Abstract:
A 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 related method of manufacturing the periodic cellular structure can accommodate a variety of cross-sectional shapes, introduce a variety of stacking offset angles to vary the lattice shape and resultant mechanical characteristics of the periodic cellular structure; and allow 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.

Description:
RELATED APPLICATIONS AND CLAIM OF PRIORITY  
       [0001]     This application is a divisional under 35 U.S.C. § 120 of copending application Ser. No. 10/516,052 filed Nov. 29, 2004, now U.S. Pat. No. ______. The &#39;052 application was a national stage filing of International Application No. PCT/US03/17049, filed on May 30, 2003, which claimed the benefit under 35 U.S.C. § 119(e) of the filing date of U.S. Provisional Application Ser. No. 60/384,159 filed on May 30, 2002, entitled “Active Energy Absorbing Cellular Metals and Method of Manufacturing the Same,” the entire disclosures of which are hereby incorporated in their entirety by reference herein. 
     
    
     FIELD OF INVENTION  
       [0002]     The present invention relates generally to multifunctional cellular metals for structural applications that are capable of 1) recovering their original (undeformed) shape and thickness after impact or crushing (i.e., self-healing) 2) being stored or used in their compressed (i.e., crushed) state and deployed when needed to act as energy absorbing structure or packaging (i.e., deployable energy absorber) and/or 3) acting as an actuator, capable of providing localized or distributed force and displacement, and related methods of using and manufacturing the same.  
       BACKGROUND OF THE INVENTION  
       [0003]     Foams and cellular materials are well established as energy absorbing materials. Styrofoam packaging for computer monitors during shipping, bubble wrap and cardboard are examples. Their energy absorbing capability arises from the deformation (bending, stretching, or buckling) of struts (if open-celled) or membrane walls (if closed-cell) [1]. Closed-cell foams may also rely upon compression of a gas contained within the cell to absorb impact energy.  
         [0004]     Although the foamed and cellular materials we are most familiar with for packaging and energy absorption are practically all polymeric, recent developments have led to a variety of metallic counterparts. Metals and alloys are attractive in these applications owing to their much higher stiffness and strength, and the increased energy they can absorb by deforming plastically (e.g., by dislocation glide). Foamed aluminum alloy can now be produced by injecting air (e.g., Metal Foams: A Design Guide by Michael Ashby, Anthony Evans, Norman Fleck, Loma Gibson, John Hutchinson and Haydn Wadley, Butterworths, 2000) or a foaming agent (TiH2) into the liquid melt and solidifying the froth in a steep temperature gradient at the surface of the bath [2], or by a similar, semi-solid process [3]. These low-cost, high-volume processing routes strongly encouraged increased research into their performance, and the relation between (porous) structure and performance.  
         [0005]     Recent developments by Sypeck and Wadley [4] have led to the development and demonstration of low-cost cellular metals based on woven wire truss structures and formed metal lattices. It is worthwhile to briefly describe both of these approaches/materials.  
         [0006]     Woven wire truss core sandwich panels use a core consisting of lamina of woven wire sheets, which are stacked and bonded using brazing or liquid phase sintering. The lightweight (relative density below 10%) cores are then bonded to metallic face sheets, which may be of the same or a different alloy than the core. Compared to metal foam core panels, such cellular metal beams and panels have been shown to exhibit excellent specific stiffness and strength [5]. The formed metal lattice, or simply truss-core, material is produced by first punching a honeycomb-like array of hexagonal holes from a flat dense sheet of the desired metal or alloy (e.g. 304 stainless steel); specially-designed tooling (consisting of a pair of interpenetrating arrays of pins) is then used to deform the hex sheet into an array of tetrahedral. This is accomplished by pushing every second vertex (i.e., node at which three ligaments within the hex sheet come together) upwards, and at the same time, all other vertices in the opposite direction. The resulting truss-core sheets can then be stacked, either with intermediate sheets (or punched hex sheets), and bonded by brazing, sintering, etc.  
         [0007]     The cellular metal structures based on woven-wire and truss-core approaches are attractive as structural materials because of their exceptional specific properties. However, they are perhaps even more promising as candidates for multifunctional materials applications. In addition to bearing forces and moments as an integral structural component, they will simultaneously be used as heat exchangers, filters, catalysts, batteries, energy absorbers, or actuators. Cellular metals are attractive as energy absorbers not only because they can double as structural members with high specific stiffness and strength. But also because plastic deformation of metals and alloys is an efficient energy absorption mechanism, such materials have very low Poisson ratio (they density while crushing), and the threshold stress for crushing can be accurately controlled by the cellular morphology (size, shape of cells and of the struts and cell walls).  
         [0008]     Recent work by Elzey et al. [6] has led to the development of active, shape-morphing structural components based on 2-D and 3-D truss-core structures combined with SMA elements (actuators). This design has been shown to provide the capability for fully reversible, shape-changing structures. Applications might include mission adaptable wings for aircraft, tunable rotors for helicopters and turbine generators, and deployable space structures. The SMA elements used currently are based on roughly equi-atomic NiTi, which can be induced to undergo a phase transformation from its martensite form (monoclinic crystal structure) to austenite (cubic crystal structure) either by increasing the temperature to above the austenite finish temperature (A f ), or by applying stress at temperatures below the temperature at which the austenite phase is stable. Deformations of up to 8% strain can be absorbed at low temperature (e.g.  
         [0009]     20) by the formation of the martensite phase, and are completely recoverable upon heating to the A f  temperature.  
         [0010]     The present invention relates to, among other things, low-cost cellular metals (e.g. truss-core sandwich panel) and active structures to achieve active, cellular metal materials for use as deployable and reusable energy absorbers and self-healing structural members. The present invention provides low-cost precursors such as the truss-core lattice in combination with active (SMA) elements. The active elements will provide for energy absorption by inelastic deformation (like a conventional metal or alloy), but fully recoverable (like a polymer foam).  
       SUMMARY OF THE INVENTION  
       [0011]     The present invention provides multifunctional cellular metals (or other materials) for structural applications that are capable of recovering their original (undeformed) shape and thickness after impact or crushing (i.e., self-healing). Alternatively, they may normally be stored or used in their compressed (i.e., crushed) state and deployed when needed to act as energy absorbing structure or packaging (i.e., deployable energy absorber). Additionally, present invention multifunctional structures may act as an actuator, capable of providing localized or distributed force and displacement, and related methods of using and manufacturing the same. These active cellular metals (or other materials) are composites consisting of conventional metal/alloy truss structures (or other material structures) in combination with shape memory metal/alloy components (or other material components) and offer high specific strength and stiffness, but which are also deployable energy absorbers or self-healing smart structures.  
         [0012]     An aspect of an embodiment of the present invention provides a multifunctional member adapted for structural deformation and reformation, the multifunctional member comprising at least one active core member. The active core member adapted to deform if exposed to an external force and reform from a deformed state if exposed to a stimulant. The multifunctional member further comprising at least one upper member disposed on the core member. The upper member further comprises at least one protrusion, whereby the protrusions generally protrude in the direction of the active core member. The multifunctional member further comprising at least one lower member disposed on the core member opposite the upper member. The lower member further comprises at least one protrusion, whereby the protrusions generally protrude in the direction of the active core member.  
