WO2023141194A1

WO2023141194A1 - Impact absorbing elements with joining structure

Info

Publication number: WO2023141194A1
Application number: PCT/US2023/011124
Authority: WO
Inventors: David Hall; Jordan KLEIN; Aqheel MOHAMMAD
Original assignee: Park & Diamond
Priority date: 2022-01-19
Filing date: 2023-01-19
Publication date: 2023-07-27

Abstract

An impact absorbing structure includes an impact absorbing material, a recipient body, and a frame. The frame is bonded to the recipient body. The recipient body and the frame together encapsulate the impact absorbing material. The frame is self-supporting. An impact absorbing structure includes an impact absorbing material with at least one perimeter edge that includes an opening or irregularity, a recipient body, and a frame that is bonded to the recipient body. The recipient body and the frame together encapsulate the impact absorbing material. The frame covers at least the one perimeter edge of the impact absorbing material. The frame provides stiffness at the one perimeter edge that is consistent with stiffness of the impact absorbing material away from the opening or irregularity.

Description

IMPACT ABSORBING ELEMENTS WITH JOINING STRUCTURE

BACKGROUND

[0001] Impact absorbing equipment contains impact absorbing material that is typically rigid to provide the necessary structural stiffness to absorb the appropriate amount of impact energy. Personal Protective Equipment (PPE) is a common application of impact absorbing equipment, and often requires very rigid material to absorb high-energy impacts. However, PPE has been limited in its application due to having to conform to relatively small, curved areas and limited in its application to being manipulated into one or multiple configurations.

[0002] The design approach of the current state of the art has two different directions. The first approach is to use large, rigid bodies and the second is to use multiple flexible layers that would not be sufficient individually but provide the necessary characteristics in combination.

[0003] An example of the first approach is body armor for military applications which often feature a single, solid metal plate covering large areas such as the torso. The large continuous plate provides the necessary high-energy impact absorption, however such a rigid plate cannot conform to other areas of the body, nor can it be manipulated to different configurations, such as the articulation of joints. Therefore, in this specific example, many areas of the wearer’s body, such as the arms and legs, cannot be protected with the same impact absorbing material as the plate on the wearer’s rear torso. United States Patent No. 3,559,210 exemplifies a design approach of a large rigid body for impact absorption.

[0004] The second approach relies on a series of flexible layers to provide the proper characteristics in combination. This design approach has been developed with the implementation of aramid fibers and other woven fibers to provide greater impact absorption characteristics while still offering a flexible laminar design. The concern with this approach is that the current state of technology for these flexible or semi-flexible layers is not fully sufficient for many impact scenarios, resulting in a reduced degree of protection when compared to the former design direction. United State Patent No. 4,522,871 exemplifies a design approach of flexible layers.

[0005] U.S. Patent Application Publication 2019/0307199 Al, which is hereby incorporated by reference in its entirety, illustrates a bicycle helmet.

SUMMARY

[0006] The drawbacks of the two design approaches often results in a combination of these two approaches to compensate for their inherent weaknesses, i.e. a large rigid plate on the back of the body armor to cover as much surface area as possible with the highest degree of protection as possible, and then the laminar protection on the rest of the body that provides flexibility at the cost of protection. Many impact absorbing applications have suffered from having to compromise on the amount of protection due to large, rigid impact absorbing materials that limit ergonomics, range of motion, and cannot be applied well to curved surfaces. European Patent No. 2 578 986 A2 exemplifies the compromised result of a combination of the former and latter design approach.

[0007] The incorporation of rigid and/or semi rigid materials (for greater impact attenuation) with flexible materials (for greater conformance and manipulation) brings challenges with how the bodies interact, namely how the bodies constrain each other. It is desirable for the rigid bodies to stay fully constrained by the flexible material to prevent the rigid bodies from moving before, during, and potentially after an impact. A situation that demands that bodies do not move during an impact would be body armor where the rigid plate shown in European Patent No. 2 578 986 A2 must be constrained within the layers of the flexible fabric. The overall impact attenuation, and therefore the protection, of the body armor would be reduced if the plate were to unintentionally move away from the impact location by the wearer’s movement. Similarly, it would be extremely detrimental if the plate were to move from the impact itself when the projectile, during impact, physically moves the plate away from the impact location. Finally, it may also be detrimental if the impacted plate were to move after being impacted and could pose a risk to the user. One could easily imagine a situation where the wearer moves in a certain manner and an unconstrained plate could move about and expose a vulnerable area, or the plate itself is pushed away, if ever so slightly, from the incoming projectile and exposes the wearer, or even the plate absorbing some or all of the impact and then transferring that energy to translational movement and potentially hitting or harming the wearer. A fully constrained system to prevent any unwanted movement is an important aspect to impact attenuation systems, and the current state of art often relies upon stitching or bonding to keep the flexible layers together to encapsulate the rigid body, as is the case for European Patent No. 2 578 986 A2.

[0008] The application of stitching has many challenges including geometries that may be physically difficult to stitch (small areas, tight gaps between thick bodies, non- continuous lines and spaces), require higher quality than stitching can typically provide, waterproof and weather-resistant applications, and other challenges. The application of bonding materials such as hot-melt adhesives has many challenges including affecting the rigid body with the adhesive material’s composition and/or application, environmental effects, reducing flexibility, and lifespan of the bond strength. In addition, partially or fully encapsulating the rigid body with the flexible material around it relies upon the flexible material to constrain the rigid body, which may not be suitable for certain applications. Relying upon stitching or bonding of the layer(s) to provide the necessary constraint of the rigid impact absorbing body has been a challenge in view of design constraints, manufacturing effects, and the overall lifecycle of the product. A new design that grants partial or full constraint of the rigid body to the flexible body can be very advantageous for many applications, and ultimately allow for greater performance, reliability, and protection.

