WO2001038622A1

WO2001038622A1 - Three-dimensional fiber preform and composite material comprising same for injury prevention and energy attenuation

Info

Publication number: WO2001038622A1
Application number: PCT/US2000/042142
Authority: WO
Inventors: Jeffrey C. Leung; Farshid Guilak; Anthony V. Seaber
Original assignee: 3Tex, Inc.
Priority date: 1999-11-24
Filing date: 2000-11-13
Publication date: 2001-05-31
Also published as: AU2622701A

Abstract

An impact resistant three-dimensional preform (P), and an impact resistant composite material including the preform, where the preform includes at least three systems of fibers (10, 12 and 14), wherein two of the three fiber systems define an upper layer (U), a lower layer (L), and a medial layer (M), between the upper layer and the lower layer within the three-dimensional structure preform, and wherein one of the at least three fiber systems interconnects the upper layer, the lower layer and the medial layer. The fiber systems within the upper and lower layers can be made primarily from a reinforcing material and the fiber system within the medial layer can be made primarily from a thermoplastic material.

Description

THREE-DIMENSIONAL FIBER PREFORM AND

COMPOSITE MATERIAL COMPRISING SAME

FOR INJURY PREVENTION AND ENERGY ATTENUATION

Technical Field

The present invention relates to a three-dimensional fiber preform, and to a composite material comprising the same. The preform and composite material comprising same are characterized by lightweight and high impact resistance properties and are preferred for use in injury prevention and energy attenuation applications.

Background Art The use of high-performance composite fiber materials is becoming increasingly common in applications such as aerospace and aircraft structural components. As is known to those familiar with the art, fiber reinforced composites consist of a reinforcing fiber such as carbon or KEVLAR^® and a surrounding matrix of epoxy resin, PEEK or the like. Most of the well-known composite materials are formed by laminating several layers of textile fabric, by filament winding or by cross laying of tapes of continuous filament fibers. However, all of the structures tend to suffer from a tendency toward delamination. Thus, efforts have been made to develop three-dimensional braided, woven and knitted preforms as a solution to the delamination problems inherent in laminated composite structures. Representative three- dimensional textile preforms are disclosed in U.S. Patent No. 5,465,760 issued to Mohamed et al. on November 14, 1995 and U.S. Patent No. 5,085,252 issued to Mohamed et al. on February 4, 1992.

Therefore, there remains a continuing need for an improved composite material which does not tend to delaminate and that possesses very high impact resistance. Such a composite material could be used prophylactically to prevent injury, especially to athletes and sports participants and to the elderly and those vulnerable to injury (e.g. those who suffer degenerative tissue and bone structure changes). Such a composite material would also provide a variety of economic benefits, including reducing of medical costs, decreasing number of days of missed work, and prolonging life, among other benefits. Toward these ends, applicants have developed a newthree-dimensional fiber structure preform, and composite material comprising the same, wherein the three-dimensional preform is formed with fiber systems comprising materials that have been selected to impart improved impact resistance and energy attenuation characteristics. Applicants believe that the novel preform and composite material are new in the impact resistant composite product art and meet a long-felt need for such products; for a method for making the products; and for a method of attenuating impact energy to a structure using the products.

Summary of the Invention In accordance with the present invention, applicants provide an impact resistant three-dimensional fiber preform, an impact resistant composite material, and a method for making the same. The three-dimensional fiber structure preform comprises at least three systems of fibers, wherein two of the three fiber systems define an upper layer, a lower layer and a medial layer between the upper layer and the lower layer within the three-dimensional fiber structure preform, wherein one of the at least three fiber systems interconnects the upper layer, the lower layer and the medial layer, and wherein the at least three fiber systems comprise a reinforcing material, a thermoplastic material or combinations thereof. The impact resistant composite material comprises a three-dimensional fiber structure preform formed of at least three systems of fibers, wherein two of the three fiber systems define an upper layer, a lower layer and a medial layer between the upper layer and the lower layer within the three-dimensional fiber structure preform, wherein one of the at least three fiber systems interconnects the upper layer, the lower layer and the medial layer, and wherein the at least three fiber systems comprise a reinforcing material, a thermoplastic material or combinations thereof.

In one embodiment of the impact resistant three-dimensional fiber preform and composite of the present invention, the fiber systems which define the upper layer and the lower layer comprise a reinforcing material and the fiber systems which define the medial layer comprise a thermoplastic material. In another embodiment of the impact resistant three-dimensional fiber preform and composite of the present invention, the fiber systems which define the upper layer, the medial layer and the lower layer each comprise a reinforcing material.

The impact resistant composite can further comprise a resin material that impregnates at least a portion of the three-dimensional fiber structure preform. Optionally, the at least three fiber systems define a plurality of interstices within the fiber structure preform. In accordance with another aspect of the present invention, applicants provide a method of attenuating a risk of injury to a structure, preferably a structure susceptible to receiving impact forces which cause injury. The method comprises providing an impact resistant three-dimensional fiber structure preform formed of at least three systems of fibers, wherein two of the three fiber systems define an upper layer, a lower layer and a medial layer between the upper layer and the lower layer within the three-dimensional structure preform, wherein one of the at least three fiber systems interconnects the upper layer, the lower layer and the medial layer; and covering the structure with the three-dimensional fiber preform to thereby attenuate a risk of injury to the structure.

It is therefore an object of the present invention to provide a three- dimensional structure preform, and a composite material comprising the same, that is lightweight and impact resistant.

It is another object of the present invention to provide a three- dimensional structure preform, and a three-dimensional composite material comprising the same, in order to provide enhanced structural integrity and improved energy attenuation. It is another object of the present invention to provide a three- dimensional structure preform, and a three-dimensional composite material comprising the same, to provide enhanced performance characteristics including enhanced resistance to delamination. It is still another object of the present invention to provide a three- dimensional structure preform, and a three-dimensional composite material comprising the same, that provides enhanced resistance to delamination, enhanced impact resistance, enhanced fatigue life, and enhanced stiffness-to- weight ratio. Some of the objects of the invention having been stated , other objects will become apparent with reference to the Drawings and Examples described hereinbelow.

Brief Description of the Drawings Figures 1 A - 1 C show a top, perspective and side view, respectively, of a three-dimensional orthogonally woven preform which is utilized in one embodiment of the impact resistant composite material product of the present invention.

