Patent Application
20120291620
This subject matter of the present application relates to light weight armor for ballistic protection of people and vehicles.
It is known in the art to use laminated and/or layered armor panels in order to protect a body from an incoming projectile. Usually, such a laminated armor panel comprises a plurality of layers whose number and characteristics are chosen according to the expected ballistic threat including the parameters of projectiles which the armor is designed to protect the body from.
It is also known to use armor panels by arranging them at an angle to the direction from which a projectile is expected to approach a surface to be protected (which is normally considered to be perpendicular to that surface), thereby causing deflection of the projectile upon impact on the armor.
The following table (Table 1) provides acronyms and abbreviations used in the present application.
Accordnig to one aspect of the subject matter of the present application, there is provided an armor panel configured for protecting a body from an incoming projectile having a movement axis and configured for spinning about said axis, said armor panel comprising a plurality of armor strips attached to each other, said panel having:
wherein said strips are arranged within said armor panel so that at least a majority thereof are oriented transversely to at least said front face of the armor panel,
wherein at least one of the following conditions applies:
wherein the armor panel is configured so that at least during penetration of the spinning projectile into said armor panel, a dynamic friction force between the spinning projectile and said strips exceeds at least one of said Fs1 and Fs2, under at least one of the respective condition (i) and (ii).
More particularly, the armor strips can be attached to each other such that in penetration of the spinning projectile through the armor panel, each armor strip is configured for adhering to the projectile with a greater adherence force that to its neighboring armor strips. In other words, the bonding of the armor strips is such that in penetration of the spinning projectile into the armor panel, the dynamic friction force between the projectile and the armor strips exceeds the static friction force between neighboring armor strips.
Additionally, or alternatively, within a single, armor strip, the material of the armor strip can be chosen such that in penetration of the spinning projectile through the armor panel, the material is configured for adhering to the projectile with a greater adherence force than to neighboring areas of same material. In other words, the material is such that in penetration of the spinning projectile into the armor panel, the dynamic friction force between the projectile and particles of material of the single armor strip exceeds the static friction force between the particles of the material within the single armor strip.
The armor strips can be made out of a material having a high tensile strength. The term ‘high tensile strength’ refers here to a tensile strength which is at least 1 GPa, more particularly at least about 2 GPa, even more particularly at least about 5 GPa, and still more particularly at least about 10 GPa. Furthermore, the armor strips can be made of a material having a high weight to tensile strength ratio.
The armor strips can be fully made out of a continuous material, for example a gel like or a plasticine-like material. Alternatively, the armor strips can comprise fibers.
Provided below are several examples of materials and fibers, that can be used in the armor panel according to the presently disclosed subject matter, along with a denomination of exemplary values of their tensile strength:
In a particular example, the armor strips can be made of a nano particles (NP) based material. In particular, nano particles such as TiS2, WS2, or Carbon Nano Tube (CNT), can be used, which have extremely high strength (for example, ten times higher than steel), very high stiffness, low density, good chemical stability and high thermal and electrical conductivities.
Additional features of the armor strips and of the material used for their manufacture can be:
One advantage of using the nano-fibers referred to above is that, surprisingly enough, it is a unique behavior under which the strength of the armor strip made of such fibers does not change with knots compared to all other fibers tested in the same technique. Such a unique behavior could affect the final composites structure properties and eventually ballistic performance. The nano-fiber is stronger, lighter, safer, and more energy efficient composite products for high performance armor and armor systems.
Another advantage of nano-fibers is that they can provide the armor strips with mechanical properties greater than those used in the industry today. For example compared to regular carbon fibers the elongation of nano-fibers can be 10 times greater, the strength is doubled, the elastic modulus is 3 times greater and the density is lower than 1 gr/cm3 which makes it a light weight material.
It is a special feature of the subject matter of the present application, that the strips are oriented transversely to at least the front face of the armor panel. This orientation will be explained in more detail below, and it should be noted in this connection that in the present application, the term “strip” means a piece of material having two parallel upper and lower surfaces of a length L and a width D, and a thickness t between said surfaces, which meet a condition that the length and the width of the strip are essentially greater than its thickness.
Having the above dimensions, the strips are oriented in the panel so as to have:
Since the armor strips can have two strip surfaces, its face and side rims have two edges formed by the intersections of the rims with the two surfaces.
