Patent Publication Number: US-2015072809-A1

Title: Article with protective sheath

Description:
The present application claims priority to U.S. Prov. Patent App. Ser. No. 61/875,144, filed on Sep. 9, 2013, which is incorporated herein in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to the addition of a protective sheath for providing enhanced performance and durability to at least part of an article specifically to sports equipment such as ice hockey sticks, field hockey sticks, lacrosse sticks, baseball/softball bats, and other articles comprising an elongated member/shaft and optionally a head portion such as a blade or webbing in a frame. 
     BACKGROUND OF THE INVENTION 
     Due to the competitive nature of many sports, players frequently seek ways to improve athletic equipment in order to gain a competitive advantage. Equipment manufacturers therefore investigate various materials and designs to enhance sports equipment performance. As can be appreciated, finding a suitable combination of materials and designs to meet a set of performance criteria such as being durable while remaining lightweight remains challenging and frequently different solutions are required for different sports articles. 
     For example, hockey sticks were initially made of wood. Over the years, composite hockey sticks have gained popularity notwithstanding having durability issues. Metal-containing hockey sticks based on aluminum have been proposed as well but they can suffer from a number of deficiencies including undesirable vibrations into the hands and arms of a player. A metal-containing hockey stick can also emit an undesirable high-pitch metallic sound upon impact with the puck. 
     Attempts have been made to address these deficiencies and multi-layered or multi-walled designs using different materials, such as metals, polymers, and composites have been proposed. While providing some benefits, these attempts can still be lacking in certain areas of performance, e.g., in terms of durability, feel and sound upon impact with a ball or puck. Moreover, some of these attempts can involve manufacturing techniques that are cumbersome and expensive. 
     Conventional hockey sticks comprise a shaft and an adjoining blade. The blade has a body and a neck that connects the body to the shaft. The blade has a heel at the end of the body below the neck and a toe disposed at end of the body opposite the heel. The body has two main faces, a front face and a rear face, that each extend from the heel to the toe. The front face comprises the primary puck striking surface of the blade. When viewed from above hockey stick blades are curved to form a forward facing “pocket”. The curvature of the blade plays a significant role in a player&#39;s ability both to control the puck and for accuracy when the player is shooting. As each player has his own preference with regard to the curvature of the blade manufacturers typically provide hockey sticks with many different shaped blades. Hockey stick blades with smooth faces can make handling of the puck at times challenging, i.e., it may be difficult to control the relative position of the puck and the blade, as well as to accurately move the puck along the surface of the blade when the two are in contact. Hockey players therefore often wrap a polymeric tape around their blades. 
     It is against this background that a need arose to develop the articles described herein. 
     SUMMARY OF THE INVENTION 
     In one aspect, the invention relates to a protective sheath for an article such as a sports article. The sports article can be any of a variety of sports equipment and associated components, e.g., a hockey stick and a lacrosse stick, various racquets and bats, and other such shafts comprising an elongated member/shafts/sticks and a head portion such as a blade, webbing in a frame, or tubular member/barrel designed to strike a ball or puck. 
     In one embodiment, the sports article is used in contact sports where, in addition to the contact between the sports article and the ball/puck or the ground, frequent contact between the sports article and the opposing player&#39;s sport article occurs such as in ice-, field-, ball- and street-hockey or lacrosse. The sport article must ideally be both lightweight and strong, however, these requirements are often incompatible and a reduction in weight often results in a loss of strength and/or durability. The sports article used in these games must be able to withstand a large number of impacts which often are concentrated at the edges and, over time, can result in increased damage to the structure and ultimately, premature failure. In addition, abrasion of selected surfaces such as the edges contacting the playing surface needs to be minimized. To improve the performance and durability a novel multi-layered protective sheath is applied to part or substantially the entire outer surface of the sports article. 
     The basic article typically includes a substrate made of reinforced composites such as carbon fiber, aramid fiber and glass fiber reinforced polymers and the inventive protective multi-layer sheath, comprising alternating layers of highly ductile and less ductile coatings, is applied to at least part of the outer surface thereof. 
     In one embodiment, the inventive protective sheath is composed of alternating layers of ductile/malleable materials and relatively rigid materials, i.e., alternating layers of materials of high and low ductility, i.e., defined herein as having an elongation to failure of &gt;10% or ≦10% as per ASTM E8, respectively. Each layer can be composed of sublayers, and the total layer thickness of each layer of high or low ductility is in the range of between 0.25 and 150 μm. 
     In one embodiment, the inventive protective sheath is composed of multiple layers comprising at least one polymeric material layer, representing the ductile layer, and at least one metallic material layer, representing the less ductile layer. 
     In one embodiment, the inventive protective sheath comprises at least one highly ductile polymer coating having a thickness between 25 and 150 μm, preferably between 50 and 100 μm, which is directly applied onto and intimately bonded with the reinforced composite sports article substrate. 
     In one embodiment, the inventive protective sheath polymer coating comprises at least one elastomer layer having a ductility greater than 10% elongation to failure, preferably equal to or greater than 15% and more preferably equal to or greater than 25% elongation to failure. 
     In one embodiment, the inventive protective sheath comprises an elastomer layer with an amorphous microstructure. 
     In one embodiment, the inventive protective sheath includes electrodeposited or electroformed metallic material layers of high ductility. 
     In one embodiment, the inventive protective sheath includes electrodeposited or electroformed metallic material layers of low ductility. 
     In one embodiment, the inventive protective sheath includes metallic material nanolaminates having sublayers having a thickness between 2 and 250 nm, preferably between 2 and 100 nm of high, low or alternating high and low ductility. In this case the “nanolaminate” is considered to represent one single “layer” and, depending on the ductility of the entire nanolaminate, the “layer” is considered to represent a layer of high or low ductility. 
     In one embodiment, the inventive protective sheath includes metallic material layers applied by electroless deposition. 
     In one embodiment, the inventive protective sheath comprises at least one fine-grained metal or metal alloy coating layer having a thickness between 20 and 100 μm applied, e.g., by electrodeposition. 
     In another embodiment, the inventive protective sheath comprises at least one grain-refined metallic material layer having an average grain size that is in the range of 2 nm to 100 nm, preferably an average grain-size between 15 and 75 nm, a hardness that is in the range of 300 Vickers to 1,000 Vickers, preferably between 300 and 750 Vickers, and a ductility that is in the range of 1 to ≦10% elongation to failure, preferably between 2 and 7.5% elongation to failure. 
     In one embodiment, the inventive protective sheath comprises at least one amorphous metal or metal alloy coating layer having a thickness between 0.5 and 10 μm and a ductility that is in the range of 0 to 5% elongation to failure, preferably in the range of 0.1 to 2.5%. 
