Abstract: A variable stiffness structure configured to isolate a mass from unwanted vibrations includes a negative stiffness element and an actuator operatively coupled to the negative stiffness element. The actuator is configured to be actuated to control a stiffness of the negative stiffness element. The variable stiffness structure may also include a positive stiffness element coupled to the negative stiffness element.

Abstract: A watercraft includes a hull having inner and outer surfaces and at least one collapsible strake coupled to the hull. The collapsible strake includes a movable skin hingedly coupled to the hull. The collapsible strake also includes a dampening element and a negative stiffness element each extending from an inner surface of the movable skin to the outer surface of the hull. The movable skin is configured to rotate between an uncollapsed configuration having a first stiffness and a collapsed configuration having a second stiffness greater than the first stiffness.

Abstract: Metal alloy knit fabrics, thermal protective members formed therefrom and their methods of construction are disclosed. This unique capability to knit high temperature metal alloy wire that is drapable allows for the creation of near net-shape preforms at production level speed. Additionally, ceramic insulation can also be integrated concurrently to provide increased thermal protection. The metal alloy knit fabrics described herein overcome the limitations of current welded stainless steel mesh seal coverings by providing coverings that withstand higher operational temperatures than stainless steel, are wear and snag resistant, can be a separate seal layer or as a portion of an integrated seal construction, can accommodate tight curvature changes to achieve complex shapes without wrinkling or buckling, and can be joined in the knitting process, sewed or mechanically fastened, without the need for welding.

Abstract: The knitted textiles include a knitted structure including a plurality of hollow yarns. Each hollow yarn includes a yarn body and defines a yarn hole extending through the yarn body to allow expansion of the yarn body upon inflation of each hollow yarn through the yarn hole. The knitted structure is configured to transition from an unexpanded state to an expanded state in response to the inflation of the hollow yarns through the yarn hole. The knitted structure has a first porosity in the unexpanded state, and the knitted structure has a second porosity in the expanded state. The second porosity is less than the first porosity such that a visibility through the knitted structure is greater when the knitted structure is in the unexpanded state than when the knitted structure is in the expanded state.

Abstract: Knit fabrics having ceramic strands, thermal protective members formed therefrom and to their methods of construction are disclosed. Methods for fabricating thermal protection using multiple materials which may be concurrently knit are also disclosed. This unique capability to knit high temperature ceramic fibers concurrently with a load-relieving process aid, such as an inorganic or organic material (e.g., metal alloy or polymer), both small diameter wires within the knit as well as large diameter wires which provide structural support and allow for the creation of near net-shape performs at production level speed. Additionally, ceramic insulation can also be integrated concurrently to provide increased thermal protection.

Abstract: A variable stiffness structure includes a first negative stiffness element configured to buckle in a first direction, a second negative stiffness element configured to buckle in a second direction opposite to the first direction, and an actuator operatively coupled to ends of the first and second negative stiffness elements to control a stiffness of the variable stiffness structure. The first negative stiffness element and the second negative stiffness element are mode-3 buckling beams.

Abstract: Knit fabrics having ceramic strands, thermal protective members formed therefrom and to their methods of construction are disclosed. Methods for fabricating thermal protection using multiple materials which may be concurrently knit are also disclosed. This unique capability to knit high temperature ceramic fibers concurrently with a load-relieving process aid, such as an inorganic or organic material (e.g., metal alloy or polymer), both small diameter wires within the knit as well as large diameter wires which provide structural support and allow for the creation of near net-shape performs at production level speed. Additionally, ceramic insulation can also be integrated concurrently to provide increased thermal protection.

Abstract: An isolator configured to isolate a payload from unwanted vibrations and shocks. The isolator includes a housing having a first end and a second end opposite the first end, a primary chamber defined in the housing, a backpressure chamber defined in the housing, a conduit placing the primary chamber in fluid communication with the backpressure chamber, a backpressure membrane in the housing proximate the first end, an elastomer dome in the housing proximate the second end, and a shaft connected to the elastomer dome. The primary chamber and the backpressure chamber are between the backpressure membrane and the elastomer dome. The shaft is configured to be connected to the payload.

Abstract: Described is a micro-lattice damping material and a method for repeatable energy absorption. The micro-lattice damping material is a cellular material formed of a three-dimensional interconnected network of hollow tubes. This material is operable to provide high damping, specifically acoustic, vibration or shock damping, by utilizing the energy absorption mechanism of hollow tube buckling, which is rendered repeatable by the micro-lattice architecture.

Abstract: A negative stiffness torsional spring. A plurality of spokes secured between a hub and an outer cylinder assembly are preloaded in compression. As the hub is rotated, the stiffness of the torsional spring is negative over a range of angles.

Abstract: A variable stiffness structure includes a first negative stiffness element configured to buckle in a first direction, a second negative stiffness element configured to buckle in a second direction opposite to the first direction, and an actuator operatively coupled to ends of the first and second negative stiffness elements to control a stiffness of the variable stiffness structure. The first negative stiffness element and the second negative stiffness element are mode-3 buckling beams.

