Methods for fabricating composite face plates for use in golf clubs and club-heads for same

Abstract

Methods are disclosed for making composite face plates for club-heads of golf clubs. In an exemplary method a lay-up is formed having multiple prepreg layers, each including at least one layer of respective fibers at a respective orientation. The at least one fiber layer is impregnated with a resin. The lay-up is exposed to an initial tool temperature T.sub.i and an initial pressure P.sub.1. At time t.sub.1 the resin has minimal viscosity, and the lay-up temperature and pressure are increased from T.sub.i and P.sub.i, respectively. During an interval from time t.sub.1 to time t.sub.2, the lay-up temperature and pressure are increased to T.sub.s>T.sub.i and P.sub.2>P.sub.1, respectively. During the first interval the resin experiences a relatively rapid progressive increase in viscosity. During a second interval between t.sub.2 and a later time t.sub.3, the lay-up is maintained substantially at T.sub.s and substantially at P.sub.2, which allows the resin to experience a relatively slow progressive increase in viscosity to a specified pre-cure viscosity level.

Description

CROSS REFERENCE TO RELATED APPLICATION

[0001] This application claim priority to, and the benefit of, U.S. Provisional Application No. 60/877,336, filed on Dec. 26, 2006, which is incorporated herein by reference in its entirety.

FIELD

[0002] This disclosure pertains generally to golf clubs and club-heads. More particularly the disclosure pertains to, inter alia, wood-type club-heads and other types of club-heads that have a face insert or the like.

BACKGROUND

[0003] With the ever-increasing popularity and competitiveness of golf, substantial effort and resources are currently being expended to improve golf clubs so that increasingly more golfers can have more enjoyment and more success at playing the game. Much of this improvement activity has been in the realms of sophisticated materials and club-head engineering. For example, modern "wood-type" golf clubs (notably, "drivers" and "utility clubs"), with their sophisticated shafts and non-wooden club-heads, bear little resemblance to the "wood" drivers, low-loft long-irons, and higher numbered fairway woods used years ago. These modern wood-type clubs are generally called "metal-woods."

[0004] An exemplary metal-wood golf club such as a fairway wood or driver typically includes a hollow shaft having a lower end to which the club-head is attached. Most modern versions of these club-heads are made, at least in part, of a light-weight but strong metal such as titanium alloy. The club-head comprises a body to which a strike plate (also called a face plate) is attached or integrally formed. The strike plate defines a front surface or strike face that actually contacts the golf ball.

[0005] The current ability to fashion metal-wood club-heads of strong, light-weight metals and other materials has allowed the club-heads to be made hollow. Use of light-weight materials has also allowed club-head walls to be made thinner, which has allowed increases in club-head size, compared to earlier club-heads. Larger club-heads tend to provide a larger "sweet spot" on the strike plate and to have higher club-head inertia, thereby making the club-heads more "forgiving" than smaller club-heads. (The current rules of the United States Golf Association, or USGA, specify a maximum limit to the volume of club-heads.) Characteristics such as size of the sweet spot are determined by many variables including the shape profile, size, and thickness of the strike plate as well as the location of the center of gravity (CG) of the club-head.

[0006] The distribution of mass around the club-head typically is quantified by parameters such as rotational moment of inertia (MOI) and CG location. Club-heads typically have multiple rotational MOIs, each associated with a respective Cartesian reference axis (x, y, z) of the club-head. A rotational MOI is a measure of the club-head'head's resistance to angular acceleration (twisting or rotation) about the respective reference axis. The rotational MOIs are related to, inter alia, the distribution of mass in the club-head with respect to the respective reference axes. Each of the rotational MOIs desirably is maximized as much as practicable to provide the club-head with more forgiveness.

[0007] Another factor in modern club-head design is the face plate. Impact of the face plate with the golf ball produces an instantaneous rearward deflection of the face plate. This deflection and the subsequent recoil of the face plate are expressed as the club-head'head's coefficient of restitution (COR). A thinner face plate deflects more at impact with a golf ball and potentially can impart more energy and thus a higher rebound velocity to the struck ball than a thicker or more rigid face plate. Because of the importance of this effect, the COR of clubs is limited under USGA rules.

[0008] Regarding the total mass of the club-head as the club-head's mass budget, at least some of the mass budget must be dedicated to providing adequate strength and structural support for the club-head. This is termed "structural" mass. Any mass remaining in the budget is called "discretionary" or "performance" mass, which can be distributed within the club-head to address performance issues, for example.

[0009] Some current approaches to reducing structural mass of a club-head are directed to making at least a portion of the club-head of an alternative material. Whereas the bodies and face plates of most current metal-woods are made of titanium alloy, several "hybrid" club-heads are available that are made, at least in part, of components formed from both graphite-composite (or another suitable composite material) and a metal alloy. For example, in one group of these hybrid club-heads a portion of the body is made of carbon-fiber (graphite) composite and a titanium alloy is used as the primary face-plate material. Other club-heads are made entirely of one or more composite materials. Graphite composites have a density of approximately 1.5 g/cm.sup.3, compared to titanium alloy which has a density of 4.5 g/cm.sup.3, which offers tantalizing prospects of providing more discretionary mass in the club-head.