     In one embodiment, the inventive protective sheath provides for a sports article that has an increased ability to withstand impact along its edges and sharp corners. 
     In one embodiment, the inventive protective sheath provides for an article such as a sports article with enhanced protection at the edges and sharp corners thereof. 
     In one embodiment, the sports article includes a graphite/metal composite shaft, tube or the like, incorporating a protective sheath representing at least 3%, such as at least 5% or at least 10% or at least 20%, and up to 40%, 50% or 75%, of the total weight of the article. 
     In one embodiment, the sports article includes a composite shaft, tube or the like, incorporating a protective sheath representing at least 3%, such as between 5% and 75%, preferably between 10% and 60%, and more preferably between 20% and 50% of the cross sectional weight of the article. 
     In one embodiment, the sports article includes a composite shaft, tube or the like, incorporating a protective sheath which covers between 10% and 100% of the outer length of the shaft, including up to 25% of the outer length of the shaft, up to 50% of the outer length of the shaft, up to 75% of the outer length of the shaft, and up to 100% of the outer length of the shaft. The protective sheath can be continuous or discontinuous, i.e., only the edges of the shaft can be covered by the protective sheath or the protective sheath forms a regular or irregular pattern with up to 25% of the outer surface area of the shaft, or up to 50% of the outer surface area of the shaft or even up to 75% of the outer surface area of the shaft being covered by the protective sheath. 
     In one embodiment, the addition of the protective sheath decreases the performance loss as measured by either flexural load to fracture or fatigue life after impact of the article by ≧20%, preferably ≧50% when compared to the same article without the addition of the protective sheath. 
     In one embodiment, the addition of the protective sheath to the sports article provides at least 10% increase in load failure, preferably at least 20% increase in load failure, and more preferably at least 30% increase in load failure. Further, the addition of the protective sheath to the sports article provides at least 5% increase in deflection to failure, preferably at least 10% increase in deflection to failure, and more preferably at least 15% increase in deflection to failure. 
     In one embodiment, the protective sheath applied to at least part of the outer surface of the article includes at least a first layer and a second layer adjacent to the first layer. At least one of the layers includes a polymeric material of high ductility and at least one of the adjacent layers includes a metallic material, preferably a grain-refined metallic material. 
     The person skilled in the art knows that grain-refined metallic materials can be formed as high-strength coatings of pure metals and/or alloys of metals selected from the group of Ag, Au, Co, Cu, Fe, Ni, Sn, Fe, and Zn, optionally with alloying elements selected from the group of Mo, W, B, C, P, S, and Si, and optionally metal matrix composites of pure metals or alloys with particulate additives, such as powders, fibers, nanotubes, flakes, metal powders, metal alloy powders, and metal oxide powders of Al, Co, Cu, Mg, Ni, Sc, Si, Sn, Ti, V, and Zn; nitrides of Al, Sc and Ti, B and Si; C (e.g., graphite, diamond, nanotubes); carbides of B, Cr, Bi, Si, and W; and self-lubricating materials such as MoS 2  or organic materials such as PTFE. Depending on the composition, the average grain size and the use of particulate additions, the ductility of the grain-refined metallic materials can extend from highly brittle to highly ductile, with the elongation to failure ranging from as low as much less than (&lt;&lt;) 1% to as high as much greater than (&gt;&gt;) 30%. Electroplating can be employed as the process for creating high strength coatings on metallic components or on non-conductive components that have been metallized to render them suitable for plating. In an alternative embodiment, the process can be used to electroform a stand-alone metallic article on a mandrel or other suitable temporary substrate and, after reaching a desired plating thickness, the free-standing electroformed article can be removed from the temporary substrate such as described, e.g. in PCT Publication No. WO 2004/001100, U.S. Pat. No. 8,025,979 and U.S. Pat. No. 7,553,553, the disclosures of which are incorporated herein by reference in their entirety. 
     In an embodiment of the invention, electrodeposited metallic coatings/layers optionally contain between 2.5% and 50% by volume particulate. The particulate can be selected from the group of metal powders, metal alloy powders, and metal oxide powders of Al, Co, Cu, In, Mg, Ni, Si, Sn, V, and Zn; nitrides of Al, B, Sc, Si and Ti; C (e.g., graphite or diamond); carbides of B, Cr, Si, and W; MoS 2 ; and organic materials such as PTFE and other polymeric materials. The particulate average particle size is typically below 10 μm, such as below 5 μm, below 1,000 nm (or 1 μm), or below 500 nm. 
     In one embodiment of the invention, after forming, the protective sheath is heat-treated to achieve added strengthening and enhance bonding between layers or alter the mechanical material properties of one or more of its layers. 
     According to an embodiment of the invention, the protective sheath can be formed on selected areas of articles, such as on hockey blades and sticks, lacrosse sticks, baseball bats, golf club face plates or sections of golf club shafts, frames or other parts for bicycles, and the like, without the need to coat an entire article. 
     According to an embodiment of the invention, patches or sleeves of grain-refined materials, which need not be uniform in thickness or composition, can be electrodeposited in order to, e.g., form a thicker coating on selected sections or sections particularly prone to heavy use or abuse, such as the bottom edge or face of hockey stick blades which are in frequent contact with the playing surface or the edges of the stick prone to being contacted by another player&#39;s stick. 
     According to an embodiment of the invention, the protective sheath can be graded or layered in the deposit direction and/or along the length as described in US 2011/0256356, the disclosure of which is incorporated herein by reference in its entirety. 
     Accordingly, the present invention in one embodiment is directed to a hockey stick comprising: 
     (i) a shaft portion comprising fiber reinforced composite materials and including a distal or grip end and a proximal end, and a blade portion connected to the proximal end of the shaft portion; and 
     (ii) a protective sheath covering at least an edge of the proximal end of the shaft portion up to 100% of an outer length of the shaft portion; said protective sheath representing &lt;50% of the total overall weight of said hockey stick; said protective sheath being composed of a multi-layer structure comprising at least two layers each having a thickness between 0.25 and 150 μm; said multi-layer structure comprising a polymer layer having a bulk tensile elongation to failure of &gt;10% in intimate contact with the fiber reinforced composite material of the shaft portion of the hockey stick followed by at least one metallic layer having a bulk tensile elongation to failure of ≦10%. 
     Accordingly, the present invention in another embodiment is directed to a hockey stick comprising: 
     (i) a shaft portion including a distal or grip end and a proximal end, and a blade portion connected to the proximal end of the shaft portion, each of the shaft portion and blade portion comprising fiber reinforced composite materials; and 
