HK1180628B - Ball bat including multiple failure planes - Google Patents

Description

Ball bat with multiple failure surfaces

This application is a continuation of U.S. patent application No.12/652,523, filed on 5.1.2010, which is incorporated herein by reference.

Background

A league of baseball and softball has experienced a dramatic increase in the number of bats that are altered by players to improve the performance of the shot. The most common method of modifying a bat to enhance performance is a practice known as "rolling" in which the bat barrel is placed between two cylinders ("rollers") that are oriented perpendicularly to the longitudinal axis of the barrel. The barrel is compressed into a bat barrel which deflects the bat into a cross-section (fig. 2 shows a schematic view of the rolling arrangement). While the barrel is in compression mode, the ball bat is moved along its longitudinal axis by the compression roller to compress the barrel along most of its length. This rolling is typically repeated at least 10 times and is typically performed about every 45 ° around the circumference of the barrel.

To achieve higher performance, players typically repeat the rolling process with a significant enough bias to break the interlaminar shear strength in the barrel, which severely alters barrel dynamics. The principle of achieving this is commonly referred to as accelerated breakthrough ("ABI").

Methods to induce ABI typically target weak interlaminar regions of the composite structure, resulting in interlaminar fracture or delamination. Delamination is a mode of failure that causes the composite layers within the structure to separate, resulting in the mechanical toughness of the composite structure being significantly reduced. The strength of a composite structure failing through delamination is often referred to as its interlaminar shear strength. Delamination typically occurs at or near the neutral axis of the barrel web and serves to reduce barrel compressibility of the ball bat, thereby increasing barrel resiliency and "trampoline effect" (i.e., barrel performance). While taking this process shortens bat life, players often choose a short enhancement in performance rather than durability.

For many softball bats, ABI roll deflections of about 0.20 inches or more may be achieved before the barrel initially fails and performance improves. The actual amount of deflection required depends on the overall durability of the barrel design: the more durable the barrel design, the more the barrel can resist deflection without increasing performance. Conversely, the design of the lower durable veneer layer may only be able to withstand approximately 0.10 inches of deflection, for example, before the performance of the barrel has improved.

To help prevent the use of clubs that do not allow for change, the amateur softball association ("ASA") implemented a new test method that required all softball clubs to meet performance limitations even after the club was rolled an unlimited number of times. ASA requires that the bat remain below or break through selected performance limits during testing (currently tested at 98 miles per hour according to astm f 2219). Sufficient breakage of the bat requires attention by the player or referee on the course.

NCAA recently adopted an ABI-like protocol for composite baseball bats. The protocol uses astm f2219 to test the performance level of the bat, which is calculated as the bat-ball coefficient of restitution ("BBCOR"). The protocol requires roll-through of the bat to test for performance enhancements that may result when the bat is over-stressed or damaged. BBCOR and barrel compressibility were tested when the bat was new or undamaged. If the bat test is below the established performance limit, the bat is later rolled. If the barrel compressibility changed by at least 15%, the bat BBCOR was retested. If the barrel compressibility did not change by 10%, the bat was rolled again with an increased 0.0125 "bias. This loop is repeated until the bat exceeds a performance limit or passes a protocol. To pass the agreement, the bat must exhibit at least a 0.014 reduction in bat break-away rate ("BESR") or a 0.018 reduction in BBCOR, or the bat must break through a point at which the test bat no longer provides a measurable rebound velocity.

The dramatic increase in player changes bat behavior forces the association to pass the failure test compound bat all the way to ensure that they do not exceed performance limits at any time. The focus of the bat design must accommodate this variation.

Disclosure of Invention

The composite ball bat includes a plurality of failure surfaces in the barrel wall. By including multiple failure planes in the barrel wall, the ball bat exhibits a performance degradation when subjected to rolling or other extreme deflections without a transient increase in barrel performance. Because the barrel performance is not increased, the bat can meet the regulatory association-specified performance limits.

Other features and advantages will appear hereinafter. The features described above can be used individually or collectively, or in various combinations of one or more of them.

Drawings

In the drawings, wherein like reference numerals refer to like parts throughout the several views:

FIG. 1 is a perspective view of a ball bat according to an embodiment;

FIG. 2 is a schematic view of a bat being compressed in a rolling device;

FIG. 3 is a table containing shear force characteristics for three alternative composite bat designs;

FIG. 4 is a table containing BEST test results for a durable bat design and a multiple fault face bat design;

fig. 5A-5D are perspective views of four embodiments of perforated partial barrier layers that may be included between composite layers in a ball bat.

