A non-limiting example of a portion of a fibrous braid or braid 8 suitable for use in the composite is shown in Figures 5, 5a, and 5b. The thermoplastic may be part of the braid initially as shown in Figure 5 as yarn including thermoplastic fiber(s), or it can be added in powder, pellet, or liquid form, or both. A braid can be made from at least one yarn. No particular method of braiding is required. Braiding may be accomplished by any technique known in the art or to be developed and may be carried out by use of a machine or by hand. Suitable braiding machines include those disclosed in, for example, but not limited to U.S. Patents No. 4,719,837 and No. 5,320,696, the relevant contents of each of which are incorporated herein by reference.

[0031] The braid may be of any type known in the art, for example, but not limited to, a flat braid, a square braid, a diagonal braid, a sock braid, a cable braid, a tubular braid, a guilloche braid, a corded braid, and a ply-split braid. One embodiment includes a braid that is constructed around another braid so that the complete braid is actually formed of one or more layers of braids. Another possibility includes using a combination of braids such as using two or more flat braids. The transverse cross-section of the braid can be of any shape such as substantially rectangular, substantially polygonal, substantially triangular, substantially octagonal, substantially circular, substantially semicircular, substantially ovoid, and substantially square. The longitudinal direction of the braid is defined herein as taken along the length of the braid and the transverse cross-section is defined as being perpendicular to the longitudinal direction. It is preferred that the transverse cross-sections of the braid are substantially square. Substantially square is broadly defined herein, as are all of the shapes, and includes transverse cross-sections with rounded or defined edges or corners and edges that may be convex and/or concave. [0032] Braids can be prepared with any number, types, or combination of yarns. Non- limiting examples of braid forming machinery include the type that follows a braid track diagram and a horn gear arrangement. One example of how to make a braid (particularly flat, square and rectangular braids) is described in an article entitled "Structure and Machine Braiding Procedure of Coupled Braids with Various Cross Sections," M. Tada et al., Composites Part A: Applied Science and Manufacturing (2001), pp 1485-1489, the relevant contents of which are incorporated herein by reference. ^" [0033] A non-limiting example of a braid track diagram is shown in Figure 6. Braid track diagrams can be in many different shapes and forms. The braid track diagram of Figure 6 includes two substantially rectangular shapes of one size (long and thin) and two substantially rectangular shapes of another size (about three times thicker and about 30% shorter than the longer, thinner rectangles). The long and thin rectangles 10, 12 are positioned in a perpendicular fashion with respect to each other so as to form an "X." The long and thin rectangles are also known as the outside tracks 10, 12. The thicker rectangles 14, 16 are positioned in a perpendicular fashion with respect to each other so as to form an X-like shape. The thicker rectangles are also known as the inside tracks 14, 16. The two "X's" are then placed on top of each other and their edges are parallel to one another so as to form a grid, which is the braid track diagram. The braid track diagram in Figure 6 is comprised of 4 tracks and 25 grid units. The grid units are labeled with alphanumeric designations (e.g. Al, B4, E7, and so on). U.S. Patent No. 4,719,837, incorporated herein in relevant part by reference, provides further non- limiting examples of other types of track diagrams. The shape of the track diagram is a major factor in the shape of the resulting braid. The shape used will depend on the application or the requirements of the end use.

[0034] Any number of carriers (not shown) generally follow along one or more of the lines or tracks illustrated in the braid track diagram. A carrier contains one or more spools. The spools supply the yam(s) that feed into the braid and a spool may contain one or more yams. Therefore, each carrier can supply one or more yams (also known as ends) at a time. Also, one or more axial yams, which remain stationary, may also be fed from any one or more of the grid units. If axial yam is fed through the grid units, one or more yams can be supplied up through the grid unit from additional spools. The yams fed from the carriers and from the grid units need not be all the same kind of yam. Different yams can be used when braiding, including at least two or more commingled yams 18a, 18b, 18c, non-limiting examples of which are included in Figure 4.