     (ii) a protective sheath covering at least outer edges of the blade portion and extending beyond at least an edge of the proximal end of the shaft portion up to 50% of an outer length of the shaft portion; said protective sheath having a surface roughness R a  in the range of 2.5 to 15 μm and representing between 3 and 50% of the total overall weight of said hockey stick; said protective sheath being composed of a multi-layer structure containing at least two layers, preferably at least three or four layers, each layer having a thickness between 0.25 and 150 μm; preferably between 0.5 and 100 μm, and a total overall thickness between 50 and 250 μm; preferably between 75 and 150 μm, said multi-layer structure comprising alternating layers having an elongation to failure of ≦10% and layers having an elongation to failure of &gt;10%; said multi-layer structure comprising a polymer layer having an elongation to failure of &gt;10% in intimate contact with the fiber reinforced composite material of the hockey stick followed by one metallic layer having an elongation to failure of ≦10%; followed by another metallic layer having an elongation to failure of &gt;10%; followed by another metallic layer having an elongation to failure of ≦10% and a minimum yield strength according to ASTM E8 of 600 MPa. 
     Accordingly, the present invention in another embodiment is directed to a hockey stick comprising: 
     (i) a shaft portion including a distal end and a proximal end, and a blade portion connected to the proximal end of the shaft portion, each of the shaft portion and blade portion comprising fiber reinforced composite materials; and 
     (ii) a protective sheath covering at least outer edges of the blade portion and extending beyond at least an edge of the proximal end of the shaft portion up to 50% of an outer length of the shaft portion; said protective sheath having a surface roughness R a  in the range of 2.5 to 15 μm and representing between 3 and 50% of the total overall weight of said hockey stick; said protective sheath being composed of a multi-layer structure containing at least four layers each having a thickness between 0.25 and 150 μm; said multi-layer structure comprising alternating layers having an elongation to failure of ≦10% and layers having an elongation to failure of &gt;10%; said multi-layer structure comprising a polymer layer having an elongation to failure of &gt;10% in intimate contact with the fiber reinforced composite material of the hockey stick and at least one metallic layer having an elongation to failure of ≦10% selected from the group of Co, Cu, Fe and Ni having an average grain size that is in the range of 2 nm to 5,000 nm, a yield strength in the range of 200 MPa to 2,750 MPa, and a hardness in the range of 300 Vickers to 1,000 Vickers. 
     Accordingly, the present invention in another embodiment is directed to a hockey stick comprising: 
     (i) a shaft portion including a distal end and a proximal end, said shaft portion comprising a top face and a front face, said top face being narrower than said front face and oriented perpendicular to said front face, and a blade portion connected to the proximal end of the shaft portion; and 
     (ii) a protective sheath comprising at least one metallic layer covering at least part of an outer length of said shaft portion; 
     wherein said shaft portion having the protective sheath has a loss of peak load performance measured on the front face of less than 30% after being subjected to an impact force of 15 J on the top face, i.e., perpendicular to the initial impact, said peak load performance being determined by securely mounting said shaft portion on two locations 50 cm apart and applying the load half way between the mounting locations using a ½″ diameter load element. 
     Accordingly, the present invention in another embodiment is directed to an article comprising a shaft portion comprising a fiber reinforced polymer: 
     (i) said shaft portion including a distal or grip end and a proximal end, said shaft portion comprising a top face and a front face, said top face being oriented perpendicular to said front face; and 
     (ii) a protective sheath comprising at least one metallic layer covering at least part of an outer length of said shaft portion; 
     wherein said shaft portion having said protective sheath after a 15 J impact on the top face has an average peak load value on the front face exceeding the average peak load value on the shaft portion devoid of said protective sheath and not subjected to the 15 J impact, wherein said peak load value is determined by securely mounting said shaft portion on two locations 50 cm apart and applying the load or impact force half way between the mounting locations using a ½″ diameter load element. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a better understanding of the nature and objects of some embodiments of the invention, reference should be made to the following detailed description taken in conjunction with the accompanying drawing. 
         FIG. 1  illustrates a perspective view, taken from the front of an article (e.g., a hockey stick) according to one embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the invention relate to one or more protective sheaths to be applied to lightweight articles, such as sports articles, e.g., hockey sticks, lacrosse sticks, baseball or softball bats, tennis, squash, racquetball and badminton racquets and the like. 
     The exemplary article of the present invention, by way of example only, will be described hereinafter in relation to ice hockey sticks, but it is understood that the invention herein described and claimed may be suitably adapted to other applications and in particular to other sports. 
     Specifically to hockey sticks, some hockey shafts use a solid construction while others comprise a hollow core. Most blades are solid but they can contain foam inserts such as polyurethane foam. Shafts and some blades of a composite construction comprise various layers of materials sandwiched together. Wood-based hockey sticks are inexpensive but heavy while aluminum-based hockey sticks are prone to buckling failure. Composite hockey sticks with numerous plies of reinforcing fibers embedded in a polymer matrix have rapidly gained popularity. Composite hockey sticks are, however, particularly vulnerable to failure along their edges, i.e., where one side surface intersects with an adjacent side surface, often at an angle of close to 90°. Impacts are often concentrated at these edges and hockey sticks that are subject to repeated impact on their edges rapidly wear out, with paint and decals wearing off, and nicks and gouges forming therein, or they simply break and fail catastrophically, frequently at inopportune times during a game. In the case of hockey sticks, the damaging impacts typically occurs on a top face of the shaft by being impacted repeatedly with other sticks, while breakage usually occurs on a front face of the shaft when shooting the puck, when bending the hockey stick perpendicular to the top face typically exposed to the damaging impacts. Similar situations occur with other shafts/stick used in sports which have similar or different cross sections, such as a lacrosse stick which typically has eight different faces. 
     Modern hockey sticks, for example, can comprise one or more reinforcing fibers such as carbon fiber, aramid fiber and glass fibers embedded in a polymer matrix. It is known that upon impact fiber cracking, delamination of the individual plies, and fiber matrix debonding can occur, significantly reducing the residual strength of the composite structure, even though no visible damage is observed and catastrophic failure, e.g., “unexpected” breaking of the hockey stick, can ultimately result. 
     Therefore there is a need to improve the performance of reinforced composite material structures with respect to energy absorption, damage resistance, performance and durability. This enhancement is achieved by applying a protective sheath according to the present invention to at least part of an outer surface of the article, such as sports articles prone to similar failure modes (e.g., hockey sticks). 
     Articles in accordance with various embodiments of the invention can be formed by applying one or more protective sheaths having a number of desirable performance characteristics. Examples of sports articles include a variety of sports equipment and associated components, such as hockey sticks, hockey skate frames, lacrosse sticks, golf club heads, golf face plates, golf shafts, baseball bats, softball bats, tennis rackets, squash rackets, racquetball rackets, bicycle frames, bicycle seat posts, bicycle linkage systems, bicycle handle bars, bicycle front forks, bicycle disc brakes and bicycle wheels, protective gear for, e.g., hockey and motorsports such as helmets, shin guards, elbow pads, shoulder pads, knee pads, to name a few. Similarly, aerospace and defense fiber reinforced composite components, construction equipment and the like may benefit from the application of the protective sheath disclosed herein. 
