WO1999020357A1

WO1999020357A1 - Sports implement with enhanced energy transfer, control of flexion and vibration dampening

Info

Publication number: WO1999020357A1
Application number: PCT/US1998/022303
Authority: WO
Inventors: Terry L. Schneider
Original assignee: Schneider Terry L
Priority date: 1997-10-20
Filing date: 1998-10-20
Publication date: 1999-04-29
Also published as: AU1272899A

Abstract

The invention provides sports implements with a shape memory alloy insert (35) located in a region of the implement that is subject to greatest force due to impact of the implement with a projectile. For composite structures, the shape memory alloy insert (35) is integrally formed into a shaft (22) of the sports implement (20), and is surrounded by composite plies (46, 48). In certain embodiments, more than one shape memory alloy insert (35, 55) may be used. When the shape memory alloy undergoes a stress-induced martensitic phase transformation, a significant portion of the generated energy is absorbed by the alloy and only a reduced amount is transmitted to a user.

Description

SPORTS IMPLEMENT WITH ENHANCED ENERGY TRANSFER, CONTROL OF FLEXION AND VIBRATION DAMPENING

Related Patent Applications This application seeks priority from U.S. Provisional Patent Application No. 60/062,584 filed October 20, 1997 and U.S. Provisional Patent Application No. 60/093,545 filed July 21, 1998.

Field of the Invention

The invention relates to the use of shape memory alloy reinforcement in load or impact-bearing elements of a shaft (and head, in some cases) of a sports implement, such as a golf club, hockey stick, polo club, baseball bat, tennis racquet and the like, to improve energy transfer and control of flexion, and to dampen impact-induced vibrations to impart a desired "feel" to the user.

Background of the Invention

In recent years, there has been a growing demand among consumers for opportunities to participate in a variety of sports, both as a means of recreation and to improve general health. At the same time, there have been several breakthroughs in technology, some of which have been applied to the implements used in sports. For example, while early golf clubs had shafts made of wood or wood composite, and club heads made of steel, these have been superseded by modern golf clubs with carbon-fiber reinforced shafts and titanium alloy heads. Moreover, sports implements have also been modified for form, to the extent that form dictates function and to the extent allowed by sports regulatory bodies.

Despite the significant advances in technology applied to sports implements, there yet exists a need for implements that are able to absorb forces generated by a club or racquet striking a ball at high velocity, to protect the user while also providing a pleasing "feel". In particular, for example, it is well-known that tennis players sometimes develop "tennis elbow" as a result of forces transmitted from the tennis racquet to the elbow, when the racquet strikes a ball with high impact. The challenge for technology is to reduce the amount of force transmitted to the user, while maintaining a sufficient "feel" so that the user is able to exercise control, obtain instantaneous feedback, and derive pleasure from playing the game. Moreover, the technology should be such that the implement, whether a golf club, hockey stick, tennis racquet, and the like, should be lightweight and retain its utility while at the same time having enhanced strength for longevity, energy transfer, user control, and reduced transmission of impact forces to the user.

Summary of the Invention The invention provides sports implements that improve impact resistance, improve energy transfer, enhance control of flexion, and improve vibration dampening by utilizing a strategically placed reinforcing insert or segment of shape memory alloy. When the implement strikes a projectile, such as a ball or hockey puck, impact energy is at least partially absorbed by the (austenitic) shape memory alloy undergoing martensitic transformation. Thus, not only is more energy transferred from the implement to the projectile, but vibration forces that ordinarily would travel to the limb of the user are reduced, reducing the risk of injury due to repetitive use. Moreover, while the shape memory alloy absorbs impact energy, sufficient energy is yet transmitted to impart a desired "feel" to the user, resulting in potentially better control and enhancing the pleasure of playing the game.