[0009] The present technology may provide a solution to this and other problems by including impact absorbing equipment which contains impact absorbing material, with the incorporation of a frame, multiple layers of impact absorbing segments, and/or nonlinear systems to improve the performance, reliability, and applicability of impact absorbing material and impact attenuation systems.

[0010] Conventional technology relies upon a compromise between the high energy absorption of rigid impact attenuation material and the comparably low energy absorption of flexible, laminar impact attenuation material. Many conventional designs rely upon large, rigid impact attenuation bodies that may be partially or fully constrained by flexible material that may or may not consist of flexible, laminar impact attenuation material. The flexible material acts as an independent or living hinge (e.g., integrated hinge) between the rigid bodies. This allows the impact absorbing equipment to conform, bend, or manipulate around a body in one or multiple configurations. However, relying upon the flexible material to provide the partial or full encapsulation of the rigid material results in many limitations.

[0011] The present technology may provide a solution to this and other problems by including a frame that is a rigid or semi-rigid material that partially or completely encapsulates the rigid material to retain the rigid material to the larger impact absorbing equipment, forming a tile or node. The frame may include a flange to increase surface area to bond/attach the frame to the recipient body, which may be a flexible material and/or a living hinge. Adhering or bonding the frame to the flexible material may include adhesives (such as hot-melt adhesives), heat staking through the flexible material, high frequency welding of the frame material to the flexible material, or ultrasonically bonding the frame material to the flexible material, or a variation of these applications to a system of bodies (such as a top clamp and a bottom clamp) to retain the frame to the flexible material. A flange that runs perpendicular to the walls of the frame and parallel with the fabric (or a variation of these angles and faces) can increase the bonding area of the flange to the hinge body, which may improve the performance of constraining the impact absorbing material.

[0012] Conventional technology often relies upon the rigid impact attenuation material to provide a significant amount of impact energy absorption, while the flexible hinge material often provides less significant or no energy absorption at all. This system loses the opportunity to create a non-linear system for further performance gains, as well as the practical benefit of the hinge material providing protection to the rigid material.

[0013] The present technology may provide a solution to this and other problems by including a frame of alternative structural stiffness to allow for offset buckling modes. This may allow for the peak loading of the frame to occur before the peak loading of the impact absorbing material, thus avoiding compounding the two peaks while increasing the overall energy absorption. Compounding the maximum amount of acceleration on the deforming frame (and therefore the maximum amount of the rate of energy absorption) and the impact attenuation material would result in the decreased acceleration of the impacting body, which may be especially desirable in helmet impacts where a quick jerk (i.e., quick time rate of change of acceleration) during impact may be far more undesirable than a slower, smoother deceleration. Alternatively, the frame could reach peak loading after peak loading of the impact absorbing material.

[0014] The frame also may provide the benefit of reinforcing opening(s) and/or irregularities within the material itself, the edges around the material, as well as the gaps and irregularities between impact absorbing nodes. For example, the frame could match the structural stiffness of the impact absorbing material and be located along the perimeter of the absorbing material to provide a consistent structurual stiffness along the edges where processing (such as cutting) could potentially have compromised the perimeter of the impact absorbing material. Similarly, this may be applied in other locations such as any inconsistencies within the material itself, and to ensure a consistency in structural stiffness between impact absorbing nodes in the larger system that comprises the impact absorbing equipment. The frame may also be significant when the frame has an alternative structural stiffness and allows for stiffnesses in general as well as specific locations, and reinforcement in specific areas beyond what would be capable from just the impact absorbing material or a system of similar structural stiffness frames and impact absorbing material. The alternative structurual stiffness of the frames when compared to the impact absorbing material may allow for further optimization of an individual impact absorbing node, as well as the overall system of impact absorbing nodes. Alternatively, the frame could have greater stiffness than the impact absorbing material, which could, for example, provide greater reinforcment in the gaps between impact absorbing nodes.

[0015] The frame may also protect the rigid impact absorbing material from being compromised by minor, insignificant impacts. This scenario of minor impacts affecting the impact absorbing material is especially apparent for plastically deforming foams (such as EPS, i.e., expanded polystyrene) which have such low plastic deformation points that many small bumps and drops throughout normal use cause the impact attenuation material to deform, thus altering its protection performance. Similarly, this may be important for many very brittle impact absorbing materials, such as ceramics, which have very favorable characteristics for high-energy impacts, yet their brittle nature leads them to significant compromise (such as fracturing and cracking) in the event of small, unintentional impacts. The implementation of the present technology allows for minor impacts that are below the frame elastic limit to not materially affect the performance of the impact attenuation system.

[0016] Conventional technology typically relies upon a single layer of the rigid impact absorbing material being encapsulated by one or more layers of flexible material to act as a living hinge. There may be a single rigid structure or an array of rigid structures to provide the necessary protection, however this array of rigid structures still suffers from the aforementioned compromise in protection or flexibility/conformance between rigid impact absorbing structures and flexible hinge material. Many designs have tried to reduce this compromise by reducing the size and increasing the quantity of the rigid impact absorbing structures, which brings an obvious efficiency loss in protection due to more exposed area between rigid material segments than a large continuous body.

[0017] Another step to reduce this compromise is to overlap the rigid segments to varying degrees to partially or fully cover the newly exposed areas. However, a system with homogenous, segmented material only creates inefficiency when compared to a homogeneous, continuous material and may come at the cost of increasing the thickness of the impact absorbing equipment, further manufacturing and processing, additional constraining required, and other detriments without a material improvement in protection performance.

