U.S. patent application number 14/121210 was filed with the patent office on 2016-12-15 for reinforced ceramic tile armor.
The applicant listed for this patent is James Sorensen. Invention is credited to James Sorensen.
Application Number | 20160363418 14/121210 |
Document ID | / |
Family ID | 57516852 |
Filed Date | 2016-12-15 |
United States Patent
Application |
20160363418 |
Kind Code |
A1 |
Sorensen; James |
December 15, 2016 |
Reinforced ceramic tile armor
Abstract
A ceramic armor is disclosed that utilizes a titanium frame
assembly surrounding monolithic ceramic tiles combined with
aluminum pressure infiltration. The aluminum pressure infiltration
serves to "wet" the ceramic, bonding the ceramic to the titanium
frame on the top, bottom, sides and interior of the frame assembly.
After aluminum pressure infiltration at high temperature followed
by cooling, this combination creates compressive stress in all
directions surrounding the ceramic thereby enhancing localization
of a blast/projectile hit to enhance the armors effectiveness. Even
after damage due to a projectile hit, adjacent tiles retain their
structural integrity, residual stress, and bond to the frame
assembly.
Inventors: |
Sorensen; James; (Eagan,
MN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Sorensen; James |
Eagan |
MN |
US |
|
|
Family ID: |
57516852 |
Appl. No.: |
14/121210 |
Filed: |
August 12, 2014 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F41H 5/0421 20130101;
F41H 5/0492 20130101 |
International
Class: |
F41H 5/04 20060101
F41H005/04 |
Claims
1. A ceramic armor comprising: a plurality of dense ceramic core
tiles having a plurality of side surfaces, each of said plurality
of dense ceramic core tiles having a top and bottom surface; an
interconnected frame assembly, said frame assembly including an
interior having a plurality of cells, said cells including a
plurality of walls, said tiles disposed within said plurality of
cells, said plurality of walls and said plurality of tile side
surfaces having a gap therebetween of at least 0.0005 inches, said
frame assembly further including side rails surrounding said
plurality of cells, said side rails and said periphery of said
plurality of cells having a gap therebetween of at least 0.0005
inches; at least one top plate and at least one backing plate
having a top and bottom surface, said top plate bottom surface and
said top surface of said plurality of dense ceramic core tiles
having a gap therebetween of at least 0.0005 inches, said backing
plate top surface and said bottom surface of said plurality of
dense ceramic core tiles having a gap therebetween of at least
0.0005 inches; a metallic material encapsulating said plurality of
cells, said top plate said backing plate, and said side rails, said
metallic material infiltrating said gap between said plurality of
said tile side surfaces and said plurality of cell walls forming a
bond therebetween, infiltrating said gap between said side rails
and said periphery of said plurality of cells forming a bond
therebetween, infiltrating said gap between said top plate bottom
surface and said top surface of said plurality of dense ceramic
core tiles forming a bond therebetween, and infiltrating said gap
between said backing plate top surface and said bottom surface of
said plurality of dense ceramic core tiles forming a bond
therebetween, wherein the CTE of said frame assembly, said top
plate and said backing plate, is greater than the CTE of said
plurality of said ceramic core tiles, said plurality of dense
ceramic core tiles being under compressive stress.
2. A ceramic armor as in claim 1, wherein said metallic material
infiltrant has a shear strength exceeding 25 MPa, a tensile
strength exceeding 50 MPa, and a melting point less than 900
degrees celcius.
3. A ceramic armor as in claim 1, wherein said frame assembly, said
top plate and said backing plate are titanium.
4. A ceramic armor as in claim 3, wherein the CTE of said frame
assembly, said top plate and said backing plate is at least 2.5
times greater than the CTE of said plurality of said ceramic core
tiles, said plurality of dense ceramic core tiles being under
compressive stress.
5. A ceramic armor as in claim 3, wherein said yield strength of
said titanium is at least 900 MPa.
6. A ceramic armor as in claim 5, wherein said yield strength of
said titanium frame assembly is increased with said metallic
material bonding, said bonding of said metallic material throughout
said ceramic armor preserving said compressive state of said
plurality of tiles adjacent to a projectile hit.
7. A ceramic armor as in claim 3, wherein said titanium walls are
at least 0.010 inches thick.
8. A ceramic armor as in claim 5, wherein said side rails further
include ports for the distribution of said metallic infiltrant
throughout the ceramic armor.
