Foam structure :from soap froth to solid foams.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kraynik, Andrew Michael

2003-01-01

The properties of solid foams depend on their structure, which usually evolves in the fluid state as gas bubbles expand to form polyhedral cells. The characteristic feature of foam structure-randomly packed cells of different sizes and shapes-is examined in this article by considering soap froth. This material can be modeled as a network of minimal surfaces that divide space into polyhedral cells. The cell-level geometry of random soap froth is calculated with Brakke's Surface Evolver software. The distribution of cell volumes ranges from monodisperse to highly polydisperse. Topological and geometric properties, such as surface area and edge length, of themore » entire foam and individual cells, are discussed. The shape of struts in solid foams is related to Plateau borders in liquid foams and calculated for different volume fractions of material. The models of soap froth are used as templates to produce finite element models of open-cell foams. Three-dimensional images of open-cell foams obtained with x-ray microtomography allow virtual reconstruction of skeletal structures that compare well with the Surface Evolver simulations of soap-froth geometry.« less

Morphological and performance measures of polyurethane foams using X-ray CT and mechanical testing.

PubMed

Patterson, Brian M; Henderson, Kevin; Gilbertson, Robert D; Tornga, Stephanie; Cordes, Nikolaus L; Chavez, Manuel E; Smith, Zachary

2014-08-01

Meso-scale structure in polymeric foams determines the mechanical properties of the material. Density variations, even more than variations in the anisotropic void structure, can greatly vary the compressive and tensile response of the material. With their diverse use as both a structural material and space filler, polyurethane (PU) foams are widely studied. In this manuscript, quantitative measures of the density and anisotropic structure are provided by using micro X-ray computed tomography (microCT) to better understand the results of mechanical testing. MicroCT illustrates the variation in the density, cell morphology, size, shape, and orientation in different regions in blown foam due to the velocity profile near the casting surface. "Interrupted" in situ imaging of the material during compression of these sub-regions indicates the pathways of the structural response to the mechanical load and the changes in cell morphology as a result. It is found that molded PU foam has a 6 mm thick "skin" of higher density and highly eccentric morphological structure that leads to wide variations in mechanical performance depending upon sampling location. This comparison is necessary to understand the mechanical performance of the anisotropic structure.

Application and future of solid foams

NASA Astrophysics Data System (ADS)

Bienvenu, Yves

2014-10-01

To conclude this series of chapters on solid foam materials, a review of industrial current applications and of mid-term market perspectives centred on manmade foams is given, making reference to natural cellular materials. Although the polymeric foam industrial development overwhelms the rest and finds applications on many market segments, more attention will be paid to the emerging market of inorganic-especially metallic-foams (and cellular materials) and their applications, present or upcoming. It is shown that the final applications of solid foams are primarily linked to transport and the present-day development of the different classes of solid foams is contrasted between functional applications and structural applications. xml:lang="fr"

Tooling Foam for Structural Composite Applications

NASA Technical Reports Server (NTRS)

DeLay, Tom; Smith, Brett H.; Ely, Kevin; MacArthur, Doug

1998-01-01

Tooling technology applications for composite structures fabrication have been expanded at MSFC's Productivity Enhancement Complex (PEC). Engineers from NASA/MSFC and Lockheed Martin Corporation have developed a tooling foam for use in composite materials processing and manufacturing that exhibits superior thermal and mechanical properties in comparison with other tooling foam materials. This tooling foam is also compatible with most preimpregnated composite resins such as epoxy, bismaleimide, phenolic and their associated cure cycles. MARCORE tooling foam has excellent processability for applications requiring either integral or removable tooling. It can also be tailored to meet the requirements for composite processing of parts with unlimited cross sectional area. A shelf life of at least six months is easily maintained when components are stored between 50F - 70F. The MARCORE tooling foam system is a two component urethane-modified polyisocyanurate, high density rigid foam with zero ozone depletion potential. This readily machineable, lightweight tooling foam is ideal for composite structures fabrication and is dimensionally stable at temperatures up to 350F and pressures of 100 psi.

Fabrication of superhydrophobic film by microcellular plastic foaming method

NASA Astrophysics Data System (ADS)

Zhang, Zhen Xiu; Li, Ya Nan; Xia, Lin; Ma, Zhen Guo; Xin, Zhen Xiang; Kim, Jin Kuk

2014-08-01

To solve the complicated manufacturing operation and the usage of toxic solvent problems, a simple and novel method to fabricate superhydrophobic film by surface foaming method was introduced in this paper. The superhydrophobic property of the foamed material was obtained at a contact angle >150° and a rolling angle about 8°. The foamed material can instantly generate its superhydrophobicity via peeling process. The effects of blowing agent content, foaming time and peeling rate on the foam structure and superhydrophobicity were studied.

Utilization of fly ash and ultrafine GGBS for higher strength foam concrete

NASA Astrophysics Data System (ADS)

Gowri, R.; Anand, K. B.