     DEFINITIONS 
     The following definitions apply to some of the features described with respect to some embodiments of the invention. These definitions may likewise be expanded upon herein. 
     As used herein, the singular terms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, a reference to an object can include multiple objects unless the context clearly dictates otherwise. 
     As used herein, the term “adjacent” refers to being near or adjoining. Objects that are adjacent can be spaced apart from one another or can be in actual or direct contact with one another. In some instances, objects that are adjacent can be coupled to one another or can be formed integrally with one another. 
     As used herein, the terms “integral” and “integrally” refer to a non-discrete portion of an object. Thus, for example, a hockey stick including a shaft portion and a blade portion that is formed integrally with the shaft portion can refer to an implementation of the hockey stick in which the shaft portion and the blade portion are formed as a monolithic unit. An integrally formed portion of an object can differ from one that is coupled to the object, since the integrally formed portion of the object typically does not form an interface with a remaining portion of the object. 
     As used herein, the term “shaft” or “shaft portion” refers to a long, slender, and comparatively straight member or handle on various sporting goods, instruments and tools such as hockey and lacrosse sticks, golf clubs and hammers, 
     As used herein, the term “layer” refers to an individual layer which, in the case of a “layer of high ductility” has or all have an elongation to failure of &gt;10% as measured in conformance with ASTM E8 using a specimen thickness greater than 0.3 mm or in the case of a “layer of low ductility” has or all have an elongation to failure of ≦10% as measured in conformance with ASTM E8 using a specimen thickness greater than 0.3 mm. 
     As used herein, the term “metallic coating” or “metallic layer” means a metallic deposit/layer applied to part of or the entire exposed surface of an article. The substantially porosity-free metallic coating is intended to adhere to the surface of a substrate to provide mechanical strength, wear resistance, corrosion resistance, and a low coefficient of friction. 
     As used herein the term “laminate” or “nanolaminate” means a metallic material that includes a plurality of adjacent “sublayers” each having an individual thickness between 2 nm and 250 nm. A “sublayer” of a laminate or nanolaminate means a single thickness of a substance where the substance may be defined by a distinct composition, microstructure, phase, grain size, physical property such as ductility, chemical property or combinations thereof. It should be appreciated that the interface between adjacent layers may not be necessarily discrete but may be blended, i.e., the adjacent layers may gradually transition from one of the adjacent layers to the other of the adjacent layers. 
     As used herein the term “graded material” means a material having at least one property in the deposition direction modified by at least 5%. 
     As used herein the term “compositionally modulated material” means a material whose chemical composition is continuously, periodically or abruptly altered in the deposition direction. 
     As used herein the term “average thickness” or “average coating/layer thickness” is the arithmetic average of the applied layer thickness as determined, e.g., by the total weight of the layer/coating applied, its density and the surface area of the layer/coating and refers to depth of a layer in a deposit direction. 
     As used herein the term “directions” refers to the three dimensional Cartesian coordinate system defining the three physical directions/dimensions of space—length, width, and height which are perpendicular to each other. The depth or height of a deposited layer is defined by the deposition direction as indicated hereinafter and indicates the thickness of the deposit layer. Length and width directions are perpendicular to the depth or height direction. If a substrate to be plated is a plate, line-of-sight deposits occur perpendicular to the plate in the height direction defining the thickness of the deposit layer. If a substrate to be plated is cylindrical in shape such as a tube the length is the axial direction and deposition occurs in radial direction. 
     As used herein the term “chemical composition” means the chemical composition of a layer or structure. 
     As used herein, the term “microstructure” refers to a microscopic configuration of a material. The microstructure can be crystalline, i.e., composed of grains, amorphous, i.e., a glassy structure without grains, or combinations, i.e., amorphous sections embedded in crystalline sections or vice versa. In the case of metallic materials crystalline microstructures can be coarse-grained (average grain-size &gt;5 μm) or grain-refined (average grain-size ≦5 μm). 
     As used herein, the term “grain size” refers to a size of a set of constituents such as crystallites/grains forming the microstructure of a material, such as a grain-refined material. When referring to a material as being “fine-grained” or “grain-refined”, it is contemplated that the material can have an average grain size in the submicron range, such as in the nm range. 
     As used herein, the term “ductile” is a material property that allows a material to be stretched or otherwise changed in shape without breaking and to retain the changed shape after the load has been removed. The ductility of a material such as a metal or polymer is reported in percent elongation to failure and can be determined from a stress-strain curve obtained from a tensile test. For the purpose of the present invention materials with high ductility are defined as having a percent elongation to failure of over 10%, preferably at least 15%, whereas materials with low ductility are defined as having a percent elongation to failure of no more than 10%, typically ≦7.5%. For the purpose of this invention the ductility values of metallic materials are determined by measuring bulk material specimens greater than 0.3 mm in thickness in conformance with ASTM E8 or a similar accepted tensile test specification. Ductility values of polymeric materials are determined by, e.g., ASTM D412-06a or ASTM D624-00. Ductility values of fiber reinforced composites are determined by, e.g., ASTM D7205. 
     As used herein the term “stress-strain curve” refers to a curve generated during tensile testing of a material sample and the “stress-strain curve” is a graphical representation of the relationship between the applied stress, derived from measuring the load applied on the sample, and the strain, derived from measuring the deformation of the sample, i.e., the elongation, compression, or distortion. 
     As used herein the term “elastomer” or “elastomeric material” is a polymeric material exhibiting viscoelasticity, characterized by a low Young&#39;s modulus and high ductility (failure strain &gt;&gt;100%). The term, which is derived from elastic polymer, is often used interchangeably with the term rubber. Elastomers usually have an amorphous microstructure and exist above their glass transition temperature, so that considerable segmental motion is possible. Elastomers are soft and readily deformable. Elastomers are usually thermosets (requiring vulcanization) but may also be thermoplastics. 
     Fiber Reinforced Polymer Composites 
     Fiber-reinforced polymers (FRP) are composite materials comprising a polymer matrix reinforced with fibers. The fibers are usually composed of glass, carbon/graphite, or aramid, although other fibers such as metal fibers or metal coated carbon fibers can be used. The polymer is usually an epoxy, vinylester or polyester thermosetting plastic, and/or phenol formaldehyde resin. FRPs are commonly used in the sporting goods-, aerospace-, automotive-, marine-, and construction-industry and are readily available commercially from a variety of vendors. 