[0035] From the carriers along the braid track diagram and from the axial positions, the yams are fed through to a die (not shown), which primarily holds the braid in place. The "tightness" of the braid can be altered by manipulating gear ratios. The gear ratio affects the angle of the ya s within the braid itself. Also, the gear ratio determines how the yam fibers will wear against each other. The gear ratio varies with the type of yam that is used, the machine employed, and the end application of the braid.

[0036] Positioning of the axial yams depends a great deal on the configuration of the desired end product. For example, if the desired end product is to have two ring portions that have mating ends that are capable of coupling in such a way so as to create a full ring and so that the top faces of the respective ring portions are flush with each other and the respective bottom faces of the ring portions are flush with each other, thereby creating a smooth surface on each face of the resulting ring in the longitudinal direction. A non-limiting example includes the end of a first ring portion that can be machined so as to create a void in order to accept a protrusion or a tab from the end of a second ring portion. Another non-limiting example includes a configuration where the ends of each ring portion are machined so as to create a combination of a stepped void and a tabular protrusion on each end so that the ends of the two ring portions can mate by having the tabular protrusion of one ring portion occupy the stepped void of the mating ring. Axial yams or extra axial yams may be placed in the area of the braid that will correspond to the protrusion of the end of the ring portion so as to provide added strength to the protrusion. [0037] The braid can be of any desired dimension. It will depend on the end application and 1 the size required to determine the braid dimensions to use. Each of the dimensions with respect to width and/or height may, as a non-limiting example, be up to and including about 1 inch (2.54 cm). As another non-limiting example, in the preparation of rings or ring portions, it is preferred that the width or height be independently selected of about 0.5 inches to about 1.75 inches (about 1.27 cm to about 4.44 cm), about 0.7 to about 1.13 inches (about 1.78 cm to about 2.87 cm) and about 0.8 inches to about 1.0 inches (about 2.03 cm to about 2.54 cm). [0038] At least one yam is used to prepare the fibrous braid, although the number of yams will vary depending on the size, thickness, and/or use of the ring or ring portion, as well as the diameter and/or material of the yams selected. In one embodiment of the present invention the braid is formed from 100 to 300 yams, 500 to 1,500 yams, 1,000 to 2,000 yams, 2,000 to 3,000 yams, 3,000 to 5,000 yams, 5,000 to 6,500 yams and greater than 6,000 yams. [0039] The yam(s) may be constructed of any type or types of fibers including staple fibers, continuous fibers, and/or thermoplastic fibers. Staple fibers and continuous fibers may be made from carbon, graphite, glass (including fiberglass), and/or ceramic. Thermoplastic fibers can be formed from any of the thermoplastics referenced above. Yams that include fibers of two or more materials are considered to be commingled yams, for example thermoplastic fibers and carbon fibers. Commingled ya s are preferred.

