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Fabrics treated with paraffinic oil and a paraffinic oil-based shear thickening fluid (STF) are evaluated under flammability testing. The tested fabrics include a woven cotton-nylon blend, a woven Kevlar textile, and a hybrid ultrahigh molecular weight polyethylene (UHMWPE) Kevlar felt. The oil-based STF is a colloid of silica nanoparticles in a paraffin oil. Test results show that the flammability of fabrics with oil addition is slightly increased, while the flammability of fabrics with STF addition was unchanged or slightly decreased. These results suggest that oil-based STFs could be used as fabric treatments, such as to enhance ballistic, puncture, or stab performance, without a significantly negative effect on flammability. Furthermore, concepts are presented for tailoring an STF to provide enhanced flammability resistance., The original document contains color images.

Monofilaments with continuous, conformal metal or ceramic coatings could be used to develop new sensing and photonic technologies. This paper discusses the application of thin coatings onto meter-long monofilaments of millimeter-scale diameters. Two separate devices were designed and fabricated to produce uniform coatings over the entire surface area of a monofilament. One device enabled coatings to be applied onto multiple medium-length monofilament segments, the other onto a single longer monofilament. The magnetron sputter deposition (MSD) process was used to apply copper coatings on the order of 10 100 nanometers thick onto both nylon and polycarbonate monofilaments. The resistivity of each coating was measured, and scanning electron microscope and optical microscope analyses were performed. The process was proven viable and produced a useful product; however, a more consistent apparatus may be designed for continuous coating of monofilaments. Though only copper coatings are discussed in this report, the system could also be used to apply a variety of sputtered metal or ceramic coatings and enable new monofilament functionalities., The original document contains color images.

Transport and mechanical properties for a range of knit, woven, and felted fabrics under consideration for extremity protection are reported. The textiles include: knits of silk, polyester, staple aramid, and continuous-filament aramid; plain woven nylon-cotton blend and continuous-filament aramid; and felted aramid and ultrahigh molecular weight polyethylene. Transport properties are characterized via water vapor transport at room temperature and body temperature (ASTM E 96), liquid moisture management (AATCC 195), air permeability (ASTM D 747), drying time, and horizontal wicking (AATCC 198). Mechanical properties are determined via uniaxial bending stiffness (ASTM D 1388), circular bending stiffness (ASTM 4032), stretch testing, and a novel test simulating knee-bend. The results show that the knits are likely to be most comfortable, as they offer high air and water vapor permeability with stretchability and low resistance to bending. Correlations between these measurements and garment comfort, as well as potential approaches for balancing comfort and protection requirements, are discussed., The original document contains color images. Prepared in collaboration with Natick Soldier Research, Development, and Engineering Center, Natick, MA and the Physical Protection Group, Defence Science and Technology Laboratory, Wiltshire, UK.

Development of efficient multifunctional structures is of interest for mass reduction of a variety of U.S. Army platforms. Structural batteries and supercapacitors are of particular interest for their ability to provide energy storage in load-bearing materials. Electrical separation of the electrode materials is required to prevent shorting and reduce self-discharge of the energy storage component. Polymer-based separator materials are typically used in traditional energy storage devices. For multifunctional composite applications this separator must also facilitate interlaminar bonding while maintaining chemical and physical compatibility. A series of potential inter-electrode separator materials, including a cellulosic paper, a microglass paper, and a porous polymer membrane, were investigated for adhesion, resistance, and lap shear strength. Vacuum-assisted resin transfer processing setups were used to fabricate composite-based supercapacitors. Throughout processing, resistance through the cells was monitored using a multimeter, and trends in resistance and overall resistivity were determined. Lap shear tests were conducted to better understand the effect each material would have on system strength as well as the separators adhesion to the resin matrix and carbon fabric electrodes. The mode of failure for each material was also determined. The results of the experiments are instrumental in the determination of the proper electrical separator for use in structural energy storage devices. Initial testing on composite matrix and fiber-dominated properties, tensile modulus and short beam shear strength were also conducted. These experiments give significant insight into proper materials, processing methods, and testing protocols for the lab scale production of multifunctional structural batteries and supercapacitors., The original document contains color images. Prepared in collaboration with ORISE, Oak Ridge, TN (1120-1120-99).