The armor strips can be stacked in the armor panel and attached to each other by at least one of the following:
When bonded to each other to form the armor panel, at least a majority of the face rims of said armor strips can be aligned with one another, e.g. so as to lie in a plane parallel to or coinciding with the front face of the armor panel. The same can be correct with respect to the strips' rear rims. Consequently at least a majority of the side rims of said armor strips will be aligned with one another, e.g. so as to line in a plane parallel to or coinciding with the panel's side which is perpendicular to the front face of the panel.
As a result, the armor panel can have the following dimensions:
With the above arrangement, in a cross-section of the armor panel taken along a plane perpendicular to the front face thereof, the side rims of the length D have a real-length projection on the cross-sectional plane.
In case fibers are used, the arrangement can be such that in some armor strips the fibers are oriented along the longitudinal dimension of the armor strips, i.e. along dimension L, and in other armor strips, the fibers are oriented along the width dimension, i.e. along dimension D. Such a design can form a bi-directional criss-cross pattern of fibers, facilitating more efficient ballistic resistance of the armor panel.
According to a specific example, the armor strips can be oriented within the armor panel at a slanted orientation, so that the side rims are at an angle to a plane perpendicular to the front face of the panel, and containing the intersection line between the armor strip and the front face. In other words, in the above cross-section, the armor strips appear angled to the front face.
Thus, the armor strips are also slanted with respect to the expected approach direction of incoming projectiles against which the armor panel is configured to protect. The slanting angle of the armor strips can depend on the specific use of the armor panel. According to different examples, the slanting angle can be up to about 80°, more particularly up to about 70°, even more particularly up to about 60°, and still more particularly up to about 45°.
The armor strips can be flexible and/or pliable. The armor panel can be rigid or flexible. It can have, in addition to the stacked-strips body, a front and/or a backing layer, which can further be a part of a wrapping forming an exterior enclosure for the stacked-strips body.
The armor panel can be configured to be, in assembly, free of any rigid armor elements. Examples of such elements can be layers made of steel/ceramic/metal etc.
According to another aspect of the subject matter of the present application there is provided a method for producing an armor panel of the previous aspect, said method comprising:
a) providing a plurality of armor strips, each strip having:
b) attaching said plurality of armor strips to one another such that at least a majority of face rims of the strips are aligned with one another to form a face;
wherein, the armor panel produced by said method has a front face constituted by the aligned face rims of the armor strips, and wherein the width of the front face is equal to the length L of the face rim, and height of the front face is equal to the combined thickness T of the thicknesses t of the armor strips.
In operation of the armor panel and during penetration of the spinning projectile into it, due to the fibrous nature of the armor strips, the fibers adhere to the projectile, while being locally detached from their neighboring fibers, and become knotted together. Thus, the spinning projectile becomes entangled and trapped within the fibrous material, thereby considerably reducing the kinetic energy of the projectile.
In addition, the fibers can have a tensile strength high enough to considerably slow down the spinning projectile as it attempts to progress within the fibrous material together with the fibers entangled thereabout.
Furthermore, the slanting of the armor strips, can cause the projectile impacting the armor panel to become deflected from its initial (straight) movement axis due via a ricochet process. In such case, due to the slanting and certain asymmetries, the projectile is caused to travel along an arc (not a straight line), thereby deflecting it from the body to be protected. The ricochet can even be such that the projectile exits the armor panel without even impacting the body to be protected.
The design of the armor panel of the present application thus affects the trajectory of the incoming projectile, and controls the impact energy on the body to be protected, so that the concept is that there is no reason to defeat a threat but rather to avoid it.
The above design can be adopted for a helmet protection system where the conventional concept could not defeat AP threats, since the residual energy from the impact of the projectile could generate lethal impact to the solider's head. Under the present design, AP threats will be deflected from the protective helmet with no or little residual energy to affect the head of the soldier. Such quantum leap technique could pave the way for the first AP protection helmet.
The same basic new concept can be adapted for personal armor where one can use the fibrous material in order to develop real flexible armor which can stop AP threats level. A similar approach can be used for vehicle armor, etc.
It is estimated that armor of the type described above which is configured for use against EFP threats and AP threats, where one uses only the nano composite as a deflector fully acting as a single member of add-on-armor, this can result in a weight reduction of about 20% compared to current armor solutions.
According to a specific use of the armor panel, it can constitute a spall liner, front layer or backing layer, i.e. working in conjunction with additional ballistic layers of material to form an armor system.