Detailed Description of the Invention Applicants have developed a novel impact resistant three-dimensional fiber preform and a composite material comprising the same that can be used in injury prevention and energy attenuation applications. The impact resistant three-dimensional fiber preform comprises at least three systems of fibers, wherein two of the three fiber systems define an upper layer, a lower layer and a medial layer between the upper layer and the lower layer within the three- dimensional fiber structure preform, and wherein one of the at least three fiber systems interconnects the upper layer, the lower layer and the medial layer. The at least three fiber systems preferably comprise a reinforcing material, thermoplastic material or combinations thereof. Preferably, the three-dimensional fiber preform comprises a three- dimensional textile preform. In this case the fiber systems are referred to as yarn systems.

An aspect of the uniqueness of applicants' inventive product and process is the selection of particular materials and particular proportions of materials for use in three-dimensional fiber preforms with inherent structural integrity. The unexpected and surprising result is a novel three-dimensional fiber preform, and composite material comprising the same, that has significantly less specific density (e.g., up to 60% decrease), than a conventional composite (e.g. KEVLAR^® fiber/epoxy resin only - no three- dimensional fiber preform) and that has higher impact-resistance (e.g., up to 200% increase), higher fatigue resistance (e.g., up to 300% increase), higher specific tensile strength (e.g., up to 100% increase) and compression strength (e.g., up to 100% increase), higher specific tensile modulus (e.g., up to 100% increase), and higher specific bending stiffness (e.g., up to 100% increase). While the following terms are believed to be well understood by one of ordinary skill in the art, the following definitions are set forth to facilitate explanation of the invention.

The term "composite material", as used herein, is meant to refer to any material comprising two or more components. One of the components of the material can optionally comprise a resin.

The term "moldable" is meant to refer to an ability to be molded to a particular shape. In the case of a "moldable" preform or composite of the present invention, the preferred shape comprises a shape of a structure to be protected. A "moldable" preform or composite of the present invention can be permanently shaped or can be "re-moldable", or shaped again, via additional applications of heat, water or other agent, depending on the choice of fibers, resin or both fibers and resin, comprising the preform or composite, as disclosed herein. The term "thermoplastic", as used herein, is meant to refer to materials, including yarns, fibers, threads, and the like, which are susceptible to becoming or remaining soft and moldable when subjected to heat. Preferred examples of suitable thermoplastic materials for use in accordance with the present invention include nylon, low-melt polyester and plastics. Preferred plastics include polyolefin fibers, polypropylene fibers, polyethylene fibers (such as those sold under the registered trademark SPECTRA^® by Allied-Signal, Inc. of Morhstown, New Jersey, those sold under the registered trademark DYNEEMA^® by DSM High Performance Fibers B.V., Heerlen, Netherlands, or those that sold under the registered trademark CERTRAN^® by Hoechst Celanese Corporation, Somerville, New Jersey), or copolymer combinations of any of the foregoing polymer fibers. Indeed, any suitable thermoplastic material as would be apparent to one of ordinary skill in the art after review of the disclosure presented herein is contemplated in accordance with the present invention.

The terms "moldable thermoplastic fibers" and "re-moldable thermoplastic fibers" are also used herein, and refers to the respective polymers listed above and blends thereof-e.g. polystyrene, impact modified polystyrene, rubber modified polystyrene, modified polypropylenes, and the like. Representative moldable thermoplastic fibers are disclosed in U.S. Patent Nos. 5,034,449; 5,219,628; 5,229,177; and 5,499,441 , the entire contents of each of which herein incorporated by reference. In accordance with the present invention, when such fibers are commingled with reinforcing fibers (described below), the resulting preform can be molded to shape, and subsequently be re-molded again. Aspects of the present invention thus pertain to permanent, moldable and re-moldable three-dimensional fiber preforms and composite materials comprising the same. As used herein, the term "reinforcing" is meant to refer to stiff and tough materials, including yarns, fibers, threads, and the like, which strengthen the composite of the present invention and act to resist impact forces. A preferred example for the reinforcing material is a poly-paraphenylene terephthalamide fiber sold under the registered trademark KEVLAR^® by E. I. du Pont de Nemours and Company, Wilmington, Delaware. Other examples include carbon, silicon, glass, fiberglass, a polyester based liquid crystal fiber sold under the registered trademark VECTRAN^® by Hoechst Celanese Corporation, Somerville, New Jersey, an aramid fiber sold under the registered trademark TWARON^® by Enka B. V., Arnhem, Netherlands, and an aramid fiber sold under the registered trademark TECHNORA^® by Teijin Kabushiki Kaisha, Osaka, Japan. Metal fibers are also examples of reinforcing fibers. Representative metal fibers include steel, boron, aluminum, iron, copper, nickel, titanium, tin, gallium, alloys of the foregoing, or any other suitable metal fiber as would be apparent to one of ordinary skill in the art after review of the disclosure presented herein. Indeed, any suitable reinforcing material as would be apparent to one of ordinary skill in the art after review of the disclosure presented herein is contemplated in accordance with the present invention.

The term "resin" is used its art-recognized sense and refers to any natural or synthetic resin have characteristics suitable for use in accordance with the present invention, such as an epoxy or polyurethane resin. Additionally, the terms "moldable resin" and "re-moldable resin" are meant to refer to resins that can be molded or re-molded to a particular shape via heat, water or other suitable agent. Representative "moldable resins" and "re- moldable resins" include synthetic polyester resins such as the urethane- modified vinyl ester resins sold under the registered trademark ATLAC^® (e.g. ATALC^® 360 AND ATLAC^® 580) by Reichhold Chemicals, Inc., Durham, North Carolina, and include vinyl ester resins such as the bis-phenol epoxy vinyl ester resins sold underthe registered trademark DION VER^® (e.g. DION VER^® 9102) by Reichhold Chemicals, Inc., Durham, North Carolina.

Additional representative "moldable resins" or "re-moldable resins" are disclosed in U.S. Patent No. 5,405,312, incorporated herein by reference, and include materials produced from the olefin family of long chain, synthetic polymers containing carbon, wherein the materials have a high impact resistance yet are relatively flexible and yet easily molded or re-molded at relatively low temperatures. These materials include ethylene/methacrylic acid based copolymers, and can also be classified as ionomer resins which are thermal plastic polymers that are ionically cross linked. Representative ionomer resins are sold under the registered trademark SURLYN^® and NUCREL^® by E. I. du Pont de Nemours and Company, Wilmington, Delaware. By way of additional example, SURLYN^® 9910 has a thermal forming temperature of between approximately 50° to 80°C (124° to 178°F). This allows the use of the hot water found in the common domestic hot water system having a temperature of approximately 60° to 70°C (140° to 160°F). This temperature range is suitable for softening the SURLYN^® 9910 material to make it easily pliable and "moldable".