[0018] The present technology may provide a solution to these and other problems by creating a nonlinear system with the implementation of an alternative structural stiffness frame, as well as the impact absorbing nodes to contain different impact absorbing materials. The present technology may include two or more layers of impact attenuating tiles containing impact absorbing material. Each layer may partially or completely interlock with the respective layer(s) to provide continuous coverage, all the while constraining translational motion between the layers without compromising rotational motion.

[0019] Similarly, the present technology may include layers that are stacked on top of each other, and rather than interlocking, the layers may be offset in relation to each other to provide continuous coverage.

[0020] The present technology may also include impact attenuation tiles and/or layers of impact attenuation tiles comprising multiple impact absorbing materials. Each layer of impact absorbing material or layer of tile(s) may be stacked on top of, inserted into, or in proximity of another, and may have unique characteristics.

[0021] The present technology may also include modifications to the structure of the frame to affect the impact response of the structure, such as tapered walls, offset walls, and curved walls, among other designs. The combination of different materials, geometries, material stiffnesses, layers, and combinations thereof can provide unique characteristics and creates a nonlinear system.

[0022] The present technology of impact attenuation structures may be applicable where impact absorption and controlled buckling is desired, such as bike helmets.

[0023] In an example of the present technology, an impact absorbing structure comprises an impact absorbing material, a recipient body, and a frame that is bonded to the recipient body, wherein the recipient body and the frame together encapsulate the impact absorbing material, the frame is self supporting.

[0024] In a further example, the recipient body is a layer of flexible material.

[0025] In a further example, the recipient body extends outward of a perimeter of where the frame is bonded to the recipient body to form a living hinge.

[0026] In a further example, the frame has a lower structural stiffness than the impact absorbing material.

[0027] In a further example, the frame is configured to undergo peak loading during an impact before the impact absorbing material undergoes peak loading. The frame may undergo peak loading between 20% and 40% of the peak loading of the impact absorbing material or undergo peak loading at 30% of the peak loading of the impact absorbing material.

[0028] In a further example, the frame comprises material that undergoes plastic deformation under load.

[0029] In a further example, the frame is plastic that undergoes plastic deformation under load.

[0030] In a further example, the impact absorbing material further comprises a first plurality of the impact absorbing material, a first plurality of the frame bonded to the recipient body on a first side of the recipient body with first gaps between adjacent ones of the first plurality of the frame, a second plurality of the impact absorbing material, a second recipient body, a second plurality of the frame bonded to the second recipient body on a first side of the second recipient body with second gaps between adjacent ones of the second plurality of the frame, wherein the recipient body and the second recipient body form parallel layers.

[0031] In a further example, the first gaps and the second gaps are offset from one another.

[0032] In a further example, the first side of the recipient body and the first side of the second recipient body face towards one another.

[0033] In a further example, the first side of the recipient body and the first side of the second recipient body face towards one another with first plurality of frames being within the second gaps and the second plurality of frames being within the first gaps.

[0034] In a further example, the first side of the recipient body and the first side of the second recipient body face the same direction.

[0035] In a further example, the first plurality of the frame have a first height from the first side of the recipient body, the second plurality of the frame have a second height from the first side of the second recipient body, and the first height and the second height are different.

[0036] In a further example, the frame includes a side wall transverse to the recipient body, and the side wall includes a geometric feature to alter the buckling mode of the frame.

[0037] In a further example, the geometric feature comprises a notch or a slot.

[0038] In a further example, the geometric feature comprises an offset of the side wall.

[0039] In a further example, the geometric feature comprises a wave profile.

[0040] In another example, an impact absorbing structure comprises impact absorbing material with at least one perimeter edge that includes an opening or irregularity, a recipient body, and a frame that is bonded to the recipient body, wherein the recipient body and the frame together encapsulate the impact absorbing material, the frame covers at least the one perimeter edge of the impact absorbing material, and the frame provides structural stiffness at the one perimeter edge that is consistent with structural stiffness of the impact absorbing material away from the opening or irregularity.

[0041] In a further example, the opening or irregularity is caused by processing the impact absorbing material.

[0042] In a further example, the opening or irregularity is caused by cutting the impact absorbing material.

[0043] Other aspects, features, and advantages of this technology will become apparent from the following detailed description when taken in conjunction with the accompanying drawings, which are a part of this disclosure and which illustrate, by way of example, principles of this technology.

BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Fig. 1 illustrates a representative impact attenuating material.

[0045] Fig. 2A illustrates partially crushed impact attenuating material.

[0046] Fig. 2B illustrates a stress-strain curve represntative of Fig. 2A.

[0047] Fig. 3 illustrates a representative impact attenuating material with an area reduction modification.

[0048] Fig. 4A illustrates a representative impact attenuating material with a frame at starting point of frame failure.

[0049] Fig. 4B illustrates a stress-strain curve represntative of Fig. 4A.

[0050] Fig. 5A illustrates a representative impact attenuating material with a frame partially through a crush stroke.

[0051] Fig. 5B illustrates a stress-strain curve represntative of Fig. 5 A

[0052] Fig. 6A illustrates the impact of impact attenuating segments with an inconsistency in geometry.

[0053] Fig. 6B illustrates a stress-strain curve represntative of Fig. 6A.

[0054] Fig. 7A illustrates impact of impact attenuating segments with an inconsistency in geometry with frames to modify the stress-strain response of an impact.

[0055] Fig. 7B illustrates a stress-strain curve represntative of Fig. 7A

[0056] Fig. 8A illustrates impact of impact attenuating segments with an inconsistency in geometry with a frame of alternative structural stiffness to modify the stressstrain response of an impact.

[0057] Fig. 8B illustrates a stress-strain curve represntative of Fig. 8 A.

[0058] Fig. 9A illustrates a representative impact attenuating material with a frame of alternative structural stiffness with applied force below initiation of plastic deformation.

