METHOD FOR MANUFACTURE OF CELLULAR STRUCTURE AND RESULTING CELLULAR STRUCTURE

RELATED APPLICATIONS

This application claims priority from U.S. Provisional Application Serial. No. 61/030,051 filed on February 20, 2008 entitled "Sandwich Panel Structures with Tailored Cores and Related Method of Manufacture," the entire disclosure of which is hereby incorporated by reference herein. This application is related to U.S. Application Serial No. 10/515,572, filed

November 23, 2004, which is a national stage filing of International Application No. PCT/US03/ 16844, filed on May 29, 2003, which claims benefit under 35 U.S.C Section 119(e) from U.S. Provisional Application Serial. No. 60/384,341 filed on May 30, 2002, entitled "Method for Manufacture of Periodic Cellular Structure and Related Structure thereof," and Application Serial. No. 60/422,550 filed on October 31, 2002, entitled "Method for Manufacture of Periodic Cellular Structure and Related Structure thereof," all of the disclosures of which are hereby incorporated by reference herein in their entirety.

US GOVERNMENT RIGHTS

This invention was made with United States Government support under Grant No. N00014-07-1-07694, awarded by the Defense Advanced Research Projects Agency/Office of Naval Research. The United States Government has certain rights in the invention.

SUMMARY OF THE INVENTION

Sandwich panel structures with light cellular cores shall be used for the efficient support of stresses which subject the panel to bending or buckling deformations. Similar panels with high strength and/or large densifϊcation strains shall also be also used for impact and blast mitigation. Panels in which the cell spaces within the core are made from ballistic resistant materials also offer promise for

impeding the penetration of projectiles. They could be used to contain the fragments created by disintegration of an engine, or those created by an explosion.

An aspect of an embodiments of the present invention comprises, but not limited thereto, the following: cellular structures that provide metallic, ceramic and polymeric materials in easily adjusted topologies ranging from prismatic to prismatic plus honeycomb to purely honeycomb with relative densities from less than about 0.01 to more than about 90%. An aspect of various embodiments of the present invention comprises, but not limited thereto, the following: structures in which the internal cell volumes are filled, fully or partially with other materials including cellular structures. Several simple methods for the fabrication of such structures are also proposed and demonstrated.

Some of the disclosed herein typify the cellular panel structure prototypes that have been invented. For example, the empty lattice and foam filled configurations provide a rigid structure well suited for the impact or blast mitigation. Also, by inserting anti-ballistic materials into the hollow rods, these structures can be tailored to resist ballistic impacts.

An aspect of an embodiments of the present invention may provide a number of novel and nonobvious features, elements and characteristics, such as but not limited thereto, the following: the use of simple, low cost material forms to design and construct optimized sandwich panels with cores that defeat specific combinations of dynamic and static loadings.

According to the invention, the lightweight periodic cellular structure has a stacked array of hollow or solid structural elements that are bonded at their contact points in order to form a stacked lattice structure. Further arrays may be stacked onto the stacked lattice structure in order to form a periodic cellular structure of varying thickness and depth. Also, structural panels may be added to parallel exterior edges of the stacked lattice structure to form a structural panel.

Further, the hollow structural elements are provided with wicking elements along their interior walls to facilitate heat transfer through the periodic cellular structure. Liquid may also be introduced into the hollow structural elements to further facilitate heat transfer through the periodic cellular structure. Also, the cellular structure may be utilized as light weight current collectors, such as electrodes, anodes, and cathodes.

The method of manufacturing the periodic cellular structure can accommodate a variety of cross-sectional shapes for the hollow structural members. In addition, the method may introduce a variety of stacking offset angles to vary the lattice shape and resultant mechanical characteristics of the periodic cellular structure. Finally, the method also allows for the bending of the array of hollow or solid structural elements into an array of hollow pyramidal truss elements that can be used to form a stacked pyramidal structure to serve as an alternative core of the periodic cellular structure.

In one aspect, the present invention lightweight periodic cellular structure provides a first array of hollow and/or solid structural elements located in a first plane along a first axis; and a second array of hollow and/or solid structural elements located in a second plane along a second axis, wherein the second array is stacked immediately on top of the first array and wherein the first axis and the second axis are offset at a desired offset angle, and wherein the second array is bonded to the first array at points of contact where the first array and the second array meet to form a stacked lattice structure.

In another aspect, the present invention provides a method of constructing a lightweight periodic cellular structure comprising the steps of: arranging a first array of parallel hollow and/or solid structural elements in a first plane along a first axis; stacking a second array of parallel hollow and/or solid structural elements in a second plane along a second axis, wherein the first axis and the second axis are offset at a desired offset angle and the second plane is parallel and disposed on the first plane at a plurality of contact points; and bonding the second array to the first array at the plurality of contact points to form a stacked lattice structure.

In another aspect, the present invention arranging a first array of hollow and/or solid parallel structural elements in a first plane along a first axis; stacking a second array of hollow and/or parallel structural elements in a second plane along a second axis, wherein said first axis and said second axis are offset at a desired offset angle and said second plane is parallel and disposed on the first plane at a plurality of contact points; bonding the second array to said first array at said plurality of contact points to form a stacked lattice structure; and bending said stacked lattice structure to a desired bending angle at a select number of said contact points to form a pyramidal cellular core.

