U.S. patent application number 11/762053 was filed with the patent office on 2008-12-18 for method and apparatus for protecting against ballistic projectiles.
This patent application is currently assigned to ENERGY SCIENCE LLC. Invention is credited to Eric John Atherton, Terance Jbeili, Christopher Charles Payton.
Application Number | 20080307553 11/762053 |
Document ID | / |
Family ID | 40130963 |
Filed Date | 2008-12-18 |
United States Patent
Application |
20080307553 |
Kind Code |
A1 |
Jbeili; Terance ; et
al. |
December 18, 2008 |
Method And Apparatus For Protecting Against Ballistic
Projectiles
Abstract
A composite material comprising a multitude of masses and fibers
supported on a flexible substrate arranged in a manner to absorb
energy from a ballistic projectile and thereby protect persons or
property from ballistic injury or damage. An array of small, tough
disc-like masses are suspended in a three dimensional cradle of
high-tensile elastomeric fibers such that energy from an incoming
ballistic projectile is first imparted to one or more masses and
the motion of the masses are restrained by tensile strain of
elastomeric fibers substantially in the direction of travel of the
incoming projectile. The projectile is eventually decelerated to
harmless velocity through a combination of transfer of momentum to
the masses and the elastic and plastic tensile deformation of the
fibers. One or more layers of the composite material can be
assembled to form body protective armor ("bullet-proof vest") or
property protective armor, the number and characteristics of the
layers being adjusted according to the specific ballistic threat
anticipated.
Inventors: |
Jbeili; Terance; (Missouri
City, TX) ; Payton; Christopher Charles; (Missouri
City, TX) ; Atherton; Eric John; (Oxford,
GB) |
Correspondence
Address: |
ENERGY SCIENCE, LLC
31 SULLIVANS LANDING
MISSOURI CITY
TX
77459
US
|
Assignee: |
ENERGY SCIENCE LLC
Sugar Land
TX
|
Family ID: |
40130963 |
Appl. No.: |
11/762053 |
Filed: |
June 12, 2007 |
Current U.S.
Class: |
2/2.5 ;
89/36.02 |
Current CPC
Class: |
F41H 5/0471 20130101;
F41H 5/0428 20130101; F41H 5/0457 20130101 |
Class at
Publication: |
2/2.5 ;
89/36.02 |
International
Class: |
F41H 1/02 20060101
F41H001/02; F41H 5/02 20060101 F41H005/02 |
Claims
1. A ballistic projectile defeating protective armor designed to
protect persons and property comprising a plurality of small masses
and a framework of fibers which partially restrain movement of said
masses under ballistic load.
2. The armor of claim 1 where said fibers are arranged around the
masses in a multi-dimensional framework, where the arrangement of
said framework is central to the function of the armor.
3. The armor of claim 1 where the arrangement of the fibers is such
that said fibers may elongate in tension in a direction
substantially corresponding to the direction of the ballistic
projectile prior to impact on the armor.
4. The armor of claim 1 which imparts force by the said mass or
masses first impacted ballistically to adjacent masses through a
combination of compressive force in the elastomeric material and
tensile force in the reinforcing fibers.
5. The armor of claim 2 where the fibers are arranged in a
three-dimensional framework around each individual mass.
6. The armor of claim 2 where at least part of the direction of the
weave of the fibers around the masses is substantially in the
direction aligned with the anticipated ballistic threat.
7. The armor of claim 2 where at least part of the direction of the
weave of the fibers is in a direction substantially normal to the
local plane of the material.
8. The armor of claim 2 where the fibers are wound or woven
alternately in regular or random or pseudo random fashion around or
about masses.
9. The armor of claim 2 where said fibers are first aligned
substantially in the x and y directions substantially normal to the
direction of the anticipated ballistic impact and are locally
rearranged upon ballistic impact such that the displacement of one
mass under ballistic load relative to adjacent masses causes a
rearrangement of the 3D geometry from the rest geometry to a
geometry where tensile elongation of said fibers occurs
substantially in the direction of the direction of the ballistic
load.
10. The armor of claim 2 where under ballistic load the geometry of
the fibers and masses dynamically rearrange to a 3D geometry of
fibers and masses prior to the ultimate tensile stress being
attained in all said fibers local to the ballistically impacted
mass.
11. The armor of claim 2 which is constructed to be flexible to
facilitate elastic flexing of said armor material at a bend rate of
20 degrees or more from the neutral position per linear foot of
material.
12. The armor of claim 2 where the dimensions and material
properties of the masses are calculated to optimally retard one or
more specific ballistic threats, such as rifle bullets, cannon
shells, or artillery shells of specified caliber and
performance.
13. The armor of claim 2 where the dimensions and material
properties of the masses are calculated to optimally retard one or
more specific ballistic threats, such as rifle bullets, cannon
shells, or artillery shells of specified caliber and performance
and prevent punch through of the mass by the specific threat
projectile.
14. The armor of claim 2 combined with at least one layer of woven
ballistic cloth material.
15. The armor of claim 2 where retardation of the ballistic
projectile is achieved through transfer of kinetic energy from the
ballistic projectile to one or more masses.
16. The armor of claim 2 where retardation of the ballistic
projectile is achieved through elastic or plastic elongation of
fibers which are or become arranged substantially in the direction
normal to the local plane of the material.
17. The armor of claim 2 where retardation of the ballistic
projectile is achieved through elastic or plastic elongation of
fibers substantially in the direction of the projectile prior to
impact.
18. The armor of claim 2 where the retardation of the ballistic
projectile is achieved through a combination of the transfer of
kinetic energy to masses and the elastic or plastic elongation of
fibers substantially in the direction of the projectile prior to
impact.
19. The armor of claim 2 where the retardation of the ballistic
projectile is achieved through a combination of the transfer of
kinetic energy to masses and the elastic or plastic elongation of
fibers substantially in the direction of the projectile prior to
impact and deformation of the masses and solid material directly in
contact with the masses and or fibers.
20. The armor of claim 2 where adjacent masses are configured in
tessellating shapes.
21. The armor of claim 2 where the tensile strength of the material
of the fibers is greater than 400 Mega Pascals.
22. The armor of claim 2 where the fibers are made from more than
one tensile strength material.
23. The armor of claim 2 where the masses are constructed of one or
more of the following ballistic shear resistant materials: metal,
ceramic, ceramic composite, fiber composite, and or quartz
composite.
24. The armor of claim 2 where the mass of an individual mass is
less than one point three times the mass of the anticipated threat
projectile.
25. The armor of claim 2 where the mass and size of said mass are
small enough so that the mass will accelerate with an impacting
ballistic projectile and not be punctured by said projectile and
the mass imparts a retarding force on the projectile.
26. The armor of claim 2 where the masses are further supported by
an elastomeric or plastic material which deforms compressively as a
result of ballistic impact on one or more masses.
27. The armor of claim 2 where the armor material is encapsulated
in elastomeric or plastic material by a process of injection or
molding or vulcanizing.
28. The armor of claim 2 where the cross section of the masses
orthogonal to the nominal direction of the ballistic threat is
smaller in at least one dimension than the diameter of the
anticipated ballistic projectile.
29. The armor of claim 2 where the fibers are woven into a fabric
or cloth and the masses are interwoven into said fabric or
cloth.
30. The armor of claim 2 where said masses are each manufactured of
one or more component parts and enclose said fibers wholly or
partially so as to effectively restrain and limit relative motion
between said fiber and said masses.
31. The armor of claim 2 where the motion of a mass is restrained
by the framework of fibers, and said restraining imparts a
retarding force.
32. A bullet proof vest constructed of one or more layers of the
armor of claim 2.
33. A bullet proof vest constructed of two or more layers of the
armor of claim 2 where said layers are separated by a layer of
elastomeric material which deforms compressively under ballistic
load.
34. A bullet proof vest constructed of one or more layers of the
armor of claim 2 and one or more layers of conventional woven
ballistic fiber cloth.
