Ballistic panel and method of making a ballistic panel

A ballistic panel is described including a core layer having a first major surface and a second major surface, the core layer including a ballistic resistant material. A first layer comprising a ballistic gel material is disposed on the first major surface of the core layer. A second layer comprising a ballistic gel material is disposed on the second major surface of the core layer.

FIELD OF THE DISCLOSURE

The present disclosure is directed to a ballistic panel and method of making the ballistic panel.

BACKGROUND

Ballistic panels are often used in applications where bullet proofing is desired. A conventional ballistic panel includes a multi-ply laminate of Kevlar fabric in a non-symmetric panel construction as shown inFIG.1. A single paper honeycomb core10about 1 inch thick is employed in the multi-ply laminate. The paper includes a set of meta-aramid fibers that are pressed together. Across each sheet of the meta-aramid paper a series of horizontal rows of epoxy adhesive are laid down. Then the sheets are stacked on top of each other and cured. The gaps between each bond line are then expanded to create the hexagonal shaped cells. Typically, the cells are hollow (e.g., filled with air). A 28-ply Kevlar laminate20with a cured epoxy resin impregnated therein is adhered to one side of the honeycomb core10with an adhesive layer30. Aluminum face sheets40are adhered to the honeycomb core10and the Kevlar laminate20with additional adhesive layers30. The ballistic panel ofFIG.1is known for use in, for example, aircraft cabin doors to protect the pilots from terrorist threats.

The current panel ofFIG.1, in embodiments, meets ballistic and stiffness requirements. However, because known ballistic panels are not symmetric, they therefore suffer from warping during heat cure. Cold bonding methods can be used for fabricating the ballistic panels ofFIG.1in order to reduce warping. However, such cold bonding methods can increase the time to manufacture the panel and increase scrap rates compared to hot bonding methods of manufacture that are performed at higher temperatures.

Thus, there is a need in the art for materials and processes that can provide a ballistic panel that can be manufactured with reduced warping and less scrap while employing hot bonding methods.

SUMMARY

The present disclosure is directed to a ballistic panel. The ballistic panel comprises a core layer having a first major surface and a second major surface, the core layer comprising a ballistic resistant material. A first layer comprising a ballistic gel material is disposed on the first major surface of the core layer. A second layer comprising a ballistic gel material is disposed on the second major surface of the core layer.

The present disclosure is also directed to a method of making a ballistic panel. The method comprises providing a core layer having a first major surface and a second major surface. The core layer comprises a ballistic resistant material. A first layer comprising a ballistic gel material is attached on the first major surface of the core layer. A second layer comprising a ballistic gel material is attached on the second major surface of the core layer.

It should be noted that some details of the figures have been simplified and are drawn to facilitate understanding rather than to maintain strict structural accuracy, detail, and scale.

DESCRIPTION

Reference will now be made in detail to the present teachings, examples of which are illustrated in the accompanying drawings. In the drawings, like reference numerals have been used throughout to designate identical elements. In the following description, reference is made to the accompanying drawings that form a part thereof, and in which is shown by way of illustration specific examples of practicing the present teachings. The following description is, therefore, merely exemplary.

The ballistic panel, as shown inFIG.1, exhibits warping during manufacture using hot bonding methods due to the differences in the Coefficient of Thermal Expansion (CTE) of the panel components. This can result in lost time and expense to repair the warped panel, or potentially may result in scrapping the panel altogether. Further, the warping of the panel often results in some form of dis-bonding of the panel components. Once dis-bonding occurs the panel loses much of the key mechanical properties for which it was designed, such as, for example, a significant reduction in flexural strength. Warping of composite panels can occur due to a non-symmetric stacking of panel components that are heated and subsequently cooled. In this case, the non-symmetry is due, in part, to the large multi-ply KEVLAR ballistic laminate20, which is used to meet ballistic specifications of the panel and, which is only stacked on one side of the honeycomb core. Unfortunately redistributing the plies of Kevlar fabric into two smaller, separate laminates that are symmetrically distributed about the honeycomb core10will not meet ballistic specifications without further modifications. Furthermore, symmetrically adding another laminate (e.g., a replicate of ballistic laminate20) to the construction may reduce warping but would greatly increase weight, which increases fuel consumption of airplanes in which the panel is employed. This in turn adds significant cost to airline customers.

