U.S. patent application number 13/267590 was filed with the patent office on 2012-08-16 for helmet designs utilizing fluid-filled containers.
This patent application is currently assigned to Kinetica Inc.. Invention is credited to Alan Ira Faden, Thomas E. Twardowski, JR..
Application Number | 20120204329 13/267590 |
Document ID | / |
Family ID | 46635713 |
Filed Date | 2012-08-16 |
United States Patent
Application |
20120204329 |
Kind Code |
A1 |
Faden; Alan Ira ; et
al. |
August 16, 2012 |
HELMET DESIGNS UTILIZING FLUID-FILLED CONTAINERS
Abstract
Disclosed herein is a helmet structure for reducing kinetic
energy transmission. The helmet has a first layer configured as an
outside layer that serves as first contact with a source of kinetic
energy and a second layer having a substance that changes state to
transfer kinetic energy laterally with respect to the skull. The
substance has a threshold shear yield point wherein upon contact
with kinetic energy, if the threshold shear yield point of the
second layer is met, the layer will at least partially liquefy to
yield a liquid and flow to internal or external chambers. In one
embodiment, the helmet structure is reset after contact with
kinetic energy. The substance in the helmet changes state such that
the substance returns to its original state prior to contact with
kinetic energy and the substance returns to its original location
within the helmet structure.
Inventors: |
Faden; Alan Ira; (Baltimore,
MD) ; Twardowski, JR.; Thomas E.; (Morrisville,
PA) |
Assignee: |
Kinetica Inc.
Baltimore
MD
|
Family ID: |
46635713 |
Appl. No.: |
13/267590 |
Filed: |
October 6, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61442469 |
Feb 14, 2011 |
|
|
|
Current U.S.
Class: |
2/413 |
Current CPC
Class: |
B32B 27/20 20130101;
Y10T 428/1334 20150115; Y10T 428/24562 20150115; Y10T 428/24612
20150115; F41H 1/08 20130101; Y10T 442/637 20150401; B32B 5/16
20130101; B32B 3/26 20130101; Y10T 428/24992 20150115; C08L 23/02
20130101; A41D 31/285 20190201; A42B 3/063 20130101; A44B 18/0076
20130101; B32B 2262/10 20130101; Y10T 428/1334 20150115; B32B
2260/046 20130101; B32B 2264/10 20130101; B32B 3/08 20130101; B32B
2419/00 20130101; B32B 2571/00 20130101; F41H 1/04 20130101; F41H
5/007 20130101; A43B 13/189 20130101; Y10T 428/24512 20150115; Y10T
428/24661 20150115; B32B 5/22 20130101; B32B 2260/025 20130101;
B32B 2264/101 20130101; Y10T 428/31504 20150401; B32B 2307/56
20130101; A42B 3/064 20130101; B32B 2264/12 20130101; Y10T 428/252
20150115; B32B 7/02 20130101; Y10T 428/31678 20150401; Y10T 442/637
20150401; B32B 1/00 20130101; B32B 5/145 20130101; B32B 2605/00
20130101; B32B 5/30 20130101; Y10T 428/24983 20150115; B32B
2264/107 20130101; F41H 5/0492 20130101; Y10T 428/24 20150115; Y10T
428/25 20150115; B32B 3/12 20130101; B32B 2437/04 20130101; F41H
5/0428 20130101 |
Class at
Publication: |
2/413 |
International
Class: |
A42B 3/00 20060101
A42B003/00 |
Claims
1. A structure for reducing kinetic energy transmission, the
structure comprising: a first layer configured as an outside layer
that serves as first contact with a source of kinetic energy; a
second layer comprising a substance adjacent to the first composite
layer, the second layer changing state having a threshold shear
yield point, wherein upon interaction with the source, if the
threshold shear yield point of the second layer is met, the second
layer will at least partially liquefy to yield a liquid; and space
for the liquid in the second layer to flow.
2. The structure of claim 1, wherein a second layer is adjacent to
a third layer comprising a substance, the third layer changing
state having a threshold shear yield point, wherein upon
interaction with the source, if the threshold shear yield point of
the third layer is met, the third layer will at least partially
liquefy to yield a liquid.
3. The structure of claim 2, wherein the threshold shear yield
point of the second layer differs from the threshold shear yield
point of the third layer.