The term "water curable resin" is meant to refer to a resin which is cured or hardened by exposure to water, such by immersion in water, and then allowed to dry. Representative water curable resins include a polyurethane prepolymer sold under the registered trademark HYPOL^® FHP 4000 by W. R. Grace and Company of New York, New York, as well as poly-isocyanate resin. Representative "water curable resins" also include those which can be permanently cured or which can be "re-molded" via additional exposure to water.

A. First Embodiment In a first embodiment, the composite material of the present invention comprises a textile structure preform that is fabricated from a true three- dimensional (3-D) fiber architecture (i.e. no fiber crimp and no lamination of multiple layers) such that upper and lower layers that are defined within the textile structure preform comprise mostly reinforcing fibers and some thermoplastic fibers, and a medial layer that is defined within the textile structure preform comprises mostly thermoplastic fibers and some reinforcing fibers.

Referring now to Figures 1A-1 C of the drawings, applicants wish to describe a method of making the composite C of the present invention, as well as the first embodiment of the composite C of the present invention. Although Figures 1 A-1 C illustrate an orthogonally woven three-dimensional preform, the invention is not intended to be limited to this structure but to include other three-dimensional textile structure preforms formed of at least three systems of yarns so as to preferably provide interstices within the structure and structural integrity to composite C. These structures can include woven, braided, circular woven and knitted three-dimensional structures formed of at least three different yarn systems.

Thus, well recognized methods for making three-dimensional preforms comprising at least three yarn systems are generally applicable to the process of making the composite C of the present invention. For example, the 3-D fabric can be fabricated on one of the 3-D weaving machines located at 3TEX, Inc., Cary, North Carolina. As noted above, representative methods of making three-dimensional textile preforms are disclosed in U.S. Patent No. 5,465,760 issued to Mohamed et al. on November 14, 1995 and U.S. Patent No. 5,085,252 issued to Mohamed et al. on February 4, 1992, and the contents of each of these U.S. patents are herein incorporated by reference.

Continuing with reference to Figures 1A-1 C, the composite material C comprises preform P and resin material R. Resin material R is shown in phantom lines around the surface of preform P in Figures 1A-1 C to facilitate explanation of the composite C of the present invention. Preform P is impregnated with resin material R, preferably to the extent that resin material R coats all surfaces of preform P including both internal interstices and external surfaces. Continuing with reference to Figures 1A-1C, three-dimensional textile preform P is formed of at least three systems 10, 12 and 14 of interlaced yarns. As best seen in Figure 1 B, yarn systems 10 run along the x-axis of textile preform P and are repeated in a series of parallel spaced-apart horizontal planes within textile preform P. Yarn systems 12 run along the y-axis of textile preform P and are also repeated in a series of horizontal spaced-apart planes within textile preform P where the horizontal planes are parallel with each other and are parallel with the horizontal planes in which yarn systems 10 lie. However, yarn systems 10 and 12 are laid into textile preform P so that they extend perpendicularly with respect to each other. Yarn systems 14 run along the z-axis of textile preform P and occur in a series of vertical spaced-apart planes which are parallel with each other and which are perpendicular to the horizontal planes in which yarn systems 10 and 12 lie. Yarn systems 14 are laid into textile preform P so that they extend perpendicularly with respect to both yarn systems 10 and 12, and yarns systems 10 and 12 extend perpendicularly to each other (as noted above) as well as perpendicularly to yarn systems 14. As best seen in Figure 1 B, yarn systems 10, 12 and 14 are preferably interlaced so as to provide a plurality of interstices 22 within textile preform P. Indeed, it is preferred that the inventive composite C is not crimped so that interstices 22 remain intact after the intermeshing of yarn systems 10, 12 and 14. As best seen in Figure 1C, yarn systems 10 and 12 define an upper layer U, a lower layer L, and a medial layer M between upper layer U and lower layer L, within the three-dimensional structural preform P. Yarn system 14 interconnects upper layer U, lower layer L and medial layer M. In the first embodiment of the composite C of the present invention, the yarn systems 10 and 12 which define upper layer U and lower layer L comprise primarily a reinforcing material as defined herein, while the yarn systems 10 and 12 which define medial layer M comprise primarily a thermoplastic material as defined herein.

A preferred example for the reinforcing material is a poly-paraphenylene terephthalamide fiber sold under the registered trademark KEVLAR^® by E. I. du Pont de Nemours and Company of Wilmington, Delaware, while polypropylene is a preferred example of the thermoplastic fiber. Thus, in accordance with the present invention, yarn systems 10 and 12 comprising primarily KEVLAR^® fibers and yarn systems 10 and 12 comprising primarily polypropylene are incorporated into a process for making textile structure preform P at appropriate intervals so that the upper layer U and lower layer L in preform P comprise primarily KEVLAR^® fibers and the medial layer M of preform P comprises primarily polypropylene. KEVLAR^® fibers and polyethylene fiber (such as that sold under the registered trademark SPECTRA^® by Allied-Signal, Inc. of Morristown, New Jersey), glass fibers and polypropylene, and glass fibers and polyethylene can also be incorporated in a similar manner into a process for making textile structural preform P in accordance with the present invention.

After formation of textile structure preform P, preform P is impregnated with resin material R, preferably to the extent that resin material R coats all surfaces of preform P including both internal interstices 22 and external surfaces. A coated external surface portion of the composite material C can optionally comprise a smooth sealed surface. As an alternative to the application of resin material R, the composite C of the present invention can be formed by direct heat-molding since the textile structure preform P of the first embodiment is made with thermoplastic fibers.

Properties of the present composites can further be enhanced with controlled cellular matrix formation within resin mateπal R as disclosed in pending U.S. Patent Application Serial No. 09/376,109, herein also incorporated by reference. Briefly, a foamable polymer resin material R is applied to three-dimensional textile structure preform P so as to fill interstices 22 and impregnate three-dimensional textile structure preform P. Then, foamable polymer material R is foamed to produce a cellular foamed polymer matrix material R containing a plurality of voids or cells distributed substantially throughout the material R. Preferably, the cellular matrix within material R comprises bubbles defining a void diameter of between about 0.01 to 10.0 μm, but cell void diameter can be larger. The cellular matrix increases the strength and stiffness properties of the material per unit weight by intentionally creating defined air voids throughout the composite structure.