35. The armor of claim 1 where the masses have smooth and rounded
surfaces in contact with the fibers so that the fibers may slide
locally over the surface of the masses during ballistic load.
36. The armor of claim 35 where a solid spacer of plastic material
is placed between the fibers and the masses, where said plastic
material deforms and flows under ballistic loading.
37. The armor of claim 1 comprising multiple layers of a plurality
of said masses and three dimensional framework of fibers which
restrain movement of the masses under ballistic load.
38. The armor of claim 37 where the mass of the individual masses
in the layer first impacted by the ballistic projectile is less
than the mass of the individual masses in subsequently impacted
layers.
39. The armor of claim 2 where upon ballistic impact of a ballistic
projectile on a mass, said mass moves by a limited amount in a
direction which is substantially the direction of travel of the
ballistic projectile prior to impact.
40. The armor of claim 39 where the motion of the mass causes
tensile stress in the fibers supporting said mass.
41. The armor of claim 40 where said tensile stress causes tensile
elongation of the fibers at least part of said elongation is
substantially in the direction of the motion of the mass.
42. The armor of claim 41 where the tensile elongation of some or
all of said fibers causes energy to be absorbed.
43. The armor of claim 41 where the tensile elongation of some or
all of said fibers results in tensile failure of some or all of
said fibers.
44. The armor of claim 2 where the tensile stress imparted in the
fibers by the motion of the mass or masses first impacted by a
ballistic projectile causes a force to be imparted to one or more
adjacent masses.
45. The armor of claim 44 where the force imparted by said first
impacted mass or masses to said adjacent masses is imparted
substantially by the tensile stress in the supporting fibers
substantially in the direction of motion of the first impacted mass
or masses.
46. The armor of claim 44 where the summed mass of the plurality of
said masses which are adjacent to and directly mechanically coupled
by said fibers to a mass which is first impacted by a ballistic
projectile, or to masses which are first impacted by a ballistic
projectile if more than one mass is directly in the path of said
projectile, is greater than twice the mass of the anticipated
threat projectile.
Description
BACKGROUND--FIELD OF INVENTION
[0001] The present invention is in the field of protection of
persons or property against kinetic missiles such as firearm
bullets, specifically contemplated is application as ballistic
body-armor (or "bullet-proof vests") and also the protection of
vehicles, including aircraft, and sensitive property such as
communications equipment by providing flexible, light-weight
protection against small arms and high-velocity rifle bullets.
BACKGROUND--DESCRIPTION OF PRIOR ART
[0002] The mechanical challenges of arresting a high velocity
projectile have focused prior and current art on materials with
extreme mechanical properties. The practical problem is that the
kinetic energy of a high velocity ballistic projectile is high
while the cross section is small, resulting in a very high specific
energy upon initial impact. Under such conditions, inertial forces
typically dominate over mechanical properties and the projectile
will tend to punch through a layer of material as the localized
stresses greatly exceed the shear, compressive and tensile
strengths for most materials. As a result current art is typically
focused on materials such as strong metals, ceramics and ballistic
polymer fibers which possess extreme mechanical properties, such as
shear modulus, tensile modules, and fracture toughness. Current art
focuses on placing sufficient amount of suitable material in the
path of the projectile, so that the projectile is stopped. In some
cases the art (Yeshuin et al) uses masses of glass or ceramic to
deflect the path of the projectile so that it may be more easily
arrested by ballistic fibers.
[0003] Ballistic protection or armor is typically one of three
types: (i) solid material plate, (ii) layered ballistic fiber, or
(iii) composite construction of hard materials supported by
ballistic fiber. Each of these types has certain practical
advantages and practical limitations.
[0004] Solid plate material is typically either a tough metal
plate, or a hard ceramic plate, or a combination of metal, ceramic
and sometimes composite fiber or solid polymer. Ceramic materials
used as ballistic protective plates include titanium nitride,
aluminum nitride, silicon carbide. Metals used include hard or
ductile steels, hard (e.g. type 7075-T6) or ductile (e.g. type
5053) aluminum alloys and titanium. Solid plate designs are
inflexible, and often heavy. Composite materials include glass or
polyaramide fibers in epoxy resin. Solid polymer materials include
ultra-high molecular weight polyethylene (UHMW PE). Information on
these materials and their application to ballistic armor is widely
available in the literature, though specific details are not always
accessible due to proprietary nature of some materials. Example
information on commercial ceramic materials for ballistic use has
been summarized in "Improving Ceramic Armor Performance" January
2006, Cerradyne Ltd. An overview of U.S. and international metallic
armor materials and specifications can be found at web page
www.niistali.ru/science/br_stali_en.htm dated May 2007.
[0005] Practical use in protective body armor of solid plate
material is commonly restricted to small critical protection areas,
such as over the heart, used in combination with layered ballistic
fiber vests. "Selection and Application Guide to Personal Body
Armor" NIJ Guide 100-01, U.S. Dept of Justice, November 2001,
provides historical background on various types of protective body
armor (ballistic and non-ballistic) and guide to selection and use
of personal protective armor of various types.
[0006] Ballistic fiber is a descriptive term applied to a number of
polymer fibers which have mechanical characteristics suited to
projectile deceleration and capture. Ballistic fiber strands can be
built up into cloths by weaving or into felts. Ballistic fibers are
typically either polyamide or polyethylene polymers. Examples are
of Kevlar 129 and Kevlar 49 (both Trade Mark, E.I. Du Pont),
Spectra 900 and Spectra 1000 (both Trade Mark, Allied Chemicals)
and Dyneema (Trade Mark DFS Industries, Holland). The currently
commercially available ballistic fibers are well known to one
practiced in the art. The application of Kevlar to bullet proof
body armor is widely described in United States patents, including
U.S. Pat. No. 5,392,686, which describes an extendable flexible
bullet proof shield for persons constructed using ballistic fiber
material and a transparent solid plastic bullet proof material,
U.S. Pat. No. 5,370,035, which describes a bullet proof curtain for
use in vehicles constructed using ballistic fiber material, and the
like. Further description is also provided in publications by fiber
manufacturers, such as, "Kevlar Tech Guide" DuPont, April 2000.
U.S. Pat. No. 6,705,197, Neal et al, describes a bullet proof vest
comprising an outer layer of woven polyaramide fiber and a second,
inner layer of polyethylene woven fiber, which more effectively
protects against a bullet by utilizing the respective mechanical
properties of polyaramide and polyethylene layers appropriate to
the first and later stages of bullet retardation by the double
layer material. Recent developments in fiber weaving have made
cloths with three dimensional weaves available, which can be formed
into composite materials. U.S. Pat. No. 5,085,252, Mohammed M et al
"Method of Forming Variable Cross-Sectional Shaped Three
Dimensional Fabrics" described a way of constructing such
materials. Application of three dimensional weave composite fiber
materials to ballistic armor is described in "Ballistic Resistance
of 2D and 3D Woven Sandwich Composites" Journal of Sandwich
Structures and Materials 2007; 9; 283 Grogan et al, referenced
below. Transonite.TM. (Martin Marietta, Inc) is material which
incorporates layers and trusses of three dimensional weave fiber
composite around an expanded foam core to provide a lightweight
blast resistant panels for buildings and structures.
[0007] Ballistic fiber vests are generally effective at providing
protection against standard hand gun bullets, but are not effective
protection against high velocity rifle bullets. For this reason,
portions of solid material plates, so called "trauma plates" are
normally added as an outer layer to provide additional protection
to vital organs.
[0008] Various designs for bullet proof materials have been
proposed based on combining smaller pieces of solid material with
one or more layers of woven ballistic fiber in order to provide a
flexible garment which benefits from the ballistic protection
properties of both solid materials and the layered ballistic fiber.
In some designs, a final inner layer of relatively soft
elastomeric, energy absorbing material is used as a final layer
where penetration protection has been provided by outer layers.