The symmetric designs of the ballistic panels of the present disclosure reduce warping to within acceptable levels while still allowing fabrication by the hot bonding method. Hot bonding employs relatively high temperatures, such as, for example, above 200° F., such as from about 220° F. to about 500° F., which can increase production rates. In an example, the hot bonding can occur at temperatures of from about 275° F. to about 300° F. for 25-30 minutes at 80 PSI. Ballistic gel layers comprising, for example, cells filled with ballistic gel, or other ballistic gel layer materials as described herein, are adhered to a multi-ply laminate of ballistic resistant material to provide for a single, cohesive laminate structure that achieves desired ballistic protection. In an embodiment, the ballistic gel layer comprising cells filled with ballistic gel has a lower density than, for example, a Kevlar laminate, thereby providing a relatively lightweight ballistic material.

FIG.2illustrates an example of a ballistic panel100, according to the present disclosure. The ballistic panel comprises a core layer102having a first major surface104and a second major surface106. The core layer comprises a ballistic resistant material, such as, for example, KEVLAR®. The ballistic resistant material that may be employed for the core layer102will be described in greater detail below. A first layer comprising ballistic gel material120is disposed on the first major surface104of the core layer102. A second layer comprising ballistic gel material122is disposed on the second major surface106of the core layer102. The ballistic gel acts as a light weight ballistic material that is different from the ballistic resistant material, and, when bonded to the ballistic resistant material, forms a composite that provides the desired anti-ballistic properties while still allowing for a symmetrical ballistic panel design.

The ballistic resistant material that may be used for core layer102will now be described in more detail. An example of a suitable material is para-aramid fibers, such as KEVLAR (poly paraphenylene terephthalamide) fibers, woven into a fabric and impregnated with a curable resin. In the KEVLAR fibers, the aromatic groups are all linked to the backbone chain at the 1 and 4 positions, as shown in Formula 2, below, where “n” is the number of repeat units. This is called a para-linkage.

Multiple layers, or plies, of the resin impregnated KEVLAR fiber fabric can be laminated together with the resin and cured. For example, about from 5 to about 20 plies, such as from about 10 to about 20 plies, or from about 10 to about 15 plies of resin impregnated fabric can be included in the core layer102. The resin can be any curable resin that is suitable for such pre-impregnated laminates, such as an epoxy resin. The resin can be a low heat release resin, including thermosetting resins such as phenolic resin, benzoxazine resins, and cyanate ester based resins. Thermoplastic resins such as Polyether ether ketone (PEEK), Polyetherketoneketone (PEKK), Polyphenylsulfone (PPSU), Polyphenylene sulfide (PPS), and Polyetherimide (PEI) resins can also be used.

The thickness of the core layer102can be chosen to provide a desired degree of protection against penetration of the ballistic panel100by bullets or other projectiles. As examples, the core layer102can have a thickness ranging from about 0.1 inch to about 0.5 inch, such as from about 0.2 inch to about 0.4 inch.

Both the first layer comprising ballistic gel material120and the second layer comprising ballistic gel material122can comprise a cell wall108structured to provide a plurality of cells110. A ballistic gel112is embedded within the plurality of cells110to form cellular gel-filled layers.

FIG.3illustrates a perspective view of a cell wall108before the ballistic gel112has been introduced into the cells110. Cells110can have any suitable shape, such as a honeycomb shape having a hexagonal cross-section, as illustrated inFIG.3. Other examples include cells with square, rectangular or other polygonal cross-sections. The cell wall108can comprises any material suitable for containing the ballistic gel112in a ballistic resistant structure. An example of a suitable material is paper comprising a set of meta-aramid fibers that are pressed together. The cell wall material108can be fabricated by applying an epoxy adhesive across a plurality of sheets of the meta-aramid paper in a series of horizontal rows. The sheets are stacked on top of each other and the adhesive is cured. The gaps between each bond line are then expanded to create the hexagonal shaped cells. An example of a commercially available fabric comprising meta-aramid fibers that is suitable for making the cell wall108is NOMEX®, which is available from DuPont, of Midland, Mich. In NOMEX, the aromatic groups are all linked to the backbone chain at the 1 and 3 positions, as shown in Formula 1, below, where “n” is the number of repeat units. This is called meta-linkage.

