U.S. patent number RE46,898 [Application Number 15/585,598] was granted by the patent office on 2018-06-19 for polymer coatings for enhanced and field-repairable transparent armor.
This patent grant is currently assigned to The United States of America, as represented by the Secretary of the Navy. The grantee listed for this patent is The United States of America, as represented by the Secretary of the Navy, The United States of America, as represented by the Secretary of the Navy. Invention is credited to Raymond M. Gamache, Charles M. Roland.
United States Patent |
RE46,898 |
Roland , et al. |
June 19, 2018 |
Polymer coatings for enhanced and field-repairable transparent
armor
Abstract
A coating of atactic polypropylene over a transparent armor
substrate improves resistance to penetration while allowing
convenient repair of minor abrasions and scratches.
Inventors: |
Roland; Charles M. (Waldorf,
MD), Gamache; Raymond M. (Indian Head, MD) |
Applicant: |
Name |
City |
State |
Country |
Type |
The United States of America, as represented by the Secretary of
the Navy |
Washington |
DC |
US |
|
|
Assignee: |
The United States of America, as
represented by the Secretary of the Navy (Washington,
DC)
|
Family
ID: |
55016772 |
Appl.
No.: |
15/585,598 |
Filed: |
May 3, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
14320846 |
Jul 1, 2014 |
9285191 |
Mar 15, 2016 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F41H
5/0407 (20130101); F41H 5/0407 (20130101); F41H
7/04 (20130101); F41H 7/04 (20130101) |
Current International
Class: |
F41H
5/04 (20060101); F41H 7/04 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Roland et al., "Elastomer-steel laminate armor" Composite
Structures 92 (2010) 1059-1064. cited by examiner .
International Search Report and Written Opinion in
PCT/US2015/025498. cited by applicant .
Roland et al,. "Elastomer-steel laminate armor" Composite
Structures 92 (2010) 1059-1064. cited by applicant.
|
Primary Examiner: Clarke; Sara
Attorney, Agent or Firm: US Naval Research Laboratory
Roberts; Roy
Claims
What is claimed is:
1. A transparent armor system comprising: a hard, transparent armor
substrate, and a transparent coating consisting of atactic
polypropylene having a thickness of from about 0.25 cm to about 2.0
cm bonded to the armor substrate as an outside surface.
2. The transparent armor system of claim 1, wherein said armor
substrate is selected from the group consisting of (1) laminates of
soda-lime or borosilicate glass with polycarbonate and (2)
transparent ceramic armor.
3. The transparent armor system of claim 1, wherein said armor
substrate is aluminum oxynitride or spinel.
4. The transparent armor system of claim 1, wherein said armor
substrate has a hardness of at least 150 Brinell as measured with a
tungsten ball of 10 mm diameter and 3,000 kg force.
5. The transparent armor system of claim 1, further comprising a
secondary coating with a hardness greater than that of the armor
substrate, disposed between the armor substrate and the transparent
coating of atactic polypropylene.
6. The transparent armor system of claim 1, wherein said
transparent coating is bonded to said armor substrate mechanically
and/or with an adhesive.
7. A vehicle comprising a transparent armor comprising: a hard,
transparent armor substrate, and a transparent coating consisting
of atactic polypropylene bonded to the armor substrate having a
thickness from about 0.25 cm to about 2.0 cm, configured to face an
exterior surface of said vehicle as an outside surface, wherein
said transparent armor system is configured as a window,
windscreen, or viewing port of said vehicle.
8. A method of treating a transparent armor system, the method
comprising: (a) providing an armor system comprising: a hard,
transparent armor substrate, and a transparent coating consisting
of atactic polypropylene having a thickness from about 0.25 cm to
about 2.0 cm bonded to the armor substrate as an outside surface;
and (b) heating and smoothing the transparent coating, thereby
improving optical clarity thereof.
9. The method of claim 8, wherein said heating and smoothing
comprises contacting with said transparent coating with a smooth
surface.
Description
BACKGROUND
Drawbacks to conventional transparent armor include the need to use
thicker panels to achieve desired levels of protection, thus
incurring a weight penalty, and environmental erosion and
scratching of the surface, which reduces transparency. A need
exists to mitigate these problems.
BRIEF SUMMARY
In a first embodiment, an armor system includes a hard, transparent
armor substrate, and a transparent coating of atactic polypropylene
bonded to the armor substrate.
In another embodiment, a vehicle incorporates the armor system of
the first embodiment, with the transparent coating configured to
face an exterior surface of the vehicle, the armor system
configured as a window, windscreen, or viewing port of said
vehicle.
A further embodiment involves treating the armor system of the
first embodiment by heating and smoothing the transparent coating,
thereby improving optical clarity thereof.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 shows the increase in velocity required to penetrate armor
(V-50) due to the presence of a 19 mm polyurea coating.
DETAILED DESCRIPTION
Definitions
Before describing the present invention in detail, it is to be
understood that the terminology used in the specification is for
the purpose of describing particular embodiments, and is not
necessarily intended to be limiting. Although many methods,
structures and materials similar, modified, or equivalent to those
described herein can be used in the practice of the present
invention without undue experimentation, the preferred methods,
structures and materials are described herein. In describing and
claiming the present invention, the following terminology will be
used in accordance with the definitions set out below.
As used in this specification and the appended claims, the singular
forms "a", "an," and "the" do not preclude plural referents, unless
the content clearly dictates otherwise.
As used herein, the term "and/or" includes any and all combinations
of one or more of the associated listed items.
