U.S. patent application number 10/186822 was filed with the patent office on 2004-06-24 for lightweight ceramic armor with improved blunt trauma protection.
Invention is credited to Alfeld, Robert D. JR., Miller, Jon, Puckett, David L..
Application Number | 20040118271 10/186822 |
Document ID | / |
Family ID | 32592578 |
Filed Date | 2004-06-24 |
United States Patent
Application |
20040118271 |
Kind Code |
A1 |
Puckett, David L. ; et
al. |
June 24, 2004 |
Lightweight ceramic armor with improved blunt trauma protection
Abstract
The invention relates to armor that is intended to withstand and
provide protection against blunt trauma or ballistic impact from a
projectile or the impact of a stabbing weapon. Such impacts on the
armor may transmit a high localized load to the body of the wearer.
The invention reduces the intensity of this loading thereby
reducing tissue trauma. The invention uses one or more layers of an
energy absorbing material that contains a large volume fraction of
fluid filled free space, distributed throughout an internal
cellular structure that accommodates deformation on one surface
without passing on the same degree of deformation to its adjacent
surface. It is, in effect, a highly compressible layer that
disperses a dynamic load applied normal to its surface (resulting
for example from the bullet impact) into a more laterally extensive
pressure distribution. When this material is combined with
reinforcing fiber material layers, the deformation reduction is
further enhanced.
Inventors: |
Puckett, David L.; (Foothill
Ranch, CA) ; Alfeld, Robert D. JR.; (Huntington
Beach, CA) ; Miller, Jon; (Hesperia, CA) |
Correspondence
Address: |
LEONARD TACHNER
A PROFESSIONLA LAW CORPORATION
SUITE 38-E
17961 SKY PARK CIRCLE
IRVINE
CA
92614-6364
US
|
Family ID: |
32592578 |
Appl. No.: |
10/186822 |
Filed: |
July 1, 2002 |
Current U.S.
Class: |
89/36.02 |
Current CPC
Class: |
F41H 5/0428
20130101 |
Class at
Publication: |
089/036.02 |
International
Class: |
F41H 005/02 |
Claims
We claim:
1. Body armor comprising: a penetration-resistant material layer
positioned for receiving an incident projectile; a composite
backing layer positioned contiguous to said penetration-resistant
layer for receiving said projectile after it has penetrated said
penetration-resistant layer; and at least one layer of multiple
closed cell flexible material positioned contiguous to said
composite backing layer opposite of said penetration-resistant
material.
2. The body armor recited in claim 1 further comprising a spall
shield enclosing said penetration-resistant layer, said composite
backing layer and said multiple closed cell material layer.
3. The body armor recited in claim 1 wherein said at least one
multiple closed cell flexible material layer comprises at least one
layer of reinforced fiber material.
4. The body armor recited in claim 1 wherein said
penetration-resistant material comprises a ceramic.
5. The body armor recited in claim 1 wherein said composite backing
comprises a carbon and resin impregnated fiber.
6. The body armor recited in claim 1 wherein said at least one
multiple closed cell flexible material comprises a TPU cellular
honeycomb structure.
7. The body armor recited in claim 1 wherein said at least one
multiple closed cell flexible material comprises a plurality of
contiguous sealed cells, each such cell having a fluid therein.
8. The body armor recited in claim 7 wherein said fluid is a
gas.
9. The body armor recited in claim 8 wherein said fluid is air.
10. The body armor recited in claim 3 wherein said at least one
layer of reinforced fiber material comprises Kevlar.RTM..
11. An upgrade apparatus for improving projectile penetration
resistance of soft body armor; the upgrade apparatus comprising: a
ceramic plate; a composite backing layer in contiguous relation to
said ceramic plate; a flexible layer of cellular material having a
plurality of contiguous closed cells positioned between opposed
cover layers, said cellular material layer being positioned closest
to said soft body armor.
12. The upgrade apparatus recited in claim 11 further comprising a
spall shield enclosing said ceramic plate, said composite backing
layer and said layer of cellular material.
13. The body armor recited in claim 11 wherein said closed cell
flexible material layer comprises at least one layer of reinforced
fiber material.
14. The body armor recited in claim 11 wherein said composite
material comprises a resin impregnated fiber.
15. The body armor recited in claim 11 wherein said closed cell
material comprises a TPU cellular honeycomb structure.