4. The structure of claim 2, wherein the threshold shear yield
point for the third layer is higher than the threshold shear yield
point for the second layer.
5. The structure of claim 1, wherein, if the threshold shear yield
point is met, the liquid will be ejected through an orifice to
space internal to the structure.
6. The structure of claim 1, wherein, if the threshold shear yield
point is met, the liquid will be ejected through an orifice to
space external to the structure.
7. The structure of claim 4, wherein space internal to the
structure is an internal storage chamber.
8. The structure of claim 6, wherein the internal storage chamber
is initially collapsed.
9. The structure of claim 6, wherein the internal storage chamber
expands as liquid flows into the chamber.
10. The structure of claim 1, wherein layers are bonded via at
least one internal storage chamber.
11. The structure of claim 2, wherein the boundary between the
second layer and the third layer is at least one of thick, thin,
rigid, flexible, interconnected and not interconnected.
12. The structure of claim 1, wherein the structure is reset after
contact with a source kinetic energy, the steps comprising:
changing the substance state of the liquid such that the liquid is
returned to its original state prior to contact with kinetic
energy; and returning the liquid to its original location within
the structure.
13. The structure of claim 12, wherein the liquid is returned to a
different location within the structure.
Description
PRIORITY
[0001] This application claims priority to U.S. Provisional Patent
Application No. 61/442,469, filed 14 Feb. 2011, the contents of
which are herein incorporated by reference in their entirety.
BACKGROUND
[0002] 1. Technical Field
[0003] The present disclosure relates to safety helmet design and
more specifically to reducing kinetic energy transmission after
various types of impacts utilizing fluid-filled containers.
[0004] 2. Introduction
[0005] In the United States, hundreds of thousands of people each
year are involved in athletic, cycling or motorcycle accidents
resulting in head injury. Much of the subsequent damage is caused
by the transmission of kinetic energy to the brain, as well as
shear forces. Although existing bicycle helmets reduce deaths and
brain injuries, current designs focus more on aesthetics and
aerodynamic performance than safety, in part due to market demands.
In addition, the helmet industry is essentially self-regulating and
therefore not likely to make significant improvements to helmets
unless the improvements prove to be cost-effective and/or markedly
more effective. Advances in polymeric materials provide novel
approaches to helmet design and construction. Significant
improvements in viscoelastic (active) dampening, low loss
elastomers, and gradient rigidity materials have already given rise
to enhanced athletic equipment and protective gear.
[0006] Crashes and impacts to the head in sports often result in
head trauma due to the rigid construction of helmets. The severe
consequences of concussive brain injuries have become increasingly
recognized in many sports, particularly recently in professional
football and ice hockey. It has also long been recognized that
boxers often suffer significant cognitive decline, even in
non-professional contests where protective head gear is required.
Professional and college sports teams would likely switch to a new
type of helmet, if such a design were clearly shown to reduce
post-traumatic brain injury.
[0007] In addition to athletics, improved helmet designs have
applications in the military. Brain injury is the leading cause of
disability for military personnel deployed in Iraq and Afghanistan.
Although military helmet designs have improved in recent years,
they are intended primarily to prevent missile/shrapnel
penetration, and do little to reduce the energy transmitted to the
brain, which is a major contributor to subsequent disability. The
mechanisms of traumatic brain injury due to blast forces remain
unclear, but brain injuries related to explosives are by far the
most common cause of death and disability in Iraq and Afghanistan.
Experimental evidence indicates that the use of advanced body armor
may contribute to the increase in brain injuries, both by
protecting against death from injury to major non-brain organs such
as the lung, and possibly by transmitting kinetic energy through
larger blood vessels to the brain.
[0008] Existing helmet designs do not adequately address the
critical problem: kinetic energy from the impact is transmitted to
the brain through primary, secondary and tertiary
mechanisms--resulting in concussion, brain damage and even
death.
SUMMARY
[0009] Additional features and advantages of the disclosure will be
set forth in the description which follows, and in part will be
obvious from the description, or can be learned by practice of the
herein disclosed principles. The features and advantages of the
disclosure can be realized and obtained by means of the instruments
and combinations particularly pointed out in the appended claims.
These and other features of the disclosure will become more fully
apparent from the following description and appended claims, or can
be learned by the practice of the principles set forth herein.
