Patent Application
20190381377
Composite ball bats for baseball or softball are often made with one or more layers or plies of composite laminate material. In an assembled composite bat, the composite layers are often concentrically arranged, such that an inner layer forms an inner portion of a bat wall while an outer layer forms an outer portion of a bat wall. Composite layers typically include a fiber-reinforced matrix or resin material in which the fibers are parallel with the plane of the layer, such that, in an assembled bat, the fibers are arranged circumferentially around the bat's longitudinal axis, which is often referred to as the bat's X-axis.
In a typical composite bat formed with multiple layers of composite laminate material, the volume of matrix material (sometimes in the form of resin) is higher between the layers (in the interlaminar interfaces) than in the laminate layers themselves. These areas, and other areas in which the matrix material makes up much or all of the assembly, are typically referred to as “resin-rich” areas. Resin-rich areas tend to be weaker than areas reinforced with more fibers. In a typical composite ball bat (and other composite structures), there may be resin rich veins running axially (along the X-axis) within the bat wall. Designers of composite bats consider these areas when determining the overall strength of the bat. For example, designers may analyze the interlaminar shear strength of an assembled bat.
During repeated use of composite bats, the matrix or resin of the composite material tends to crack, and the fibers tend to stretch or break. Sometimes the composite material develops interlaminar failures, which involve plies or layers of the composite materials separating or delaminating from each other along a failure plane between the layers in the interlaminar interface. For example, the plies may separate along the resin-rich areas. This “break-in” reduces stiffness and increases the elasticity or trampoline effect of a bat against a ball, which tends to temporarily increase bat performance. Typically, the separation of the plies along the resin-rich areas results in fracturing between the plies, but the fibers in the plies generally resist cracking through the thickness of the plies.
As a bat breaks in, and before it fully fails (for example, before the bat wall experiences a through-thickness failure), it may exceed performance limitations specified by a governing body, such as limitations related to batted ball speed. Some such limitations are specifically aimed at regulating the performance of a bat that has been broken in from normal use, such as BBCOR (“Bat-Ball Coefficient of Restitution”) limitations.
Some unscrupulous players choose to intentionally break in composite bats to increase performance. Intentional break-in processes may be referred to as accelerated break-in (ABI) and may include techniques such as “rolling” a bat or otherwise compressing it, or generating hard hits to the bat with an object other than a ball. Such processes tend to be more abusive than break-in during normal use, and they exploit the relatively weak interlaminar shear strength of resin-rich areas found in the composite structures of typical ball bats to try to increase batted ball speed. Some sports governing bodies require that composite bats meet certain standards even after an ABI procedure in order to limit the increase in performance from use and abuse of a composite bat.
Representative embodiments of the present technology include a ball bat with a barrel wall formed at least in part by a plurality of concentric first composite laminate layers and a plurality of second composite laminate layers oriented transverse to the first composite laminate layers. In some embodiments, a ball bat may include composite material with a plurality of fibers oriented along a direction transverse to the longitudinal axis of the bat.
Other features and advantages will appear hereinafter. The features described above can be used separately or together, or in various combinations of one or more of them.
In the drawings, wherein the same reference number indicates the same element throughout the several views:
The present technology is directed to composite ball bats with transverse fibers and associated systems and methods. Various embodiments of the technology will now be described. The following description provides specific details for a thorough understanding and enabling description of these embodiments. One skilled in the art will understand, however, that the invention may be practiced without many of these details. Additionally, conventional or well-known aspects of ball bats and composite materials may not be shown or described in detail so as to avoid unnecessarily obscuring the relevant description of the various embodiments. Accordingly, embodiments of the present technology may include additional elements, or may exclude some of the elements described below with reference to
The terminology used in this description is intended to be interpreted in its broadest reasonable manner, even though it is being used in conjunction with a detailed description of certain specific embodiments of the invention. Certain terms may even be emphasized below; however, any terminology intended to be interpreted in any restricted manner will be overtly and specifically defined as such in this detailed description section.
Where the context permits, singular or plural terms may also include the plural or singular term, respectively. Moreover, unless the word “or” is expressly limited to mean only a single item exclusive from the other items in a list of two or more items, then the use of “or” in such a list is to be interpreted as including (a) any single item in the list, (b) all of the items in the list, or (c) any combination of items in the list. Further, unless otherwise specified, terms such as “attached” or “connected” are intended to include integral connections, as well as connections between physically separate components.
Specific details of several embodiments of the present technology are described herein with reference to baseball or softball but the technology may be used in other activities, and it is not limited to use with ball bats.
The bat 100 may have any suitable dimensions. For example, the bat 100 may have an overall length of 20 to 40 inches, or 26 to 34 inches. The overall barrel diameter may be 2.0 to 3.0 inches, or 2.25 to 2.75 inches. Typical ball bats have diameters of 2.25, 2.625, or 2.75 inches. Bats having various combinations of these overall lengths and barrel diameters, or any other suitable dimensions, are contemplated herein. The specific preferred combination of bat dimensions is generally dictated by the user of the bat 100, and may vary greatly among users.