[0009] "Ballistic Resistance of 2D and 3D Woven Sandwich
Composites" Journal of Sandwich Structures and Materials 2007; 9;
283 Grogan et al, further describes a ballistic protective armor
comprising layers of compliant ballistic woven fiber and a layer of
ceramic, or other hard strike face impact resisting material. The
design thus explained further utilizes a multidimensional weave
("3D weave") ballistic fabric to improve the mechanical properties
of the fabric. It is noted here that in contrast to the present
invention, the function of the ceramic layer and the fiber layers
thus described are essentially separate and or sequential, and
furthermore the concept and function of kinetic mass retardation is
not integral to that design.
[0010] U.S. Pat. No. 4,483,020, Dunn describes a bullet proof vest
comprising interlocking plates together with layer of ballistic
fiber cloth which provides a flexible vest construction.
[0011] U.S. Pat. No. 4,660,223, Fritch et al, describes a flexible
protective garment constructed of titanium plates of area ranging
from approximately 5.08 to 15.24 centimeters (2 inches to 6 inches)
square and approximately 1 mm thick, bonded into a several layers
of Kevlar fiber felt. This design is suited to defeating knife
attacks and low energy bullets.
[0012] U.S. Pat. No. 5,134,725 Yeshrun et al, describes a flexible
ballistic protective garment material constructed using small
axi-symmetrical or centro-symmetrical bodies of glass or ceramic
material together with one or more layers of ballistic fiber
material, the function of the bodies being to deflect an incoming
ballistic projectile so that it may be retarded by the ballistic
fiber layer(s). The bodies of glass or ceramic are not supported
within or integral to, an individual layer of ballistic fiber, nor
are successive layers of the glass ceramic bodies separated by a
layer of ballistic fibers.
[0013] U.S. Pat. No. 5,200,256, Dunbar describes a layered material
construction comprising an outer, i.e. first impacted, layer of
woven ballistic fiber impregnated with resin, followed by one or
more intermediate layer of metal mesh, typically stainless steel,
followed by a final layer of elastomeric foam material. The
compound material provides light-weight ballistic protection for
vehicles and aircraft.
[0014] U.S. Pat. No. 6,745,661, Neal et al, and U.S. Pat. No.
6,035,438 Neal et al, both describe a bullet proof vest constructed
with an overlapping two dimensional array of compound ceramic and
fiber discs, enclosed on either side by a layer of woven ballistic
fiber, and backed by a further layer of ballistic fiber, followed
by a further layer of soft woven ballistic fiber. The possibility
of a multiplicity of similarly constructed layers is also
disclosed.
[0015] The disclosure of each of the above mentioned United States
patents is hereby incorporated by reference into this
specification. These patents, together with the commercial
references mentioned provide an overview of the prior and current
art in small arms ballistic protection, including current practice
in flexible and solid body designs for ballistic body armor.
Standards for Ballistic Protection.
[0016] Performance standards for ballistic protection are issued by
various national and international agencies, including CRISAT,
which is short for Collaborative Research Into Small Arms
Technology, and is the EU-Nato standard in the manufacture of
military equipment. The CRISAT Target is defined as a 1.6 mm
Titanium plate supplemented by 20 layers of Kevlar. Weapons are
measured against this standard in respect to its ability to
penetrate it, and protective equipment is manufactured to adhere to
it. Both the Underwriters Laboratories (UL Standard 752) and the
United States National Institute of Justice (NIJ Standard 0101.04)
have specific performance standards for bullet resistant vests used
by law enforcement. These standards relate to the type of
projectile to be blocked, and the amount of deformation allowable
at the protected, or inside, side of the vest.
TABLE-US-00001 References Cited 4,483,020 November 1984 Dunn A.
4,660,223 April 1987 Fritch D. 5,085,252 February 1992 Mohammed M
et al 5,134,725 August 1992 Yeshurun et al 5,200,256, April 1993
Dunbar C. 5,392,686 December 1993 Sankar W 5,370,035 December 1994
Madden, Jr. J. 6,035,438 March 2000 Neal et al 6,705,197 March 2004
Neal M. 6,745,661 June 2004 Neal et al
OBJECTS AND ADVANTAGES
[0017] The method of the present invention differs from prior art
first in that a mass of tough material is used not in an attempt to
directly block the projectile, nor to deflect it, but to couple
mass to it, and thus slow it down by transfer of kinetic energy.
This process then may be repeated in sequential stages, whereby
additional mass is coupled progressively to the projectile, causing
more and more kinetic energy to be transferred from it.
[0018] Second, the method provides a method of restraining the
motion of the coupled masses and projectiles, using a network of
fibers. The fibers are constructed into a three dimensional
arrangement which allows the fibers to elongate elastically or
plastically under favorable mechanical conditions so that they
exert a progressive restraining force.
[0019] The nature of the restraining force is also of novel design
in the present invention, being of two combined sources. First, the
fibers stretch and provide restraint due to their own tensile
modulus. Second the fibers couple force to surrounding adjacent
masses, causing these masses also to experience acceleration, and
thereby coupling kinetic energy from the projectile to surrounding
masses which are themselves not necessarily directly impacted by
the projectile.
[0020] The manner in which energy is coupled to adjacent masses is
by tensile loading of the fibers substantially in the direction of
the fibers longitudinal axis and substantially in the direction of
the projectile prior to impact. These features are novel and are an
important advance in ballistic protection because the design of the
invention is such that the energy transfer and tensile loading can
be accomplished well with the material properties of currently
available materials and still be able to defeat hard, high velocity
ballistic projectiles, which are capable of lethally penetrating
many types of conventional "bullet proof vests".
[0021] The design also provides an intrinsically flexible material,
which is suitable for bullet proof vests; it does not have to be
further modified, or made up into separate small pieces joined
together in order to be flexible. The resulting accomplishment is
exemplified in the embodiments described below, namely flexible,
light bullet proof vest capable of defeating high velocity rifle
bullets at close range. The composite armor can be formed into
complex shapes and thus made into protective clothing that can
protect much of the body, not only just the vital organs.
[0022] The second embodiment described herein is particularly
straightforward to manufacture and utilizes readily available
materials, and therefore could be deployed to serving armed forces
economically and quickly. The method of the invention is also
scalable, and the size and dimensions of the internal components
can be adjusted to defeat heavy caliber projectile or artillery
shells, however, such embodiments would not reasonably qualify as
light weight for use in personal body armor such as a bullet proof
vest.
[0023] Several variations to the three primary embodiments are
described which incorporate additional novel construction
arrangements and additional methodologies for dissipating kinetic
energy from the projectile to the mass and fiber framework of the
composite armor material by incorporating elastomeric and plastic
deformation processes and dynamic rearrangement of the material 3D
structure progressively under ballistic loading to facilitate ease
of manufacturing and production of high performance armor on a
volume basis.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] The patent or application file contains reference to
following figures:
[0025] FIG. 1 shows a cross section through five layers of a
bulletproof vest.
[0026] FIG. 2 shows front view of an assembled bullet proof vest
showing the front (chest) protection, the left and the right
shoulder protection and the Velcro.TM. straps used to assemble the
vest.
[0027] FIG. 3 shows a layer of an unassembled bullet proof vest in
part; the front (chest) piece and one shoulder piece, unassembled,
and flat.
[0028] FIG. 4 shows a cross section through one ballistic defeating
layer of the vest of the first embodiment.
[0029] FIG. 5 shows the arrangement and construction of a grid of
tubes used in the construction of the first embodiment of the
invention.
[0030] FIG. 6 shows the arrangement and layout of x and y direction
fibers prior to assembly on to the tubular grid of the first
embodiment.
[0031] FIG. 7 shows a plan view (in the plane of the composite
armor material of the vest) of one mass used in the first
embodiment.
[0032] FIG. 8 shows a cross section through one mass used in the
first embodiment.
[0033] FIG. 9 shows a cross section through one mass used in the
first embodiment located on a protective spacer washer.
