Patent Publication Number: US-9901135-B2

Title: Footwear with flexible auxetic ground engaging members

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is related to co-pending U.S. patent application Ser. No. 14/565,143, filed Dec. 9, 2014, titled “Footwear with Auxetic Ground Engaging Members,” the entirety of which is herein incorporated by reference. This application is also related to co-pending U.S. patent application Ser. No. 14/564,797, filed Dec. 9, 2014, titled “Footwear With Flexible Auxetic Sole Structure,” the entirety of which is herein incorporated by reference. 
     BACKGROUND 
     The present embodiments relate generally to a sole structure for an article of footwear and, more particularly, to an article of footwear with ground engaging members. It is advantageous, when participating in various activities, to have footwear that provides traction and stability on the surface upon which the activities take place. Accordingly, sole structures for articles of footwear have been developed with traction systems that include ground engaging members to provide traction on a variety of surfaces. Examples include cleated shoes developed for outdoor sports, such as soccer, football, and baseball. In some cases, the shape and orientation of ground engaging members on a sole structure may be configured particularly for forward and rearward traction. 
     SUMMARY 
     In one aspect, the present disclosure is directed to a sole structure for an article of footwear, the sole structure comprising an outer member with a base portion, and a ground engaging member extending away from the base portion. The ground engaging member has a plurality of faces extending from the base portion on an outer side of the outer member, and each of the plurality of faces are joined at an apex of the ground engaging member. The ground engaging member also has a hollow interior region that is bounded by the plurality of faces on the outer side, and the hollow interior region is open on an inner side of the outer member. The base portion has a first thickness and the apex portion of the ground engaging member has a second thickness, and the first thickness is substantially different than the second thickness. 
     In another aspect, the present disclosure is directed to a sole structure for an article of footwear, the sole structure comprising an outer member with a base portion and a ground engaging member extending away from the base portion. The ground engaging member has a plurality of faces extending from a base portion, and each of the plurality of faces are joined at an apex of the ground engaging member. The apex has an outer apex surface disposed on an outer surface of the outer member and the apex has an inner apex surface disposed on an inner surface of the outer member. The outer apex surface is associated with a first curvature and the inner apex surface is associated with a second curvature. In addition, the first curvature is substantially greater than the second curvature. 
     In another aspect, the present disclosure is directed to a sole structure for an article of footwear, the sole structure comprising an outer member and a plurality of ground engaging members extending away from a base portion of the outer member. The plurality of ground engaging members include a ground engaging member. The ground engaging member has at least a first arm portion, and the first arm portion has a first face and a second face. The first face and the second face are joined along a first hinge portion. In addition, the first face is attached to the outer member along a second hinge portion, and the second face attached to the outer member along a third hinge portion. A free end of the ground engaging member is an apex, and the apex is rounded. An end of the first face is associated with the apex, and an end of the second face is associated with the apex. The first face includes a first intermediate portion extending between the apex and the base portion and the second face includes a second intermediate portion extending between the apex and the base portion. The apex is thicker than the first intermediate portion and the apex is also thicker than the second intermediate portion. The ground engaging member has a first configuration and a second configuration, where the apex has a first height with respect to the base portion in the first configuration, and the apex has a second height with respect to the base portion in the second configuration. The first hinge portion, the second hinge portion, and the third hinge portion facilitate the transition of the ground engaging member between the first configuration and the second configuration. The plurality of ground engaging members are arranged on the outer member to provide the sole structure with the auxetic structure. 
     Other systems, methods, features and advantages of the embodiment will be, or will become, apparent to one of ordinary skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description and this summary, be within the scope of the embodiment, and be protected by the following claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The embodiment can be better understood with reference to the following drawings and description. The drawings are schematic and, therefore, the components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the embodiment. Moreover, in the figures, like reference numerals designate corresponding parts throughout the different views. 
         FIG. 1  is an exploded isometric view of an embodiment of an article of footwear having an outer member with ground engaging members; 
         FIG. 2  is an illustration of the outer surface of an embodiment of an outer member for an article of footwear; 
         FIG. 3  is an isometric illustration of the inner surface of an embodiment of an outer member for an article of footwear; 
         FIG. 4  is an isometric view of the inner surface of an embodiment of a portion of the outer member; 
         FIG. 5  is a schematic illustration of the inner surface of an embodiment of a portion of the outer member; 
         FIG. 6  is an isometric view of the outer surface of an embodiment of a portion of the outer member; 
         FIG. 7  is an isometric view of the outer surface of an embodiment of a portion of the outer member; 
         FIG. 8  is an isometric view of the outer surface of an embodiment of a portion of the outer member; 
         FIG. 9  is a schematic cross-section illustration of an embodiment of the ground engaging outer member shown in  FIG. 3 ; 
         FIG. 10  is an isometric view of the outer surface of an embodiment of an outer member with ground engaging members for an article of footwear; 
         FIG. 11  is an isometric view of the outer surface of an embodiment of an outer member with ground engaging members for an article of footwear undergoing compression forces; 
         FIG. 12  is a front view of the outer surface of an embodiment of an outer member with ground engaging members for an article of footwear; 
         FIG. 13  is a front view of the outer surface of an embodiment of an outer member with ground engaging members for an article of footwear undergoing compression forces; 
         FIG. 14  is a side view of an embodiment of an article of footwear with an outer member; 
         FIG. 15  is a schematic illustration of the outer surface of an embodiment of an outer member with ground engaging members for an article of footwear; 
         FIG. 16  is a schematic illustration of the outer surface of an embodiment of an outer member with ground engaging members for an article of footwear; 
         FIG. 17  is an illustration of the outer surface of an embodiment of an outer member for an article of footwear; 
         FIG. 18  is an illustration of a region of an embodiment of an outer member for an article of footwear; 
         FIG. 19  is a side view of an embodiment of a ground engaging member; 
         FIG. 20  is a side view of an embodiment of a ground engaging member; and 
         FIG. 21  is a side view of an embodiment of a ground engaging member. 
     
    
    
     DETAILED DESCRIPTION 
     The following discussion and accompanying figures disclose a sole structure for an article of footwear. Concepts associated with the footwear disclosed herein may be applied to a variety of athletic footwear types, including soccer shoes, baseball shoes, football shoes, and golf shoes, for example. Accordingly, the concepts disclosed herein apply to a wide variety of footwear types. 
     For consistency and convenience, directional adjectives are employed throughout this detailed description corresponding to the illustrated embodiments. The term “longitudinal,” as used throughout this detailed description and in the claims, refers to a direction extending a length of a sole structure, i.e., extending from a forefoot portion to a heel portion of the sole. The term “longitudinal axis,” as used throughout this detailed description and in the claims, refers to an axis oriented in a longitudinal direction. 
     The term “forward” is used to refer to the general direction in which the toes of a foot point, and the term “rearward” is used to refer to the opposite direction, i.e., the direction in which the heel of the foot is facing. 
     The term “lateral direction,” as used throughout this detailed description and in the claims, refers to a side-to-side direction extending a width of a sole. In other words, the lateral direction may extend between a medial side and a lateral side of an article of footwear, with the lateral side of the article of footwear being the surface that faces away from the other foot, and the medial side being the surface that faces toward the other foot. The term “lateral axis,” as used throughout this detailed description and in the claims, refers to an axis oriented in a lateral direction. 
     The term “horizontal,” as used throughout this detailed description and in the claims, refers to any direction substantially parallel with the longitudinal direction, the lateral direction, and all directions in between. In cases where an article is planted on the ground, a horizontal direction may be parallel with the ground. Similarly, the term “side,” as used in this specification and in the claims, refers to any portion of a component facing generally in a lateral, medial, forward, and/or rearward direction, as opposed to an upward or downward direction. 
     The term “vertical,” as used throughout this detailed description and in the claims, refers to a direction generally perpendicular to both the lateral and longitudinal directions, along a vertical axis. For example, in cases where a sole is planted flat on a ground surface, the vertical direction may extend from the ground surface upward. It will be understood that each of these directional adjectives may be applied to individual components of a sole. Furthermore, the term “outer surface,” or “outer side” as used throughout this detailed description and in the claims, refers to the surface of a component that would be facing away from the foot when worn by a wearer. “Inner surface,” or “inner side” as used throughout this detailed description and in the claims, refers to the surface of a component that is facing inward, or the surface that faces toward the foot when worn by a wearer. 
     For purposes of this disclosure, the foregoing directional terms, when used in reference to an article of footwear, shall refer to the article of footwear when sitting in an upright position, with the sole facing groundward, that is, as it would be positioned when worn by a wearer standing on a substantially level surface. 
     In addition, for purposes of this disclosure, the term “permanently attached” shall refer to two components joined in a manner such that the components may not be readily separated (for example, without destroying one or both of the components). Exemplary modalities of fixed attachment may include joining with permanent adhesive, rivets, stitches, nails, staples, welding or other thermal bonding, and/or other joining techniques. In addition, two components may be permanently attached by virtue of being integrally formed, for example, in a molding process. 
