Patent Application
20240085152
This invention relates to impact resistant protective materials for increased safety in hostile environments, and more particularly relates to novel combinations of materials which enhance overall performance in comparison to the materials when used independently.
Traditionally, metallurgists have used high quality materials, such as hardened steel, aluminum, titanium, ceramics, and more to create a protective environment for safeguarding life, trade goods, and other items of value. Over many millenia, significant expenditures have been made in this effort by both countries and individuals. In 2019 near $2 trillion, a global average of 2.2% of all countries' gross domestic product, was spent on military defense. These expenditures include workforce, procurement of needed equipment, and advanced research and development.
Generally, steel is the most widely used material to protect valuables from impact. Through decades of research, many steel grades have been tested, standardized, and rated for performance. The US Dept of Defense has created military details (MIL DTL) for various levels of protection. These include MIL DTL 12560 for rolled homogeneous armor (RHA) with a Brinell hardness near 370. MIL DTL 46100 explains the requirements for 500 Brinell high hard armor (HHA) plate. MIL DTL 32332 is the most recent specification delineating the benchmarks for ultra hard armor (UHA) at 600 Brinell. Each of these MTh DTLs have various sub classes based on specific performance criteria. Additionally, each of these MIL DTLs has multiple revisions to encapsulate recent developments in armor performance. MIL DTLs 12560, 46100, and 32332, at their current revision level, are included herein in their entirety for reference.
Depending on the thickness of the steel armor, each MIL DTL prescribes what ballistic threat should be used for testing. A tabulation is included that provides an armor plate thickness, the testing round to be fired at the armor, and the velocity required for a passing result. Bullets include M80 ball round, M2 armor piercing (AP) rounds, .30 caliber fragmentation simulating penetrators (0.30-cal FSP), .50 caliber fragmentation simulating penetrators (0.50-cal FSP), and 20 millimeter fragmentation simulating penetrators (20 mm FSP) to name just a few of the many. While the bullets are representative of the actual threat, the FSP rounds are a standardized construction meant to represent a large piece of metal that could be encountered in the flurry of metallic pieces that armor could be impacted by in a blast event.
Each of these MIL DTLs spells out performance against various ballistic and blast fragment threats. The softest steel armor, RHA, is known for its nominal resistance to AP rounds while excelling at resistance to blast fragments and forces. In comparison to RHA, the harder HHA provides increased protection against AP rounds and, in thicknesses near 6.4 mm, offers increased protection from 20 mm FSP. However, when thickness of the required armor exceeds 12.7 mm, RHA offers better protection than HHA against 20 mm FSP. The UHA, hardest of all steel armors, offers yet further increased protection against AP rounds. Being harder, UHA has a more brittle tendency and is well known to be a poor performer against 20 mm FSP, blast fragments, and blast forces. Provided the various optimal performance of each armor, they can be used in differing locations of an armored vehicle to optimize protection. For example, since blast forces often arise from the ground, 25 mm thick sections of RHA could be used in the floor construction. HHA, at 6.4 mm to 9.5 mm is often used in the bodyside construction of vehicles to offer midrange protection from bullets while retaining some level of blast fragment protection. UHA, with minimal blast fragment resistivity performance, is the best candidate for the vehicle roof. Being higher performing against bullets, thinner UHA is not needed to protect from ground borne blast fragments and forces. Thinner, lighter UHA also keeps the vehicle center of gravity lower than heavier RHA would.
The defense industry prides itself on many generations of development using various grades of armor to make the lightest, most protective vehicles. In the 21st century, vehicle builders have focused on a layered approach to armored protection. The basic vehicle hull, called the A-cab, is typically constructed of a single steel thickness, often 6.4 to 9.5 mm. The A-cab provides a basic level of protection which is similarly safe as the typical armored trucks used by the banking industry. To enhance protection, a material solution known as the B-kit can be added. The B-kit is often comprised of various layers of metals, ceramics, epoxies, and bullet resistant fabrics like kevlar. B-kits are mostly bolted to the doors of the vehicle and other areas where passengers are at most risk. In some cases, a thicker and higher performance C-kit is installed rather than, or in addition to, a B-kit. Both B-kits and C-kits often have components, like ceramics, that are extremely hard and encapsulated within the kit itself. Defense industry vernacular often calls the internal components of the B-kit or C-kit as the “cake batter”. A component known as a strike face is the outermost surface of the B-kit and C-kit which is designed to protect the inner components. This strike face has the ability to deflect hand gun or non-armor piercing rounds while keeping the inner cake batter ready to protect against higher powered rounds and blast events. It is also widely accepted that the strike face should be made from at least HHA and often UHA to offer a higher hardness for initial bullet and impact stopping power combined with the multi hit capability of steel. Using softer materials is not considered viable as they can be easily damaged by minor impact events from pistols or even thrown rocks and then allow damage to the encapsulated ceramic, kevlar, and the like which constitutes the cake batter.