[0034] FIG. 10 shows a cross section through one ballistic
retarding layer of the second embodiment.
[0035] FIG. 11 shows a cross section through one ballistic
retarding layer of the third embodiment.
[0036] FIG. 12 shows a cross section through one mass of the third
embodiment and its sub assemblies.
[0037] FIG. 13 shows a cross section illustration of nominal
deformation and geometric rearrangement under ballistic loading in
the third embodiment.
DETAILED DESCRIPTION
[0038] The invention provides for a composite material that
protects against specific ballistic threats, and is flexible and
relatively light in weight. The invention can be fashioned into
protective body armor ("bullet-proof vests"), and other protective
coverings, including supplementary protection for conventional
bullet proof vests. ("Bullet-proof vest" is a commonly used term
for ballistic body armor, and in many cases it is a misnomer,
because many such vests do not in fact provide protection against
rifle fire. Nevertheless, the term is common usage and the concept
it conveys is well understood, so it is used here with that
understanding.)
[0039] Three practical embodiments of the invention will now be
described, which explain its construction, method of operation and
unique features.
The First Embodiment
[0040] The first embodiment is a flexible bullet proof vest which
provides the wearer protection from high velocity, high power rifle
fire to within the inner surface deflection limit of 4.4
centimeters (1.73 inches) specified by the United States National
Institute of Justice (NIJ Standard 0101.04). By high velocity, high
power rifle, we specifically consider the standard NATO
7.62.times.51 mm cartridge, which is a common threat in current
warfare. This first embodiment of the invention is designed to
protect to NIJ Standard 0101.04 Type III which protects against
7.62 mm Full Metal Jacketed (FMJ) bullets (U.S. Military
designation M80), with nominal masses of 9.6 grams (148 grains) at
a reference velocity of 847 meters/second (2780 ft/s). The concept
of flexibility is important in bullet proof vests. A solid or stiff
vest is extremely uncomfortable to a human user, and can result in
the vest not being worn. Non-flexible vests exist, but tend to be
constructed to provide minimal essential body coverage, and
projectiles can enter though the shoulders and other unprotected
areas and still reach vital organs. For reasonable comfort, a
bullet proof vest needs to be able to flex about +/-30 degrees per
foot of material length, plus is should allow the shoulders to rise
and drop by 7.62 centimeters (3 inches).
Construction of the First Embodiment
[0041] The bullet-proof vest of the first embodiment, hereinafter
referred to as "vest", is constructed of five layers. A cross
section through the layers is shown in FIG. 1. An incoming bullet
(17) is shown in FIG. 1 as a reference for the direction of
anticipated threat. In the following, the terms "first" and "outer"
shall refer to the side of the vest from which a bullet comes, i.e.
the first impacted, and the term "inner" shall refer to the side
closest to the wearer.
[0042] With reference to FIG. 1, the first and outermost layer (11)
is of medium weight polyester fabric, with conventional Velcro.TM.
patches (10) sewn and bonded to it to facilitate attachment of
accessories and to facilitate securing of the vest around the
wearer. Layer (11), is incidental to the ballistic function of the
vest. As an alternative to conventional polyester fabric a tough
breathable waterproof fabric, such as conventional rip-stop
Gortex.TM. could be used. Behind layer (11) are three similar
layers: the second layer (12), the third layer (13), and the fourth
layer (14), each of special composite material which have ballistic
protection function, the detailed construction of which are
described immediately below. The innermost fifth layer (15) is the
layer closest to the vest wearer and is a "comfort layer",
essentially incidental to the ballistic function of the vest.
Layers 11-15 may be in direct contact with each other at some
places and not in direct contact at other places in the vest,
according to how the garment is flexed. Minimal separation of the
layers is assured through the inclusion of thin elastomeric foam
material.
[0043] The final assembled vest is depicted in FIG. 2.
[0044] The construction of layer (12), is described in detail now.
The construction of the other two ballistic function layers, (13)
and (14), is substantially similar to the construction of this
layer (12). Layer (12) is comprised of six sub-layers, as shown in
FIG. 4. The construction is described starting with the innermost
sub-layer, i.e. that which is closest to the wearer.
[0045] The innermost sub-layer is 0.635 centimeter (0.25 inch)
thick elastomeric foam sheet (40). This innermost sub-layer is
actually added to the layer as a final step, after the assembly of
the rest of the layer, which will now be described. A thin first
substrate sub-layer (41) of high tensile ballistic fiber is
constructed with an open weave. Spectra 900 is a suitable fiber,
but others could be used, as could various weave directions or
alternatively a low density unwoven felt. The weave is made with
650 Dernier (60 filament) fibers at a weave density of 4.72 per
centimeter (12 per inch). Next a mesh sub-layer (50) is constructed
of short pieces of metal tube as shown in FIG. 5.
[0046] In FIG. 5, the pieces of metal tube (51) are threaded onto a
high tensile fiber (52) type Spectra 900.TM. 1600 Dernier and woven
to form a regular square mesh. In this example embodiment the mesh
grid spacing is 1.65 centimeters (0.65 inches) and the tubing (51)
outside diameter is 0.3 centimeters (0.12 inches). The inner
diameter of the tubing is 0.127 centimeters (0.05 inches), being
sufficient to allow the strands of high tensile fiber (52) to pass
through, but not large enough to compromise the diametric
compression strength of the tube. The integrity of the tube under
compression is important to the function of the vest, although some
deformation in operation is acceptable. Metal has been specified
for the tube, although other material which has high compressive
strength and toughness, such as composites and ceramics, could be
used. In this embodiment 310 annealed stainless steel tubing is
used. The fibers which run though the tubes are pulled to low
tension (20 to 50 N), but not slack, and tied off at the edges. The
mesh is constructed to the desired shape and size of layer (12) as
predetermined by the shape and size of the final assembled vest.
During construction, the fibers are flexibly bonded in place to the
inside of the tubes by conventional adhesive such as room
temperature vulcanizing silicone adhesive using a small amount of
adhesive inside a piece of tube approximately every 5.08
centimeters (2 inches). This bonding is incidental to the ballistic
function of the vest, and provides ease in handling the material
during assembly. The flexible bond allows the fibers to stretch
under stress. The resulting mesh is mildly flexible but retains its
essentially square matrix structure when handled.
[0047] Next, on top of the tubular mesh, i.e. towards the outside
of the vest, is placed a sub-layer of 90 degree woven ballistic
fiber cloth (60) shown in FIG. 6. Strand orientations other than 90
degrees could be used; 90 degrees is specified here for ease of
manufacture. The 90 degree weave is not a complete weave, there are
holes or void spaces as shown in FIG. 6. The runs of x-axis fibers
(62) are each 1.27 centimeters (0.5 inches) wide and then separated
by a space of 0.635 centimeters (0.25 inches). The runs of y-axis
fibers (61) are also each 1.27 centimeters (0.5 inches) wide and
then separated by a space of 0.635 centimeters (0.25 inches). The
resulting cloth (60) is a square woven cloth with holes (64) of
size 0.635.times.0.635 centimeters (0.25.times.0.25 inches) spaced
apart by 1.27 centimeters (0.5 inches) in both x and y directions.
The cloth (60) is laid over the mesh (50) and pressed into it, so
that the holes (64) line up with the intersection joints (63) of
the mesh, and then the weave of the cloth is depressed into each
void in the mesh.
[0048] On top of the cloth are placed a plurality of small metal
discs (80), arranged in a regular square matrix layout with one
disc located at each of the voids of the mesh (50). The detail of
each disc is shown in plan view in FIG. 7 and cross section in FIG.