Representative foaming techniques are also disclosed in U.S. Patent No. 3,796,779 issued to Greenberα; U.S. Patent No.4,473,665 to J.E. Martini- Vredrenskv et al.: U.S. Patent No. 4,761 ,256 to Hardenbrook et al.; and U.S. Patent No. 5,334,356 and U.S. Patent No. 5,158,986 both issued to Baldwin et al. The entire contents of each of these U.S. Patents are herein incorporated by reference. The first embodiment of the composite of the present invention is unique in that it combines two significant mechanical concepts for impact absorption and injury prevention in a single, non-laminated structure: • Distribution of Impact by a Stiff Outer Shell - The composite has greater stiffness and strength per unit weight compared to standard composite materials, and therefore has greater ability to distribute forces. • Dissipation of Energy - The more compliant inner core increases contact time of impacts and provides longer distances over which the impact can decelerate. By increasing contact time, these materials also reduce the peak forces by distributing the impulse of the impact over a greater period of time.

The thickness and composition of the layers of composite C, and thereby of the entire structure, can be altered and customized to fit a variety of energy attentuation and injury prevention applications. Additional yarn systems 10 and 12 can be included within any of upper layer U, lower layer L and medial layer M of textile structure preform P. For example, (+)/(-) bias yarns can be incorporated within textile preform P in accordance with techniques described in U.S. Patent No. 5,465,760. Thus, textile structure preforms having more than three yarn systems are also contemplated for use in the composite of the present invention, including textile structure preforms having four and five yarn systems. The additional yarn systems can comprise reinforcing materials and/orthermoplastic materials depending on a particularly contemplated application for the composite. Incorporation of a reinforcing and/orthermoplastic material is facilitated by reference to the data provided in the Examples presented hereinbelow.

As noted above, yarn systems 10 and 12 which define upper layer U and lower layer L preferably primarily comprise reinforcing materials and thus can also comprise a relatively smaller proportion of thermoplastic material. Correspondingly, yarn systems 10 and 12 which define medial layer M comprise primarily a thermoplastic material and thus can also comprise a relatively smaller proportion of a reinforcing material. This construction can be accomplished by incorporating more filaments of reinforcing material as compared to thermoplastic material into the yarn systems 10 and 12 which comprise upper layer U and lower layer L; and incorporating relatively more thermoplastic filaments as compared to reinforcing filaments into yarn systems 10 and 12 which define medial layer M, as a part of a weaving, knitting, braiding or other process for interlacing yarn systems 10 and 12 to form textile preform P.

Thus, yarn systems 10 and 12 can comprise both a reinforcing material and a thermoplastic material in accordance with the present invention, as can yarn systems 14. In yarn systems 10 and 12 (which comprise upper layer U and lower layer L) and in yarn systems 14, representative proportions of reinforcing material to thermoplastic material can comprise 90/10, 80/20, 70/30 and 60/40. In yarn systems 10 and 12 (which comprise medial layer M) and in yarn systems 14, representative proportions of thermoplastic material to reinforcing material can comprise 90/10, 80/20, 70/30 and 60/40. While representative proportions are provided herein, any suitable proportions may be employed in accordance with the present invention, and preferably, proportions are chosen depending on a particular end use for the preform or composite of the present invention.

B. Second Embodiment A second embodiment of the present invention pertains to a conformable composite material comprising a three-dimensional textile structure preform impregnated with a user curable or moldable resin. The use of a user curable or moldable resin facilitates custom fitting to particular applications, such as a shin guard on a leg or a cast on an elbow.

Referring again to Figures 1A - 1 C, in accordance with the second embodiment of the composite C of the present invention, the yarn systems 10 and 12 which define the upper layer U and lower layer L comprise a reinforcing material, as do yarn systems 10 and 12 which define medial layer M. Thus, each of upper layer U, lower layer L and medial layer M comprise primarily a reinforcing material. However, in accordance with this embodiment of the present invention, resin material R which impregnates three-dimensional textile structure preform P comprises a conformable resin that can be cured or molded by an end-user using heat, water or other agent. Thus, the second embodiment of the composite material of the present invention allows for custom fitting of the composite with respect to a structure that is to be protected from impact forces by composite material C of the present invention.

Representative moldable resins and re-moldable resins include synthetic polyester resins such as the urethane-modified vinyl ester resins sold underthe registered trademark ATLAC^® (e.g. ATLAC^® 360 AND ATLAC^® 580) by Reichhold Chemicals, Inc., Durham, North Carolina and include vinyl ester resins such as the bis-phenol epoxy vinyl ester resins sold underthe registered trademark DION VER^® (e.g. DION VER^® 9102) by Reichhold Chemicals, Inc., Durham, North Carolina.

Additional representative moldable resins or re-moldable resins are disclosed in U.S. Patent No. 5,405,312, incorporated herein by reference, and include materials produced from the olefin family of long chain, synthetic polymers containing carbon, wherein the materials have a high impact resistance yet are relatively flexible and yet easily molded or re-molded at relatively low temperatures. These materials include ethylene/methacrylic acid based copolymers, and can also be classified as ionomer resins which are thermal plastic polymers that are ionically cross linked. Representative ionomer resins are sold under the registered trademark SURLYN^® and NUCREL^® by E. I. du Pont de Nemours and Company, Wilmington, Delaware.

By way of additional example, SURLYN^® 9910 has a thermal forming temperature of between approximately 50° to 80°C (124°to 178°F). This allows the use of the hot water found in the common domestic hot water system having a temperature of approximately 60° to 70°C (140° to 160°F). This temperature range is suitable for softening the SURLYN^® 9910 material to make it easily pliable and moldable.