[0010] Composites that are useful for making club-head components comprise a fiber portion and a resin portion. In general the resin portion serves as a "matrix" in which the fibers are embedded in a defined manner. In a composite for club-heads, the fiber portion is configured as multiple fibrous layers or plies that are impregnated with the resin component. The fibers in each layer have a respective orientation, which is typically different from one layer to the next and precisely controlled. The usual number of layers is substantial, e.g., fifty or more. During fabrication of the composite material, the layers (each comprising respectively oriented fibers impregnated in uncured or partially cured resin; each such layer being called a "prepreg" layer) are placed superposedly in a "lay-up" manner. After forming the prepreg lay-up, the resin is cured to a rigid condition.

[0011] Conventional processes by which fiber-resin composites are fabricated into club-head components utilize high (and sometimes constant) pressure and temperature to cure the resin portion in a minimal period of time. The processes desirably yield components that are, or nearly are, "net-shape," by which is meant that the components as formed have their desired final configurations and dimensions. Making a component at or near net-shape tends to reduce cycle time for making the components and to reduce finishing costs. Unfortunately, at least three main defects are associated with components made in this conventional fashion: (a) the components exhibit a high incidence of composite porosity; (b) a relatively high loss of resin occurs during fabrication of the components; and (c) the fiber layers tend to have "wavy" fibers instead of straight fibers. Whereas some of these defects may not cause significant adverse effects on the service performance of the components when the components are subjected to simple (and static) tension, compression, and/or bending, component performance typically will be drastically reduced whenever these components are subjected to complex loads, such as dynamic and repetitive loads (i.e., repetitive impact and consequent fatigue).

[0012] In view of the above, a need exists for improved methods for fabricating club-heads, the methods providing improved control of porosity, reductions in resin loss, and prevention of wavy fibers in composite components used for fabricating club-heads.

SUMMARY

[0013] The need stated above is met by methods and other aspects of the current invention, as disclosed herein.

[0014] An embodiment of such a method is directed to the fabrication of composite face plates for club-heads of golf clubs. The method comprises forming a lay-up that comprises multiple prepreg layers. Each prepreg layer comprises at least one layer of respective fibers at a respective orientation, and the at least one fiber layer is impregnated with a resin. The lay-up is exposed to an initial tool temperature T.sub.i and an initial pressure P.sub.1. Beginning at a time t.sub.1 at which the resin exhibits a minimal liquid viscosity, the temperature of the lay-up is increased from T.sub.i, and the pressure of the lay-up is increased from P.sub.1. During a first interval between the time t.sub.1 and a later time t.sub.2, the temperature of the lay-up to is increased to T.sub.s>T.sub.i, and the pressure of the lay-up is increased to P.sub.2>P.sub.1. During this first interval the resin exhibits a relatively rapid progressive increase in viscosity. During a second interval between the time t.sub.2 and a later time t.sub.3, the lay-up is maintained substantially at the temperature T.sub.s and substantially at the pressure P.sub.2, which allows the resin to undergo a relatively slow but continued increase in viscosity to a specified pre-cure viscosity level.

[0015] Desirably, the increase in temperature of the lay-up from T.sub.i is ramped, and the increase in pressure of the lay-up from P.sub.1 is ramped. Also or alternatively, during the first interval between the times t.sub.1 and t.sub.2, the temperature of the lay-up desirably is ramped up to T.sub.s, and the pressure of the lay-up desirably is ramped up to P.sub.2.

[0016] After the time t.sub.3, the temperature desirably is decreased from T.sub.s, and the pressure desirably is decreased from P.sub.2, and a full-cure of the lay-up can be completed. A full-cure generally is characterized by the resin exhibiting a maximal viscosity. The method can further comprise shaping the lay-up (full-cured or not) to have specified dimensions and shape for use as a face plate for a club-head.

[0017] In some embodiments the lay-up is formed in a tool configured to hold the lay-up as the lay-up is being exposed to the temperatures T.sub.i and T.sub.s and to the pressures P.sub.1 and P.sub.2. The lay-up can be removed from the tool when the lay-up has reached the specified pre-cure viscosity level. While the lay-up is in the tool, the contour of the lay-up can be shaped.

[0018] In some embodiments the pressure P.sub.1 is within a range 0-100 psig. This range can be 0-100 psig.+-..DELTA.P, wherein .DELTA.P is a maximum of 50 psi.

[0019] In some embodiments the pressure P.sub.2 is within a range 200-500 psig. This range can be 200-500 psig.+-..DELTA.P, wherein .DELTA.P is a maximum of 50 psi.