The ballistic gel112can be any dilatant, non-newtonian fluid that has the property of exhibiting an increase in rigidity when impacted by a bullet. An example of such a ballistic gel is D3O™ gel, commercially available from D3O Labs of London, United Kingdom. D3O is an energy-absorbing gel material comprising polyurethane and polyborodimethylsiloxane. The D3O can be in the form of a foam, such as closed cell polyurethane foam composite comprising polyborodimethylsiloxane (PBDMS) as the dilatant dispersed through the foam matrix.

The cell walls108provide little or no ballistic resistance without the D3O gel, but do impart stiffness to the composite panel. The first layer comprising ballistic gel material120and the second layer comprising ballistic gel layer122can each have any thickness that provides the desired ballistic resistance and/or stiffness to the ballistic panel. As an example, the thickness can range from about 0.2 inch to about 3 inches, such as from about 0.2 inch to about 2 inches, or from about 0.5 inch to about 1 inch.

The ballistic panel ofFIG.2further comprises a first face sheet130on the first layer of ballistic gel material120and a second face sheet132on the second layer of ballistic gel material122. As an example, the first face sheet130and the second face sheet132each comprise aluminum, such as pure aluminum (e.g., 99% by weight of Al or more) or aluminum alloys. The face sheet provides flexure stiffness along with the core. Additionally, face sheets comprising aluminum have properties that may aid in stopping bullets or shrapnel.

The first face sheet130and the second face sheet132can have any desired thickness. Examples of suitable thickness range from about 0.005 inch to about 0.04 inch, such as from about 0.01 inch to about 0.03 inch.

One or more of the layers that make up the ballistic panel100can be attached together using adhesive layers. For example, a first adhesive layer150can adhere the first layer of ballistic gel material120to the core layer102and a second adhesive layer150can adhere the second layer of ballistic gel material122to the core layer102. Other adhesive layers150can be used to adhere the face sheets130,132to the ballistic panel100. Any suitable adhesive material that provides sufficient bonding between the layers can be employed. Examples include urethane adhesives and epoxy adhesives.

FIG.4illustrates a ballistic panel100that is similar to that ofFIG.2, except that the ballistic panel ofFIG.4includes a first underlying layer136disposed between the first layer comprising ballistic gel material120and the first face sheet130and a second underlying layer138disposed between the second layer comprising ballistic gel material122and the second face sheet132. In an example, the first underlying layer136and the second underlying layer138both comprise a fiberglass fabric impregnated with a resin. Any suitable curable resin can be employed that is suitable for fiberglass. For example, the resin can be a phenolic resin.

Other implementations of the ballistic panels of the present disclosure are contemplated. As examples, instead of the cellular gel-filled layers discussed above for the layers120and122ofFIGS.2and4, other types of layers can be used, such as a ballistic gel without the cell walls108structured to provide the plurality of cells110. For example, the layers120and122ofFIGS.2and4can be a layer of ballistic gel foam alone. Examples of suitable ballistic gel foam materials are known in the art, such as the D3O material described herein. In yet another implementation, the layers120and122of the ballistic panel ofFIGS.2and4can each be a laminate structure comprising multiple plies of ballistic resistant material and one or more layers of ballistic gel. An example of such a laminate structure is shown inFIG.5, which includes sheets of a ballistic resistant material170and one or more layers of ballistic gel172positioned between the sheets of ballistic resistant material170and bonded thereto by any suitable means, such as by using an adhesive (not shown). The ballistic resistant material can be, for example, para-aramid fibers, such as KEVLAR (poly paraphenylene terephthalamide) fibers, woven into a fabric. In the layers120and122as shown inFIG.5, the para-aramid fiber fabric may or may not be impregnated with a curable resin. The ballistic gel can be a ballistic gel foam, such as, for example, layers of the D3O material described herein. The laminate structure ofFIG.5can be included as each of the layers120and122in the ballistic panel100ofFIGS.2and4.

FIG.6illustrates another implementation of a ballistic panel according to the present disclosure. The ballistic panel100ofFIG.6also includes a core layer of ballistic resistant material102; face sheets130,132and adhesive layers150for bonding the layers together. The layers of ballistic resistant material102; face sheets130,132and adhesive layers150can be the same as those described above with respect toFIG.2. In addition, the ballistic panel100includes ballistic gel layers120,122without cell walls108or cells110. For example, the ballistic gel layers120and122can be the ballistic gel foam alone, as described herein. Cellular layers180and182are separate from the ballistic gel layers120,122. The cellular layers180,182comprise cell walls108that form cells110, and which can be the same as described above with respect toFIG.3, except that the cells110are filled with a gas, such as air, instead of a ballistic gel. For example, the cellular layers180and182can comprise hexagonal cells (e.g., honeycomb) or other cell shapes comprising meta-aramid fibers. The cellular layers180,182are bonded to adjacent layers using a suitable adhesive150. The implementation ofFIG.6can optionally include an underlying layer (not shown) between the first face sheet130and the cellular layer180and an underlying layer (not shown) between the second face sheet132on the cellular layer182, where the underlayers can be the same as underlayers136,138described herein with respect toFIG.4.