An aspect of an embodiment (or partial embodiment) comprises a cellular lattice structure. The cellular lattice structure may comprise: a first array of structural elements located in a first plane along a first axis; a second array of structural elements disposed on a second plane along a second axis, wherein the second array is disposed on top of the first array and wherein the first axis and the second axis are offset at a desired offset angle, and wherein the second array is bonded to the first array at points of contact wherein the first array and the second array meet; and a third array of structural elements located essentially vertically crosswise to the first array and the second array. The lattice may further comprise inserts disposed in the structural elements of the first array, the second array, or the third array or any combination thereof. It should be appreciated that not every contact point is bonded or bonded the same.

An aspect of an embodiment (or partial embodiment) comprises a method of making a cellular lattice structure. The method may comprise: providing a first array of structural elements located in a first plane along a first axis; placing a second array of structural elements located in a second plane along a second axis, wherein the second array is disposed on the first array and wherein the first axis and the second axis are offset at a desired offset angle, and wherein the second array is bonded to the first array at points of contact where the first array and the second array meet; and disposing a third array of structural elements located essentially vertically crosswise to the first array and the second array. The method may further comprise: disposing inserts in the structural elements of the first array, the second array, or third array, or any combination thereof.

The invention itself, together with further objects and attendant advantages, will best be understood by reference to the following detailed description taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS The foregoing and other objects, features and advantages of the present invention, as well as the invention itself, will be more fully understood from the following description of preferred embodiments, when read together with the accompanying drawings, in which:

FIG. 1 is a photographic depiction of a perspective view of a stacked lattice core structure of the present invention where the hollow tube arrays are stacked in alternating perpendicular arrays and bonded to form a stacked lattice core.

FIG. 2 is an photographic depiction of a plan view of a two-layer stacked lattice structure of the present invention where the two hollow tube or solid ligament arrays are stacked and bonded such that the second wire array is offset at an angle less than 90 degrees from the first hollow tube or solid ligament array.

FIG. 3 is a schematic illustration of a perspective view of the stacked lattice periodic cellular structure of the present invention where the hollow tube or solid ligament arrays are stacked in alternating perpendicular arrays and bonded to form a stacked lattice core and structural panels have been bonded to the orthogonal edges of the periodic cellular core to form a structural panel.

FIG. 4 is a schematic illustration of a perspective view of the stacked lattice periodic cellular structure of the present invention where the hollow tube or solid ligament arrays are stacked in alternating perpendicular arrays and bonded to form a stacked lattice core and structural panels have been bonded to the exterior of the stacked lattice core at an angle of 45 degrees from the orthogonal edges of the periodic cellular core to form a structural panel.

FIG. 5 is a schematic illustration of a perspective view of the stacked pyramidal periodic cellular structure of the present invention where the hollow or solid pyramidal truss elements are bonded to form a pyramidal core and structural panels have been bonded to the exterior of the pyramidal core to form a structural panel.

FIG. 6 is a photographic depiction of a side view of the stacked pyramidal periodic cellular structure of the present invention showing the desired bending angle of the pyramidal periodic cellular core.

FIG. 7 is a perspective view of the stacked pyramidal periodic cellular structure shown in FIG. 6.

FIG. 8 is a schematic illustration of one embodiment of the bending technique used to form the stacked pyramidal periodic cellular structure of the present invention.

FIG. 9 is a schematic depiction of a perspective view of a lattice core structure of an embodiment of the present invention where the hollow tube arrays are stacked in alternating perpendicular arrays and bonded to form a stacked lattice core. FIGS.

9(A)-(C) illustrate the desire offset angle are shown at about 0 degrees (0-0 configuration), about 90 degrees of one another (90-0 configuration), and about 90 degree configuration with additional vertical rods (90-0 vertical configuration), respectively. FIG. 10 is a photographic depiction of a perspective view of a stacked lattice core structure of the present invention where the hollow tube arrays are stacked in alternating perpendicular arrays and bonded to form a stacked lattice core. FIG. 10(A) illustrates the desire offset angle are shown at about 90 degrees of one another having four planes or layers, along with a substrate (panel) on both face sides. FIG. 10(B) illustrate the desire offset angle are shown at about 0 degrees of one another (generally aligned) having two planes or layers, as well as a partial frame on the left and right side of the lattice core.

FIGS H(A)-(E) shows the use of an illustrative and non- limiting brazing process for manufacturing the lattice core structure that may be accomplished by fusing aluminum alloy tubes together to make one cohesive core piece and /or attach it to face plates. The 90 degree configuration also includes the vertical rods configuration (90-0 vertical configuration).

FIG. 12. provides a schematic illustration of an embodiment of the lattice structure. Within the hollow tubing, ceramics and foams (or other material as desired or required) may be inserted into any of the first array, second array, or third array structural elements, etc. to armor the lattice structures 110 from ballistic impacts. FIG. 12(A) provides the foam inserts 131, while the second FIG. 12(A) provides ceramic inserts 133. It should be appreciated that any combination of material types or compositions may be included as desired or required for the structures, inserts, or panels disclosed herein. The inserts are provided as vertical and/or horizontal inserts.