[0010] Disclosed is a structure for improved safety helmet designs
utilizing fluid-filled containers that reduce the kinetic energy
induced by impact and rotational forces. The safety helmet will
better protect the brain by limiting both direct missile trauma and
secondary kinetic effects. The safety helmet has a first layer that
comes in direct contact with an object and a second layer having a
substance that changes state. Optionally, the helmet can have a
third or more layers having a substance that changes state. The
second layer and optional additional layers each have a threshold
shear yield point wherein upon contact with kinetic energy, if the
threshold shear yield point of a layer is met, the layer will at
least partially liquefy to yield a liquid and flow into pockets of
space. Subsequent threshold shear yield points in a layer can
differ from previous threshold shear yield points and become
progressively higher in shear yield force required to cause liquid
to flow. The liquid is ejected through an orifice and flows to
internal holding chambers or space external to the helmet. In one
embodiment, the helmet can be reset such that after an impact
causing liquid to flow, the substance state of the liquid is
changed such that the liquid is returned to its original state
prior to contact with kinetic energy. In another embodiment,
subsequent layers can contain both foam and liquid dispersion
elements. The foam can be composed of any suitable compressible
material formulated to have a range of mechanical compression
strength.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] In order to describe the manner in which the above-recited
and other advantages and features of the disclosure can be
obtained, a more particular description of the principles briefly
described above will be rendered by reference to specific
embodiments thereof which are illustrated in the appended drawings.
Understanding that these drawings depict only exemplary embodiments
of the disclosure and are not therefore to be considered to be
limiting of its scope, the principles herein are described and
explained with additional specificity and detail through the use of
the accompanying drawings in which:
[0012] FIG. 1 illustrates a side view of a safety helmet with
layers having fluid-filled containers;
[0013] FIG. 2 illustrates an exemplary safety helmet method
embodiment;
[0014] FIG. 3 illustrates a side view of safety helmet layers
having substance-filled bubbles;
[0015] FIG. 4 illustrates a side view of safety helmet layers
having substance-filled containers;
[0016] FIG. 5 illustrates a side view of safety helmet layers
having substance-filled bubbles and compressible foam
structures;
[0017] FIG. 6 illustrates a side view of safety helmet layers
having substance-filled containers and compressible foam
structures;
[0018] FIG. 7 illustrates a side view of safety helmet layers
having substance-filled bubbles and internal holding chambers;
[0019] FIG. 8 illustrates a side view of safety helmet layers
having substance-filled containers and internal holding
chambers;
[0020] FIG. 9 illustrates a side view of safety helmet layers
having substance-filled bubbles and an external orifice;
[0021] FIG. 10 illustrates a side view of safety helmet layers
having substance-filled containers and an expandable sac; and
[0022] FIG. 11 illustrates an exemplary safety helmet reset method
embodiment.
DETAILED DESCRIPTION
[0023] Various embodiments of the disclosure are discussed in
detail below. While specific implementations are discussed, it
should be understood that this is done for illustration purposes
only. A person skilled in the relevant art will recognize that
other components and configurations may be used without parting
from the spirit and scope of the disclosure.
[0024] The present disclosure addresses the need in the art for
improved safety helmet designs. A safety helmet design is disclosed
that reduces both the kinetic energy induced by impact and
rotational forces. A brief introductory description of safety
helmets is provided followed by a discussion of mathematical
modeling used to optimize helmet layer design. A more detailed
description of improved safety helmet designs utilizing
fluid-filled containers will then follow. While a helmet is used in
the example embodiment, the layering principles can also be applied
to a wall, body armor, a vehicle, or any protective layer that
could use the principles disclosed herein. Accordingly, various
embodiments of the disclosure include a wall having a series of
layers and disclosed herein, body armor having the series of layers
as well as a vehicle having an outer covering including the series
of layers disclosed herein. The disclosure proceeds to discuss
primarily a helmet embodiment.
[0025] Traditional design for both military and recreational
helmets includes a rigid outer material to prevent penetration of
the skull and brain, as well as some type of lining material to
absorb some of the shock and to enhance comfort. However, few
modern designs adequately address the critical problems leading to
brain damage: kinetic energy transmitted to the brain and rotation
(particularly axial acceleration/deceleration).