16. The body armor recited in claim 11 wherein said closed cell
material comprises a plurality of contiguous sealed cells, each
such cell having a fluid therein.
17. The body armor recited in claim 16 wherein said fluid is a
gas.
18. The body armor recited in claim 17 wherein said fluid is
air.
19. The body armor recited in claim 13 wherein said at least one
layer of reinforced fiber material comprises Kevlar.RTM..
20. An armor apparatus comprising: a rigid strike face and a
composite backing affixed to said strike face; and a layer of
flexible cellular material positioned contiguous to said
backing.
21. The armor apparatus recited in claim 20 wherein said strike
face comprises a material taken from the group consisting of
ceramic material, metallic material, plastic material and composite
material.
22. The armor apparatus recited in claim 20 wherein said composite
backing comprises a fiber and resin-based material.
23. The armor apparatus recited in claim 20 wherein said layer of
cellular material comprises thermoplastic polyurethane.
24. The armor apparatus recited in claim 20 wherein said layer of
flexible cellular material comprises at least one reinforcing layer
bonded to a surface of said layer of flexible cellular
material.
25. The armor apparatus recited in claim 24 wherein said at least
one reinforcing layer comprises a fabric.
26. A method of reducing blunt trauma to a wearer of a protective
plate resulting from sudden impact of an external force applied to
the plate; the method comprising the steps of: providing a layer of
flexible cellular material having a plurality of contiguous hollow
cells; and placing said layer between said plate and said
wearer.
27. The method recited in claim 26 further comprising the step of:
affixing said layer to said plate.
28. The method recited in claim 26 further comprising the step of:
forming said plate out of a ceramic.
29. The method recited in claim 26 further comprising the step of:
forming said cellular material out of a thermoplastic
polyurethane.
30. The method recited in claim 26 further comprising the step of:
reinforcing said cellular material by covering at least one surface
of said material with a layer of reinforcing fiber.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the invention
[0002] The present invention relates generally to the field of
armor for personal protection of the body. The invention relates
more specifically to armor that is intended to withstand and
provide protection against blunt trauma or ballistic impact from a
projectile or the impact of a stabbing weapon. Such impacts on the
armor may transmit a high localized load to the body of the wearer.
The invention reduces the intensity of this loading thereby
reducing tissue trauma. The invention is intended for use with
helmets or protective vests typical of those worn by police and
soldiers and with hard armor "upgrade plates" that are used in
conjunction with flexible armor vests to increase protection to
rifle bullet level.
[0003] 2. Background Art
[0004] Traditional soft armor used in protective vests is comprised
of layers of flexible fabric or non-woven textile. The fibers used
in these textiles are typically aramid (such as Kevlar.RTM. or
Twaron.RTM.) or polyethylene (such as Spectra Shield.RTM. or
Dyneema.RTM.). Other advanced fibers are also used. When a bullet
strikes these layered protective armors, the impact load causes a
bulge to develop which deforms the back surface of the armor. Since
the armor is worn adjacent to the body, this bulge or "deformation"
can extend into the body of the wearer. If the deformation is
large, tissue damage or "trauma" may occur. The National Institute
of Justice (NIJ) has established test methods and standards for
this deformation. A clay material, contained in an open faced box,
is utilized as a back support for the armor system. After the
bullet impact, a depression is preserved in the face of this clay.
The depth of this depression is measured and is referred to as the
"back face signature" (BFS). The NIJ requires that this deformation
not exceed 44 mm in depth. Certain other specifications, including
those used by the military, may be slightly different, but with the
general goal of achieving deformations below the NIJ maximum value.
It is widely held that trauma resulting from back face signature
(BFS) can be severe and debilitating. While this may be of reduced
consequence for a law enforcement officer that will receive prompt
medical attention in the event of a shooting, it is of serious
concern for soldiers that may not receive prompt medical treatment
as a result of battlefield conditions. The invention employs a
flexible layer which can be utilized as a "behind armor" addition
that substantially reduces deformation while adding very little
weight or other negative side-effects.
[0005] U.S. Pat. Nos. 5,918,309 and 6,253,655 each describe armor
systems that are relevant to the present invention. However,
neither such patent discloses the use of peak load reduction
material as a trauma reduction layer in a "behind armor"
configuration. U.S. Pat. No. 5,534,343 discloses the use of an
inner layer of flexible cellular material. However, the patent
relates to flexible armor. The most relevant prior art appears to
be U.S. Pat. No. 5,349,893 which discloses a ceramic armor having
an inner layer of cellular material. However, that material is
disclosed as being rigid, semi-flexible or semi-rigid, as opposed
to "flexible".