Measuring the weight of an armored solution can be difficult when the components of the cake batter have differing densities. In single material solutions, calculating the armor's mass per square foot is a simple math problem. Known as the areal density, the defense industry measures the weight of armored solutions in pounds per square foot (psf). For example, steel at ¼″ thick has an areal density of 10.2 psf which is calculated by 12″ wide×12″ long×¼″ thick×0.284 pounds per cubic inch density. An aluminum plate of the same dimensions would have an areal density of only 3.6 psf. While the aluminum plate is only 35% of the steel's mass, the aluminum plate only has about 20% of the ballistic and energy resistance. Both the aluminum and steel are known to be able to absorb multiple impacts without compromising the integrity of the metal a few inches away from the point of impact. This multi-hit capability is important in vehicle construction for long term robustness. Ceramics are known to have even lower areal densities than metals, significantly higher ballistic impact performance, but lack a general multi-hit capacity and are prone to cracking both visually and internally, thus compromising their performance.
In accordance with the present invention, testing has found that an unexpected combination of a hard armor plate in combination with a softer material front plate can offer significantly increased protection against impact events than the harder armor plate alone can provide. This is a very counterintuitive and novel combination because it has always been believed that the hardest material should be the front strike face which is first material contacted by the incoming projectile. Traditionally, the hardest fronting strike face will break up the incoming projectile allowing the softer backing material to absorb and dissipate energy and projectile remnants. In the present invention, starting with the areal density of the hard back plate alone, increasing the combination armor solution's areal density by as little as 2% by adding the softer front plate has improved ballistic performance by more than 10%. Depending on the configuration of the soft front plate, an increase in areal density of 3 to 10% can provide up to 60% improvement over the ballistic performance of the harder backing plate alone. Front plates in tested examples ranged in thickness from 0.040″ to 0.127″ thick made of perforated aluminum with 50% hole reduction or simple sheets of plastic. The front plate in these examples have a bulk material density of up to 3 grams per cubic centimeter but a front plate with up to 5 or even 8 grams per cubic centimeter fronting a harder backing plate would offer improved protection from penetration as well. Further, the front plate will have a maximum areal density of 4 psf.
In accordance with the present invention, herein is disclosed a superior impact resistant material and methods therefore. In that regard, ballistic performance is measured by the velocity and type of projectile impacting the armor solution. The velocity 50th percentile, known as the V50 protection limit, for armor plate is defined as the average velocity of six impacts, of a maximum of ten total rounds fired at the armor, in which the three lowest velocity complete penetrations (CP) and the three highest incomplete penetrations, known by industry as partial penetrations (PP), are averaged. Further, the total spread between the three highest velocity partial penetrations and the three lowest velocity complete penetrations must be less than 150 feet per second per the US Army MIL DTLs. For example, the US Army armor performance specification MIL DTL 32332A, incorporated herein in its entirety, further clarifies the V50 requirement against .30 caliber M2 armor piercing rounds to be 2465 fps V50 performance for 0.25″ (6.35 mm) thick plates made of UHA steel. As specified in MTh DTL 32332A, reduced thicknesses of UHA will have lower V50 requirements while thicker pieces will have higher V50s.
Various ballistic performance tests were performed at NTS Chesapeake in Belcamp, Maryland. Examples of findings, based on Flash Processed Ultra Hard Armor (UHA), include:
A 0.147″ thick 6.0 psf plate of UHA had a V50 of 2045 fps against 0.30-cal FSP baseline test case #1.
A 0.147″ thick 6.0 psf plate of UHA fronted by a 0.29 psf, 0.058″ thick high density polyethylene plastic had a V50 of 2547 fps against 0.30-cal FSP for the 6.29 psf combination solution.