[0040] Figure 4 is a photograph of a non-limiting example of commingled yams 18a, 18b, 18c. Figure 5 and 5 a are photographs of a section of braid that includes commingled yams. It is preferred that the yams are commingled yams that include at least one carbon fiber and at least one thermoplastic fiber. As a non-limiting example, the commingled yams may include carbon fibers and polyphenylene sulfide fibers. Another non-limiting example of a commingled yam is carbon fibers and polyetheretherketone fibers. Other preferred combinations include carbon fibers with any of the preferred thermoplastics listed above and/or their copolymers and/or their derivatives or any other known or to be developed thermoplastics. ^" [004Ϊ] ^""A^™ noh-Ti^'ihiting ^"example of carbon fiber presence in a commingled yam may range from about 20 wt % to about 77 wt % carbon fibers. Preferably the range of carbon fiber presence is from about 40 wt % to about 73 wt %. More preferably the range of carbon fiber presence with a commingled yam is from about 50 wt % to about 70 wt %. [0042] The selected yams may be of any diameter. Moreover, the braid need not be composed of yams that are all of an identical diameter. A person of skill will recognize based on this disclosure that the diameter of the yam selected will vary depending on several factors including, the size, thickness, and/or use of the ring or ring portion, as well as the material of the yams. It is preferred that the yams have a diameter of about 0.1 to about 20 microns, with about 1 to about 15 microns being more preferred and about 5 to about 10 microns being most preferred. However, yams with diameters of about 0.1 to about 100 microns may be used. [0043] Yams can be used in the braid with a linear weight of about 500 to about 3,600 metric count (meters/kg). Preferably the linear weight ranges from about 750 to about 2,200 metric count. More preferably the linear weight ranges from about 1,400 to about 2,100 metric count. All of the yams used need not be of the same weight and yams of different weights may be used in the same braid. [0044] The composite can also include various additives depending on the intended use. Non-limiting examples of additives include colorants, flame retardants, stabilizers, plasticizers, conductive materials, fillers, ultraviolet absorbers, and other reinforcing fibers or powders. [0045] Exemplary fillers or additives may include but are not limited to glass spheres and/or fibers, carbon spheres and/or fibers, carbon black, silicates, fiberglass, calcium sulfate, asbestos, boron fibers, ceramic fibers, polyamide fibers (such as those sold under the trademark KEVLAR^®, available from E.I. du Pont de Nemours & Co., Wilmington, Delaware, U.S.A.), aluminum hydroxide, barium sulfate, calcium carbonate, magnesium carbonate, silica, alumina, aluminum nitride, borax (sodium borate), activated carbon, pearlite, zinc terephthalate, Buckyballs, graphite, talc, mica, synthetic hectorite, silicon carbide platelets, wollastonite, calcium terephthalate, ceramic compounds, silicon carbide whiskers, or fullerene tubes, depending on the specific properties desired in the end product. One may also include plasticizers, flame retardants, and colorants in the thermoplastic composition from which the yams are prepared. Other fillers or combinations of fillers may be used as is known or to be developed in the art in order to enhance or modify the properties of the resultant thermoplastic composition, including mechanical properties, thermal properties, and/or electrical properties, or to improve the processability of the selected resin(s), for example, by altering the rheological properties of the material. [0046] The ring or ring portion may also include one or more coating layer(s) of thermosetting or thermoplastic polymer. Non-limiting examples of thermosetting polymers useful as a base polymer and/or a secondary polymer or as additives in the composites of the invention may include epoxy resins, phenolic resins, urea-formaldehyde resins, melamine- formaldehyde resins, polybenzoxazole resins, acetylene terminated polyimide resins, silicones, triazines, alkyds, vinyl ester resins, vinyl esters, and xylene resins and/or copolymers and/or derivatives of these or any other known or to be developed thermosetting resins.