[0059] Fig. 9B illustrates a stress-strain curve represntative of Fig. 9A.

[0060] Fig. 10A illustrates a frame with complete (but illustrated transparent) encapsulation of a representative impact absorbing material

[0061] Fig. 10B illustrates a frame with partial (and opaque) encapsulation of a representative impact absorbing material. [0062] Fig. 11 A and 1 IB illustrate cross-section views of frames bonded to a living hinge material.

[0063] Figs. 12A, 12B, 12C and 12D illustrate cross-section views of frames bonded to a living hinge material.

[0064] Fig. 13 A illustrates two interlocking layers of impact attenuation nodes.

[0065] Fig. 13B illustrates a single layer of impat attentuaion nodes.

[0066] Fig. 14A illustrates two offset layers of impact attenuation nodes.

[0067] Fig. 14B illustrates a single layer of impat attentuaion nodes.

DETAILED DESCRIPTION OF EMBODIMENTS

[0068] Throughout this disclosure, stiffness is intended to mean resistance to deformation under load. Stiffness may be a material property (e.g., modulus of elasticity) or a structural property (e.g., a combination of material properties and geometry). Stiffness alone is intended to encompass both (i.e., may refer to a material property or a structural property). Material stiffness is intended to encompass stiffness as a material property. Structural stiffness is intended to encompass the combination of material properties and geometry.

[0069] FIG. 1 is a perspective view of a representative impact attenuating material. The impact absorbing material includes individual cells 2 that together form an impact absorbing structure 1. Note that there are a plethora of impact absorbing materials, geometries, bonds, and structures available for impact attenuation. The present technology may include, but is not limited to, impact attenuation structures such as the one shown.

[0070] FIG. 2A is a perspective view of a representative impact attenuating material, halfway through an exemplary crush stroke and FIG. 2B is an associated general stress-strain curve. The impact absorbing structure 1 includes an array of bonded impacted individual cells 2 that are being crushed by the applied impact force 5. The crushed impact absorbing structure 1 shown is an array of individual cells 2 as an example, but any material, geometry, bonding, and structure can be used for the impact attenuation. The impact absorbing structure 1, as well as the individual cells 2, are crushed downwards by force 5 which creates a certain amount of strain (displacement of the material crushed downwards from the original position) for a given stress. The graphical representation of this stress and strain relationship is given with the stress-strain graph 6 shown. An example of a typical stress-strain graph for a crushed impact absorbing structure 1 is shown with the peak load 7 and plateau load 8 shown. The overall area underneath the curve represents the overall energy absorbed 9 by the crushed impact absorbing structure 1. The peak load 7 typically represents the first point where the impact absorbing structure 1 ceases to elastically deform and begins to plastically deform. Elastic deformation is not permanent and allows the material and structure to maintain its physical characteristics before and after the applied load, for most materials and especially for materials used in impact dynamics. However, the plastic deformation is when the physical structure permanently changes and results in a greater degree of impact energy absorption. After the peak load 7, the impact absorbing structure 1 typically falls to a plateau load 8 that lasts for much longer than the peak load 7. The plateau load 8 typically provides a large amount of energy absorption for a typical impact, and a flatter and more predictable plateau load 8 is desired for more controlled impacts. Note that the force 5 can be at any angle, as long as it contacts the impact absorbing structure 1.

[0071] FIG. 3 is a perspective view of a representative impact attenuating material with an area reduction modification. The impact absorbing material includes individual cells 2 that together form an impact absorbing structure 10. Note that there are a plethora of impact absorbing materials, geometries, bonds, and structures available for impact attenuation. The present technology may include, but is not limited to, impact attenuation structures such as the one shown. The present technology may include a modification 3 to the impact absorbing structure 10 to reduce the amount of area that is engaged during an impact. The area modification 3 may reduce the amount of volume engaged during the impact. Reducing the amount of area engaged increases the amount of pressure applied to the remaining area. The increase in applied pressure to the remaining area and/or volume may initiate plastic deformation sooner than if the modification 3 were not present. The reduced area of engagement may be especially beneficial if occurring at the center of a face with a large surface area. This will reduce the overall engagement area on a large face, plus the centered location for the modification 3 will allow for impact absorbing material to be present around the perimeter of the face where greater structural stiffness may be desired. This has the benefit of allowing for a less stiff impact to occur, which can be beneficial for impacts where a low acceleration, given the appropriate amount of energy absorption, is desired such as bicycle helmets.

[0072] FIG. 4A is a perspective view of a representative impact attenuating material with a frame 12 of alternative structural stiffness, at starting point of frame failure, and FIG. 4B is an associated general stress-strain curve. The impact absorbing material includes individual cells 2 that together form an impact absorbing structure 1, what was previously described with respect to FIG 1. The present technology includes an impact absorbing frame 12 that partially or completely encapsulates the impact absorbing structure 1 with a similar or alternative structural stiffness. The frame 12 in the example shown has an alternative structural stiffness as shown by the higher frame peak load 15 compared to the previous peak load 7 in FIG. 2B, which is supported by both impacts having the same impact absorbing material and structure. Note that the frame 12 is structurally failing as shown by the failure lines 13 (which may be fracture or deformation). The failure of the frame is significant since it shows the plastic deformation of the structure and the frame peak load 15, along with a overall energy absorption 16 as shown with the stress-strain curve 14.

