1. Field of the Invention
The present invention pertains to the art of protective panels and, more specifically, to lightweight blast mitigating composite panels.
2. Discussion of the Prior Art
Blast mitigation can be achieved by numerous methods including the use of structural elements such as composite armor. In general, composite armor comprises a system of materials in which ultra high molecular weight polyethylene (UHMWPE) fibers are arranged within a matrix to form a core that is subsequently encased in some form of outer shell such as ceramic or fiberglass. The core and shell may be further surrounded by a protective sleeve or case. A limiting factor of such armors is the ability of the UHMWPE fibers to delocalize or disperse a blast load over the matrix.
One area where blast mitigation is increasingly utilized is in transportation applications. It is an unfortunate fact that terrorist threats to public transportation have increased in recent times. Bombs of various sorts have been utilized by terrorists in a variety of situations and pose a particular threat to in-flight aircraft. Despite an increase in security procedures and the use of explosives detecting equipment, bombs have still occasionally found their way aboard aircraft. Bombs may be smuggled into an aircraft in carry-on luggage or other parcels that are stored and carried in the overhead storage bins of the aircraft. Because of regulatory requirements, as well as practical considerations, overhead storage bins have certain size and weight limitations.
Based on the above, there exists a need for a lightweight blast mitigating composite panel which is adapted to protect against damage from an explosion and constructed from materials which are cost-effective. In particular, there is seen to exist a need for a lightweight panel which can be utilized in overhead storage bins to protect against damage from an explosion from within the bin.
The present invention is directed to a lightweight blast mitigating composite panel. More specifically, a composite panel includes multiple layers incorporating ultra high molecular weight polyethylene (UHMWPE) fibers as a primary strength component, a honeycomb layer, flame resistant thermoset adhesive layers applied on either side of the UHMWPE layer, and a fiber reinforcing layer applied on either side of the flame resistant thermoset layers. These composite layers form a core which is then encased in an outer fiberglass shell. The flame resistant thermoset adhesive layers provide for increased adhesion between the UHMWPE core and the high strength reinforcing fibers. The overall combined layering results in a panel having increased dynamic stiffness and the ability to disperse/distribute localized blast loads. The panels have numerous applications, including in the manufacturing of blast mitigating storage bins for aircraft. More specifically, a blast mitigating storage bin of the present invention includes integrated unarmored and armored portions covered by continuous upper and lower shells. The storage bin is lightweight and can replace a standard overhead storage bin in the cabin of an aircraft with no outward change in appearance or function, while the overall combined layering results in a panel having increased dynamic stiffness and the ability to disperse/distribute localized blast loads.
Additional objects, features and advantages of the present invention will become more readily apparent from the following detailed description of preferred embodiments when taken in conjunction with the drawings wherein like reference numerals refer to corresponding parts in the several views.
With initial reference to
Turning to
More specifically, as depicted in
In accordance with the first embodiment, the lightweight armored panel of the present invention has the following characteristics: first outer shell 14 includes first and second reinforcing layers 50 and 52, each comprised of an E-glass/phenolic facing having a thickness of approximately 0.016 inches. Second outer shell 15 includes first and second fiber reinforcing layers 68 and 69 in the form of uni-directional carbon fiber/phenolic facings having a thickness of approximately 0.02 inches each. Likewise, first, interior reinforcing layer 60 includes first and second reinforcing layers 61 and 62 in the form of uni-directional carbon fiber/phenolic facings having a thickness of approximately 0.02 inches each. Flame resistant adhesive layer 54 extends between honeycomb layer 56 and first outer shell 14, and flame resistant adhesive layer 58 extends between honeycomb layer 56 and reinforcing layer 60. UHMWPE layer 64 includes thermoset flame resistant upper and lower plastic coatings 70 and 71, wherein layer 64 has an overall thickness in the order of 0.2 inches, most preferably approximately 0.214 inches. Additional flame resistant adhesive layers 63 and 66 having a thickness of approximately 0.005 inches adhere UHMWPE layer 64 to respective second outer shell 15 and first reinforcing layer 60. This first configuration results in a lightweight composite panel having an overall thickness in the order to 0.6-0.7 inches, preferably approximately 0.671 inches. Details of this first embodiment, which exhibits an advantageous strength to weight ratio, are summarized in Table 1 below.
One application of the lightweight blast mitigating panel 10 of the present invention is in the production of blast mitigating storage devices. With reference to
With particular reference to
In a preferred embodiment, UHMWPE fiber layer 164 is comprised of long chain polyethylene having molecular weights ranging from 3 to 6 million. However, in general, molecular weights above 500 thousand would be considered ultra high and functional in accordance with the invention. Still, a preferred molecular weight range is greater than 1 million and, most preferred is the 3-6 million weight range. In accordance with the present invention, UHMWPE layer 164 is coated on upper and lower sides with a fire resistant thermoset plastic coating indicated at 170 and 171 in the form of a thin flame resistant paste. Honeycomb layer 156 is preferably Nomex®.