[0047] A composite structure as described herein can be formed by any method using any apparatus that has the ability to mold the braid into a structure of any desired shape, depending on the intended end use known in the art or to be developed. In one embodiment, the braid and thermoplastic is heated and consolidated to form a composite structure. In preferred embodiment, the braid and thermoplastic are compression molded under application of heat to form the braid into a ring or a ring portion. The braid may be placed in the cavity of a compression mold configured in the form of a ring or ring portion. If there is excess braid, it is preferably trimmed such that the length of the braid is approximately the same as the perimeter of the mold cavity. The braid and thermoplastics are then compression molded at a temperature and dwell time suitable for the selected thermoplastic. If the thermoplastic is present in the braid in the form of a fiber then only the braid will be compression molded, if no further thermoplastics are to be added. For example, the thermoplastic is preferably present in the form of one or more yams which are commingled within the braid, such as polyphenylene sulfide fiber commingled with carbon fibers, the molding should be carried out at a pressure of about 230 psi (1.58 MPa) and at a temperature of about 640°F (337.8°C). If the braid includes commingled yams of NYLON- 12 and carbon fibers, then the molding should be carried out at a pressure of about 160 psi (1.10 MPa) and a temperature of about 450°F (232.2°C). [0048] The resulting composite structure is substantially uniform in appearance in the longitudinal and transverse directions due to the even distribution of the polymer, preferably of the thermoplastic. If there are any fiber fragments or continuous fibers used, it is preferred that they are evenly dispersed throughout the composite structure. Likewise, if there are any fillers, it is preferred that they are evenly distributed. The composite is substantially uniform and if a cross-section were taken in any direction along the device it would show a substantially thorough and uniform dispersement of fibers, thermoplastic and fillers (if any). [0049] An advantage of using thermoplastics is, in general, they are amenable to being reformed or remolded if a piece would happen to break off or if the desired shape needed to be adjusted. Being reformed is defined as reheating and/or reconsolidating the composite structure in order to (re)create a refurbished or new composite structure. The temperatures and pressures used are the molding temperatures that are suitable to the particular thermoplastic that is in the composite. More thermoplastic and or fibers may be added to fill in any voids. This reduces waste and can be a cost savings measure. ^* [0050] ^"Using the preferred thermoplastics listed above allows the composite to be sterilized using steam and/or heat and/or autoclaving without compromising the mechanical performance or affecting the dimensional characteristics (will not deform) of the composite structure. The preferred thermoplastics are amenable to steam sterilization and/or autoclaving because they are generally hydrophobic and will not deform (such as swell, warp, etc.) or degrade from being exposed to steam, thereby maintaining their mechanical performance. Having a composite that is amenable to steam sterilization or autoclaving is especially important in medical device applications. This also allows the composite structure to be reused. Autoclaving typically takes place at temperatures that range from about 265°F (129.4°C) to about 280°F (137.8°C) and at pressures from about 17 psi (1.16 atm) to about 29.4 psi (2 atm). [0051] The resulting composite can be molded into any desired shape. One embodiment of the present invention, for purpose of illustration, herein includes a braid that is molded into a ring or ring portion composite structure. By "ring," as used herein, it is meant any structure having a configuration such that the structure has substantially continuous inner and outer perimeters and the inner perimeter defined as an annular space. While preferred, the ring need not have a generally circular outer and inner perimeter configuration, but may resemble any closed geometric shape - it may be, for example, square, polygonal, ovoid, elliptical or triangular in shape, or any approximation of these geometries. The inner and outer perimeters of the ring when preferably of similar geometries could have differing configurations. For example, a generally square outer perimeter and a generally circular inner perimeter. By a "ring portion," as used herein, it is meant any section of a ring that preferably is capable of being assembled with other ring portions to form a ring. Ring portions can include, for example, but are not limited to 1/2, 1/4, 1/3, 1/16, and 1/64 of a ring. A non-limiting example of a ring portion is shown in Figures 1 and 3 a. The ring portions are preferably designed so that they are able to releasably interlock or become releasably attached using connecting devices or by other techniques so as to form an entire ring structure a part of a ring structure or an orthopedic brace forming using such rings or ring portions. The ring portions are preferably configured using a mold, but may also be instead of or in addition to molding, machined from a larger ring portion or larger composite structure. [0052] An embodiment of the composite structure as a ring 20 is shown in Figure 3b and as a ring portion 22 is shown in Figures 1 and 3 a. The transverse cross-section of the composite structure shown is a circular ring 20. The transverse cross-section of the composite structure can also be a circular ring portion 22. As used herein with respect to the ring and ring portion, the transverse direction is defined along the T'-T' axis and T-T axis as shown respectively in Figures 3a and 3b. The longitudinal direction is defined herein with respect to regarding the ring 20 and ring portion 22 as being in the direction of the A'- A' axis and A-A axis, respectively. [0053] Preferably, the composite structure is capable of being machined, such that the edges can be beveled or smoothed, end mitered, or one or more apertures can be inserted in the ring. For example, the ring or ring portions may have aperture(s) or other openings or features for use in the connecting the rings or ring portions. The apertures may be formed through the molding process or preferably when using a braid composite, they are machined. For example, in the case of an Ilizarov ring, apertures may be machined in the ring or ring portion in order for ties and connectors to be inserted. The apertures need not be circular in shape. For example, the aperture can be in the shape of an arc or elongated hole and/or be threaded. In one embodiment, as shown in Figures 1, 2, 3a, and 3b, at least one of the substantially circular apertures 24 are formed in the composite structure so as to extend longitudinally therethrough. If desired, at least one aperture may be threaded to as to accept a screw or a bolt like member or other similar device that has male threads. Alternatively, hooks, loops or other fixation devices may be secured to the ring or ring portion. One skilled in the art will be able to determine, depending on use and structural integrity, a maximum desired size or diameter for any aperture. [0054] Alternative means of formation may also be used. The ring can be formed by attaching the two ends of a ring portion with the two ends of another ring portion with an epoxy, adhesive, or other fixative, and heat curing the preformed structure.