9. A ceramic armor comprising: a plurality of dense ceramic core
tiles, having a plurality of side surfaces each of said plurality
of dense ceramic core tiles having a top and bottom surface; an
interconnected frame assembly, said frame assembly including an
interior having a plurality of cells, said cells including a
plurality of walls, said tiles disposed within said plurality of
cells, said plurality of walls and said plurality of tile side
surfaces having a gap therebetween of at least 0.0005 inches, said
frame assembly further including side rails surrounding said
plurality of cells, said side rails and said periphery of said
plurality of cells having a gap therebetween of at least 0.0005
inches; a metallic material encapsulating said plurality of cells,
and said side rails, said metallic material infiltrating said gap
between said plurality of said tile side surfaces and said
plurality of cell walls forming a bond therebetween, infiltrating
said gap between said side rails and said periphery of said
plurality of cells forming a bond therebetween.
10. A ceramic armor as in claim 9, further including: at least one
top plate and at least one backing plate having a top and bottom
surface, said top plate bottom surface and said top surface of said
plurality of dense ceramic core tiles having a gap therebetween of
at least 0.0005 inches, said backing plate top surface and said
bottom surface of said plurality of dense ceramic core tiles having
a gap therebetween of at least 0.0005 inches; a metallic material
encapsulating said at least one top plate and at least one backing
plate, said metallic material infiltrating said gap between said
top plate bottom surface and said top surface of said plurality of
dense ceramic core tiles forming a bond therebetween, and
infiltrating said gap between said backing plate top surface and
said bottom surface of said plurality of dense ceramic core tiles
forming a bond therebetween.
11. A ceramic armor as in claim 9, wherein said metallic material
infiltrant has a shear strength exceeding 25 MPa, a tensile
strength exceeding 50 MPa, and a melting point less than 900
degrees celcius.
12. A ceramic armor as in claim 10, wherein said frame assembly,
said top plate and said backing plate are titanium.
13. A ceramic armor as in claim 12, wherein said yield strength of
said titanium is at least 900 MPa.
14. A ceramic armor as in claim 9, wherein said yield strength of
said frame assembly is increased with said metallic material
bonding, said bonding of said metallic material throughout said
ceramic armor preserving said compressive state of said plurality
of tiles subsequent to a projectile hit.
15. A ceramic armor as in claim 12, wherein said titanium walls are
at least 0.010 inches thick.
16. A ceramic armor as in claim 9, wherein the CTE of said frame
assembly is greater than the CTE of said plurality of said ceramic
core tiles, said plurality of dense ceramic core tiles being under
compressive stress.
17. A ceramic armor comprising: a plurality of dense ceramic core
tiles having a plurality of side surfaces, each of said plurality
of dense ceramic core tiles having a top and bottom surface; an
interconnected frame assembly, said frame assembly including an
interior having a plurality of cells, said cells including a
plurality of walls, wherein said walls are at least 0.010 inches
thick, said tiles disposed within said plurality of cells, said
plurality of walls and said plurality of tile side surfaces having
a gap therebetween of at least 0.0005 inches, said frame assembly
further including side rails surrounding said plurality of cells,
said side rails and said periphery of said plurality of cells
having a gap therebetween of at least 0.0005 inches; at least one
top plate and at least one backing plate having a top and bottom
surface, said top plate bottom surface and said top surface of said
plurality of dense ceramic core tiles having a gap therebetween of
at least 0.0005 inches, said backing plate top surface and said
bottom surface of said plurality of dense ceramic core tiles having
a gap therebetween of at least 0.0005 inches; wherein said frame
assembly, said top plate and said backing plate are titanium, said
titanium having a yield strength of at least 900 MPa; a metallic
material encapsulating said plurality of cells, said top plate,
said backing plate, and said side rails, wherein said metallic
material has a shear strength exceeding 25 MPa, a tensile strength
exceeding 50 MPa, and a melting point less than 900 degrees
celcius, said metallic material infiltrating said gap between said
plurality of said tile side surfaces and said plurality of cell
walls forming a bond therebetween, infiltrating said gap between
said side rails and said periphery of said plurality of cells
forming a bond therebetween, infiltrating said gap between said top
plate bottom surface and said top surface of said plurality of
dense ceramic core tiles forming a bond therebetween, and
infiltrating said gap between said backing plate top surface and
said bottom surface of said plurality of dense ceramic core tiles
forming a bond therebetween; wherein the CTE of said frame
assembly, said top plate and said backing plate, is at least 2.5
times greater than the CTE of said plurality of said ceramic core
tiles, said plurality of dense ceramic core tiles being under
compressive stress; wherein said yield strength of said titanium
frame assembly is increased with said metallic material bonding,
said bonding of said metallic material throughout said ceramic
armor preserving said compressive state of said plurality of tiles
subsequent to a projectile hit.