[0020] In some embodiments the temperature T.sub.s=T.sub.r.+-..DELTA.T, wherein T.sub.r is a manufacturer's recommended cure temperature for the resin, and .DELTA.T is a maximum of 75.degree. F. The temperature T.sub.i can be equal to T.sub.s/2.+-..DELTA.T.

[0021] At the time t.sub.1, the minimum viscosity of the resin can be in a range of .+-..DELTA.x, wherein .DELTA.x is a maximum of 25%. The time t.sub.1 can be in a range of .+-..DELTA.t, and .DELTA.t is a maximum of 10 minutes.

[0022] In some embodiments, at the time t.sub.2, the resin has reached 80% of its maximum viscosity X.sub.m, X.sub.m is in a range of .+-..DELTA.x, and .DELTA.x is a maximum of 25%.

[0023] In some embodiments the time t.sub.2 is in a range of .+-..DELTA.t, wherein .DELTA.t is a maximum of 10 minutes.

[0024] In some embodiments, at the time t.sub.3, the resin has reached 90% of its maximum viscosity X.sub.m, X.sub.m is in a range of .+-..DELTA.x, and .DELTA.x is a maximum of 25%. The time t.sub.3 can be in a range of .+-..DELTA.t, wherein .DELTA.t is a maximum of 10 minutes.

[0025] In some embodiments the pressure P.sub.1 is within the range 0-100 psig.+-..DELTA.P, wherein .DELTA.P is a maximum of 50 psi. The pressure P.sub.2 can be within a range 200-500 psig.+-..DELTA.P, wherein .DELTA.P is a maximum of 50 psi. The temperature T.sub.s can be equal to T.sub.r.+-..DELTA.T, wherein T.sub.r is a manufacturer's recommended cure temperature for the resin, and .DELTA.T is a maximum of 75.degree. F. The temperature T.sub.i can be equal to T.sub.s/2.+-..DELTA.T. At the time t.sub.1 the minimum viscosity of the resin can be in a range of .+-..DELTA.x, wherein .DELTA.x is a maximum of 25%, the time t.sub.1 is in a range of .+-..DELTA.t, and .DELTA.t is a maximum of 10 minutes. At the time t.sub.2 the resin can have reached 80% of its maximum viscosity X.sub.m, wherein X.sub.m is in the range of .+-..DELTA.x, and the time t.sub.2 is in the range of .+-..DELTA.t. At the time t.sub.3 the resin can have reached 90% of its maximum viscosity X.sub.m, wherein X.sub.m is in the range of .+-..DELTA.x, and the time t.sub.3 is in the range of .+-..DELTA.t.

[0026] In some embodiments the pressure is increased (desirably ramped) from P.sub.1 to P.sub.2 at a rate in which the pressure P.sub.2 is reached before the resin viscosity ceases its relatively rapid increase.

[0027] In many embodiments the prepreg layers comprise carbon fiber and epoxy resin.

[0028] The foregoing and additional features and advantages of the invention will be more readily apparent from the following detailed description, which proceeds with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] FIG. 1 is a perspective view of a "metal-wood" club-head, showing certain general features pertinent to the instant disclosure.

[0030] FIG. 2 is a schematic diagram showing an exemplary manner in which plies can be stacked in making a composite face plate.

[0031] FIGS. 3(A)-3(C) are plots of temperature, viscosity, and pressure, respectively, versus time in a representative embodiment of a process for forming composite components.

[0032] FIGS. 4(A)-4(C) are plots of temperature, viscosity, and pressure, respectively, versus time in a representative embodiment of a process in which each of these variables can be within a specified respective range (hatched areas).

[0033] FIG. 5 is a partial sectional view of the upper lip region of an embodiment of a club-head of which the face plate comprises a composite plate and a metal cap.

DETAILED DESCRIPTION

[0034] This disclosure is set forth in the context of representative embodiments that are not intended to be limiting in any way.

[0035] In the following description, certain terms may be used such as "up," "down,", "upper," "lower," "horizontal," "vertical," "left," "right," and the like. These terms are used, where applicable, to provide some clarity of description when dealing with relative relationships. But, these terms are not intended to imply absolute relationships, positions, and/or orientations. For example, with respect to an object, an "upper" surface can become a "lower" surface simply by turning the object over. Nevertheless, it is still the same object.

[0036] The main features of an exemplary hollow "metal-wood" club-head 10 are depicted in FIG. 1. The club-head 10 comprises a face plate 12 and a body 14. The face plate 12 typically is convex, and has an external ("striking") surface (face) 13. The body 14 defines a front opening 16. A face support 18 is disposed about the front opening 16 for positioning and holding the face plate 12 to the body 14. The body 14 also has a heel 20, a toe 22, a sole 24, a top or crown 26, and a hosel 28. Around the front opening 16 is a "transition zone" 15 that extends along the respective forward edges of the heel 20, the toe 22, the sole 24, and the crown 26. The transition zone 15 effectively is a transition from the body 14 to the face plate 12. The hosel 28 defines an opening 30 that receives a distal end of a shaft (not shown). The opening 16 receives the face plate 12, which rests upon and is bonded to the face support 18 and transition zone 15, thereby enclosing the front opening 16. The transition zone 15 includes a sole-lip region 18d, a crown-lip region 18a, a heel-lip region 18c, and a toe-lip region 18b. These portions can be contiguous, as shown, or can be discontinuous, with spaces between them.