8. The discs are square with rounded corners of size 1.27
centimeters (0.50 inches) square and 0.81 centimeters (0.32 inches)
thick. Although square discs in a regular square matrix have been
specified, other tessellating shapes and arrangements, such as
hexagonal discs in a 120 degree arrangement are viable
alternatives, with corresponding adjustment in mesh (50) layout and
cloth (60) weave, and would alter the mechanical properties of the
material if desired. The innerside of each disc (80), which is
closest to the cloth (60), is radiused with a convex radius of 3.56
centimeters (1.4 inches) and further rounded edges. The outer side
is radiused concavely, so the thickness of the disc is roughly
uniform across its area.
[0049] The discs are CNC milled from sheet metal and inspected and
deburred and finished by hand to remove any rough edges. The
rounded edges are important and prevent the disc cutting the fibers
of the cloth against the mesh. Metal has been specified for the
disc material, although other materials which have high compressive
and ballistic shear strength and toughness, such as composites and
ceramics, could be used. The selection of the material of the disc
is important to the function of the vest. This embodiment uses
conventional 7475-T6 aluminum which has a density of 2.81 g/cc
(0.102 lbs/cu.in.). If the density of the disc material is high,
and the anticipated projectile mass is low, then the spacing of the
mesh needs to be reduced, otherwise the disc becomes too thin and
will puncture or shear on impact. The thickness of the disc is
determined by the mass and energy of the projectile(s) to be
blocked and by the density of the disc and its material properties,
as specified in the operation of the vest below.
[0050] In a variation to this embodiment, shown in FIG. 9, a 0.2
centimeter (0.08 inch) thick plastic spacer (81) is between the
cloth (60) and each disc (80). The spacer (81) has the outer face
conformal to the disc and the inner face smooth and rounded except
that each corner is thickened forming a small post at each corner
which serves to help keep the fibers of the cloth (60) in place.
The spacer provides lubrication for the fibers to slide over the
disc surface and it also provides compliant compressive cushion
during ballistic loading.
[0051] On top of the discs (80) is a second thin substrate
sub-layer (90) identical to the first substrate sub-layer (41). It
is constructed of high tensile ballistic fiber and with an open
weave. Spectra 900 is a suitable fiber, but others could be used.
The weave is made with bundles of 650 Dernier fibers at 4.72 per
centimeter (12 per inch).
[0052] The six sub-layers of the ballistic layer (12) are assembled
together as follows: the innermost substrate sub-layer (41), the
metal mesh sub-layer (50), the cloth sub-layer (60), the discs (80)
and final substrate sub-layer (90) are bonded and loosely sewn
together. The bonding is done with conventional UV-6800.TM.
(Eclectic Products Inc., LA) flexible adhesive. The purpose of the
bonding and sewing is to keep the sub-layers of layer together and
preserve the general arrangement of the components but maintain
general flexibility. The adhesive allows the fibers to slide over
the disc and mesh surfaces during ballistic loading of the armor,
but will retain its bond integrity during general handling and
normal wear so as to hold the garment together for day to day usage
i.e. when not ballistically loaded. The adhesive is applied to the
outer and inner faces of the discs (80), wetting through the fibers
of the cloth (60) and the substrate layers (41) and (90). The
sewing is done using Spectra 900 1200 Dernier 10 fiber bundles and
one loop sewn through all the sub-layers at each node of the mesh
and tied off, binding the entire layer together. A practical
alternative to adhesive and sewing would be to encapsulate the
whole layer in room temperature vulcanizing silicone adhesive in a
vacuum environment to extract trapped air or encapsulating the
sub-layers in a two-component polymer foam in a mold. The result is
a flexible but tough, mechanically stable, layer with a
two-dimensional array of metal discs supported on a cradle of high
tensile fiber which is in turn supported on metal mesh.
[0053] The overall size and shape of each layer is determined
according to the need. In this case the size and approximate shape
of the outermost ballistic layer for a medium size vest as shown in
FIG. 3, which shows only the front piece (30) and the left
shoulder-neck piece (31). The back piece is similar to the front
piece, and the right shoulder-neck piece is a mirror image of the
left. The cloth (60) is constructed oversize and then trimmed after
assembly of the aforementioned sub-layers thus far to approximately
5.08 centimeters (2 inches) oversize with respect to the plan size
of the mesh (50). Any loose fibers (61) or (62) are removed from
the edge and the extended fiber ends are folded under the mesh (50)
and bonded with UV-6000.TM. on to the weave of fibers (61) and
(62). This finishes the ends of the fibers in the ballistic layer.
Finally the assembled sub-layers just described at bonded to a
sheet of 0.635 centimeter (0.25 inch) thick flexible elastomeric
foam (40), type K-Flex LS S2S.TM. (Noel Group, LLC, NC) or similar
alternative, and bonded to it using K-Flex 720 LVOC.TM. (Noel
Group, LLC, NC) adhesive. Note that this elastomeric foam is not
sewn together with the other sub-layers of the ballistic layer.
[0054] There are two more similarly constructed ballistic layers,
i.e. a total of three, in the vest. To reduce the weight, increase
flexibility and provide less abrupt edges when assembled together,
the three ballistic layers are not constructed of exactly identical
size and shape. Also, different parts of the vest are subject to
different levels of threat and some areas of the vest overlap with
other parts when the whole is assembled, and these factors are
considered in determining the final shape and extent of each
ballistic layer, so that the overall vest performance and function
are optimized.
[0055] In this embodiment, the first ballistic layer (12) is larger
in plan (size) than the next layer (14), which is larger than the
next layer (15). For ease of manufacture, the construction of the
three ballistic layers can be of identical construction. However,
for ballistic performance it is desirable to change the dimensions
of the mesh and discs for each specific layer, because the
projectile slows and adds mass as it passes though each layer. For
this embodiment, the disc size for layer (12) has been specified as
1.27 centimeters square (0.5 inches square). The disc size for
layer (13) is 1.65 centimeters square (0.65 inches square), and the
disc size for layer (14) is 2.54 centimeters square (1.0 inches
square). The mesh size of each layer is increased accordingly by
using longer sections of the tube (51), so that the mesh size is
0.381 centimeters (0.15 inches) larger than the disc size in each
layer. All of the discs in this embodiment are 0.81 centimeters
(0.32 inches) thick. The fact that the disc thicknesses for each of
the three ballistic layers has been selected to be the same is a
matter of convenience of manufacture, and will not be achievable in
many other configurations or embodiments of the invention. The disc
properties, including thickness must be calculated for each layer
and the specifically contemplated ballistic loading, according to
the mass, velocity and cross sectional area of the impacting
projectile. For layer (13), the expected impacting projectile is
not the bullet, but several possible combinations of bullet and
disc from layer (12). Similarly, for layer (14), the expected
impacting projectile is several possible combinations of bullet,
discs from layer (13) and discs from layer (12). However, there is
also possibility the bullet will impact in such a way as to miss a
disc at the second layer (12). Therefore the ballistic
characteristics of the discs in the third layer (13) cannot be too
different from that of layer (12) and must be suitable as providing
first line defense if the bullet squeezes past the discs in layer
(12).
[0056] The innermost layer of the vest, layer (15), is medium
weight cotton fabric cross hatched sewn at 5.08 centimeter (2 inch)
spacing on to 0.51 centimeter (0.2 inch) thick polyester quilting;
the cotton fabric is closest to the wearer. The purpose of layer
(15) is largely oriented towards user comfort, and it is
essentially incidental to the ballistic function of the vest,
except that it provides a small amount of additional separation of
the ballistic layers from the wearer, which is always favorable in
reducing deformation of the wearer's body upon impact by a bullet,
as the vest structure itself deforms in the course of retarding and
defeating a projectile.
[0057] The assembly of the layers to form the vest is described
below. Only the assembly of the front piece of the vest is
described, as the assembly of the back and shoulder pieces are
carried out in similar fashion. Other pieces of body or property
protective armor could also be similarly assembled using the method
described; the plan shape and layout would need to be adjusted
according to the application.