[0026] By using novel materials and composites that are organized
upon mathematically defined principles to maximize the relative
dissipation of transmitted kinetic energy, as well as to limit
rotational components, development of a new design for helmets and
body armor should markedly reduce posttraumatic brain injuries from
various types of insults and impacts. The initial target outcome is
a set of disruptive technological advances in helmet design that
improve the survivability of impact trauma to the head for use in
military and civilian applications.
[0027] Stacks of various materials can be used in experiments to
determine the abilities of the various materials to dissipate and
spread out external forces. Mathematical modeling can be used to
extrapolate from experimental data to the behaviors of actual
helmets constructed of the various material stacks by constructing
local models and constructing local-to-global models.
[0028] A local model refers to a mathematical model of a single
cylindrical stack. Such a model allows calculation, based upon an
exogenous force exerted on the top surface of the stack, the amount
of force transmitted to a particular point either internal to the
stack or on the surfaces of the stack.
[0029] Consider a particular stack on which is imposed a
rectangular coordinate system (x, y, z). Further, suppose that the
vector function F(x, y, z) represents the magnitude of the force
experienced at point (x, y, z) of the stack from a known exogenous
impact on the stack. Yet further, suppose that experimental data
results in measurement of the value of F(x, y, z) at N particular
stack points, say
(x.sub.i,y.sub.i,z.sub.i)(i=1, . . . ,N)
[0030] Based on the geometric description of the stack, the
properties of the materials composing the stack, and an analysis of
the physics of force transmission through the stack, the general
mathematical form of the function F(x, y, z), up to a set of
parameters. For example, in a simple case, the function might have
the form:
F(x,y,z)=ax+by+cz
a linear function, involving three parameters a, b, c, which must
be determined. Generally, the experimental data results in an
over-determination of a, b, c, so that no set of values for a, b, c
exactly matches the experimental data. The best that can be done is
to determine the values of a, b, cis some "optimal fashion"--that
is, so that some error function is minimized. The most common such
error function is the sum of squares function:
E ( a , b , c ) = i = 1 N ( F ( x i , y i , z i ) - ax i - by i -
cz i ) 2 ##EQU00001##
[0031] In case F(x, y, z) is linear, as in the above example, the
determination of a, b, c is just the well-known problem of linear
regression analysis. However, in actual practice, the function F
may involve more or fewer parameters and is generally highly
non-linear, especially for materials with complicated behaviors. In
such instances, the error function E is a much more complex
function and the problem of minimizing the sums of the squares of
the errors is a non-linear optimization problem, which we have had
considerable experience addressing.
[0032] In order to proceed from the local models to actual helmets
configurations, an accepted technique from finite-element analysis
can be used, namely subdividing a helmet configuration into a large
number of elemental configurations, the analysis of each of which
can be handled by a local model, and then analyzing the interaction
among adjacent elemental configurations.
[0033] For the case of the helmet configurations, the surface of
the helmet can be divided into a triangular lattice. Corresponding
to each triangle, a triangular prism can be obtained by a radial
cut into the helmet along each side of the triangle. Each
triangular prism can be regarded as embedded within a circular
stack and thus subject to the analysis of a local model, which
would allow an assessment of the transmission of forces between
adjacent prisms in response to an exogenous force anywhere on the
helmet surface.
[0034] Of particular interest would be the proportion of the
initial energy which is transmitted to the bottom of the prisms,
the maximum forces transmitted, and their respective locations.
This information can be used to compare the effectiveness of
various material stacks and helmet configurations.
[0035] Having disclosed some mathematical modeling used to optimize
helmet layer design, the disclosure now turns to FIG. 1 and FIG. 2.
FIG. 1 and FIG. 2 illustrate an improved safety helmet design that
reduces both the kinetic energy induced by impact and rotational
forces. The safety helmet will better protect the brain by limiting
both direct missile trauma and secondary kinetic effects. The
safety helmet 102 receives contact of an object that transfers
kinetic energy to a first layer 104, 202. The first layer can be a
composite composed of a discrete reinforcement and a continuous
binder, such as a polymer, or can be any other material such as
Kevlar or steel that can spread kinetic energy A polymer is a large
molecule composed of repeating structural units, the units
typically connected by covalent chemical bonds. Polymers are both
natural and synthetic materials with varying properties. Natural
polymeric materials include shellac, and cellulose and synthetic
polymers include neoprene, PVC, silicone and more. The discrete
reinforcement is composed of particles that can have differing
sizes, shapes and can be different materials such as ceramic or
glass. The reinforcement is at least one particle and has particles
with a size greater than one micron. The continuous binder binds
particles to one another to yield the composite in the first
composite layer of the safety helmet.