Any suitable mixture of the moldable resins can also be employed. For example, the ATLAC^® 360, ATLAC^® 580, and DION VER^® 9102 resins referenced above can be used to impregnate preform P as a mixture of about 0 to about 40% ATLAC^® 360, preferably about 10 to about 25% ATLAC^® 360 and more preferably about 7 to about 16% ATLAC^® 360, with the balance in each range comprising ATLAC^® 580 or DION VER^® 9102. Representative water curable resins include a polyurethane prepolymer sold under the registered trademark HYPOL^® FHP 4000 by W. R. Grace and Company of New York, New York, as well as poly-isocyanate resin. Thus, preferred materials for use in the second embodiment of composite material C of the present invention comprise a three-dimensional glass fabric preform impregnated with a water curable HYPOL^® FHP 4000 polyurethane prepolymer. The envelope or casing which houses the fabric-resin combination prior to curing is typically a polyethylene foam, but can comprise any suitable material as would be apparent to one of ordinary skill in the art after review of the present disclosure. Other embodiments include a three-dimensional glass fabric preform impregnated with a polyisocyanate resin, three-dimensional KEVLAR^® fabric preform impregnated with HYPOL^® FHP 4000 polyurethane prepolymer, and a three-dimensional KEVLAR^® fiber preform impregnated with a polyisocyanate resin. Additional yarn systems can be included within any of upper layer U, lower layer L and medial layer M. For example, (+)/(-) bias yarns can be incorporated within textile preform P in accordance with techniques described in U.S. Patent No. 5,465,760. Thus, textile structure preforms having more than three yarn systems are contemplated for use in this embodiment of the composite of the present invention, including textile structure preforms having four and five yarn systems. The additional yarn systems can comprise reinforcing materials and/orthermoplastic materials depending on a particularly contemplated application for the composite. Incorporation of a reinforcing and/orthermoplastic material is facilitated by reference to the data provided in the Examples presented herein below.

As noted above, yarn systems 10 and 12 which define upper layer U, lower layer L and medial layer M preferably primarily comprise reinforcing materials; and thus can also comprise a relatively smaller proportion of thermoplastic material. This construction can be accomplished by incorporating more filaments of reinforcing material as compared to thermoplastic material into the yarn systems 10 and 12 which comprise upper layer U, lower layer L and medial layer M, as a part of a weaving, knitting, braiding or other process for interlacing yarn systems 10 and 12 to form textile preform P.

Thus, yarn systems 10 and 12 can comprise both a reinforcing material and a thermoplastic material in accordance with the present invention, as can yarn systems 14. In the yarn systems 10 and 12 which comprise upper layer U and lower layer L, and in yarn systems 14, representative proportions of reinforcing material to thermoplastic material can comprise 90/10, 80/20, 70/30 and 60/40. While representative proportions are provided herein, any suitable proportions may be employed in accordance with the present invention, and preferably, proportions are chosen depending on a particular end use for the preform or composite of the present invention.

A well-known prior art moldable fiberglass composite that is commercially available consists of multiple layers which are laminated together, and thus suffers delamination and a significant loss of properties following high impact loads. The second embodiment of the composite C of the present invention has greater stiffness per unit weight and greater bending strength since the three-dimensional architecture eliminates any need for lamination. Moreover, the ability to be able to "mold" the structure to a custom shape by the user without compromising the strength and stiffness is a major advantage in the function as well as the comfort of a protective article comprising the composite of the present invention. A better fitting protective article serves to distribute forces over a greater area, effectively decreasing contact stresses. A better fitting guard is also more comfortable and thus more likely to be used. C. Method of Attenuating a Risk of Injury or Damage

A method of attenuating a risk of injury to a structure susceptible to receiving impact energy is also provided in accordance with the present invention. The method comprises:

(a) providing an impact resistant three-dimensional fiber structure preform formed of at least three systems of fibers, wherein two of the three fiber systems define an upper layer, a lower layer and a medial layer between the upper layer and the lower layer within the three-dimensional fiber structure preform, wherein one of the at least three fiber systems interconnects the upper layer, the lower layer and the medial layer; and (b) covering the structure susceptible to receiving impact energy with the three-dimensional fiber preform provided in step (a) to thereby attenuate a risk of injury to the structure. The provided fiber preform can further comprise an impact resistant composite material. In this case, the provided composite material preferably comprises a composite material in accordance with the above-described first and second embodiments of the composite C of the present invention. Thus, the composite preferably further comprises a resin material that impregnates the three-dimensional fiber structure preform.

Preferably, the three-dimensional fiber preform or composite of the present invention is oriented with respect to the structure in or along a path through and/or by which impact energy or impact forces are transmitted to the structure. Representative "paths" include the frontal approach of an impact force in the case of a shinguard covering an athlete's shin.

Any structure susceptible to receiving impact energy or impact forces can be protected in accordance with the present method of reducing impact energy transmitted to such a structure. Indeed, the present invention pertains to injury prevention and energy attentuation of a holistic nature. That is, the methods and products of the present invention prevent injuries through attenuating energy, through decreasing impact, through reducing sprain and strain (particularly recurrent strain), and through absorbing energies from falls, blows and other similar impacts. The prophylactic and protective nature of the impact resistant products of the present invention, especially to the elderly and those vulnerable to injury (e.g. those who suffer degenerative tissue and bone structure changes), is thus apparent. When employed, the methods and products of the present invention thus provide a variety of economic benefits, including reducing of medical costs, decreasing number of days of missed work, and prolonging life, among other benefits. By way of further illustration, parts of the human or animal body, machinery of all kinds, fence works, guardrails and bridges can be protected, and are thus "structures susceptible to receiving impact energy or impact forces". Many athletic, industrial and military protection products can be fabricated using the impact resistant products of the present invention. Representative athletic, military and industrial protection products include shin guards for soccer, baseball or any other activity employing shin guards, leg guards for animals (such as horse leg guards that protect the articulated or like portions of the horse's legs), helmets, chest protectors and safety vests, pads, shoes, boots, gloves, socks, braces, casts, shields, protective body garments including undergarments, back supports, lumbar/back supporting belts, splints, medical bandages, and devices which immobilize protected areas during healing. Thus, a new generation of three-dimensional fiber preforms, and composites comprising the same, for injury prevention and energy attentuation along with a method of using the same are contemplated in accordance with the present invention.

P. Examples The following Examples have been included to illustrate preferred applications and uses of the invention. Certain aspects of the following Examples are described in terms of techniques and procedures found or contemplated by the present inventors to work well in the practice of the invention. These Examples are exemplified through the use of standard laboratory practices of the inventors. In light of the present disclosure and the general level of skill in the art, those of skill will appreciate that the following Examples are intended to be exemplary only and that numerous changes, modifications and alterations can be employed without departing from the spirit and scope of the invention.

Examples - Shin Guard Prototypes Applicants have fabricated and tested three prototype shin guards using the following materials: Example 1 : KEVLAR^® (50/50 resin mix embodiment)

Prepared in accordance with the first embodiment of the present composite.

Preform: Three-dimensional woven fabric, KEVLAR^® 49 fibers (70%) and SPECTRA^® (30%) fibers.