More particularly, the sports implements of the invention generally include a shaft with one end adapted for being grasped by the user, and a second end having a head with a striking surface for striking a projectile. In certain instances, such as, for instance, an ice hockey stick, the head may be an integral part of the lower end of the shaft. Likewise, the frame of the heads of racquets, such as tennis, racquetball, badminton, and squash racquets, may be integrally formed with the shaft. Notwithstanding, for implements with a composite shaft, the shaft includes at least one composite layer surrounding and forming a surface of the shaft in an area subject to impact energy forces when the sports implement strikes a projectile. A shape memory alloy insert, having a shape substantially conforming to that of the composite ply, extends adjacent and between the composite layers of the shaft. The shape memory alloy insert may comprise filaments or strips, a wire mesh screen, a thin sheet, or a perforated sheet, or an integral ring or band of the alloy.

In the case of metal shafted implements, the shape memory alloy may replace a portion of the shaft subject to flexion from impact forces, or the entire shaft (and head) may be of shape memory alloy.

The invention utilizes the unique property of shape memory alloys in that they undergo martensitic phase transformation, to absorb impact energy generated when the sports implement strikes a projectile. The invention is applicable to both composite and metallic sports instruments. Thus, the hybrid composite formed when at least one layer of shape memory alloy is utilized in conjunction with composite plies, generally made of fiber reinforcement within a resin matrix, provides unique benefits due to the unique properties added by the shape memory alloy. In metallic implements, the shape memory alloy replaces or reinforces the flex point area(s) of the implement to absorb impact-induced forces. The shape memory alloy (SMA) includes alloys with elements selected from the group comprising: Ni, Ag, Au, Cd, In, Ga, Mn, Cr, Co, C, N, Si, Ge, Sn, Sb, Zn, Nb, Cu, Fe, Pt, Al, and Ti. The shape memory alloy would preferably have superelastic (reversible strain) properties and preferably be able to exhibit stress- induced martensitic phase transformations. It is believed that the ability to transform from an austenitic to a martensitic phase will maximize the damping properties of the alloy. Alternatively, the shape memory alloy may be selected and subjected to a heat processing treatment such that it is in the martensitic phase at a desired range of temperatures, in which it is believed the shape memory alloy will be used. As a result, a device made of shape memory alloy exhibits superelastic properties when used in the selected range of temperatures, omitting the need to pre-stress the shape memory alloy elements.

Brief Description of the Drawings The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:

FIGURE 1A is a schematic diagram illustrating filaments or strips of shape memory alloy, that can be wound around or extend along a portion of a shaft (and head) of a sports implement in accordance with the invention; FIGURE IB is a schematic diagram illustrating filaments, of rectangular cross-section, of shape memory alloy useful in sports implements of the invention;

FIGURE 1C is a cross-section taken at 1C-1C of FIGURE 1A showing a hollow shape memory alloy filament; FIGURE 2 is an illustrative representation of a wire mesh screen fabricated from filaments of shape memory alloy, that may be used in certain embodiments of the invention as shape memory alloy inserts or layers;

FIGURE 3 is an illustrative representation of thin perforated sheet of shape memory alloy, that may be utilized in certain embodiments of the invention as a shape memory alloy insert or layer;

FIGURE 4A is a schematic side view in partial cross-section of a golf club, in accordance with the invention, using a shape memory alloy insert;

FIGURE 4B is another embodiment of a golf club in accordance with the invention, utilizing a shape memory alloy insert; FIGURE 4C is another embodiment of a metal golf club in accordance with the invention, utilizing a shape memory alloy applied to the exterior and interior surfaces of the golf club's hollow shaft;

FIGURE 4D is a cross-section taken at 4D-4D of FIGURE 4C, showing a shape memory alloy applied to the outer surface of the hollow shaft; FIGURE 4E is a cross-section taken at 4E-4E of FIGURE 4C, showing a shape memory alloy applied to the inner surface of the hollow shaft;

FIGURE 5 A is a schematic perspective view of an embodiment of a shaft of a sports implement in accordance with the invention illustrating layers of composite plies with an intervening shape memory alloy insert of longitudinally extending filaments or strips;

FIGURE 5B is a variant of the embodiment of FIGURE 5A, but with two shape memory alloy inserts;