[0058] The three ballistic layers and outermost fabric layer of the
front piece of the vest are formed into shape around a mannequin
torso of appropriate size and first bonded together using three
5.08 centimeter (2 inch) wide stripes of UV-6800.TM. between each
pair of layers as follows: first the fourth layer (14) is placed on
the mannequin and a vertical stripe of adhesive run down the center
of the chest and another stripe down from the shoulder line on
either side. It is easier if the mannequin is placed on its back
for this process. Then the third layer (13) is placed on top of
layer (14) in the correct position. Next adhesives stripes are
placed on the layer (13) and the second layer (12) placed on top of
it. Next adhesives stripes are placed on layer (12) and the first
layer (11) placed on top of it. When the adhesive has dried, the
bonded-together layers can be handled for further assembly. The
three ballistic layers and outermost layer are then sewn together
at a few points using 650 Dernier Spectra 900 fiber; specifically
along the centers of the vertical adhesive stripes, sewn at 7.62
centimeter (3 inch) spacing. Sewing is effected by carefully
threading the needle though the mesh and disc layers from the
inside and the needle is passed carefully through the composite
material. At each point, eight loops of fiber are sewn and tied
off.
[0059] Next the innermost layer (15) is placed under the other
layers and the whole is loosely sewn together around the edges
approximately 1.27 centimeters (0.5 inches) from the outer edge
using 650 Dernier Spectra 900 fiber. As with the previously
mentioned sewing, the pathway for the needle has to be carefully
passed through the multiple layers from the inside. The outer seam
is then taped to 1.91 centimeters (0.75) inches, i.e. with 3.81
centimeter (1.5 inch) tape and the tape bonded in place with
UV-6800.TM. adhesive.
[0060] The design of the vest is such that the material from the
front and back pieces overlap slightly at the side seams and are
fastened by conventional Velcro.TM., which allows adjustment of
fit. The Velcro.TM. panels (10), are sewn onto layer (11) before
assembly of the vest. In addition to the conventional "A" shape
vest, FIG. 2 (20), comprised of a front piece and a back piece,
there is a separate two-part piece which protects the shoulders and
neck, and allows freedom of movement of the shoulders. This
additional shoulder piece is shown in FIG. 2 (21) and (22) and the
flat plan shape of its outermost ballistic layer is shown (left
side only) in FIG. 3 (31). It is attached to the vest "A" body (20)
by Velcro.TM. elastic straps (23) and (24) which pass over each
shoulder and the left and right pieces are flexibly joined at the
neck by Velcro.TM. (25).
Operation of the Vest
[0061] We will consider the normal impact on the vest of a high
power high velocity rifle bullet at very close range, specifically
a NATO 7.62 mm Full Metal Jacketed (FMJ) bullet with mass of 9.6
grams (148 grain) at an unretarded reference velocity of 847 m/s
(2780 ft/s).
[0062] The bullet passes unaffected through the first layer (11) in
FIG. 1, which is incidental to the ballistic function of the vest.
The bullet then contacts the first ballistic layer (12). We shall
assume for now that it impacts on a disc. This assumption will be
addressed later. In an ideal, lossless interaction, the bullet and
disc would rebound with a relative separation velocity equal in
magnitude but opposite in direction to that prior to impact, in
accordance with the laws of conservation of momentum and
conservation of energy. However, in practice, the impact is not
lossless. Energy is dissipated in several manners, including the
deformation of the bullet, deformation of the disc and deformation
of the structure supporting the disc in space. Furthermore, the
impact is not an instantaneous event, but in practice it is a
progressive event, during which both the bullet and the disc move,
substantially in the original direction of the bullet prior to
impact. During the event the disc is deforming and accelerating,
and the bullet is deforming and decelerating. The bullet/disc
interaction is complex and the outermost, first impacted, surface
of the disc first accelerates, and then decelerates. Provided that
the bullet does not puncture and entirely pass though the disc, it
is reasonable to assume that bullet and disc move forward together
for at least a short distance after the initial impact. The
criterion that the bullet does not puncture and pass through the
disc is met if the disc is designed correctly. Specifically the
disc should be light, so there are no significant inertial forces
restraining it, it should be of high shear strength and toughness
under ballistic loading, which is dependent on the material
selection and thickness to area ratio. Because of the speed of
ballistic interactions, normal mechanical properties of materials
do not apply and special ballistic material properties need to be
specifically considered in material selection and component design,
as would be known to one practiced in the art. With this in mind it
is a relatively straight forward computation for one skilled in the
art to determine what plan dimension (and therefore mass) of disc
of a given thickness and material would cause it to be punctured by
a given projectile if that plan dimension were to be exceeded. The
maximum disc size and the mass that would not be punctured for a
given impacting projectile could then be correspondingly
calculated. The ballistic design of specific projectiles also has
bearing on disc puncture and penetration and would need to be
factored into the calculation, and again this would be well
recognized and understood by one skilled in the art. Accordingly,
the optimal mass and dimensions of a disc could be calculated and
selected to defeat a selected projectile type or range of
projectile types for a given configuration of armor to be
constructed.
[0063] In addition to the deformation of the bullet and disc, the
structure supporting the disc also deforms and moves. This is
central to the operation of the vest. Specifically the fibers (61)
and (62) of the cloth (60) will be in tension as a result of the
motion of the disc (80). The fibers will be restrained by their
path around the mesh (50) and under adjacent discs, and the tension
will cause the mesh to move or deform, also in the direction of the
bullet, or the adjacent discs to move in the opposite direction to
the bullet, or both, or the mesh and adjacent discs to move in the
direction of the bullet. Which of these happens depends on the
specific nature of the bullet impact, its point of impact and
direction. However, the effect in operation of the vest is the same
in each case: namely the fibers (61) and (62) will be in tension
due to the movement of the disc (80) and will be restrained by
inertial forces of the surrounding mesh and discs. There is a
further beneficial effect of this process which is to add effective
mass to the bullet and disc pair, further decelerating the pair due
to conservation of momentum by coupling mass through the fibers in
tension to some of the adjacent discs and tubes.
[0064] In this specific embodiment, the total mass of one disc (80)
and four tubes (51) of the mesh (50) of layer (12) is designed to
be 7 grams, which is equal to 73% of the mass of an M80 bullet.
This has been calculated to provide sufficient retardation of a
range of threats, equivalent to M80 bullets or lesser projectiles,
including for example NATO 5.56 mm cartridge and various handgun
cartridges, as applied to the outer layer of a multi layer vest.
The number and nature of the fibers (61) and (62) are calculated so
as to strain elastically under the load of the moving bullet and
disc pair, but not to rupture. (Obviously damage will occur around
the impact zone and rupture will occur locally thereabouts as a
result.) Plastic deformation also may occur, as would progressive
rupture when using a combination of dissimilar fibers in the cloth
(60). If the tensile stiffness of the cloth (60) is too great, the
effect will be to directly couple a large effective mass to the
disc (80), in which case it will not accelerate freely on impact
and will be more susceptible to being punctured by the bullet.
Therefore, the number and nature of fibers (61) and (62) in the
cloth (60) is also calculated to be sufficiently compliant to allow
the bullet and disc pair to move though the mesh. The elastic, or
plastic, elongation of the fibers (61) and (62) in tension is
central to the function of the invention. Specifically, the
construction of the ballistic layers (12), (13) and (14), arranges
the fibers (61) and (62) so that they elongate in tension
substantially in the direction of original travel of the bullet.
This arrangement is advantageous over other ballistic fiber
fabrics, where the bullet impact is substantially normal to the
direction of the fibers and the fibers are first subject to lateral
compression and shear loading and the mechanical advantage of the
tensile strength of the fibers is rarely achieved. Another
advantage of the method described here is that the fibers are
buffered from contact with the actual bullet by the disc (80) and
the fibers contact the smooth surfaces of the mesh tubes (51) and
the discs (80) under load, which is further supplemented in the
variation shown in FIG. 9 by the compressing and lubricating spacer
(81).