[0055] If the composite is made of a thermosetting polymer and a fibrous braid, the basic idea as the thermoplastic, described above, is followed, with a few adjustments, which are as follows. If a thermosetting polymer is used to create the composite, the fibrous braid will only consist of fibers that include carbon, glass (including fiber), graphite, and ceramic. Commingled yams generally are not used with the thermosetting polymer, however it may be and can be used in some applications. Any of the thermosetting polymers described above may be used. As a non-limiting example, the fibrous braid is impregnated with the thermosetting polymer by placing the braid into a suitable mold and then pouring the thermosetting polymer in liquid form into the mold, thereby wetting the braid and then applying heat and/or pressure to the fibrous braid and the thermosetting polymer to form the thermosetting polymer composite. [0056] The present invention also includes a method of forming a composite structure, as defined above, which includes providing a fibrous braid that is formed from at least one yam and a thermoplastic, applying heat to the fibrous braid and thermoplastic to form the composite structure, and machining the composite structure.

[0057] The fibrous braid used in the method of forming a composite structure is preferably the braid that is described hereinabove. The braid may be constructed on site, shipped from another site, or it may come from a supplier. [0058] Heat is applied to the braid and thermoplastic in order to form the composite structure. Preferably, the composite structure is formed in a compression molding apparatus. As described above, the temperature and pressure used will depend on the materials selected for inclusion in the composite structure.

[0059] After the composite structure is formed, it can then be machined if necessary in the manner described above. In one embodiment, the resulting transverse cross section of the composite structure is a ring or ring portion. If (an) aperture(s) is (are) to be placed within the ring or ring portion, the aperture(s) may be formed when being molded or may be machined into the ring or ring portion. It is preferred that the aperture(s) be machined into the ring or ring portion. [0060] Another aspect of the invention includes an orthopedic ring or ring portion 30 that is suitable for use in an orthopedic brace 32, as shown in Figure 7. The ring or ring portion is preferably made from a composite that includes a fibrous braid preferably formed from commingled yams that include thermoplastic fibers and carbon fibers and then formed by heat molding into a composite structure having a desired ring or ring portion configuration. The ring or ring portion is preferably capable of being machined and preferably has at least one aperture 24 that extends longitudinally therethrough.