[0036] The helmet uses a second layer having a substance that
changes state to transfer kinetic energy laterally with respect to
the skull 204. Optionally, the helmet can have a third or more
layers having a substance that changes state. The third layer is
adjacent to the second layer, the fourth layer is adjacent to the
third, and so on. The second layer 106 and optional additional
layers each have a threshold shear yield point wherein upon contact
with kinetic energy, if the threshold shear yield point of a layer
is met, the layer will at least partially liquefy to yield a liquid
and flow into pockets of space. A threshold shear yield point is
the point at which a substance changes state. Different Bingham
liquid plastics or other liquids having similar properties can be
used in the helmet. Bingham plastic liquids are characterized as
having no flow, or solid behavior, when the applied shear force is
below a threshold value. Above this threshold, the liquid will have
a shear thinning behavior, or a thick liquid flow.
[0037] Subsequent threshold shear yield points in a layer can
differ from previous threshold shear yield points and become
progressively higher in shear yield force required to cause liquid
to flow. For example, a third layer can have one or more threshold
shear yield points higher than a second layer, and a fourth layer
can have one or more threshold shear yields point higher than a
third layer. Upon impact with a source of kinetic energy, layers
can partially or completely liquefy to reduce the impact that a
head receives. Alternately, subsequent threshold shear yield points
in a layer can be the same or lower as previous threshold shear
yield points.
[0038] FIG. 3 and FIG. 4 illustrate side views of safety helmet
layers. The first layer is an outside layer 302, 402 that comes
into contact with an object. The second layer 304, 404 adjacent to
a respective first layer 302, 402 can consist of bubbles 306 or
other containers 406 filled with a substance, such that when a
threshold shear yield point for the layer is met, liquid flows from
the bubbles 306 or other containers 406 to displace force laterally
with respect to the skull. Liquid can be ejected through an orifice
and flow to internal space such as internal storage chambers 108,
408 or can flow to space external to the helmet 110. The internal
storage chambers 108 can be initially collapsed 110 and can expand
as the liquid flows into the chambers 112 or chambers can be rigid.
Helmet layers can be bonded by at least one storage chamber. Layers
of phase changing liquid plastics can be separated by storage
layers that can serve as expandable binding layers. Boundaries
between layers can be thick, thin, rigid, flexible, interconnected,
not interconnected or any combination thereof. The substance-filled
containers can be made from any impermeable plastic, for example
polypropylene. The liquids can be made from suitable liquids with a
suitable range of formulation. Examples include silicone oils,
polyvinyl alcohol mixtures with cross-linking, polyethylene oxides
or other synthetic polymers, and mixtures with diluents including
water and silicone oils.
[0039] In one embodiment, second and additional layers in a
structure can contain both foam and liquid dispersion elements. The
foam can be composed of any suitable compressible material, for
example polyurethane, formulated to have a range of mechanical
compressible strength. A second layer can compress and have
expansion structures such that at least one expansion structure
expands into an expansion zone in the second layer to transfer
kinetic energy upon impact. Each expansion structure has a first
base configured to be adjacent to the first layer and a first tip,
and a second base configured to be adjacent to a third layer and a
second tip, such that the first tip is in contact with the second
tip in a mirrored configuration. For example, a helmet can have a
first composite layer that receives contact of an object that
transfers kinetic energy and a second layer having a substance that
changes state to transfer kinetic energy laterally with respect to
the skull and can have expansion structures that expand into an
expansion zone in the second layer. The second layer can have
multiple foam structures with graded physical properties. The
graded physical properties can be created from the chemical
composition of the foam, by incorporation of different sizes of
reinforcements, or by physical shaping of the foam. Subsequent
layers can contain any number of foam dispersion elements in any
location within the layers. Each subsequent layer can contain
differing sizes of reinforcements, physical shaping, etc. from at
least one other of the layers.