       FIG. 1  depicts an exploded view of an embodiment of an article of footwear (“article”)  100 , which may include a sole structure  102  and an upper  108  configured to receive a foot. Sole structure  102  may be permanently attached to a bottom portion of upper  108 . As shown in  FIG. 1  for reference purposes, article  100  may be divided into three general regions, including a forefoot region  110 , a midfoot region  112 , and a heel region  114 . Forefoot region  110  generally includes portions of article  100  corresponding with the toes and the joints connecting the metatarsals with the phalanges. Midfoot region  112  generally includes portions of article  100  corresponding with an arch area of the foot. Heel region  114  generally corresponds with rear portions of the foot, including the calcaneus bone. Forefoot region  110 , midfoot region  112 , and heel region  114  are not intended to demarcate precise areas of article  100 . Rather, forefoot region  110 , midfoot region  112 , and heel region  114  are intended to represent general relative areas of article  100  to aid in the following discussion. 
     The accompanying figures depict various embodiments of article  100 , having sole structures  102  suited for multi-directional traction on natural and/or synthetic turf. Article  100 , as depicted, may be suited for a variety of activities on natural and/or synthetic turf, such as agility/speed training and competition, as well as other sports, such as baseball, soccer, American football, and other such activities where traction and grip may be significantly enhanced by cleat members. In addition, various features of the disclosed sole structures  102  (and/or variations of such features) may be implemented in a variety of other types of footwear. 
     As sole structure  102  and upper  108  both span substantially the entire length of article  100  along a longitudinal direction  104 , the terms forefoot region  110 , midfoot region  112 , and heel region  114  apply not only to article  100  in general, but also to sole structure  102  and upper  108 , as well as the individual elements of sole structure  102  and upper  108 . 
     In different embodiments, upper  108  may include one or more material elements (for example, textiles, foam, leather, and synthetic leather), which may be stitched, adhesively bonded, molded, or otherwise formed to define an interior void configured to receive a foot. The material elements may be selected and arranged to selectively impart properties such as durability, air-permeability, wear-resistance, flexibility, and comfort. Upper  108  may alternatively implement any of a variety of other configurations, materials, and/or closure mechanisms. 
     In different embodiments, sole structure  102  may have a configuration that extends between a bottom surface of upper  108  and the ground in a vertical direction  106  and may be secured to upper  108  in any suitable manner. For example, sole structure  102  may be secured to upper  108  by adhesive attachment, stitching, welding, or any other suitable method. Sole structure  102  may include provisions for attenuating ground reaction forces (that is, cushioning and stabilizing the foot during vertical and horizontal loading) in some embodiments. In addition, sole structure  102  may be configured to provide traction, impart stability, and/or limit various foot motions, such as pronation, supination, and/or other motions. 
     In different embodiments, the configuration of sole structure  102  may vary significantly according to one or more types of ground surfaces on which sole structure  102  may be used. For example, the disclosed concepts may be applicable to footwear configured for use on indoor surfaces and/or outdoor surfaces. The configuration of sole structure  102  may vary based on the properties and conditions of the surfaces on which article  100  is anticipated to be used. For example, sole structure  102  may vary depending on whether the surface is harder or softer. In addition, sole structure  102  may be tailored for use in wet or dry conditions. 
     Sole structure  102  may include multiple components in some embodiments, which may individually and/or collectively provide article  100  with a number of attributes, such as support, rigidity, flexibility, stability, cushioning, comfort, reduced weight, traction, and/or other attributes. For example, in some embodiments, sole structure  102  may incorporate incompressible plates, moderators, and/or other elements that attenuate forces, influence the motions of the foot, and/or impart stability, for example. Further, while various types of cleated article  100  may be provided without a midsole, in some embodiments, sole structure  102  may also include a midsole  118  or another sole layer disposed between an outer member  116  and upper  108 . In some embodiments, an additional sole layer disposed between outer member  116  and upper  108  may include cushioning members, reinforcing structures, support structures, or other features. In another embodiment, midsole  118  may include a recess to hold outer member  116 . In other embodiments, midsole  118  may not be included in sole structure  102  and/or outer member  116  may be joined directly to upper  108 . 
     Article of footwear  100  according to the present disclosure may include a sole structure  102  with outer member  116 . In different embodiments, outer member  116  may include features that provide traction and stability on any of a variety of surfaces, and in any of a variety of conditions. In some embodiments, outer member  116  may include a base portion  120  along its outer side  299  that is joined to one or more ground engaging members  122 . In some embodiments, ground engaging members  122  extend away from base portion  120  of outer member  116 . In one embodiment, ground engaging members  122  may be permanently attached to the base portion  120  of outer member  116 . In other embodiments, ground engaging member  122  may be attached in non-permanent manner. In some embodiments, ground engaging members  122  may be cleats or structures substantially similar to cleats. In other embodiments, ground engaging members  122  may be convex portions, or convex members. Some embodiments of such structures are discussed in greater detail below. 
     In different embodiments, outer member  116  may include a substantially flat or plate-like element that supports the foot, and serves as a platform from which ground engaging members  122  may extend. In some embodiments, outer member  116 , although relatively flat, may include various anatomical contours, such as a relatively rounded longitudinal profile, a heel portion that is higher than the forefoot portion, a higher arch support region, and other anatomical features. 
     Embodiments of ground engaging members  122  may have one or more features that provide increased traction, directional traction, ground penetration, and/or ground extraction. Such features may include, for example, shapes, sizes, positioning on the outer member, as well as the orientation of ground engaging members  122 . 
       FIG. 2  is a view of the bottom surface of an embodiment of sole structure  102 .  FIG. 2  depicts the outer surface of sole structure  102 , comprising outer member  116 , and ground engaging members  122 . An enlarged view of a first ground engaging member  200  is included for purposes of illustration. 
     In the embodiment shown in  FIG. 2 , ground engaging members  122  and other portions of outer member  116  may be configured in a geometric pattern that provides an auxetic structure to at least some portions of sole structure  102 . As will be described in greater detail below with respect to  FIGS. 3-12 , sole structure  102  may include an auxetic structure that, when placed under tension in a first direction, can increase in size both in the first direction and in the direction in the plane of the structure that is orthogonal to the first direction. In some embodiments, outer member  116  may be at least partially an auxetic structure. A structure that deforms due to its auxetic properties may be said to undergo an auxetic action. 
     As used herein, the terms “auxetic” generally refers to materials that have a negative Poisson&#39;s ratio, such that when they are under tension in a first direction, their dimensions increase both in the first direction and in a direction orthogonal the first direction. Articles of footwear having soles with an auxetic structure are described in Cross, U.S. patent application Ser. No. 14/030,002, filed Sep. 18, 2013 and titled “Auxetic Structures and Footwear with Soles Having Auxetic Structures”, which is incorporated by reference above. In some cases, the term “reactive structure” may also be used to describe an auxetic structure. For example, if the structure can be described as having a length, a width and a thickness, then when the structure is under tension longitudinally, the structure increases in width. In some embodiments, the auxetic structures are bi-directionally auxetic such that they increase in length and width when stretched longitudinally and in width and length when stretched laterally, but do not increase in thickness. Also, although such auxetic structures will generally have at least a monotonic relationship between the applied tension and the increase in the dimension orthogonal to the direction of the tension, that relationship need not be proportional or linear, and in general need only increase in response to increased tension. Thus, in one embodiment, outer member  116  can expand in a first direction and a second direction when outer member  116  is tensioned in the first direction, where the second direction is substantially perpendicular to the first direction. 
     In different embodiments, ground engaging members  122  may be used to form auxetic structures in sole structure  102 . In some embodiments, ground engaging members  122  may comprise portions that can project outwardly from the base of a sole structure. In different embodiments, portions may be any shape, size, or geometry. For example, in some embodiments, sole structure  102  or portions of soles structure  102  may incorporate any of the structures disclosed in Nordstrom, U.S. Patent Publication Number 2014/0053311, published Feb. 27, 2014 (now U.S. patent application Ser. No. 14/011,201, filed Aug. 27, 2013) and titled “Dynamic Materials Integrated Into Articles for Adjustable Physical Dimensional Characteristics,” which is incorporated by reference in its entirety herein. In some embodiments, various polygonal features or portions may be used to form the auxetic structures, such as triangular, quadrilateral, pentagonal, hexagonal, heptagonal or octagonal features. In other embodiments, portions may be polygonal features used to form three-pointed star-shaped projections, four-pointed star-shaped projections, five-pointed star-shaped projections, or six-pointed star-shaped projections. In the embodiment of  FIG. 2 , the portions are depicted as ground engaging members  122  that include generally triangular features forming three-pointed star-shaped pyramidal structures or projections. In one embodiment, ground engaging members may have the approximate geometry of a pyramid with a tri-star base. 