2018-02-01

Foam concrete is a widely accepted construction material, which is popular for diverse construction applications such as, thermal insulation in buildings, lightweight concrete blocks, ground stabilization, void filling etc. Currently, foam concrete is being used for structural applications with a density above 1800kg/m3. This study focuses on evolving mix proportions for foam concrete with a material density in the range of 1200 kg/m3 to 1600 kg/m3, so as to obtain strength ranges that will be sufficient to adopt it as a structural material. Foam concrete is made lighter by adding pre-formed foam of a particular density to the mortar mix. The foaming agent used in this study is Sodium Lauryl Sulphate and in order to densify the foam generated, Sodium hydroxide solution at a normality of one is also added. In this study efforts are made to make it a sustainable construction material by incorporating industrial waste products such as ultrafine GGBS as partial replacement of cement and fly ash for replacement of fine aggregate. The fresh state and hardened state properties of foam concrete at varying proportions of cement, sand, water and additives are evaluated. The proportion of ultrafine GGBS and fly ash in the foam concrete mix are varied aiming at higher compressive strength. Studies on air void-strength relationship of foam concrete are also included in this paper.

Structural Performance of a Compressively Loaded Foam-Core Hat-Stiffened Textile Composite Panel

NASA Technical Reports Server (NTRS)

Ambur, Damodar R.; Dexter, Benson H.

1996-01-01

A structurally efficient hat-stiffened panel concept that utilizes a structural foam as a stiffener core material has been designed and developed for aircraft primary structural applications. This stiffener concept is fabricated from textile composite material forms with a resin transfer molding process. This foam-filled hat-stiffener concept is structurally more efficient than most other prismatically stiffened panel configurations in a load range that is typical for both fuselage and wing structures. The panel design is based on woven/stitched and braided graphite-fiber textile preforms, an epoxy resin system, and Rohacell foam core. The structural response of this panel design was evaluated for its buckling and postbuckling behavior with and without low-speed impact damage. The results from single-stiffener and multi-stiffener specimen tests suggest that this structural concept responds to loading as anticipated and has excellent damage tolerance characteristics compared to a similar panel design made from preimpregnated graphite-epoxy tape material.

Polymer-Reinforced, Non-Brittle, Lightweight Cryogenic Insulation

NASA Technical Reports Server (NTRS)

Hess, David M.

2013-01-01

The primary application for cryogenic insulating foams will be fuel tank applications for fueling systems. It is crucial for this insulation to be incorporated into systems that survive vacuum and terrestrial environments. It is hypothesized that by forming an open-cell silica-reinforced polymer structure, the foam structures will exhibit the necessary strength to maintain shape. This will, in turn, maintain the insulating capabilities of the foam insulation. Besides mechanical stability in the form of crush resistance, it is important for these insulating materials to exhibit water penetration resistance. Hydrocarbon-terminated foam surfaces were implemented to impart hydrophobic functionality that apparently limits moisture penetration through the foam. During the freezing process, water accumulates on the surfaces of the foams. However, when hydrocarbon-terminated surfaces are present, water apparently beads and forms crystals, leading to less apparent accumulation. The object of this work is to develop inexpensive structural cryogenic insulation foam that has increased impact resistance for launch and ground-based cryogenic systems. Two parallel approaches will be pursued: a silica-polymer co-foaming technique and a post foam coating technique. Insulation characteristics, flexibility, and water uptake can be fine-tuned through the manipulation of the polyurethane foam scaffold. Silicate coatings for polyurethane foams and aerogel-impregnated polyurethane foams have been developed and tested. A highly porous aerogel-like material may be fabricated using a co-foam and coated foam techniques, and can insulate at liquid temperatures using the composite foam

Forming foam structures with carbon foam substrates

DOEpatents

Landingham, Richard L.; Satcher, Jr., Joe H.; Coronado, Paul R.; Baumann, Theodore F.

2012-11-06

The invention provides foams of desired cell sizes formed from metal or ceramic materials that coat the surfaces of carbon foams which are subsequently removed. For example, metal is located over a sol-gel foam monolith. The metal is melted to produce a metal/sol-gel composition. The sol-gel foam monolith is removed, leaving a metal foam.

Structural assessment of metal foam using combined NDE and FEA

NASA Astrophysics Data System (ADS)

Ghosn, Louis J.; Abdul-Aziz, Ali; Young, Philippe G.; Rauser, Richard W.

2005-05-01

Metal foams are expected to find use in structural applications where weight is of particular concern, such as space vehicles, rotorcraft blades, car bodies or portable electronic devices. The obvious structural application of metal foam is for light weight sandwich panels, made up of thin solid face sheets and a metallic foam core. The stiffness of the sandwich structure is increased by separating the two face sheets by a light weight foam core. The resulting high-stiffness structure is lighter than that constructed only out of the solid metal material. Since the face sheets carry the applied in-plane and bending loads, the sandwich architecture is a viable engineering concept. However, the metal foam core must resist transverse shear loads and compressive loads while remaining integral with the face sheets. Challenges relating to the fabrication and testing of these metal foam panels remain due to some mechanical properties falling short of their theoretical potential. Theoretical mechanical properties are based on an idealized foam microstructure and assumed cell geometry. But the actual testing is performed on as fabricated foam microstructure. Hence in this study, a high fidelity finite element analysis is conducted on as fabricated metal foam microstructures, to compare the calculated mechanical properties with the idealized theory. The high fidelity geometric models for the FEA are generated using series of 2D CT scans of the foam structure to reconstruct the 3D metal foam geometry. The metal foam material is an aerospace grade precipitation hardened 17-4 PH stainless steel with high strength and high toughness. Tensile, compressive, and shear mechanical properties are deduced from the FEA model and compared with the theoretical values. The combined NDE/FEA provided insight in the variability of the mechanical properties compared to idealized theory.