A system for sputter deposition of thin (10 1000 nm) metal and ceramic coatings onto vibro-fluidized beds of microparticles has been fabricated. Coatings are sputtered onto microparticles of various sizes, shapes, and materials. Experiments show that the coating deposition rate onto particles decreases with decreasing particle size for the case of a fixed total bed mass. Factors affecting particle coating thickness also include sputter power and fluidized bed container size. Coating surface morphology is evaluated using scanning electron microscopy. Lower sputter deposition powers create smoother, less porous coatings. Fluidizing parameters such as driving amplitude and frequency are also shown to affect coating morphology. Barrier coatings on salt microparticles are produced and shown to slow the dissolution of the coated salt particles in water. Dual-layer memetal-ceramicoatings are also demonstrated using the sputter deposition technique. A dual-layer aluminum/tin-oxide coating is produced on glass microspheres, which are then shown to have distinct reflectance characteristics and colors. A model is developed to estimate coating thickness based on size, shape, and number of particles., The original document contains color images.

Cephalopods, the class of mollusks that include squid, cuttlefish, and octopus, possess skin with dynamic adaptable appearance. Their unique ability to rapidly change their visual appearance is enabled in part by a layer of skin containing thousands of chromatophore organs. These organs consist of a pigment sac connected to 15-25 radially arranged muscles. Muscle contraction and relaxation controls the expansion state of the sac, which alters the size of its presented area and the skin color. This study examines the chromatophore organs in detail, to investigate the global and local structure and characterize mechanical properties of skin from the squid Loligo pealeii. A biaxial membrane inflation test and digital image correlation was used to measure the biaxial modulus, strain limits, plus strain and damage fields on the skin during bulge experiments. Microscopy was used to examine chromatophore substructures and determine their connectivity and functional relationships with surrounding structures., A reprint from the Proceedings of the Army Science Conference, Orlando, FL, 29 Nov 2010. ORISE 120-1120-99 (GHIORSE). Biological Laboratory, Woods Hole, MA. The original document contains color images.

In this study autonomic self-healing of impact damage in composite materials is shown using a microencapsulated healing agent. The components for self-healing, urea-formaldehyde microcapsules containing dicyclopentadiene (DCPD) liquid healing agent and paraffin wax microspheres containing 10 wt% Grubbs' catalyst, have been successfully incorporated in a woven S2-glass-reinforced epoxy composite. Low-velocity impact tests reveal that the self-healing composite panels are able to autonomically repair impact damage. Fluorescent labeling of damage combined with image processing shows that total crack length per imaged cross-section is reduced by 51% after self-healing. A testing protocol based on compression after impact reveals significant recovery of residual compressive strength (RCS) in self-healing panels. Self-healing panels show a higher threshold impact energy before RCS reduction, and as impact energy increases, RCS recovery decreases. Qualitative inspection shows that crack separation increases with increasing impact energy, indicating that self-healing performance depends on the ability to adequately fill damage volume., Published in the Journal of Composites, Part A, v41 p360-368, 2010.

