Rate-responsive, stretchable devices
Inventors
Wetzel, Eric D. • Nenno, Paul T.
Assignees
United States Department of the Army
Publication Number
US-9303717-B2
Publication Date
2016-04-05
Expiration Date
2033-06-26
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Abstract
Rate-dependent, elastically-deformable devices according to various embodiments can be stretched and recovered at low elongation rates. Yet they become stiff and resistive to stretching at high elongation rates. In one embodiment, a rate-dependent, elastically-deformable device includes an elastically-deformable confinement member; one or more filaments placed inside the elastically-deformable confinement member; and a fluid that substantially fills the remaining volume inside the elastically-deformable confinement member. The resistance force to extension of the device is designed to increase as the extension rate of the device increases. At low elongation rates the filaments can readily slide past each other. At high elongation rates, the fluid transforms to a less flowable material that greatly increases the force and energy required for elongation; or transforms to a non-flowable material that resists elongation. The devices thus can be stretched and recovered at low elongation rates, but become extremely stiff and resistive to stretching at high elongation rates.
Core Innovation
The invention describes rate-dependent, elastically-deformable devices that can be stretched and recovered at low elongation rates, yet become stiff and resistive to stretching at high elongation rates. The devices include an elastically-deformable confinement member housing one or more filaments and a fluid that substantially fills the remaining interior volume. The resistance force to extension of the device increases as the extension rate of the device increases. At low elongation rates, the filaments slide past each other, while at high elongation rates, the fluid changes to a less flowable or non-flowable material greatly increasing the force and energy required for elongation.
The elastically-deformable confinement member is constructed from resilient materials such as rubber, silicone, elastomers, fluoroelastomers, urethane, natural or synthetic latex, polymers, or thermoplastic elastomers. It may take the form of a stretchable tube, possibly with spiral wound or folded material to facilitate elastic deformation, and may include materials or layers to prevent puncturing by the filaments. The fluid inside may be a non-Newtonian fluid such as a shear thickening fluid (STF), electrorheological fluid, or magnetorheological fluid, designed to change viscosity under different strain rates or in response to electric or magnetic fields.
The filaments inside can be made of steel, polymer, glass, or carbon, with diameters ranging from 0.001 to 10 mm and may be monofilament or multifilament, twisted, braided, flat, or have various shapes to encourage shear interaction. Ends of the filaments may be modified to prevent puncturing the confinement member and may be attached to the confinement member. This structure allows the device to have low resistance at slow elongation and increased resistance or locking at fast elongation, providing a tuned rate-dependent elastic response suitable for various applications.
Claims Coverage
The patent includes three independent claims covering different embodiments of the rate-dependent, elastically-deformable device and its components.
Rate-dependent resistance to extension
The device comprises an elastically-deformable confinement member, one or more filaments inside it, and a fluid filling the remainder volume, wherein the resistance force to extension increases with the extension rate of the device.
Mechanical sealing and filament attachment using barbed plugs
The device includes one or more barbed plugs inserted into the ends of the elastically-deformable confinement member to contain the fluid and mechanically attach at least one end of one filament.
Use of electrorheological fluid with applied electric field
The device contains an electrorheological fluid as the internal fluid and is configured to provide an electric field to the fluid to alter resistance properties dependent on extension rate.
Use of magnetorheological fluid with applied magnetic field
The device contains a magnetorheological fluid as the internal fluid and is configured to provide a magnetic field to the fluid to alter resistance properties dependent on extension rate.
Unattached filaments inside confinement member
The device comprises one or more filaments placed inside the confinement member that are unattached to the confinement member while still enabling rate-dependent resistance to extension.
Shear thickening fluid with non-spherical particles
The device includes a non-Newtonian, shear thickening fluid comprising a suspension with non-spherical solid particles in a liquid, enabling rate-dependent increases in resistance.
Apparatus coupling head and shoulders with device
An apparatus comprising one or more such rate-dependent devices configured to mechanically couple the head and shoulders of an individual wearing the apparatus.
The independent claims define the invention as elastically-deformable confinement members filled with fluids and enclosing filaments providing rate-dependent resistance to extension, including embodiments with mechanical sealing by barbed plugs, electrorheological and magnetorheological fluids with applied fields, unattached filaments, and specific shear thickening fluids with non-spherical particles, as well as an apparatus coupling head and shoulders using such devices.
Stated Advantages
The device stiffens and resists stretching at high elongation rates while allowing stretch and recovery at low rates.
The device can be tailored to particular applications with configured elongation rate response thresholds.
The device responds rapidly to high elongation rates, reaching high resistance force within less than 100 milliseconds.
The device provides high energy absorption during elongation due to the force plateau at high elongation rates.
The device can effectively resist unplanned rapid motions to reduce injury risk in orthotic and protective equipment.
Documented Applications
Orthotic devices such as head and helmet braces, knee braces, ankle braces, back braces, neck braces, wrist braces, and slings.
Wearable equipment including shoes, boots, headgear, belts, and harnesses.
Safety and sporting or athletic equipment and goods.
Robotics and mechanical assemblies including restraints like seat belts, linkages, and vehicle suspension systems.
Clothing and woven textiles, and self-tightening straps or bungee-type cords replacing simple elastic bands or Velcro®.
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