An investigation on the effects of phase change material on material components used for high temperature thermal energy storage system

NASA Astrophysics Data System (ADS)

Kim, Taeil; Singh, Dileep; Zhao, Weihuan; Yua, Wenhua; France, David M.

2016-05-01

The latent heat thermal energy storage (LHTES) systems for concentrated solar power (CSP) plants with advanced power cycle require high temperature phase change materials (PCMs), Graphite foams with high thermal conductivity to enhance the poor thermal conductivity of PCMs. Brazing of the graphite foams to the structural metals of the LHTES system could be a method to assemble the system and a method to protect the structural metals from the molten salts. In the present study, the LHTES prototype capsules using MgCl2-graphite foam composites were assembled by brazing and welding, and tested to investigate the corrosion attack of the PCM salt on the BNi-4 braze. The microstructural analysis showed that the BNi-4 braze alloy can be used not only for the joining of structure alloy to graphite foams but also for the protecting of structure alloy from the corrosion by PCM.

High Temperature Structural Foam

NASA Technical Reports Server (NTRS)

Weiser, Erik S.; Baillif, Faye F.; Grimsley, Brian W.; Marchello, Joseph M.

1997-01-01

The Aerospace Industry is experiencing growing demand for high performance polymer foam. The X-33 program needs structural foam insulation capable of retaining its strength over a wide range of environmental conditions. The High Speed Research Program has a need for low density core splice and potting materials. This paper reviews the state of the art in foam materials and describes experimental work to fabricate low density, high shear strength foam which can withstand temperatures from -220 C to 220 C. Commercially available polymer foams exhibit a wide range of physical properties. Some with densities as low as 0.066 g/cc are capable of co-curing at temperatures as high as 182 C. Rohacell foams can be resin transfer molded at temperatures up to 180 C. They have moduli of elasticity of 0.19 MPa, tensile strengths of 3.7 Mpa and compressive strengths of 3.6 MPa. The Rohacell foams cannot withstand liquid hydrogen temperatures, however Imi-Tech markets Solimide (trademark) foams which withstand temperatures from -250 C to 200 C, but they do not have the required structural integrity. The research activity at NASA Langley Research Center focuses on using chemical blowing agents to produce polyimide thermoplastic foams capable of meeting the above performance requirements. The combination of blowing agents that decompose at the minimum melt viscosity temperature together with plasticizers to lower the viscosity has been used to produce foams by both extrusion and oven heating. The foams produced exhibit good environmental stability while maintaining structural properties.

Improvement of the mechanical properties of reinforced aluminum foam samples

NASA Astrophysics Data System (ADS)

Formisano, A.; Barone, A.; Carrino, L.; De Fazio, D.; Langella, A.; Viscusi, A.; Durante, M.

2018-05-01

Closed-cell aluminum foam has attracted increasing attention due to its very interesting properties, thanks to which it is expected to be used as both structural and functional material. A research challenge is the improvement of the mechanical properties of foam-based structures adopting a reinforced approach that does not compromise their lightness. Consequently, the aim of this research is the fabrication of enhanced aluminum foam samples without significantly increasing their original weight. In this regard, cylindrical samples with a core of closed-cell aluminum foam and a skin of fabrics and grids of different materials were fabricated in a one step process and were mechanically characterized, in order to investigate their behaviour and to compare their mechanical properties to the ones of the traditional foam.

A combined NDE/FEA approach to evaluate the structural response of a metal foam

NASA Astrophysics Data System (ADS)

Ghosn, Louis J.; Abdul-Aziz, Ali; Raj, Sai V.; Rauser, Richard W.

2007-04-01

Metal foams are expected to find use in structural applications where weight is of particular concern, such as space vehicles, rotorcraft blades, car bodies or portable electronic devices. The obvious structural application of metal foam is for light weight sandwich panels, made up of thin solid face sheets and a metallic foam core. The stiffness of the sandwich structure is increased by separating the two face sheets by a light weight metal foam core. The resulting high-stiffness structure is lighter than that constructed only out of the solid metal material. Since the face sheets carry the applied in-plane and bending loads, the sandwich architecture is a viable engineering concept. However, the metal foam core must resist transverse shear loads and compressive loads while remaining integral with the face sheets. Challenges relating to the fabrication and testing of these metal foam panels remain due to some mechanical properties falling short of their theoretical potential. Theoretical mechanical properties are based on an idealized foam microstructure and assumed cell geometry. But the actual testing is performed on as fabricated foam microstructure. Hence in this study, a detailed three dimensional foam structure is generated using series of 2D Computer Tomography (CT) scans. The series of the 2D images are assembled to construct a high precision solid model capturing all the fine details within the metal foam as detected by the CT scanning technique. Moreover, a finite element analysis is then performed on as fabricated metal foam microstructures, to calculate the foam mechanical properties with the idealized theory. The metal foam material is an aerospace grade precipitation hardened 17-4 PH stainless steel with high strength and high toughness. Tensile and compressive mechanical properties are deduced from the FEA model and compared with the theoretical values for three different foam densities. The combined NDE/FEA provided insight in the variability of the mechanical properties compared to idealized theory.

