Described is a deformable, variable-stiffness cellular structure. The cellular structure a group of unit cells with each unit cell having a cellular geometry. The group of unit cells are formed of a variable-stiffness composite material (VSM). The VSM has a first stiffness state and a second stiffne
Described is a deformable, variable-stiffness cellular structure. The cellular structure a group of unit cells with each unit cell having a cellular geometry. The group of unit cells are formed of a variable-stiffness composite material (VSM). The VSM has a first stiffness state and a second stiffness state. Additionally, the cellular structure has a first shape and a second shape, with a gradation of shapes between the first shape and second shape. The transition from the first shape to the second shape occurs through using an actuation signal to actuate the VSM to change the stiffness of the cellular structure, thereby allowing the cellular structure to be deformed from the first shape to the second shape, and any shape therebetween. The cellular structure can be locked in the second shape through actuating the VSM from the second stiffness state to the first stiffness state.
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What is claimed is: 1. A morphing cellular structure, comprising a group of unit cells with each unit cell having a cellular geometry, the group of unit cells formed of a variable-stiffness material (VSM), where the VSM has a first stiffness state and a second stiffness state, and where the cellula
What is claimed is: 1. A morphing cellular structure, comprising a group of unit cells with each unit cell having a cellular geometry, the group of unit cells formed of a variable-stiffness material (VSM), where the VSM has a first stiffness state and a second stiffness state, and where the cellular structure has a first shape and a second shape, with a gradation of shapes between the first shape and second shape, and where the transition from the first shape to the second shape occurs through using an actuation signal to actuate the VSM from the first stiffness state to the second stiffness state to change the stiffness of the cellular structure, thereby allowing the cellular structure to be deformed from the first shape to the second shape, and any shape therebetween; and wherein each cell in the cellular structure has a cell wall having a gradation in stiffness property, such that the cell wall has a constant stiffness core inner material that is sandwiched between at least two layers of outer material formed of a variable-stiffness material, where out-of-plane loads are carried by the constant stiffness core inner material. 2. A morphing cellular structure as set forth in claim 1, wherein once in the second shape, the cellular structure can be locked in the second shape through activating the VSM from the second stiffness state to the first stiffness state. 3. A morphing cellular structure as set forth in claim 2, wherein each cell has a plurality of edges, and wherein the cellular structure is deformed from the first shape to the second shape using an external deformation system, the external deformation system being an actuator such that the actuator can be used to apply displacement to the edges of the cellular structure to change the shape of the cellular structure, and wherein the actuator is selected from a group consisting of an electromagnetic motor, a hydraulic cylinder, a pneumatic cylinder, and an ultrasonic piezoelectric motor. 4. A morphing cellular structure as set forth in claim 3, further comprising a pad connected between the actuator and the cellular structure to distribute force provided by the actuator over a larger area of the cellular structure. 5. A morphing cellular structure as set forth in claim 1, wherein the cellular structure is configured to have a ratio selected from a group consisting of a negative Poisson ratio and a positive Poisson ratio. 6. A morphing cellular structure as set forth in claim 1, wherein at least one cell in the cellular structure includes a strain relief, thereby allowing the cell to accommodate global tensile stretching through cell wall bending. 7. A morphing cellular structure as set forth in claim 6, wherein the constant stiffness material is a material selected from a group consisting of steel alloys; aluminum alloys; titanium alloys; glass fiber reinforced polymer; carbon fiber reinforced polymer; polymer fiber reinforced polymer; high stiffness structural polymers; or silicone; a metal; a fiber composite; a polymer; a ceramic; and a semiconductor. 8. A morphing cellular structure as set forth in claim 1, wherein each cell has a cavity and the cavity is filled with a volume changeable elastic material. 9. A morphing cellular structure as set forth in claim 8, wherein the elastic material is elastic foam. 10. A morphing cellular structure as set forth in claim 9, wherein the elastic foam is polymeric foam. 11. A morphing cellular structure as set forth in claim 1, wherein each cell has a wall thickness and the wall thickness is between 1/1000 and ⅕ of a cell length. 12. A morphing cellular structure as set forth in claim 1, wherein the morphing cellular structure has a size and each unit cell in the morphing cellular structure is between approximately one thousandths and one third of the size of the morphing cellular structure. 13. A morphing cellular structure as set forth in claim 1, wherein each unit cell includes cell walls and the morphing cellular structure further comprises a hinge joint having a variable-stiffness material that permits locking/unlocking of selective degrees of freedom between multiple cell walls that are in the cellular structure. 14. A morphing cellular structure as set forth in claim 13, wherein the hinge joint is formed to permit a limited rotation to one desired axis. 15. A morphing cellular structure as set forth in claim 13, wherein the hinge joint is formed to permit a limited rotation to two desired axes. 16. A morphing cellular structure as set forth in claim 13, wherein the hinge joint is formed to permit a limited rotation to three desired axes. 17. A morphing cellular structure as set forth in claim 1, wherein the cellular structure has an external surface and further comprising a solid outer skin covering the external surface. 