18. A ceramic armor as in claim 1 wherein said bonding infiltrant
is aluminum.
Description
BACKGROUND
[0001] 1. Field of Use
[0002] The present invention relates to ceramic armor produced by
metallic encapsulation and structural reinforcement for increased
structural integrity against blast/projectile hits.
[0003] 2. Description of Prior Art
[0004] Ceramic containing armor has been shown to be an effective
means to protect against a wide variety of ballistic threats
because of its combination of high hardness, strength and stiffness
along with low bulk density and favorable pulverization
characteristics upon impact. Ceramic materials have long been
considered for use in the fabrication of armor components because
ceramic materials have a high hardness, are potentially capable of
withstanding armor-piercing projectiles, and are relatively
lightweight.
[0005] However, the use of ceramic materials in armor applications
has been limited by the low impact resistance of these materials,
which results from ceramic's brittleness and lack of toughness.
Indeed, one of the significant drawbacks to the use of ceramic
materials in armor applications is that they lack repeat hit
capability. In other words, ceramic materials tend to disintegrate
upon the first hit and cease to be useful when subjected to
multiple projectiles.
[0006] For armor systems arranged in an array type structure,
multiple projectile hits tend to disintegrate adjacent ceramics,
propagating the hit throughout the structure. For a more effective
utilization of ceramic materials in armor applications, it is
necessary to improve the impact resistance of this class of
materials.
[0007] Applicants have found that the use of a Titanium frame
assembly surrounding monolithic ceramic tiles combined with
aluminum pressure infiltration serves to "wet" the ceramic, bonding
the ceramic to the titanium frame on the top, bottom, sides and
interior of the frame assembly. After aluminum pressure
infiltration at high temperature followed by cooling, this
combination creates compressive stress in all directions
surrounding the ceramic thereby enhancing localization of a
blast/projectile hit to enhance the armors effectiveness. Even
after damage due to a projectile hit, adjacent tiles retain their
structural integrity, residual stress, and bond to the frame
assembly.
[0008] Since the coefficient of expansion for titanium is higher
than the CTE of the ceramic tiles, the cooling puts additional
compressive stress on the ceramic tiles. In the present invention,
the adjacent tiles are bonded to the top plate, bottom plate and
side walls of titanium. So, when the middle tile is destroyed the
surrounding tiles are still held in place and residual compression
stress is maintained because the entire module is bonded into an
integral structural system.
[0009] Prior art methods of construction such as the Hot Isostatic
Pressure (HIP) process do not allow for adequate bonding of the
ceramic to the frame assembly. The HIP process is where metal
castings or other metal objects are squeezed at high temperature
and high pressure to collapse any porosity present. Current
titanium encapsulated, ceramic armor is made by fabricating a
titanium structure with cavities, then placing ceramic tiles into
the cavities. The HIP process heats the titanium encapsulated armor
to about 950C and then pressurizes it to between 15,000 and 30,000
psi. This combination of heat and pressure softens the titanium and
collapses the entire module, thus removing any gaps or porosity
between the tiles and titanium, unlike the present invention. Then
as the module cools the titanium shrinks.
[0010] In addition to not being able to control the defects
(wrinkling, etc) inherent in the HIP process, the titanium does not
bond to the ceramic tiles, and when the completed armor is struck
by a projectile, the ceramic tile is shattered and reduced to
rubble. The titanium walls surrounding that tile are not bonded to
the surrounding tiles, so the residual compression that existed
before the projectile impact is partially relieved for the
adjacent, surrounding tiles.
SUMMARY OF THE INVENTION
[0011] The present invention relates to a ceramic armor utilizing a
titanium frame assembly surrounding monolithic ceramic tiles
combined with aluminum pressure infiltration. The aluminum pressure
infiltration serves to "wet" the ceramic, bonding the ceramic to
the titanium frame on the top, bottom, sides and interior of the
frame assembly. After aluminum pressure infiltration at high
temperature followed by cooling, this combination creates
compressive stress in all directions surrounding the ceramic
thereby enhancing localization of a blast/projectile hit to enhance
the armors effectiveness. Even after damage due to a projectile
hit, adjacent tiles retain their structural integrity, residual
stress, and bond to the frame assembly.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The foregoing and other objects, features, and advantages of
the invention are apparent from the following detailed description
taken in conjunction with the accompanying drawings in which:
[0013] FIG. 1 shows a schematic cross-sectional representation of
an armor construction encapsulating a plurality of ceramic tiles in
accordance with the teachings of the present invention.
[0014] FIG. 2 illustrates a portion of the frame assembly used in
the armor construction of FIG. 1. FIG. 3 illustrates the tiles that
are fitted into the cells of the frame assembly of FIG. 2.