Various other layers can also optionally be employed in any of the ballistic panels described herein. For example, the ballistic panels ofFIGS.2,4and6can includes a first fire retardant layer (not shown) disposed between the ballistic gel containing layers120,122and the outer layers of the ballistic panels. As an example, referring toFIG.2, a first fire retardant layer can be disposed between the first layer of ballistic gel material120and the first face sheet130and a second fire retardant layer can be disposed between the second layer of ballistic resistant material122and the second face sheet132. The fire retardant layers can also be disposed between layers120and136and layers122and138, or between layers136and130and layers138and132of the ballistic panel ofFIG.4. In yet another implementation, the fire retardant layers can be disposed between layers120and180and layers122and182, or between layers180and130and layers182and132of the ballistic panel ofFIG.6

The fire retardant layers can comprise one or more layers, such as about 1 to about 10 layers, or about 1 to about 5 layers, or about 1 to about 3 layers, of fabric impregnated with a fire retardant. The fabric can be a ballistic resistant material, such as woven para-aramid fibers (e.g., KEVLAR® or other fabric). Any suitable fire retardant material can be employed, such as any of the intumescent materials described in the present disclosure. Examples of a commercially available intumescent material is VERSACHAR® resin, which is a thermoplastic intumescent layer available from FlameOFF Coatings, Inc., of Raleigh, N.C. In an alternative example, the fire retardant layers can comprise the intumescent material impregnated into a fiberglass fabric. In yet another example, the fire retardant layers can comprise the intumescent material without a fabric or fibers (e.g., a layer of the intumescent material alone).

Other optional layers that can be employed include intumescent layers and/or decorative layers, which can be disposed on one or both of the face sheets130,132of any of the ballistic panels described herein. The intumescent layer functions to provide fire resistance to the ballistic panels. The intumescent layer comprises intumescent materials that can be, for example, organic material formulations that create a foam in the presence of heat. Example temperatures at which the intumescent materials activate to form a foam are about 250° F. to about 450° F. The foam acts as a thermal barrier against heat penetration in the event of a fire. The D3O gel will most likely not have the same flammability properties as the aramid core into which the gel is incorporated, and the intumescent materials can aid in providing a desired level of fire resistance to the panel. Examples of a commercially available intumescent material is VERSACHAR® resin, which is a thermoplastic intumescent layer available from, for example, FlameOFF Coatings, Inc. of Raleigh, N.C. or Ed Gregor and associates of South Carolina. In another embodiment, a fabric can be pre-impregnated with an intumescent polymer, such as VERSACHAR®. This would incorporate nicely into a composite stack up where one or more plies of the pre-impregnated fabric (prepreg) can be disposed on the outside surface of the ballistic laminate. The intumescent layer can have any suitable thickness. As an example, the intumescent layer has a thickness ranging from about 0.001 inch to about 0.1 inch, such as about 0.002 inch to about 0.01 inch. The decorative layers can include, for example, wall paper, paint, logos or any other desired layer applied to enhance visual appearance of the panel. Such decorative layers can optionally be applied to any of the ballistic panels described herein.

The ballistic panels of the present disclosure can be employed in any desired application for which ballistic protection is desired. Examples of such applications include bullet proofing of aircraft, aerospace and other vehicles or structures used for military purposes. Other examples include ballistic resistant door panels employed between the passenger compartment and cabins of commercial aircraft as an anti-terrorism measure, and other applications in which relatively light weight ballistic protection is desired.