Matrix resin: Epoxy DER331 (50%) and DER732 (50%), cured with hardener DEH26 (14pph).

Example 2: KEVLAR^® (30/70 resin mix embodiment)

Prepared in accordance with the first embodiment of the present composite

Matrix resin: Epoxy DER331 (30%) and DER732 (70%), cured with hardener DEH26 (14pph).

Example 3: Fiberglass (50/50 resin mix embodiment)

Preform: Three-dimensional woven fabric, S-2 glass fiber. Matrix resin: epoxy DER331 (50%) and DER732 (50%), cured with hardener DEH26 (14pph).

The preforms were saturated with the respective resins and wrapped around a cylindrical object to provide a curved geometry. Curing was carried out at 80°C for 2 hours. A 3 mm thick EVA foam pad was attached to the back of each fiber-matrix composite specimen for testing.

Biomechanical testing was performed as described below at a drop height of 40 cm. This level of impact was shown to cause complete fracture of human cadaver bones and of the fiberglass model leg. The peak load upon impact, the peak principal tensile strain on the bone, and the contact time of impact were measured at 10 kHz on a drop track in accordance with the testing methods disclosed above. The results of these studies are presented in comparison to several of the best performing current shin guard models available in the art (Table 1 ).

In most cases, the prototype shin guards/protective covers exhibited force attenuation characteristics and a decrease of tibia strain which surpassed currently available prior art models. For example, Example 3 (fiberglass prototype) showed the greatest decrease of bone strain (as a measure of fracture risk) as compared to any currently available shin guard model. Similarly, Example 1 (prototype comprising KEVLAR^®/SPECTRA^® fibers and a 50-50 epoxy resin) showed better performance in all categories as compared to a commercial moldable fiberglass shin guard. The Examples indicate that the composite material of the present invention incorporated in a shin guard structure provides significantly improved protective capabilities.

Biomechanical Testing of Shin Guard Protective Ability A drop track is used to provide repeatable impacts on tibia specimens. The track comprises of a 20 mm wide rail (available from Thomson Industries, Inc. of Port Washington, New York) mounted to a steel I-beam attached vertically to a wall. The impactor is attached to the track using two linear bearing sliders (available from Thomson Industries, Inc. of Port Washington, New York). The impactor has a mass of 4.2 kg and included an accelerometer (available from PCB Piezoelectronics of Depew, New York), a uni-axial load cell (available from Sensotec of Columbus, Ohio), and a 3.81 cm diameter aluminum tube to strike the target. A 1.27 cm thick butyl rubber guard is attached over the tube to simulate an opposing player's leg or shoe during impact. At the bottom of the drop track, two U-shaped aluminum jigs, used to hold the lower leg models during testing, are mounted to a steel plate supported by a 3.175 mm thick butyl rubber mat. The tibia is supported at its ends by aluminum rods, 1.27 cm in diameter. The rod at the proximal end is held fixed by one jig, while the rod at the distal end lay on top of another jig so that the impactor strikes the specimens along the middle of its length. Forces at the ends of the specimen are measured using two uni-axial load cells (available from Sensotec of Columbus, Ohio). Principal strain magnitude is measured using a three-rosette strain gage (available from Measurement Group, Inc. of Raleigh, North Carolina) attached to the middle of the posterior side of the tibia specimen and centered. An optical sensor (available from MTS of Rancho Palos Verdes, California) is used to measure the velocity of the impactor immediately before impact to ensure the repeatability of the impact energy. A piezoelectric accelerometer (available from Sensotec of Columbus, Ohio) mounted on the impactor is used to measure acceleration (and velocity and displacement, by integration) at 10 kHz during impact.

All shin guard testing is performed on a lower leg model comprised of a rubber covered foam leg (available from Pacific Research Laboratories, Inc. of Vashon Island, Washington) surrounding the synthetic fiberglass bone. The fiberglass bone is designed to represent a left young adult tibia with a length of 36 cm and a 7 cm tibial plateau. The ultimate tensile strength of the model is approximately 172 MPa, with a tensile modulus of 18.6 GPa, flexural modulus of 14.2 GPa, and ultimate flexural strength of 276 MPa. The Poisson's ratio of the material is 0.30, and it has a hardness shore D. Shin guards are attached to the model with a sock of standardized thickness. Testing begins with a minimal 10 cm drop height trial on the unguarded leg. Then, shin guards are tested at the 20 cm drop height. Each guard is subjected to a set of three trials at this drop height. After each set, data for a 10 cm drop height trial on the unguarded leg are collected to observe any changes in mechanical behavior that would indicate permanent damage to the model incurred from testing. After all guards are tested at the 20 cm drop height, the unguarded model leg is tested at the same height. Then, the process begins again at the next highest drop height. Overall, shin guards are tested at 10, 20, 30, 40, and 50 cm drop heights, which will represent a range of physiologic and hyper-physiologic (i.e., fracture-causing) impact energies. Force, strain, and velocity data collected using an amplifier and analog- to-digital computer board (available from National Instruments of Austin, Texas). The software package, Labview (available from National Instruments of Austin, Texas) is used to control data acquisition. Data is filtered using a finite impulse response filter with a cutoff frequency of 600 Hz (SAE Handbook, 1995). The loads measured at the ends of the tibia are summed to obtain the total force on the tibia. The maximum impact force, the maximum principal strain on the posterior side of the tibia, and the velocity immediately before impact is calculated. For each testing situation, the mean of the set of three trials is calculated. For each drop height, a one-factor Multivariate Analysis of Variance (MANOVA), followed by Tukey's method for confidence intervals, is performed to study differences between guards and the unguarded model as a control. Linear correlations between impact parameters and shin guard characteristics of weight, thickness, and length are examined. Thickness of the shin guard material is measured at the site where the guard was impacted during testing.