FIG. 13 is a schematic depiction of a perspective view of an embodiment of the lattice core structure of the present invention of hollow tube arrays. FIGS.13(A)- (C) illustrate the desire offset angle are shown at about 0 degrees (0-0 configuration), about 90 degrees of one another (0/90 configuration) and about 90 degree configuration with additional vertical rods (90-0 vertical configuration), respectively. Panels, face sheets or substrates are provided on the face or sides of the structure. FIG. 14. provides a schematic illustration of an embodiment of the lattice structure. Within the hollow tubing, ceramics and foams may be inserted to armor the

structures from ballistic impacts. FIG. 14(B) provides the foam and/or ceramic inserts. It should be appreciated that any combination of material types or compositions may be included as well for the inserts or structures. The inserts are provided as vertical and/or horizontal inserts. FIGS 15 shows the use of an illustrative and non- limiting fabrication process for manufacturing an embodiment of the lattice core structure. Steps may be reordered or omitted as desired or required. This fabrication sequence illustrates how square tubes are formed into cellular structures using a dip brazing method followed with a heat treatment process for aluminum. FIGS. 16(A)-(C) are a photographic depiction of two types of elevational views of a lattice core structure of the hollow tube arrays. FIGS. 16(A)-(C) illustrate the desire offset angle are shown at about 0 degrees (0-0 configuration), about 90 degrees of one another (0/90 configuration), and the 0/90 degree configuration with additional vertical rods (0/90/V), respectively. Whereby p/ p _s represents relative core density. Whereby p is the density of the core p _s represents the density of a solid core structure. Panels, face sheets, or substrates are provided on the face or sides of the structure. Although not shown, it should be appreciated that a frame or partial frame may be provided along any of the four edges.

FIG. 17(A) provides a graphical representation of a quasi-static representation of Stress, σ versus Strain, ε for 0-0 core configuration. FIGS. 17(B)-(G) represent the lattice core structure at various percentages of strain, ε, levels.

FIG. 18(A) provides a graphical representation of quasi-static representation of Stress, σ versus Strain, ε for 0/90 core configuration. FIGS. 18(B)-(G) represent the lattice core structure at various percentages of strain, ε, levels. FIG. 19(A) provides a graphical representation of quasi-static representation of Stress, σ versus Strain, ε for 0-90-V core configuration. FIGS. 19(B)-(G) represent the lattice core structure at various percentages of strain, ε, levels.

FIG. 20(A) provides a graphical representation of quasi-static representation of Stress, σ versus Strain, ε for 0-90-V core configuration. FIGS. 20(B)-(G) represent the lattice core structure at various percentages of strains, ε, levels.

FIG. 21. illustrates schematic illustration of a lattice core structure that may be tested by providing the rig that can be operated in a sliding mode to determine the

impulse transferred to the core structure. The rig can be operated in a sliding mode to determine the impulse transferred to the test structure (from the height travelled and knowledge of the pendulum mass) or with the Kolsky bars fixed to measure the transmitted pressure waveform. FIG. 22 is a photographic depiction of an elevation view of a lattice core structure of the present invention of hollow tube arrays comprising four layers or planes, as well has having panels, face sheets, or substrates provided on the face or sides of the structure. FIGS.22(A)-(C) illustrate the desire offset angle are shown at about 0 degrees (0-0 configuration), about 90 degrees of one another (0/90 configuration), and about 90 degree configuration with additional vertical rods (90-0 vertical configuration), respectively. The lattice cores of FIGS.22(A)-(C) relative core densities of 14.8, 14.3 and 18.6 percent, respectively.

FIGS 23(A)-(B) are photographic depictions of elevation views of a lattice core structure of the present invention of hollow tube arrays comprising four layers or planes that have 90 degree configuration with additional vertical rods (0-90 vertical configuration), FIGS.23(A)-(B) represent the lattice core structure subjected to various blast standoff distances. The results from the blast tests were average core strains of 5 percent and 8 percent, respectively, and different standoff distances (24 cm and 19 cm, respectively). Table 1 provides a vertical Rig "Sliding Mode" Specific Impulses (Wet sand) of the an aluminum tube core.

Table 2 provides an Impulse Reduction (% Calibration Block) an aluminum tube core.

DETAILED DESCRIPTION OF THE INVENTION

Turning now to the drawings, the subject invention, as shown In FIGS. 1, 2, 3, and 4 includes a first array of hollow or solid structural elements 1 oriented along a first axis 5 and in a first plane 3. Upon the first array of hollow structural elements 1 are stacked a second array of hollow or solid structural elements 2 oriented along a second axis 6 and in a second plane 4. As shown in FIGS. 1, 2, 3, and 4 the stacked arrays of hollow structural elements 1, 2 are then bonded together at their respective contact points 7. Bonding techniques for attaching the arrays of hollow or solid

structural elements 1, 2 may include: brazing or other transient liquid phases, adhesives, diffusion bonding, resistance welding, electron welding, or laser welding. FIG. 2 shows the first two arrays of hollow or solid structural elements 1, 2 from a top view as well as the contact points 7 where the bonding occurs. FIG. 2 also depicts the offset angle 15 between the first array of hollow or solid structural elements 1 and the second array of hollow or solid structural elements 2. This angle can be varied from 0 to 90 degrees to alter the mechanical properties of the resulting stacked lattice structure 10 shown in FIG. 1, for example.