[0073] FIG. 5A is a perspective view of a representative impact attenuating material with a frame of alternative structural stiffness, partially through crush stroke (e.g., halfway through crush stroke), and FIG. 5B is an associated general stress-strain curve. The crushed impact absorbing structure 1 includes an array of bonded impacted individual cells 2 that are being crushed by the applied impact force 5, as described previously with respect to FIG 2A. The present technology includes an impact absorbing frame 17 that partially or completely encapsulates the impact absorbing structure 2 with a similar or alternative structural stiffness. The frame 17 in the example shown has an alternative structural stiffness as shown by the higher frame peak load 11 than the previous peak load 7 in FIG. 2B, which is supported by both impacts having the same impact absorbing material and structure. Note that the frame 17 is completely structurally failing as shown by the fracture/deformation lines 18, and the frame is failing more than the failure in FIG 4 A as shown by failure lines 13. The failure of the system of frame 17 and impact absorbing structure 1 (also referred to as a tile or node) creates a unique impact characteristic that can be seen in the stress-strain curve 19. The frame 17 has a greater structural stiffness as compared to the structural stiffness of the impact absorbing structure 1, which is shown by the fact that the frame peak load 11 occurs first and is greater than the impact structure peak load 7. Following the impact structure peak load 7 is the plateau load 8, and peak load 7 and plateau load 8 are consistent between FIG. 2B and FIG. 5B, and the frame peak load 15 in FIG. 4B is consistent with the frame peak load 11 FIG. 5B. The overall impact energy absorption of frame 17 and impact absorbing structure 1 is greater than the impact absorbing structure's overall energy absorption 9 in FIG. 2B and the overall energy absorption 16 in FIG. 4B. This shows that the impact characteristics of the different structures (e.g., impact absorbing structure 1 and impact absorbing structure 10) can be combined to create a unique structure for optimal impact performance.

[0074] The frame 17 can have a greater structural stiffness as compared to the impact absorbing structure 1 to provide offset buckling modes. This may allow for the frame peak load 11 to be greater and take place prior to the impact structure peak loading 7, thus avoiding compounding the two peaks while increasing the overall energy absorption. The offset buckling mode's overall energy absorption 20 will be higher than the overall energy absorption 9 of just the impact absorbing structure 1 in FIG 3. This greater energy absorption means greater protection performance without compounding the peak load 7 and the frame peak load 11 and therefore compounding the maximum acceleration of the deforming impact tile. Reducing the maximum acceleration while maintaining the appropriate amount of impact energy absorption may be relevant to an optimal impact since a high acceleration means a quick jerk during impact which is very undesirable in many scenarios. A slower, smooth deceleration is desirable and optimal for many, if not all impact attenuation scenarios, and especially safety equipment such as bike helmets.

[0075] FIG. 6A is a perspective view of the impact of impact attenuating segments with an inconsistency in geometry, a gap for example, with associated general stress-strain curve illustrated in FIG. 6B. The impact absorbing structure 21 includes an array of bonded individual cells 22 which may or may not be crushed by the applied impact force 5 with a certain geometry of impactor 24. The impact absorbing structure 21 shown is an array of individual cells 22 as an example, but any material, geometry, and structure can be used for the impact attenuation. The impact absorbing structure 21 is crushed downwards by the impactor 24 with a certain applied impact force 5 and creates a certain amount of strain (displacement of the material crushed downwards from the original position) for a given stress. An inconsistency 23, in this example a gap, is between or within the impact absorbing structure 21. The graphical representation of this stress and strain relationship is given with the stress-strain curve 25 shown. An example of a typical stress-strain graph for an impact absorbing structure 21 is shown with the peak load 26 and plateau load 27 shown. The overall area underneath the curve 28 represents the total amount of energy absorbed by the impact absorbing structure(s) 21. The stress-strain curve 25 is distinct from stress-strain curves in prior figures since the inconsistency 23 of the impact absorbing struture 21 results in a unique stress-strain relationship. The inconsistency 23 in the physical geometry of the impact absorbing structure 21 can lead to lower performance when compared to a continuous impact absorbing structure.

[0076] FIG. 7A is a perspective view of the impact of impact attenuating segments with an inconsistency in geometry (e.g., a gap) with frames to modify the stress-strain response of an impact, with associated general stress-strain curve illustrated in Fig. 7B. The impact absorbing material includes individual cells 2 that together form an impact absorbing structure 1, following the description associated with FIG. 1. The present technology includes an impact absorbing frame 29 that partially or completely encapsulates the impact absorbing structure 1 with a similar or alternative structural stiffness. The graphical representation of this stress and strain relationship is given with the stress-strain curve 31 shown. Note that the Frame 29 is structurally failing as shown by the fracture/deformation lines 30. The failure of the frame is significant since it shows the plastic deformation of the structure and the peak frame load 32. Note that the stress-strain curve 14 in FIG. 4B and the stress-strain curve 31 FIG.7B are not identical because, for example, the impact geometries are different (or undetermined), and the impact attenuation structures and geometries are different. The overall area underneath the curve 33 represents the total amount of energy absorbed by the frame(s) 29. The stress-strain curve 31 is distinct from prior stress-strain curves since the inconsistency 23 in geometry of the impact absorbing structure 1 results in a unique stressstrain relationship. Irregularities in the physical geometry of the impact absorbing structure 1 can lead to lower performance when compared to a continuous impact absorbing structure.

[0077] The frame 29 can have a similar structural stiffness as the impact absorbing structure 1 to reinforce opening(s) and/or inconsistency 23 within the material itself, the edges around the material, as well as the gaps and irregularities between impact absorbing nodes. For example, the frame could match the structural stiffness of the impact absorbing material and be located along the perimeter of the material to provide a consistent structural stiffness along the edges where processing (such as cutting) could potentially have compromised the perimeter of the impact absorbing material. Similarly, this may be applied in other locations such as any inconsistencies within the material itself, or to ensure a consistency in structural stiffness between impact absorbing nodes in the larger system. The force 5 can be at any angle, as long as the force 5 contacts the impact absorbing structure 1. Alternatively, the frame 29 could have greater stiffness than the impact absorbing material, which could provide reinforcment at an edge of the material to provide greater resistance to damage of the edge of the material (e.g., within the inconsistency 23 or at a perimeter of the impact absorbing structure 1).