[0040] FIG. 5 and FIG. 6 illustrate structures having a second
layer with both liquid and foam dispersion elements. A first layer
502, 602 is an outside layer that comes into contact with an
object. A second layer 504, 604 has both liquid and foam dispersion
elements. A second layer 504 can contain graded foam structures 506
and liquid-filled bubbles 508. When the threshold shear yield point
for the second layer is met, the bubbles pop causing liquid to flow
into empty internal space 510 surrounding the bubbles and the foam
compresses and expands into empty space 510 to absorb shock from an
impact. A second layer 604 can contain graded foam structures 606
having elements with differing shapes and liquid-filled containers
608. When the threshold shear yield point for a second layer is
met, liquid-filled containers can open, causing liquid to flow into
empty space 610 surrounding the containers and foam can compress
and expand into empty space 610 to absorb shock. Alternately,
liquid can flow from containers 612 into an expandable sac that
expands when liquid flows 614.
[0041] FIG. 7 illustrates fluid from popped bubbles flowing into
internal holding chambers and FIG. 8 illustrates fluid from
containers flowing into internal holding chambers. A first layer
702, 802 is an outside layer that comes into contact with an
object. A second layer can have liquid dispersion elements. A
second layer 704 can contain liquid-filled bubbles 706 that can pop
when the threshold shear yield point for the layer is met. Liquid
can flow into empty space surrounding the bubbles 708 and can flow
into an internal storage chamber 710. A second layer 804 can
contain liquid-filled containers 806 that can open for liquid to
flow into an internal storage chamber 808 when the threshold shear
yield point for the layer is met.
[0042] FIG. 9 illustrates fluid from popped bubbles flowing into an
external orifice and FIG. 10 illustrates fluid from opened
containers flowing into an external orifice. A first layer 902,
1002 is an outside layer that comes into contact with an object. A
second layer 904, 1004 has liquid dispersion elements. A second
layer 904 contains liquid-filled bubbles 906 that can pop when the
threshold shear yield point for the layer is met. The liquid can
flow into an orifice 908 to external space by flowing through a
first layer 902 or by any other means. Additionally, liquid can
flow into internal storage chambers 910 when the threshold shear
yield point for a layer is met. A second layer 1004 can contain
liquid-filled containers 1006 that can open when the threshold
shear yield point for the layer is met and can have graded foam
structures 1008 that compress upon impact with an object. Liquid
can flow to space external to a helmet using an orifice 1010 an can
flow through a first layer 1002 or by any other means. Liquid can
flow into an expandable sac 1012 that is external to the second
layer and/or helmet structure. Alternately, liquid can flow into an
expandable sac internal to the helmet 1014 or liquid can flow to
expandable sacs both internal 1014 and external 1012 to the helmet.
The expandable sac 1012 can expand when liquid flows into the sac
and can serve as a visual indicator to a helmet wearer or to others
the severity of an impact. Any combination of fluid-filled bubbles,
fluid-filled containers, fluid dispersion techniques and
compressible foam for slowing or redirecting the transfer of force
away from the head from an impacting object are contemplated.
[0043] In one embodiment, the helmet can be reset such that after
an impact causing liquid to flow, liquid flows from a container or
other source back to its initial location or a new location within
the helmet. FIG. 11 illustrates resetting a helmet structure after
impact. After an impact, another device can be used or the helmet
itself can reset such that liquid returns to its original state
prior to contact with an object that transfers kinetic energy 1102
and returns the liquid to its original location within the
structure 1104. Alternately, after an impact the liquid returns to
its original state prior to contact with kinetic energy and the
liquid returns to another location within the structure. For
example, after an impact a helmet with an external expandable
fluid-filled sac is reset such that the fluid flows from the sac
back into one or more containers through an orifice or other means.
Alternately, after an impact a helmet with an external expandable
fluid-filled sac is reset such that fluid flows from the sac back
into one or more empty containers although the fluid was originally
stored in bubbles. This more complex helmet is designed to handle
multiple impacts appropriate for football helmets, motorcycle
helmets and military helmets.
[0044] The various embodiments described above are provided by way
of illustration only and should not be construed to limit the scope
of the disclosure. Thus, for a claim that recites a structure that
deflects and spreads kinetic energy, the structure could apply in
any application disclosed herein (vehicle, helmet, body armor,
building protection, etc.) as well as other structures not listed.
Those skilled in the art will readily recognize various
modifications and changes that may be made to the principles
described herein without following the example embodiments and
applications illustrated and described herein, and without
departing from the spirit and scope of the disclosure.
* * * * *