As used herein, the term "about" when used in conjunction with a
stated numerical value or range denotes somewhat more or somewhat
less than the stated value or range, to within a range of .+-.10%
of that stated.
As used herein, the term "armor substrate" refers to new and
conventional forms of transparent armor including, without
limitation, laminates of soda-lime or borosilicate glass with
polycarbonate as well as transparent ceramic armor including
aluminum oxynitride ("Alon"), spinel (including nanocrystalline
spinel), and the like, and combinations thereof.
.Iadd.As used herein, "atactic polymer" refers to a polymer
composed of atactic macromolecules, which are regular
macromolecules in which the configurational (base) units are not
all identical..Iaddend.
Description
Elastomeric coatings were found to substantially increase the
ballistic limit of underlying steel armor substrates when applied
to the outside surface (that is, the "strike-face") with a
composite array of elastomer-steel panels enjoying increases armor
penetration resistance, as reported in Roland et al.,
"Elastomer-steel laminate armor" Composite Structures 92 (2010)
1059-1064, incorporated herein by reference.
Various coatings including polyurea and butyl rubber have shown to
function well in this application, and the coating itself may
include a combination of materials.
FIG. 1 shows the increase in average velocity required to penetrate
armor (V-50) due to the presence of a 19 mm polyurea coating. The
coating contribution to penetration resistance systematically
increases with increasing substrate hardness. On steel substrates,
mass efficiencies exceeding a factor of two have been achieved.
With regard to conventional transparent armor, thicker panels are
required to achieve higher ballistic performance, with a
concomitant weight penalty which is especially undesirably in the
case of vehicles, adversely impacting performance, fuel economy,
and payload, while the bulkier panels impinge on interior space.
Furthermore, conventional transparent armor can be prone to
environmental abrasion or scratching, reducing transparency and
requiring costly and time-consuming repair.
This armor system may be applied to vehicles including manned or
unmanned vehicles suitable for travel on the ground, or in the air,
on the surface of water or underwater, and combinations thereof. It
may be used in windows, windscreens, viewing ports, and the
like.
As described herein, a transparent armor system includes a polymer
coating applied to a transparent armor substrate. The density by
area of this transparent armor system can be less than that of
conventional armor systems while providing equal or greater
protection.
The protective function of the coating is believed to arise from an
impact-induced phase transition with consequent large energy
absorption, so that the substrate should be stiff enough to allow
rapid compression of the coating. Atactic polypropylene with a
glass transition temperature of about -20.degree. C. functions as a
suitable coating due to this phenomenon, while providing the
desired transparency.
Armor Substrate
The armor substrate is preferably transparent and with sufficient
rigidity and hardness to support the coating while also itself
resisting penetration. Most preferably, the armor substrate has a
hardness of at least 150, 200, 300, 400, 500 , or more, as measured
using the Brinell method with a tungsten ball of 10 mm diameter and
3,000 kg force.
The armor substrate may be one or more new or conventional forms of
transparent armor including, without limitation, laminates of
soda-lime or borosilicate glass with polycarbonate and transparent
ceramic armor including aluminum oxynitride ("Alon"), spinel
(including nanocrystalline spinel), and the like, and combinations
thereof. Nanocrystalline ceramic material that might be suitable
for use as an armor substrate is described in commonly-owned U.S.
Provisional Patent Application No. 61/907,440 filed on Nov. 22,
2013, incorporated herein by reference.
Traditional bullet-resistant glass is available with coatings under
the trade names MARGARD and MAKROLON intended to improve scratch
resistance. The present armor system may be used with any such
forms of coated transparent substrates, termed secondary coatings
to distinguish them from the atactic polypropylene coating of the
invention. It is believed that hard coatings may increase the
effective hardness of the glass, thus improving performance of the
system as seen in FIG. 1. The polypropylene coating senses the
hardness of the substrate of length-scales commensurate with the
wavelength of the longitudinal pressure wave--this may guide the
design of the thickness of a secondary coating.
Coating
The polymeric coating is preferably atactic polypropylene. It was
found that isotactic polypropylene would crystallize and fail to
provide the desired ballistic performance. A suitable molecular
weight may be from about 40 to about 80 kilograms/mol for an
atactic polypropylene polymer. In preparing the polymer, it should
be cooled quickly to avoid formation of crystals large enough to
scatter visible light.
The coating thickness may range, for example, from about 0.25 cm to
about 2.0 cm.
The coating may be bonded to the armor substrate using various
techniques. It may be in direct contact with the armor substrate or
bonded thereto via an intermediate adhesive. It may be cast into
place on the armor substrate. Mechanical bonding may be used, for
example using a frame, clamps, bolts, or other fasteners. A
combination of bonding techniques may be used.
An advantage of this transparent polymeric coating is its
reversible solidification (as opposed to solidification via a
practically irreversible chemical change in other polymers). Thus,
abrasions and scratches may be removed by heating, optionally while
contacting the surface of the polymer with a smooth surface. It was
found that a temperature of about 100.degree. C. was sufficient to
repair atactic polypropylene. Such repairs could easily be made in
the field.
Concluding Remarks
All documents mentioned herein are hereby incorporated by reference
for the purpose of disclosing and describing the particular
materials and methodologies for which the document was cited.
Although the present invention has been described in connection
with preferred embodiments thereof, it will be appreciated by those
skilled in the art that additions, deletions, modifications, and
substitutions not specifically described may be made without
departing from the spirit and scope of the invention. Terminology
used herein should not be construed as being "means-plus-function"
language unless the term "means" is expressly used in association
therewith.
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