         [0013]     At least some of said upper protrusions and lower protrusions are aligned relative to one another such they will interpenetrate when subject to the force. An aspect of an embodiment of the present invention provides a multifunctional member adapted for structural deformation and reformation. The multifunctional member comprising at least one active core member. The active cellular core member adapted to deform if exposed to an external force and reform from a deformed state if exposed to a stimulant. The multifunctional member further comprising at least one upper three-dimensional space filling layer disposed on the core member. The upper three-dimensional space filling layer comprises an array of out of plane truss units. The multifunctional member further comprising at least one lower three-dimensional space filling layer disposed on the active core member opposite the upper space filling layer. The lower three-dimensional space filling layer comprises an array of out of plane truss units. At least some of the upper and lower three-dimensional space filling layers are aligned relative to one another such that they will interpenetrate when subjected to the force.  
         [0014]     An aspect of an embodiment of the present invention provides a multifunctional member adapted for structural deformation and reformation. The multifunctional member comprising at least one active core member. The active core member is adapted to deform in tension if exposed to an external force and reform from a deformed state if exposed to a stimulant. The multifunctional member further comprising at least one upper expandable layer that is disposed on the core member. The upper expandable layer comprising an array of expandable units. The upper expandable units having a base dimension as defined by the dimension substantially parallel to the active core member and a height dimension as defined by the dimension substantially perpendicular to the active core member. The multifunctional member further comprising at least one lower expandable layer disposed on the active core member opposite the upper space filling layer. The lower expandable layer comprises an array of expandable units. The lower expandable units having a base dimension as defined by the dimension substantially parallel to the active core member and a height dimension as defined by the dimension substantially perpendicular to the active core member. The upper and lower expandable layers are adapted whereby when subject to the force the height dimensions of at least some of the upper and lower expandable units decrease thereby deforming the active core member in tension.  
         [0015]     An aspect of an embodiment of the present invention provides a multifunctional member adapted for structural deformation and reformation. The multifunctional member comprising at least one active core member. The active core member adapted to deform in tension if exposed to an external force and reform from a deformed state if exposed to a stimulant: The multifunctional member further comprising at least one upper three-dimensional space filling layer disposed on the core member. The upper three-dimensional space filling layer comprised of an array of out of plane truss units. The upper truss units having a base dimension as defined by the dimension substantially parallel to the active core member and a height dimension as defined by the dimension substantially perpendicular to the active core member. The multifunctional member further comprising at least one lower three-dimensional space filling layer disposed on the active core member opposite the upper space filling layer. The lower three-dimensional space filling layer comprises an array of out of plane truss units. The lower truss units having a base dimension as defined by the dimension substantially parallel to the active core member and a height dimension as defined by the dimension substantially perpendicular to the active core member. The upper and lower three-dimensional space filling layers are adapted whereby when subject to the force the height dimensions of at least some of the upper and lower truss units decrease thereby deforming the active core member in tension.  
         [0016]     An aspect of an embodiment of the present invention provides a multifunctional member adapted for structural deformation and reformation. The multifunctional member comprising at least one active core member. The active core member adapted to deform if exposed to an external force and reform from a deformed state if exposed to a stimulant. The multifunctional member further comprising at least one upper exterior member disposed on the core member and at least one lower exterior member disposed on the core member opposite the upper exterior member.  
         [0017]     An aspect of an embodiment of the present invention provides multifunctional member adapted for structural deformation and reformation. The multifunctional member comprising at least one active core member. The active core member adapted to deform if exposed to an external force and reform from a deformed state upon removal of the external force. The multifunctional member further comprising at least one upper member disposed on the core member. The upper member further comprises at least one protrusion, whereby the protrusions generally protrude in the direction of the active core member. The multifunctional member further comprising at least one lower member disposed on the core member opposite the upper member. The lower member further comprises at least one protrusion, whereby the protrusions generally protrude in the direction of the active core member. At least some of the upper protrusions and lower protrusions are aligned relative to one another such they will interpenetrate when subject to the force.  
         [0018]     An aspect of an embodiment of the present invention provides a multifunctional member adapted for structural deformation and reformation. The multifunctional member comprising at least one active core member. The active cellular core member adapted to deform if exposed to an external force and reform from a deformed state upon removal of the external force. The multifunctional member further comprising at least one upper three-dimensional space filling layer disposed on the core member. The upper three-dimensional space filling layer comprises an array of out of plane truss units. The multifunctional member further comprising at least one lower three-dimensional space filling layer disposed on the active core member opposite the upper space filling layer. The lower three-dimensional space filling layer comprises an array of out of plane truss units. At least some of the upper and lower three-dimensional space filling layers are aligned relative to one another such that they will interpenetrate when subjected to the force.  
         [0019]     An aspect of the present invention provides a multifunctional member adapted for structural deformation and reformation. The multifunctional member comprising at least one active core member. The active core member adapted to deform in tension if exposed to an external force and reform from a deformed state upon removal of the external force. The multifunctional member further comprising at least one upper expandable layer disposed on the core member. The upper expandable layer comprising an array of out of expandable units. The upper expandable units having a base dimension as defined by the dimension substantially parallel to the active core member and a height dimension as defined by the dimension substantially perpendicular to the active core member. The multifunctional member further comprising at least one lower expandable layer disposed on the active core member opposite the upper space filling layer. The lower expandable layer comprises an array of expandable units. The lower expandable units having a base dimension as defined by the dimension substantially parallel to the active core member and a height dimension as defined by the dimension substantially perpendicular to the active core member. The upper and lower expandable layers are adapted whereby when subject to the force the height dimensions of at least some of the upper and lower expandable units decrease thereby deforming the active core member in tension.  
         [0020]     An aspect of an embodiment of the present invention provides a multifunctional member adapted for structural deformation and reformation. The multifunctional member comprising at least one active core member. The active core member adapted to deform in tension if exposed to an external force and reform from a deformed state upon removal of the external force. The multifunctional member further comprising at least one upper three-dimensional space filling layer disposed on the core member. The upper three-dimensional space filling layer comprises an array of out of plane truss units. The upper truss units having a base dimension as defined by the dimension substantially parallel to the active core member and a height dimension as defined by the dimension substantially perpendicular to the active core member. The multifunctional member further comprising at least one lower three-dimensional space filling layer disposed on the active core member opposite the upper space filling layer. The lower three-dimensional space filling layer comprised of an array of out of plane truss units. The lower truss units having a base dimension as defined by the dimension substantially parallel to the active core member and a height dimension as defined by the dimension substantially perpendicular to the active core member. The upper and lower three-dimensional space filling layers are adapted whereby when subject to the force the height dimensions of at least some of the upper and lower truss units decrease thereby deforming the active core member in tension.  