FIGURE 6 is a schematic perspective view illustrating layers of composite plies and a layer of shape memory alloy insert comprised of shape memory alloy wire mesh screen, in accordance with the invention;

FIGURE 7 is a schematic perspective view illustrating another embodiment of a shaft of a sports implement in accordance with the invention, having composite plies and a shape memory alloy insert in the form of a perforated sheet;

FIGURE 8 is a side view, in partial cross-section, of a hockey stick showing the location of a shape memory alloy insert in accordance with the invention; and FIGURE 9 is a schematic illustration of a tennis racquet, including a shape memory alloy insert in accordance with the invention with location of the insert shown in broken lines.

FIGURE 10 is a baseball bat embodiment, not to scale, of the invention; FIGURE 10A is a cross-section taken at 10A-10A of FIGURE 10 showing a hollow portion of the baseball bat formed from a shape memory alloy;

FIGURE 1 OB is a cross-section taken at 10B-10B of FIGURE 10 showing a hollow portion of the baseball bat with a shape memory alloy applied to the outer surface of the baseball bat; FIGURE 11 is a metallic sectional shaft embodiment of the invention; and

FIGURE 11 A is a schematic cross-section taken at 11 A-l 1A of FIGURE 11 A showing an embodiment of a shape memory alloy insert in accordance with the invention.

Detailed Description of the Preferred Embodiment In the specification and claims, the term "frusto-conical" means a shape in the form of a portion of a cone, having a tip removed. While a cone is circular in cross- section, transverse to its vertical axis, it is recognized that some of the sports implement shafts to which the invention pertains are not of precisely circular cross- section. Accordingly, in the specification and claims, the term "frusto-conical" should be more broadly interpreted to include all those shafts that taper, and that have a cross-sectional area that approximates a circular shape, such as elliptical shapes, and the like. Other shafts, such as the shaft of an ice hockey stick, may not taper, and may have a cross-sectional area that more closely resembles a rectangle, with rounded ends. Shape memory alloys (SMAs) are a family of alloys having qualities of memory and trainability. A particularly useful attribute of an SMA is that when it is plastically deformed at a particular temperature, it can completely recover its original shape on being raised to a higher predefined temperature. In recovering its original shape, the SMA produces a powerful displacement force that can be 200 times greater than a force produced by the expansion and contraction of a bimetallic element of the same weight. Moreover, a particular SMA can be selected so that the return to the memory shape occurs at a predetermined desired temperature. To produce an SMA element that has a desired single memory shape, the SMA is formed into the desired shape and heated to a temperature so that the crystalline temperature of the SMA is entirely in a beta or austenite phase. The SMA element is then cooled below a defined and characteristic temperature M_t at which the austenite crystal structure of the alloy changes to a martensite crystal structure. The SMA element can then be plastically deformed into a different shape. If the SMA element is then heated above another defined temperature A_t (where A_t > M_j) at which the martensite crystalline structure of the alloy is again converted to the austenite crystalline structure, the SMA moves and exerts force as it reverts back into its memory shape. This process can be repeated indefinitely.

In 1962, an SMA of nickel and titanium (referred to as "nitinol") was discovered. Nitinol alloy is an SMA that can retain memory shapes for two different physical configurations of the alloy, at two different temperatures through a process of trainability. Trainability of the Nitinol alloy is based upon the fact that the alloy exhibits superelasticity, i.e., the growth and compensating contraction of adjacent plates of the martensite crystalline structure as stress is applied. The training of a Nitinol alloy (and other SMAs) for two different shape memory configurations is generally accomplished by limiting the number of variants of martensite formed when an alloy is repeatedly heated and cooled below the critical temperature M_t.