Thermal aging of traditional and additively manufactured foams: analysis by time-temperature-superposition, constitutive, and finite-element models

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maiti, A.; Weisgraber, T. H.; Small, W.

Cellular solids or foams are a very important class of materials with diverse applications ranging from thermal insulation and shock absorbing support cushions, to light-weight structural and floatation components, and constitute crucial components in a large number of industries including automotive, aerospace, electronics, marine, biomedical, packaging, and defense. In many of these applications the foam material is subjected to long periods of continuous stress, which can, over time, lead to a permanent change in structure and a degradation in performance. In this report we summarize our modeling efforts to date on polysiloxane foam materials that form an important component inmore » our systems. Aging of the materials was characterized by two measured quantities, i.e., compression set and load retention. Results of accelerated aging experiments were analyzed by an automated time-temperaturesuperposition (TTS) approach, which creates a master curve that can be used for long-term predictions (over decades) under ambient conditions. When comparing such master curves for traditional (stochastic) foams with those for recently 3D-printed (i.e., additively manufactured, or AM) foams, it became clear that AM foams have superior aging behavior. To gain deeper understanding, we imaged the microstructure of both foams using X-ray computed tomography, and performed finite-element analysis of the mechanical response within these microstructures. This indicates a wider stress variation in the stochastic foam with points of more extreme local stress as compared to the 3D printed material.« less

Porous Foam Based Wick Structures for Loop Heat Pipes

NASA Technical Reports Server (NTRS)

Silk, Eric A.

2012-01-01

As part of an effort to identify cost efficient fabrication techniques for Loop Heat Pipe (LHP) construction, NASA Goddard Space Flight Center's Cryogenics and Fluids Branch collaborated with the U.S. Naval Academy s Aerospace Engineering Department in Spring 2012 to investigate the viability of carbon foam as a wick material within LHPs. The carbon foam was manufactured by ERG Aerospace and machined to geometric specifications at the U.S. Naval Academy s Materials, Mechanics and Structures Machine Shop. NASA GSFC s Fractal Loop Heat Pipe (developed under SBIR contract #NAS5-02112) was used as the validation LHP platform. In a horizontal orientation, the FLHP system demonstrated a heat flux of 75 Watts per square centimeter with deionized water as the working fluid. Also, no failed start-ups occurred during the 6 week performance testing period. The success of this study validated that foam can be used as a wick structure. Furthermore, given the COTS status of foam materials this study is one more step towards development of a low cost LHP.

Recycling of Aluminum Alloy with Dimox and Rheocasting Functionalize High Performance Structural Foam Composite

NASA Astrophysics Data System (ADS)

Rabeeh, Bakr Mohamed

Great efforts aiming towards the synthesis and the development of structural composite materials. Direct metal oxidation, DIMOX introduced for hybrid composite processing. However, oxidation temperatures around 1100°C lead to the formation of porous ceramic materials. To utilize this porosity intentionally for foam production, a new approach based on synergetic effect of alloying elements, DIMOX and semisolid (rheocsting) processing is developed. A semisolid reaction, rheocasting is introduced to control porosity shape and size. Aluminum alloy 6xxx (automobile scrap pistons) is recycled for this objective and DIMOX at 1100°C for 30 min, then rheocasting, at 750°C for 30 minutes. The effect of α-Fe powder, Mg powder, and Boric acid powder established for the objective of a hybrid structural metal matrix composite in bulk foam matrix. The kinetic of formation of hybrid metal matrix foam composite is introduced. Microstructural and mechanical characterization established for high performance Aluminum foam hybrid composite materials.

Hypervelocity Impact Evaluation of Metal Foam Core Sandwich Structures

NASA Technical Reports Server (NTRS)

Yasensky, John; Christiansen, Eric L.

2007-01-01

A series of hypervelocity impact (HVI) tests were conducted by the NASA Johnson Space Center (JSC) Hypervelocity Impact Technology Facility (HITF) [1], building 267 (Houston, Texas) between January 2003 and December 2005 to test the HVI performance of metal foams, as compared to the metal honeycomb panels currently in service. The HITF testing was conducted at the NASA JSC White Sands Testing Facility (WSTF) at Las Cruces, New Mexico. Eric L. Christiansen, Ph.D., and NASA Lead for Micro-Meteoroid Orbital Debris (MMOD) Protection requested these hypervelocity impact tests as part of shielding research conducted for the JSC Center Director Discretionary Fund (CDDF) project. The structure tested is a metal foam sandwich structure; a metal foam core between two metal facesheets. Aluminum and Titanium metals were tested for foam sandwich and honeycomb sandwich structures. Aluminum honeycomb core material is currently used in Orbiter Vehicle (OV) radiator panels and in other places in space structures. It has many desirable characteristics and performs well by many measures, especially when normalized by density. Aluminum honeycomb does not perform well in Hypervelocity Impact (HVI) Testing. This is a concern, as honeycomb panels are often exposed to space environments, and take on the role of Micrometeoroid / Orbital Debris (MMOD) shielding. Therefore, information on possible replacement core materials which perform adequately in all necessary functions of the material would be useful. In this report, HVI data is gathered for these two core materials in certain configurations and compared to gain understanding of the metal foam HVI performance.