Detailed Description

Various embodiments of the invention will now be described. The following description provides specific details for a thorough understanding and explanation of these embodiments. One skilled in the art will recognize, however, that the invention may be practiced without many of these details. Additionally, some well-known structures or features may not be shown or described in detail to avoid unnecessarily obscuring the relevant description of the various embodiments.

The terminology used in the description presented below is intended to be interpreted in its most reasonable manner, even though it is being used in conjunction with a detailed description of certain specific embodiments of the invention. However, any terminology intended to be emphasized below is intended to be interpreted in any limited manner, as will be apparent and clearly defined in this detailed description.

Where the context permits, singular or plural terms may also include the plural or singular term, respectively. Furthermore, unless "or" is expressly limited to mean only a single item and excludes other items from a list of two or more items, then the use of "or" in such a list should be interpreted to include: (a) any single item in the list, (b) all items in the list, or (c) any combination of items in the list.

Referring now to the detailed illustration, as shown in FIG. 1, a baseball or softball bat 10, hereinafter collectively referred to as a "bat" or "bat," includes a handle 12, a barrel 14, and a tapered section 16 connecting the handle 12 to the barrel 14. The free end of the handle 12 includes a knob 18 or similar structure. The barrel 14 is preferably closed by a suitable cap 20 or plug. The interior of the bat 10 is preferably hollow, allowing the bat 10 to be relatively lightweight so that a player may develop a considerable swing speed while swinging the bat 10. For example, the ball bat 10 may be a single piece structure or may include two or more separate joints (e.g., separate handles and barrels), as described in U.S. patent 5,593,158, which is incorporated herein by reference.

The club barrel 14 is preferably constructed of one or more composite materials that are co-processed during barrel molding. Some examples of suitable composite materials include those made of carbon, glass, graphite, boron, aramid, ceramic, Kevlar (Kevlar), orThe fiber-reinforced layer of (a). The bat handle 12 may be constructed of the same material as the barrel 14 or a different material. For example, in a two-piece ball bat, the handle 12 may be constructed of a composite material (the same or a different material than that used to construct the barrel), a metallic material, or any other suitable material.

The barrel 14 may comprise a single wall, multi-walled construction. For example, a multiwall rod cartridge may comprise cartridge walls separated by one or more interfacial shear control zones ("ISCZs"), as described in U.S. Pat. No. 7,115,054, which is incorporated herein by reference. For example, the ISCZ may include a peel ply or other element, structure or space suitable for resisting the transfer of shear stress between adjacent cylinder walls. The peel ply or other ISCZ preferably further prevents bonding of adjacent barrel walls to each other during curing of the bat 10 and throughout the life of the bat 10.

The ball bat 10 may have any suitable dimensions. The bat 10 may have an overall length of 20 to 40 inches or 26 to 34 inches. The overall barrel diameter is 2.0 to 3.0 inches or 2.25 to 2.75 inches. Typical bats have diameters of 2.25, 2.625, or 2.75 inches. Rods having various combinations of these overall lengths and rod barrel diameters or any other suitable dimensions are contemplated herein. The particular preferred combination of pole sizes will generally depend on the user of the pole 10 and may vary widely between users.

Fig. 2 schematically illustrates a rolling device in which a roller 25 is used to compress the barrel 14 along the length of the barrel 14 from a location approximately 2.0-2.5 feet from the end of the bat 10 to the tapered section 16 of the bat 10. As explained above, when the bat is deflected to a failure point, delamination typically occurs between the layers at or near the neutral axis of the barrel 14 as a result of rolling or another deflection-induced stimulus. In a single wall bat, there is a single neutral axis, defined as the axis of gravity associated with all deformations occurring. Shear forces in the barrel wall are typically greatest along this neutral axis. In a multi-wall bat, there is a separate neutral axis in each barrel wall.

The radial position of the neutral axis in the wall of the rod barrel will vary depending on the distribution of the composite layers and the stiffness of the particular layer. If the rod barrel wall is made up of uniform, isotropic layers, the neutral axis will be located at the radial midpoint of the wall. If more than one composite material is used in the wall, or if the materials are not uniformly distributed, the neutral axis may exist at different radial positions, as will be appreciated by those skilled in the art. For purposes of the embodiments described herein, the neutral axis for a given shaft wall will generally be assumed to be at or near the radial midpoint of the shaft wall.