The penetration behavior of Kevlar fabric intercalated with dry particles and shear thickening fluids (STF), highly concentrated fluid-particle suspensions, is presented. In particular, the role of particle hardness is explored by comparing fabric treatments containing SiO2 particles, which are significantly harder than Kevlar, to treatments containing softer poly(methyl methacrylate) (PMMA) particles. The fabric testing includes yarn pull-out, quasi-static spike puncture, and ballistic penetration resistance, performed on single fabric layers. It was found that both dry particle and STF treatments resulted in improvements in fabric properties relative to neat or poly(ethylene glycol) (PEG) treated fabrics. On comparison of treatments with different particle hardness, the SiO2 materials performed better in all tests than comparable PMMA materials, although the SiO2 treatments caused yarn failure in pull-out testing, reducing the total pull-out energy. In addition, resistance to yarn pull-out was found to be substantially higher for STF-treated fabrics than for dry particle treated fabrics. However, both dry particle addition and STF treatments exhibited comparable enhancements in puncture and ballistic resistance. These observations suggest that viscous stress transfer, friction, and physical entrainment of hard particles into filaments contribute to the demonstrated improvements in the properties of protective fabrics treated with shear thickening fluids., Published in ACS Applied Materials and Interfaces, v1 n11 p2602-2612, 25 Nov 2009; published online 3 Nov 2009. Prepared in collaboration with Materials Division, U.S. Army Research Laboratory, Aberdeen Proving Ground, MD. The original document contains color images. All DTIC reproductions will be in black and white.

The breathability of a series of ballistic fabrics and shear thickening fluid (STF)-treated ballistic fabrics was evaluated. Breathability was characterized using measurements of water vapor transport rate through fabric samples. The results show that uncoated ballistic fabrics offer good breathability that is only slightly lower than conventional military outer garments. Ballistic fabrics treated with STF show a slight decrease in breathability, as compared with uncoated fabrics. Ballistic fabrics with continuous polymer coatings, however, exhibit very low water vapor transport rates. These results indicate that fabrics treated with STF introduce no significant penalty in breathability relative to conventional, uncoated ballistic fabrics., The original document contains color images. Project No. H7G.

This report is a reprint from the Proceedings of the 2004 Army Science Conference at Orlando, Florida, in 2004. We have developed a multifunctional material concept that combines structural performance with power generation. Such devices would replace inert structural components in U.S. Army systems, such as a ground vehicle body or a soldier's helmet, and simultaneously provide supplementary power for light load applications. The emphasis of our research is two-fold. We are developing structural polymer electrolytes that exhibit desirable ion conductivity, and we are researching augmentation of overall mechanical properties in polymer based power generating devices., The original document contains color images. Published in the Proceedings of the Army Science Conference 2004, held in Orlando, FL on 29 Nov-2 Dec 2004.

This report is a reprint of a paper published in Proceedings of the American Chemical Society Division of Polymeric Materials: Science & Engineering (PMSE Preprints) by the American Chemical Society in Fall 2004. Many current applications demand lighter and stronger structural materials. In addition, more weight efficient power generating devices are needed to support the increasing integration of electronic technology into everyday systems. A multifunctional concept for material development will be presented that combines structural performance with power generation. Such devices would replace inert structural components in common items, such as a vehicle shell, and simultaneously provide supplementary power for light load applications. Particular focus is on the development of polymer electrolyte membranes which exhibit an efficient combination of structural and electrochemical properties. A greater emphasis is placed on structure than is generally seen in the literature. We will present several routes that are underway in our lab to accomplish this goal, including development of fast ion conductive rigid polymers; ion conductive resins or resin scaffolds filled with amorphous polymer; and blending inorganic fibers and fillers with amorphous polymer electrolytes., The original document contains color images. Published in the Proceedings of the American Chemical Society Division of Polymeric Materials: Science and Engineering (PMSE Preprints), v91, Fall 2004, held in Philadelphia, PA on 22-26 Aug 2004.

Photonic bandgap materials (PBGMs) prevent the propagation of electromagnetic waves across certain wavelengths the so-called bandgap. This behavior is the result of periodic variations in the material's dielectric constant, with the location of the bandgap as a function of the spacing between dielectric features. PBGMs show great promise in optoelectronics as waveguides and in sensors. Unfortunately, the large-scale production of PBGMs is difficult. This report proposes a simple low-cost method for PBGM production. A device has been constructed that produces micrometer-sized, monodisperse bubbles that can be assembled into a crystal lattice by surface tension. The bubble crystals can be solidified and preserved using an aqueous acrylamide monomer solution as the medium for bubbling., The original document contains color images.