The resulting stacked lattice structure 10 as shown in FIG. 1 is used as a core for the periodic cellular structure of the present invention. Optionally, located along the inner diameter of the arrays of hollow structural elements 1, 2 are wicking elements (not shown) which act to facilitate heat transfer throughout the stacked lattice structure 10.

In addition, according to the design criteria discussed throughout, other hollow structural designs of the present invention are provided. As shown in co-pending and co-assigned PCT International Application No. PCT/US01/22266, entitled "Heat Exchange Foam," filed on July 16, 2001, and corresponding US Application No. 10/333,004, filed January 14, 2003, of which are hereby incorporated by reference herein in their entirety, there is provided other ways of forming the structural elements that includes a core that is comprised of an open cell having solid or hollow ligaments, foam, and/or interconnected network. The resultant hollow ligaments that have a substantially circular (rounded) cross section will require an internal wicking structure to effect a heat pipe. Otherwise, an interconnected cellular or truss network that has hollow ligaments having a triangular or cusp-like shaped cross section, or an acute-angled corner will not require an internal wicking mechanism to effect a heat pipe. The corner regions of the heat pipe act as return channels or groves.

According to the design criteria discussed throughout, other two-dimensional and three-dimensional structures may be implemented with the present invention as shown in co-pending and co-assigned PCT International Application No. PCT/US02/ 17942, entitled "Multifunctional Periodic Cellular Solids and the Method of Making thereof," filed on June 6, 2002, of which is hereby incorporated by reference herein in its entirety.

According to the design criteria discussed throughout, other two-dimensional and three-dimensional structures may be implemented with the present invention as provided in co-pending and co-assigned PCT International Application No. PCT/USO 1/17363, entitled "Multifunctional Periodic Cellular Solids and the Method of Making thereof," filed on May 29, 2001 , and corresponding US Application No. 10/296,728, filed November 25, 2002, of which are hereby incorporated by reference herein in their entirety.

In addition, because of the tubes being hollow, additional functionality can be readily integrated into the structures described in this document. For example, the hollow nature of the tubes allow for the structure to become a very lightweight current collector for the integration of power storage devices such as batteries. For example, according to the design criteria discussed throughout, as shown in co-assigned PCT International Application No. PCT/USOl/25158, entitled "Multifunctional Battery and Method of Making the Same," filed on August 10, 2001, and corresponding US Application No. 10/110,368, filed July 22, 2002, of which are hereby incorporated by reference herein in their entirety, there is provided other ways of forming current collectors.

There are numerous other functionalities, which can be added into these structures making them ideal candidates for "structure plus" multifunctional materials. As shown in FIGS. 3 and 4, the stacked lattice structure is sandwiched between two parallel structural panels 8 which can be constructed of metal or some non-conductive structural material including polymers or structural composites. The structural panels are affixed to any two parallel exterior surfaces 9 of the stacked lattice structure 10 using any of the bonding techniques listed above for bonding the arrays of hollow structural elements 1,2. The resulting periodic cellular structure is one embodiment of the subject invention.

As shown in FIGS. 1, 2, 3, and 4 the arrays of hollow structural elements 1, 2 may be circular in cross section. The cross sectional shapes of the hollow structural elements may also be varied in order to change the overall structural properties of the stacked lattice structure 10. Possible cross sectional shapes for the hollow structural elements include: circular, triangular, rectangular, square, and hexagonal.

We turn now to an alternate embodiment of the subject invention as shown in FIGS. 5 and 6. In this embodiment as depicted in FIG. 5, a first array of hollow or

solid pyramidal truss elements 12 is oriented along a desired plane or contour. Upon the first array of hollow or solid pyramidal truss elements 1 it is possible to stack additional arrays of hollow or solid pyramidal truss elements oriented as desired (not shown). The array of pyramidal truss elements 12are bonded together at their contact points 7 to serve as the structural core for this embodiment of the subject invention. It should be appreciated that the truss units may be a variety of truss arrangements such as, but not limited thereto, the following: tetrahedral, pyramidal, three-dimensional Kagome or any combination thereof. As in the first embodiment, bonding techniques for attaching the first array of hollow or solid pyramidal truss elements 12 to a second array or third array and structural panel 8 may include: brazing or other transient liquid phases, adhesives, diffusion bonding, resistance welding, electron welding, or laser welding. Also, as in the first embodiment, the offset angle of the legs or ligaments can be varied from 0 to 90 degrees to alter the mechanical properties of the resultant pyramidal structure 12. The resulting pyramidal structure 12 as shown in FIG. 5 and 6 is used as a core for the periodic cellular structure that is an alternate embodiment of the subject invention. As in the first embodiment, located along the inner diameter of the arrays of hollow or solid pyramidal truss elements 12 are wicking elements (not shown) which act to facilitate heat transfer throughout the pyramidal structure 12. As shown in FIGS. 5, 6, and 7, and in a manner similar to the first embodiment, the stacked pyramidal structure is sandwiched between two parallel structural panels 8 which can be constructed of metal or some non-conductive structural material including polymers or structural composites. The structural panels are affixed to any two parallel exterior surfaces 9 of the pyramidal structure 12 using any of the bonding techniques listed above for bonding the arrays of hollow pyramidal truss elements 12.