[0015] FIG. 4 is a top view of the frame assembly of FIG. 2 with
the tiles of FIG. 3 fitted therein.
[0016] FIG. 5 is a bottom view of FIG. 4.
[0017] FIG. 6 is an exploded view of one embodiment of the armor
construction in accordance with the teachings of the present
invention.
DETAILED DESCRIPTION
[0018] In the following description, the same numerical references
refer to similar elements. The embodiments, geometrical
configurations, materials mentioned and/or dimensions shown in the
figures or described in the present description are preferred
embodiments only, given for exemplification purposes only.
[0019] In the context of the present invention, any equivalent
expression and/or compound words thereof known in the art will be
used interchangeably, as apparent to a person skilled in the
art.
[0020] It is to be understood, as also apparent to a person skilled
in the art, that other suitable components and cooperations
therebetween, as well as other suitable geometrical configurations
may be used for the armor construction according to the present
invention, as will be explained herein and as can be easily
inferred herefrom, by a person skilled in the art, without
departing from the scope of the invention.
[0021] Furthermore, the order of the steps of the method described
herein should not be taken as to limit the scope of the invention,
as the sequence of the steps may vary in a number of ways, without
affecting the scope or working of the invention, as can also be
understood.
[0022] Referring to FIG. 6, which shows an exploded view of an
embodiment of armor construction 10 made in accordance with the
teachings of the present invention. As illustrated in FIGS. 2, 3
and 6, the armor construction includes a frame assembly 15 with
ceramic plates or tiles 40 placed within the cells 17 of frame
assembly 15. Frame assembly 15 includes side rails 15A and interior
walls 15B connected together to form cells 17.
[0023] Side rails 15A include infiltration ports 15A1 where liquid
infiltrant will enter under pressure. Referring to FIGS. 2 and 6,
walls 15B include tabs 15B1 for engagement of top plate 20 slots
20A. A layer of Saffil paper 22 may be added between top plate 20
and tiles 40, and/or between backing plate 25 and tiles 40. Saffil
paper 22 reduces the likelihood of residual stress cracking between
the ceramic tiles 40 and titanium plates 20,25 placed upon tiles
40.
[0024] A Bottom plate 30 may be added between tiles 40 and backing
plate 25. Bottom plate 30 facilitates the securement of tiles 40
within cells 17. In another embodiment of the present invention,
the bottom plate 30 may be eliminated. In the preferred embodiment
the frame assembly 15, top plate 20, backing plate 25, and bottom
plate 30 are made of titanium. The walls 15B are titanium and at
least 0.010 inches thick.
[0025] As illustrated in FIGS. 2 and 6, bottom plate 30 and top
plate 20 includes slots 20A for engagement of tabs 15B1 located on
the top and bottom of frame assembly 15. Tabs 15B1 are located on
the top and bottom of walls 15B. A cross-section of the armor
construction 10 of FIG. 6, in assembled form is illustrated in FIG.
1. Prior to being placed in an infiltration vessel armor
construction 10 is welded by shield gas tungsten, electron beam or
similar methods at tabs 15B1. The complete assembled armor
construction 10 would be placed in an infiltration vessel or mold
cavity then infiltrated with liquid metal.
[0026] The armor construction 10 should be heated in a vacuum or
shielded with inert gas to prevent oxidation of the titanium
surfaces. The gaps between ceramic tiles 40 and interior walls 15B,
the gap between ceramic tiles 40 and top plate 20, and the gap
between ceramic tiles 40 and backing plate 25, are at least 0.0005
inches, and preferably are between about 0.003 and about 0.008
inches.
[0027] The aluminum infiltration process causes aluminum to
penetrate throughout the overall structure, filling the gaps
between the aforementioned surfaces. The liquid aluminum wets the
titanium and ceramic surfaces creating a bond between them when it
solidifies. After solidification, bonding occurs throughout the
armor construction, specifically between ceramic tiles 40 and
interior walls 15B, between ceramic tiles 40 and top plate 20, and
between ceramic tiles 40 and backing plate 25.
[0028] While molten aluminum is the preferred embodiment
illustrated other suitable metals with a melting point below 900
degrees celcius maybe utilized that do not adversely react with
titanium. A metal with a shear strength exceeding 25 MPa and a
tensile strength exceeding 50 MPa is desirable as the bonding
infiltrant. The infiltrating metal should react sufficiently to wet
the surface of the titanium, but not so much that it creates a
thick, brittle intermetallic reaction bond. The liquid metal
infiltration process is described in U.S. Pat. No. 3,547,180 and
incorporated herein by reference for all that it discloses.