A 0.147″ thick 6.0 psf plate of UHA fronted by a 0.35 psf, 0.069″ thick ultra high molecular weight polyethylene plastic had a V50 of 2560 fps against 0.30-cal FSP for the 6.35 psf combination solution.
A 0.147″ thick 6.0 psf plate of UHA fronted by a 0.56 psf, 0.115″ thick ultra high molecular weight polyethylene plastic had a V50 of 2791 fps against 0.30-cal FSP for the 6.56 psf combination solution.
A 0.147″ thick 6.0 psf plate of UHA fronted by a 0.64 psf, 0.127″ thick high density polyethylene plastic at had a V50 of 2794 fps against 0.30-cal FSP for the 6.64 psf combination solution.
A 0.148″ thick 6.0 psf plate of UHA fronted by a 0.6 psf, 0.079″ thick perforated aluminum sheet (51% open area, 3/16″ holes) had a V50 of 2661 fps against 0.30-cal FSP for the 6.6 psf combination solution.
A 0.148″ thick 6.0 psf plate of UHA fronted by a 0.9 psf, 0.129″ thick perforated aluminum sheet (51% open area, 3/16″ holes) had a V50 of 2903 fps against 0.30-cal FSP for the 6.9 psf combination solution.
Two stacked plates of 0.260″ thick 10.6 psf UHA (21.2 psf)) had a V50 of 3700 fps against 0.50-cal FSP for baseline test case #2.
Two stacked plates of 0.260″ thick 10.6 psf UHA (21.2 psf) fronted by a 0.9 psf, 0.125″ thick perforated aluminum sheet (51% open area, 3/16″ holes) had a V50 of 4150 fps against 0.50-cal FSP for the 22.1 psf combination solution.
Three stacked plates of 0.260″ thick 10.6 psf UHA (31.8 psf)) had a V50 of 3157 fps against 20 mm FSP for baseline test case #3.
Three stacked plates of 0.260″ thick 10.6 psf UHA (31.8 psf) fronted by a 0.9 psf, 0.125″ thick perforated aluminum sheet (51% open area, 3/16″ holes) had a V50 of 3906 fps against 20 mm FSP for the 32.7 psf combination solution.
This performance data is tabulated in Table 1.
−1%
In the performance increase column of the chart, two measures of improvement are reviewed. The Velocity VS Mass column is the comparison of the Flash Processed UHA plate with and without the front plate added. This is not a mass efficiency calculation but purely based on the percentage increased velocity of the blast fragment simulating penetrator threats that can be stopped. The mass efficiency, Em VS RHA column, is based on a comparison of the Flash UHA to RHA. In the three rows for the baseline analysis without front plates added, it can be seen that Flash UHA under performs RHA as illustrated by the negative number. Against 0.30-cal FSP, the backing plate alone has 11.6% lower performance than RHA of the same areal density. The combination of two stacked plates of UHA without the fronting material has 1% lower performance than RHA of the same areal density. The combination of three stacked plates of UHA without the fronting material has 5.1% lower performance than RHA of the same areal density. However, when the various front plates are added, in all cases the Flash UHA with front plate, at a lower areal density, outperforms RHA at higher areal density. This performance increase spans multiple common hard armor thicknesses ranging from 0.144″ to 0.780″. Projectiles tested ranged in size from 0.30-cal to 20 mm FSPs demonstrating a wide variety of threats.
This aspect is a design of a product for an impact resistant protective material for increased safety in hostile environments that is comprised of providing a hardened backing material with protective properties whose construction includes any combinations of the fabrication techniques, thickness, density, areal density, localized placement of constituent materials, and/or temporal processing to optimize performance of the hardened backing material which could be used singularly to resist impact from attack by ballistic, blast, sonic, directed energy, or similar harmful threats with the ability to penetrate the material and adversely affect the environment behind the hardened backing material. A fronting material is provided, measured to be at least 25% softer in the Brinell scale than the hard backing material, whose construction includes any combinations of the fabrication techniques. thickness, density, areal density, localized placement of constituent materials, and/or temporal processing, and singularly has lower resistance to impact from attack by ballistic, blast, sonic, directed energy, or similar harmful threats designed to penetrate the material and adversely affect the environment than the hardened backing material. The fronting material to the backing material is assembled to create a protective combination that increases the impact threat resistive performance at an aggregate areal density lower than the mass increase that would have been required by simply increasing the thickness of the harder backing material alone to achieve the combination's increased threat resistive performance. In the present aspect, the harder back plate and softer front plate were bolted together. Other means of mechanical fastening of the plates together such as rivets, screws, or clamping would create similar results. Non-mechanical fastening such as brazing, dissimilar metal welding, adhesives, or epoxies are just some of the many other ways to connect together the harder back plate and softer front plate.