Non-flammable polyimide materials for aircraft and spacecraft applications

NASA Technical Reports Server (NTRS)

Gagliani, J.; Supkis, D. E.

1979-01-01

Recent developments in polyimide chemistry show promise for producing materials with very low flammability and a wide range of mechanical properties. Polyimide foams can be synthesized to provide fire safety without detectable formation of smoke or toxic byproducts below 204 C (400 F), thus avoiding an environment which is lethal to human habitation. This work has been and is currently being performed under development programs, the objective of which is to provide cost effective processes for producing thermally stable, polyimide flexible resilient foams, thermal-acoustical insulating materials, rigid low density foam panels, and high strength foam structures. The chemical and physical properties demonstrated by these materials represent a technological advancement in the art of thermally stable polyimide polymers which are expected to insure fire protection of structures and components used in air transportation and space exploration. Data compiled to date on thermal, physical and functional properties of these materials are presented.

Foam For Filtering

NASA Technical Reports Server (NTRS)

1978-01-01

Like nature's honeycomb, foam is a structure of many-sided cells, apparently solid but actually only three percent material and 97 percent air. Foam is made by a heat-producing chemical reaction which expands a plastic material in a manner somewhat akin to the heat-induced rising of a loaf of bread. The resulting structure of interconnected cells is flexible yet strong and extremely versatile in applicati6n. Foam can, for example, be a sound absorber in one form, while in another it allows sound to pass through it. It can be a very soft powder puff material and at the same time a highly abrasive scrubber. A sampling of foam uses includes stereo speaker grilles, applying postage meter ink, filtering lawnmower carburetor air; deadening noise in trucks and tractors, applying cosmetics, releasing fabric softener and antistatic agents in home clothes dryers, painting, filtering factory heating and ventilating systems, shining shoes, polishing cars, sponge-mopping floors, acting as pre-operative surgical scrubbers-the list is virtually limitless. The process by which foam is made produces "windows," thin plastic membranes connecting the cell walls. Windowed foam is used in many applications but for certain others-filtering, for example-it is desirable to have a completely open network. Scott Paper Company's Foam Division, Chester, Pennsylvania, improved a patented method of "removing the windows," to create an open structure that affords special utility in filtering applications. NASA technology contributed to Scott's improvement.

Fire-retardant foams

NASA Technical Reports Server (NTRS)

Gagliani, J.

1978-01-01

Family of polyimide resins are being developed as foams with exceptional fire-retardant properties. Foams are potentially useful for seat cushions in aircraft and ground vehicles and for applications such as home furnishings and building-construction materials. Basic formulations can be modified with reinforcing fibers or fillers to produce celular materials for variety of applications. By selecting reactants, polymer structure can be modified to give foams with properties ranging from high resiliency and flexibility to brittleness and rigidity.

Characterization of Polyimide Foams for Ultra-Lightweight Space Structures

NASA Technical Reports Server (NTRS)

Meador, Michael (Technical Monitor); Hillman, Keithan; Veazie, David R.

2003-01-01

Ultra-lightweight materials have played a significant role in nearly every area of human activity ranging from magnetic tapes and artificial organs to atmospheric balloons and space inflatables. The application range of ultra-lightweight materials in past decades has expanded dramatically due to their unsurpassed efficiency in terms of low weight and high compliance properties. A new generation of ultra-lightweight materials involving advanced polymeric materials, such as TEEK (TM) polyimide foams, is beginning to emerge to produce novel performance from ultra-lightweight systems for space applications. As a result, they require that special conditions be fulfilled to ensure adequate structural performance, shape retention, and thermal stability. It is therefore important and essential to develop methodologies for predicting the complex properties of ultra-lightweight foams. To support NASA programs such as the Reusable Launch Vehicle (RLV), Clark Atlanta University, along with SORDAL, Inc., has initiated projects for commercial process development of polyimide foams for the proposed cryogenic tank integrated structure (see figure 1). Fabrication and characterization of high temperature, advanced aerospace-grade polyimide foams and filled foam sandwich composites for specified lifetimes in NASA space applications, as well as quantifying the lifetime of components, are immensely attractive goals. In order to improve the development, durability, safety, and life cycle performance of ultra-lightweight polymeric foams, test methods for the properties are constant concerns in terms of timeliness, reliability, and cost. A major challenge is to identify the mechanisms of failures (i.e., core failure, interfacial debonding, and crack development) that are reflected in the measured properties. The long-term goal of the this research is to develop the tools and capabilities necessary to successfully engineer ultra-lightweight polymeric foams. The desire is to reduce density at the material and structural levels, while at the same time maintaining or increasing mechanical and other properties.