Preferably, lightweight panel portions 128-132 utilized in blast mitigating overhead storage bin 100 include the following characteristics: first shell 152 comprises a single layer of E-glass/phenolic facing having a thickness of approximately 0.014 inches; flame resistant adhesive layers 154, 158, 163 and 166 comprise phenolic adhesive layers having a thickness of approximately 0.005 inches; and first fiber reinforcing layer 160 and second shell 168 comprise S-glass phenolic prepregs having a thickness of approximately 0.019 inches. In this embodiment, Nomex® honeycomb layer 156 has a thickness of approximately 0.365 inches and Dyneema® UHMWPE layer 164 has a thickness of approximately 0.156 inches, with each flame resistant thermoset coating 170 and 171 having a thickness of approximately 0.010 inches. This first configuration results in thin, armored sections 128-132, having an overall thickness of approximately 0.613 inches and an overall weight of approximately 1.59 lbs/ft2. Details of this second, strong composite embodiment of the lightweight blast mitigating composite panels of the present invention are summarized in Table 2 below.
Referring back to
In accordance with the invention, it has been surprisingly found that the inclusion of the flame resistant thermoset plastic layers such as 70, 71 and 170, 171, dramatically enhances the blast absorption, suppression and mitigation capabilities of typical UHMWPE type shields by up to 4 times verses corresponding structure without the flame resistant thermoset plastic layers. Although the fire resistant layers' usual purpose is fire resistance, it is speculated that the fire resistant layers stiffen the Dyneema® layer enough to allow the stress created by a blast to disperse over a larger area. This may be due to the flame resistant thermoset plastic layers significantly enhancing the adherence of the composite layers to the UHMWPE layer core, be it Dyneema®, Spectra® or the like. In effect, this configuration increases the stiffness of the core material, which manifests itself into increased distribution of the localized loads resulting in significant improvements in blast performance. This system provides the core material with the required stiffness to absorb blast and ballistic threats. More specifically, composite panels including a coated UHMWPE core were found to perform well under both series 1 and series 2 tests under Section 2.1.2 (Fragmentation/Shock holing) of ISO 6517, Draft Appendix A, while standard panels known in the industry were found to perform at most under series 1 test requirements, as evidenced by the experimental results described below.
A total of eight sample panels were tested based on requirements set forth in the overhead bin specification Section 2.1.2 (Fragmentation/Shock holing) of ISO 6517, Draft Appendix A. The panels were tested under series 1 and series 2. The tests were conducted at Aberdeen Proving Grounds.
Test #1—Panel Composition No. 1, Series 1
A first 4′×4′ panel had an identical composition and thickness to a standard hardened cockpit door supplied by C&D Aerospace, Inc. Specifically, the panel was composed of a 2-ply phenolic/E-glass facesheet, a film epoxy adhesive, a ⅜″ Nomex® honeycomb panel treated with phenolic resin, a film epoxy adhesive, a UHMWPE—Dyneema® panel ( 3/16″), a film epoxy adhesive, and a 2-ply phenolic/E-glass facesheet. The panel was 1″ thick and had an areal weight of 1.5 lb/sqft. The resin content was between 30-40% within the E-glass facing.
Test Procedure: The panel was mounted to a test fixture with 3 soft-sided suitcases, the charge suitcase was in the center. The contents, weight and composition of the charge bag and adjacent bags were documented to maintain consistency from test to test. Charge size and placement were in accordance with the requirements of overhead bin specification Section 2.1.2 of ISO 6517, Draft Appendix A, series 1. Instrumentation of the test was limited to still photograph documentation.
Test Results: Criteria for determining if a panel was deemed to have passed the test was a visual inspection of the panel post-test for signs of rupture at panel center due to impulsive loading. Panel pull-through at edges of bolted connections was not a criteria for shock hole failure. The panel did not perforate. On the outside panel, there was a tear in the 2 E-glass plies that measured 39″ horizontally and 40″ diagonally downwards. There were multiple tears between 15″ and 41″ to the E-glass (2 plies) and a 16″×18″ hole in the honeycomb. On the inside panel, there was a 42″ horizontal tear to the E-glass and a 10½″×18½″ hole in the honeycomb. There was no hole in the Dyneema®. There was fragment damage to the inside face measuring 3″×3¼″ and 2½×1½″. There was minor charring to the panel and the dome deformation measured 4⅜″. There was delamination near the center of the panel. The E-glass and honeycomb delaminated from the Dyneema®.