[0037] In a club-head according to one embodiment, at least a portion of the face plate 12 is made of a composite including multiple plies or layers of a fibrous material (e.g., graphite, or carbon, fiber) embedded in a cured resin (e.g., epoxy). An exemplary thickness range of the composite is 4.5 mm or less. The composite is configured to have a relatively consistent distribution of reinforcement fibers across a cross-section of its thickness to facilitate efficient distribution of impact forces and overall durability.

[0038] The composite portion is made as a lay-up of multiple prepreg plies. For the plies the fiber reinforcement and resin are selected in view of the club-head's desired durability and overall performance. In tests involving certain club-head configurations, it was determined that composite portions formed of prepreg plies having a relatively low fiber areal weight (FAW) can provide superior attributes in several areas, such as impact resistance, durability, and overall club performance. (FAW is the weight of the fiber portion of a given quantity of prepreg, in units of g/m.sup.2.) FAW values below 100 g/m.sup.2, and more desirably below 70 g/m.sup.2, can be particularly effective. A particularly suitable fibrous material for use in making prepreg plies is carbon fiber, as noted. However, more than one fibrous material can be used.

[0039] Multiple low-FAW prepreg plies can be stacked and still have a relatively uniform distribution of fiber across the thickness of the stacked plies. In contrast, at comparable resin-content (R/C, in units of percent) levels, stacked plies of prepreg materials having a higher FAW tend to have more significant resin-rich regions, particularly at the interfaces of adjacent plies, than stacked plies of low-FAW materials. Resin-rich regions tend to reduce the efficacy of the fiber reinforcement, particularly since the force resulting from golf-ball impact is generally transverse to the orientation of the fibers of the fiber reinforcement.

[0040] In a composite face plate each low-FAW prepreg ply desirably has a prescribed fiber orientation, and the plies are stacked in a prescribed order with respect to fiber orientation. For convenience of reference, the fiber orientation of each ply is measured from a horizontal axis of the club-head's face plane to a line that is substantially parallel with the fibers in the ply. Referring to FIG. 2, for example, fiber orientation is indicated by dashed lines. To fabricate a composite face plate used in this example, a first low-FAW ply 120 is oriented at 0 degrees, followed by multiple unit-groups 122, 124, 126 of low-FAW plies each having four plies oriented at 0, +45, 90, and -45 degrees, respectively. The resulting stack of unit-groups of low-FAW plies is sandwiched between an "outer" ply 128 and an "inner" ply 130. The outer ply 128 is oriented at 90 degrees, and the inner ply 130 is oriented at 0 degrees. In this embodiment, the inner and outer plies 128, 130 are formed of prepreg reinforced by glass fibers, such as 1080 glass fibers. The other plies are formed of prepreg reinforced by carbon fiber. The number of unit groups desirably ranges from ten to fourteen, with twelve unit groups providing 48 plies being a preferred embodiment.

[0041] An example carbon fiber is "34-700" carbon fiber, available from Grafil (Sacramento, Calif.), having a tensile modulus of 234 Gpa (34 Msi) and a tensile strength of 4500 Mpa (650 Ksi). Another Grafil fiber that can be used is "TR50S" carbon fiber, which has a tensile modulus of 240 Gpa (35 Msi) and a tensile strength of 4900 Mpa (710 Ksi). Suitable epoxy resins are types "301" and "350" available from Newport Adhesives and Composites (Irvine, Calif.). An exemplary resin content (R/C) is 40%.

[0042] In the general procedure described above, stacking the prepreg plies in predetermined orientations may be done by first stacking individual plies in unit-groups 122, 124, 126, and then stacking a desired number of unit-groups (and any additional desired plies) to form the final thickness of the composite. The inner ply 128 and outer ply 130 desirably are made of a different fiber material than used in the plies of the unit-groups. The number of unit-groups can be varied as desired. One embodiment comprises twelve unit-groups.