SUMMARY OF THE INVENTION
[0006] In the past, semi-rigid plates of plastic or metal have been
used as an insert behind the armor to help spread the deformation
across a larger body surface, thereby reducing trauma. These
methods add significant weight and also reduce the efficiency of
the armor with respect to dispersal of the bullet energy by
restricting the movement of the armor back surface during the
impact event. The invention is very light in weight and does not
reduce the performance of the basic armor material. This is
achieved by the use of one or more layers of an energy absorbing
material that contains a large volume fraction of fluid filled free
space, distributed throughout an internal cellular structure that
accommodates deformation on one surface without passing on the same
degree of deformation to its adjacent surface. It is, in effect, a
highly compressible and flexible layer that disperses a dynamic
load applied normal to its surface (resulting from the bullet
impact) into a more laterally extensive pressure distribution. When
this material is combined with reinforcing fiber material layers,
the deformation reduction is further enhanced.
[0007] The flexible cellular layer is used to best advantage when
placed at the rear surface of a ceramic/composite armor upgrade
plate of the type commonly used to enhance the protection of a
flexible ballistic vest armor. When incorporated into the design of
the upgrade plate, the deformation passed on to the soft vest armor
and in turn to the body of the wearer, is significantly reduced.
When applied to the USMC "Interceptor" body armor system SAPI
(Small Arms Protective Insert) plate, the invention reduces
deformation from an average of 41 mm to only 35 mm. This reduction
is considered highly beneficial to the armor wearer.
[0008] The preferred embodiment of the invention comprises a
flexible, resilient, cellular "honeycomb" structure where the cell
walls and principal skin surfaces are made of a thermoplastic
polyurethane (TPU) material. The open spaces of the honeycomb may
be filled with a fluid, although "air" is most commonly used. The
thickness of the TPU layer is typically between {fraction (3/16)}
and {fraction (5/16)} inches in a body armor. The thickness
utilized in a vehicle armor, primarily to enhance multihit
ballistic performance, may be significantly greater depending on
the projectile size and the associated magnitude of impact energy.
The dimension of the internal honeycomb structure and the thickness
of material comprising the face skins and cell walls may be varied
over a wide range depending on the severity of the deformation to
be mitigated. The preferred embodiment also employs one or more
layers of a strong fiber reinforcement fabric or non-woven textile
that is bonded to the face skins of the honeycomb sheet. This
reinforcement adds strength and enhances load spreading without
defeating the essential dynamic response of the trauma reduction
mechanism.
OBJECTS OF THE INVENTION
[0009] It is a primary object of the invention to reduce the trauma
experienced by the wearer of ballistic armor vests and
ceramic/composite upgrade plates when struck by a projectile that
is subsequently defeated and captured within the armor. This
objective is accomplished by reduction of the magnitude of
deformation transmitted to rear most surface of the armor system
(the surface closest to the body of the wearer) using a highly
compressible and highly flexible layer of cellular material.