It should be appreciated that the parallel structural panels 8 as discussed throughout can be planar, substantially planar, and/or curved shape, with various contours as desired. FIG. 6 shows a side view of the alternate embodiment of the subject invention where the core of the periodic cellular structure comprising a stacked pyramidal structure 12 bonded to two structural panels 8 along parallel exterior surfaces 9 of the stacked pyramidal structure 12. FIG. 6 also depicts the desired bending angle 16 of

the arrays of hollow pyramidal truss elements 12. This desired bending angle 16 can be varied between 0 and 180 degrees to adjust the overall mechanical properties of the stacked pyramidal structure 12.

Similarly, FIG. 7 shows a perspective view of the embodiment the stochastic cellular structure shown in FIG. 6, which comprises a pyramidal structure 12 bonded to two structural panels 8 along parallel exterior surfaces 9 of the pyramidal structure 12. FIG. 7 shows the intertwined solid or hollow ligaments of the stochastic hollow or solid pyramidal truss elements 12.

As shown in FIG. 5 the arrays of hollow or solid pyramidal truss elements 12 may be circular in cross section. The cross sectional shapes of the hollow or solid pyramidal truss elements 12 may also be varied as in the first embodiment in order to change the overall structural properties of the pyramidal structure 12. Possible cross sectional shapes for the hollow pyramidal truss elements 12 include: circular, triangular, rectangular, square, and hexagonal. Finally, we turn to the methods for producing the above embodiments of the subject invention. The method for producing the stacked lattice structure 10 as shown in FIGS. 1, 3, and 4 is as described in the above detailed description of the first embodiment. The first and second arrays of hollow structural elements 1,2 are stacked and bonded at their contact points 7 such that the arrays are aligned at a desired offset angle 15. Bonding techniques may include, but are not limited to, the techniques listed above in the detailed description of the first embodiment of the subject invention. The stacking and bonding steps can be repeated to add and bond further arrays of hollow structural elements until a stacked lattice structure 10 of the desired size is obtained. As a final step, structural panels 8 can be added to sandwich the stacked lattice structure 10 along parallel exterior surfaces 9 to form a structural panel.

The method for producing the alternate embodiment stacked pyramidal structure 12 as shown in FIGS. 5 and 6 begins with the stacking of two arrays of hollow structural elements as shown in FIG. 2. First, a first array of hollow structural elements 1 is prepared. Upon this first array 1, is stacked and bonded (using any of the bonding techniques described above) a second array of hollow structural elements 2 to form a two-layer stacked lattice structure as shown in overhead view in FIG. 2. The two-layer stacked lattice structure is them subjected to a bending operation such

that the two layer stacked lattice structure is bent to a desired bending angle 16 as shown in FIG. 6 to form the resulting stacked pyramidal structure 12.

FIG. 8 depicts one method of completing the bending step in order to achieve a desired bending angle 16 of the pyramidal structure 12. A wedge-shaped punch 17 is applied in a direction perpendicular to the planes of the first and second arrays of hollow structural elements 1,2 as shown in FIG. 2. As shown in FIG. 8, the wedge- shaped punch 17 used to bend the two-layer stacked lattice structure into an interlocking die 18 such that the desired bending angle 16 is achieved in the resulting pyramidal structure 12. Alternatively, a press, stamp, or rolling process (e.g., passage through a set of saw-toothed rollers) may be used. An exemplary illustration of an end result is represented by FIGS. 6-7.

The embodiments and methods of manufacture for the embodiments described above provide a number of significant advantages. First of all, the methods of producing these periodic cellular structures allows for infinite variation in the cross- sectional size and shape of the arrays of hollow and solid structural elements 1,2 and the arrays of hollow and solid pyramidal truss elements 12 that make up the resulting stacked lattice structures 10 and stacked pyramidal structures. This flexibility is accomplished while still allowing for hollow passageways within the arrays of hollow structural elements 1, 2 whereby wicking elements 11 and fluids may be introduced in order to obtain optimum heat transfer performance within the periodic cellular structure. An embodiment of the present invention provides for the best heat transfer properties of open cell stochastic metal foams with the geometric and structural certainty of an engineered truss structure.

In addition, an embodiment of the subject invention provides for easy construction using a variety of bonding techniques. Where open cell stochastic metal foams require some stretching and temperature processing to achieve the slightest isotropic tendencies, the present invention provides for exacting control over all of the mechanical properties of the resulting periodic cellular structure by adjustment of: the cross sectional shapes of the arrays of hollow structural elements 1,2, the desired offset angle 15 between the first and second arrays l,2and the desired bending angle 16 in the case of the pyramidal structure 12 described above as the alternate embodiment. In addition, the structural rigidity and surface area of the wicking elements contained within the periodic cellular structure by increasing the density of

parallel hollow structural elements within the stacked arrays 1,2 and pyramidal truss elements 12.