         [0021]     An aspect of an embodiment of the present invention provides a multifunctional member adapted for structural deformation and reformation. The multifunctional member comprising at least one active core member. The active core member adapted to deform if exposed to an external force and reform from a deformed state upon removal of the external force. The multifunctional member further comprising at least one upper exterior member disposed on the core member and at least one lower exterior member disposed on the core member opposite the upper exterior member.  
         [0022]     An aspect of an embodiment of the present invention provides a multifunctional member adapted for structural deformation and reformation. The multifunctional member comprising at least one active core member. The active core member adapted to deform if exposed to an external force and reform from a deformed state if exposed to a stimulant. The multifunctional member further comprising at least one upper exterior member disposed on the core member and at least one lower exterior member disposed on the core member opposite the upper exterior member, wherein at least a portion of at least one upper exterior member and at least a portion of at least one lower member interpenetrate one another when subject to the force.  
         [0023]     An aspect of an embodiment of the present invention provides a multifunctional member adapted for structural deformation and reformation. The multifunctional member comprising at least one active core member. The active core member adapted to deform if exposed to an external force and reform from a deformed state upon removal of the external force. The multifunctional member further comprising at least one upper exterior member disposed on the core member at least one lower exterior member disposed on the core member opposite the upper exterior member, wherein at least a portion of at least one upper exterior member and at least a portion of at least one lower member interpenetrate one another when subject to the force.  
         [0024]     An aspect of an embodiment of the present invention provides a multifunctional member adapted for structural deformation and reformation. The multifunctional member comprising at least one active core member. The active core member is adapted to deform in tension if exposed to an external force and reform from a deformed state if exposed to a stimulant. The multifunctional member further comprising at least one upper expandable layer that is disposed on the core member. The upper expandable layer comprising an array of expandable units. The upper expandable units having a base dimension as defined by the dimension substantially parallel to the active core member and a height dimension as defined by the dimension substantially perpendicular to the active core member. The multifunctional member further comprising at least one lower expandable layer disposed on the active core member opposite the upper space filling layer. The lower expandable layer comprises an array of expandable units. The lower expandable units having a base dimension as defined by the dimension substantially parallel to the active core member and a height dimension as defined by the dimension substantially perpendicular to the active core member. The upper and lower expandable layers are adapted whereby when subject to the force the base dimensions of at least some of the upper and lower expandable units increase thereby deforming the active core member in tension.  
         [0025]     An aspect of an embodiment of the present invention provides a multifunctional member adapted for structural deformation and reformation. The multifunctional member comprising at least one active core member. The active core member adapted to deform in tension if exposed to an external force and reform from a deformed state if exposed to a stimulant. The multifunctional member further comprising at least one upper three-dimensional space filling layer disposed on the core member. The upper three-dimensional space filling layer comprised of an array of out of plane truss units. The upper truss units having a base dimension as defined by the dimension substantially parallel to the active core member and a height dimension as defined by the dimension substantially perpendicular to the active core member. The multifunctional member further comprising at least one lower three-dimensional space filling layer disposed on the active core member opposite the upper space filling layer. The lower three-dimensional space filling layer comprises an array of out of plane truss units. The lower truss units having a base dimension as defined by the dimension substantially parallel to the active core member and a height dimension as defined by the dimension substantially perpendicular to the active core member. The upper and lower three-dimensional space filling layers are adapted whereby when subject to the force the base dimensions of at least some of the upper and lower truss units increase thereby deforming the active core member in tension.  
         [0026]     An aspect of the present invention provides a multifunctional member adapted for structural deformation and reformation. The multifunctional member comprising at least one active core member. The active core member adapted to deform in tension if exposed to an external force and reform from a deformed state upon removal of the external force. The multifunctional member further comprising at least one upper expandable layer disposed on the core member. The upper expandable layer comprising an array of out of expandable units. The upper expandable units having a base dimension as defined by the dimension substantially parallel to the active core member and a height dimension as defined by the dimension substantially perpendicular to the active core member. The multifunctional member further comprising at least one lower expandable layer disposed on the active core member opposite the upper space filling layer. The lower expandable layer comprises an array of expandable units. The lower expandable units having a base dimension as defined by the dimension substantially parallel to the active core member and a height dimension as defined by the dimension substantially perpendicular to the active core member. The upper and lower expandable layers are adapted whereby when subject to the force the base dimensions of at least some of the upper and lower expandable units increase thereby deforming the active core member in tension.  
         [0027]     An aspect of an embodiment of the present invention provides a multifunctional member adapted for structural deformation and reformation. The multifunctional member comprising at least one active core member. The active core member adapted to deform in tension if exposed to an external force and reform from a deformed state upon removal of the external force. The multifunctional member further comprising at least one upper three-dimensional space filling layer disposed on the core member. The upper three-dimensional space filling layer comprises an array of out of plane truss units. The upper truss units having a base dimension as defined by the dimension substantially parallel to the active core member and a height dimension as defined by the dimension substantially perpendicular to the active core member. The multifunctional member further comprising at least one lower three-dimensional space filling layer disposed on the active core member opposite the upper space filling layer. The lower three-dimensional space filling layer comprised of an array of out of plane truss units. The lower truss units having a base dimension as defined by the dimension substantially parallel to the active core member and a height dimension as defined by the dimension substantially perpendicular to the active core member. The upper and lower three-dimensional space filling layers are adapted whereby when subject to the force the base dimensions of at least some of the upper and lower truss units increase thereby deforming the active core member in tension.  
         [0028]     These and other objects, along with advantages and features of the invention disclosed herein, will be made more apparent from the description, drawings and claims that follow. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0029]     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:  
         [0030]     FIGS.  1 (A)-(B) are schematic representations of an embodiment of the present invention self-healing/deployable active multifunctional member in both recovered/deployed configuration and collapsed configuration, respectively.  
         [0031]     FIGS.  2 (A)-(B) are schematic representations of an embodiment of the present invention self-healing/deployable active multifunctional member in the reformed/deployed configuration and collapsed configuration, respectively, wherein the core is three dimensional.  
         [0032]      FIG. 2 (C) schematically illustrates an enlarged partial view of a portion of the multifunctional member as shown in  FIG. 2 (A) wherein the active core member is aligned above the lower exterior member (the upper exterior member is not shown).  
         [0033]     FIGS.  3 (A)-(B) are schematic representations of an embodiment of the present invention of a scissors type self-healing/deployable active cellular multifunctional member in both reformed/deployed configuration and collapsed configuration, respectively.  
         [0034]      FIG. 4 (A) schematically illustrates a partial view of an embodiment of the present invention scissor type self-healing/deployable active multifunctional member in the reformed/deployed configuration wherein the core is three-dimensional.  
         [0035]      FIG. 4 (B) schematically illustrates a square cell SMA active core member that corresponds to pyramidal rigid upper and lower truss members.  
         [0036]      FIG. 5  schematically illustrates a partial view of an embodiment of the present invention scissor type self-healing/deployable active multifunctional member in the reformed/deployed configuration wherein the core is a cellular hex sheet corresponding to tetrahedral rigid upper and lower truss members.  