Table 1 Biomechanical Comparison of Shin Guards Fabricated with three-dimensional Woven Composites

Name Material Length Thickness Weight Peak Load Max Strain Contact Tim

(cm) (mm) (g) (N) (με) (ms)

ADIDAS^® OSI LITE^® Fiberglass 23.0 6.5 115 1174±3 6656±38 14.0±0.3

(Comparison)

UMBRO^® GLADIATOR^® Plastic 23.2 12.7 216 669±5 4393±70 20.6±0.2

(Comparison)

DIADORA^® OSI 6^® Fiberglass 24.2 7.2 72 1026±7 5728±8 17.3±0.3

(Comparison)

Example 1 KEVLAR^® 25.0 5.3 112 947±6 6133±150 16.4±0.3

(Invention) (50/50)

Example 2 KEVLAR^® 25.2 5.2 121 1064±41 6865±85 14.8±0.1

(Invention) (30/70)

Example 3 Fiberglass 25.1 8.0 272 865±28 2784±190 19.2±0.1

(Invention) (50/50)

The present co-inventors have developed a new three-dimensional fiber preform, and a new composite material comprising the same, wherein the three-dimensional preform is formed with fiber systems comprising materials that have been selected to impart improved impact resistance and energy attenuation characteristics to the composite material. Therefore, a new generation of preforms and composites for injury prevention and energy attentuation along with methods of making and using the same have been provided in accordance with the present invention.

It will be understood that various details of the invention can be changed without departing from the scope of the invention. Furthermore, the foregoing description is for the purpose of illustration only, and not for the purpose of limitation-the invention being defined by the claims.

Claims

CLAIMS What is claimed is:

1. A method of attenuating a risk of injury to a structure susceptible to receiving impact energy, the method comprising: (a) providing an impact resistant three-dimensional fiber structure preform formed of at least three systems of fibers, wherein two of the three fiber systems define an upper layer, a lower layer and a medial layer between the upper layer and the lower layer within the three-dimensional fiber structure preform, wherein one of the at least three fiber systems interconnects the upper layer, the lower layer and the medial layer; and (b) covering the structure susceptible to receiving impact energy with the three-dimensional fiber preform provided in step (a) to thereby attenuate a risk of injury to the structure.

2. The method of claim 1 , wherein the at least three fiber systems each comprise a material selected from the group consisting of a reinforcing material, a thermoplastic material and combinations thereof.

3. The method of claim 2, wherein the thermoplastic material is a moldable thermoplastic material or a re-moldable thermoplastic material.

4. The method of claim 2, wherein the fiber systems that define the upper layer and the lower layer comprise a reinforcing material and wherein the fiber systems that define the medial layer comprise a thermoplastic material.

5. The method of claim 2, wherein the fiber systems that define the upper layer, the medial layer and the lower layer each comprise a reinforcing material.

6. The method of claim 1 , wherein the three-dimensional fiber structure preform comprises three orthogonally woven fiber systems, a plurality of braided fiber systems, a plurality of circular woven fiber systems or combinations thereof.

7. The method of claim 1 , wherein the at least three fiber systems define a plurality of interstices within the three-dimensional fiber structure preform.

8. The method of claim 1 , wherein the three-dimensional fiber preform further comprises an impact resistant composite material.

9. The method of claim 8, wherein the composite material further comprises a resin material that impregnates at least a portion of the three- dimensional fiber structure preform.

10. The method of claim 9, wherein the resin material is selected from the group consisting of a moldable resin, a re-moldable resin, a water curable resin, and combinations thereof.

11. The method of claim 9, wherein the resin material comprises a polymer.

12. The method of claim 11 , wherein the polymer is selected from the group consisting of an epoxy resin, a urethane-modified vinyl ester resin, a bis- phenol epoxy vinyl ester, and combinations thereof.

13. The method of claim 12, wherein the polymer resin is selected from the group consisting of a moldable epoxy resin, a re-moldable epoxy resin, a thermosetting epoxy resin, a water curable epoxy resin, a moldable urethane-modified vinyl ester resin, a re-moldable urethane-modified vinyl ester resin, a water curable urethane-modified vinyl ester resin, a moldable bis- phenol epoxy vinyl ester, a re-moldable bis-phenol epoxy vinyl ester, a water curable bis-phenol epoxy vinyl ester, and combinations thereof.

14. The method of claim 9, wherein the resin material further comprises a cellular matrix.

15. An impact resistant three-dimensional fiber structure preform comprising at least three systems of fibers, wherein two of the three fiber systems define an upper layer, a lower layer and a medial layer between the upper layer and the lower layer within the three-dimensional fiber structure preform, and wherein one of the at least three fiber systems interconnects the upper layer, the lower layer and the medial layer, wherein the at least three fiber systems each comprise a material selected from the group consisting of a reinforcing material, a thermoplastic material and combinations thereof.

16. The impact resistant three-dimensional fiber structure preform of claim 15, wherein the fiber systems which define the upper layer and the lower layer comprise a reinforcing material and wherein the fiber systems which define the medial layer comprise a thermoplastic material.

17. The impact resistant three-dimensional fiber structure preform of claim 15, wherein the thermoplastic material is a moldable thermoplastic material or a re-moldable thermoplastic material.

18. The impact resistant three-dimensional fiber structure preform of claim 15, wherein the three-dimensional fiber structure preform comprises three orthogonally woven fiber systems, a plurality of braided fiber systems, a plurality of circular woven fiber systems, or combinations thereof.

19. The impact resistant three-dimensional fiber structure preform of claim 15, wherein the at least three fiber systems define a plurality of interstices within the fiber structure preform.

20. The impact resistant three-dimensional fiber structure preform of claim 19, wherein the three-dimensional fiber structure preform is heat-molded to form a composite material.

21. The impact resistant three-dimensional fiber structure preform of claim 20, further comprising a resin material that impregnates at least a portion of the three-dimensional fiber structure preform to form a composite material.

22. The impact resistant composite material of claim 21 , wherein the resin material is selected from the group consisting of a moldable resin, a re- moldable resin, a water curable resin, and combinations thereof.

23. The impact resistant composite material of claim 21 , wherein the resin material comprises a polymer.

24. The impact resistant composite material of claim 23, wherein the polymer is selected from the group consisting of an epoxy resin, a urethane- modified vinyl ester resin, a bis-phenol epoxy vinyl ester, and combinations thereof.

25. The impact resistant composite material of claim 24, wherein the polymer resin is selected from the group consisting of a moldable epoxy resin, a re-moldable epoxy resin, a thermosetting epoxy resin, a water curable epoxy resin, a moldable urethane-modified vinyl ester resin, a re-moldable urethane- modified vinyl ester resin, a water curable urethane-modified vinyl ester resin, a moldable bis-phenol epoxy vinyl ester, a re-moldable bis-phenol epoxy vinyl ester, a water curable bis-phenol epoxy vinyl ester, and combinations thereof.

26. The impact resistant composite material of claim 21 , wherein the resin material further comprises a cellular matrix.