Shape memory and super elastic alloys undergo microstructural processes when subjected to mechanical forces that convert these forces into thermal energy in the material. These processes do not damage or work harden the alloy so that the alloys can be used as highly fatigue-resistant damping components in structures. It is useful to recall that there are both processed martensitic shape memory alloys, and stress-induced martensite alloys. The person of skill in the art will select between these shape memory alloys, as appropriate for the particular purpose. For example, shape memory alloy that transforms to stress-induced martensite could be used for the surface of a baseball bat that strikes the projectile, since a permanent deformation would not likely occur. In this instance, a shape memory alloy, originally in austenitic phase, should be selected that transforms to a processed martensitic phase, before reverting back to austenitic after impact force absorption.

The shape memory alloy (SMA) includes alloys with elements selected from the group comprising: Ni, Ag, Au, Cd, In, Ga, Mn, Cr, Co, C, N, Si, Ge, Sn, Sb, Zn, Nb, Cu, Fe, Pt, Al, and Ti. The shape memory alloy would preferably have superelastic (reversible strain) properties and preferably be able to exhibit stress- induced martensitic phase transformations. It is believed that the ability to transform from an austenitic to a martensitic phase will maximize the damping properties of the alloy. Alternatively, the shape memory alloy may be selected and subjected to a heat processing treatment such that it is in the martensitic phase at a desired range of temperatures, in which it is believed the shape memory alloy will be used. As a result, a device made of shape memory alloy exhibits superelastic properties when used in the selected range of temperatures, omitting the need to pre-stress the shape memory alloy elements.

The composite layers utilized in certain embodiments of the invention in conjunction with shape memory alloy reinforcing insert(s), may include any of the composites known in the art that are used for various purposes, including the fabrication of sports implement shafts. Such composites include a reinforcement embedded within or coated with an organic polymeric matrix. The reinforcement may include any one of several kinds of long strands of fiber, woven fiber, braided fiber, or other structure, made from a variety of known fibers, such as, for example, glass fiber, carbon fiber, ceramic fiber, metal fiber, organic polymeric ("plastic") fibers and the like. The matrix material acts as a binder and, while preferably a thermosetting resin, may also be a thermoplastic polymer, or a combination of the two. In certain embodiments, the shape memory alloy may be embedded in a metal matrix, such as for example, SMA filaments in a steel tubing material.

Shape memory alloys include commercially available NITINOL™, and it is known that they can be made from alloys that include a wide range of elements, for example, elements selected from the group consisting of: nickel, silver, gold, cadmium, indium, gallium, silicon, germanium, tin, zinc, niobium, copper, iron, platinum, aluminum, manganese, chrome, cesium, antimony, carbon (as carbide), nitrogen (as nitride), and titanium. Thus, a wide variety of shape memory alloys may be used, in accordance with the invention. The most preferred alloy is NITINOL™ (NiTi). The alloy thickness will vary depending upon the type of sports implement to which it is applied and the particular alloy used, but typical thickness of the alloy insert or reinforcement is in the range from about 5 microns to about 1.25 cm.

As will be explained in more detail below, with reference to the attached drawings with illustrative non-limiting examples of applications of the invention, sports implements are improved by the addition of a layer of shape memory alloy in a strategic region of the shaft, either in the form of solid and hollow filaments or strips, or woven and braided wire mesh, or thin perforated and non-perforated sheets, or a combination of these. The shape memory alloy inserts are preferably located at those regions of the sports implement shaft that are determined to be subject to the highest impact forces and/or flexion, to allow the shape memory alloy to "absorb" some of that energy through martensitic transformation, while at the same time transmitting sufficient force to allow the user feedback, a pleasant "feel" of striking the ball, and to permit the user to maintain control of the implement.

Thus, a composite-type sports implement may include a single shape memory alloy reinforcing insert, or several of these arranged in a concentric manner along the length of the shaft of the implement, either between layers of composite plies or at the outer surface of the implement. In the case of a sports implement like an ice hockey stick, wherein the club head bearing the striking face is integral with the shaft, the insert may have an "L-shape" to conform with the angle of the shaft to the head. In the case of a tennis racquet, a "Y"-shaped insert may be used. As explained above, several inserts may be used, and these are preferably concentrically arranged with intervening composite ply(s). Additionally, a sports implement may include at least one shape memory alloy insert arranged along the length of the shaft of the implement. The shape memory alloy inserts may be applied to the exterior surface of a sports implement shaft and/or an inner surface of a hollow shaft.