         [0037]      FIG. 6  is a schematic illustration of an active cellular metal applied as a deployable energy absorber.  
         [0038]      FIG. 7  is a schematic illustration of an active cellular metal applied as a self-healing active cellular metal, wherein the active cellular metal commences in a deployed state.  
         [0039]      FIG. 8  is a schematic representation of an embodiment of the present invention self-healing/deployable active multifunctional member in a recovered/deployed configuration having multiple layers.  
         [0040]      FIG. 9  is a schematic representation of an embodiment of the present invention scissor type self-healing/deployable active multifunctional member in a recovered/deployed configuration having multiple layers. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0041]     The present invention provides self-healing or deployable cellular metals or combination thereof, as well as related methods of using and manufacturing the same. The present invention provides composite structures of conventional and shape memory metals or alloys. The present invention relates generally to multifunctional cellular metals (or other materials) for structural applications that are capable of 1) recovering their original (undeformed) shape and thickness after impact or crushing (i.e., self-healing) 2) being stored or used in their compressed (i.e., crushed) state and deployed when needed to act as energy absorbing structure or packaging (i.e., deployable energy absorber) and/or 3) acting as an actuator, capable of providing localized or distributed force and displacement, and related methods of using and manufacturing the same.  
         [0042]     Firstly, in an embodiment the present invention provides a cellular architecture/mechanism based on conventional (i.e., non-SMA) metal/alloy truss structures suspended on shape memory alloy elements (wires, strips, ribbons, sheets (continuous or perforated), or the like). In fact, any pair of interpenetrating topology structures when suspended in this way that responds to compression (crushing or impact) by interpenetration of the rigid truss structures or protrusions (struts) and consequent deformation of the SMA elements (i.e., suspension elements) in tension may be utilized.  
         [0043]     Secondly, in an embodiment the present invention provides a cellular architecture/mechanism analogous to the scissors-jack; it includes rigid (i.e. conventional metal/alloy) truss layers alternating with SMA layers and responds to compression loading by lateral spreading of the trusses or expandable layer, and consequent deformation of the SMA elements in tension. Both embodiment types, described in greater detail below, recover their original (undeformed) configuration (size, shape, etc.) upon heating or stimulating of the SMA elements (i.e., self-healing). Alternatively, the SMA elements may be a pseudo-elastic (super elastic) shape memory alloy (SMA) which does not require heat or other stimuli to recover. Rather, the pseudo-elastic (super elastic) shape memory alloy (SMA) returns to a recovered/reformed state spontaneously and immediately on removal of the external or desired force, i.e., the applied load.  
         [0044]     Alternatively, both of the aforementioned structures may be normally used in their compressed configuration and expanded by heating other stimuli (i.e., deployable) prior to use as an impact energy absorber. Such stimuli include, but not limited thereto electric field, magnetic field, and pressure (e.g., pyrotechnic devices). Alternatively, both of the aforementioned structures may be a pseudo-elastic (super elastic) shape memory alloy (SMA) which does not require heat or other stimuli to recover. Rather, both of the aforementioned structures may be normally used in their compressed configuration and expanded spontaneously and immediately on removal of the external or desired force, i.e., the applied load.  
         [0045]      FIG. 1  schematically illustrates the concept for a two-dimensional suspended truss prototype of a multifunctional member  102 .  FIG. 1 (A) schematically illustrates the multifunctional member  102  in a reformed or recovered state, before an external force  104  is applied to the multifunctional member  102 . Whereas  FIG. 1 (B) schematically illustrates the multifunctional member  102  in a collapsed state, after encountering an external force  104 . Through the addition of heat  106  or other stimuli, the multifunctional member  102  returns to a recovered/reformed state as seen in  FIG. 1 (A). Alternatively, the multifunctional member  102  is a pseudo-elastic (super elastic) shape memory alloy (SMA) which does not require heat or other stimuli to recover. Rather, the multifunctional member  102  returns to a recovered/reformed state spontaneously and immediately on removal of the external force  104 , i.e., the applied load.  
         [0046]     Still referring to  FIG. 1 (A), exemplary component parts of the multifunctional member  102  are seen. In the center of the member  102  is the active core member  110 , having an upper surface  112 , and an opposing lower surface  114 . In the present exemplary embodiment, the active core member  110  is composed of a shape memory alloy (SMA) metallic substance. In proximity to the active core member  110 , adjacent its upper surface  112 , lays a rigid or substantially rigid upper member  116 . Next, adjacent the lower surface  114  of the core member  110  lays a rigid or substantially rigid lower member  118 . The rigid or substantially rigid upper member  116  in the present exemplary embodiment includes a multitude of protrusions  120  or struts or the like adjacent the active core member upper surface  112 . Rigid upper member protrusions  120  or struts can either be an integral part of rigid upper member  116  or attached thereto. The rigid upper member  116  is connected to active core member  110  where the multiple protrusions  120  are adjacent the upper surface  112  of active core member  110  in the present exemplary embodiment, as shown by reference number  117 . The protrusions or struts as discussed throughout this document maybe a variety of structures such as projections, fingers, posts, pillars, pedestals, legs, rods, knobs, arms, tongues, embossments, protuberances, cones, frustums, or the like. The protrusions may be a variety of sizes and shapes or combination thereof including, but not limited thereto, the following: triangular, oval, semi-oval, rectangular, convex, cubicle, egg crate shape, spherical, semi-spherical, rectangular, pyramidal, tetrahedral, circular, cup or triangular. It is also contemplated that truss units may be utilized for the protrusions. In fact, any pair of interpenetrating topology structures when suspended in this way that responds to compression (crushing or impact) by interpenetration of the rigid truss structures or protrusions (struts) and consequent deformation of the SMA elements (i.e., suspension elements) in tension may be utilized.  
         [0047]     In the present exemplary embodiment, the rigid lower exterior member  118  also includes a multitude of protrusions  122  or struts, which can either be an integral part of rigid or substantially rigid lower member  118  or attached thereto. The rigid lower member protrusions  122  are adjacent the lower surface  114  of the active core member  110 . In the present exemplary embodiment, the rigid lower exterior member  118  is connected to active core member  110  where the rigid lower member protrusions  122  are adjacent the lower surface  114  of active core member  110 , as shown by reference number  119 .  
         [0048]     The upper fastening means  117  and lower fastening means  119  can be a variety of mechanical fasteners, interlocking designs, various bonding means, attachment means, or adhesive means. For example, the rigid upper member  116  and rigid lower member  118  can be attached to the active core member  110  using, but not limited the following: fusion bond, splicing, crimping, interlocking designs or sockets, adhesives, metallurgical/chemical bonding, and mechanical fasteners (rivets, screws, threaded fasteners, bolts/nuts, etc.), or any other device. It should be noted that not all rigid upper member protrusions  120  or struts and rigid lower member protrusions  122  or struts need be fastened to active core member  110 , such that a select number of attachments can be made as desired.  