[0043] The following aspects desirably are controlled to provide composite components that are capable of withstanding impacts and fatigue loadings normally encountered by a club-head, especially by the face plate of the club-head. These three aspects are: (a) adequate resin content; (b) fiber straightness; and (c) very low porosity in the finished composite. These aspects can be controlled by controlling the flow of resin during curing, particularly in a manner that minimizes entrapment of air in and between the prepreg layers. Air entrapment is difficult to avoid during laying up of prepreg layers. However, air entrapment can be substantially minimized by, according to various embodiments disclosed herein, imparting a slow, steady flow of resin for a defined length of time during the laying-up to purge away at least most of the air that otherwise would become occluded in the lay-up. The resin flow should be sufficiently slow and steady to retain an adequate amount of resin in each layer for adequate inter-layer bonding while preserving the respective orientations of the fibers (at different respective angles) in the layers. Slow and steady resin flow also allows the fibers in each ply to remain straight at their respective orientations, thereby preventing the "wavy fiber" phenomenon. Generally, a wavy fiber has an orientation that varies significantly from its naturally projected direction.

[0044] Even with achievement of slow and steady resin flow, air bubbles and air pockets still tend to remain at the edges (or nearly at the edges) of the composite component as formed during laying-up. The presence of this residual air at or near the edges is especially likely if the bubbles and pockets did not have time to travel completely to the surfaces (including edge surfaces) of the lay-up during the slow-and-steady period of resin flow. The edges are also where wavy fibers are likely to be formed. Hence, it is important that components intended for repeated impact and fatigue loadings be made slightly larger during laying up than their intended finished-component dimensions. After curing, followed by trimming or other machining of the edges from these slightly over-sized parts, net-shape components are produced that have very low porosity as well as straight fibers in each layer and substantially no entrapped air.

[0045] In some embodiments, the composite face plate can be provided with its final desired shape and dimensions by die cutting. Any desired bulge and roll of the face plate may be formed during the last of two or more "debulking" or compaction steps (performed before curing, to remove and/or reduce air trapped between plies). To form the bulge or roll, the "last" debulking step can be performed against a die panel having the final desired bulge and roll. If desired, yet another (and subsequent) debulking step can be performed using the die panel to achieve the final face-plate thickness. The weight and thickness of the face plate desirably are measured before the curing step.

[0046] FIGS. 3(A)-3(C) depict an embodiment of a process (pressure and temperature as functions of time) in which slow and steady resin flow is performed with minimal resin loss. FIG. 3(A) shows temperature of the lay-up as a function of time. The lay-up temperature is substantially the same as the tool temperature. The tool is maintained at an initial tool temperature T.sub.i, and the uncured prepreg lay-up is placed or formed in the tool at an initial pressure P.sub.1 (typically atmospheric pressure). The tool and uncured prepreg is then placed in a hot-press at a tool-set temperature T.sub.s, resulting in an increase in the tool temperature (and thus the lay-up temperature) until the tool temperature eventually reaches equilibrium with the set temperature T.sub.s of the hot-press. This temperature increase desirably is "ramped," by which is meant a progressive increase. As the temperature of the tool increases from T.sub.i to T.sub.s, the hot-press pressure is kept at P.sub.1 for t=0 to t=t.sub.1. At t=t.sub.1, the hot-press pressure is increased (desirably in a ramped manner) from P.sub.1 to P.sub.2 such that, at t=t.sub.2, P=P.sub.2. Between T.sub.i and T.sub.s, the temperature increase of the tool and lay-up is continuous. Exemplary rates of change of temperature and pressure are: .DELTA.T.about.(60 C)/(120 sec) up to t.sub.1, and .DELTA.P.about.(150 psi)/(300 sec) from t.sub.1 to t.sub.2.

[0047] As the tool temperature increases from T.sub.i to T.sub.s, the viscosity of the resin first decreases to a minimum, at time t.sub.1, before the viscosity rises again due to cross-linking of the resin (FIG. 3(B)). At time t.sub.1, resin flows relatively easily. This increased flow poses an increased risk of resin loss, especially if the pressure in the tool is elevated. Elevated tool pressure at this stage also causes other undesirable effects such as a more agitated flow of resin. Hence, tool pressure should be maintained relatively low at and around t.sub.1 (see FIG. 3(C)). After t.sub.1, cross-linking of the resin begins and progresses, causing a progressive rise in resin viscosity (FIG. 3(B)), so tool pressure desirably is gradually increased in the time span from t.sub.1 to t.sub.2 to allow (and to encourage) adequate and continued (but nevertheless controlled) resin flow. The rate at which pressure is increased should be sufficient to reach maximum pressure P.sub.2 slightly before the end of rapid increase in resin viscosity. Again, a desired rate of change is .DELTA.P.about.(150 psi)/(300 sec) from t.sub.1 to t.sub.2. At time t.sub.2 the resin viscosity desirably is approximately 80% of maximum.

[0048] Curing continues after time t.sub.2 and follows a schedule of relatively constant temperature T.sub.s and constant pressure P.sub.2. Note that resin viscosity exhibits some continued increase (typically to approximately 90% of maximum) during this phase of curing. This curing (also called "pre-cure") ends at time t.sub.3 at which the component is deemed to have sufficient rigidity (approximately 90% of maximum) and strength for handling and removal from the tool, although the resin may not yet have reached a "full-cure" state (at which the resin exhibits maximum viscosity). A post-processing step typically follows, in which the components reach a "full cure" in a batch mode or other suitable manner.