The location of a fault where delamination occurs between the composite layers, such as at or near the neutral axis, will generally be referred to herein as a fault plane. To prevent the increase in barrel flexibility and, therefore, barrel performance, which typically occurs when delamination is induced in a composite ball bat, at least one additional failure plane is created or provided in the barrel wall of the ball bat described herein.

In a single wall bat, at least one additional failure plane is disposed in a single barrel wall. In a multi-walled bat, where each wall includes its own neutral axis, additional failure planes are disposed in at least one of the barrel walls. For example, in a double-walled bat, at least one additional failure plane may be disposed in at least one barrel wall, and optionally in both barrel walls. For ease of description, single wall bats will generally be described in the remainder of this detailed description.

When the barrel is subjected to rolling or other extreme deflections, the inclusion of one or more additional failure planes in the barrel wall causes the barrel to fail at multiple locations simultaneously or nearly simultaneously. This failure at multiple locations produces a dramatic drop in barrel performance such that no temporary increase in barrel performance occurs. In a preferred embodiment, there are at least two additional failure planes, on either side of the neutral axis, disposed within a given shaft wall.

For example, in one embodiment, the additional failed wall may be located approximately one-quarter and three-quarters of the radial thickness of the barrel wall (or in one-quarter and three-quarter sections and modular moments of inertia) as measured from the outer surface of the barrel 14. Thus, assuming that the neutral axis of the barrel is located approximately at the radial midpoint of the barrel wall, the fault plane is located at about one-quarter, one-half, and three-quarters of the radial thickness of the barrel 14. Providing additional failure planes at these locations is preferred because after the barrel wall fails at its primary neutral axis, the barrel wall essentially immediately becomes a double-walled structure, e.g., the neutral axis exists on each side of the failure location (which typically occurs at approximately the radial midpoint of each newly constructed wall, i.e., one-quarter and three-quarters of the entire barrel wall).

Once a fault occurs in the primary neutral axis, the fault occurs simultaneously or nearly simultaneously in the additional fault planes. One or more additional failure planes may optionally be located elsewhere within the barrel layer when the barrel is subjected to rolling or other extreme deflections, so that a compound failure prevents any increase in barrel performance as long as the barrel fails at multiple failure planes simultaneously or nearly simultaneously.

Additional fault planes may be created in a variety of different ways. In one embodiment, a sharp discontinuity in modulus is provided between adjacent composite layers in the barrel layers to create a failure plane. Such discontinuities may be provided by significantly changing the fiber angle in adjacent layers, resulting in severe drops in barrel compression at these locations. For example, a layer including carbon fibers at a zero angle with respect to the longitudinal axis of the bat may be disposed adjacent to a layer including glass fibers at a 60 angle with respect to the longitudinal axis of the bat. The carbon layer may optionally include low tensile carbon fibers that are less ductile than high tensile carbon fibers and have a lower elongation (i.e., they are more brittle) and thus provide more predictable failure. For example, high modulus carbon fibers having less than 1% elongation may be used.

The table of fig. 3 shows the shear stress distribution in three composite ball bats, each of which includes 13 layers:

(1) a single failure face, all-carbon bat with a uniform or constant 30 ° fiber angle throughout the several layers;

(2) a single failure face, strong, durable, primarily glass ball bat having an outer carbon layer (layer 1) and a central carbon layer (layer 7), the carbon layers having fiber angles ranging from 0 to 60 °, and no change in fiber angle between adjacent carbon layers of more than 30 °; and

(3) the multi-failure face, primarily glass bat includes two additional carbon layers (relative to the second bat) with fibers at an angle of 0 in layers 4 and 10 and glass fibers at an angle of 60 in layers 3 and 11.