     Fiber-reinforced polymers exhibit limited ductility and the failure strain ductility is typically in the range of 1-3% as determined by, e.g., ASTM D7205. The inventive protective sheath is particularly suited to overcome the shortcomings of articles, including, but not limited to, sports articles made from fiber reinforced composite materials. 
     Elastomers/Elastomeric Materials 
     Suitable elastomeric materials are electrically non-conductive and comprise one or more materials selected from the group consisting of thermoset elastomers, thermoplastic elastomers, thermoset elastomeric urethanes, thermoplastic polyurethanes, thermoset elastomeric dicyclopentadienes, elastomeric urethanes, silicones, rubbers, polyisoprenes, polybutadienes, polyisobutylenes and latex based materials and are readily available commercially from a variety of vendors. Elastomeric material layers, e.g., rubber toughened epoxy compositions containing at least 10% rubber, are typically cured at elevated temperatures (up to 150° C.) which can occur within the molding tooling or thereafter. 
     Elastomers exhibit significant ductility and the failure strain ductility is typically &gt;10%, typically &gt;25%, more typically &gt;100% and as high as 800% as measured by ASTM D412-06a or ASTM D624-00. 
     Metallic Materials 
     For the purpose of this invention suitable metallic materials include highly ductile metals and alloys (&gt;10% elongation to failure) and metallic materials of limited ductility (≦10% elongation). 
     Poorly ductile metallic materials in this context can include selected grain-refined and amorphous metallic materials with a ductility in the range of &lt;1 to 10%, typically ≦7.5%. 
     Poorly ductile metallic materials include amorphous Ni—P based alloys which are conveniently applied by, e.g., electroless deposition processes available from a number of commercial vendors which range in ductility between 0.1 and 2.5%. A number of Ni-based or Cu-based poorly ductile coatings can be deposited using an electroless plating process and are used for metallizing non-conductive substrate to render them suitable for electroplating. 
     Metallizing layers which are ductile include, among other, Ag and Cu based electroless coatings which can be applied by an immersion, painting or spraying process. 
     Preferred metallic materials include grain-refined materials although coarse-grained metallic materials can be used as well. Preferred grain-refined metallic materials include: (1) metals selected from the group of Co, Cu, Fe and Ni; (2) alloys formed of two or more of these metals; and (3) metal alloys formed of these metals along with an alloying component selected from the group of B, C, Mo, P, S, Si, and W. In some instances, a grain-refined material can be formed as a metal matrix composite in which a metal or a metal alloy forms a matrix within which a set of additives are dispersed. Particularly useful additives include particulate additives formed of metal oxides, nitrides of Al, B, Sc, Si and Ti; carbides of B, Bi, Cr, Si, and W, C such as in the form of graphite, diamond, and nanotubes, and polymers. Suitable particulate additives have an average particle size ≦25 μm, preferably ≦10 μm, more preferably ≦1 μm, and even more preferably ≦0.5 μm. Depending on specific characteristics that are desired, the particulate additives comprise ≦50% by volume, such as 5-25% by volume. 
     The person skilled in the art will know that the ductility of metallic materials is not an inherent material property and can be adjusted by various means such as the method of synthesis, microstructure, mechanical deformation, heat treatment, etc., and, in the case of thin layers, depends on the thickness of the layer tested, with thicker layers usually showing higher ductility values. Furthermore changing the composition by even adding minor alloying elements can have a drastic effect on the ductility/elongation as is well known for iron which can range in ductility between 0.5 and 30%. Similar rules apply to other metals and alloys. As another example, the ductility of pure Ni or pure Cu has been reported to range from about 0.5% to about 60%, specifically to pure Ni or Cu prepared by electrodeposition, the ductility has been reported to range from as low as 0.5% to as high as 30%. Ni or Cu based metallic materials prepared by electrodeposition are therefore particularly suited for practicing the present invention as they can be formed to have high or low ductility, as desired. Ni or Cu layers, depending on the specific design requirements, can be very ductile and relatively soft, i.e., having a ductility of &gt;10% or, alternatively, exhibit low ductility but with increased yield strength. 
     Electrodeposition is a particularly well suited process for forming selected layers of the protective sheath by providing the flexibility to plate layers of high or low ductility, as desired, build up the desired layer thickness, and grade and/or layer the deposits appropriately, as required. In addition, laminates or nanolaminates, defined as having a sublayer thickness of ≦250 nm and as small as ≦100 nm, can be conveniently prepared using electroplating techniques as well. It is known that mechanical properties of structures such as yield strength, hardness, modulus of elasticity and ductility can be controlled by controlling the thickness and/or the composition and/or the microstructure of the metallic layers. 
     An example for using electrodeposition for forming one or more metallic layers of the protective sheath comprises plating Cu and/or Ni-based layers out of a single plating bath by suitably adjusting the electrical plating conditions. At very low average current densities mainly Cu rich layers are deposited, at medium average current densities Ni—Cu alloys are deposited, while at high average current densities mainly Ni rich layers are deposited. Adding, e.g., forward and/or reverse pulsing to the electrical waveform, the strength and ductility of each layer can be tuned even further to achieve the desired mechanical properties. Using this approach, e.g., ductile Cu followed by high-strength Ni layers can be formed in a single plating cell. Furthermore “compositionally or ductility modulated” layers and/or nanolaminates can be formed. In addition, Cu-rich and/or Ni-rich Ni—Cu alloy layers with the desired mechanical properties can be conveniently formed in a single plating cell economically and at high production speeds. Similar rules apply to many more binary systems, including Cu—Co, Ni—Co, Ni—Fe, and Co—Fe systems. 
     Sports Articles comprising the Protective Sheath 
       FIG. 1  illustrates an exemplary sports article  10  implemented in accordance with an embodiment of the present invention.  FIG. 1  depicts a frontal view of a right-handed ice hockey stick  10 . A mirror image of the hockey stick  10  would constitute a left-handed embodiment. 
     The hockey stick  10  comprises a shaft or shaft portion  100  and a blade or blade portion  200 . The shaft  100  and blade  200  can be integrally formed, conventionally referred to as a “one-piece hockey stick” or, the shaft and blade can be formed separately, referred to as a “two-piece hockey stick”. 
     The shaft  100  at its lower end  102 , also termed its proximal end, is joined to the blade  200 , and the opposite distal end  104 , also termed its grip end, provides for the grip/handle. In this embodiment, the shaft  100  has a rectangular cross-section with the rectangle typically having rounded corners, and having a rear face  106 , opposite a front face  108 , and a top face  110  opposite a bottom face  112 . Shafts can also have different shaped cross-sections. 
     The blade  200  has a blade body  202 , a neck  203 , a heel  204  and a toe  206 . The blade  200  has a rectangular cross-section with rounded edges, having a front face  208 , a rear face  210  opposite the front face  208 , a top face  212  and a bottom face  214 . The inventive protective sheath reinforcement  220  covers at least part of the blade  200  and at least part of the shaft  100 , preferably up to ¼ or ½ of the length of the shaft  100 . The protective sheath  220  preferably forms a continuous outer face, i.e., it covers and encapsulates the entire blade  200  and the entire circumference of the shaft  100  up to a designated outer length of the shaft past an edge of the proximal end  102 , if any, between the blade  200  and the shaft  100 , to cover the entire “slash zone” which according to one aspect can extend to about half way up the outer length of the shaft to  222 . Optionally, a polymeric layer such as an elastomeric layer  230  is applied to at least part of a puck striking surface such as the blade front face and/or rear face to resist slippage of the puck on the blade and improve puck trajectory, speed and shot accuracy. 