Many U.S. Army systems depends on the efficient use of material mass and volume. Many components on these systems are often dedicated to power generation and energy storage. Examples include next-generation ground vehicles and individual soldiers, whose sensing and communication equipment requires both continuous and burst power. Many of these systems also include a significant amount of structural and/or armor materials. Therefore, important system-level reductions in mass and volume are possible by creating multifunctional materials that simultaneously offer both power generation or energy storage capabilities with structural or armor properties. Three candidate multifunctional materials are under investigation. First, structural fuel cells have been fabricated by creating skin-core composite structures. In these fuel cells, the skins are composed of thin, glass fiber or carbon fiber reinforced composite laminates. The core consists of layers of open-cell metal foam with a Nafion(R)-based membrane electrode assembly interlayer. This core generates power when hydrogen and oxygen sources are circulated through the porous foam layers. Simultaneously, the high shear and compressive stiffness of the core transfers loads efficiently to the skins, resulting in a structure with high specific stiffness and strength. Secondly, structural lithium-ion batteries are being designed by formulating ion-conductive polymer electrolytes with continuous fiber reinforcement. The electrolytes are designed to balance structural and ion-conduction properties, through the use of functionalized structural polymers, block copolymers, or microscale mixtures of conductive and structural materials. Finally, electroded surfaces have been integrated into continuous fiber reinforced polymeric composites, to create structural capacitors., Presented at the AVT-141 Specialists' Meeting held in Vilnius, Lithuania on 2-4 October 2006 and published in the proceedings as paper 2. See also ADM202433, Multifunctional Structures/Integration of Sensors and Antennas (Les structures multifonctionnelles/l'integration de capteurs et d'antennes), RTO-MP-AVT-141. The original document contains color images.

Polymer electrolytes have potential for use in solid state electrochemical devices owing to favorable material properties. We have developed a multifunctional concept for material development that integrates structural performance with energy storage. One focus of our research is to develop polymer electrolytes that exhibit a desirable combination of mechanical strength and ion conductivity. In the present study, PEG vinyl esters were complexed with lithium triflate and studied as both homopolymer and random copolymer electrolytes. Lithium content was first optimized on a diverse sampling of the set through varied salt concentrations. Homopolymer electrolytes at 30 EO:Li were then characterized. The homopolymers vary in length of PEG oligomers, number of vinyl esters per monomer, and additional functionality. Random copolymer electrolytes were investigated using electrochemically strong monomers and mechanically strong monomers in systematically varied weight percent. The resulting electrochemical and mechanical properties will be discussed as well as the directions of future research., Reprinted from Proceedings of the American Chemical Society Division of Polymeric Materials: Science & Engineering (PMSE Preprints), V93, Fall 2005, Washington, D.C., 28 Aug-1 Sep 2005. The original document contains color images.

We have developed a multifunctional material concept that combines structural performance with power generation. Such devices would replace inert structural components in the U.S. Army systems, such as a ground vehicle body or a soldier's helmet, and simultaneously provide supplementary power for light load applications. The emphasis of our research is two-fold. We are developing structural polymer electrolytes that exhibit desirable ion conductivity, and we are researching augmentation of overall mechanical properties in polymer based power generating devices., See also ADM001736, Proceedings of the Army Science Conference (24th) held in Orlando, FL on 29 Nov-2 Dec 2004.

Yarn pull-out can be an important energy absorption mechanism during the ballistic impact of woven Kevlar fabric. This study reports the effects of fabric length, number of yarns pulled, arrangement of yarns, and transverse tension on the force-displacement curves for yarn pull-out tests on Kevlar KM-2 fabric under laboratory conditions. A semi-empirical model is presented for predicting the yarn pull-out force and energy as a function of pull-out distance, including both yarn uncrimping and subsequent yarn translation. This model is found to replicate the experimental data to a high degree of accuracy, and should prove useful for understanding ballistic experiments and improving computational modeling of fabrics., The original document contains color images.