Options to the above aspect include a design which employs an aluminum alloy, titanium alloy, plastic, epoxy, rubber, polymer, or other soft materials as the fronting plate. Combinations of material selected from the group of aluminum ahoy, titanium alloy, plastic, epoxy, rubber, polymer, or other soft materials as the fronting plate are possible. It has been found that employing at least one perforated material as the fronting plate is beneficial. This design blunts the impacting blast fragment with the soft front plate which then induces the fragment to deform by flattening the front of the fragment peel back to form a mushroom shape and shied during deformation, increasing its frontal surface area, and spreading out the impact forces by distributing the forces over a larger area making localized forces impacting the protective surface lower reducing loading pressure which makes it easier to defeat the threat. The perforated fronting material acts to contain and mitigate the spread of the shattered remains of the impacting threat forces. The perforated fronting material of aluminum and one or multiple polymer and/or adhesive coating(s) can be applied to adhere the aluminum to the hard backing plate and encapsulate the assembly. The thickness of the hard backing plate can be from 0.020″ to 8″ thick. The thickness of the front plate as tested has remained less than 0.200″. However, a more preferred application of this aspect may find thicker front plates up to 4″ to perform better against various threats.
Another aspect is an article product which acts as an impact resistant protective material for increased safety against impacting forces in hostile environments that is comprised of an iron based alloy in excess of 535 Brinell hardness whose incoming energy absorption defeat mechanism employs the highest energy absorbing physical mechanics of bulge, crack, and petal to absorb and dissipate the energy from the impacting force. Other materials prior to this invention with hardness greater than 535 Brinell are known to fail by shear plugging and catastrophic cracking in which the impact forces punch a hole through the iron based alloy in the shape of the impacting force or crack the impacted material like untempered plate glass. The present aspect of the article product of this current invention could be comprised of a singular piece of iron based alloy that is 0.020″ to 1.500″ thick. Alternatively in this aspect, the article could be comprised of multiple pieces, or layers, of the iron based alloy stacked together in which the front piece/layer upon being impacted by a force will degrade the impacting force distributing the impact energy at a diameter larger than the impacting force followed by the residual impact forces causing a bulge, crack, and petal in the subsequently impacted layer. This pattern of impacting force degradation, bulge, crack, petal will continue to absorb impacting forces through each layer of the article until the energy is fully dissipated by subsequent pieces/layers or the forces penetrating through the final piece/layer. The impacting force could be an explosive blast fragment, depicted as a fragmentation simulating penetrator known as an FSP, which upon impact causes the fragment's leading contact surface to change its form and peel back similar to how a banana's outer layer peels back to expose the edible portion. While the outer surface peels and folds back, the internal part of the fragment, representative of the edible banana, disintegrates on impact with the iron based alloy plate.
The notion of bulge, crack, petal is often thought of in respect to ballistic performance when a bullet or blast impacts a plate of armor. Similar threats to material performance exist in the heavy construction industry where vehicles like dump trucks have their beds getting loaded with heavy materials that can similarly get damaged by incoming forces. Larger diameter boulders weighing hundreds of pounds can impart significant forces on the hardened steel plate used to construct the bed of a dump truck. The same bulge, crack, petal effects can happen in the production of steel, stamping presses, agricultural equipment, the shipping industry, and many other applications in which high forces are impacted on hardened steel plate. In all of these examples and many more, an iron based alloy plate hardened to 535 Brinell or harder that has the ability to absorb energy through the bulge, crack, petal mechanism would increase performance over plates that fail by shear plugging and cracking. In this aspect, an iron based alloy such as carbon steel, alloy steel, stainless steel, super alloys, and phosphoric iron are some of the many iron based alloys that can have in excess of 535 Brinell hardness to perform with bulge, crack, petal energy absorption
All of this results in an article which acts as an impact resistant protective material for increased safety against impacting forces in hostile environments. The present invention includes an iron based alloy in excess of 535 Brinell hardness whose incoming energy absorption defeat mechanism employs the highest energy absorbing physical mechanics of bulge, crack, and petal to absorb and dissipate the energy from the impacting force. Such a material includes a singular piece of iron based alloy that is 0.020″ to 1.500″ thick in combination with at least one more layer or multiple pieces, or layers, of the iron based alloy stacked together in which the front piece/layer upon being impacted by a force will degrade the impacting force distributing the impact energy at a diameter/size larger than the impacting force followed by the residual impact forces causing a bulge, crack, and petal in the subsequently impacted layer. This pattern of impacting force degradation, bulge, crack, petal will continue to absorb impacting forces through each layer of the article until the energy is fully dissipated by subsequent pieces/layers or the forces penetrate through the final piece/layer. The iron based alloy plate causes the impacting force of an explosive blast fragment, depicted as a fragmentation simulating penetrator known as an FSP, which upon impact causes the fragment's leading contact surface have material removed to change its form and peel back similar to how a banana's outer layer peels back to expose the inner, edible portion. While the outer surface of the FSP peels and folds back, the internal part of the fragment, representative of the edible banana, disintegrates on impact with the iron based alloy plate.