Fabrication of cellular materials

NASA Astrophysics Data System (ADS)

Prud'homme, Robert K.; Aksay, Ilhan A.; Garg, Rajeev

1996-02-01

Nature uses cellular materials in applications requiring strength while, simultaneously, minimizing raw materials requirements. Minimizing raw materials is efficient both in terms of the energy expended by the organism to synthesize the structure and in terms of the strength- to-weight ratio of the structure. Wood is the most obvious example of cellular bio-materials, and it is the focus of other presentations in this symposium. The lightweight bone structure of birds is another excellent example where weight is a key criterion. The anchoring foot of the common muscle [Mytilus edulis] whereby it attaches itself to objects is a further example of a biological system that uses a foam to fill space and yet conserve on raw materials. In the case of the muscle the foam is water filled and the foot structure distributes stress over a larger area so that the strength of the byssal thread from which it is suspended is matched to the strength of interfacial attachment of the foot to a substrate. In these examples the synthesis and fabrication of the cellular material is directed by intercellular, genetically coded, biochemical reactions. The resulting cell sizes are microns in scale. Cellular materials at the next larger scale are created by organisms at the next higher level of integration. For example an African tree frog lays her eggs in a gas/fluid foam sack she builds on a branch overhanging a pond. The outside of the foam sack hardens in the sun and prevents water evaporation. The foam structure minimizes the amount of fluid that needs to be incorporated into the sack and minimizes its weight. However, as far as the developing eggs are concerned, they are in an aqueous medium, i.e. the continuous fluid phase of the foam. After precisely six days the eggs hatch, and the solidified outer wall re-liquefies and dumps the emerging tadpoles into the pond below. The bee honeycomb is an example of a cellular material with exquisite periodicity at millimeter length scales. The cellular structure provides strength through geometric regularity and functions as both honey storage vessels and incubators.

Application of Video Image Correlation Techniques to the Space Shuttle External Tank Foam Materials

NASA Technical Reports Server (NTRS)

Hilburger, Mark W.; Nemeth, Michael P.

2005-01-01

Results that illustrate the use of a video-image-correlation-based displacement and strain measurement system to assess the effects of material nonuniformities on the behavior of the sprayed-on foam insulation (SOFI) used for the thermal protection system on the Space Shuttle External Tank are presented. Standard structural verification specimens for the SOFI material with and without cracks and subjected to mechanical or thermal loading conditions were tested. Measured full-field displacements and strains are presented for selected loading conditions to illustrate the behavior of the foam and the viability of the measurement technology. The results indicate that significant strain localization can occur in the foam because of material nonuniformities. In particular, elongated cells in the foam can interact with other geometric or material discontinuities in the foam and develop large-magnitude localized strain concentrations that likely initiate failures. Furthermore, some of the results suggest that continuum mechanics and linear elastic fracture mechanics might not adequately represent the physical behavior of the foam, and failure predictions based on homogeneous linear material models are likely to be inadequate.

Application of Video Image Correlation Techniques to the Space Shuttle External Tank Foam Materials

NASA Technical Reports Server (NTRS)

Hilburger, Mark W.; Nemeth, Michael P.

2006-01-01

Results that illustrate the use of a video-image-correlation-based displacement and strain measurement system to assess the effects of material nonuniformities on the behavior of the sprayed-on foam insulation (SOFI) used for the thermal protection system on the Space Shuttle External Tank are presented. Standard structural verification specimens for the SOFI material with and without cracks and subjected to mechanical or thermal loading conditions were tested. Measured full-field displacements and strains are presented for selected loading conditions to illustrate the behavior of the foam and the viability of the measurement technology. The results indicate that significant strain localization can occur in the foam because of material nonuniformities. In particular, elongated cells in the foam can interact with other geometric or material discontinuities in the foam and develop large-magnitude localized strain concentrations that likely initiate failures. Furthermore, some of the results suggest that continuum mechanics and linear elastic fracture mechanics might not adequately represent the physical behavior of the foam, and failure predictions based on homogeneous linear material models are likely to be inadequate.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rao, Rekha R.; Celina, Mathias C.; Giron, Nicholas Henry

We are developing computational models to help understand manufacturing processes, final properties and aging of structural foam, polyurethane PMDI. Th e resulting model predictions of density and cure gradients from the manufacturing process will be used as input to foam heat transfer and mechanical models. BKC 44306 PMDI-10 and BKC 44307 PMDI-18 are the most prevalent foams used in structural parts. Experiments needed to parameterize models of the reaction kinetics and the equations of motion during the foam blowing stages were described for BKC 44306 PMDI-10 in the first of this report series (Mondy et al. 2014). BKC 44307 PMDI-18more » is a new foam that will be used to make relatively dense structural supports via over packing. It uses a different catalyst than those in the BKC 44306 family of foams; hence, we expect that the reaction kineti cs models must be modified. Here we detail the experiments needed to characteriz e the reaction kinetics of BKC 44307 PMDI-18 and suggest parameters for the model based on these experiments. In additi on, the second part of this report describes data taken to provide input to the preliminary nonlinear visco elastic structural response model developed for BKC 44306 PMDI-10 foam. We show that the standard cu re schedule used by KCP does not fully cure the material, and, upon temperature elevation above 150°C, oxidation or decomposition reactions occur that alter the composition of the foam. These findings suggest that achieving a fully cured foam part with this formulation may be not be possible through therma l curing. As such, visco elastic characterization procedures developed for curing thermosets can provide only approximate material properties, since the state of the material continuously evolves during tests.« less