The armor system can comprise a hard front layer (i.e. a layer facing the direction of an expected threat) configured to damage a threat and a back layer configured to absorb the residual energy of the threat after it has impacted the front layer.
The armor panel of the present application can be used either as an add-on armor mounted on a structure, vehicle etc. Alternatively, it may be used as a personal armor such as, for example, vests, helmets etc.
In order to understand the invention and to see how it may be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which:
With reference to
Each armor strip AS has a strip surface of a length L and a width D, wherein the length L is considerably greater than the width D, i.e. L>>D. Each of the armor strips AS also has a thickness t, measured in a direction perpendicular to the strips surface, t being considerably smaller than both D and L, i.e. t<<D, L.
With particular reference being drawn to
Each of the strips 2, 4 has a face rim of length L. The face rim 5 of the D strip 2 is constituted by the combination of cross-sections of the fibers 6 used to form the D strip, whereas the face rim 7 of the L strip 4 is constituted by the length of the outermost fiber 6 constituting the L strip.
As observed from
The armor strips 2, 4 can be simply stacked one on top of the other, but can also be physically attached to each other by such means as: electrostatic connection between the layers, weaving, stitching and bonding using an adhesive matrix (not shown).
As a result, the armor panel 1 is formed with a front face (also referred to as strike face) SF which is constituted by the face rims 5, 7 of the armor strips 2, 4. The armor panel 1 (see
Using different types of armor strips 2, 4 facilitates increasing the ballistic resistance of the armor panel 1 by forming a criss-cross pattern (when viewed perpendicular to the surface of the armor strips AS.
It is observed that in the armor panel 1, the armor strips 2, 4 are arranged such that they are oriented transverse to the impact direction of the projectile PJ. In other words, in a cross-section taken along a plane perpendicular to the front face SF of the armor panel 1 along the height H of the panel 1, the armor strips 2, 4 are seen oriented transverse to the front face SF (see left side view in
In the above example, the armor strip 2, 4 are transverse to the front face SF and are oriented at an angle of 90° thereto (i.e. perpendicular). However, this does not necessary have to be the case as will now be discussed with respect to
With reference to
When the projectile PJ attempts the above, the dynamic friction force FD between the spinning projectile PJ and the fibers 6 of the armor panel 1, 1′ is greater than the static friction force FS2 between the fibers 6 themselves, or than the static friction force FS1 between neighboring armor strips 2, 4.
As a result, the fibers 6 “adhere” to the projectile PJ, and due to its spinning about its axis, become tangle and knotted up with each other. In other words, since the fibers ‘adhere’ to the spinning projectile, they become ‘wrapped’ around it life on a spinning spool.
In the above process, the tensile strength of the fibers plays an important role. Due to the high tensile strength of the fibers 6, the projectile PJ is required to spend more and more energy both on progressing within the knotted and tangle portion of the armor panel 1, 1′ and on spinning. This progression through the knotted fibers accounts for absorption of a considerable amount of the kinetic energy of the projectile PJ.
With reference to
However, contrary to the armor panel 1, in the armor panel 1′ the armor strips are oriented an a slanting angle with respect to the front face SF. According to this specific example, the angle is θ=45°.
Thus, in addition to the previously described penetration process of the projectile into the armor panel 1, in the present example, due to the slanting, the projectile PJ changes its trajectory, at least at first, to become aligned with the direction of the armor strips (i.e. deflecting it by 45°). Thereafter, due to its spinning and inertia, and owing to asymmetric forces, the projectile PJ can continue being deflected so that it essentially moves along an arc instead of along a straight line (i.e. ricocheting from the armor panel). This ricocheting can cause the projectile to exit the armor panel 1′ even without impacting the body to be protected (not shown).
The materials from which the fibers 6 of the armor strips 2, 4 are made are chosen to have a very high tensile strength (up to 10 GPa). For example, the material can be a Carbon Nano Tube (CNT) material (see
It is also noted that in manufacture of armor strips from various materials, e.g. Kevlar®, Dynema etc. knots can be formed by the fibers constituting the material. With reference to
With reference to
Different processes can be used for the manufacture of the fibers 6. In particular, with reference to
The uniqueness of this process is that it is continues allowing the fabrication of a theoretically unlimited long fiber. The transit from a fiber made of CNT to a GNF is possible in the last stage of the fiber pulling where external interference causes the double walled CNT's to collapse forming closely packed Graphene sheets.