The barrel portion 110 may be constructed with one or more composite materials. Some examples of suitable composite materials include laminate plies reinforced with fibers of carbon, glass, graphite, boron, aramid (such as Kevlar®), ceramic, or silica (such as Astroquartz®). The handle portion 120 may be constructed from the same materials as, or different materials than, the barrel portion 110. In a two-piece ball bat, for example, the handle portion 120 may be constructed from a composite material (the same or a different material than that used to construct the barrel portion 110), a metal material, or any other material suitable for use in a striking implement such as the bat 100.
The ball striking area of the bat 100 typically extends throughout the length of the barrel portion 110, and may extend partially into the taper portion 130 of the bat 100. The barrel portion 110 generally includes a “sweet spot,” which is the impact location where the transfer of energy from the bat 100 to a ball is generally maximal, while the transfer of energy (such as shock or vibration) to a player's hands is generally minimal. The sweet spot is typically located near the bat's center of percussion (COP), which may be determined by the ASTM F2398-11 Standard. Another way to define the location of the sweet spot is between the first node of the first bending mode and the second node of the second bending mode. This location, which is typically about four to eight inches from the distal free end of the bat 100 (the end with the optional cap 150), generally does not move when the bat is vibrating. For ease of measurement and description, the “sweet spot” described herein coincides with the bat's COP.
For purposes of orientation and context for the description herein,
In accordance with an embodiment of the present technology, one or more secondary layers 430 of composite laminate material may be positioned in the wall and oriented generally along the Z-axis, in the Z-Y plane, transverse (such as perpendicular or oblique) to the concentric layers 400. Such an arrangement provides radially-oriented interlaminar interfaces or shear areas between the secondary layers 430 along the Z-axis, in the Z-Y plane. For example, a resin-rich area may be formed between the layers 430 but oriented along the Z-axis (radially) rather than along the longitudinal X-axis (as is the case for the resin-rich areas between the concentric layers 400).
When subjected to an ABI procedure, a barrel wall according to embodiments of the present technology may develop faults or cracks, or fail through the thickness of the wall (along the Z-axis), rather than along the length (X-axis) of the wall. The secondary layers 430 may also stop the proliferation of cracks or faults between the concentric layers 400. By orienting the fiber axes in the Z-Y plane (radially), the hoop stiffness of the barrel will remain generally intact even if the veins of resin between secondary layers 430 have cracked. This limits or resists increases in trampoline effect from normal break-in or ABI.
In some embodiments, the secondary layers 430 may be made of the same material as, or different material from, the primary or concentric layers 400. In some embodiments, the fibers in the secondary layers 430 may be uniformly aligned with each other along a direction in the Z-Y plane. For example, in some embodiments, the fibers may be aligned with the Z-axis, or they may be aligned with the Y-axis, or they may be aligned with a direction between the Z-axis or the Y-axis, such as between 0 and 90 degrees relative to the Z-axis. In some embodiments, the fibers may be oriented in a hoop arrangement or a circumferential direction around the barrel. In other embodiments, the fibers may be radially-oriented along directions extending from the bat's X-axis, or otherwise transverse to the X-axis. In other embodiments, the fibers in the secondary layers 430 may be aligned in other directions, and in accordance with various embodiments, they may or may not be uniformly aligned.
For ease of description only, an arrangement or grouping of secondary layers 430, such as the arrangement or grouping of secondary layers 430 illustrated in
In some embodiments, a designer may select a length L of a Z-stack based on the interlaminar strength of the other parts of the barrel wall (for example, the primary or concentric layers 400) and the desired performance (such as trampoline effect) of the bat. A longer length L of a Z-stack correlates with less performance increase in the bat during use or abuse, such as ABI. In some embodiments, a length L of a Z-stack may be between approximately 0.125 inches and 10 inches. In some embodiments, a length L of a Z-stack may be between one inch and four inches, depending on the length of the ball striking area and the characteristics of the resin-rich areas between various layers, or on other factors.
In some embodiments, a thickness T of a Z-stack may be selected based on the interlaminar strength of the materials in the Z-stack (such as the type of composite ply). The interlaminar strength correlates with the strength of the interlaminar interfaces 440, which are the interfaces between adjacent secondary layers 430 in the Z-stack.
For example, if the materials in the Z-stack have high interlaminar strength, the thickness T of the Z-stack (which may also be the thickness T of the interlaminar interfaces between the secondary layers 430) may be approximately five to ten percent of the overall wall thickness W. In some embodiments, the Z-stack thickness T may be 75 percent or more of the overall wall thickness W. In general, the Z-stack thickness T may be any suitable fraction of the overall wall thickness W, and the Z-stack thickness T may be limited to what is suitable for preventing or at least resisting exceeding the interlaminar strength of the primary layers 400 during use or abuse.