     Thus, in different embodiments, ground engaging members  122  may be configured in varying geometric patterns. In some embodiments, ground engaging members  122  may include convex features. In other embodiments, ground engaging members  122  may include various hinges or predetermined regions of bending. In one embodiment, when ground engaging members  122  are vertically compressed they can unfold and extend in a horizontal direction. In some embodiments, there may be multiple ground engaging members  122  arranged on sole structure  102 , and in one embodiment, ground engaging members  122  may function together to provide auxetic structure to sole structure  102 . For example, in one embodiment, as shown with respect to first ground engaging member  200  in  FIG. 2 , one or more of ground engaging members  122  may have a substantially three-pointed star cross-sectional shape in a substantially horizontal plane. In some embodiments, one or more ground engaging members  122  may have a substantially three-pointed star cross-sectional shape over substantially the entire height of ground engaging member  122 . Accordingly, first ground engaging member  200  may extend from a region of outer member  116  in a substantially three-pointed star shape to a central tip  202  located around an apex  204  of first ground engaging member  200 . Central tip  202  may be curved or rounded in some embodiments. Apex  204  may represent the point on first ground engaging member  200  farthest from outer member  116 . 
     In different embodiments, ground engaging members  122  may include one or more arm portions  206 . In some embodiments, arm portions  206  may extend substantially radially from a central region  208 , as shown with respect to first ground engaging member  200 . In some embodiments, one or more arm portions  206  may extend in a substantially non-radial direction from central region  208 . In other embodiments, all arm portions  206  of a single ground engaging member may extend radially from central region  208  of the ground engaging member. 
     In some embodiments, central region  208  may include different shapes. In the embodiment of  FIG. 2 , central region  208  includes a triangular shape in the horizontal plane. In other embodiments, central region  208  may include a circular, square, or other polygonal shape. Central region  208  and central tip  202  are not intended to demarcate a precise area of the ground engaging member. Rather, they are intended to represent general relative areas of the ground engaging member to aid in the following discussion. 
     In some embodiments, a majority of ground engaging members  122  may each include three arm portions  206 , extending outward in a radial direction. For example, in  FIG. 2 , first ground engaging member  200  shown in the enlarged view includes a first arm portion  210 , a second arm portion  212 , and a third arm portion  214 . Each arm portion begins near central region  208  and terminates at a vertex  216 . A midline on each arm portion may be seen that moves from apex  204  to each vertex  216 . First arm portion  210  includes a first midline  218 , second arm portion  212  includes a second midline  220 , and third arm portion  214  includes a third midline  222 . 
     In different embodiments, arm portions  206  may have various shapes. In some embodiments, arm portions  206  may include a generally oblong triangular shape. In other embodiments, vertices  216  may include an intersection of edges that is more pointed, or less pointed, than that depicted in  FIG. 2 . In other words, edge of vertex  216  may be more rounded or curved, or may be more narrow or sharp. Furthermore, arm portions  206  may be non-linear in some embodiments. For example, in some embodiments, arm portions  206  may extend outward from central region  208  and include a curved geometry. In different embodiments, first arm portion  210 , second arm portion  212 , and third arm portion  214  of first ground engaging member  200  may be shaped similarly to one another, or they may each have different shapes. 
     In different embodiments, the width of an arm portion  206  in the horizontal plane may vary from central region  208  to vertex  216 . In some embodiments, there can be a first width  221  that is closer to central region  208 , and a second width  223  that is closer to vertex  216 . In some embodiments, first width  221  is larger than second width  223 . In other embodiments, first width  221  may be substantially equivalent to second width  223 , or may be smaller. 
     In some embodiments, the geometry of ground engaging members  122  can generally demarcate outer surface of outer member  116  into smaller areas. As seen in  FIG. 2 , outer member  116  includes a regular pattern of outer member areas  272  that lie between or adjacent to arm portions  206  of adjacent ground engaging members  122 . In some embodiments, outer member areas  272  may be generally triangular. In other embodiments, outer member  116  may be demarcated in a different arrangement or geometrical pattern and provide outer member areas  272  of different shape or size. In some embodiments, outer member areas  272  may be curved or otherwise irregular, rather than linearly shaped. In other embodiments, the appearance of outer member areas  272  may be related to the shape, size, and arrangement of ground engaging members  122  included. 
     In some embodiments, different areas of a ground engaging member may function as a hinge, permitting the turning or movement of adjacent parts. In particular, in some embodiments, edges connecting adjacent portions of material may rotate about a hinge portion  283  associated with the edge of the ground engaging member. In different embodiments, ground engaging members  122  may include one or more hinge portions  283 . In some embodiments, each arm portion  206  of ground engaging members  122  may include one or more hinge portions  283 . Hinge portions  283  may at least in part provide sole structure  102  with the auxetic properties described in this description. In other words, ground engaging members  122  may be able to move about the regions associated with hinge portions  283  in some embodiments. In some embodiments, at least some of hinge portions  283  may be rounded with a convex geometry. 
     In one example, each edge of ground engaging member  200  can be associated with a corresponding hinge portion  283 . In  FIG. 2 , it can be seen that first ground engaging member  200  includes twelve hinge portions. First arm portion  210  includes a first hinge portion  284  and a second hinge portion  285 . Second arm portion  212  includes a third hinge portion  286  and a fourth hinge portion  287 . Third arm portion  214  includes a fifth hinge portion  288  and a sixth hinge portion  289 . Furthermore, first midline  218  of first arm portion  210  may be associated with a seventh hinge portion, second midline  220  of second arm portion  212  may be associated with an eighth hinge portion, and third midline  222  of third arm portion  214  may be associated with a ninth hinge portion. In addition, first arm portion  210  of first ground engaging member  200  may be disposed adjacent to and joined along a tenth hinge portion  233  to neighboring second arm portion  212 . Likewise, second arm portion  212  may be joined along an eleventh hinge portion  235  to adjacent third arm portion  214 . Third arm portion  214  may also be joined along a twelfth hinge portion  237  to first arm portion  210 . In other embodiments, arm portions  206  may include a lesser or greater number of hinge portions  283 . 
     In some embodiments, each of the remaining edges and/or midlines of ground engaging members  122  may be associated with hinged areas or hinge portions that join adjacent polygonal portions in a rotatable manner. The characteristics of hinge portions  283  may be related to the type of shape or geometry selected for ground engaging members  122 . In other embodiments, ground engaging members  122  may not include hinge portions  283 . 
     In different embodiments, hinge portions  283  can be associated with and/or comprised of a relatively small portion of material adjoining or connecting various faces, or sides, of the various polygonal or irregular portions forming the auxetic structure. In some embodiments, ground engaging members  122  include a plurality of faces. In one embodiment, the faces associated with ground engaging members  122  are substantially flat. 
     Hinge portions  283  may also provide a connecting portion between arm portions  206  and a portion of outer member  116 , such as outer member areas  272 . In other words, some hinge portions  283  may provide a region of attachment for the various faces or portions comprising ground engaging members  122  to sole structure  102  and/or outer member  116 . 
     In some embodiments, ground engaging members  122  may include six faces. For example, in  FIG. 2 , a first face  290  and a second face  291  forming two sides or portions of first arm portion  210  are depicted. First face  290  and second face  291  may be joined, rotated or bent with respect to one another along the seventh hinge portion associated with first midline  218 . First face  290  may also be joined, moved, rotated, or bent along first hinge portion  284  with respect to a first outer member area  296  of sole structure  102 , and second face  291  may be connected, moved, rotated, or bent along second hinge portion  285 , with respect to a second outer member area  297  of sole structure  102 . In a similar manner, a third face  292  and a fourth face  293  form two sides or portions of second arm portion  212 . Third face  292  and fourth face  293  may join, rotate or bend with respect to one another along the eighth hinge portion associated with second midline  220 . Third face  292  may also be joined, moved, rotated or bent along third hinge portion  286  with respect to second outer member area  297 , and fourth face  293  may be connected, moved, rotated, or bent along fourth hinge portion  287  with respect to a third outer member area  298 . In addition, third arm portion  214  may be comprised of two sides, including a fifth face  294  and a sixth face  295 . Fifth face  294  and sixth face  295  may join, rotate or bend with respect to one another at the ninth hinge portion associated with third midline  222 . Fifth face  294  may be connected, moved, rotated, or bent along fifth hinge portion  288  with respect to third outer member area  298 , and sixth face  295  may be joined, moved, rotated, or bent along sixth hinge portion  289  with respect to first outer member area  296 . 
     As seen in  FIG. 2 , a portion, or one end, of each face may also be associated with an apex  204 . Thus, in one embodiment, each face may extend from base portion  120  to apex  204 . In other embodiments, each face may be joined to two adjacent faces. 
     In some embodiments, two adjacent arm portions  206  may form various angles. In the embodiment of  FIG. 2 , the three arm portions associated with first ground engaging member  200  form three angles, identified as angle  224 , angle  225 , and angle  226 . First arm portion  210 , second arm portion  212 , and third arm portion  214  are disposed so that each pair of adjacent arm portions form substantially equivalent obtuse angles. In other embodiments, the angles formed by a pair of adjacent arm portions may differ from one another. In some embodiments, any angles formed by a pair of adjacent arm portions may be acute or right angled. It should be noted that the magnitudes of angle  224 , angle  225 , and angle  226  may increase or decrease as the auxetic structure of sole structure  102  undergoes expansion or compression. In particular, as tenth hinge portion  233 , eleventh hinge portion  235 , and/or twelfth hinge portion  237  permit movement of various regions of first ground engaging member  200 , corresponding angle  224 , angle  225 , and angle  226  can change. 