     While  FIG. 1  shows one preferred embodiment, the present invention also includes sport articles, such as hockey sticks, where the blades are partly covered or not covered with the protective sheath. In addition, the present invention applies to shafts for sport articles (e.g., hockey sticks, lacrosse sticks and the like) where the protective sheath covers between 10 and 100% of an outer length of the shaft, including up to 25% of the outer length of the shaft, up to 50% of the outer length if the shaft, up to 75% of the outer length of the shaft, and up to 100% of the outer length of the shaft. The protective sheath can be continuous or discontinuous, i.e., only the edges of the shaft can be covered by the protective sheath or the protective sheath forms a regular or irregular pattern with up to 25% of the outer surface area of the shaft, or up to 50% of the outer area of the shaft or even up to 75% of the outer area of the shaft being covered by the protective sheath. 
     Sport articles (e.g., hockey sticks) of the present invention may be made of any suitable conventional construction using natural materials (wood), synthetic materials (polymers) or combinations (laminated wood). In this embodiment, the hockey stick  10  is made of a carbon fiber reinforced polymer (CFRP) composite and the shaft  100  is hollow whereas the blade  200  is made of a solid construction but containing foam inserts. Other suitable fiber reinforced materials include glass fibers and/or aramid-based fibers.  FIG. 1  depicts a hockey stick for a defense or attacking player, however, goalie sticks, too, are within the scope of the invention. The person skilled in the art will appreciate that goalie sticks are typically longer and heavier than hockey sticks for open-ice players, contain a paddle and have a wider and longer blade. In this case at least part of the paddle, preferably the entire paddle is included in the protective sheath. Dimensions of the hockey sticks are typically governed by the various game associations&#39; regulatory bodies, e.g., the National Hockey League (NHL). 
     As indicated, the basic sports article providing the substrate for the exemplary protective sheath can be formed of any suitable materials such as fibrous materials, ceramics, metals, metal alloys, polymers, or composites. 
     The use of specific materials and other specific implementation features of the protective sheath can further enhance performance characteristics of the article. For example, the overall thickness and thickness distribution of the protective sheath can contribute to the performance characteristics but also add to the overall weight. It is contemplated that the protective sheath is applied so as to selectively cover those portions of the sports article that are likely to come into contact with a ball/puck, the playing surface or another stick during use, thus providing an improved hitting surface. It is also contemplated that the protective sheath can be distributed so as to selectively cover those portions of the sports article that are likely to come into contact with a player&#39;s hands during use, such as the handle portion and/or those portions likely coming into contact with another player&#39;s sports article. It is also contemplated that the protective sheath can be distributed so as to selectively cover the edges of the sports article prone to abuse with much less or no coverage in the sections not prone to failure such as the puck striking surface of the blade and the fairly flat front and rear faces of the shaft. 
     The use of specific materials, their respective weights and thicknesses and other specific implementation features, can further enhance performance characteristics of the sports article. In order to minimize the weight, e.g., the blade may only be coated around the periphery such as from the heel, around the bottom face, around the toe and all the way around to the top face between about ¼ to 1″ wide without having a metallic coating in the center portion/main puck striking area. Alternatively, the coating thickness in less critical areas can simply be reduced significantly, e.g., to less than ½ or even less than ¼ of the thickness of the areas prone to failure, and the entire blade and slash zone of the hockey stick can be encapsulated. 
     The use of the protective sheath can allow the sports article to exhibit improved performance characteristics, such as a desired weight, enhanced balance, enhanced durability, and enhanced coupling strength to the stick portion. Also, the use of the protective sheath can alter a vibrational frequency response of the sports article, thus providing a desired feel upon impact with a ball or puck. 
     Implementations of the Protective Sheath 
     In one preferred embodiment, the sports article receiving the protective sheath is a hockey stick comprising a shaft and a blade made of a reinforced composite. The reinforcing material preferably is carbon/graphite fiber, however additions and/or substitutions with glass fiber and Kevlar® fibers are within the scope of the invention. For open-ice players the shaft of the hockey stick is about 60″ long and the slash zone extends about half way up (about 30″) the outer length of the shaft from the blade connection. The CFRP hockey stick forming the “substrate” has a weight of about 420 g, qualifying it as a “lightweight hockey stick”. The CFRP hockey stick has an elongation to failure of about 2% as measured by 3-point bending, similar fiber reinforced hockey sticks range in elongation to failure between 1 and 5%. 
     In preparation for applying the inventive protective sheath the outer surface of the hockey stick blade (e.g., the entire outer surface) all the way up to the end of the slash zone is mechanically abraded to 500 grid equivalent or a surface roughness R a  of ≦0.1 μm. After degreasing a first ductile elastomeric layer comprising polyisoprene, such as suitable rubber toughened epoxy compositions, is applied in one or more applications such as spraying, painting or dipping to achieve an average elastomeric layer thickness after curing of between 25 and 150 μm, preferably between 50-100 μm. The ductility of the elastomeric layer is &gt;10%, preferably &gt;25% and as high as &gt;100%. After curing, the ductile elastomeric layer, comprising at least 10% by weight of polyisoprene, preferably fully encapsulates the blade and slash zone of the shaft and has a surface roughness R a  of between 2.5-15 μm. Subsequently the first elastomeric layer is suitably activated by various swelling and/or etching treatments to receive a second layer, specifically a layer of low ductility, such as a brittle metallic layer, e.g., by suitably applying a metallizing layer of an amorphous Ni-based alloy, e.g., Ni with 3-15% P. The non-ductile average layer thickness is typically &lt;10 μm, preferably between 0.5- and 5 μm, and more preferably between 1- and 2 μm and has a ductility of &lt;2%. Optionally, the puck striking surface in the center of the blade on the front face and/or rear face may not be metallized if it is not to be plated subsequently, to minimize the added weight. 
     Thereafter a third layer, specifically a ductile metallic layer, is applied to the second layer, e.g., by electrodeposition. A suitable ductile metallic layer comprises pure Cu or a Cu rich alloy having an average layer thickness between 0.5 and 40 μm, preferably between 0.5 and 25 μm, more preferably between 0.75- and 12.5 μm, and a ductility &gt;10%, preferably &gt;15%. Areas not previously metallized lack sufficient conductivity and therefore do not receive an electrodeposited coating. Alternatively areas not to be plated can be masked, as needed. 