[0061] The fibrous braid may be made to have the same construction and use the same material as those described above. Preferably, the fibrous braid includes commingled yams with one or more thermoplastic fibers and one or more carbon fibers. The thermoplastic can be a combination, copolymer or blend of any of the thermoplastics listed above or their derivatives. The preferred thermoplastics include polyaryl ether ketones, polyether sulfones, polysulfones, polyphenylene sulfides, and combinations and derivatives and copolymers thereof. Creating the orthopedic ring or ring portion using these preferred thermoplastics allows the orthopedic ring or ring portion to be amenable to sterilization, such as by autoclaving, as discussed above. [0062] The fibrous braid is transformed into the composite by a suitable heat and pressure, which is determined by the type of thermoplastic that is used. Preferably compression molding is used. When finished the composite is in the form of a basic ring or ring shape. The basic ring or ring portion shape may then be further machined into the orthopedic ring, such as by adding aperture(s). [0063] The orthopedic ring or ring portion preferably has at least one aperture. The aperture can be formed by machining in the orthopedic ring. Preferably, the at least one aperture extends in the longitudinal direction. The aperture can be of any shape, as discussed above. Preferably, the aperture is substantially circular. The aperture can be of any diameter as discussed in detail above. One skilled in the art would be able to determine the maximum diameter of the aperture so that the integrity of the orthopedic ring is not compromised. [0064] A preferred embodiment includes an aperture that is threaded by machining. The aperture is machined in such a way as to allow the aperture to accept bolt-like and screw-like devices or fittings or any device that includes a mating thread.

[0065] The orthopedic ring or orthopedic ring portions can be used with other orthopedic rings or orthopedic ring portions in any suitable orthopedic device. Also, the orthopedic ring portions can be attached to other orthopedic ring portions to create a Ml orthopedic ring. One embodiment includes, as shown in Figure 7, the orthopedic rings being constructed of at least two ring portions where the ends of the two ring portions are fastened together at a point 34. One way of having the ring portions fasten together includes having the ends of the two ring portions overlap so as to form a circular ring and so that the apertures of each ring portion match up in such a way that a bolt or bolt like device or tie rod can be inserted into the lined-up apertures of the ring portions and then secured with a nut or cap like device. Washers or washerlike devices may be used to help fasten and secure the bolt like device to the ring portions. Having ring portions come together to make a ring around a limb allows the brace to be constructed without requiring movement of the limb. Additional supports or tie rods can be attached to the other parts of the ring or ring portions to create the orthopedic structure as shown in Figure 7.

[0066] There are a wide variety of such orthopedic brace designs and any such design capable of using rings or ring portions as described herein is within the scope of the invention. [0067] The following non-limiting examples are directed to the manufacture of exemplary braids for use in the invention. Composites may include braids that can be made from the braiding patterns that are disclosed below.

Example 1 [0068] Commingled yams of carbon fibers and polyetheretherketone (PEEK) fibers were obtained and loaded onto a conventional 3-D braider machine (a Rockwell 36 Carrier Lattice Braider was used in this example) having 36 carriers, a gear ratio of 26 to 70, and a die size of 1 inch (2.54 cm). The braider was oriented so that the inside tracks 14, 16 had 10 carriers each on track. Each carrier contained one spool and there were 10 yams per spool. The inside tracks 10, 12 had 8 carriers on each track. Each carrier on the inside track contained one spool and and there were 10 yams per spool. The outside comers (Al, A7, Gl, G7) contained 0 spools and 0 yams and the inside comers (C3, C5, E3, E5) varied. The braider was operated in accordance with standard techniques. The resultant braid had a cross-section that varied along the length of the braid with height and width measurements ranging from about 0.75 inches to about 1.0 inches (about 1.90 cm to about 2.54 cm). Example 2

[0069] Commingled yams of carbon fibers and NYLON- 12 were obtained and loaded onto a conventional 3-D braider machine as described in Example 1 but having 20 carriers, a gear ratio of 44 to 52, and a die size of 3/8 inches (0.9525 cm). The braider had the same orientation as that in Example 1. The outside comers (Al, A7, Gl, G7) contained 4 spools and 2 ya s per spool and the inside comers (C3, C5, E3, E5) 4 spools, 10 yams per spool. The braider was operated in accordance with standard techniques. The resultant braid had a cross section with an height measurement Of about 0.385 inches to about 0.415 inches (about 0.98 cm to about 1.05 cm) and a width measurement of about 0.355 inches to about 0.385 inches (about 0.90 cm to about 0.98 cm).