     In different embodiments, the orientation of one or more arm portions  206  may differ significantly, or may be substantially similar. In the embodiment of  FIG. 2 , first arm portion  210 , second arm portion  212 , and third arm portion  214  are each oriented along a different direction. In other words, each midline of first arm portion  210 , second arm portion  212 , and third arm portion  214  is oriented along a different axis. In some embodiments, first midline  218  may be oriented along a first direction  230 , second midline  220  may be oriented along a second direction  232 , and third midline  222  may be oriented along a third direction  234 . As seen in  FIG. 2 , first direction  230  and third direction  234  are oriented so that they extend diagonally relative to a lateral direction  236 , extending from a medial side  238  to a lateral side  240  of sole structure  102 . Second direction  232  is oriented so that it extends approximately from forefoot region  110  to heel region  114  of sole structure  102 . 
     In different embodiments, the orientation of adjacent ground engaging members  122  may vary or be substantially similar to the orientation of first ground engaging member  200 . In other words, the midlines of arm portions  206  of ground engaging members  122  may lie along or near substantially the same axis as the respective midlines of the three arm portions of first ground engaging member  200  in some embodiments. For example, in  FIG. 2 , ground engaging members adjacent to first ground engaging member  200  include second ground engaging member  242 , third ground engaging member  244 , fourth ground engaging member  246 , fifth ground engaging member  248 , sixth ground engaging member  250 , and seventh ground engaging member  252 . The midlines of a first arm portion  254  of second ground engaging member  242 , first arm portion  210  of first ground engaging member  200 , and a first arm portion  256  of third ground engaging member  244  may generally lie along first direction  230 . The midlines of a second arm portion  258  of fourth ground engaging member  246 , second arm portion  212  of first ground engaging member  200 , and a second arm portion  260  of fifth ground engaging member  248  may generally lie along second direction  232 . The midlines of a third arm portion  262  of sixth ground engaging member  250 , third arm portion  214  of first ground engaging member  200 , and a third arm portion  264  of seventh ground engaging member  252  may lie along third direction  234 . In some embodiments, other ground engaging members  122  may include arm portions  206  that lie along axes that are substantially parallel to first direction  230 , second direction  232 , and third direction  234 . 
     In other embodiments, ground engaging members  122  may be disposed along different orientations or arrangements. It should be noted that in different embodiments, first direction  230 , second direction  232 , third direction  234 , and/or any other axis along which ground engaging members are arranged may be non-linear. In some embodiments, adjacent ground engaging members  122  may lie along an axis that is curved, for example. In other embodiments, ground engaging members  122  may be disposed in a staggered arrangement. 
     Providing all, or substantially all, of ground engaging members  122  so that an arm portion generally lies along first direction  230 , second direction  232 , or third direction  234 , or axes parallel to first direction  230 , second direction  232 , or third direction  234  may maximize the benefits discussed above regarding the characteristics of traction in medial side  238  to lateral side  240  (i.e., side-to-side) directions. Such configurations may provide increased performance in terms of traction supporting agility in lateral direction  236 . 
     In different embodiments, two adjacent ground engaging members  122  may be disposed at various distances from one another. In some embodiments, ground engaging members  122  may be disposed at regular intervals from one another. In other embodiments, there may be greater space, or areas of outer member  116 , between one ground engaging member and another ground engaging member. In the embodiment of  FIG. 2 , first ground engaging member  200  and sixth ground engaging member  250  are adjacent to one another so that third arm portion  262  of sixth ground engaging member  250  generally abuts the area near central region  208  of first ground engaging member  200  within the obtuse angle formed by second arm portion  212  and third arm portion  214  of first ground engaging member  200 . Other ground engaging members  122  may be disposed in a similar arrangement adjacent to areas of outer member  116 . In one embodiment, ground engaging members  122  that generally lie along a single axis may be disposed so that they are at substantially the same distance from one another. For example, in  FIG. 2 , a first distance  227  from a first apex  266  to a second apex  268  may be substantially similar to a second distance  228  from second apex  268  to a third apex  270 . In other embodiments, first distance  227  may be less than second distance  228 , or first distance  227  may be greater than second distance  228 . 
     In some embodiments, particularly near a perimeter  274  of sole structure  102 , ground engaging members  122  may be partially formed. In other words, some ground engaging members  122  may be formed with fewer than three arm portions  206 , arm portions  206  that extend for shorter lengths, and/or a central region  208  that is smaller relative to the central regions of other ground engaging members disposed farther from perimeter  274 . For example, in  FIG. 2 , an eighth ground engaging member  276  can be seen disposed along perimeter  274  of heel region  114 . Eighth ground engaging member  276  includes a first arm portion  278  and a second arm portion  280 , similar to arm portions  206  described above. However, a third arm portion  282  of eighth ground engaging member  276  is abbreviated in length relative to first arm portion  278  and second arm portion  280 . Thus, in some embodiments, ground engaging members  122  may be formed along or near perimeter  274  of outer member  116  that differ from ground engaging members  122  that are not formed along perimeter  274 . In some embodiments, at least one arm portion of each ground engaging member disposed along perimeter  274  may be shorter than the arm portions  206  of the ground engaging members disposed further from perimeter  274 . In other embodiments, there may be fewer than three arm portions  206  included for one or more ground engaging members  122  that are disposed along perimeter  274 . In one embodiment, a ground engaging member near perimeter  274  may include only a single arm portion  206 , or a partially formed arm portion. 
     Materials and configurations for outer member  116  and ground engaging members  122  may be selected according to the type of activity for which article  100  is configured. Outer member  116  and/or ground engaging members  122  may be formed of suitable materials for achieving the desired performance attributes. In one embodiment, outer member  116  and ground engaging members  122  may be comprised of substantially similar materials. In different embodiments, for example, outer member  116  and/or ground engaging members  122  may be formed of any suitable polymer, rubber, composite, and/or metal alloy materials. Examples of such materials may include thermoplastic and thermoset polyurethane (TPU), polyester, nylon, glass-filled nylon, polyether block amide, alloys of polyurethane and acrylonitrile butadiene styrene, carbon fiber, poly-paraphenylene terephthalamide (para-aramid fibers, e.g., Kevlar®), titanium alloys, and/or aluminum alloys. In one embodiment, outer member  116  and/or ground engaging members  122  are made of a substantially elastic material. 
     In some embodiments, outer member  116 , or portions of outer member  116  and ground engaging members  122 , may be formed of a composite of two or more materials, such as carbon-fiber and poly-paraphenylene terephthalamide. In some embodiments, these two materials may be disposed in different portions of outer member  116  and/or ground engaging members  122 . Alternatively, or additionally, carbon fibers and poly-paraphenylene terephthalamide fibers may be woven together in the same fabric, which may be laminated to form outer member  116 . Other suitable materials, including future-developed materials, will be recognized by those having skill in the art. 
     Different structural properties may be desired for different aspects of outer member  116  and/or ground engaging members  122 . Therefore, the structural configuration may be determined such that, even though a common material is used for all portions of outer member  116  and/or ground engaging members  122 , the different portions may be stiffer, or more flexible due to different shapes and sizes of the components. In different embodiments, for example, heel region  114  and midfoot region  112  of outer member  116  may be formed of a thicker material and/or may include reinforcing features, such as ribs, in order to provide stiffness to these portions of outer member  116 , whereas forefoot region  110  of outer member  116 , particularly a region of outer member  116  corresponding with the ball of the foot, may be formed of a relatively thin material, in order to provide flexibility to forefoot region  110 . Greater flexibility in forefoot region  110  may enable natural flexion of the foot during running or walking, and may also enable outer member  116  to conform to surface irregularities, which may provide additional traction and stability on such surfaces. In addition, ground engaging members  122  may be formed at least in part with a thicker structure to provide rigidity and strength in some embodiments. 
     In different embodiments, outer member  116  and/or ground engaging members  122  may be formed by any suitable process. For example, in some embodiments, outer member  116  and/or ground engaging members  122  may be formed by molding. In addition, in some embodiments, various elements of outer member  116  and/or ground engaging members  122  may be formed separately and then joined in a subsequent process. Those having ordinary skill in the art will recognize other suitable processes for making outer members  116  and/or ground engaging members  122  discussed in this disclosure. 
     In some embodiments, outer member  116 , ground engaging members  122 , and other elements of outer member  116  may be integrally formed. For example, in some embodiments, the entirety of outer member  116  may be formed of a single material, forming all parts of outer member  116 . In such embodiments, outer member  116  may be formed all at once in a single molding process, for example, with injection molding. 
     In other embodiments, different portions of sole structure  102  may be formed of different materials. For example, a stiffer material, such as carbon fiber, may be utilized in heel region  114  and/or midfoot region  112  of outer member  116 , whereas a more flexible material, such as a thin polyurethane, may be used to form forefoot region  110  of outer member  116 . In addition, it may be desirable to utilize a stiffer and/or harder material for outer member  116  in some embodiments, such as carbon-fiber and/or polyurethane, and softer and more flexible material for ground engaging members  122 , such as a relatively hard rubber. For example, some parts of outer member  116  may be made by molding a hard rubber or polyurethane to form the polygonal features. 