Overall, the subject invention provides a way to combine the best heat transfer capabilities of the open cell stochastic metal foam with the structural integrity and predictability of engineered truss shapes in a method that is simple and inexpensive to perform.

It should be appreciated that various aspects of embodiments of the present method, system, devices, article of manufacture, and compositions may be implemented with the following methods, systems, devices, article of manufacture, and compositions disclosed in the following U.S. Patent Applications, U.S. Patents, and PCT International Patent Applications and are hereby incorporated by reference herein and co-owned with the assignee:

International Application No. PCT/US2008/073377, entitled "Synergistically-Layered Armor Systems and Methods for Producing Layers Thereof," filed August 15,

2008. International Application No. PCT/US2008/060637, entitled "Heat-Managing

Composite Structures," filed April 17, 2008.

International Application No. PCT/US2007/022733, entitled "Manufacture of Lattice Truss Structures from Monolithic Materials," filed October 26, 2007.

International Application No. PCT/US2007/012268, entitled "Method and Apparatus for Jet Blast Deflection," filed May 23, 2007. International Application No. PCT/US04/04608, entitled "Methods for Manufacture of Multilayered Multifunctional Truss Structures and Related Structures There from," filed February 17, 2004, and corresponding U.S. Application No.

10/545,042, entitled "Methods for Manufacture of Multilayered Multifunctional Truss Structures and Related Structures There from," filed August 11, 2005. International Application No. PCT/US03/27606, entitled "Method for Manufacture of Truss Core Sandwich Structures and Related Structures Thereof," filed September 3, 2003, and corresponding U.S. Application No. 10/526,296, entitled "Method for Manufacture of Truss Core Sandwich Structures and Related Structures Thereof," filed March 1, 2005.

International Patent Application Serial No. PCT/US03/27605, entitled "Blast and

Ballistic Protection Systems and Methods of Making Same," filed September 3,

2003

International Patent Application Serial No. PCT/US03/23043, entitled "Method for Manufacture of Cellular Materials and Structures for Blast and Impact Mitigation and Resulting Structure," filed July 23, 2003 International Application No. PCT/US03/16844, entitled "Method for Manufacture of

Periodic Cellular Structure and Resulting Periodic Cellular Structure," filed May

29, 2003, and corresponding U.S. Application No. 10/515,572, entitled "Method for Manufacture of Periodic Cellular Structure and Resulting Periodic Cellular

Structure," filed November 23, 2004. International Application No. PCT/US02/17942, entitled "Multifunctional Periodic

Cellular Solids and the Method of Making Thereof," filed June 6, 2002, and corresponding U.S. Application No. 10/479,833, entitled "Multifunctional Periodic Cellular Solids and the Method of Making Thereof ," filed December 5,

2003. International Application No. PCT/USOl/25158, entitled "Multifunctional Battery and

Method of Making the Same," filed August 10, 2001, U.S. Patent No. 7,211,348 issued May 1, 2007 and corresponding U.S. Application No. 11/788,958, entitled "Multifunctional Battery and Method of Making the Same," filed April 23, 2007.

International Application No. PCT/USO 1/22266, entitled "Method and Apparatus For

Heat Exchange Using Hollow Foams and Interconnected Networks and Method of

Making the Same," filed July 16, 2001, U.S. Patent No. 7,401,643 issued July 22,

2008 entitled "Heat Exchange Foam," and corresponding U.S. Application No. 11/928,161, "Method and Apparatus For Heat Exchange Using Hollow Foams and

Interconnected Networks and Method of Making the Same," filed October 30,

2007. International Application No. PCT/USOl/17363, entitled "Multifunctional Periodic

Cellular Solids and the Method of Making Thereof," filed May 29, 2001, and corresponding U.S. Application No. 10/296,728, entitled "Multifunctional

Periodic Cellular Solids and the Method of Making Thereof ," filed November 25,

2002.

Examples and Experimental Results

Practice of the invention will be still more fully understood from the following examples and experimental results, which are presented herein for illustration only and should not be construed as limiting the invention in any way. Example No. 1

FIG. 9 shows the use of square tubes to fabricate sandwich panels with variable prismatic to honeycomb topologies. FIG 9(A) provides a structure and is called the 0-0 configuration. The lattice structure 110 provides a first array of structural elements 101 along a first axis 5 in a first plane 3. Upon the first array of hollow structural elements 101 are stacked a second array of hollow or solid structural elements 102 oriented along a second axis 6 and in a second plane 4. The stacked arrays of hollow structural elements 101, 102 are then bonded or affixed together at their respective contact points 107. In this set-up, hollow tubes with square, triangular, hexagonal etc cross sections are laid collinearly on-top of one another. Referring to FIG. 9(B), in a second configuration, hollow tubes are laid 90 degrees of one another. Thus, is called the 0-90 configuration. The lattice structure 110 provides a first array of structural elements 101 along a first axis 5 in a first plane 3. Upon the first array of hollow structural elements 101 along a first axis 5 are stacked a second array of hollow or solid structural elements 102 oriented along a second axis 6 and in a second plane 4. The stacked arrays of hollow structural elements 101, 102 are then bonded or affixed together at their respective contact points 107. In this set-up, hollow tubes with square, triangular, hexagonal etc cross sections are laid collinearly on-top of one another.