An example of a ballistic resistant door200of an aircraft202is shown inFIG.7. Aircraft202includes an exterior skin205defining a fuselage. The inside of the aircraft202includes a flight deck wall206including the ballistic resistant door200, which can be, for example, a flight deck door. The flight deck wall206and ballistic resistant door200separate the flight deck area or side212from the passenger area or side214. The ballistic resistant door200allows restricted access to the flight deck side212from the passenger side214. The ballistic resistant door200may also be used as a door at other locations within the fuselage if desired. Generally, the ballistic resistant door200is formed to fit into a door jam in the flight deck wall206. For example, one side of the ballistic resistant door200can include a hinge207which mates with a hinge208of the door jam. This allows the ballistic resistant door200to be easily opened and closed. Also, the ballistic resistant door200includes a door latch or locking mechanism209. The locking mechanism209mates with a jam locking mechanism (not shown) on the door jam to lock the ballistic resistant door200in a closed position.

Referring toFIG.8, the present disclosure is also directed to a method of making a ballistic panel. The method comprises providing a core layer having a first major surface and a second major surface, the core layer comprising a ballistic resistant material. A first layer comprising a ballistic gel material is attached on the first major surface of the core layer. A second layer comprising a ballistic gel material is attached on the second major surface of the core layer.

The first layer comprising ballistic gel material and the second layer comprising ballistic gel material, as described for any of the ballistic panels above, can each be a cellular core layer manufactured by incorporating a ballistic gel into a plurality of cells formed by cell wall, as shown inFIG.3. For example, the ballistic gel under slowly applied pressure acts as a liquid and can be embedded into the honeycomb core cells. The pressure for embedding the ballistic gel may be applied by gravity or other suitable techniques.

The methods described herein can optionally include attaching additional layers to the ballistic panels. For example, the methods can optionally include attaching underlying layer136and/or the first face sheet130on the first layer comprising ballistic gel material and an underlying layer138and/or a second face sheet132on the second layer comprising ballistic gel material.

Any other suitable layers described herein can also optionally be applied as part of the methods of the present disclosure. As an example, the method can optionally further include attaching one or more layers of para-aramid fibers woven into a fabric and impregnated with a fire retardant. As yet another example, the method can optionally further include applying an intumescent layer that can act as a fire retardant on the first face sheet and/or the second face sheet. As another example, the method can optionally comprise attaching a first cellular layer to the first layer of ballistic resistant material prior to attaching the first face sheet and attaching a second cellular layer to the second layer of ballistic resistant material prior to attaching the second face sheet, the first cellular layer and the second cellular layer both comprising cell walls that form a plurality of cells, the plurality of cells being filled with a gas. The first face sheet can be attached to the first cellular layer and the second face sheet can be attached to the second cellular layer, similarly as illustrated inFIG.6. Any of the layers of face sheets, layers of para-aramid fibers woven into a fabric and impregnated with a fire retardant, intumescent layers, decorative layers or cellular layers described herein can be employed in the methods of the present disclosure.

The optional intumescent layers and/or decorative layers can be applied to the face sheets130,132by any suitable layer techniques. Suitable layer techniques are well known in the art and could be selected by one of ordinary skill in the art. A primer (not shown) can optionally be applied to the face sheet(s) prior to applying the intumescent layer. The primer aids in providing satisfactory adhesion between the intumescent layer and the face sheets.

One or more, such as all, of the layers of the ballistic panels can be adhered together using adhesive layers, as described above. For example, the method can include adhering the first layer comprising ballistic gel material120to the core layer102and adhering the second layer comprising ballistic gel material122to the core layer102using adhesive layers150. Other adhesive layers150can be used to adhere the face sheets130,132to the ballistic panel. The adhering process can be performed by a hot bonding method, which employs heating to cure the adhesion layers150, such as at any of the hot bonding temperatures described herein. While hot bonding methods are preferred because they save process time compared to cold process techniques, cold bonding methods can also be employed if desired. Both hot bonding and cold bonding techniques are generally well known in the art.

While the present teachings have been illustrated with respect to one or more implementations, alterations and/or modifications can be made to the illustrated examples without departing from the spirit and scope of the appended claims. In addition, while a particular feature of the present teachings may have been disclosed with respect to only one of several implementations, such feature may be combined with one or more other features of the other implementations as may be desired and advantageous for any given or particular function.

Furthermore, to the extent that the terms “including,” “includes,” “having,” “has,” “with,” or variants thereof are used in either the detailed description and the claims, such terms are intended to be inclusive in a manner similar to the term “comprising.” Further, in the discussion and claims herein, the term “about” indicates that the value listed may be somewhat altered, as long as the alteration does not result in nonconformance of the process or structure to the intended purpose described herein. Finally, “exemplary” indicates the description is used as an example, rather than implying that it is an ideal.