     Accordingly, in some embodiments, outer member  116  and/or ground engaging members  122  may be formed by multiple molding steps, for example, using a co-molding process. For instance, outer member  116  may be pre-molded, and then inserted into an outer member mold, into which the ground engaging member material may be injected to form ground engaging members  122 , or portions of ground engaging members  122 . In other embodiments, ground engaging members  122  may be pre-molded and outer member  116  may be co-molded with the pre-formed ground engaging members. In addition, other components of outer member  116 , such as reinforcing elements, may be formed of different materials. 
     In some embodiments, outer member  116  and ground engaging members  122  may be made separately and then engaged with one another (e.g., by mechanical connectors, by cements or adhesives, etc.). In some embodiments, ground engaging members  122  and other sole components may be integrally formed as a unitary, one piece construction (e.g., by a molding step). In some embodiments, at least some portions of sole structure  102  (e.g., outsole or outer member components) may be affixed to one another or formed together as a unitary, one-piece construction, e.g., by selective laser sintering, stereolithography, or other three dimensional printing or rapid manufacturing additive fabrication techniques. These types of additive fabrication techniques allow the ground engaging members  122 , outer member  116 , and/or other components of sole structure  102  to be built as unitary structures. 
       FIG. 3  illustrates an isometric view of an inner side  320  of an embodiment of outer member  116  for a sole structure. Outer member  116  may include apertures  300  disposed along inner surface or inner side  320  of outer member  116  in some embodiments. In one embodiment, apertures  300  may comprise a hollow interior region that is bounded by the plurality of faces associated with ground engaging members  122  on the outer side of outer member  116 . The hollow interior region can be open on an inner side of outer member  116 . In particular, apertures  300  may correspond to a concave interior side of ground engaging members  122 . Apertures  300  may extend in vertical direction  106  through outer member  116 . 
     In different embodiments, apertures  300  may be configured in varying geometric patterns. In some embodiments, apertures  300  may include concave features. In other embodiments, apertures  300  may include various hinges or predetermined regions of bending. In one embodiment, when apertures  300  are vertically compressed they can unfold and extend in a horizontal direction. In some embodiments, there may be multiple apertures  300  arranged on sole structure  102 , and in one embodiment, apertures  300  may function together to provide auxetic structure to outer member  116 . 
     In some embodiments, apertures  300  may comprise openings in outer member  116 . In different embodiments, apertures  300  may be any shape, size, depth, or geometry. In some embodiments, various polygonal openings or other irregularly shaped openings may be used to form apertures  300 , such as triangular, quadrilateral, pentagonal, hexagonal, heptagonal, octagonal, or other irregular features. In other embodiments, apertures  300  may be polygonal, and may form three-pointed star-shaped openings, four-pointed star-shaped openings, five-pointed star-shaped openings, or six-pointed star-shaped openings. 
     In one example, as shown in  FIG. 3 , inner side  320  of outer member  116  bears a pattern of triangular, or three-pointed, star-shaped apertures  300 , bounded by a pattern of base areas  302 . In different embodiments, base areas  302  may be configured in varying geometric patterns. In some embodiments, base areas  302  may include generally flat or plate-like features. In other embodiments, base areas  302  may include various hinges or predetermined regions of bending for greater flexibility. In other embodiments base areas  302  may be relatively inflexible. In some embodiments, there may be multiple base areas  302  arranged on sole structure  102 , and in one embodiment, base areas  302  may function together to provide auxetic structure to outer member  116 . 
     In some embodiments, base areas  302  may comprise variously shaped portions in outer member  116 . In different embodiments, base areas  302  may be any shape, size, thickness, or geometry. In some embodiments, various polygonal shapes or other irregularly shape portions may comprise base areas  302 , such as round, curved, elliptical, triangular, quadrilateral, pentagonal, hexagonal, heptagonal, octagonal, or other irregular features. In one embodiment, base areas  302  may be generally triangular. 
     In one case, base areas  302  may be separated by apertures  300  so that base areas  302  are completely enclosed and separated from one another. In other cases, base areas  302  are partially enclosed so that some base areas  302  can touch or abut adjacent base areas  302 , as depicted in  FIG. 3 . 
     In different embodiments, apertures  300  may be disposed in various arrangements along outer member  116 . In some embodiments, apertures  300  may be disposed in a uniform pattern along outer member  116 . In other embodiments, apertures  300  may be disposed in only some areas of outer member  116 . 
     In different embodiments, apertures  300  may align or correspond with ground engaging members  122  that are located on the outer side of outer member  116 . In other embodiments, ground engaging members  122  may be disposed on an outer side of outer member  116 , but the opposite side of outer member  116  may be solid, or “filled in,” so that there is no corresponding aperture  300 . In one embodiment, apertures  300  may be present but there may be no corresponding ground engaging member  122 . In another embodiment, there may be ground engaging members  122  and corresponding apertures  300 , but they may differ significantly in size or shape from one another. In the embodiment of  FIG. 3 , apertures  300  generally correspond to ground engaging members  122  disposed on the opposite side of outer member  116 . As seen in forefoot region  110 , and along perimeter  274  of outer member  116 , there is a first aperture  304  which is aligned with a first ground engaging member  312 , a second aperture  306  aligned with a second ground engaging member  314 , a third aperture  308  aligned with a third ground engaging member  316 , and a fourth aperture  310  aligned with a fourth ground engaging member  318 . This type of arrangement may be repeated throughout outer member  116 , or it may differ. Moreover, it may be understood that base areas  302  on inner side  320  may generally correspond with outer member areas  272  on outer side  299  of outer member  116 . 
     In some embodiments, the shape of apertures  300  in the horizontal plane may be substantially similar to the shape of corresponding ground engaging members  122  in the horizontal plane. In other embodiments, some areas of outer member  116  may include apertures  300  and ground engaging members  122  that are similar shapes, and other areas may include apertures  300  and ground engaging members  122  are different shapes. 
     During deformations as described above, ground engaging members  122  may expand or compress in different embodiments in different embodiments.  FIGS. 4-8  depict a cutaway portion of outer member  116 . In  FIGS. 4 and 5 , a first aperture  400  and a second aperture  402  in outer member  116  are depicted, with portions of corresponding first ground engaging member  408  and second ground engaging member  410  visible below outer member  116 . In  FIG. 4 , first aperture  400  has an opening with a first aperture area  404 , and second aperture  402  similarly has an opening with a second aperture area  406 . In some embodiments, the openings lie generally in the horizontal plane along the upper surface of outer member  116 . The area of each opening may be enclosed by the perimeter edges of each aperture. 
     When a compressive force is applied, for example near the perimeter of outer member, the areas of the openings of first aperture  400  and second aperture  402  may change in some embodiments. In  FIG. 5 , a first compressive force  506  and a second compressive force  508  are represented by arrows. As a result of the application of compressive force  506  and compressive force  508 , the areas of first aperture  400  and second aperture  402  have decreased. The opening of first aperture  400  has a third aperture area  500 , and the opening of second aperture  402  has a fourth aperture area  502 . Third aperture area  500  is less than first aperture area  404  and fourth aperture area  502  is less than second aperture area  406 . 
     In some embodiments, the shape of the apertures may also change. Depending on the magnitude and the direction of the force(s) applied, the changes in area or shape may vary. In some embodiments, a different force may permit an expansion of the aperture areas. For example, in one embodiment, the outer member may be exposed to a force whereby third aperture area  500  is greater than first aperture area  404 , and/or fourth aperture area  502  is greater than second aperture area  406 . In one embodiment, the area of an aperture may increase when a compressive force is applied in the vertical direction. 
     Exposure to various forces may also produce a change in the shape or geometry, size, and/or height of ground engaging members. In  FIG. 4 , first ground engaging member  408  has an apex  412  at a first height  414 . In some embodiments, the height of apex  412  lies generally in the vertical plane of the outer member and extends from the bottom side of the outer member toward the ground. For example, when a first force  506  and a second force  508  are applied, the height of first ground engaging member  408  may change. In  FIG. 5 , the height of apex  412  of first ground engaging member  408  is increased to a second height  504 . In the embodiments of  FIGS. 4 and 5 , second height  504  is greater than first height  414 . 
     In other embodiments, second height  504  may be substantially similar to or less than first height  414  as various forces are applied to article of footwear  100 . In some embodiments, the overall geometry of the ground engaging members may also change. Depending on the magnitude and the direction of the force(s) applied, changes in area or shape may vary. In some embodiments, a different force may permit an expansion of the ground engaging member(s). In some cases, this expansion occurs in the horizontal direction. For example, in one embodiment, the outer member may be exposed to a force whereby second height  504  is less than first height  414 . 