[0078] FIG. 8A is a perspective view of the impact of impact attenuating segments with an inconsistency in geometry (e.g., a gap) with a frame of alternative structural stiffness to modify the stress-strain response of an impact, with associated general stress-strain curve for half of the impact attenuating segment stroke illustrated in FIG. 8B. The impact absorbing material includes individual cells 2 that together form an impact absorbing structure 34. The impact absorbing structure 34 includes an array of bonded individual cells 2 which may or may not be crushed by the applied impact force 5 with a certain geometry of impactor 24. The impact absorbing structure 34 shown is an array of individual cells 2 as an example, but any material, geometry, and structure can be used for the impact attenuation. The present technology includes an impact absorbing frame 36 that partially or completely encapsulates the impact absorbing structure 34 with a similar or alternative structural stiffness. The graphical representation of this stress and strain relationship is given with the stress-strain curve 38 shown. Note that the Frame 36 is structurally failing as shown by the fracture/deformation lines 37. The failure of the frame is significant since it shows the plastic deformation of the structure and the peak frame load 32.

[0079] The overall area underneath the curve 33 represents the total amount of energy absorbed by the impact absorbing structure 34. The stress-strain curve 25 is distinct from prior stress-strain curves since the inconsistency in geometry of the impact absorbing structure 34 results in a unique stress-strain relationship. Inconsistency 23 in the physical geometry of the impact absorbing structure 34 can lead to lower performance when compared to a continuous impact absorbing structure. The frame 36 can have similar structural stiffness as compared to the impact absorbing structure 34 (which can also be referred to as a tile or node) creates a unique impact characteristic that can be seen in the stress strain - curve 38. The same benefits of a similar structural stiffness frame 36 as described with respect to FIG 5A can be expected in this loading scenario of two impact absorbing structures 34 with a different geometry of impactor 24.

[0080] The frames 36 can have a greater structural stiffness as compared to the impact absorbing structure 1 to provide offset buckling modes. This may allow for the peak frame loading 32 to be greater and take place prior to the impact structure peak loading 26, thus avoiding compounding the two peaks while increasing the overall energy absorption. This may have some or all of the benefits described with respect to FIG 5 A and FIG 7A.

[0081] FIG. 9A is a perspective view of a representative impact attenuating material with a frame of alternative structural stiffness with applied force below initiation of plastic deformation, with associated general stress-strain curve illustrated in FIG. 9B. No deformation/engagement of impact absorbing material is illustrated. The impact absorbing material includes individual cells 2 that together form an impact absorbing structure 1. A representative impact absorbing structure is illustrated and includes individual cells 2 that are cylindrical and bonded together to form a single impact absorbing structure 1 for impact attenuation. The present technology includes an impact absorbing frame 39 that partially or completely encapsulates the impact absorbing structure 1 with a similar or alternative structural stiffness. The frame 39 has the ability to partially or fully protect the rigid or semi rigid impact absorbing structure 1 from being compromised by minor, minor impacts 35. The minor impact 35 would result in the frame 39 elastically deforming, as shown with deformation marks 40, to maintain the ability to protect the impact absorbing structure 1 from being structurally compromised. This scenario can be seen with the stress strain graph 41 that shows the strain reaching a point of elastic deformation 42, and then returning back to the origin of the graph. The frame 39 absorbs a certain amount of impact energy 43 from the minor impact 35, which would have been energy that could have been plastically absorbed by the impact absorbing structure 1 had the frame 39 not been present. The loading of the frame 39 from the minor impact 35 can be repeated in this scenario of elastic deformation without considering the fatigue effects on the frame 39, which are most likely only present in highly- repeated loading situations rarely seen in impact absorbing scenarios requiring large, rigid bodies. This scenario of minor impacts 35 affecting the impact absorbing material is especially apparent for plastically deforming foams (such as EPS) which have such low plastic deformation points that many small bumps and drops throughout daily use cause the impact attenuation material to deform, thus altering its protection performance. Similarly, this is important for many very brittle impact absorbing materials, such as ceramics, which have very favorable characteristics for high-energy impacts, yet their brittle nature leads them to significant compromise (such as fracturing and cracking) in the event of small, unintentional impacts. The implementation of the present technology allows for minor impacts that are below the frame elastic limit to not materially affect the performance of the impact attenuation system.

[0082] FIG. 10A is a perspective view of a frame with complete (but illustrated transparent) encapsulation of a representative impact absorbing material and Fig. 1 OB is a perspective view of a frame with partial (and opaque) encapsulation of a representative impact absorbing material. The impact absorbing material includes individual cells 2 that are bonded together to form an impact absorbing structure 1, following the description associated with FIG 1. The present technology includes a fully-encapsulating frame 44 or a partially- encapsulating frame 45 for the impact absorbing structure 1. The frames 44 and 45 may partially constrain the impact absorbing structure 1, and may be bonded/adhered to the recipient body 46 (e.g., bottom layer) to partially or fully constrain the impact absorbing structure 1. In addition, the frames 44 and 45 may provide the benefits previously.