[0049] Typically after reaching full-cure, the components are subjected to manufacturing techniques (machining, forming, etc.) that achieve the specified final dimensions, size, contours, etc., of the components for use as face plates on club-heads.

[0050] Thus, important parameters of this process are: (a) T.sub.s, the tool-set temperature (or typical resin-cure temperature), established according to manufacturer's instructions; (b) T.sub.i, the initial tool temperature, usually set at approximately 50% of T.sub.s (in .degree. F. or .degree. C.) to allow an adequate time span (t.sub.2) between T.sub.i and T.sub.s and to provide manufacturing efficiency; (c) P.sub.1, the initial pressure that is generally slightly higher than atmospheric pressure and sufficient to hold the component geometry but not sufficient to "squeeze" resin out, in the range of 20-50 psig for example; (d) P.sub.2, the ultimate pressure that is sufficiently high to ensure dimensional accuracy of components, in the range of 200-300 psig for example; (e) t.sub.1, which is the time at which the resin exhibits a minimal viscosity, a function of resin properties and usually determined by experiment, for most resins generally in the range of 5-10 minutes after first forming the lay-up; (f) t.sub.2, the time of maximum pressure, also a time delay from t.sub.1, where resin viscosity increases from minimum to approximately 80% of a maximum viscosity (i.e., viscosity of fully cured resin), appears to be related to the moment when the tool reaches T.sub.s; and (g) t.sub.3, the time at the end of the pre-cure cycle, at which the components have reached handling strength and resin viscosity is approximately 90% of its maximum.

[0051] Many variations of this process also can be designed and may work equally as well. Specifically, all seven parameters mentioned above can be expressed in terms of ranges instead of specific quantities. In this sense, the processing parameters can be expressed as follows (see FIGS. 4(A)-4(C)):

[0052] T.sub.s: recommended resin cure temperature.+-..DELTA.T, where .DELTA.T=20, 50, 75.degree. F.

[0053] T.sub.i: initial tool temperature (or T.sub.s/2).+-..DELTA.T.

[0054] P.sub.1: 0-100 psig.+-..DELTA.P, where .DELTA.P=5, 10, 15, 25, 35, 50 psi.

[0055] P.sub.2: 200-500 psig.+-..DELTA.P.

[0056] t.sub.1: t(minimum.+-..DELTA.x viscosity).+-..DELTA.t, where .DELTA.x=1, 2, 5, 10, 25% and .DELTA.t=1, 2, 5, 10 min.

[0057] t.sub.2: t(80%.+-..DELTA.x maximum viscosity).+-..DELTA.t.

[0058] t.sub.3: t(90%.+-..DELTA.x maximum viscosity).+-..DELTA.t.

[0059] The potential mass "savings" obtained from fabricating at least a portion of the face plate of composite, as described above, is about 10-30 g, or more, relative to a 2.7-mm thick face plate formed from a titanium alloy such as Ti-6Al-4V, for example.

[0060] The methods described above provide improved structural integrity of the face plates and other club-head components manufactured according to the methods, compared to composite component manufactured by prior-art methods.

[0061] These methods can be used to fabricate face plates for any of various types of clubs, such as (but not limited to) irons, wedges, putter, fairway woods, etc., with little to no process-parameter changes.

[0062] The subject methods are especially advantageous for manufacturing face plates because face plates are the most severely loaded components in golf club-heads. Conventional (and generally less expensive) composite-processing techniques (e.g., bladder-molding, etc.) can be used to make other parts of a club-head not subject to such severe loads.

[0063] Attaching a composite face plate to the club-head body may be achieved using an appropriate adhesive (typically an epoxy adhesive or a film adhesive). To prevent peel and delamination failure at the junction of an all-composite face plate with the body of the club-head, the composite face plate can be recessed from or can be substantially flush with the plane of the forward surface of the metal body at the junction. Desirably, the composite face plate is sufficiently recessed so that the ends of the fibers in the plies are not exposed.

[0064] In other embodiments as shown, for example, in the partial section depicted in FIG. 5, the face plate 12 comprises a metal "cap" 90 formed or placed over a composite plate 92 to form the strike surface 13. The cap 90 includes a peripheral rim 94 that covers the peripheral edge 96 of the composite plate 92. The rim 94 can be continuous or discontinuous, the latter comprising multiple segments (not shown). For a cap 90 made of titanium alloy, the thickness of the titanium desirably is less than about 1 mm, and more desirably less than 0.2 mm. The candidate titanium alloys are not limited to Ti-6Al-4V, and the base metal of the alloy is not limited to titanium. Other materials or titanium alloys can be employed as desired. In one example, in which the thickness of the composite plate 92 was about 3.65 mm, a titanium cap 90 was used having a thickness of about 0.3 mm.