     In  FIGS. 6, 7, and 8 , an embodiment of a portion of outer member  116  is shown. The portion of outer member  116  includes a first ground engaging member  600 , a second ground engaging member  602 , a third ground engaging member  610 , a fourth ground engaging member  612 , and a fifth ground engaging member  614 . Dotted lines represent apertures corresponding to the ground engaging members, including, for example, a first aperture  604  corresponding to first ground engaging member  600 , and a second aperture  606  corresponding to second ground engaging member  602 . 
     In  FIG. 6 , first ground engaging member  600  has an apex  412  at a third height  642 , and, as seen in magnified area  608 , second ground engaging member  602  has an apex  412  at a fourth height  644 . In some embodiments, the height of each apex  412  lies generally in the vertical plane of the outer member and extends from the bottom side of outer member toward the ground. 
     When a compressive force is applied, for example near the perimeter of the outer member, the heights of the ground engaging members may change. In  FIG. 7 , a third compressive force  710 , is represented by an arrow. As a result of the application of third compressive force  710 , the heights of first ground engaging member  600 , second ground engaging member  602 , third ground engaging member  610 , fourth ground engaging member  612 , and fifth ground engaging member  614  are decreased relative to the embodiment of  FIG. 6 . For example, first ground engaging member  600  has a fifth height  706 , and, as seen in magnified area  700 , second ground engaging member  602  has a sixth height  708 . In the embodiments of  FIGS. 6 and 7 , fifth height  706  is less than third height  642 , and sixth height  708  is less than fourth height  644 . 
     If a different compressive force is applied, the heights of ground engaging members may further change. In  FIG. 8 , a fourth compressive force  812  is represented by an arrow. Fourth compressive force  812  is greater than third compressive force  710 . As a result of the application of fourth compressive force  812 , the heights of first ground engaging member  600 , second ground engaging member  602 , third ground engaging member  610 , fourth ground engaging member  612 , and fifth ground engaging member  614  are decreased relative to the embodiments of  FIGS. 6 and 7 . For example, first ground engaging member  600  has a seventh height  806 , and, as seen in magnified area  800 , second ground engaging member  602  has an eighth height  808 . In the embodiments of  FIGS. 6, 7, and 8 , fifth height  706  is less than third height  642 , seventh height  806  is less than fifth height  706 , sixth height  708  is less than fourth height  644 , and eighth height  808  is less than sixth height  708 . 
     The change in height, as well as other changes to size and shape of ground engaging members, may be facilitated by hinge portions of each ground engaging member. For example, second ground engaging member  602  can be seen to include a first hinge portion  616 , a second hinge portion  618 , a third hinge portion  620 , a fourth hinge portion  622 , a fifth hinge portion  624 , a sixth hinge portion  626 , and a seventh hinge portion  628 . Moreover, arm portions of second ground engaging member may be connected by hinge portions, for example, an eighth hinge portion  629 . Additional hinge portions may be present along the side of second ground engaging member facing away from the viewer. As various forces are applied to second ground engaging member  602 , each hinge portion may provide portions of second ground engaging member  602  with the ability to bend, rotate, or otherwise move, relative to other portions of second ground engaging member  602 , or relative to other portions of outer member  116 . In some embodiments, in order for apex  412  of second ground engaging member  602  to decrease in height, first hinge portion  616 , second hinge portion  618 , and/or third hinge portion  620  may each allow a splaying outward of the arm portions of second ground engaging member  602 , in particular with respect to the two faces associated with each arm portion. For example, second ground engaging member  602  includes an arm portion  634 , which has a first face  630  along one side, and a second face  632  along the generally opposing side. Second hinge portion  618  provides a connecting portion between first face  630  and second face  632  that is flexible and permits rotation of one face with respect to the adjoining face. In some embodiments, this feature provides one means for ground engaging members to splay outward. 
     Furthermore, in different embodiments, fourth hinge portion  622 , fifth hinge portion  624 , sixth hinge portion  626 , seventh hinge portion  628 , and other hinge portions disposed along the base of second ground engaging member  602  may allow a flattening or widening of the arm portions of second ground engaging member  602  with respect to their connection to outer member areas  272 . For example, arm portion  634  of second ground engaging member  602  includes first face  630  that is adjoining an outer member area  636 . Sixth hinge portion  626  provides a connecting portion between first face  630  and outer member area  636  that is flexible, and permits rotation of first face  630  with respect to outer member area  636 . In some embodiments, this feature can allow ground engaging members to flatten in the vertical direction and/or expand in the horizontal direction. 
     Thus, in different embodiments, outer member  116  may experience different types of forces. During wear, foot and ground forces may compress the outer member along a generally vertical direction. In some embodiments, the outer member may be expanded or experience a force so that there is a splaying outward of the geometry of ground engaging member(s). This may occur during vertical compression, e.g., as a wearer exerts weight on article  100 . For example, as depicted in  FIGS. 7 and 8 , third compressive force  710  and/or fourth compressive force  812  can alter the extent of “splay-out” or horizontal expansion of first ground engaging member  600  and second ground engaging member  602 , particularly in the horizontal direction. In  FIG. 6 , two arm portions of second ground engaging member  602  form an obtuse angle  646 . In  FIG. 7 , as a result of third compressive force  710 , the two arm portions of second ground engaging member form an obtuse angle  712 . In this case, angle  712  is greater than angle  646 . Furthermore, in the embodiment of  FIG. 8 , the two arm portions of second ground engaging member  602  form an obtuse angle  810  after application of fourth compressive force  812 . In this case, angle  810  is greater than angle  712 . In other embodiments, forces may differ such that angle  712  may be greater than angle  646 , and/or angle  810  is greater than angle  712 . Furthermore, in some embodiments, the areas of first aperture  604  and second aperture  606  may increase when a compressive force is applied in the vertical direction. 
     Horizontal tensioning forces may also contribute to the expansion of ground engaging members. For example, when a ground engaging member experiences a horizontal tension due to friction with a ground surface, the ground engaging member may expand both in the direction of the tension, as well as in a direction perpendicular to the tension. 
     In some embodiments, the increased “splay-out” of first ground engaging member  600 , second ground engaging member  602 , third ground engaging member  610 , fourth ground engaging member  612 , and/or fifth ground engaging member  614  may alter the size, shape, and/or other characteristics of outer member  116 . For example, in  FIG. 6 , the depicted portion of outer member has a third length  638 , and a third width  640 . When one or more ground engaging members are compressed, as by third compressive force  710  in  FIG. 7 , the depicted portion of outer member  116  has an increased fourth length  702 , and an increased fourth width  704 . In  FIG. 8 , the depicted portion of outer member  116  has a fifth length  802  that is greater than fourth length  702 , and a fifth width  804  that is greater than fourth width  704 . The flattening or splaying of different ground engaging members may thus change, expand, or increase the area of outer member  116  in some embodiments. In one embodiment, the length of outer member  116  may expand to the same extent as the width of outer member as a result of an applied force. In other embodiments, the length of outer member  116  may not increase as much as the width of outer member  116 . For example, in some embodiments, fourth length  702  may expand or increase more relative to the expansion that occurs along fourth width  704  in response to the same force. In another embodiment, the width of outer member  116  may not increase as much as the length of outer member  116 . For example, in some embodiments, fourth width  704  may expand or increase more relative to the expansion that occurs along fourth length  702  in response to the same force. Thus, the auxetic properties of the ground engaging members may allow various levels of expansion to outer member  116  that increase its size in the horizontal direction. 
     Depending on the magnitude and the direction of the force(s) applied, changes in area or shape may vary. It should be noted that forces applied in the lateral direction, as seen in  FIGS. 4 and 5 , may also result in similar changes in ground engaging member shapes, sizes, heights and/or area of outer member  116 . For example, a tension may be applied to or along the sides of outer member  116 , and may result in the splaying-out of ground engaging members. This can lead to a decrease in the height of the apex, which can create expansion in outer member  116 . Thus, forces in the vertical, horizontal, or other directions may result in expansion in multiple directions. 
     In different embodiments, the overall geometry of the ground engaging members may also change. In some embodiments, a different force may permit ground engaging member(s) to increase in height. For example, in one embodiment, the outer member may be exposed to a force whereby fifth height  706  is greater than third height  642 , seventh height  806  is greater than fifth height  706 , sixth height  708  is greater than fourth height  644 , and/or eighth height  808  is greater than sixth height  708 . 
     In different embodiments, the depths of apertures  300  may vary.  FIG. 9  depicts a cross-section of the embodiment shown in  FIG. 3 , along the line labeled  FIG. 9 . In  FIG. 9 , it may be seen that the average depth of apertures  300  may be substantially uniform throughout outer member  116 . For example, in  FIG. 9 , a first depth  904  of a first aperture  900  is substantially similar to a second depth  906  of a fourth aperture  902 . In other embodiments, there may be differences in the average depth of each aperture. In one embodiment, apertures  300  may extend to a greater depth, where the material comprising any corresponding ground engaging member  122  on outer member  116  is relatively thin. This may permit greater bendability in ground engaging member  122 . In another embodiment, depth of apertures  300  may be relatively shallow, so that the material comprising any corresponding ground engaging member  122  is relatively thick. In other words, one or more ground engaging members  122  may be “filled in” to some extent, so that they are at least partially solid rather than hollow. This may permit ground engaging members  122  or cleats to have greater stiffness and provide a more firm response in movements requiring traction. 