[0083] FIG. 11 A and FIG. 1 IB are cross-section views of frames bonded to a living hinge material to partially or completely encapsulate a representative impact attenuating material. The impact absorbing material includes individual cells 2 that are bonded together to form an impact absorbing structure 1, following the description associated with FIG 1. The present technology includes a frame 47 that is a rigid or semi-rigid material that partially or completely encapsulates the rigid material to retain it to the recipient body 46 or to the larger impact absorbing equipment, forming a tile or node. The frames 47 may include a flange 48 (FIG. 1 IB) to increase surface area to bond/attach the frame 47 to the recipient body 46. The frame can be adhered or bonded to the living hinge by adhesives (such as hot-melt adhesives), heat staking through the recipient body 46, high frequency welding of the material of the frame 47 to the recipient body 46, or ultrasonically bonding the material of the frame 47 to the recipient body 46, or a variation/combination of these applications to a system of bodies (such as a top clamp/fixture and/or a bottom clamp/fixture) to partially or completely retain the frame 47 to the recipient body 46. The implementation of a flange 48, which may be perpendicular to the walls of the frame and parallel with the recipient body 46 (or a variation of these angles and faces), can increase the bonding area of the flange 48 to the recipient body 46 - thus improving the performance of constraining the impact absorbing materials. The combination of the impact absorbing structure 1 with the frame 47 and recipient body forms a tile or node 49.

[0084] FIG. 12A - FIG. 12D are cross-section views of frames bonded to a living hinge material to partially or completely encapsulate a representative impact attenuating material. The present technology may include impact attenuating nodes 49, following the description associated with FIG. 11 A and FIG. 1 IB, and include a frame 47 as described previously. The overall structure of the frame 47, and the ensuing node 49, can be varied to create different crushing behavior (often referred to as buckling modes because the structure buckles from the applied load). For example, FIG. 12A shows a node 49 with frame 47 that includes notches or slots 50 to affect the buckling modes of the structure. A single slot 50 or plural slots 50 can be incorporated. This permutation of the present technology may reduce the overall structural stiffness of the node 49, and/or may reduce the structural stiffness of the node 49 in specific areas such as the corners of the structure which may be too stiff. FIG. 12B shows another permutation of the present technology with offset side walls 51 that may allow for the geometry of the structure to better accommodate the geometry of the application (such as needing a wider perimeter along the edge that is bonded to the recipient body) and may also affect the buckling modes, such as increasing or decreasing the structural stiffness of the frame 47. Similarly, FIG 12C is another permutation that shows a tapered wall 52 that may be beneficial for geometric and manufacturing constraints, as well as altering the impact response of the frame 47. FIG. 12D includes a wavy side wall 53 that may also affect the impact response of the frame 47 and the overall node 49. These are examples of modifications of the frame 47 that affect the overall applicability and performance of the node 49. These modifications to the side walls may allow for further control of the buckling modes, as well as another variable in a nonlinear system to manipulate for greater performance. Other modifications may be employed to provide similar results.

[0085] FIG. 13 A is a cross-section view of two interlocking layers of impact attenuation nodes and FIG. 13B is a similar cross-section but of one layer of impact attenuation nodes. The present technology may include two or more layers 54 of impact attenuating nodes 49 containing impact absorbing material. An impact attenuating tile or node 49 contains impact absorbing structure 1 bonded to form an impact absorbing structure 1, along with a frame 47 and recipient body 46 following the description associated with FIG. 10A, FIG. 10B, FIG. 11 A and FIG. 1 IB. Layer 54 may interlock with layer 55 to provide continuous coverage while constraining translational motion with limited compromise to rotational motion of the layers when compared to a singular layer of nodes 57 as illustrated in FIG. 13B. A benefit of the configuration of FIG. 13A is that the impact attenuation nodes 49 are constrained from the surface closest to the impact on both sides (e.g., the surface facing impact and the surface opposite impact), which may result in more efficient impact absorption since the recipient body 46 is engaged in an impact. This efficiency may allow for a wider allowable gap 56 or inconsistency between nodes which may result in a greater degree of rotation, or many other design liberties may be achieved with the greater impact efficiency such as using thinner material that would reduce the overall bulk of the impact absorbing nodes 49, which may be especially useful for personal protective equipment which may be worn.

[0086] FIG. 14A is a cross-section view of two offset layers of impact attenuation nodes 49 and FIG. 14B is a cross-section view of one layer of impact attenuation nodes. The present technology may include two or more layers 58 and 59 of impact attenuating nodes 49, following the description associated with FIG. 9 A, FIG. 10A and FIG. 10B, containing impact absorbing material. Layer 59 is stacked on top of the other layer 58 and is offset so the space between the nodes 49 are not aligned. This layered design may reduce the vulnerability of the exposed space 60 between each impact attenuation node 49. Each layer 58 or 59 may also contain different impact absorbing materials with distinct characteristics. Another design element that can be varied is the stiffness and materials of the frame within the node 49 in relation to each layer 58 (i.e. a consistent frame material for the layer 58) or even each node 49 (i.e. a different frame material for each or a few nodes 49 in each layer). Note that layer 61 in FIG 14B shows a single layer of nodes 49 which are all thicker than the combined layers 58 and 59 of FIG 14A to highlight the improved impact efficiency of the combination of layers in FIG. 14A. The combination of different materials in series can provide unique characteristics and establishes a nonlinear system. The benefit is a nonlinear system that can be optimized for advantageous characteristics such as improved stiffness, strength, or buckling dynamics for improved impact response.

[0087] Each of the frames described above (e.g., frame 12, frame 17, frame 29, frame 36, frame 39, frame 44, frame 45 and frame 47) is preferably a self supporting structure. Here, self-supporting means that the frames maintain their shape under gravity. Self- supporting does not mean the shape is maintained in scenarios such as impact. Self-support can be achieved with a combination of material selection and geometric design. Cloth typically used for clothing (absent some sort of impregnation or other modification) would likely not be capable of self-support.

[0088] The frames may be made from a material that undergoes plastic deformation. Plastic deformation is the ability of a solid material to undergo permanent deformation, a non-reversible change of shape in response to applied forces. Materials that undergo a relatively large amount of plastic deformation may be more desirable than materials that undergo relatively less plastic deformation because plastic deformation aborbs energy and energy absorption may be particularly desirable for impact attentuation. Brittle materials (e.g., materials that fail with little elastic deformation and without significant plastic deformation) may be less desirable for use in the frames but could be employed nonetheless, particularly if the brittle material has desirable energy absorption properties despite the brittle failure mode.

