US Government As Represented by the Secretary of the Army

University of Delaware

Army Research Laboratory

Eric Dean Wetzel

Norman Joseph Wagner

Daniel J O'Brien

Patrick M Toal, Jr

James F Snyder

Emil Jose Sandoz-Rosado

John Joseph La Scala

Larry R Holmes, Jr

Daniel Murphy Baechle

Dominika Nini Lastovickova

Ricardo X Rodriguez

Paul T Nenno

Todd David Beaudet

Radhakrishnan Balu

Keith Wayne Goossen

Dennis W Prather

Daniel George Norton

Garrett Schneider

Joseph Karl Hitt

Robert Bruce Floersheim

Dionisios Vlachos

Michael Ghebrebrhan

Robert Hansbrough Carter

Robert H Lambeth

Joseph T South

Devon J Spinelli

David C McLeod

Greg Allan Thompson

Kevin R Waters

Jared Michael Gardner

Thomas Anthony John Plaisted

David Stanley Lowry

Oleg B Yurchak

Thomas A J Plaisted

Shridrar Yarlagadda

Ryan M Dunn

Kevin R Hart

Two-dimensional (2D) polymers and methods for their formation are described herein. To create oriented 2D polymer films, monomers are combined with processing additives within a solvent, creating a solution that can be cast and dried to remove the solvent and form a solid film. The methods can enable transformation of the monomers into oriented films. Film quality can be controlled via multiple processing parameters, including monomer and additive concentrations, shear and elongational flow rates during casting, evaporation rates, and post-process rinsing, buffering, stretching, and thermal treatments. By combining stiff carbon-containing cyclic polymer nodal units with more compliant linear polymer bridge units in an ordered, 2D repeating molecular structure it is possible to tailor the mechanical properties of 2D polymers and their assemblies to provide high stiffness, strength, and toughness. The 2D polymer can also be combined with other 2D materials, linear polymers, or reinforcing materials to create 2D polymer composites.

Method for directly creating a film of 2D polymers from monomer solutions

A family of new and novel molecules for mechanically superior two-dimensional (2D) polymers is described herein. By combining stiff carbon-containing cyclic polymer nodal units with more compliant linear polymer bridge units in an ordered, 2D repeating molecular structure it is possible to tailor the mechanical properties of 2D polymers and their assemblies to provide high stiffness, strength, and toughness. Furthermore, the inherent dimensionality of 2D polymers and their ability to be stacked into ordered and chemically interactive ensembles gives them inherent benefits in a variety of barrier and structural applications over current stiff and strong linear polymer technologies.

Two-dimensional polymers comprised of a combination of stiff and compliant molecular units

The disclosed subject matter relates to relate to fibers, textiles, fabrics, clothing and methods that are retroreflective including fibers having a hollow sheath that is filled with retroreflective particles.

Particle-filled retroreflective fiber

A polymer body includes a first thermoplastic polymer, and a second thermoplastic polymer. The first thermoplastic polymer and the second thermoplastic polymer form a continuous solid structure. The first thermoplastic polymer forms an external supporting structure that at least partially envelops the second thermoplastic polymer. A first flow temperature of the first thermoplastic polymer is at least 10&#xb0; C. higher than a second flow temperature of the second thermoplastic polymer. The first thermoplastic polymer may be removable by exposure to a selective solvent.

High strength 3D-printed polymer structures and methods of formation

Impact energy absorbing devices, in some embodiments, may be configured as a helmet having suspension elements employing 'rate activated tethers' (RATs), a speed-sensitive flexible strapping material. The RATs are configured to suspend a helmet shell on the head of a wearer, so that impact to the helmet causes extension of the RATs. The RATs provide for: (1) steady force over long strokes, and (2) a stroke force that increases with increasing impact velocity. Standard impact testing of a helmeted headform shows that the RAT suspension decreases head accelerations by 50% relative to a standard suspension system. This decrease in head acceleration is expected to lead to a reduced likelihood of brain and head injury. Because the RATs absorb energy during tensile extension, they offer increases in energy absorption efficiency. These RAT suspensions can potentially replace or complement existing helmet pad and suspension systems in military, sports, and industrial safety-wear.