     Additionally, the thickness of outer member  116  may vary in different embodiments. In  FIG. 9 , it may be seen that the thickness of outer member  116  is substantially uniform throughout some portions of outer member  116 . For example, in  FIG. 9 , a first thickness  908  of a base portion  924  is substantially similar to a second thickness  913  of base portion  924 , where the first thickness  908  and the second thickness  913  are taken at different regions of base portion  924 . In other embodiments, there may be minor differences in the average thickness of outer member  116  in different regions, allowing variations in the flexibility of outer member  116 . In one embodiment, for example, outer member  116  may be thicker in forefoot region  110  than in heel region  114  or midfoot region  112 . This may permit greater flexibility to the area of the foot associated with forefoot region  110 . In the exemplary embodiment of  FIG. 9 , outer member areas  922  and/or base portion  924  may have a uniform thickness. 
     In some embodiments, the thickness of various regions within a ground engaging member  914  can differ in order to provide increased strength and support to ground engaging member  914 . In one embodiment, the thickness of apex  412  may differ from the thickness of base portion  924 . For example, a third thickness  912  associated with apex  412  can be substantially greater than second thickness  913  associated with base portion  924 . In  FIG. 9 , third thickness  912  of apex  412  is also depicted as substantially greater than first thickness  908  associated with base portion  924  of outer member  116 . Such variation in thickness may be necessary to allow ground engaging members  122  to retain their overall shape and structure generally, while also deforming or expanding in response to external forces. As seen in magnified area  910 , the varying thicknesses of the material of outer member  116  and ground engaging members  122  contributes to a reinforced layer that stabilizes the flexible nature of the material comprising outer member  116  and ground engaging members  122 . The reinforcement of apex  412  with greater thickness can also provide additional traction, strength, and or rigidity to ground engaging member  914  than areas of outer member  116  with lesser thickness. 
     Furthermore, portions of ground engaging member  914  may have variations in thickness relative to apex  412 . For example, ground engaging member  914  includes a first face  928  and a second face  930 . First face  928  can include a first intermediate portion  932  extending between apex  412  and base portion  924 , and second face  930  may include a second intermediate portion  934  extending between apex  412  and base portion  924 . The third thickness  912  associated with apex  412  can be seen to be thicker than a fourth thickness  936  of first intermediate portion  932 . In some embodiments, apex  412  is also thicker than second intermediate portion  934 . 
     In some embodiments, the thickness of various portions of faces along ground engaging member  914  may differ from the thickness associated with apex  412 . For example, in  FIG. 9 , first face  928  includes an end portion  938  attached to base portion  924 . End portion  938  is associated with a fifth thickness  940 . In one embodiment, fifth thickness  940  can differ from third thickness  912  of apex  412 . In the embodiment of  FIG. 9 , fifth thickness  940  is less than third thickness  912 . In some embodiments, the thickness of end portion  938  may be similar to the thickness of base portion  924 . In  FIG. 9 , fifth thickness  940  is substantially similar to second thickness  913 . 
     In addition, as seen in magnified area  910 , ground engaging member  914  has an outer surface  918  and a corresponding inner surface  916 . Inner surface  916  and/or outer surface  918  of ground engaging member  914  can include curved regions. In one embodiment, the portion of inner surface  916  associated with apex  412  includes an inner apex surface  920 , and the portion of outer surface  918  associated with apex  412  includes an outer apex surface  926 . In particular, inner apex surface  920  and/or outer apex surface  926  may include curved regions. For example, in some embodiments, the area associated with outer apex surface  926  is rounded. In one embodiment, inner surface  916  associated with inner apex surface  920  is also rounded. In some embodiments, the surface of outer apex surface  926  may be convex, and the surface of inner apex surface  920  may be concave. 
     In different embodiments, the curvatures of inner apex surface  920  and/or outer apex surface  926  may differ. For example, in  FIG. 9 , the curvature of outer apex surface  926  associated with apex  412  is greater than the curvature of inner apex surface  920  associated with apex  412 . In some embodiments, outer apex surface  926  may be characterized as having a smaller radius of curvature than inner apex surface  920 . 
     As noted earlier, in different embodiments, due to the material included in outer member  116  and ground engaging members  122 , portions of sole structure  102  may compress and deform to various degrees. For example, in some embodiments, as a result of the application of a deforming force, ground engaging members  122  may expand so that there is greater “splay out” of ground engaging members  122 . In such a case, the apex of a ground engaging member may decrease in height, while the arm portions of the same ground engaging member may expand in width. In some embodiments, portions of outer member  116  may in turn also expand. 
     It should be noted that the various degrees of bending described and shown here are for purposes of illustration. In some situations outer member  116 , ground engaging members  122 , and/or sole structure  102  may not undergo compression to the extent depicted, or may bend less, depending on various factors such as the materials used in the production of outer member  116  and ground engaging members  122 , the manner of attachment to upper  108 , or other factors. For example, if outer member  116  is joined or attached to a less reactive material, the compressive and/or expansive properties described herein may differ, or be limited. In some embodiments, when outer member  116  is joined to a strobel or other structure, the capacity of expansion may decrease. In some embodiments, the perimeter of outer member  116  may be fixed, e.g., bonded to a strobel layer. However, in such embodiments the auxetic structure of outer member  116  may still facilitate increased flexibility for portions of outer member  116  even though the dimensions of the perimeter of outer member  116  may not change. 
     Elasticity and flexibility of a sole component such as sole structure  102  is an important factor associated with comfort for article of footwear  100 . In some embodiments, the stiffness of article of footwear  100  can be evaluated by twisting article of footwear  100  in one or more directions.  FIGS. 10-13  depict additional embodiments of article of footwear  100 . In some embodiments, a force may be applied such that one or more regions are bent. The material(s) selected for sole structure  102  may permit variation in the degree of possible bending. In  FIG. 10 , article of footwear  100  is shown at rest. In  FIG. 11 , article of footwear  100  has been bent as a result of a force  1104 . Sole structure  102  has been deformed upward from midfoot region  112  so that forefoot region  110  is raised upwards. In other embodiments, the degree of bending may be greater or smaller, depending on the force applied and the materials comprising the structure of article of footwear  100 . 
     Furthermore, in the embodiment of  FIG. 10 , a ground engaging member  1002  is shown in a magnified area  1000  of sole structure  102 . Ground engaging member  1002  has a first width  1004 . When forefoot region  110  of outer member  116  is bent upwards, ground engaging member  1002  expands in order to permit bending. In  FIG. 11 , ground engaging member  1002  has become relatively flatter, and can be seen in magnified area  1100  as expanded to a larger width  1102 . 
     Moreover, article of footwear  100  may be bent along a different axis or plane, further highlighting the high degree of flexibility of sole structure  102 . For example, in  FIG. 12 , article of footwear  100  is shown at rest. In  FIG. 13 , sole structure  102  of article of footwear  100  has been bent outwards relative to its center line, a longitudinal axis  1208 . The bending is a result of a first force  1306  from along lateral side  240  and a second force  1308  from along medial side  238 , forming an angle  1310 . Sole structure  102  has been deformed upward along its sides so that medial side  238  and lateral side  240  are raised up relative to longitudinal axis  1208 . In other embodiments, angle  1310  may be greater or smaller, depending on the force applied and the materials comprising the structure of article of footwear  100 . 
     Furthermore, in the embodiment of  FIG. 12 , a ground engaging member  1206  is shown in a magnified area  1200  of sole structure  102 . Ground engaging member  1206  has a first width  1202 . When forefoot region  110  of outer member  116  is bent upwards along longitudinal axis  1208 , ground engaging member  1206  expands in order to permit bending. In  FIG. 13 , width of ground engaging member  1206  has expanded to a larger width  1302  and ground engaging member  1206  become relatively flatter, and can be seen in magnified area  1300 . Similarly, in  FIG. 12 , a first height  1204  of apex  412  of ground engaging member  1206  has decreased, allowing ground engaging member  1206  to flatten, so that first height  1204  is decreased to a second height  1304  in  FIG. 13 . 
     Thus, in some embodiments, in response to compressive or other forces, ground engaging members  122  may expand so that one or more ground engaging members  122  “splay out” and increase in surface area along outer member  116 . In such a case, the apex of the ground engaging member may decrease in height, while the arm portions of the same ground engaging member may expand in their average width. In some cases, this expansion occurs in the horizontal direction. In some embodiments, outer member  116  may also expand. This may permit extension of sole structure  102  in a way that promotes a higher flexibility of article of footwear  100 . Such flexibility can be important to a wearer in order to achieve increased foot mobility. With greater flexibility, impedances to movement may be minimized. An article of footwear which bends with very little pressure or force, allowing the feet to move freely in all directions, may improve performance in a variety of athletic events. In addition, a flexible sole structure  102  can provide a user with a much greater comfort level. 