Superalloy Foams for Aeroshell Applications

NASA Technical Reports Server (NTRS)

Gayda, John; Padula, Santo, II

2001-01-01

Current thermal protection systems for reentry from space, such as that employed on the space shuttle, rely on ceramic tiles with ultra-low conductivity. These materials provide excellent thermal protection but are extremely fragile, easily degraded by environmental attack, and carry no structural loads. Future thermal protection systems being proposed in NASAs MITAS Program will attempt to combine thermal protection with improved durability and structural capability without significant increases in vehicle weight. This may be accomplished by combining several materials in a layered structure to obtain the desired function for aeroshell applications. One class of materials being considered for inclusion in this concept are high temperature metal foam. The objective of this paper was to fabricate low density, superalloy foams and conduct limited testing to evaluate their thermal and structural capabilities. Superalloys were chosen for evaluation as they possesses good strength and excellent environmental endurance over a wide range of temperatures. Utilizing superalloys as low density foams, with porosity contents greater than 90%, minimizes weight and thermal conductivity.

Design, characterization and modeling of biobased acoustic foams

NASA Astrophysics Data System (ADS)

Ghaffari Mosanenzadeh, Shahrzad

Polymeric open cell foams are widely used as sound absorbers in sectors such as automobile, aerospace, transportation and building industries, yet there is a need to improve sound absorption of these foams through understanding the relation between cell morphology and acoustic properties of porous material. Due to complicated microscopic structure of open cell foams, investigating the relation between foam morphology and acoustic properties is rather intricate and still an open problem in the field. The focus of this research is to design and develop biobased open cell foams for acoustic applications to replace conventional petrochemical based foams as well as investigating the link between cell morphology and macroscopic properties of open cell porous structures. To achieve these objectives, two industrially produced biomaterials, polylactide (PLA) and polyhydroxyalkanoate (PHA) and their composites were examined and highly porous biobased foams were fabricated by particulate leaching and compression molding. Acoustic absorption capability of these foams was enhanced utilizing the effect of co-continuous blends to form a bimodal porous structure. To tailor mechanical and acoustic properties of biobased foams, blends of PLA and PHA were studied to reach the desired mechanical and viscoelastic properties. To enhance acoustic properties of porous medium for having a broad band absorption effect, cell structure must be appropriately graded. Such porous structures with microstructural gradation are called Functionally Graded Materials (FGM). A novel graded foam structure was designed with superior sound absorption to demonstrate the effect of cell arrangement on performance of acoustic fixtures. Acoustic measurements were performed in a two microphone impedance tube and acoustic theory of Johnson-Champoux-Allard was applied to the fabricated foams to determine micro cellular properties such as tortuosity, viscous and thermal lengths from sound absorption impedance tube measurements using an inverse technique. As the next step towards in depth understanding of the relation between cell morphology and sound absorption of open cell foams, a semi-analytical model was developed to account for the effect of micro cellular properties such as cell wall thickness and reticulation rate on overall macroscopic and structural properties. Developed model provides the tools to optimize the porous structure and enhance sound absorption capability.

Pitch-based carbon foam and composites

DOEpatents

Klett, James W.

2001-01-01

A process for producing carbon foam or a composite is disclosed which obviates the need for conventional oxidative stabilization. The process employs mesophase or isotropic pitch and a simplified process using a single mold. The foam has a relatively uniform distribution of pore sizes and a highly aligned graphic structure in the struts. The foam material can be made into a composite which is useful in high temperature sandwich panels for both thermal and structural applications.

Pitch-based carbon foam and composites

DOEpatents

Klett, James W.

2003-12-16

A process for producing carbon foam or a composite is disclosed which obviates the need for conventional oxidative stabilization. The process employs mesophase or isotropic pitch and a simplified process using a single mold. The foam has a relatively uniform distribution of pore sizes and a highly aligned graphic structure in the struts. The foam material can be made into a composite which is useful in high temperature sandwich panels for both thermal and structural applications.

Pitch-based carbon foam and composites

DOEpatents

Klett, James W.

2003-12-02

A process for producing carbon foam or a composite is disclosed which obviates the need for conventional oxidative stabilization. The process employs mesophase or isotropic pitch and a simplified process using a single mold. The foam has a relatively uniform distribution of pore sizes and a highly aligned graphic structure in the struts. The foam material can be made into a composite which is useful in high temperature sandwich panels for both thermal and structural applications.

Pitch-based carbon foam and composites

DOEpatents

Klett, James W.