Finally, referring to FIG. 9(C), the most intricate structure involves adding vertical 6061-T6 Aluminum hollow rods within the cavities of the 0-90 configuration. It should be appreciated that any available material may be used as desired or required including more exotic metals in the future. This configuration is being called 0-90- vertical configuration. The lattice structure 110 provides a first array of structural elements 101 along a first axis 5 in a first plane 3. Upon the first array of hollow structural elements 101 along a first axis 5 in a first plane 3 are stacked a second array of hollow or solid structural elements 102 oriented along a second axis 6 and in a second plane 4. Further, a third array of structural elements 120 is provided

substantially vertical to both the first and second array in a third axis 121. The third axis may vary from a range of abut 0 to about 90 degrees.

It should be appreciated that the wall thickness and tube dimensions determine the relative density (volume fraction of core occupied by material) which can be varied from less than 0.01 to near 100%. The figures show the use of identical tubes for the 0°, 90° and vertical elements but we envisage structures in which these are independently varied and structures where the 0 and 90° tubes are removed to create a structure with only vertical tubes. An aspect of various embodiments of the present invention provides the ability to freely vary the component of prismatic to honeycomb fraction to be a novelty of the current invention. An aspect of various embodiments of the present invention also envisages structures where the dimensions and fractions of the three elements of the structure to be spatially varied creating regions within the panel of different mechanical response.

Example No. 2

FIG. 10, shows photographs of structures that have already been fabricated using the configurations mentioned previously. FIG. 10(A) provides a photograph is in the 0-90 configuration and is used for impulse tests. The core of the structure is 8" X 8" X 3" and 6061-T6 aluminum is the material of choice. It should be appreciated that any available material may be used as desired or required. The 6061-T6 aluminum plates that sandwich the core together measure 3/16" in thickness. The top sandwich plate is greater than 8" X 8" in area, so it can be mounted to the structure shown in FIG. 21.

FIG. 10(B) provides a photograph is a 21.75" X 21.75" structure. It is in the 0-0 configuration and will be used for blast tests. This structure may be sandwiched between two face sheets of aluminum, but this photograph was intended to show the specifics of the core.

Example No. 3 The tube core structures can be made by any joining process including adhesive bonding, brazing, numerous welding techniques, diffusion bonding, etc. The following schematic, Fig 11, shows the use of a general dip brazing process that can

be used to fuse aluminum alloy tubes together and make one cohesive core piece and /or attach it to face plates.

Example No. 4 The interior of the tubes and/or the open spaces between the tubes can be filled or partially filled with other materials to create desirable panel properties. For example, they can be filled with polymer, metal or ceramic foams. They can also be filled powder particles, fibers or composites of these various materials. The two schematic figures shown in Figure 12 provide two examples of these configurations. Within the hollow tubing, ceramics and foams may be inserted to armor the structures from ballistic impacts. Figure 12(A) provides foam inserts, while Figure 12(B) provides ceramic inserts.

The various figures schematically show, among other things, the type of lattice structures that are being designed. The lattice core incorporates hollow rods in three different geometries. Thus far, 6061 -T6 aluminum has been used to fabricate the cores. However many numerous metals may be used to create these cores. These cores may be fused together through a dip brazing process as shown. The core structure is held together between two face sheets made of the same material as the cores. The hollow square core on its own should provide resistance to explosive blasts. By inserting anti-ballistic materials such as ceramics and foams, may make this structure resistant to ballistic penetration.

Example No. 5 FIG. 13 is a schematic depiction of a perspective view of an embodiment of the lattice core structure of the present invention of hollow tube arrays. FIGS.13(A)- (C) illustrate the desire offset angle are shown at about 0 degrees (0-0 configuration), about 90 degrees of one another (0/90 configuration) and about 90 degree configuration with additional vertical rods (90-0 vertical configuration), respectively. Panels, face sheets or substrates are provided on the face or sides of the structure.

Example No. 6

FIG. 14. provides a schematic illustration of an embodiment of the lattice structure. Within the hollow tubing, ceramics and foams may be inserted to armor the structures from ballistic impacts. FIG. 14(B) provides the foam and/or ceramic inserts. It should be appreciated that any combination of material types or compositions may be included as well for the inserts or structures. The inserts are provided as vertical and/or horizontal inserts.

Example No. 7 FIGS 15 shows the use of an illustrative and non- limiting fabrication process for manufacturing an embodiment of the lattice core structure. Steps may be reordered or omitted as desired or required. This fabrication sequence illustrates how square tubes are formed into cellular structures using a dip brazing method followed with a heat treatment process for aluminum.

Example No. 8

FIGS. 16(A)-(C) are a photographic depiction of two types of elevational views of a lattice core structure of the hollow tube arrays. FIGS. 16(A)-(C) illustrate the desire offset angle are shown at about 0 degrees (0-0 configuration), about 90 degrees of one another (0/90 configuration), and the 0/90 degree configuration with additional vertical rods (0/90/V), respectively. Whereby p/ p _s represents relative core density. Whereby p is the density of the core p _s represents the density of a solid core structure. Panels, face sheets, or substrates are provided on the face or sides of the structure. Although not shown, it should be appreciated that a frame or partial frame may be provided along any of the four edges.