     Thereafter a fourth layer, specifically a relatively strong metallic layer of limited ductility is applied to the third layer, e.g., by electrodeposition. The strong layer can preferably comprise grain-refined metallic materials, e.g., Ni-based layers, such as Ni with 10-50% Co or Ni-low P (0.1-3%) or Ni—Fe based layers, as well as Co-low P (0.1-3%) or Co—Fe layers, or Ni—Co—Fe, or Ni—Co—Fe-low P (0.1-3%) layers, or Ni—Cu layers having an average grain size in the range of 2-100 nm, preferably between 5 and 50 nm. The average thickness of the grain-refined layer is typically between 20 and 100 μm, preferably between 30 and 75 μm, and has a ductility between 1 and 10%, preferably between 2.5 and 7.5%. Preferably the thickness of the strong metallic layer at the bottom face of the blade contacting the playing surface is about 50% thicker than the average thickness of the coating, i.e., in the case of an overall strong metallic layer average thickness of 40 microns, the bottom face of the blade contacting the playing surface is increased to between 60 and 75 μm. The use of other grain-refined and/or amorphous strong metallic layers is contemplated as well, provided the hardness of the layer ranges between 250 and 750VHN, a minimum yield strength according to ASTM E8 is 600 MPa, preferably 900 MPa, the maximum yield strength is 2,000 MPa, preferably 2,500 MPa, and the minimum Young&#39;s modulus according to ASTM E8 is 75 MPa, preferably 100 MPa, and the maximum Young&#39;s modulus is 250 GPa, preferably 500 GPa. 
     The total thickness of the protective sheath applied to the sports article (e.g., hockey stick) is in the range of 50 to 350 μm, preferably in the range of 100 to 250 μm and the added weight between 20 and 40 g and the surface roughness R a  of the protective sheath outermost layer is between 2.5-15 μm. The elastomeric layer and the strong metallic layer of low ductility preferably are the two thickest layers applied. The elastomeric layer typically is the layer of the highest overall thickness and is about as thick as all metallic layers combined. The relatively strong layer typically represents the metallic layer of the highest thickness. 
     Optionally a fifth layer is applied to the fourth layer, which can be another ductile elastomeric layer with the same or similar properties and dimensions as the first layer. The fifth layer preferably is only applied to the blade itself, specifically to part or all of the blade front face and/or rear face specifically designed to predominantly handle and shoot the puck as illustrated in  FIG. 1 , although other shapes as depicted in the figure are within the scope of the invention. 
     Additional decorative layers can be applied to the protective sheath such as suitable decals, a clear coat etc. remaining within the scope of the invention as long as they are &lt;10% of the total thickness of the protective sheath. 
     The description above for forming the exemplary protective sheath on a substrate of a sports article (e.g., hockey stick) is not meant to be limiting and the person skilled in the art will appreciate that the exemplary protective sheath can be applied by other means. For instance, the protective sheath can be formed from the outside in instead of the inside out, e.g., by starting out with the metallic layer and, e.g., applying the adhesive elastomeric layer to a metallic layer. 
     The inventors have surprisingly discovered that the addition of a protective sheath with at least two, but preferably with at least three, four or five layers as described applied to a CFRP substrate of a hockey stick with a total added weight of between 10 and 50 g, preferably between 20 and 40 g, provides a good balance between weight and durability with much enhanced fatigue life after impact. It has also surprisingly been found that the sequence of the layers is important and the durability of hockey sticks, for example, of equivalent weight comprising alternating layers of ductile and brittle materials is superior to hockey sticks containing identical layers in a different sequence or without regularity, i.e., applying a ductile layer on another ductile layer or a strong, relatively brittle layer on another strong, relatively brittle layer. For open ice players it is typically advantageous to have the strong layer of low ductility as the outermost functional layer (not considering thin decorative finishing layers) although a further polymeric insert of high ductility on the blade may provide for better puck control, or the designated puck striking area may not be metal coated at all to minimize the added weight, as described. In the case of a goalie stick it has been found to be advantageous to have a relatively thick elastomeric layer as the most outer functional layer (not considering thin decorative finishing layers) on one or both faces of the blade, particularly the rear face of the blade. Applying a thick ductile layer to the entire paddle of the goalie stick which, in the NHL, typically has a maximum length of 26 inches, can assist in limiting the puck rebound distance. 
     A further advantage of the inventive protective sheath is that it can be either readily added to the existing reinforced hockey stick manufacturing process or conveniently added later as a retrofit. Layer properties, sequence and thicknesses can also be easily adjusted to meet players&#39; personal preferences. 
     As an example, the peak load to failure of various carbon fiber reinforced hockey sticks with and without the exemplary protective sheath was investigated. The protective sheath comprised a 75 μm 33% polyisoprene containing elastomeric layer vulcanized at 140° C. and built up to thickness with two applications, a 1.5 μm thick metallizing layer of low ductility amorphous Ni-7P, a 10 μm layer of ductile electrolytic Cu and a 50 μm strong grain-refined layer of Ni-30Co as indicated in Table 1. The shafts were securely mounted on two locations 50 cm (19.7″) apart and the three-point flexure strength to failure expressed in Newtons was determined by applying a load using an Instron Universal Tester unit half way between the mounting locations on the wider side of the hockey stick (about 1″ wide front face;  108  in  FIG. 1 ) using a ½″ diameter load element. The peak load at failure was recorded. “New” hockey sticks and hockey sticks having been subjected to an impact load of 15 Joules with a ½″ diameter load element were tested. To simulate impact damage, hockey sticks were securely mounted in the same jig but with the narrow side (the top face  110  in  FIG. 1 , which is about ¾″) positioned upward and weights were dropped on them half way between the mounting locations to achieve an impact force of 15 J. This experiment simulated a stick-on-stick impact occurring most likely on the narrow top face of the shaft, while breakage would most likely occur when shooting the puck on the wider front face, i.e., perpendicular to the initial impact. Five (5) specimens for each condition were tested. Table 1 indicates that the hockey sticks having the exemplary protective sheath retained a much greater percentage of the original load bearing capacity performance after impact. In addition, the shaft peak load after impact for the hockey stick having the exemplary protective sheath exceeded the performance of the bare hockey shafts before impact. Normalized for weight and length the shafts having the inventive protective sheath after impact had an average peak load value of 682N·cm/g versus 602N·cm/g for the bare shafts after impact. 
     The inventors have discovered that, in order for the protective sheath to provide a meaningful improvement, at least one polymeric layer and at least one metallic layer, specifically the strong metallic layer of limited ductility, need to be present. Furthermore, adding one or more metallic layers directly to the FRP substrate of the hockey stick does not provide a substantial performance benefit without the application of a polymeric layer in between the CFRP substrate and the strong metallic layer and therefore appears to add weight without appreciable performance benefits. Similarly, a sequence of, e.g., various layers of low ductility without the application of a subsequent ductile layer of at least 10 μm thickness in between appears to add weight without appreciable performance benefits. From the above the person skilled in the art will understand how to apply the guidance hereinbefore described to assemble a protective sheath according to the present invention meeting the desired performance benefits for specific applications. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Peak Load of various Hockey Sticks Before and After Impact. 
               