Example 3

[0070] Four braid configurations were created below with a conventional 3-D braid machine as described in Example 1, having 36 carriers - but the carriers are allocated so that there are 9 carriers on each track. A gear ratio of 68 to 28 was used, and a die size of 1.0 inch (2.54 cm) was used. Also, each carrier has one spool with 10 yams. The yams used were commingled polyphenylene sulfide (PPS) fibers and carbon fibers. The linear weight of the yam was 1700 metric count (meters/kg). Four example braids were constructed using the following axial positions: [0071] Braid A - 4 yams in each axial position labeled Al, A7, Gl, and G7.

[0072] Braid B - 4 yams in each axial position labeled B4, D2, D6, and F4.

[0073] Braid C - 4 yams in each axial position labeled Al, A7, Gl, G7, B4, D2, D6, and F4.

[0074] Braid D - 4 yams in positions Al, A7, Gl, and G7, and 7 yams in positions B4, D2,

D6, and F4. [0075] The transverse cross-section of the braids varied in width and height from about 0.875 inches (2.22 cm) to about 1.125 inches (2.86 cm) along the length of the braid.

Example 4

[0076] Four braid configurations were created below with a conventional 3-D braid machine as described in Example 1, having 36 carriers - but the carriers are allocated so that there are 9 carriers on each track. A gear ratio of 26 to 70 was used, and a die size of 1 inch ( 2.54 cm) was used. Also, each carrier has one spool with 10 yams or yams. The yams used were commingled polyetheretherketone (PEEK) fibers and carbon fibers. The linear weight of the yam was 1500 metric count (meters/kg). Four example braids were constructed using the following axial positions: [0077] Braid E - 4 yams in each of the following axial positions: B4, D2, D6, and F4. [0078] Braid F - 8 yams in each of the following axial positions: B4, D2, D6, and F4. [0079] Braid G - 4 yams or yams in the following axial positions: B2, B4, B6, D2, D6, F2, F4 and F6. There were 6 yams in the D4 axial position. [0080] Braid H - 8 yams or yams in the following axial positions: B2, B4, B6, D2, D6, F2, F4 and F6. There were 10 yams in the D4 axial position.

[0081] The transverse cross-section of the braids varied in width and height from about 1.0 inch (2.54 cm) to about 1.25 inches (3.175 cm) along the length of the braid. [0082] Each of the braids result in substantially square transverse cross-sectional shapes. Although, there is a slight variation in that the transverse cross-section of the braid may have right and left sides that are concave on the sides and convex on the upper and lower sides. The shape of the cross-section of the braid is dependent upon the amount of and positioning of the axial yams. Braids with axial yams result in composites with a greater strength than those braids that are without axial yams. [0083] The composites as disclosed herein show advantages over the prior metallic rings and devices. Composites constructed from fibrous braids that are impregnated with thermoplastic are light weight and radiolucent, which are excellent properties for use in medical applications such as orthopedic braces and bone fixation devices, yet their properties are such that they have the desired physical properties to be used in such applications. Additionally, thermoplastic composites do not feel as cold as metal upon contact with the skin, which is an additional benefit, especially in the design of orthopedic braces and bone fixation devices. [0084] It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims.

Claims

CLAIMS We claim:

1. A composite comprising a polymer selected from the group consisting of a thermoplastic polymer, a thermosetting polymer, and copolymers, derivatives and combinations thereof; and a fibrous braid; wherein the fibrous braid is impregnated with the polymer and the composite is capable of being machined.

2. The composite according to claim 1, wherein the polymer is a thermoplastic polymer selected from the group consisting of polyaryl ether ketones, polyether sulfones, polysulfones, polyphenylene sulfides and derivatives, copolymers, and combinations thereof.

3. The composite according to claim 1, wherein the composite is amenable to being sterilized by using steam.

4. The composite according to claim 1, wherein the fibrous braid comprises commingled yams.

5. The composite according to claim 1, wherein the thermoplastic polymer is provided to the braid in the form of thermoplastic fibers.

6. The composite according to claim 1, wherein the fibrous braid comprises a fiber selected from the group consisting of carbon, glass, graphite, fiberglass, ceramic and combinations thereof.