         [0049]     Turning to  FIG. 1 (B), the multifunctional member  102  is seen in the collapsed state, after being subjected to an external force  104  (shown in  FIG. 1 (A)). In the present exemplary embodiment, upper protrusions  120  are adapted to avoid lower protrusions  122  when the multifunctional member  102  is subjected to the external force  104 , allowing greater energy absorption by the multifunctional member  102 . In the present exemplary embodiment, the rigid upper member  116  and rigid lower member  118  do not deform, but instead transfer absorbed energy from the external force  104  to the active core member  110 . The active core member  110  thus deforms in tension when the multifunctional member  102  is subjected to external force  104 .  
         [0050]     When the active core member  110  of the multifunctional member  102  as seen in collapsed form in  FIG. 1 (B) is subjected to heat  106  or other stimuli, it returns to its original, reformed/recovered form as seen in  FIG. 1 (A). In the present exemplary embodiment, when the SMA active core member  110  absorbs heat  106  or other stimulants generated by heat source or stimulant source (not shown), it reforms to its original non-tensioned shape, forcing the entire multifunctional member  102  to return to its original undeformed configuration as seen in  FIG. 1 (A). Alternatively, the SMA active core member  110  is a pseudo-elastic (super elastic) shape memory alloy (SMA) which does not require heat or other stimuli to recover. Rather, the active core member  110  returns to a recovered/reformed state spontaneously and immediately on removal of the external force  104 , i.e., the applied load.  
         [0051]     These approaches are based on a composite structure combining rigid members (compression members) with energy absorbing members (tensile members). The compression members (rigid upper member  116  and rigid lower member  118 ) are effectively suspended by the tensile active core member  110 . The underlying concept on which this class of recoverable structural designs is based is therefore referred to as the suspension structure concept. As the rigid upper exterior member  116  and rigid lower exterior member  118  are pressed together, as during an impact for example, the multifunctional member  102  structure deforms by stretching the active core member  110  in tension. The active core member  110  may be shape memory alloy (SMA) wire, strip, ribbon, or sheet (continuous or perforated), or some other suitable, high-strain, recoverable material. This material could be an elastomer, or a shape memory material that responds to temperature or magnetic or electric field stimulation.  
         [0052]     The multifunctional material  102  may be used as a single layer (i.e. one composite unit layer of conventional plus SMA components), or as a laminate of multiple (repeating) unit layers, as shown in  FIG. 8 , for example.  FIG. 8  schematically illustrates the concept for a two-dimensional suspended truss prototype of a multifunctional member  102  having a multiple repeating layers of the upper exterior members  116 , rigid lower exterior members  118 , and active core members  110 . Additional unit layers increases the total energy which can be absorbed on impact and the total deformation which can be recovered on self-healing of the active core member  110 .  
         [0053]     The multifunctional member  102  of  FIG. 1  comprises two opposing sets of rigid exterior members  116  and  118  (e.g., metal/alloy), each having a multitude of protrusions  120  and  122  (posts, struts or egg crate cups) which are offset such that when adjacent layers of the multifunctional member  102  are pressed together, the rigid exterior member protrusions  120  and  122  interpenetrate. The rigid exterior member protrusions  120  and  122  are interconnected in the present exemplary embodiment by a shape memory alloy (SMA) wire (ribbon or sheet) active core member  110 . An external compressive force  104  is applied normal or oblique to the plane of the multifunctional member  102  (as during impact or crushing) that causes the opposing sets of rigid exterior member protrusions  120  and  122  to interpenetrate and in doing so, deforms the active core member  110  in tension. The deformations of the active core member  110  material (e.g. SMA) acts to absorb energy during impact/crushing.  
         [0054]     Alternatively, as well be discussed in greater detail infra the multifunctional member  102  can be uniformly and intentionally compacted (crushed) into its collapsed state as seen in  FIG. 1 (B), and deployed by introducing heat  106  or other stimuli (or alternatively, upon the removal of a desired, expected, predetermined, resultant, controlled force or forces) to the SMA active core member  110  just prior to an impact of an external force  104 .  
         [0055]     The SMA material discussed throughout this document may be made of from a material or composite of materials including, but not limited thereto, the following: Ni—Ti, Ni—Ti—V, Ni—Ti—Fe, Ni—Ti—Cu, Ni—Ti—C—, Ni—Ti—Cr, Ni—Ti—Nb, Ni—Ti—Pd, Ni—Ti—Fe, Cu—Zn—Al, Cu—Al—Ni and Fe—Mn—Si. The SMA material may also include magnetic SMA and polymer SMA.  
         [0056]     The upper member  116  and lower member  118  may be comprised of but not limited to polymers, metals, or ceramics, or any combination thereof.  
         [0057]     While  FIG. 1  illustrates an exemplary two-dimensional embodiment, the suspension concept is readily extendable to 3-D architectures, as shown by the exemplary embodiment shown in FIGS.  2 (A)-(C). The present exemplary embodiment uses an upper and a lower layer of truss-core lattice layer  350 ,  352  comprised of out of plane truss units  354 ,  356  (consisting of tetrahedral or pyramidal elements, for example, as well as kagome, cone, frustum, and combinations thereof and other non-limiting arrangements) as the rigid or substantially rigid upper member  116  and rigid lower exterior member  118 , respectively, alternating with perforated hexagonal cell SMA sheet active core member  110 . The rigid upper exterior member  116  and rigid lower exterior member  118  are stacked directly over one another so that they will interpenetrate when a crushing force (not shown) is applied normal to the plane of the multifunctional member  102  as seen in  FIG. 2 (B). As the rigid upper exterior member  116  and the rigid lower exterior member  118  layers interpenetrate, the ligaments of the SMA hex cell active core member  110  are deformed in tension. In the present exemplary embodiment, upon the addition of heat  106  or other stimuli to active core member  110 , either by direct resistance, or by some other indirect method, to above the austenite finish A f  temperature, the SMA active core member  110  will revert to its original undeformed configuration as seen in  FIG. 2 (A). This cycle of deformation by exposing the multifunctional member  102  to an external force  104  (not shown), followed by shape memory recovery of the active core member  110  that can be repeated indefinitely.  
         [0058]     Alternatively, the active core member  110  is a pseudo-elastic (super elastic) shape memory alloy (SMA) which does not require heat or other stimuli to recover. Rather, the active core member  110  returns to a recovered/reformed state spontaneously and immediately on removal of the external force  104  (not shown), i.e., the applied load.  
         [0059]     As for the SMA material discussed throughout this document, the SMAs could be those that are stimulated by temperature or magnetic or other stimuli. As an example, consider the metal SMA systems. These should be heated to ensure that they are in the austenite condition, and the heating will be to a temperature to above the so called austenite finish A f . That&#39;s the characteristic temperature to insure that the entire shape memory alloy has reverted to the austenite phase, i.e. the high temperature phase, i.e., the transition temperature. Typically, this is approximately in the range of about 0 to about 170° C., but may be as broad as about −20 to about 770° C. Other transformation temperature ranges may be affected by selecting the alloy composition as required by the intended application, e.g., an optimal temperature range can be chosen by selecting the appropriate actuator material.  