            
           
           
               
               
               
               
            
               
                   
                   
                 Peak Load 
                 Loss of 
               
               
                   
                 Peak Load 
                 after Impact 
                 Performance 
               
               
                 Hockey Stick ID 
                 New [N] 
                 [N] 
                 [%] 
               
               
                   
               
               
                 Bare Hockey Shaft 
                 1734 
                 1172 
                 32.4 
               
               
                 (prior art) 
               
               
                 Hockey Shaft with 
                 2056 
                 1767 
                 14.1 
               
               
                 4 Layer Protective 
               
               
                 Sheath (this invention) 
               
               
                   
               
            
           
         
       
     
     It is contemplated that each layer of high or low ductility can be formed so as to include two or more sub-layers, which can be formed of the same material or different materials within the thickness range provided. For certain implementations, at least one of the sub-layers can be formed of a conductive material, such as in the form of a coating of a metal, or a non-conductive material. 
     As illustrated, one preferred embodiment provides a protective sheath comprising a total of four layers, i.e., two sets of layers alternating between low ductility and high ductility. According to another embodiment of the invention a multi-layered design includes a first elastomeric layer, and a second high strength, metallic layer of low ductility that is adjacent to the first layer. According to another embodiment of the invention a multi-layered design includes a first elastomeric layer, and a low ductility metallic layer that is adjacent to the first layer, and a third layer that is adjacent to the second layer comprising a high ductility metallic layer. According to another embodiment of the invention a multi-layered design includes a first elastomeric layer, a second layer which is a metallic layer of low ductility that is adjacent to the first layer, a third layer which is a metallic layer of high ductility that is adjacent to the second layer, and a fourth layer which is a metallic layer of low ductility that is adjacent to the third layer. It is also contemplated that the protective sheath can include more or less layers for other implementations. 
     In another test new, partially coated hockey sticks (e.g., approximately 23″ from the heel  204  of the blade  200 , average total weight of 490 g) and new, uncoated hockey sticks (average total weight of 419 g) were subjected to three point bend tests over 1 m (40″) of the shafts, extending from the heels upwards. The shafts were designed to have the same flex and the test location was approximately 21″ from the heel. The load was applied to the front face  208  of the blade  200  of each of the hockey sticks. Table 2 indicates that the hockey sticks having the exemplary protective sheaths provided a 30% increase in load to failure and a 16.5% increase in deflection to failure. 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Peak Load of various Unused Hockey Sticks. 
               
            
           
           
               
               
               
               
               
            
               
                   
                   
                 Differ- 
                   
                 Differ- 
               
               
                   
                 Peak Load 
                 ence 
                 Deflection at 
                 ence 
               
               
                 Hockey Stick ID 
                 New [N] 
                 [%] 
                 Failure [mm] 
                 [%] 
               
               
                   
               
               
                 Bare Hockey Shaft 
                 1134.7 
                 — 
                 85.7 
                 — 
               
               
                 (prior art) 
               
               
                 Hockey Shaft with 
                 1476.7 
                 +30.1 
                 99.8 
                 +16.5 
               
               
                 4 Layer Protective 
               
               
                 Sheath (this invention) 
               
               
                   
               
            
           
         
       
     
     Determining the area under the stress-strain curves indicated that, at their respective failures, the inventive shafts stored 51% more energy than the uncoated shafts. 
     Similar results are obtained when the exemplary articles are lacrosse sticks, aerospace parts, and the like. 
     The foregoing description of the invention has been presented describing certain operable and preferred embodiments. It is not intended that the invention should be so limited since variations and modifications thereof will be obvious to those skilled in the art, all of which are within the spirit and scope of the invention.