Abstract: A nonlinear mechanical element including a buckling column and hard stops. In one embodiment when the nonlinear mechanical element is subjected to an increasing compressive load, the buckling column buckles at a critical load, resulting in reduced stiffness past the critical load. One or more lateral hard stops may be provided adjacent to the buckling column to prevent the buckling deformation from exceeding a certain extent, and axial hard stops may be provided to shift the load path away from the buckling column when a certain amount of compressive displacement has been reached.

Abstract: Systems and methods are provided for feeding thread at a knitting machine. One embodiment is a thread feeding device which includes a spool that supplies thread to a knitting device through a thread path and a motor that drives the spool. The device and further includes a mobile guide in the thread path that changes position due to changes in thread tension as the knitting device draws thread through the mobile guide. The thread feeding device also includes a sensor that measures a change in position of the mobile guide, and a controller that determines an amount of tension applied to the thread by the knitting device based on the change in position, and adjusts a speed of a motor that drives the spool based on the amount of tension.

Abstract: Systems and methods are provided for feeding thread at a knitting machine. One embodiment is a thread feeding device which includes a spool that supplies thread to a knitting device through a thread path and a motor that drives the spool. The device and further includes a mobile guide in the thread path that changes position due to changes in thread tension as the knitting device draws thread through the mobile guide. The thread feeding device also includes a sensor that measures a change in position of the mobile guide, and a controller that determines an amount of tension applied to the thread by the knitting device based on the change in position, and adjusts a speed of a motor that drives the spool based on the amount of tension.

Abstract: A nonlinear mechanical element including a buckling column and hard stops. In one embodiment when the nonlinear mechanical element is subjected to an increasing compressive load, the buckling column buckles at a critical load, resulting in reduced stiffness past the critical load. One or more lateral hard stops may be provided adjacent to the buckling column to prevent the buckling deformation from exceeding a certain extent, and axial hard stops may be provided to shift the load path away from the buckling column when a certain amount of compressive displacement has been reached.

Abstract: Described is a micro-lattice damping material and a method for repeatable energy absorption. The micro-lattice damping material is a cellular material formed of a three-dimensional interconnected network of hollow tubes. This material is operable to provide high damping, specifically acoustic, vibration or shock damping, by utilizing the energy absorption mechanism of hollow tube buckling, which is rendered repeatable by the micro-lattice architecture.

Abstract: Metal alloy knit fabrics, thermal protective members formed therefrom and their methods of construction are disclosed. This unique capability to knit high temperature metal alloy wire that is drapable allows for the creation of near net-shape preforms at production level speed. Additionally, ceramic insulation can also be integrated concurrently to provide increased thermal protection. The metal alloy knit fabrics described herein overcome the limitations of current welded stainless steel mesh seal coverings by providing coverings that withstand higher operational temperatures than stainless steel, are wear and snag resistant, can be a separate seal layer or as a portion of an integrated seal construction, can accommodate tight curvature changes to achieve complex shapes without wrinkling or buckling, and can be joined in the knitting process, sewed or mechanically fastened, without the need for welding.

Abstract: A new battery structure as disclosed allows convective flow of electrolyte through three-dimensional structured electrodes. Hierarchical battery structure design enables three-dimensional metal structures with fluid transport capabilities. Some variations provide a lithium-ion battery system with convective electrolyte flow, comprising: a positive electrode comprising a lithium-containing electrode material and a conductive network with hollow liquid-transport conduits; a negative electrode comprising a lithium-containing electrode material in the conductive network; a separator that electronically isolates the positive and negative electrodes; and a liquid electrolyte contained within the hollow liquid-transport conduits of the conductive network. The hollow liquid-transport conduits serve as structural members, and the walls of these conduits serve as current collectors. The conductive networks may include a micro-lattice structure with a cellular material formed of hollow tubes.

Abstract: A hydraulic actuator includes a tubular bladder having first and second ends, an expandable and collapsible sleeve provided on the tubular bladder, a fluid inlet fitting provided in fluid communication with the tubular bladder and at least one mechanical connection provided along the tubular bladder. The hydraulic actuator may have flexibility and an overall diameter of less than about 5 mm.

Abstract: Knit fabrics having ceramic strands, thermal protective members formed therefrom and to their methods of construction are disclosed. Methods for fabricating thermal protection using multiple materials which may be concurrently knit are also disclosed. This unique capability to knit high temperature ceramic fibers concurrently with a load-relieving process aid, such as an inorganic or organic material (e.g., metal alloy or polymer), both small diameter wires within the knit as well as large diameter wires which provide structural support and allow for the creation of near net-shape preforms at production level speed. Additionally, ceramic insulation can also be integrated concurrently to provide increased thermal protection.