         [0060]     Moreover, the various embodiments described herein, the active cores are provided with a means of heating to a temperature sufficient to achieve the temperature range at the level or rate of change deemed adequate for the intended application. Heating or stimulation may be achieved by direct resistance (Joule) heating of the SMA face sheet (i.e. by the attachment of suitable electrical contacts and the passage of current through the face sheet), by resistance heating of a conductor attached to, or located within the active core, by the use of a heated fluid or gas, by irradiative means (e.g. Xenon lamp, laser, etc.), or other alternative approaches as appreciated by those skilled in the art. Other stimulation may eventually include electric, magnetic, electromagnetic, or perhaps sound fields.  
         [0061]     Alternatively, as will be discussed in greater detail infra the multifunctional member  102  can be uniformly and intentionally compacted (crushed) into its collapsed state as seen in  FIG. 2B , and deployed by introducing heat (not shown) or other stimuli (or alternatively, upon the removal of a desired, expected, predetermined, resultant, or controlled force or forces) to the SMA active core member  110  just prior to an impact of an external force  104 .  
         [0062]     Referring to  FIG. 2 (A), layers of tetrahedral truss core material formed of metal/alloy or polymer rigid members  116  and  118  alternate with a layer of perforated SMA sheet active core member  110  there between. The tetrahedral layers are positioned such that the rigid (or substantially rigid) upper member  116  and rigid (or substantially rigid) lower exterior members  118  nest (interpenetrate) when exposed to an external force (not shown) during compression or crushing as seen in  FIG. 2 (B). As for the 2-D case, the SMA active core member  110  is deformed in tension as the rigid upper member  116  and rigid lower member  118  layers are pressed together (i.e., towards one another) by the external force. To recover the reformed/undeformed configuration of the multifunctional member  102 , the SMA active core member  110  in the present exemplary embodiment is heated (or stimulated) to above the austenite finish A f  temperature or stimulated state as required.  
         [0063]     Alternatively, the active core member  110  is a pseudo-elastic (super elastic) shape memory alloy (SMA) which does not require heat or other stimuli to recover. Rather, the active core member  110  returns to a recovered/reformed state spontaneously and immediately on removal of the external force  104  (not shown), i.e., the applied load.  
         [0064]     Turning to  FIG. 2 (C),  FIG. 2 (C) schematically illustrates an enlarged partial view of a portion of the multifunctional member  102  with the lower member  118  aligned with perforated hexagonal cell SMA sheet active core member  110 . Reference number  121  reveals the location where the node or leg of the upper exterior member  116  (not shown in this view) would contact the upper surface of the active core member  112 .  
         [0065]     An embodiment of the present invention multifunction member is a scissors jack-like concept as illustrated in FIGS.  3 (A)-(B). The scissors jack design concept again relies on truss structures constructed using metal/alloy or polymers and which are subjected primarily to compression and SMA elements deforming in tension and which exhibits deployable/self-healing active behavior. Generally speaking, in its classic configuration, this device comprises four rigid struts connected by pivot points or pins at their ends to form a trapezoid (or better, a diamond shape). If two opposite pivot points or pins are pulled towards one another, the remaining adjacent or proximate two pivot points or pins are forced outwards, away from one another. For example, the automobile scissors jack relies on a threaded bolt or screw to pull the pivot points or pins together, thereby lifting a car as the other two pins are forced apart. Conversely, as the car presses down on the jack, it applies a tensile force to the screw.  
         [0066]     The present invention cellular metal energy absorbing multifunctional member concept replaces the screw actuator with a shape memory alloy element (wire, strip, ribbon, band, sheet (continuous or perforated), or the like) active core member  210  and upper expandable layer  240  and lower expandable layer  242  (e.g., rigid links) comprised of rigid or substantially rigid upper expandable units  244  and lower expandable units  246 .  
         [0067]      FIG. 3 (A) shows an example of a 2-D prototype of the scissors-type structure; the present exemplary embodiment comprises two layers of corrugated metal sheet (e.g., 304 stainless steel), to form the upper expandable layer  240  and a lower expandable layer  242  arranged in mirror symmetry or substantially mirror symmetry about a central SMA active core member  210  sheet. The reformed/undeformed repeating scissors jack element is readily visible when viewed on end, as in  FIG. 3 (A). As the multifunctional member  202  is compressed when exposed to an external force  204  during impact, the corrugated rigid upper and lower expandable layers  240  and  242  (which experience compressive loading) transmit tensile load to the SMA active core member  210 , deforming it in tension in lateral directions or near lateral directions. The resulting structure can be viewed in  FIG. 3 (B). The multifunctional member  202  absorbs energy as it crushes and may be recovered/reformed (redeployed) by applying heat  206  or other stimuli from a heat source (not shown) to the SMA active core member  210  in quantity to bring it to its austenite finish A f  temperature or stimulated state. Alternatively, the multifunctional member  202  is a pseudo-elastic (super elastic) shape memory alloy (SMA) which does not require heat or other stimuli to recover. Rather, the multifunctional member  202  returns to a recovered/reformed state spontaneously and immediately on removal of the external force  204 , i.e., the applied load.  
         [0068]     In the present exemplary embodiment, upper expandable units  224  each have two dimensions. The first of upper expandable units  244  dimension is b u , the linear (or substantially linear) distance measured from one point of contact of the upper expandable unit  244  with the upper surface  212  of active core member  210  to the next immediate such point of contact. The dimension b u  is at least substantially parallel to the upper surface  212  of active core member  210 . The second of upper expandable units  246  dimension is h u , the linear distance measured at least substantially perpendicularly from the upper surface  212  of active core member  210  to a point on the upper expandable unit  244  furthest from the upper surface  212  of the active core member  210 .  
         [0069]     Similarly, in the present exemplary embodiment, lower expandable unit  246  has two dimensions. The first of lower expandable unit dimensions is b 1 , the linear distance measured from one point of contact of the lower expandable unit  246  with the lower surface  214  of active core member  210  to the next immediate such point of contact. The dimension b 1  is parallel to the lower surface  214  of active core member  210 . The second of lower expandable unit  246  dimension is h 1 , the linear distance measured at least substantially perpendicularly from the lower surface  214  of active core member  210  to a point on the lower expandable unit  246  furthest from the lower surface  214  of the active core member  210 .  
         [0070]     In the present exemplary embodiment, when the multifunctional member  202  seen in  FIG. 3 (A) is exposed to an external force  204 , the dimensions b u  and b 1  increase, while the dimensions h u  and h 1  decrease. Conversely, when the SMA active core member  210  of the multifunctional member  202  seen in  FIG. 3 (B) is exposed to heat  206  and reforms to its original undeformed/reformed configuration, the dimensions b u  and b 1  decrease, while the dimensions h u  and b 1  increase. Alternatively, the multifunctional member  202  is a pseudo-elastic (super elastic) shape memory alloy (SMA) which does not require heat or other stimuli to recover. Rather, the multifunctional member  202  returns to a recovered/reformed state spontaneously and immediately on removal of the external force  204 , i.e., the applied load, and reforms to its original undeformed/reformed configuration, the dimensions b u  and b 1  decrease, while the dimensions h u  and h 1  increase.  