[0065] The bullet and disc pair will continue to be decelerated by
the fibers (61) and (62) and the mass coupled by the fibers, which
will typically be part of the mesh, until they contact the next
layer of the vest, which is the second ballistic layer (13). This
occurs after the bullet and disc pair have traveled a distance of
0.635 centimeters (0.25 inches) or more if there is separation
between the layers due to folding, for example. At this point,
depending on the exact bullet type, trajectory, angle of incidence,
etc. the velocity of the bullet disc pair at the disc leading face
will be of the order of 60 percent of the initial bullet velocity.
Depending on the material of the bullet, the rear of the bullet
will still be traveling with slightly higher velocity and the
bullet will still be deforming. The deceleration from impact
velocity is due to the combined effects of adding mass and the
tensile restraint of the fibers (61) and (62) and the energy of
deformation of the various components including the bullet itself.
The bullet and disc pair now impact a disc from layer (13). The
mass of this disc is greater than that of the disc of layer (12).
The deceleration process described above in relation to the bullet
impacting layer (12) now applies to the bullet and disc impacting
the second ballistic layer (13).
[0066] The possibility that the bullet misses a disc in layer (12)
and impacts in between discs is now considered. In this case the
bullet will experience some deceleration due to contact with the
mesh and partial contact with one or more discs. The same
consideration applies in the case that a bullet impacts the corner
or edge of a disc of the first ballistic layer, in which case the
bullet will experience energy transfer, and therefore deceleration,
also due to the rotation and possible shearing of the disc and/or
lateral acceleration of one or more discs. (In both cases work will
still also be done by the deformation of the bullet and discs or
other vest components.) However, the function of the vest prevails
in both these cases, because of the multi-layer construction. If a
bullet misses a disc of layer (12) then it will likely impact a
disc of layer (13). The tubes (51) and (52) of the mesh (50) are
themselves of armor type material and will serve to partially
deform the bullet and absorb some of its kinetic energy. The discs
of the second ballistic layer could be forcibly aligned by the
construction of the vest to protect the area between the gaps in
the discs of the first ballistic layer, but preserving this
arrangement will tend to reduce the flexibility of the final
garment and would be suited to more rigid applications. The discs
of layer (13), although larger than those of layer (12), are also
designed to retard a direct impacting bullet. Therefore the
dimensions and mass of the discs of the second ballistic layer are
calculated not to be too large in area and mass. If by chance a
bullet misses the discs of the first and second ballistic layers,
then it will be retarded by the third ballistic layer. Overall, a
bullet will experience some deceleration in each ballistic layer,
even if it does not impact a disc directly and experience optimal
deceleration. The net effect of the design is that due to the
cumulative effect of the three ballistic layers the bullet will be
sufficiently decelerated so as not to puncture the third and final
ballistic layer.
[0067] An alternative embodiment of the invention could also be
considered here, where a conventional ballistic fiber construction
vest is worn under a single layer of the current invention
corresponding to layer (12). The kinetic energy and cross sectional
area of the bullet and disc pair after passing through layer (12)
are similar to that of a hand gun projectile such as a 0.45 ACP
caliber, and conventional ballistic fiber vests are generally
effective at stopping such projectiles.
Description of Second Embodiment of the Invention
[0068] A second embodiment of the invention will now be disclosed.
It is also a bullet proof vest, hereafter referred to as vest. This
second embodiment differs from the first embodiment in the
construction of the ballistic layers, which will be described in
detail. However the principles of operation and function are the
same as in the first embodiment. The general assembly and
construction of the final garment is essentially similar to that of
the first embodiment and will not be described here.
[0069] The vest is constructed of five layers. There are three
ballistic function layers, as with the first embodiment. The
outermost first layer (11) and innermost fifth layer (15) are the
same as described in the first embodiment.
[0070] Details of the construction of the first ballistic layer of
the second embodiment vest are shown in the cross section in FIG.
10. A plurality of square cross section discs (103) arranged in a
regular square matrix pattern are supported in a flexible three
dimensional framework of high tensile polymer fibers (104) and
(105). The discs (103) are 1.21 centimeters by 1.21 centimeters by
0.66 centimeters (0.475 inches by 0.475 inches by 0.26 inches)
quartz fiber composite material, with 60% fiber volume fraction,
conventional multi-directional weave fabric, embedded in a
toughened cyanate ester resin. The discs have rounded and smoothed
edges. On both faces of each disc is placed a 0.127 centimeter
(0.05 inch) thick spacer (109) of UHMW PE material, each conformal
to the face of the disc and smooth on the other side. The spacer is
held in place during assembly using a small amount of conventional
viscous adhesive such as UV-6000.TM., noting that it is difficult
to bond to UHMW PE, but that the bond is not necessary to the
ballistic function of the vest. Calculation of mass, dimensions and
selection of material properties are the same as those for the
discs (80) considered above in the first ballistic layer (12) of
the first embodiment of the invention.
[0071] Strands of ballistic fiber (104) are wound alternately over
and under adjacent discs in the x-direction and tied off at the end
of a line of discs of length corresponding to the desired
dimensions of the overall garment. The fibers (104) are spread
evenly across the surface of each disc so that the entire surface
area of the disc is covered with fiber. Then strands of ballistic
fiber (105) are wound alternately over and under adjacent discs in
the y-direction, such that the entire surface area of each disc is
also covered by fibers in the y-direction. This process binds the
lines of discs first created by weaving the x-direction fibers
(105) together, and now creating a cloth of 90 degree weave fibers
encasing a plurality of regularly spaced discs (103). The fiber
type is Spectra 900.TM. 1600 Dernier, and the density of the weave
is such that 48 fibers are spread linearly across each disc in both
x and y directions. The considerations as to fiber type are the
same as discussed above in the first embodiment. An alternative
embodiment using a large number of fibers comprised of a
combination of 20% Spectra 900.TM. and 80% commercial high density
high tenacity polyester fibers could be employed, the arrangement
providing a progressive load as the less elastic fibers will fail
in tension first. As with the first embodiment, arrangements other
than regular square matrix and weaves other than 90 degree could be
alternately employed, providing adjustment in the composite
material properties.
[0072] Two thin substrate sub-layers (106) and (107) of high
tensile ballistic fiber are constructed with an open weave and are
placed either side of the disc-weighted fiber cloth just
constructed. Spectra 900 is a suitable fiber, but others could be
used. The weave is made with bundles of 650 Dernier fibers at 4.72
per centimeter (12 per inch). The substrate layers, fiber cloth and
discs are bonded to each other by placing a small amount of diluted
flexible adhesive such as type UV-6800.TM. at each disc, first on
one side and then the other. It is noted that for the function of
the vest, the restraining shear loading imparted by the adhesive
should be less than the tensile stress in the fibers, and this is
easily achieved with practical materials. Finally, a sub-layer of
0.635 centimeter (0.25 inch) thick elastomeric foam (108), type
K-Flex LS S2S.TM. (Noel Group, LLC, NC) or similar, is bonded to
the innermost side of the composite substrate (106), fiber, disc
and substrate (107) just assembled. The mechanical properties of
the elastomeric foam are not important to the ballistic retardation
function of the vest in this embodiment, though selection of the
material could further enhance performance. What is most pertinent
in the present embodiment is that the sub-layer of elastomeric foam
(108) ensures a minimum separation between adjacent ballistic
layers, allowing the fibers (105) and (106) to stretch under
ballistic load and the bullet's energy to be coupled to surrounding
discs by the network of fibers. In an alternative embodiment to the
present, the elastomeric sub-layer could supplement or replace the
retarding and energy coupling function of the fibers (105) and
(106) if constructed out of material with appropriate mechanical
properties such as fiber reinforced rubber.
[0073] A second ballistic layer is constructed essentially
identically to the first ballistic layer just described, except
that the disc size is 1.78 centimeters by 1.78 centimeters by 0.81
centimeters (0.7 inches by 0.7 inches by 0.32 inches), and the
overall plan shape and size of the layer is smaller than the first
ballistic layer.