As shown, the sharp discontinuity in modulus that caused the 60 fiber angle change between layers 3 and 4 and layers 10 and 11 in the third bat significantly increased the shear forces in the sheet set in these regions (166.6 psi and 132.3psi, respectively) to create additional failure planes. Those skilled in the art will appreciate that other variations in fiber angle between adjacent layers (e.g., at least about 45) may alternatively be used, depending on the materials used (e.g., fiber angle variations need not be extreme if the fiber modulus between the materials used in adjacent layers is very different), including the number of failure planes in a given barrel wall, the particular tests to which the barrel design is to be subjected, etc. Variations in fiber angle between adjacent layers of about 60 ° are preferred, however, such variations necessarily create an additional failure plane while providing sufficient durability for the bat to lift when used as intended (i.e., when not subjected to rolling or other extreme deflections).

The table of fig. 4 compares the BESR of the second and third bat types described above when subjected to ABI rolling for various barrel deflections. As shown in the table, at 0.113 inches of deflection, the durable second bat exhibited an increase in performance or BESR (so that the bat failed the BESR test), while the third bat included multiple failure planes exhibiting a decrease in performance or BESR (so that it passed the BESR test). Thus, multiple failure planes in the third bat caused a significant decrease in barrel performance when subjected to ABI rolling, while the performance of the more durable second bat increased beyond acceptable limits.

While some variation in fiber angles between adjacent composite layers in a ball bat has been used with existing bat design barrels, the significant variations described herein have not been used or even contemplated because the goals of conventional bat designs are generally to increase bat performance and durability. Conversely, by so significantly changing the fiber angle between adjacent composite plies in the barrel wall, the bat barrel described herein intentionally reduces durability (once the barrel is deflected to a point where interlaminar shear forces cause delamination between the carbon layers located at the principal neutral axis of the barrel wall) so that barrel performance does not exceed specified performance limits.

In another embodiment, one or more partial barrier layers may be used to create additional failure planes in a bat barrel. Partial barrier layers prevent bonding between portions of adjacent composite layers to reduce the interlaminar shear strength between those layers. Portions of the barrier layer may be comprised of polytetrafluoroethylene, nylon, or any other material suitable for preventing bonding between portions of adjacent composite layers.

Relative to conventional release or release layers, which are typically used to completely or nearly completely separate the walls of a multi-wall bat (e.g., as described in incorporated U.S. patent 7,115,054), a relatively large percentage of the partial barrier layer area includes perforations or other openings such that meaningful bonding between the composite layers located on either side of the barrier layer may occur.

Figures 5A-5D show exemplary embodiments of portions of barrier layers 30, 32, 34, 36. The pores 40, 42, 44, 46 or other openings are preferably included in up to about 85% of the total area of each barrier layer such that the bond area between composite layers on either side of the barrier layer is reduced by at least 15% (relative to embodiments that do not include portions of the barrier layer). Thus, the barrier layer prevents substantial bonding and thus reduces the interlaminar shear strength between adjacent layers, but still allows the carbon layers on either side of the barrier layer to bond more than about 85% of the total area of the barrier layer.

For a ball bat having sufficient durability under normal use conditions, the perforations or other openings are preferably included in up to about 80-85% of the total area of the barrier layer so as to provide sufficient bonding and therefore sufficient durability to withstand normal playing conditions. Conversely, where bats having lower overall durability tend to fail under normal use conditions, perforations or other openings are preferably included in at least about 25% of the total area of the barrier layer so as to provide less bonding and reduce the interlaminar shear strength between the carbon layers on either side of the partial barrier layer.

The barrier layer, which includes one or more portions, reduces the interlaminar shear strength between the composite layers on either side of the barrier layer, thereby creating additional failure planes in the ball bat. Thus, when the club barrel is subjected to rolling or other extreme deflections, the club barrel will fail at multiple failure planes simultaneously or nearly simultaneously so that no transient enhancement in barrel performance occurs. In one embodiment, two partial barrier layers including perforations or openings are included in up to about the remaining 85% of their area at about one-quarter and three-quarters of the diameter thickness of a given barrel wall so that when the bat barrel is subjected to rolling or other extreme deflections, failure will occur at three locations (about at the neutral axis and at two additional failure planes).

In some embodiments, a higher proportion of perforations or openings may be included in portions of the barrier layer, particularly when several portions of the barrier layer are included in a given barrel wall. However, when a two-part barrier layer is included, perforations or other openings are preferably included in up to about 85% of the barrier layer area, as a reduction in bonding of at least 15% is generally sufficient to create a failure plane. Those skilled in the art will appreciate that the appropriate percentage of perforations or openings needed to create a failure plane may depend on the composite material used, the variation in fiber angle between partially bonded composite layers, and other materials in the barrel that reduce bonding between carbon layers, among other things.