This panel passed under the requirements of overhead bin specification Section 2.1.2 (Fragmentation/Shockholing) of ISO 6517, Draft Appendix A, series 1.
Test #2—Panel Composition No. 1, Series 1
The panel submitted for test #2 was identical in construction and composition to the panel submitted in test #1.
Test Procedure: The panel was mounted in the test fixture and the bags were prepared and oriented identically to the manner used in test #1. The explosive charge weight, composition, initiation procedure and charge standoff were identical to the procedures noted in test #1.
Test Results: The panel did not perforate. On the outside panel, there was a tear that measured 30″ horizontally and 37″ vertically to the E-glass (2 plies). There were tears between 20″ and 42″ to the 2 plies of the E-glass and an 18″ (horizontal)×11″ (vertical) tear to the Nomex®. On the inside panel there was 30″ (horizontal) and 37″ (vertical) tears to the E-glass—2 plies and an 11″ (horizontal)×8″ (vertical) tear to the Nomex®. There was no hole in the Dyneema®. There was fragment damage to the inside face with a 1″ hole and minor charring to the panel. The panel did not separate from the fixture. The dome deformation measured 2″. There was delamination to the E-glass and honeycomb near the center of the panel.
This panel passed under the requirements to overhead bin specification Section 2.1.2 (Fragmentation/Shockholing) of ISO 6517, Draft Appendix A, series 1. By passing 2 successive series 1 tests, this panel design completely met series 1 shock hole requirements.
Test #3—Panel Composition No. 1, Series 2
The panel submitted for test #3 was identical in construction and composition to the panels submitted in tests #1 and #2.
Test Procedure: The panel was mounted in the test fixture and the bags were prepared and oriented identically to the manner used in tests #1 and #2.
Test Results: The panel perforated. On the outside panel, there were tears that measured between 44″ and 16″ to the E-glass (2 plies) and there was a 12″×11″ hole in the honeycomb. On the inside panel there was a 17″×20″ tear to the E-glass (2 plies) and a 12″×11″ hole in the honeycomb. There was a hole in the Dyneema® that measured 6″×6″. The panel did not separate from the fixture. There was also delamination near the central region. The panel did not burn and there was no fragment damage.
This panel failed under the requirements to overhead bin specification Section 2.1.2 (Fragmentation/Shockholing) of ISO 6517, Draft Appendix A, series 2.
Test #4—Panel Composition No. 2, Series 2
The panel submitted for test #4 was nearly identical in construction and composition to the panels submitted in tests 1-3, the only difference was the inclusion of a fire retardant (FR) layer placed on both sides and directly in contact with the Dyneema® layer. The FR layers were comprised of a thermosetting glue made by Composix in Newark, Ohio, having a thickness of approximately 0.060″.
Test Procedure: The panel was mounted in the test fixture and the bags were prepared and oriented identically to the manner used in Tests 1-3.
Test Results: The panel did not perforate. On the outside panel, there was a tear in the 2-ply E-glass that measured 37″ (horizontally) and 32″ (vertically) and there was a 23″×15″ hole in the honeycomb. On the inside panel there was a 9″×7″ hole in the 2-ply E-glass and a 9″×12″ hole in the Nomex®. There was delamination in the central region to the Dyneema®. The panel did not burn and there was no fragment damage. The dome deformation measured 1⅜″.
This panel passed under the requirements to overhead bin specification Section 2.1.2 (Fragmentation/Shockholing) of ISO 6517, Draft Appendix A, series 2.
Test #5—Panel Composition No. 1, Series 2
The panel submitted for test #5 was identical in construction and composition to the panels submitted in tests 1-3.
Test Procedure: The panel was mounted in the test fixture and the bags were prepared and oriented identically to the manner used in tests 1-4.
Test Results: The panel perforated. On the outside panel, there were tears in the 2-ply E-glass that measured between 18″ and 40″ and a 9″×11″ hole in the Nomex®. On the inside panel there was an 8″×10″ hole in the 2-ply E-glass and an 8″×11″ hole in the Nomex®. There was a 3″×2″ hole in the Dyneema®. There was delamination in the central region to the E-glass and Nomex® from the Dyneema®. The dome deformation measured 4½″. The panel did not burn and there was no fragment damage.
This panel failed under the requirements to overhead bin specification Section 2.1.2 (Fragmentation/Shockholing) of ISO 6517, Draft Appendix A, series 2.
Test #6—Panel Composition No. 3, Series 2
A 4′×4′ panel sample was submitted having 6 plies composed of S2-glass/phenolic laminate, 0/90 layup. The panel was ⅛″ thick and had an areal weight of 1.30 lb/sqft. The resin content was about 32%-35%.