[0074] A third and final ballistic layer is constructed essentially
identically to the first and second ballistic layers just
described, except that the disc size is 2.67 centimeters by 2.67
centimeters by 0.56 centimeters (1.05 inches by 1.05 inches by 0.22
inches), and the overall plan shape and size of the layer is
smaller than the second ballistic layer.
[0075] The three ballistic layers are placed between a first,
outermost layer and fifth innermost layer as in the first
embodiment and assembled into a completed garment in similar
fashion to the first embodiment.
[0076] Although the construction of the second embodiment differs
from the first, the function is very similar. A 7.62 NATO FMJ
bullet impacting the first ballistic layer causes a disc (103) to
accelerate and also causes the ballistic fibers (105) and (106) to
elongate in tension. The addition of mass to the bullet and the
extension of the fibers and the coupling of additional mass though
the fibers all cause the bullet to be decelerated, as well as the
deformation of the bullet and disc. These effects are repeated as
the combined bullet and disc impact the second and eventually third
ballistic layers.
[0077] One final variation to the above embodiment is described. In
this variation the discs are constructed not as discs per se but as
a series of stacked plates. The dimensions of the plates in the
first layer are 1.27 centimeters by 0.254 centimeters (0.5 inches
by 0.1 inches) in area, and 0.762 centimeters (0.3 inches) in
thickness, and of material 7475-T61 aluminum alloy. The plates have
rounded-off corners. The orientation of thickness in this case
being the same as that used in the above descriptions, i.e. the
plates are aligned edge-on to the ballistic threat direction.
Fibers are woven alternately over and under the individual plates
in the x-direction, as with the discs previously. The plates are
canted 45 degrees to the direction of the fiber weave. In the next
line the plates are canted 45 degrees in the opposite direction,
making a sort of herringbone pattern of plates. Then the
y-direction fibers are woven alternately over and under each line
of plates just constructed with the x-direction fibers. The
herringbone arrangement makes the composite armor material less
flexible (it is still flexible) in the x-direction than if they are
arranged orthogonally, but it improves ballistic performance. There
are many alternate weaving patterns which will be obvious to one
practiced in the art that could be employed that will effectively
encompass the plates within the weave and provide for tensile
elongation of the fibers in the direction essentially normal to the
plane of the layer under ballistic loading. Although regularly
rectangular plates have been described in this instance, other
three dimensional shapes and aspect ratios are specifically
contemplated, including but not limited to three dimensional shapes
which partially enclose some or all of the fibers in the locality
of specific disc, and shapes and forms comprised of or assembled
from more than one part.
Description of Third Embodiment of the Invention
[0078] A third embodiment of the invention will now be disclosed.
It is also a bullet proof vest, hereafter referred to as vest. This
third embodiment differs in construction of the ballistic layers,
one of which will be described in detail, however the principles of
operation and function are the same as in the first and second
embodiment. The general assembly and construction of the final
garment is essentially similar to that of the first and second
embodiment and will not be described.
[0079] The vest is constructed of five layers. There are three
ballistic function layers, as with the first embodiment. The
outermost first layer (11) and innermost fifth layer (15) are the
same as described in the first embodiment.
[0080] Details of the construction of the first ballistic layer of
the third embodiment vest will now be described with reference to
FIGS. 11, 12 and 13.
[0081] A plurality of square cross section multi-component discs
(303) arranged in a regular square matrix pattern is supported in a
flexible framework of high tensile polymer fibers (304) and (305).
Each disc has a main and outer component which itself has two parts
(made of one piece of material): a 1.2 centimeters square (0.475
inches square) cross section in the plane of the material and of
thickness 0.635 centimeters (0.25 inches) and a central round stem
part of diameter 0.762 centimeters (0.3 inches) and 0.457
centimeters thick (0.18 inches). As shown in FIG. 12, each disc
(303) is comprised of an outer component (317) just described of
7075-T6 aluminum, an inner component (318) of conventional cyanate
ester resin impregnated quartz composite which is 1.2 centimeters
square (0.475 inches square) cross section and 0.254 centimeters
(0.1 inches) thick and a 316 stainless steel screw (319) which is
threaded into the outer component (317). Fibers (304) and (305) are
woven substantially in the x and y directions between the discs to
form the composite armor material. The fibers (304) and (305) are
also woven and or wound around adjacent discs regularly and
randomly to bind and secure the whole construction together.
Additionally, some fibers are threaded and looped around the x and
y fiber bundles between the discs to add robustness to the
construction. The layer is constructed by weaving the fibers as
just described across, between and around the disc outer components
(317) which are laid out in an x-y matrix for assembly, then the
inner components (318) are screwed in place with screws (319) and a
securing layer of conventional flexible adhesive such as
UV-6000.TM. is applied. The remainder of the construction of the
ballistic layers of the third embodiment and of the five layers of
the vest of the third embodiment are the same as for the second
embodiment and will not be described here.
[0082] Under ballistic impact of a projectile on one disc, the disc
will move substantially in the direction of impact and
substantially normally to the plane of the material, and the
general arrangement of the composite material will be deformed and
rearranged temporarily. Under this rearranged geometry, as depicted
in FIG. 13, the further motion of the impacted disc will be
restrained by the tensile elongation of fibers taking place
substantially in the direction of motion of disc and the ballistic
impact. FIG. 13 illustrates a condition of a ballistic projectile
having impacted a first disc (313) of the layer and caused the
layer to deform and dynamically rearrange geometrically such that
tensile elongation of fibers occurs between disc (313) and adjacent
disc(s) (314). The projectile and disc will both deform severely on
impact, which is not shown in FIG. 13 for purposes of clarity.
Intrinsic and implicit in the design of the third embodiment and
variants thereof is the concept that under ballistic load the
geometry of the fibers and discs will rearrange prior to ultimate
tensile stress from the natural or rest or pre-ballistically loaded
configuration. Further, the arrangement of discs and fibers allows
for limited localized slideable movement of the fibers over the
discs; as deformation of the initial arrangement occurs under
loading, the tension in the fibers increases, and eventually at an
amount predetermined by the specific arrangement, friction causes
the fibers to bind against the discs, thus causing any further
deformation to be done as work against tensile extension of fibers.
In this example embodiment as described the discs (303) have been
made of three parts and are screwed together, but other
configurations can be readily contemplated by one skilled in the
art. The construction is such that the fibers and discs are engaged
in a 3D matrix such that under ballistic loading the structure is
altered by first slidable motion of discs relative to fibers and
that any disc first impacted by a ballistic projectile imparts or
couples energy to adjacent discs by tensile extension of fibers
wholly or in part substantially in the direction of the ballistic
impact.
[0083] The ballistic sub layer of the third embodiment just
described is sandwiched between and bonded to supporting sub layers
(306), (307), (308) in FIG. 11 corresponding to sub layers (106),
(107), (108) respectively in FIG. 10 previously described for
second embodiment. The construction is similar to those previously
described for the first and second embodiments and will not be
repeated here.
[0084] The above method and all its embodiments and variations may
be used to protect persons and property against kinetic missiles
such as firearm bullets. The invention is scalable, such that basic
design is applicable to protection from heavier caliber weapons,
such as .50 caliber armor-piercing bullets or larger shells,
including cannon and artillery shells, by adjusting the size of the
components and the material calculations according to the method
described and the number of layers appropriate to the protection
required.
[0085] The present invention is therefore well-adapted to carry out
the objects and attain the ends mentioned, as well as those that
are inherent therein. While the invention has been depicted,
described and is defined by references to examples of the
invention, such a reference does not imply a limitation on the
invention, and no such limitation is to be inferred. The invention
is capable of considerable modification, alteration and equivalents
in form and function, as will occur to those ordinarily skilled in
the art having the benefit of this disclosure. The depicted and
described examples are not exhaustive of the invention.
Consequently, the invention is intended to be limited only by the
spirit and scope of the appended claims, giving full cognizance to
equivalents in all respects.
* * * * *
References