[0089] Plastics (i.e., synthetic or semi-synthetic materials that use polymers as a main ingredient) may be a suitable material for the frame. Plastics often exhibit favorable levels of plastic deformation (e.g., relatively high plastic deformation) under load. Specific plastics may include acrylonitrile butadiene styrene (ABS), polycarbonate (PC), thermoplastic polyolefin (TPO) and thermoplastic polyurethane (TPU). However, not all plastics undergo large amounts of plastic deformation under load and some may be considered brittle materials. Brittle plastics may be desirable under certain circumstances. For example, where the frame is intended to protect the impact absorbing material from normal use but is not intended to provide a significant contribution to energy absorption during impact, brittle plastics could be employed.

[0090] In at least one embodiment, the frame is self-supporting and has a structural stiffness that is less than the structural stiffness of the impact absorbing structure. For example, the structural stiffness of the frame may be from 20% to 40% of the structural stiffness of the impact absorbing structure. The structural stiffness of the frame may be 30% of the structural stiffness of the impact absorbing structure. The relative structural stiffnesses may be characterized or measured by one or more of normal loading with a flat impactor, normal loading with a curved impactor (e.g., impactor 24 or either of a hemisphereical anvil and a curbstone anvil defined in 16 CFR Part 1203, Safety Standard for Bicycle Helmets), and oblique with a curved impactor at any or all surfaces that would be loaded under impact. Here, normal is used in the geometric sense (i.e., perpendicular). For example, applied impact force 5 in Fig. 2A is illustrated as a normal load. With the structural stiffness of the frame from 20% to 40% of the structural stiffness of the impact absorbing structure (e.g., 30%), the frame may have a favorable combination of properties that results in a non-linear system during impact while able to withstand normal use (e.g., wear and tear) such that impact absorption is not compromised by the normal use.

[0091] While the present technology has been described in connection with several practical examples, it is to be understood that the technology is not to be limited to the disclosed examples, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the technology.

Claims

WHAT IS CLAIMED IS

1. An impact absorbing structure comprising: an impact absorbing material, a recipient body, and a frame that is bonded to the recipient body, wherein the recipient body and the frame together encapsulate the impact absorbing material, and the frame is self- supporting.

2. The impact absorbing structure according to claim 1, wherein the recipient body is a layer of flexible material.

3. The impact absorbing structure according to claim 2, wherein the recipient body extends outward of a perimeter of where the frame is bonded to the recipient body to form a living hinge.

4. The impact absorbing structure according to claim 1, wherein the frame has a lower structural stiffness than the impact absorbing material.

5. The impact absorbing structure according to claim 4, wherein the frame is configured to undergo peak loading during an impact before the impact absorbing material undergoes peak loading.

6. The impact absorbing structure according to claim 4, wherein the frame is configured to undergo peak loading between 20% and 40% of the peak loading of the impact absorbing material.

7. The impact absorbing structure according to claim 4, wherein the frame is configured to undergo peak loading at 30% of the peak loading of the impact absorbing material.

8. The impact absorbing structure according to claim 1, wherein the frame comprises material that undergoes plastic deformation under load.

9. The impact absorbing structure according to claim 1, wherein the frame is plastic that undergoes plastic deformation under load.

10. The impact absorbing material according to claim 1, further comprising a first plurality of the impact absorbing material, a first plurality of the frame bonded to the recipient body on a first side of the recipient body with first gaps between adjacent ones of the first plurality of the frame, a second plurality of the impact absorbing material, a second recipient body, and a second plurality of the frame bonded to the second recipient body on a first side of the second recipient body with second gaps between adjacent ones of the second plurality of the frame, wherein the recipient body and the second recipient body form parallel layers.

11. The impact absorbing material according to claim 10, wherein the first gaps and the second gaps are offset from one another.

12. The impact absorbing material according to claim 11, wherein the first side of the recipient body and the first side of the second recipient body face towards one another.

13. The impact absorbing material according to claim 11, wherein the first side of the recipient body and the first side of the second recipient body face towards one another with the first plurality of frames being within the second gaps and the second plurality of frames being within the first gaps.

14. The impact absorbing material according to claim 11, wherein the first side of the recipient body and the first side of the second recipient body face the same direction.

15. The impact absorbing material according to claim 14, wherein the first plurality of the frame have a first height from the first side of the recipient body, the second plurality of the frame have a second height from the first side of the second recipient body, and the first height and the second height are different.

16. The impact absorbing material according to claim 1, wherein the frame includes a side wall transverse to the recipient body, and the side wall includes a geometric feature to alter the buckling mode of the frame.

17. The impact absorbing material according to claim 16, wherein the geometric feature comprises a notch or a slot.

18. The impact absorbing material according to claim 16, wherein the geometric feature comprises an offset of the side wall.

19. The impact absorbing material according to claim 16, wherein the geometric feature comprises a wave profile.

20. An impact absorbing structure comprising: impact absorbing material with at least one perimeter edge that includes an opening or irregularity, a recipient body, and a frame that is bonded to the recipient body, wherein the recipient body and the frame together encapsulate the impact absorbing material, the frame covers at least the one perimeter edge of the impact absorbing material, and the frame provides structural stiffness at the one perimeter edge that is consistent with stiffness of the impact absorbing material away from the opening or irregularity.

21. The impact absorbing structure according to claim 20, wherein the opening or irregularity is caused by processing the impact absorbing material.

22. The impact absorbing structure according to claim 20, wherein the opening or irregularity is caused by cutting the impact absorbing material.