7. The composite according to claim 1, further comprising one or more additives selected from the group consisting of colorants, flame retardants, stabilizers, plasticizers, conductive materials, fillers, ultraviolet absorbers, and reinforcing fibers.

8. The composite according to claim 1, wherein the fibrous braid comprises a plurality of braided layers.

9. The composite according to claim 1, wherein the polymer is a thermoplastic polymer and the composite is formed by heating and consolidating thereby shaping the fibrous braid and the thermoplastic polymer to form a composite structure.

10. The composite according to claim 9, wherein the composite is substantially uniform throughout a transverse and a longitudinal cross-section of the composite structure.

11. The composite according to claim 10, wherein the transverse cross-section of the composite structure has a configuration which is a substantially circular ring or a substantially circular ring portion.

12. The composite according to claim 11, wherein the composite structure contains at least one machined aperture extending longitudinally therethrough.

13. A method of forming a composite structure comprising, providing a fibrous braid formed by at least one yam; providing a thermoplastic; applying heat to the fibrous braid and the thermoplastic to impregnate the fibrous braid and to form the composite structure; and machining the composite structure.

14. A method according to claim 13, wherein the thermoplastic is selected from the group consisting of polyaryl ether ketones, polyether sulfones, polysulfones, polyphenylene sulfides, and derivatives, copolymers and combinations thereof.

15. A method according to claim 13, wherein there is at least one yam in the fibrous braid which is a commingled yam and wherein the at least one yam comprises thermoplastic fibers and carbon fibers.

16. The method according to claim 13, wherein heat is applied and the composite structure is formed by compression molding.

17. The method according to claim 13, further comprising coating the ring with a material selected from the group consisting of thermoplastic polymers, thermosetting polymers, and combinations thereof.

18. The method according to claim 13, further comprising providing the thermoplastic by injection molding.

19. The method according to claim 13, further comprising providing the thermoplastic by interweaving thermoplastic polymeric fibers into the braid.

20. A method according to claim 13, wherein a shape of a transverse cross section of the composite structure is selected from the group consisting of a substantially circular ring and a substantially semi-circular ring portion.

21. The method according to claim 20, further comprising machining one or more apertures into the ring or ring portion.

22. An orthopedic ring formed from a composite, comprising a thermoplastic; and a fibrous braid, wherein the braid is impregnated with the thermoplastic to form the composite, the composite is capable of being machined; and the composite has a configuration of an orthopedic ring having at least one aperture extending longitudinally therethrough.

23. The orthopedic ring according to claim 22, wherein the orthopedic ring comprises a first portion and a second portion, each portion having a transverse cross-sectional configuration which is substantially semicircular.

24. The orthopedic ring according to claim 22, wherein the orthopedic ring is amenable to steam sterilization.

25. The orthopedic ring according to claim 22, wherein the at least one aperture is formed by machining the composite.

26. The orthopedic ring according to claim 25, wherein the at least one aperture is threaded.

27. The orthopedic ring according to claim 26, wherein the thermoplastic is selected from the group consisting of polyaryl ether ketones, polyether sulfones, polysulfones, polyphenylene sulfides, and derivatives, copolymers, and combinations thereof.

28. A composite comprising a fibrous braid comprising at least one commingled yam, wherein the at least one commingled yam comprises thermoplastic fibers and carbon fibers; wherein the fibrous braid is heated and consolidated to form the composite and the composite is capable of having at least one aperture machined therethrough.

29. A composite according to claim 28, wherein the thermoplastic fibers are selected from the group consisting of polyaryl ether ketones, polyether sulfones, polysulfones, polyphenylene sulfides, and derivatives, copolymers and combinations thereof, and wherein the composite can be sterilized by using steam.

30. A composite comprising a thermoplastic polymer; and a fibrous braid; wherein the fibrous braid is impregnated with the thermoplastic and the composite is capable of being machined.