The energy absorbed in ballistic fabrics is modeled by assuming yarn pull-out including yarn uncrimping and translation as the primary energy absorption mechanisms. Using a semi-empirical model of yarn pull-out based on laboratory tests predictions for ballistic performance of fabrics are compared to ballistic test results. It is demonstrated that quasi-static pull-out results can be correlated quantitatively with yarn pull-out during ballistic impact.

This report provides a review of select Soviet and Russian (SIR) literature from the mid 1960s to the mid 199Os related to residual stresses in wound composite articles. Through a compilation of SIR review articles. a historical overview of the development of this SIR knowledge base is first provided. This overview is then followed by detailed compilations of the following topics: experimental measurement of residual stress development in wound composites. cure shrinkage in neat polymers. residual microsstress development. modeling residual macrostress development. and manufacturing methods for controlling residual macrosnesses in wound composites. This study though not a comprehensive review of SIR residual stress literature. provides a general survey which should prove useful for identifying published sources of SIR technical expertise.

Phase-toughened epoxy/dicyandiamide adhesives were loaded with magnetic particle filler and then cured by induction processing. The effect of induction field magnitude and exposure time on bonding strength of the loaded adhesives was characterized. At low magnetic field amplitudes, bond strength increased significantly with exposure time, with the highest strength bonds occurring after 60-min exposures. At high magnetic field amplitudes, bond strength increased only slightly with exposure time, so that significant bond strength was reached after 15 min of exposure. In general, the induction-cured adhesives exhibited lower bond strengths than comparable oven-cured adhesives. All of these strength trends were likely due to process- induced variations in the adhesive degree of cure, toughening phase development, or thermal degradation.

Large structural composite tubes, prototype components for a proposed U.S. Navy application, are bonded by induction curing of an engineering adhesive. Magnetic powder is used as the susceptor material and is directly incorporated into the adhesive prior to processing. Different induction power supplies, coil designs, and adhesive formulations are investigated. Final demonstration runs bond 9-in-long, 3-in-diameter axisymmetric bondlines in 15 min. These results demonstrate for the first time the successful induction bonding of large structural composite components using magnetic particulate susceptors.

Polystyrene-polyisobutylene-polystyrene (SIBS) block copolymer films have been electrostatically melt processed in order to induce a preferential orientation in the material microstructure. The results show that electrostatic melt processing is inducing some change in the microstructure, but full reorientation is not being achieved. The low dielectric contrast of the SIBS blocks as well as the relatively short electrostatic processing times are the likely causes of incomplete alignment.

The thermal performance of an inductively heated film sandwiched between two identical adherends is investigated. Models for infinite conductivity finite thickness adherends, finite conductivity semi-infinite thickness adherends, and finite conductivity finite thickness adherends are presented. Calculations are performed for polymer-matrix composite, ceramic, and metal adherends for a variety of adherend thicknesses. The results show that for expected bonding applications, film heating rates will be reduced by a factor of l0-l00, as compared with insulated film heating rates with no attached adherends. Higher reductions in heating performance are noted for ceramic and metal adherends as compared with composite adherends. However, even with the most severe reductions in heating rates, bonding with inductively heated films is feasible.

The feasibility of using magnetic particulate susceptor materials for induction heating during bonding of polymer matrix composite materials is investigated. If properly designed, these systems should rapidly heat to the particulate material Curie temperature and dwell at that temperature without feedback control. This performance is only possible by maximizing hysteresis heating while eliminating eddy current heating and shielding effects. Models of eddy current heating, hysteresis heating, field penetration thickness, and heat transfer in a particulate film are presented. These models are then used to predict heating behavior of particulate films containing metallic ferromagnetic (nickel), hard magnetic (strontium ferrite), and soft magnetic (nickel zinc ferrite) materials. The results show that soft or semi-hard insulating magnetic materials are best suited for susceptor particles for a broad range of potential military applications. Polymer films with around 10% volume fraction of these materials should be capable of heating rates up to 100 deg C/s in moderate strength 1-10 MHz induction fields.