Rate-activated helmet suspension

A thermoplastic filament comprising multiple polymers of differing flow temperatures in a regular geometric arrangement, and a method for producing such a filament, are described. Because of the difference in flow temperatures, there exists a temperature range at which one polymer is mechanically stable while the other is flowable. This property is extremely useful for creating thermoplastic monofilament feedstock for three-dimensionally printed parts, wherein the mechanically stable polymer enables geometric stability while the flowable polymer can fill gaps and provide strong bonding and homogenization between deposited material lines and layers. These multimaterial filaments can be produced via thermal drawing from a thermoplastic preform, which itself can be three-dimensionally printed. Furthermore, the preform can be printed with precisely controlled and complex geometries, enabling the creation of monofilament and fiber with unique decorative or functional properties.

Process for creating a polymer filament suitable for use in three-dimensional printing

A thermoplastic filament comprising multiple polymers of differing flow temperatures in a geometric arrangement and an interior channel containing a structural or functional thread therein is described. A method for producing such a filament is also described. Because of the difference in flow temperatures, there exists a temperature range at which one polymer is mechanically stable while the other is flowable. This property is extremely useful for creating thermoplastic monofilament feedstock for three-dimensionally printed parts, wherein the mechanically stable polymer enables geometric stability while the flowable polymer can fill gaps and provide strong bonding and homogenization between deposited material lines and layers. These multimaterial filaments can be produced via thermal drawing from a thermoplastic preform, which itself can be three-dimensionally printed. Furthermore, the preform can be printed with precisely controlled and complex geometries, enabling the creation of a filament or fiber with an interior thread contained within the outer, printed filament or fiber. This thread adds structural reinforcement or functional properties, such as electrical conductivity or optical waveguiding, to the filament.

Process for creating a filament

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. These device can be utilized in orthotics, braces, and circulation-enhancing compression garments for the prevention of injury, promotion of personal health, and/or enhancement in human performance. The rate-responsive properties of the devices are critical performance enablers, as they allow the devices to provide a unique balance of comfort and performance that cannot be achieved with conventional, passive straps, braces, and compression garments.

Orthotics having rate-responsive, stretchable devices

A head restraint system having a rate sensitive device to connect a head restraint to a body of a user. The head restraint system includes a first connector to connect to the head of a user, a second connector connected to the first connector and to a body of the user, wherein one of the first connector and the second connector includes a rate sensitive (RS) device, wherein the first connector and the second connector are configured to restrain the user's head to the user's body at high speed motion of the user's head relative to the user's body and otherwise not restrain the user's head.

Head restraint system having a rate sensitive device

A structural capacitor having a plurality of planar dielectric layers and a plurality of positive and negative electrodes with the positive and negative electrodes alternating between each dielectric layer and methods for making structural capacitors are provided. First and second spaced apart holes are provided through each dielectric layer as well as the electrodes so that the first holes in the electrodes register with the first holes in the dielectric layer and likewise for the second holes. The capacitor is formed by stacking the dielectric layers and electrodes on two spaced apart alignment pins with a positive alignment pin extending through the first holes and a negative alignment pin extending through the second holes in the dielectric layers and electrodes. These alignment pins maintain layer alignment during subsequent thermal and pressure processing to bond together the dielectric and electrode layers into an integral structural material. After processing, the alignment pins are removed and replaced with electrode pins, where the positive electrode pin is in electrical contact only with the positive electrodes and the negative electrode pin is in electrical contact only with the negative electrodes. The electrode pins are used for subsequent electrical and mechanical connectorization to the structural capacitor.

Method for making a structural capacitor

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.

Rate responsive, stretchable devices further improvements

A method and an apparatus for producing metal and ceramic coatings on a fluidized bed of particles or fibers are described. The method utilizes a unique apparatus to transfer vibratory motion through a wall of a deposition chamber in order to produce a fluidized bed of particle or fluidized bed of fibers inside the chamber. The method and apparatus are versatile, allowing particles of different shapes, sizes, materials and masses to be fluidized and coated. The fluidization process allows uniform and conformal coatings on particles and fibers. Coatings of pure metals, alloys, or ceramic materials can be produced.

Apparatus and method for sputter-deposited coatings on fluidized particle beds

A device, assembly and method for clamping single fibers that utilizes snubbing surfaces simultaneously with magnetic gripping action are described. The device can be fabricated at miniature sizes with very low mass and volume, which are desirable requirements for testing of small fibers in highly sensitive force-transducing load frames. Advantageously, the combined use of snubbing surfaces and magnetic gripping greatly reduces the probability of slippage or fiber failure at the grip during testing.

Fiber snubbing clamp using magnetic gripping action

Rate-responsive, stretchable devices

Growing community of inventors

Baltimore, MD, United States of America

Eric Dean Wetzel