As illustrated in
In some embodiments, a bat wall, such as a barrel wall 200 (see
The secondary layers 430 (and their corresponding fibers therein) may be transverse (such as perpendicular or oblique) to the primary or concentric layers 400, or otherwise oriented generally along the Z-axis. Accordingly, interlaminar interfaces 440 between the secondary layers 430 may be transverse (such as perpendicular or oblique) to the concentric layers 400.
Each strip 518 may have a length L1 equal to or approximately equal to one half of the circumference of a Z-stack. A bat designer would understand how to select the circumference of a Z-stack based on the dimensions of a ball bat and the position of the Z-stack in the bat (such as in the barrel wall 200), using basic geometry considerations. In a second step, in box 520, the strips 518 may be arranged in a stack 525. The number of strips 518 in a stack 525 may correspond to the length L of a Z-stack (see
The methods 500, 600 illustrated in
In some embodiments, the sock 810 may be a tube formed with a pre-preg material having woven or braided glass, carbon, or aramid fibers, or any other suitable fiber material, including other fiber materials mentioned herein. The sock 810 may be pushed onto a mandrel between the concentric layers 400 (to form the wrinkles and layers 820) and co-cured with the concentric layers 400.
In some embodiments, the sock 810 may not be a pre-preg material. For example, in some embodiments, the sock 810 may be made of fibers, and a layer of resin film may be placed on top of the sock 810 to wet the sock 810 during the curing process. An example method of making an embodiment of the present technology is to place the inner skin material 420 on a bat-shaped mandrel, push the sock 810 onto the mandrel to form wrinkles with layers 820 along the Z-direction or otherwise transverse to the X-axis, then stack concentric layers 400 around the sock 810, then lay a resin film over the sock 810, and then cure the assembly.
In some embodiments, the sock 810 may be formed and cured before being placed into the bat assembly. For example, the sock 810 may be formed with a fiber mat, compressed onto a mandrel to form wrinkles, placed in a mold, injected with resin, cured, then cut into pieces to be added to a composite assembly, between the concentric layers 400.
In some embodiments, other components may form the wrinkled interface that creates the layers 820. For example, in some embodiments, a sheet of material, such as pre-preg material, may be wrapped around the circumference of a mandrel and pushed or wrinkled into a pleated arrangement to form folds constituting the layers 820. The sock 810 or other wrinkled materials provide convenient ways to create interfaces between secondary (for example, transverse) layers and in the Z-Y plane (such as the layers 820).
In some embodiments, the bulk molding compound 910 may be laid up and cured simultaneously with the concentric layers 400 according to various composite manufacturing methods. The bulk molding compound disrupts interlaminar shear fractures between the concentric layers 400 and also limits or prevents proliferation of fractures along the Z-direction (radial direction) of the barrel wall 200. In various embodiments, any suitable number of concentric layers 400 may be used in the barrel wall 200, and in some embodiments, there may be a concentric layer 400 between the bulk molding compound 910 and one or both of the outer and inner skins 410, 420. In some embodiments, the bulk molding compound 910 may be directly adjacent to one or both of the outer and inner skins 410, 420 (without a concentric layer 400 between the bulk molding compound 910 and the outer skin 410 or the inner skin 420).
In some embodiments, the rope 1110 may be laid up with the concentric layers of laminate (see
Embodiments of the present technology provide multiple advantages. For example, embodiments of the present technology provide interlaminar interfaces or shear interfaces along the Z-axis, in the Z-Y plane, or otherwise radially outward from, or transverse to (such as perpendicular or oblique to), the X-axis. Such interfaces provide less of an increase in trampoline effect, or no increase in trampoline effect, when they fracture, unlike when interfaces along the X-axis fracture. Accordingly, ball bats according to embodiments of the present technology are less prone to unfair performance increases or violations of league rules when the bats are used or abused (such as in an ABI process).
The inventors discovered that fibers or interfaces oriented generally along a Z-direction according to various embodiments of the present technology resist or even prevent delamination along the X-Y plane or along the length of the ball bat. The fibers or plies in the Z-direction may resist a crack running only along the X-axis. Accordingly, bats according to embodiments of the present technology may fail along the Z-direction before they fail along the X-Y plane, so they become disabled after an ABI procedure rather than gaining performance beyond regulations.
From the foregoing, it will be appreciated that specific embodiments of the disclosed technology have been described for purposes of illustration, but that various modifications may be made without deviating from the technology, and elements of certain embodiments may be interchanged with those of other embodiments, and that some embodiments may omit some elements. For example, in some embodiments, composite laminate material may be replaced by or supplemented with sheet molding compound or bulk molding compound. In some embodiments, the quantity of fibers oriented along a direction transverse to the longitudinal axis of the bat may be more than ten percent of a total quantity of fibers in a given portion of the barrel wall.
Further, while advantages associated with certain embodiments of the disclosed technology have been described in the context of those embodiments, other embodiments may also exhibit such advantages, and not all embodiments need necessarily exhibit such advantages to fall within the scope of the technology. Accordingly, the disclosure and associated technology may encompass other embodiments not expressly shown or described herein, and the invention is not limited except as by the appended claims.