         [0071]     The multifunctional structure  202  may be used as a single layer (i.e. one composite unit layer of conventional plus SMA components), or as a laminate of multiple (repeating) unit layers, as shown in  FIG. 9 , for example.  FIG. 9  schematically illustrates the concept for a two-dimensional scissor truss prototype of a multifunctional member  202  having a multiple repeating layers of the upper exterior members  216 , rigid lower exterior members  218 , upper expandable layer  240 , lower expandable layer  242  and active core members  210 . Additional unit layers increases the total energy which can be absorbed on impact and the total deformation which can be recovered on self-healing of the active core member  210 .  
         [0072]     Turning to FIGS.  4 (A)-(B), FIGS.  4 (A)-(B) schematically illustrate partial view of an embodiment of the present invention scissor type self-healing/deployable active multifunctional member  302  in the reformed/deployed configuration wherein the core is three dimensional. As illustrated, for the suspended structure concept, the scissors structure may be extended to 3-D architectures. This example comprises upper three-dimensional space filling layer  350  comprising pyramidal rigid upper truss units  354  and lower three-dimensional space filling layer  352  comprising lower truss units  356  that sandwich perforated square cell SMA active core member  310  sheets. While FIGS.  4 (A)-(B) only show a limited number of pyramidal rigid upper truss units  324  and lower truss units  356  for the sake of simplifying the drawings, it should be understood that a predetermined number of truss units  354 ,  356  may be utilized with the multifunction member  302 .  
         [0073]     Looking particularly at FIGS.  4 (A)-(B), in contrast with the suspended structure of  FIG. 2 , the pyramid units in the present exemplary embodiment are now positioned in mirror symmetry about the SMA sheet  3   10 . Thus, rather than interpenetrating during crushing when the multifunctional member  302  is exposed to an external force (not shown), the pyramids are forced to spread laterally or substantially lateral (i.e. in the plane of the sheet the dimensions b u  and b 1  increasing), stretching the SMA ligaments of the active core member  310  as they do so. The desired upper three-dimensional space filling layer  350  comprised of upper out of plane truss units  354  and the lower three-dimensional space filing layer  352  comprised of lower out of plane truss units  356  are spread laterally.  
         [0074]     In some embodiments, the scissors-type structures comprise pin, rotation, pivot joints/attachments  319  or suitable means to accommodate relative rotation of compressive struts during crushing.  
         [0075]     In operation, when the multifunctional member  302  seen in FIGS.  4 (A)-(B) is exposed to an external force  304 , the dimensions b u  and b 1  increase, while the dimensions h u  and b 1  decrease. Next, when the SMA active core member  310  of the multifunctional member  302  is exposed to heat (not shown) and reforms to its original undeformed/reformed configuration, the dimensions b u  and b 1  decrease, while the dimensions h u  and h 1  increase. Alternatively, the multifunctional member  302  is a pseudo-elastic (super elastic) shape memory alloy (SMA) which does not require heat or other stimuli to recover. Rather, the multifunctional member  302  returns to a recovered/reformed state spontaneously and immediately on removal of the external force, i.e., the applied load, and reforms to its original undeformed/reformed configuration, the dimensions b u  and b 1  decrease, while the dimensions h u  and h 1  increase.  
         [0076]     Similarly, turning to  FIG. 5 ,  FIG. 5  schematically illustrates a partial view of an embodiment of the present invention scissor type self-healing/deployable active multifunctional member  302  in the reformed/deployed configuration wherein the active core  310  is hexagonal cellular. As illustrated, for the suspended structure concept, the scissors structure may be extended to 3-D architectures. This example comprises an upper three-dimensional space filling layer  350  comprised of tetrahedral truss units  354  and lower three-dimensional space filling layer  352  comprised of tetrahedral truss units  356  that sandwich perforated hex cell SMA active core member sheets  3   10 . While  FIG. 5  only show a limited number of upper tetrahedral truss units  354  and lower tetrahedral truss units  356  for the sake of simplifying the drawings, it should be understood that a predetermined number of truss units may be utilized with the multifunction member  302 .  
         [0077]     Looking particularly at  FIG. 5 , in contrast with the suspended structure of  FIG. 2 , the tetrahedra in the present exemplary embodiment are now positioned in mirror symmetry about the SMA sheet  3   10 . Thus, rather than interpenetrating during crushing when the multifunctional member  302  is exposed to an external force (not shown), the tetrahedra are forced to spread laterally or substantially lateral (i.e. in the plane of the sheet the dimensions b u  and b 1  are increasing), stretching the SMA ligaments or legs of the active core member  310  as they do so.  
         [0078]     The active cellular metal based on the scissors-type design provides a strong tendency to expand laterally or near laterally during crushing. If crushing is localized, as during indentation, material surrounding the indentation must somehow accommodate the lateral deformation. In some applications, it shall be important to avoid local buckling of compressive struts, which will occur if no accommodation mechanism is available. Further, scissors-type structures incur relative rotation of compressive struts during crushing. In the absence of any mechanism for rotation of the struts (e.g. pin joint or pivot joints, journals), the rotation must occur by localized deformations in the region where two or more struts connect with each other. Clearly, unless these deformations are kept acceptably small, struts will fail at or near the joint due to static overload or fatigue.  
         [0079]     Turning to FIGS.  6 (A)-(C),  FIG. 6 (A) schematically illustrates how any of the herein mentioned active cores of the multifunctional members can be applied as a deployable energy absorber. The multifunctional member  495  has a active core member  480  that is shown first in its normal (compressed) configuration with the upper exterior member  470  and lower exterior member  490  ( FIG. 6 (A). Next; heating of the SMA elements to the A f  temperature or stimulating the SMA elements causes the cellular structure to deploy as shown in  FIG. 6 (B). Alternatively, the multifunctional member  495  is a pseudo-elastic (super elastic) shape memory alloy (SMA) which does not require heat or other stimuli to recover. Rather, the multifunctional member  495  returns to a recovered/reformed state spontaneously and immediately on removal of a desired force, i.e., the applied load. The material is then able to absorb energy during an impact by (tensile) deformation of the SMA substructure as shown in  FIG. 6 (C). Finally, the material can be compressed to its normal configuration, ready to be re-deployed on demand as shown in  FIG. 6 (D).  
         [0080]     In contrast,  FIG. 7 (A) schematically illustrates the multifunctional member already in its deployed state, i.e., the original (undeformed) configuration. As such, as shown in  FIG. 7 (B), the multifunctional member  495  is subjected to deformation as a result of impact. Finally, the material is able to recover (self heal) its original configuration by activating the shape memory element as shown in  FIG. 7 (C). Alternatively, the multifunctional member  495  is a pseudo-elastic (super elastic) shape memory alloy (SMA) which does not require heat or other stimuli for activation to recover. Rather, the multifunctional member  495  returns to a recovered/reformed state spontaneously and immediately on removal of a desired force, i.e., the applied load.  