[0029] In each of the embodiments of the present invention, it is
preferred that the ceramic plate or tiles 40 are machined to be
substantially the same width as walls 15B while allowing for tabs
15B1 to be raised enough above tiles 40 for engagement into slots
20A. In the preferred embodiment, only one tile fills cell 17,
however, multiple tiles within each cell can be utilized. In the
preferred embodiment, the layers of material components illustrated
in FIG. 6 are symmetrical in length and width but not
thickness.
[0030] It is preferred that the metal material used for frame
assembly 15 consist of a material having relatively low density,
high strength and good ductility along with a coefficient of
thermal expansion higher than the coefficient of expansion for the
ceramic tiles 40 encapsulated therewithin. Applicants have found
that an alloy of Titanium known as Ti-6A1-4V or Ti-6A1-4V ELI
(Extra Low Interstitials) is a suitable material for this purpose.
Ti-6A1-4V has a relatively low density (4.5 g/cc), relatively high
strength (900 MPa), and good ductility (yield strength of 830 MPa
at 0.2% yield), and can be bought already annealed according to Mil
T 9046 spec.
[0031] The thermal expansion of Ti-6A1-4V is about
10.5.times.10.sup.-6 in/in .degree. C. from 0-600.degree. C., a
coefficient considerably higher than that of dense SiC which has a
thermal expansion coefficient of 4.1.times.10.sup.-6in/in .degree.
C. from 0-600.degree. C., a difference in which the thermal
expansion coefficient for the Titanium alloy is over 21/2 times the
thermal expansion coefficient for the ceramic material.
[0032] In the preferred embodiment of the present invention, the
ceramic material employed may consist of pressure assisted (PAD)
SiC-N, one of a family of Coorstec dense hot pressed ceramics.
Other grades and types of armor ceramics such as Silicon Carbide,
Boron Carbide, Tungsten. Carbide, Titanium Diboride, Aluminum
Oxide, Silicon Nitride and Aluminum Nitride or mixtures of the
aforementioned materials can be employed. Such armor ceramics have
thermal coefficients of expansion from about 3.0.times.10.sup.-6 to
about 9.times.10.sup.-6 in/in .degree. C. and hardness greater than
1100 kg/mm.sup.2.
[0033] There are several advantages to using Titanium as a
surrounding frame assembly 15 material. First, the very high
"yield" strength of Ti can be utilized to constrain the ceramic
core very effectively and impede the material's disintegration.
Herein, the important strength parameter is the "yield" strength of
the surrounding Ti. When the armor package takes a hit, the ceramic
core will tend to fracture and dimensionally expand due to opening
cracks. In this situation, the surrounding metal will be forced to
stretch out and the material's resistance to yielding will be an
important factor in impeding the disintegration of the ceramic
core. Ti-6A1-4V has a yield strength of at least 900 MPa. The
higher the yield strength is the higher resistance against
disintegration forces and provides a more effective constrain.
[0034] The unique combination of a high yield-strength titanium
having an infiltrated bonding metal tends to constrain the ceramic
within a cell after a projectile hit. After aluminum pressure
infiltration at high temperature followed by cooling, this
combination creates compressive stress in all directions
surrounding the ceramic thereby enhancing localization of a
blast/projectile hit to enhance the armors effectiveness. Moreover,
bonding occurs throughout the armor construction, specifically
between ceramic tiles 40 and interior walls 15B, between ceramic
tiles 40 and top plate 20, and between ceramic tiles 40 and bottom
plate 25.
[0035] Even after damage due to a projectile hit, adjacent tiles
retain their structural integrity, residual stress, and bond to the
frame assembly. It has further been observed that a damaged tile
within a cell will not fully deteriorate within the cell after a
projectile hit. Portions of the tile will remain bonded to the
interior walls 15B, top plate 20, and bottom plate 25 even after a
direct hit, due to the bonding of the metal infiltrant throughout
the structure. The residual compression and integrity of the armor
construction 10 may therefore be maintained in cells that have not
yet been penetrated and the integrity of the armor construction 10
can be preserved for multiple hits.
[0036] Another advantage of Ti is the deformation mechanism by
localized shear bands. In the case of ceramic encapsulation, the
deformation of Ti will be limited to a very small portion of the
Ti, which will in effect keep the substantial portion of the Ti
intact. This will allow the Ti to preserve the constraining effect
on the ceramic and improving its effectiveness. In the case of
conventional metal and alloys, the deformation of metallic
component propagates throughout the most the structure and as such
distorts and deprives the constraining action necessary to improve
the effectiveness of ceramic component.
* * * * *