In certain instances, for example in the instance of golf clubs, the orientation of plies of composite material may already be well-established. Further advances in the arrangement and orientation of these plies may be expected, as technology advances. Modern computer modeling allows the prediction of performance of selected combinations of composite ply orientations. Accordingly, while the description herein illustrates certain particular orientations of the plies of composite fayers of the sports implement shaft, these are for exemplary purposes only, and do not limit the scope of the invention which more broadly relates to the inclusion of at least one layer (or insert) of a shape memory alloy adjacent to or between layers of composite plies, regardless of ply orientation or type.

The attached figures illustrate preferred embodiments of the invention, and do not limit the invention as described during and claimed here below.

FIGURES 1A and IB are schematic illustrations of filaments 2, 4 of shape memory alloy. These filaments may extend along a length of a shaft in the required high impact force region or may be wound around that region of the shaft, in accordance with the invention. The filaments may be wound over a prior layer of composite, and covered by a subsequent layer of composite. FIGURE 1C shows a cross-section of a hollow shape memory alloy circular filament 2'. Solid and hollow filaments may be circular 2 or square 4 or any other geometric shape in cross-section. FIGURE 2 is a schematic illustration of a wire mesh screen construct 6, wherein the filaments 2 of the screen comprise a shape memory alloy. The screens may be used in place of the filaments, as discussed above, to produce a shape memory alloy insert at a strategic location of the sports implement where impact forces are highest, when the implement strikes a projectile.

FIGURE 3 is a schematic illustration of a thin perforated sheet 8 of shape memory alloy, the perforations serving to reduce the overall mass of the insert prepared from the sheet. As described above, the sheet may substitute for the filaments or mesh to form a shape memory alloy insert. Additionally, it is envisioned that the filaments, wire mesh screen, and thin perforated sheet may also be the outermost ply in a composite shaft.

FIGURE 4A shows a golf club 20 having a shaft 22 with a proximal end 24 for grasping by the user, and a distal end 26 to which a club head 30 is mounted. The hosel 26 of the club is a flex point area of high-impact forces 32, and is located at the point of insertion of the shaft 22 into a bore in the club head 30. As shown in the partially cross-sectioned region of the shaft of the embodiment of FIGURE 4A, the shape memory alloy insert 35 extends along the shaft 22 both above and below the hosel 32, thereby reinforcing and covering the strategic flex point and area of greatest impact force of the golf club 20. The shaft 22 may also include a second insert 55 at a flexion point, and a third insert 65 to absorb vibration at the proximal end 24 of the shaft 22 adapted for grasping.

In the embodiment of FIGURE 4B, the shape of the golf club head is different than that of FIGURE 4A, and includes a hosel 26 that extends upward in a substantially semi-cylindrical form from the club head 30. The tip end 28 of the shaft 22 is mounted in a bore in the hosel 26, which does not extend to the base of the club head 30 as in FIGURE 4 A. Again, the shape memory alloy insert 35 extends both above and below the hosel 26, covering the area of maximum impact forces 32 on the shaft 22.

In the embodiment of FIGURE 4C, the golf club has a hollow steel shaft and includes a hosel 26' that extends upward in a substantially semi-cylindrical form from a club head 30'. A tip end 28' of a shaft 22' is mounted in a bore in the hosel, which does extend to the base of club head 30'. A shape memory insert 65' extends both above and below the hosel 26', covering the area of maximum impact forces 32' on the shaft 22. FIGURE 4D is a cross-section taken at a proximal end 24' of shaft 22' showing the shape memory alloy insert 65' applied to an outer surface 62 of the shaft. Although not shown, it is envisioned that the proximal end 24' of the shaft 22' may be solid. Also, FIGURE 4E is a cross-section taken at the middle portion of shaft 22' showing a shape memory alloy insert 64 applied to the inner surface of the shaft.