         [0081]     Regarding the manufacturing and process development, the active cellular metals described herein may be based on composite laminates of conventional metal/alloy and shape memory alloy precursors, joined (metallurgically or by some other means) to create the final material. The conventional metal/alloy precursors may be manufactured from sheet stock formed either by deformation processing alone (e.g. corrugated sheet structure) or produced by a combination of cutting/punching and forming operations (i.e. the tetrahedral truss-core material). The SMA precursor (or other active material) is either wire, strip or sheet (either as-received or perforated to create a hexagonal cell array).  
         [0082]     Conventional metal/alloy and SMA components may be joined metallurgically at moderate temperature by soldering (e.g. using a specially developed flux in combination with Ag—Sn solder [7]). Intermediate and high temperature joining processes may include brazing and liquid phase sintering. More costly alternatives such as laser and electron beam welding have also demonstrated successful joining with only a moderate effect on shape memory performance reported [8]. Thus, in summary, available bonding techniques include, but not limited to the following: brazing bonded, UV welding bonded, laser welding bonded, electron beam welded, resistance welded, ultrasonically/friction welded, fusion welded or diffusion welding bonded.  
         [0083]     Design and manufacture are also affected by the method chosen for heating the SMA during deployment/healing. Direct resistance (Joule) heating may be considered, but since the SMA components will not, in general, be isolated from contact with the metallic compression components, this may be inefficient and, perhaps more importantly, slow. Alternative means would include use of insulated resistance heating elements (e.g. polyamide coated NiCr wire) either bonded to or wrapped around SMA elements, or the flow of a heated fluid through the cellular structure.  
         [0084]     According to the design criteria discussed throughout, SMA attributes and structures may be implemented with the present invention as described in the co-pending and commonly assigned PCT Application No.: PCT/US02/27116 filed Aug. 26, 2002, entitled “Reversible Shape Memory Multifunctional Structural Designs and Method of Using the Same,” (Publication No.: WO 03/018853 A2) and corresponding U.S. application Ser. No. 10/487,291, filed Feb. 20, 2004, both of which are incorporated by reference herein in their entirety.  
         [0085]     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 Jun. 6, 2002, and corresponding U.S. patent application Ser. No. 10/479,833, filed Dec. 5, 2004, both of which are hereby incorporated by reference herein in their entirety.  
         [0086]     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/US01/17363, entitled “Multifunctional Periodic Cellular Solids and the Method of Making thereof,” filed on May 29, 2001, and corresponding U.S. application Ser. No. 10/296,728, filed Nov. 25, 2002, both of which are hereby incorporated by reference herein in their entirety.  
         [0087]     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/US03/16844, entitled “Method for Manufacture of Periodic Cellular Structure and Resulting Periodic Cellular Structure,” filed on May 29, 2003, and corresponding U.S. application Ser. No. 10/515,572, filed Nov. 23, 2004, both of which are hereby incorporated by reference herein in their entirety.  
         [0088]     The publications as cited throughout this document and provided below are hereby incorporated by reference herein in their entirety.  
         [0089]     [1] Gibson, L. and Ashby, M. F., Cellular Solids—Structure and Properties, Pergamon Press (1988).  
         [0090]     [2] Miyoshi, T., Itoh, M., Akiyama, S. and Kitahara, A., “Aluminum Foam ALPORAS: Production process, properties and applications”, MRS V. 521, 133 (1998).  
         [0091]     [3] Banhart, J. and Baumeister, J., “Production methods for Metallic Foams”, MRS V. 521, 133 (1998).  
         [0092]     [4] Sypeck, D. S. and Wadley, H. N. G., “Cellular Metal Truss core Sandwich Structures”, MetFoam 2001 Conf. Proc. (2001).  
         [0093]     [5] Mumm, D. R., Chiras, S., Evans, A. G., Hutchinson, J. W., Sypeck, D. J. and Wadley, H. N. G., “On the Performance of Lightweight Metallic Panels Fabricated Using Textile Technology”, submitted (2001).  
         [0094]     [6] Elzey, D. M., Sofia, A. and Wadley, H. N. G., “Shape memory-based multifunctional actuator panels”, In: Industrial and Commercial Applications of Smart Structures and Technologies, Proceedings of SPIE Vol. 4698 (2002).  
         [0095]     [7] Pelton, A., Nitinol Devices and Components, NDC NT Flux, Fremont, Calif.  
         [0096]     [8] Tuissi, A., Besseghini, S., Squatrito, F., Pozzi, M., “Effect of Nd-YAG laser welding on the functional properties of Ni-49.6 at. % Ti”, Mat. Sci. &amp; Eng. A 273-275, pp. 813-817 (1999).  
         [0097]     In conclusion, some advantages of the present invention multifunctional cellular structures is that it they are capable of 1) recovering their original (undeformed) shape and thickness after impact or crushing (i.e., self-healing), 2) being stored or used in their compressed (i.e., crushed) state and deployed when needed to act as energy absorbing structure or packaging (i.e., deployable energy absorber), and/or 3) acting as an actuator, capable of providing localized or distributed force and displacement.  
         [0098]     Other advantages of the present invention multifunctional cellular structures, and related methods of using and manufacturing the same, are that they provide: lightweight structural material which is deployable on demand to absorb impact energy; capability to store structures compactly when not in use (undeployed) to absorb energy; light, stiff, and strong structural characteristics; corrosion resistant material if desired; low cost manufacturing capability; and high specific energy absorption with design-tunable crushing stress.  
         [0099]     Further advantages of the present invention multifunctional cellular structures (especially panels), and related methods of using and manufacturing the same, are that they provide: lightweight structural integrity; moderately strong, stiff load-bearing materials; and capability of being joined by conventional joining and attachment means (brazing, welding, mechanical fasteners, etc).  
         [0100]     Still yet, advantages of the present invention multifunctional cellular structures (especially panels), and related methods of using and manufacturing the same, are that they may be applied to a variety of applications including, but not limited thereto: crash/impact energy absorption (deployable) systems for automobile interiors, packaging, crates, containers, weapons containers tossed/parachuted from aircraft/helicopters, architectural applications, interior/exterior panels/padding, aircraft interiors, and military vehicle interiors.  
         [0101]     Finally, advantages of the present invention multifunctional cellular structures (especially panels), and related methods of using and manufacturing the same, are that they may be applied to a variety of applications including, but not limited thereto self-healing cellular metals, automatic body panels, boats/ships hull cladding, and train cars interior/exterior.  
         [0102]     The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. Of course, it should be understood that a wide range of changes and modifications can be made to the preferred embodiment described above. The foregoing embodiments are therefore to be considered in all respects illustrative rather than limiting of the invention described herein. Scope of the invention is thus indicated by the appended claims as read in light of the foregoing description, including all equivalents, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced herein.