       FIGS. 14-16  depict different embodiments of article of footwear  100  with ground engaging members  122 .  FIG. 14  depicts a side-view of one embodiment of assembled article of footwear  100 , including sole structure  102  and upper  108 . In some embodiments, ground engaging members  122  may vary in height from one another. In another embodiment, as shown in  FIG. 14 , ground engaging members  122  may have substantially similar heights throughout outer member  116 . 
     In some embodiments, ground engaging members  122  may be disposed all along outer member  116 , so that substantially the entire base portion  120  of outer member  116  from forefoot region  110  to heel region  114  includes ground engaging members  122 . In other embodiments, ground engaging members  122  may be utilized at any suitable location of outer member  116 . In some embodiments, ground engaging members  122  having particular shapes and configurations may be disposed at regions of outer member  116  corresponding with various anatomical portions of the foot. Furthermore, in some embodiments, article  100  may include greater or fewer ground engaging members  122  as desired to provide performance characteristics suitable for the desired use. 
     For example, as illustrated in  FIG. 15 , one or more ground engaging members  122  may be disposed in areas that correspond with forefoot region  110  and heel region  114 . An athlete may place a significant amount of their weight on these regions during certain movements, such as cutting in a lateral direction  236 , or during abrupt stopping. Such an embodiment may provide an athlete with greater flexibility along midfoot region  112 . In other embodiments, forefoot region  110  may have a reduced number of ground engaging members  122 , in order to provide sole structure with even greater flexibility along forefoot region  110 . Such portions may include at least one ground engaging member  122  in order to provide traction in lateral direction  236 . However, an article of footwear that includes ground engaging members  122  in forefoot region  110  and/or other regions, as depicted in  FIG. 15 , may nevertheless continue to provide a high level of flexibility in those regions, due to the construction of outer member  116  described herein. 
     The configuration of sole structure  102  may vary significantly according to one or more types of ground surfaces on which sole structure  102  may be used in different embodiments. Accordingly, outer member  116  may be configured to provide traction on various surfaces, such as natural turf (e.g., grass), synthetic turf, dirt, snow. In some embodiments, sole structure  102  may also vary based on the properties and conditions of the surfaces on which article  100  is anticipated to be used. For example, sole structure  102  may vary depending on whether the surface is harder or softer. In addition, sole structure  102  may be tailored for use in wet or dry conditions. In other embodiments, the configuration of sole structure  102 , including the traction pattern of outer member  116 , may vary significantly according to the type of activity for which article  100  is anticipated to be used (for example, running, soccer, baseball, football, and other activities), as described further below. 
     In some embodiments, sole structure  102  may be configured for versatility. For example, sole structure  102  may be configured to provide traction and stability on a variety of surfaces, having a range of properties, and/or under various conditions. In another embodiment, a versatile embodiment of sole structure  102  may include both larger and medium sized ground engaging members  122 , and/or ground engaging members  122  having moderately to minimally aggressive shapes, a different number of hinge portions, and being disposed in different regions of outer member  116 . In  FIG. 16 , for example, a series of large three-pointed diamond shaped ground engaging members  1604  are disposed in heel region  114  and a series of medium three-pointed diamond shaped ground engaging members  1600  are disposed in forefoot region  110 . Furthermore, a number of small three-pointed star shaped ground engaging members  1602  are disposed in midfoot region  112 . While the number, size, and shape of ground engaging members  122  are provided as examples, other structural parameters may be varied in order to tailor article  100  for traction and stability on various surfaces, and/or in a variety of conditions. Additional such parameters may include, for example, the use of secondary traction elements, placement of ground engaging members  122 , the relative softness or hardness of the ground engaging members  122  and/or sole structure  102  in general, the relative flexibility of portions of sole structure  102 , and other such parameters. 
     In different embodiments, there may be outer member areas  272  that move relative to ground engaging members  122  in order to allow expansion and/or compression. For example, in  FIGS. 17 and 18 , a first outer member area  1700 , a second outer member area  1702 , a third outer member area  1704 , a fourth outer member area  1706 , a fifth outer member area  1708 , and a sixth outer member area  1710  are shown in the context of a sole structure  1754 . Outer member areas  272  surrounding a first ground engaging member  1748  in  FIGS. 17 and 18  have a substantially triangular shape. 
     Each outer member area depicted in a magnified area  1750  and a magnified area  1800  is defined or bounded in part by arm portions and/or faces of adjacent ground engaging members  122 . In the embodiment of  FIGS. 17 and 18 , first outer member area  1700  is bounded by a first face  1712 , a seventh face  1724 , and a fourteenth face  1738 . Second outer member area  1702  is bounded by a second face  1714 , an eighth face  1726 , and a fifteenth face  1740 . Third outer member area  1704  is bounded by a third face  1716 , a ninth face  1728 , and a sixteenth face  1742 . Fourth outer member area  1706  is bounded by a fourth face  1718 , a tenth face  1730 , and a seventeenth face  1744 . Fifth outer member area  1708  is bounded by a fifth face  1720 , an eleventh face  1732 , and an eighteenth face  1746 . Sixth outer member area  1710  is bounded by a sixth face  1722 , a twelfth face  1734 , and a thirteenth face  1736 . 
     In different embodiments, as one or more ground engaging members  122  of sole structure  1754  expand from  FIG. 17  to  FIG. 18 , outer member areas  272  may shift position and/or orientation. For example, in  FIG. 17 , first outer member area  1700  has a first position  1756  relative to first ground engaging member  1748 . However, after expansion of first ground engaging member  1748  in  FIG. 18 , first outer member area  1700  has a second position  1804 . In some embodiments, first position  1756  of first outer member area  1700  is different from second position  1804 . In one embodiment, upon expansion of first ground engaging member  1748 , first outer member area  1700  can rotate so that second position  1804  accommodates the expansion of ground engaging members  122 . Similarly, in other embodiments, second outer member area  1702 , third outer member area  1704 , fourth outer member area  1706 , fifth outer member area  1708 , sixth outer member area  1710 , and other outer member areas  272  may also change position relative to adjacent ground engaging members  122  upon the expansion of one or more portions of sole structure  1754 . In at least some embodiments, these outer member areas may be seen to rotate with respect to one another, to allow for increases in the horizontal area of the ground engaging members. 
     As shown in  FIGS. 19-21 , in some embodiments, ground engaging members  122  may include additional features that contribute to an increased flexibility and/or responsiveness of outer member  116 . In  FIG. 19 , a ground engaging member  1900  is disposed along a portion of an outer member  1902 . Ground engaging member  1900  includes a first face  1908  and a second face  1910 . First face  1908  and second face  1910  are joined along a hinge portion  1912 . First face  1908 , second face  1910 , and hinge portion  1912  can be representative of additional faces and/or hinge portions comprising ground engaging member  1900 . Furthermore, ground engaging member  1900  includes an apex  1906 . 
     In one embodiment, as shown in  FIG. 19 , ground engaging member  1900  is lightly contacting a ground surface  1904 . Upon the application of greater pressure, as seen in  FIGS. 20-21 , ground engaging member  1900  can be compressed. Due to the varied properties of the embodiment as described above, ground engaging member  1900  may respond to a force by bending and/or by exhibiting auxetic action. In one embodiment, as shown in  FIG. 20 , when undergoing bending stresses, apex  1906  of ground engaging member  1900  can respond by bending or flexing to various degrees, deforming at least part of ground engaging member  1900 . This bending or deformation may be facilitated by the substantially thicker apex  1906 , relative to the faces of ground engaging member  1900 , as discussed above and shown in  FIG. 9 . Such bending and/or deformation may enhance the capacity of ground engaging member  1900  to provide traction. In this embodiment, first face  1908  and second face  1910  do not necessarily rotate along hinge portion  1912 , and there may be little or no auxetic action. In another embodiment, as shown in  FIG. 21 , ground engaging member  1900  can respond to forces by expanding in an auxetic action. Thus, the auxetic structure of ground engaging member  1900 , as represented by the movement of first face  1908  relative to second face  1920  along hinge portion  1912 , may permit ground engaging member  1900  to respond to the force through an expansion of ground engaging member  1900  and corresponding portions of outer member  1902 . It should be noted that in other embodiments, in response to a force, ground engaging member  1900  may exhibit various deformations, for example though bending as well as expansion resulting from an auxetic action. 
     In some cases, it may be advantageous to provide increased torsional traction on one foot, and to provide decreased torsional traction on the other foot to enable greater freedom of motion. That is, it may be desirable to provide one or more portions of the rear foot with a reduced amount of torsional traction and provide one or more portions of the front foot with an increased amount of torsional traction. Accordingly, in some embodiments, asymmetric outer members may be provided for left and right feet. That is, outer member  116  for a left foot may be a non-mirror image of the outer member  116  for a right foot. 
     While various embodiments of the embodiment have been described, the description is intended to be exemplary, rather than limiting and it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible that are within the scope of the embodiment. Although many possible combinations of features are shown in the accompanying figures and discussed in this detailed description, many other combinations of the disclosed features are possible. Therefore, it will be understood that any of the features shown and/or discussed in the present disclosure may be implemented together in any suitable combination. Accordingly, the embodiment is not to be restricted except in light of the attached claims and their equivalents. Also, various modifications and changes may be made within the scope of the attached claims.