[0010] It is a further object of the invention to enhance the
multiple hit capability of a ceramic/composite armor upgrade plate
by mitigating the armor damage caused by a bullet impact. This is
accomplished by the load spreading nature of the trauma reduction
layer which dynamically disperses load and creates a "counter-load"
during the impact event. This counter-load reduces the deflection
of the rigid armor plate during the impact event which, in turn,
reduces the degree of flexure-induced cracking experienced by the
plate. The protective value of ceramic/composite armor to multiple
hits is directly related to the degree of cracking experienced by
the plate.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The aforementioned objects and advantages of the present
invention, as well as additional objects and advantages thereof,
will be more fully understood hereinafter as a result of a detailed
description of a preferred embodiment when taken in conjunction
with the following drawings in which:
[0012] FIG. 1 is a schematic of a typical prior art body armor
construction showing hard armor plate on a soft ballistic fabric
without the addition of the present invention;
[0013] FIG. 2 is a schematic of a hard armor plate, and ballistic
composite backing with the invention added to decrease back face
deformation;
[0014] FIG. 3 is a schematic of body armor construction showing a
hard armor plate on a soft ballistic fabric with a trauma reduction
layer added to decrease back face deformation;
[0015] FIG. 4 is a detailed schematic of the preferred embodiment
of the cellular material layer employed in the invention;
[0016] FIG. 5A is a schematic showing a frontal view of a typical
test set-up to measure deformation;
[0017] FIG. 5B is a schematic showing a side view of a typical test
set-up prior to projectile impact;
[0018] FIG. 5C is a schematic showing a side view of a typical test
after projectile impact and defining "deformation",
[0019] FIG. 6 is a schematic of typical test results after impact
and the deformation value registered in the clay (D.sub.1) for a
standard armor system without the invention;
[0020] FIG. 7 is a schematic of typical test results after impact
and the deformation value registered in the clay (D.sub.2) for a
standard armor system with the invention;
[0021] FIG. 8 is a schematic of load dispersion prior, during and
after compression of the invention, demonstrating how load is
transmitted from a local impact area to adjacent areas and how the
trauma reduction layer actually creates a reactive load adding to
the overall regional support;
[0022] FIG. 9a is a schematic showing hard armor plate with out the
trauma reduction layer prior to impact;
[0023] FIG. 9b is a schematic showing how conventional support can
allow the ceramic to flex;
[0024] FIG. 9c is a schematic showing large crack propagation when
the ceramic has flexed from the lack of support;
[0025] FIG. 10a is a schematic showing hard armor plate with the
trauma reduction layer prior to impact;
[0026] FIG. 10b is a schematic showing how the added support of the
trauma reduction layer can reduce ceramic flex;
[0027] FIG. 10c is a schematic showing reduced crack propagation
when the ceramic has flexed less because of the trauma reduction
layer;
[0028] FIG. 10d is a schematic showing the trauma reduction layer
of the invention prior to point loading;
[0029] FIG. 10e is a schematic showing the trauma reduction layer
of the invention after point loading and resultant reactive support
force;
[0030] FIG. 11 is a graph showing the peak deformation with and
without the trauma reduction layer. The graph also shows how the
invention laterally distributes the load more uniformly over a
larger area; and
[0031] FIG. 12 is a graph comparing the average deformation values
of a standard armor system of the same design the only difference
being:
[0032] A--without the trauma reduction layer,
[0033] B--with the trauma reduction layer,
[0034] C--with the invention modified with reinforced Kevlar.RTM.
skins.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0035] Referring first to FIG. 1, it will be seen that in typical
high grade body armor construction, a soft ballistic fabric vest 2
is upgraded with a ceramic/composite body armor upgrade plate 1
comprising a layer 11 of a ceramic material and a layer 12 of
ballistic backing material, the latter typically made of a bonded
or unbonded, woven or non-woven textile comprising strong fibers
such aramid, polyethylene, nylon, glass, PBO or other strong
fibers. Layers 11 and 12 may be enclosed by a spall suppression
cover material 13.
[0036] In FIG. 2, the body armor upgrade plate 3 has been modified
as compared to the plate 1 of FIG. 1. More specifically, a trauma
reduction layer 7 has been added to a ceramic layer 5 and ballistic
composite backing layer 6 within the surrounding spall cover 4.
This improved ceramic/composite upgrade plate 3 is shown in FIG. 3
adjacent a soft ballistic vest 2 of the same type shown in FIG. 1.
FIG. 4 illustrates the preferred characteristics of the trauma
reduction layer 7. It will be seen that trauma reduction layer 7
comprises a cellular or honeycomb material 14 having face skins 13
and preferably covered on both of its external surfaces by
reinforcement layers 16 which are preferably bonded to the cellular
or honeycomb material. The cellular honeycomb material may for
example be a thermoplastic urethane ether material (TPU) supplied
by Supracor of San Jose, Calif. under the trademark STIMULITE.TM..
In the preferred embodiment, the TPU material has a thickness of
0.1875 inches, a cell diameter of 0.25 inches, a cell wall
thickness of 0.006 inches and a cell face or cover surface
thickness of 0.005 inches. The presently preferred TPU material
comprises honeycomb cells containing air. However, honeycomb cells
having other gases and even certain liquids such as water, may be
useful to spread the impact load and reduce blunt trauma-causing
deformation. Moreover, other TPU material thicknesses, cell
dimensions, and cell wall thicknesses may be advantageous depending
upon the armor and deformation requirements. Additionally, other
forms of cellular material besides honeycomb cellular, may be
suitable as a trauma reduction layer as long as each cell is
hermetically isolated from cells adjacent to it so that as some
cells are compressed others are forced to expand from the resulting
transfer of pressure. The optional reinforcement layers 16 are
preferably made of a ballistic fabric such as Kevlar.RTM. in
relatively thin layers, i.e., less than about 0.01 inches.