FIGURE 5 A is an embodiment of the flex point region of high flexural stress of the shafts of FIGURES 4A and 4B, showing the structural composite plies and the shape memory alloy insert. The shaft 22 is of substantially frusto-conical shape, tapering from a largest cross-sectional area in the vicinity of the proximal end 24 to a smallest cross-sectional area nearest the distal end 28. The first layer 40 of the composite shaft illustrated is a composite ply with fibers at an angle of about 45° to the axis of the shaft. The second ply 42 is wound with fibers at an angle of -45° to the shaft. The third ply 44 is wound at an angle of about 60° to the shaft, and the fourth ply 46 at angle of -60° to the shaft. After the fourth ply, there is a shape memory alloy insert 35, illustrated as filaments 2 of shape memory alloy aligned along the axis of the shaft. In other embodiments, the filaments may be wound around the shaft, at angles of 45°, 60°, or any other selected angle. In the embodiment of FIGURE 5 A, the shape memory alloy insert 35 is covered with a pair of outer structural composite plies 48, 50 each also having fibers aligned along the central axis of the shaft.

FIGURE 5B shows a second embodiment of a flex point region of a shaft that includes a second shape memory alloy insert 55, concentric with the first insert 35. The second insert 55 is spaced from the first one by at least one intervening layer of composite plys 48, and is covered by at least one protective composite ply layer 50. Alternatively, the alloy layer 55 may be the outermost layer.

Referring to FIGURE 6, this illustrates yet a further embodiment of the flex point region of a shaft of a sports implement of the invention wherein the shape memory alloy insert 35 is a wire mesh screen, rather than filaments or strips of shape memory alloy. FIGURE 7, yet another embodiment, shows a shape memory alloy insert 35 of a perforated sheet of shape memory alloy. As in the case of FIGURE 5B, more than one mesh screen or a perforated sheet may be used to form concentric shape memory alloy inserts. Moreover, mixtures of inserts may be used: for example, a first insert of shape memory alloy filament coupled with a second insert of either shape memory alloy perforated sheet or shape memory alloy mesh screen. Other permutations are clearly also possible.

FIGURE 8 is an illustration of a hockey stick 60, showing the location of a shape memory alloy insert 35 in dotted lines. The shape memory alloy is also sandwiched between composite plies, as discussed above, but the insert is "L"-shaped, to cover the area of the stick that is subject to greatest impact forces. Although not shown, the shape memory alloy inserts may be applied to the outer surface of the hockey stick in substantially the same locations as indicated by the dotted lines.

FIGURE 9 shows a shape memory alloy insert 35, in dotted lines, in a tennis racquet 70. The shape memory alloy is substantially "Y"-shaped, with the lower leg 33 of the Y extending along the shaft, and each branch 37 of the Y extending into the frame of the racquet that surrounds the head 72. Similar construction may clearly be used for racquetball racquets, badminton racquets, and squash racquets. Further, the "string" 38 of the racquet may also be fabricated of shape memory alloy filaments or composite filaments reinforced with such alloys, or filaments that have sections made of such alloys. It is also envisioned that the shape memory alloy insert may be applied to the outer surface of the tennis racquet in substantially the same location as indicated by the dotted lines.

FIGURES 10 and 10A show a baseball bat 80 having a series of shape memory alloy sections. The shape memory alloy 84 is located at the hand grip, to reduce vibration imparted to the user. Another shape memory alloy insert 82 is located at a point of flexion, to absorb forces. Finally, a striking face 88 of the bat 80 is also fabricated of shape memory alloy. In this instance, the baseball bat 80 may be formed, as conventionally, of a hollow, substantially tubular material, but with shape memory alloy substituting for the standard aluminum metal in the regions shown. As an alternative, the entire baseball bat 80 may be fabricated of a shape memory alloy. FIGURE 10B is a cross-section of the baseball bat 80 showing a hollow portion of the distal end with a shape memory alloy insert 88' applied to an outer surface 81. It is also envisioned that the baseball bat 80 may be formed from a solid non-metallic material including wood and a composite material, and the shape memory alloy insert 88' could be applied to the outer surface of the non-metallic material.