Example No. 9

FIG. 17(A) provides a graphical representation of a quasi-static representation of Stress, σ versus Strain, ε for 0-0 core configuration. FIGS. 17(B)-(G) represent the lattice core structure at various percentages of strain, ε, levels.

Example No. 10

FIG. 18(A) provides a graphical representation of quasi-static representation of Stress, σ versus Strain, ε for 0/90 core configuration. FIGS. 18(B)-(G) represent the lattice core structure at various percentages of strain, ε, levels.

Example No. 11

FIG. 19(A) provides a graphical representation of quasi-static representation of Stress, σ versus Strain, ε for 0-90-V core configuration. FIGS. 19(B)-(G) represent the lattice core structure at various percentages of strain, ε, levels.

Example No. 12

FIG. 20(A) provides a graphical representation of quasi-static representation of Stress, σ versus Strain, ε for 0-90-V core configuration. FIGS. 20(B)-(G) represent the lattice core structure at various percentages of strains, ε, levels.

Example No. 13

FIG. 21. illustrates schematic illustration of a lattice core structure that may be tested by providing the rig that can be operated in a sliding mode to determine the impulse transferred to the core structure. The rig can be operated in a sliding mode to determine the impulse transferred to the test structure (from the height travelled and knowledge of the pendulum mass) or with the Kolsky bars fixed to measure the transmitted pressure waveform.

Example No. 14 FIG. 22 is a photographic depiction of an elevation view of a lattice core structure of the present invention of hollow tube arrays comprising four layers or planes, as well has having panels, face sheets, or substrates provided on the face or sides of the structure. FIGS.22(A)-(C) illustrate the desire offset angle are shown at about 0 degrees (0-0 configuration), about 90 degrees of one another (0/90 configuration), and about 90 degree configuration with additional vertical rods (90-0 vertical configuration), respectively. The lattice cores of FIGS.22(A)-(C) relative core densities of 14.8, 14.3 and 18.6 percent, respectively.

Example No. 15

FIGS 23(A)-(B) are photographic depictions of elevation views of a lattice core structure of the present invention of hollow tube arrays comprising four layers or planes that have 90 degree configuration with additional vertical rods (0-90 vertical configuration), FIGS.23(A)-(B) represent the lattice core structure subjected to various blast standoff distances. The results from the blast tests were average core strains of 5 percent and 8 percent, respectively, and different standoff distances (24 cm and 19 cm, respectively).

Table 1 : Vertical Rig "Sliding Mode" Specific Impulses (Wet sand)

Table 2: Impulse Reduction (% Calibration Block)

Of course it should be understood that a wide range of changes and modifications could be made to the preferred and alternate embodiments described above. It is therefore intended that the foregoing detailed description be understood that it is the following claims, including all equivalents, which are intended to define the scope of this invention.

In summary, while the present invention has been described with respect to specific embodiments, many modifications, variations, alterations, substitutions, and equivalents will be apparent to those skilled in the art. The present invention is not to be limited in scope by the specific embodiment described herein. Indeed, various modifications of the present invention, in addition to those described herein, will be apparent to those of skill in the art from the foregoing description and accompanying drawings. Accordingly, the invention is to be considered as limited only by the spirit and scope of the following claims, including all modifications and equivalents.

Still other embodiments will become readily apparent to those skilled in this art from reading the above-recited detailed description and drawings of certain exemplary embodiments. It should be understood that numerous variations, modifications, and additional embodiments are possible, and accordingly, all such variations, modifications, and embodiments are to be regarded as being within the spirit and scope of this application. For example, regardless of the content of any portion (e.g., title, field, background, summary, abstract, drawing figure, etc.) of this application, unless clearly specified to the contrary, there is no requirement for the inclusion in any claim herein or of any application claiming priority hereto of any particular described or illustrated activity or element, any particular sequence of such activities, or any particular interrelationship of such elements. Moreover, any activity can be repeated, any activity can be performed by multiple entities, and/or any element can be duplicated. Further, any activity or element can be excluded, the sequence of activities can vary, and/or the interrelationship of elements can vary. Unless clearly specified to the contrary, there is no requirement for any particular described or illustrated activity or element, any particular sequence or such activities, any particular size, speed, material, dimension or frequency, or any particularly interrelationship of such elements. Accordingly, the descriptions and drawings are to be regarded as illustrative in nature, and not as restrictive. Moreover, when any number or range is described herein, unless clearly stated otherwise, that number or

range is approximate. When any range is described herein, unless clearly stated otherwise, that range includes all values therein and all sub ranges therein. Any information in any material (e.g., a United States/foreign patent, United States/foreign patent application, book, article, etc.) that has been incorporated by reference herein, is only incorporated by reference to the extent that no conflict exists between such information and the other statements and drawings set forth herein. In the event of such conflict, including a conflict that would render invalid any claim herein or seeking priority hereto, then any such conflicting information in such incorporated by reference material is specifically not incorporated by reference herein.