Test Procedure: The panel was mounted to the test fixture with 3 soft-sided suitcases, the charge suitcase was in the center. The contents, weight and composition of the charge bag and adjacent bags were documented to maintain consistency from test to test. Charge size and placement were in accordance with the requirements to overhead bin specification Section 2.12 (Fragmentation/Shockholing) of ISO 6517, Draft Appendix A, series 1 and series 2. Instrumentation of the test was limited to still photograph documentation.
Test Results: Criteria for determining if a panel was deemed to have passed the test was a visual inspection of the panel post-test for signs of rupture at panel center due to impulsive loading. Panel pull-through at edges of bolted connections was not a criteria for shock hole failure. The panel perforated. On the outside and inside of the panel, there was delamination throughout most of the panel. There was a hole that measured 6″ and all 6 plies were penetrated. There was no fragment damage and minor charring to the panel.
This panel failed under the requirements to overhead bin specification Section 2.1.2 (Fragmentation/Shockholing) of ISO 6517, Draft Appendix A, series 2.
Test #7—Panel Composition No. 3, Series 2
The panel submitted for test #6 was identical in construction and composition to the panel submitted in test #5.
Test Procedure: The panel was mounted in the test fixture and the bags were prepared and oriented identically to the manner used in test #5. The explosive charge weight, composition, initiation procedure and charge standoff were identical to the procedures noted in test #5.
Test Results: The panel perforated. There was delamination of 6 plies in and around the central hole and multiple tears extending inward from the bolt holes approximately 15″ long. There was a hole that measured 5″. There was one small fragment damage portion with partial penetration. There was also minor charring to the panel.
This panel failed under the requirements to overhead bin specification Section 2.1.2 (Fragmentation/Shockholing) of ISO 6517, Draft Appendix A, series 2.
Test #8—Panel Composition No. 3, Series 1
The panel submitted for test #7 was identical in construction and composition to the panels submitted in test #'s 5 and 6.
Test Procedure: The panel was mounted in the test fixture and the bags were prepared and oriented identically to the manner used in test #5 and #6.
Test Results: The panel perforated. There was delamination throughout the panel. There were multiple tears to the inside face extending inward form the bolt holes approximately 10″. There was a hole that measured 9″ vertically and 6″ horizontally. There was no fragment damage and minor charring to the panel.
This panel failed under the requirements to overhead bin specification Section 2.1.2 (Fragmentation/Shockholing) of ISO 6517, Draft Appendix A, series 1.
Although described with reference to preferred embodiments of the invention, it should be readily understood that various changes and/or modifications can be made to the invention without departing from the spirit thereof. For instance, although main body portion 133 of overhead bin 100 is shown including five armored panel portions 128-132, it should be understood that various configurations utilizing different numbers of armored panels may be utilized without departing from the present invention. Additionally, although the disclosed embodiments refer to panels having a final thickness of approximately 0.613 and 0.671 inches, it should be understood that the general and specific thicknesses of each layer can be tailored to a desired application and the threat present in that particular application. Furthermore, although honeycomb layers 56, 156 are shown, honeycomb layers 56, 156 may not be necessary for every application of the armored panels of the present invention. Although S-glass and E-glass have been discussed above for use in the armored panel, other fiberglass products could be employed. Particularly preferred is S-2 Glass® made by AGY Holding Corporation.
Advantageously, the present invention provides a lightweight panel without the need for any metal, ceramic or other hard and difficult to process materials. The panel of the present invention can be shaped to limited curvatures and formed into components and panels to conform to existing configurations or replace existing structural panels. It should be readily understood that the armored panels of the present invention, in addition to having applications in baggage compartments and containers, can have applications including: military body or vehicle armor; homeland security, anti-terrorism and personal security fields; automotive, shipping and aerospace vehicles; and storm management. More specifically, the present invention may have use in load bearing structures, lightweight walls, explosive blow-out containment or mitigation walls or barriers in building construction, cargo applications, monuments, flooring, doors, and auxiliary panels, for example. In any case, the invention is only intended to be limited to the scope of the following claims.
This application represents a National Stage application of PCT/US2009/042677 entitled “Lightweight Blast Mitigating Composite Panel” filed May 4, 2009, pending, which claims priority of U.S. Provisional Patent Application Ser. No. 61/071,516, filed May 2, 2008, entitled “Aircraft Overhead Storage Bin” and U.S. Provisional Patent Application Ser. No. 61/071,517, filed May 2, 2008 entitled “Lightweight Blast Mitigating Composite Panel”.
The present invention was developed under TSA/TSL Contract No. DTFACT-03-C-00042. Therefore, the U.S. Government has certain rights to the invention.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/US2009/042677 | 5/4/2009 | WO | 00 | 10/27/2010 |
Publishing Document | Publishing Date | Country | Kind |
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WO2010/033266 | 3/25/2010 | WO | A |
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