Referring to FIGURES 11 and 11 A, illustrating a metallic golf club shaft in cross-section, the shaft is fabricated from a series of cylindrical sections 22a, and has a shape a shape memory alloy portion 35 at its distal end 26, and a second shape memory alloy portion 55 at its proximal end 24. These shape memory alloy portions substitute for the standard steel sections 22a that would be used in the prior art. As shown in FIGURE 11 A, in one embodiment, the shape memory alloy 35 (and 55) may be made up of a cylindrical ring of metal 56 that includes a series of longitudinal circumferentially spaced shape memory alloy filaments 2. Alternatively, the entire cylindrical ring 35 may be fabricated of the shape memory alloy. It is also envisioned that any of the standard metallic sections may be replaced with a shape memory alloy section.

While the preferred embodiment of the invention has been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the invention.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A sports implement having improved impact resistance, vibration dampening, and a defined flex point location the sports implement comprising a shaft having a first end adapted for being grasped by a human hand, and a second end proximate a head of the implement for striking a projectile, the shaft of layered construction and comprising:

(a) at least one composite layer, the layer extending along a portion of the shaft subject to vibrational forces when the sports implement strikes a projectile; and

(b) a layer comprising shape memory alloy forming a reinforcing insert at the flex point, the insert extending along a portion of the shaft adjacent to a portion of the at least one composite layer, the shape memory alloy having super- elastic properties and undergoing martensitic phase transformation to absorb forces generated when the implement strikes a projectile.

2. The sports implement of Claim 1, wherein the sports implement is selected from the group consisting of golf clubs, baseball bats, polo clubs, tennis racquets, squash racquets, racquetball racquets, and ice hockey sticks.

3. The sports implement of Claim 1, wherein the shape memory alloy insert comprises aligned individual lengths of shape memory alloy filaments, the shape memory filaments including a hollow and a solid shape.

4. The sports implement of Claim 1, wherein the shape memory alloy insert comprises a woven wire mesh screen of shape memory alloy filaments.

5. The sports implement of Claim 1, wherein the shape alloy memory insert comprises a sheet of shape memory alloy composition, the sheet including a perforated and a solid shape.

6. The sports implement of Claim 1, wherein the sports implement is an ice hockey stick, and the shape memory alloy insert is L-shaped and extends from a distal end of the shaft into the head, the head supporting a striking face of the hockey stick.

7. The sports implement of Claim 1, wherein the shape memory alloy insert is frusto-conical in shape.

8. The sports implement of Claim 1, wherein the sports implement is a racquet and the shape memory alloy is Y-shaped with a leg of the "Y" extending along the second end of the shaft and one branch of the " Y" extending from either side of the second end of the shaft into a rim surrounding a head of the implement.

9. The device according to Claim 1, wherein the shape memory alloy insert is pre-stressed at a level sufficient to be near the threshold of the pseudo-elastic plateau region of the alloy's stress-strain property curve.

10. The device according to Claim 1, wherein the shape memory alloy insert is selected so as to be in a martensitic phase at a temperature at which the device is used.

11. A sports implement comprising a shaft having a first end adapted for being grasped by a human hand, and a second end adapted for mounting a club head thereto, the shaft of layered hybrid composite construction and the shaft comprising:

(a) a series of concentric composite layers extending along a length of the shaft, to form the shaft; and

(b) an intervening layer, adjacent a composite layers, of a shape memory alloy insert, the insert located at a region of the shaft subject to high-impact forces when the head of the sports implement strikes a projectile.

12. The sports implement of Claim 11 wherein the shaft is of substantially circular cross-section, and the shape memory alloy is of frusto-conical shape.

13. The sports implement of Claim 11, wherein the implement is a golf club and the shape memory alloy insert is located in a flex point region proximate the hosel of the golf club.