In another embodiment, a low shear strength material, which has a lower adhesion relative to the composite matrix material, may be included in the rod barrel sheet to create one or more additional failure planes. For example, one or more paper layers or dry fibers may be included to create a weak shear plane between two or more composite layers in the barrel. Materials that are not strongly bonded to the resin of the composite layer may also be used to accomplish the reduction in shear strength. Examples of such materials include polypropylene, polyethylene terephthalate, olefins, polyoxymethylenesNylon, polyvinyl chloride, and the like. The inclusion of one or more of these low shear strength materials reduces the interlaminar shear strength between the composite layers in the barrel, thereby creating one or more additional failure planes.

In another embodiment, foreign matter or contaminants may be used to reduce the interlaminar shear strength between adjacent composite layers in the barrel. Sufficient talc, platelets, silica, thermoplastic particles, dust, etc. may be located between adjacent composite layers to reduce the bond strength between the layers, thereby creating one or more additional failure planes in the barrel. One skilled in the art will appreciate that the amount of foreign material required to create a failure plane may vary depending on how much of the material selected reduces the interlaminar shear strength of the sheet substrate. In one embodiment, an amount of foreign matter or contaminants sufficient to reduce the bond area between adjacent composite layers by at least about 30% may be used to create a failure plane between the composite layers.

In another embodiment, the barrel shell may be pre-formed and then over-molded with the sheet, typically using a resin transfer molding process. The layers bonded to the preformed shell typically have a weaker bond than the co-cured sheets. Those skilled in the art will appreciate that such reduced interlaminar shear strength may be used to force failure when used in conjunction with failure planes in surrounding shells or other locations within a preformed outer shell.

The ball bat described herein may be designed to perform at or very close to established regulatory limits, as a multi-plane failure in the barrel wall can result in a rapid degradation of barrel performance (without a transient increase in performance). In contrast, many existing bats must initially perform well below regulatory limits because failures in these bats often result in transient enhancements in barrel performance.

The various embodiments described herein also provide great design flexibility. For example, in a double-walled bat, one or more additional failure planes may be included in the outer barrel wall or the inner barrel wall or both. Furthermore, the various embodiments described are optionally used in combination with one another. For example, the ball bat may include a first additional failure plane created by extreme fiber angle variations between adjacent composite plies, and a second additional failure plane created by a perforated partial barrier layer. The total number of failure planes provided within a given spar cap wall may also be varied. Thus, by including various failure planes in the barrel of a bat, one skilled in the art will be able to adjust the performance of a composite bat to meet those criteria, as barrel performance criteria change over time.

Thus, the preferred fiber angles, percentage of perforations, etc. described herein may be adjusted according to given bat design goals and overall bat structure. For example, in a given bat, the particular materials used, the thickness of the composite layers, the amount of deflection dictated by the intended test or where the bat was scheduled to fail (e.g., 0.10 inch or 0.20 inch deflection), the number and location of failure planes provided, etc., may determine the values that are adjusted. Those skilled in the art will understand how to adjust the design of the bat in view of these variations.

While several embodiments have been shown and described, various changes and substitutions may of course be made, without departing from the spirit and scope of the invention. Accordingly, the invention should not be limited, except as by the following claims and their equivalents.

Claims (19)

1. A ball bat, comprising:

a barrel comprising a plurality of composite layers, wherein the barrel comprises an outer surface and an inner surface such that a neutral axis defining a primary failure plane is located between the inner surface and the outer surface;

a first additional fault plane located between said outer surface and said neutral axis of said barrel;

a second additional fault plane located between said inner surface and said neutral axis of said barrel; and

a handle connected to or integrally formed with the barrel;

wherein at least one of the first and second additional failure planes is created by a perforated barrier layer.

2. The ball bat of claim 1 wherein the first additional failure plane is located at one-quarter of the barrel radial thickness and the second additional failure plane is located at three-quarters of the barrel radial thickness.

3. The ball bat of claim 1 wherein at least one of the first and second additional failure planes is created by an extreme change in fiber angle of adjacent composite plies.

4. The ball bat of claim 3 wherein the fiber angles of the respective adjacent composite plies differ by 60 degrees.

5. The ball bat of claim 4 wherein a first layer of the adjacent composite layers comprises glass fibers and a second layer of the adjacent composite layers comprises carbon fibers.