It is by understanding the fabrication of the GNF, the characterization is made possible in a short time. The impurities and inconsistencies in the material are linked to various process parameters which could be controlled, changed and optimized.
For example, in the early stages of the reaction, nano particles of iron are formed to serve as catalysts for the formation of CNT's. Excess amounts the precursor used to form the iron nano particles could result in the formation of iron agglomerates within the GNF.)
There are many other parameters which could be controlled and characterized by various characterization methods:
HR-SEM—A HR-SEM (Zeiss Ultra+): It is visible from preliminary images taken to evaluate the material (
TEM—A FEI Titan 80300 electron microscope can be used to view the composition of the nano Graphene tubes, the number of walls the CNT had prior to collapsing, the quality and relative quantity of collapsed tubes to tubes which did not collapse.
The main mechanical characterization method for a single fiber would be the FAVIMAT testing machine. Single fiber testing via instruments such as the FAVIMAT proves of use to this research since limited testing material is available Single fiber testing with the Favimat allows testing of fineness (linear density), strength, and elongation. As single fiber testing is performed the distribution of properties in a sample can be readily obtained. An example for the curve obtained from FAVIMAT is shown in
All parameters will be collected from those tests will be used to successfully model the fiber for computerized simulation as well as to compare with commercially available fibers.
The characterization of the composite material will begin with the process of sample preparation. The fabrication method of the composite samples will strongly depend on the polymeric matrix and its properties. For example the matrix material could well be Epoxy in which case injection or casting methods will be considered. Another option for the matrix material could be elastic thermoplastic polymers or rubbers, in this case pre-impregnation or powder coating and pressing would be the fabrication process used. The samples would than undergo a series of characterization steps in order to characterize the matrix compatibility and performance. For the compatibly electron microscopy (HR-TEM, HR-SEM) and spectroscopy (SAXS, WAXS) will be used to examine the interface between the GNF and the matrix. From this kind of evaluation the adhesion of the matrix to the fiber as well as crystallinity and orientation of the matrix would be evident. In parallel the basic mechanical properties: UTS, elastic modulus, loss and storage modulus, elongation, stiffness and toughness, will be defined. From these characterization methods the compatibility and the synergetic effect of the matrix with the GNF will be decided and the most suitable matrix will be chosen for the rest of the project. For the selected composite material additional tests will be performed. It should be noted that for each proposed characterization method, different sample preparation and even different sample composition is needed.
Predictable properties of GNF composite materials can be effective for future armor applications. It is well known that the mechanical behavior of a composite material is a function of its building material as well as its structure, trough this it can be tailor designed for specific service purposes. Characterization of armor-oriented materials requires dynamic load evaluation in wide range of impact loading rates. facility is equipped with a Hopkinson High Pressure Split Bar (HSPB) apparatus which allows Dynamic compression, tension, bending and shear testing in the range of 102-104 sec−1 strain rates. The output data is usually translated to a stress strain curve at various rates of dynamic loadings. This provides understanding whether the composite material possess a tendency to be affected by the strain rate i.e. it is a strain rate sensitive material. In this case, its strength is linked to the loading conditions, and, if it so, the parameters of constitutive equation will be obtained from these experiments. Correct constitutive equation will be referred by computerized simulative modeling with LS-Dyna tools as explained in section B.4.5 of this proposal. Structure/properties optimization will be carried out by iterations steps in cycles of structure modification versus properties enhancement. Analysis of composite and polymeric containing materials already has a certain level of developed theoretical and experimental base which will used at starting points of presented research proposal.
The technique of planar impact experiment, which can supply data corresponding to dynamic strength at compression dynamic tests, such as Hugoniot Elastic Limit (HEL) at the strain rate range higher than 104 sec−1 and typically up to 107 sec−1.
Characterization of composite materials under dynamic loading will be aimed on understanding of structure-properties relationships and service-aided design of the GNF composite material. Ballistic effectiveness of these materials will be evaluated then directly by means of ballistic evaluation, however optimization of the properties of composite materials will be based on comprehensive material analysis and understanding of its behavior under wide spectrum of loadings.
Those skilled in the art to which this invention pertains will readily appreciate that numerous changes, variations and modifications can be made without departing from the scope of the invention mutatis mutandis.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202372 | Nov 2009 | IL | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/IL2010/000988 | 11/25/2010 | WO | 00 | 7/18/2012 |
| Number | Date | Country | |
|---|---|---|---|
| 61388959 | Oct 2010 | US |