14. The sports implement of Claim 11, wherein the shaft comprises a second shape memory alloy insert, the insert spaced from the first insert by at least one intervening composite ply layer.

15. The sports implement of Claim 11, wherein the shape memory alloy insert is comprised of shape memory alloy in the form of at least one selected from the group consisting of solid and hollow filaments, woven and braided meshes, sheets, and perforated sheets of shape memory alloy.

16. The device according to Claim 11, wherein the shape memory alloy insert is pre-stressed at a level sufficient to be near the threshold of the pseudo-elastic plateau region of the alloy's stress-strain property curve.

17. The device according to Claim 11, wherein the shape memory alloy is selected so as to be in a martensitic phase at a temperature at which the device is used.

18. A sports implement comprising a shaft having a first end adapted for being grasped by a human hand, and a second end having a head for striking a projectile, wherein a portion of the head is integrally formed with the shaft, the shaft and integrally formed portion of the head being of layered hybrid composite construction and comprising:

(a) composite layers extending along the shaft and the integral portion of the head; and

(b) a shape memory alloy insert forming a layer adjacent a composite ply, the shape memory alloy layer extending along at least a portion of the second end of the shaft and a contiguous portion of the head in a region of the sports implement subject to forces when the sports implement strikes a projectile.

19. The sports implement of Claim 18, wherein the sports implement is selected from the group consisting of tennis racquets, squash racquets, racquetball racquets, baseball bats and hockey sticks.

20. The sports implement of Claim 18, wherein the shape memory alloy insert is selected from inserts formed of woven and braided wire mesh, solid and hollow filaments, sheets, and perforated sheets of shape memory alloy.

21. The sports implement of Claim 18, wherein the shape memory alloy insert is "Y"-shaped with a leg of the "Y" extending along the portion of the shaft.

22. The device according to Claim 18, wherein the shape memory alloy insert is pre-stressed at a level sufficient to be near the threshold of the pseudo-elastic plateau region of the alloy's stress-strain property curve.

23. The device according to Claim 18, wherein the shape memory alloy insert is selected so as to be in a martensitic phase at a temperature at which the device is used.

24. A sports implement comprising a metallic shaft having a first end adapted for being grasped by a human hand, and a second end adapted for mounting a club head thereto, the shaft comprising an elongate hollow metallic body, wherein a portion of the body of the shaft subject to flexion when the implement impacts a projectile is comprised of shape memory alloy.

25. The sports implement of Claim 24, wherein the shaft is a golf club shaft, and the shape memory alloy is located at the distal end of the golf club shaft.

26. The sports implement of Claim 24, wherein the shaft is a golf club shaft and the proximal end of the shaft comprises shape memory alloy.

27. The device according to Claim 24, wherein the shape memory alloy is pre-stressed at a level sufficient to be near the threshold of the pseudo-elastic plateau region of the alloy's stress-strain property curve.

28. The device according to Claim 24, wherein the shape memory alloy is selected so as to be in a martensitic phase at a temperature at which the device is used.

29. A metallic baseball bat, the baseball bat having a hollow interior portion, surrounded by a metallic skin, a portion of the metallic skin comprised of a shape memory alloy, at a location subject to forces when the baseball bat strikes a projectile.

30. The baseball bat of Claim 29, wherein the portion of the baseball bat comprised of shape memory alloy is the striking face of the bat.

31. The baseball bat of Claim 29, wherein the portion of the baseball bat comprised of shape memory alloy is located in a neck region of the baseball bat.

32. The baseball bat of Claim 29, wherein the portion of the bat comprised of shape memory alloy is at a proximal end of the bat adapted for being grasped by a human hand.

33. The device according to Claim 29, wherein the shape memory alloy is pre-stressed at a level sufficient to be near the threshold of the pseudo-elastic plateau region of the alloy's stress-strain property curve.

34. The device according to Claim 29, wherein the shape memory alloy is selected so as to be in a martensitic phase at a temperature at which the device is used.