[0065] The metal cap 90 desirably is bonded to the composite plate 92 using a suitable adhesive 98, such as an epoxy, polyurethane, or film adhesive. The adhesive 98 is applied so as to fill the gap completely between the cap 90 and the composite plate 92 (this gap usually in the range of about 0.05-0.2 mm, and desirably is approximately 0.1 mm). The face plate 12 desirably is bonded to the body 14 using a suitable adhesive 100, such as an epoxy adhesive, which fills the gap completely between the rim 94 and the peripheral member 80 of the face support 18. When thus assembled, the face plate 12 contacts the rear member 84 of the face support 18. Similarly, if the face plate 12 lacks a metal cap 90, the face plate can be placed on the face support 18 and bonded to the body 14 using a suitable adhesive that fills the gap completely between the peripheral edge 96 of the composite plate and the peripheral member 80 as the composite plate contacts the rear member 84.

[0066] A particularly desirable metal for the cap 90 is titanium alloy, such as the particular alloy used for fabricating the body (e.g., Ti-6Al-4V). For a cap 90 made of titanium alloy, the thickness of the titanium desirably is less than about 1 mm, and more desirably less than 0.2 mm. The candidate titanium alloys are not limited to Ti-6Al-4V, and the base metal of the alloy is not limited to Ti. Other materials or Ti alloys can be employed as desired. In one example, in which the thickness of the composite plate 92 was about 3.65 mm, a titanium cap 90 was used having a thickness of about 0.3 mm.

[0067] Surface roughness can be imparted to the composite plate 92 (notably to any surface thereof that will be adhesively bonded to the body of the club-head and/or to the metal cap 92). In a first approach, a layer of textured film is placed on the composite plate 92 before curing the film (e.g., "top" and/or "bottom" layers discussed above). An example of such a textured film is ordinary nylon fabric. Conditions under which the adhesives 98, 100 are cured normally do not degrade nylon fabric, so the nylon fabric is easily used for imprinting the surface topography of the nylon fabric to the surface of the composite plate. By imparting such surface roughness, adhesion of urethane or epoxy adhesive, such as 3M.RTM. DP 460, to the surface of the composite plate so treated is improved compared to adhesion to a metallic surface, such as cast titanium alloy.

[0068] In a second approach, texture can be incorporated into the surface of the tool used for forming the composite plate 92, thereby allowing the textured area to be controlled precisely and automatically. For example, in an embodiment having a composite plate joined to a cast body, texture can be located on surfaces where shear and peel are dominant modes of failure.

[0069] The composite face plate as described above need not be coextensive (dimensions, area, and shape) with a typical face plate on a conventional club-head. Alternatively, a subject composite face plate can be a portion of a full-sized face plate, such as the area of the "sweet spot." Both such composite face plates are generally termed "face plates" herein.

EXAMPLE

[0070] In this example, the resin was Newport 301-1 epoxy resin. T.sub.s=270.+-.5.degree. F.; T.sub.i=140.+-.5.degree. F.; P.sub.1=30.+-.10 psi; P.sub.2=200.+-.10 psi; t.sub.1=5.+-.2 min; t.sub.2=8.+-.2 min; and t.sub.3=25.+-.5 min.

[0071] Whereas the invention has been described in connection with representative embodiments, it will be understood that the invention is not limited to those embodiments. On the contrary, the invention is intended to encompass all modifications, alternatives, and equivalents as may fall within the spirit and scope of the invention, as defined by the appended claims.

Claims

1. A method for fabricating a composite face plate for a club-head of a golf club, the method comprising: forming a lay-up comprising multiple prepreg layers, each prepreg layer comprising at least one layer of respective fibers at a respective orientation, the at least one fiber layer being impregnated with a resin; exposing the lay-up to an initial tool temperature T.sub.i and an initial pressure P.sub.1; beginning at a time t.sub.1 at which the resin exhibits a minimal liquid viscosity, commencing an increase in temperature of the lay-up from T.sub.i and an increase in pressure of the lay-up from P.sub.1; during a first interval between the time t.sub.1 and a later time t.sub.2, increasing the temperature of the lay-up to T.sub.s>T.sub.i and increasing the pressure of the lay-up to P.sub.2>P.sub.1, during which first interval the resin exhibits a relatively rapid progressive increase in viscosity; and during a second interval between the time t.sub.2 and a later time t.sub.3, maintaining the lay-up substantially at the temperature T.sub.s and substantially at the pressure P.sub.2, thereby allowing the resin to undergo a relatively slow but continued increase in viscosity to a specified pre-cure viscosity level.

2. The method of claim 1, wherein: the increase in temperature of the lay-up from T.sub.i is ramped; and the increase in pressure of the lay-up from P.sub.1 is ramped.