In this aspect of the present invention, the iron based alloy may be any suitable steel including carbon steel, alloy steel, stainless steel, super alloys, phosphoric iron or combinations of multiple layers of these materials acting as back plates. In combination with the back plate is a softer fronting plate or fronting plates. The back plate and fronting plate may be assembled together using bolts, rivets, screws, clamping, brazing, dissimilar metal welding, adhesives, or epoxies, or they may simply layered.
An aluminum alloy may be employed as the fronting plate, as well as plastic, epoxy, titanium alloy, rubber, polymer, or other soft materials as the fronting plate. Furthermore, preferred materials may be selected from the group of aluminum, titanium, plastic, epoxy, rubber, polymer, and other soft materials as the fronting plate.
In yet another aspect, at least one perforated material is preferred as the fronting plate. The impacting blast fragment is blunted by the soft front plate which then induces the fragment to deform by flattening the front of the fragment to peel back to form a mushroom shape and shred during deformation, increasing its frontal surface area, and spreading out the impact forces by distributing the forces over a larger area making localized forces impacting the protective surface lower reducing loading pressure which makes it easier to defeat the threat. The perforated fronting material acts to contain and mitigate the spread of the shattered remains of the impacting threat forces. In a preferred aspect, the perforated fronting material is aluminum and a polymer coating is applied to adhere the aluminum to the hard backing plate, and may encapsulate the assembly.
Also in the present invention, a method to create an impact resistant protective material for increased safety in hostile environments includes the steps of providing a hardened backing material with protective properties whose construction includes any combinations of the fabrication techniques, thickness, density, areal density, localized placement of constituent materials, and/or temporal processing to optimize performance of the hardened backing material which could be used singularly to resist impact from attack by ballistic, blast, sonic, directed energy, or similar harmful threats designed to penetrate the material and adversely affect the environment behind the hardened backing material, providing a fronting material, measured to be at least 25% softer in the Brinell scale than the hard backing material, whose construction includes any combinations of the fabrication techniques, thickness, density, areal density, localized placement of constituent materials, and/or temporal processing, and singularly has lower resistance to impact from attack by ballistic, blast, sonic, directed energy, or similar harmful threats designed to penetrate the material and adversely affect the environment than the hardened backing material, and assembling the fronting material to the backing material to create a protective combination that increases the impact threat resistive performance at an aggregate areal density lower than the mass increase that would have been required by simply increasing the thickness of the harder backing material alone to achieve the combination's increased threat resistive performance.
The foregoing description of a preferred aspect of the inventions have been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Obvious modifications or variations are possible in light of the above teachings with regards to the specific aspects. Thicker and thinner hardened back plates in combination with thicker and thinner soft front plates of various materials are the most obvious variations. The aspect was chosen and described in order to best illustrate the principles of the invention and its practical applications to thereby enable one of ordinary skill in the art to best utilize the invention in various aspects and with various modifications as are suited to the particular use contemplated.
The present invention finds applicability in the defense and construction industries and finds particular utility for use in the fabrication of protective vehicles and enclosures by providing a lightweight solution that offers higher impact resistance performance.
This application claims the benefit under 35 U.S.C. 119(e) of U.S. Provisional Application No. 63/136,283 filed on Jan. 12, 2021.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2022/020247 | 3/14/2022 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 63136283 | Jan 2021 | US |