[0037] Referring to FIG. 5 it will be seen that in order to test
the resulting armor in accordance with methods required by the
National Institute of Justice (i.e., NIJ Standard 0101.04) the
ceramic/composite body armor upgrade plate 3 and soft armor panel 2
are affixed to a clay structure 8 within a box 9 and a bullet 10 is
fired at the armor. The extent of deformation of the clay 8 is then
measured as an indication of blunt trauma. FIG. 6 illustrates this
test for high grade body armor comprising a ceramic layer 5,
composite backing 6 and soft armor fabric 2 while FIG. 7
illustrates the same test for armor with the additional trauma
reduction layer 7. The respective measured deformations D.sub.1 and
D.sub.2 of clay 8 may then be compared such as shown graphically in
FIG. 11. As shown in FIG. 11, D.sub.1 is significantly greater than
D.sub.2. Moreover, FIG. 11 shows that use of a trauma reduction
layer in accordance with the present invention spreads the impact
load over a larger expanse (X.sub.2 versus X.sub.1) but decreases
the peak value of deformation, the latter being the key to reducing
blunt trauma to the armor-wearing personnel. The reason for this
impact load spread and reduction of peak deformation is believed to
be due to the interaction of cells in the TPU layer of the trauma
reduction layer. This interaction is illustrated in FIGS. 8a, 8b
and 8c. FIG. 8a shows the composite backing and TPU layer interface
before projectile impact; FIG. 8b shows the interface during
initial impact; and FIG. 8c shows the interface after initial
impact. It can be seen that during initial impact, the composite
backing begins to compress the TPU material causing cell walls to
compress and creating a lateral force vector transmitted to
adjacent cells. Moreover, as the backing continues to deform from
the force of the projectile, the collapse of impacted cells
continues creating both lateral and oppositely-directed vectors in
adjacent cells due both to mechanical deformation and to reduction
of cell volume at the point of impact.
[0038] The trauma reduction layer of the present invention has
still another benefit, namely reducing crack propagation in the
ceramic layer and thereby increasing impact resistance to second
shots. This benefit is illustrated in FIGS. 9 and 10. FIG. 9a shows
the conventional upgrade armor plate prior to projectile impact.
FIG. 9b shows the same plate during impact and demonstrates
substantial ceramic layer flexure due to a lack of underlying
support. FIG. 9c illustrates substantial crack propagation in the
ceramic layer due to the large extent of flexure. FIG. 10a shows
the improved upgrade armor plate prior to projectile impact. FIG.
10b shows the improved plate during impact and demonstrates reduced
ceramic layer flexure because of added support from the underlying
layers. FIG. 10c shows significantly reduced crack propagation in
the ceramic layer. The added support results from a reactive
support force generated by cellular layer. FIG. 10d shows that
layer before impact. FIG. 10e illustrates how the reactive force
results from compression at the impact point and the inflation of
adjacent cells caused by that compression. Thus, the present
invention provides two significant benefits. It reduces blunt
trauma and it improves performance against a second impact.
[0039] Finally, FIG. 12 shows actual data of tests conducted using
the test setup of FIG. 5a wherein three shorts were fired into
three personal armor configurations. Each "A" bar shows deformation
of a conventional upgrade plate. Each "B" bar shows deformation of
an improved plate with commercial TPU as a trauma reduction layer.
Each "C" bar shows deformation of an improved plate with commercial
TPU modified with Kevlar.RTM. face covers on the front and back
surfaces of the cellular layer.
[0040] The graph of FIG. 12 clearly demonstrates the significant
reduction in deformation with the addition of a TPU-based trauma
reduction layer. It also shows the even greater reduction in
deformation with the addition of a Kevlar.RTM. reinforced TPU-based
trauma reduction layer.
[0041] Having thus disclosed preferred embodiments of the
invention, it will be understood that those having the benefit of
the teaching herein will now perceive various modifications and
additions to the basic features revealed. Therefore, such
modifications and additions are deemed to be within the scope
hereof which is to be limited only by the appended claims and their
equivalents.
* * * * *