18. A morphing cellular structure as set forth in claim 17, wherein the skin covering is a material selected from a group consisting of an elastic material which is adhesively bonded to the cell structure, a stretchable fabric material, a thin shape memory polymer, and a VSM. 19. A morphing cellular structure as set forth in claim 17, wherein the skin covering stores elastic energy during transformation so that strain and shape recovery is assisted. 20. A morphing cellular structure as set forth in claim 1, wherein the wall thickness is varied to change deformation properties to control the local strain within each wall and the global strain of the whole structure. 21. A morphing cellular structure as set forth in claim 1, wherein the cellular structure is configured to be deformed by softening the VSM, actuating an actuator using an actuator signal to induce deformation, hardening the VSM, and then releasing the actuator signal. 22. A morphing cellular structure as set forth in claim 1, wherein the cellular structure is configured to change from the first shape to the second shape through an actuation process selected from a group consisting of directly applying loads to the VSM of the cell wall, and incorporating an active material into at least one cell in the cellular structure, where the active material is responsive to a second actuation signal such that when the VSM is in the second stiffness state, the second actuation signal can be actuated to cause the VSM to deform from the first shape to the second shape. 23. A morphing cellular structure as set forth in claim 1, wherein there exists 17 planar symmetry groups and each cell has a cellular geometry and the cellular geometry is selected from a group consisting of the 17 planar symmetry groups. 24. A morphing cellular structure as set forth in claim 1, wherein the actuation signal is a signal selected from a group consisting of a temperature change, redox reaction, pH change, electromagnetic field, chemical reaction, electric current, electric field, and magnetic field. 25. A morphing cellular structure as set forth in claim 1, wherein an active material is attached with the VSM at a hinge joint such that actuation of the active material forces a bending moment at the hinge joint. 26. A morphing cellular structure as set forth in claim 1, wherein the VSM is material selected from a group consisting of shape memory polymers; shape memory alloys; phase changing metals; wax; ice; plastically deforming materials; electrorheological fluids; magnetorheological fluids; electrostrictive materials; piezoelectrictrics materials; magnetostrictive materials; ferromagnetic magnetostrictive materials; magnetorheological elastomers; electrorheological elastomers; and liquid crystal elastomers. 27. A morphing cellular structure, comprising a group of unit cells with each unit cell having a cellular geometry, the group of unit cells being formed of a variable-stiffness material (VSM), where the VSM has a first stiffness state and a second stiffness state, and where the cellular structure has a first shape and a second shape, with a gradation of shapes between the first shape and second shape, and where the transition from the first shape to the second shape occurs through using an actuation signal to actuate the VSM from the first stiffness state to the second stiffness state to change the stiffness of the cellular structure, thereby allowing the cellular structure to be deformed from the first shape to the second shape, and any shape therebetween; and wherein the VSM is embedded with a linear elastic material to allow for bending along one-axis of freedom. 28. A method for forming a morphing cellular structure, comprising an act of forming a group of unit cells with each unit cell having a cellular geometry, the group of unit cells formed of a variable-stiffness material (VSM), where the VSM has a first stiffness state and a second stiffness state, and where the cellular structure has a first shape and a second shape, with a gradation of shapes between the first shape and second shape, and where the transition from the first shape to the second shape occurs through using an actuation signal to actuate the VSM from the first stiffness state to the second stiffness state to change the stiffness of the cellular structure, thereby allowing the cellular structure to be deformed from the first shape to the second shape, and any shape therebetween; and wherein each cell in the cellular structure has a cell wall having a gradation in stiffness property, such that the cell wall has a constant stiffness core inner material that is sandwiched between at least two layers of outer material formed of a variable-stiffness material, where out-of-plane loads are carried by the constant stiffness core inner material. 29. A method as set forth in claim 28, further comprising an act of forming the cellular structure such that when in the second shape, the cellular structure can be locked in the second shape through activating the VSM from the second stiffness state to the first stiffness state. 30. A method as set forth in claim 29, further comprising an act of forming the cellular structure such that each cell has a plurality of edges, and wherein the cellular structure is deformed from the first shape to the second shape using an external deformation system, the external deformation system being an actuator such that the actuator can be used to apply displacement to the edges of the cellular structure to change the shape of the cellular structure, and wherein the actuator is selected from a group consisting of an electromagnetic motor, a hydraulic cylinder, a pneumatic cylinder, and an ultrasonic piezoelectric motor. 31. A method as set forth in claim 30, further comprising an act of connecting a pad between the actuator and the cellular structure to distribute force provided by the actuator over a larger area of the cellular structure.
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