3. The method of claim 2, wherein, between the times t.sub.1 and t.sub.2: the temperature of the lay-up is ramped up to T.sub.s>T.sub.i; and the pressure of the lay-up is ramped up to P.sub.2>P.sub.1,

4. The method of claim 1, wherein, between the times t.sub.1 and t.sub.2: the temperature of the lay-up is ramped up to T.sub.s>T.sub.i; and the pressure of the lay-up is ramped up to P.sub.2>P.sub.1,

5. The method of claim 1, further comprising, after the time t.sub.3, decreasing the temperature from T.sub.s and decreasing the pressure from P.sub.2.

6. The method of claim 4, further comprising shaping the lay-up to have specified dimensions and shape for use as a face plate for a club-head.

7. The method of claim 1, further comprising, after the time t.sub.3, completing a full-cure of the lay-up, the full-cure being characterized by the resin exhibiting a maximal viscosity.

8. The method of claim 7, further comprising shaping the full-cured lay-up to have specified dimensions and shape for use as a face plate for a club-head.

9. The method of claim 1, wherein the lay-up is formed in a tool configured to hold the lay-up as the lay-up is being exposed to the temperatures T.sub.i and T.sub.s and to the pressures P.sub.1 and P.sub.2.

10. The method of claim 9, further comprising removing the lay-up from the tool when the lay-up has reached the specified pre-cure viscosity level.

11. The method of claim 8, further comprising shaping a contour of the lay-up while the lay-up is in the tool.

12. The method of claim 1, wherein the pressure P.sub.1 is within a range 0-100 psig.

13. The method of claim 1, wherein the pressure P.sub.1 is within the range 0-100 psig.+-..DELTA.P, wherein .DELTA.P is a maximum of 50 psi.

14. The method of claim 1, wherein the pressure P.sub.2 is within a range 200-500 psig.

15. The method of claim 1, wherein the pressure P.sub.2 is within a range 200-500 psig.+-..DELTA.P, wherein .DELTA.P is a maximum of 50 psi.

16. The method of claim 1, wherein the temperature T.sub.s=T.sub.r.+-..DELTA.T, wherein T.sub.r is a manufacturer's recommended cure temperature for the resin, and .DELTA.T is a maximum of 75.degree. F.

17. The method of claim 16, wherein the temperature T.sub.i=T.sub.s/2.+-..DELTA.T.

18. The method of claim 1, wherein, at the time t.sub.1: the minimum viscosity of the resin is in a range of .+-..DELTA.x; .DELTA.x is a maximum of 25%; the time t.sub.1 is in a range of .+-..DELTA.t; and .DELTA.t is a maximum of 10 minutes.

19. The method of claim 1, wherein, at the time t.sub.2: the resin has reached 80% of its maximum viscosity X.sub.m; X.sub.m is in a range of .+-..DELTA.x; and .DELTA.x is a maximum of 25%.

20. The method of claim 1, wherein: the time t.sub.2 is in a range of .+-..DELTA.t; and .DELTA.t is a maximum of 10 minutes.

21. The method of claim 1, wherein, at the time t.sub.3: the resin has reached 90% of its maximum viscosity X.sub.m; X.sub.m is in a range of .+-..DELTA.x; and .DELTA.x is a maximum of 25%.

22. The method of claim 21, wherein: the time t.sub.3 is in a range of .+-..DELTA.t; and .DELTA.t is a maximum of 10 minutes.

23. The method of claim 1, wherein: the pressure P.sub.1 is within the range 0-100 psig.+-..DELTA.P, wherein .DELTA.P is a maximum of 50 psi; the pressure P.sub.2 is within a range 200-500 psig.+-..DELTA.P, wherein .DELTA.P is a maximum of 50 psi; the temperature T.sub.s=T.sub.r.+-..DELTA.T, wherein T.sub.r is a manufacturer's recommended cure temperature for the resin, and .DELTA.T is a maximum of 75.degree. F.; the temperature T.sub.i=T.sub.s/2.+-..DELTA.T; and at the time t.sub.1 the minimum viscosity of the resin is in a range of .+-..DELTA.x, wherein .DELTA.x is a maximum of 25%, the time t.sub.1 is in a range of .+-..DELTA.t, and .DELTA.t is a maximum of 10 minutes.

24. The method of claim 23, wherein, at the time t.sub.2 the resin has reached 80% of its maximum viscosity X.sub.m, X.sub.m is in the range of .+-..DELTA.x, and the time t.sub.2 is in the range of .+-..DELTA.t.

25. The method of claim 24, wherein, at the time t.sub.3 the resin has reached 90% of its maximum viscosity X.sub.m, X.sub.m is in the range of .+-..DELTA.x, and the time t.sub.3 is in the range of .+-..DELTA.t.

26. The method of claim 1, wherein the pressure is increased from P.sub.1 to P.sub.2 at a rate in which the pressure P.sub.2 is reached before the resin viscosity ceases its relatively rapid increase.

27. The method of claim 1, wherein the prepreg layers comprise carbon fiber and epoxy resin.