27. A method of producing a impact resistant three-dimensional fiber preform, the method comprising: forming a three-dimensional fiber structure preform with at least three fiber systems such that two of the three fiber systems define an upper layer, a lower layer and a medial layer between the upper layer and the lower layer within the three-dimensional fiber structure preform, and wherein one of the at least three fiber systems interconnects the upper layer, the lower layer and the medial layer, wherein the at least three fiber systems each comprise a material selected from the group consisting of a reinforcing material, a thermoplastic material and combinations thereof, whereby an impact resistant three dimensional fiber preform is produced.

28. The method of claim 27, wherein the thermoplastic material is a moldable thermoplastic material or a re-moldable thermoplastic material.

29. The method of claim 27, wherein the fiber systems which define the upper layer and the lower layer comprise a reinforcing material and wherein the fiber systems which define the medial layer comprise a thermoplastic material.

30. The method of claim 27, further comprising forming a three- dimensional fiber structure preform selected from the group consisting of the following: three orthogonally woven fiber systems, a plurality of braided fiber systems, a plurality of circular woven fiber systems and combinations thereof.

31. The method of claim 27, further comprising forming the three- dimensional fiber structure preform so that the at least three fiber systems define a plurality of interstices within the three-dimensional fiber structure preform.

32. The method of claim 27, further comprising heat-molding the three-dimensional fiber structure preform or impregnating at least a portion of the three-dimensional fiber structure preform with a resin material to form an impact resistant composite material.

33. The method of claim 32, wherein the resin material is selected from the group consisting of a moldable resin, a re-moldable resin, a water curable resin, and combinations thereof.

34. The method of claim 32, wherein the resin material comprises a polymer.

35. The method of claim 34, wherein the polymer is selected from the group consisting of an epoxy resin, a urethane-modified vinyl ester resin, a bis- phenol epoxy vinyl ester, and combinations thereof.

36. The method of claim 35, wherein the polymer resin is selected from the group consisting of a moldable epoxy resin, a re-moldable epoxy resin, a thermosetting epoxy resin, a water curable epoxy resin, a moldable urethane-modified vinyl ester resin, a re-moldable urethane-modified vinyl ester resin, a water curable urethane-modified vinyl ester resin, a moldable bis- phenol epoxy vinyl ester, a re-moldable bis-phenol epoxy vinyl ester, a water curable bis-phenol epoxy vinyl ester, and combinations thereof.

37. The method of claim 32, further comprising foaming the resin material to form a cellular matrix within the resin material.

38. A conformable impact resistant composite material comprising:

(a) a three-dimensional fiber structure preform formed of at least three systems of fibers, wherein two of the three fiber systems define an upper layer, a lower layer and a medial layer between the upper layer and the lower layer within the three-dimensional fiber structure preform, and wherein one of the at least three fiber systems interconnects the upper layer, the lower layer and the medial layer, wherein the fiber systems that define the upper layer, the medial layer and the lower layer each comprise a reinforcing material; and

(b) a conformable resin material that impregnates at least a portion of the three-dimensional fiber structure preform.

39. The impact resistant composite material of claim 38, wherein the at least three fiber systems define a plurality of interstices within the three- dimensional fiber structure preform.

40. The impact resistant composite material of claim 38, wherein the three-dimensional fiber structure preform comprises three orthogonally woven fiber systems, a plurality of braided fiber systems, a plurality of circular woven fiber systems, or combinations thereof.

41. The impact resistant composite material of claim 38, wherein the conformable resin material is selected from the group consisting of a moldable resin, a re-moldable resin, a water curable resin, and combinations thereof.

42. The impact resistant composite material of claim 38, wherein the resin material comprises a polymer.

43. The impact resistant composite material of claim 42, wherein the polymer is selected from the group consisting of an epoxy resin, a urethane- modified vinyl ester resin, a bis-phenol epoxy vinyl ester, and combinations thereof.

44. The impact resistant composite material of claim 42, wherein the polymer resin is selected from the group consisting of a moldable epoxy resin, a re-moldable epoxy resin, a thermosetting epoxy resin, a water curable epoxy resin, a moldable urethane-modified vinyl ester resin, a re-moldable urethane- modified vinyl ester resin, a water curable urethane-modified vinyl ester resin, a moldable bis-phenol epoxy vinyl ester, a re-moldable bis-phenol epoxy vinyl ester, a water curable bis-phenol epoxy vinyl ester, and combinations thereof.

45. The impact resistant composite material of claim 38, wherein the resin material further comprises a cellular matrix.

46. A method of producing a conformable impact resistant composite material, the method comprising: (a) forming a three-dimensional fiber structure preform with at least three fiber systems such that two of the three fiber systems define an upper layer, a lower layer and a medial layer between the upper layer and the lower layer within the three-dimensional fiber structure preform, and wherein one of the at least three fiber systems interconnects the upper layer, the lower layer and the medial layer, wherein the fiber systems that define the upper layer, the medial layer and the lower layer each comprise a reinforcing material; and (b) impregnating at least a portion of the three-dimensional fiber structure preform with a conformable resin material to form the composite material.

47. The method of claim 46, further comprising forming the three- dimensional fiber preform so that the at least three fiber systems define a plurality of interstices within the fiber structure preform.

48. The method of claim 46, further comprising forming a three- dimensional fiber structure preform selected from the group consisting of the following: three orthogonally woven fiber systems, a plurality of braided fiber systems, a plurality of circular woven fiber systems and combinations thereof.

49. The method of claim 46, wherein the conformable resin material is selected from the group consisting of a moldable resin, a re-moldable resin, a water curable resin, and combinations thereof.

50. The method of claim 49, wherein the resin material comprises a polymer.

51. The method of claim 50, wherein the polymer is selected from the group consisting of an epoxy resin, a urethane-modified vinyl ester resin, a bis- phenol epoxy vinyl ester, and combinations thereof.

52. The method of claim 51 , wherein the polymer resin is selected from the group consisting of a moldable epoxy resin, a re-moldable epoxy resin, a thermosetting epoxy resin, a water curable epoxy resin, a moldable urethane-modified vinyl ester resin, a re-moldable urethane-modified vinyl ester resin, a water curable urethane-modified vinyl ester resin, a moldable bis- phenol epoxy vinyl ester, a re-moldable bis-phenol epoxy vinyl ester, a water curable bis-phenol epoxy vinyl ester, and combinations thereof.

53. The method of claim 46, further comprising foaming the resin material to form a cellular matrix within the resin material.