6. The ball bat of claim 1 wherein the perforated barrier layer includes perforations or openings between 25% and 85% of the surface area, wherein the composite layers on either side of the perforated barrier layer are bonded to each other through the perforations or openings.

7. The ball bat of claim 1 wherein a low shear strength material is used to create at least one of the first additional failure plane and the second additional failure plane.

8. The ball bat of claim 1 wherein at least one of the first and second additional failure planes is created by foreign matter or contaminants located between adjacent composite layers in the barrel.

9. The ball bat of claim 8 wherein the foreign layers or contaminants are reduced by at least 30% of the bond area between adjacent composite layers.

10. The ball bat of claim 1 wherein the barrel includes at least one preformed shell, and wherein at least one of the first additional failure plane and the second additional failure plane is created by combining a composite layer with the preformed shell.

11. The ball bat of claim 1 wherein the barrel includes a radially outer wall and a radially inner wall, and wherein the first and second additional failure planes are located within the radially outer wall.

12. A ball bat including a handle attached to or integrally formed with a composite barrel, the barrel comprising:

an outer surface;

an inner surface such that a neutral axis is defined between the outer surface and the inner surface;

a first composite layer located between the outer surface and the inner surface, the first composite layer including fibers oriented at a first angle relative to a longitudinal axis of the ball bat;

a second composite layer located between the outer surface and the inner surface, wherein the second composite layer is bonded to the first composite layer, the second composite layer including fibers oriented at a second angle relative to the longitudinal axis of the ball bat, wherein the second angle differs from the first angle by at least 45 degrees;

a third composite layer located between the outer surface and the neutral axis, the third composite layer including fibers oriented at a third angle relative to the longitudinal axis of the ball bat;

a fourth composite layer located between the inner surface and the neutral axis, wherein the fourth composite layer is bonded to the third composite layer, the fourth composite layer including fibers oriented at a fourth angle relative to the longitudinal axis of the ball bat, wherein the fourth angle differs from the third angle by at least 45 degrees;

wherein delamination occurs substantially simultaneously between the first and second composite layers, and between the third and fourth composite layers when the barrel is subjected to a failure-induced deflection.

13. The ball bat of claim 12 wherein the first angle is equal to the third angle and the second angle is equal to the fourth angle.

14. The ball bat of claim 13 wherein the first and third angles are 60 degrees and the second and fourth angles are 0 degrees.

15. The ball bat of claim 14 wherein the first and third composite layers comprise glass fibers and the second and fourth composite layers comprise carbon fibers.

16. The ball bat of claim 15 further comprising a composite layer located at or near the neutral axis, the composite layer including carbon fibers oriented at an angle of 0 degrees with respect to the longitudinal axis of the ball bat.

17. A ball bat, comprising:

a barrel comprising a plurality of composite layers, wherein the barrel comprises an outer surface and an inner surface such that a neutral axis is defined between the inner surface and the outer surface;

a first partial barrier layer between a first pair of composite layers, wherein the first pair of composite layers is between the outer surface and the neutral axis of the barrel;

a second partial barrier layer between a second pair of composite layers, wherein the second pair of composite layers is between the inner surface and the neutral axis of the barrel;

a handle attached to or integrally formed with the barrel;

wherein at least one of the first and second partial barrier layers comprises perforations or openings between 25% and 85% of the surface area, wherein the composite layers located on either side of the perforated barrier layer are bonded to each other through the perforations or openings.

18. A ball bat, comprising:

a barrel comprising at least one wall comprising a plurality of composite layers;

a handle attached to or integrally formed with the barrel; and

means for causing substantially simultaneous delamination of adjacent composite layers at a plurality of radial locations in the barrel wall when the barrel is subject to failure-induced deflection.

19. A ball bat, comprising:

a barrel comprising a plurality of composite layers, wherein the barrel comprises an outer surface and an inner surface such that a neutral axis defining a primary failure plane is located between the inner surface and the outer surface;

an additional fault plane located between the outer surface and the neutral axis of the barrel or between the outer surface and the neutral axis of the barrel; and

a handle attached to or integrally formed with the barrel;

wherein when the barrel is subject to a fault-induced deflection, the barrel fails at the primary failure face and at the additional failure face substantially simultaneously.