2002-01-01

A process for producing carbon foam or a composite is disclosed which obviates the need for conventional oxidative stabilization. The process employs mesophase or isotropic pitch and a simplified process using a single mold. The foam has a relatively uniform distribution of pore sizes and a highly aligned graphic structure in the struts. The foam material can be made into a composite which is useful in high temperature sandwich panels for both thermal and structural applications.

Formation of 3D graphene foams on soft templated metal monoliths

NASA Astrophysics Data System (ADS)

Tynan, Michael K.; Johnson, David W.; Dobson, Ben P.; Coleman, Karl S.

2016-07-01

Graphene foams are leading contenders as frameworks for polymer thermosets, filtration/pollution control and for use as an electrode material in energy storage devices, taking advantage of graphene's high electrical conductivity and the porous structure of the foam. Here we demonstrate a simple synthesis of a macroporous 3D graphene material templated from a dextran/metal salt gel, where the metal was cobalt, nickel, copper, and iron. The gel was annealed to form a metal oxide foam prior to a methane chemical vapour deposition (CVD). Cobalt metal gels were shown to afford the highest quality material as determined by electron microscopy (SEM and TEM) and Raman spectroscopy.Graphene foams are leading contenders as frameworks for polymer thermosets, filtration/pollution control and for use as an electrode material in energy storage devices, taking advantage of graphene's high electrical conductivity and the porous structure of the foam. Here we demonstrate a simple synthesis of a macroporous 3D graphene material templated from a dextran/metal salt gel, where the metal was cobalt, nickel, copper, and iron. The gel was annealed to form a metal oxide foam prior to a methane chemical vapour deposition (CVD). Cobalt metal gels were shown to afford the highest quality material as determined by electron microscopy (SEM and TEM) and Raman spectroscopy. Electronic supplementary information (ESI) available: Raman, EDX, PXRD, TGA, electrical conductivity data and SEM. See DOI: 10.1039/c6nr02455f

Centrifugation-Assisted Fog-Collecting Abilities of Metal-Foam Structures with Different Surface Wettabilities.

PubMed

Ji, Keju; Zhang, Jun; Chen, Jia; Meng, Guiyun; Ding, Yafei; Dai, Zhendong

2016-04-20

The collection of water from fog is a simple and sustainable means of obtaining freshwater for human and animal consumption. Herein, we address the use of metal foam in fog collection and present a novel fog-collecting device fabricated from copper foam. This device, which can also be used in other liquid-gas separation applications, is a 3D extension of biologically inspired 1D and 2D materials. The network structure of the 3D material effectively increased the contact area and interaction time of the skeleton structure and fog compared to those of traditional 2D fog-collecting materials. The main aspects investigated in this study were the influences of the inertial centrifugal force generated by rotating the metal-foam samples and the use of samples with different surface wettabilities on the fog-collecting performance. Superhydrophilic and superhydrophobic samples were found to have higher collection efficiencies at low and high rotational speeds, respectively, and a maximum efficiency of 86% was achieved for superhydrophobic copper foam (20 pores per inch) rotated at 1500 rpm.

The performance of lightweight plastic foams developed for fire safety

NASA Technical Reports Server (NTRS)

Fish, R. H.

1971-01-01

The use of a low density, polyurethane based foam to suppress a fire and to provide protection for the structure of an aircraft or spacecraft is discussed. The mechanism by which foams provide protection from heat and create a nonflammable surface is described. Various materials and their application to specific types of structures are examined.

Development and validation of cryogenic foam insulation for LH2 subsonic transports

NASA Technical Reports Server (NTRS)

Anthony, F. M.; Colt, J. Z.; Helenbrook, R. G.

1981-01-01

Fourteen foam insulation specimens were tested. Some were plain foam while others contained flame retardants, chopped fiberglass reinforcement and/or vapor barriers. The thermal performance of the insulation was determined by measuring the rate at which LH2 boiled from an aluminum tank insulated with the test material. The test specimens were approximately 50 mm (2 in.) thick. They were structurally scaled so that the test cycle would duplicate the maximum thermal stresses predicted for the thicker insulation of an aircraft liquid hydrogen fuel tank during a typical subsonic flight. The simulated flight cycle of approximately 10 minutes duration heated the other insulation surface to 316 K (110 F) and cooled it to 226 K (20 F) while the inner insulation surface remained at liquid hydrogen temperature of 20 K (-423 F). Two urethane foam insulations exceeded the initial life goal of 2400 simulated flight cycles and sustained 4400 cycles with only minor damage. The addition of fiberglass reinforcement of flame retardant materials to an insulation degraded thermal performance and/or the life of the foam material. Installation of vapor barriers enhanced the structural integrity of the material but did not improve thermal performance. All of the foams tested were available materials; none were developed specifically for LH2 service.

Graphene oxide foams and their excellent adsorption ability for acetone gas

DOE Office of Scientific and Technical Information (OSTI.GOV)

He, Yongqiang; School of Science, Tianjin University, Tianjin 300072; Zhang, Nana

2013-09-01

Graphical abstract: - Highlights: • GO and RGO foams were prepared using a simple and green method, unidirectional freeze-drying. • The porous structure of the foams can be adjusted by changing GO concentrations. • GO and RGO foams show good adsorption efficiency for acetone gas. - Abstract: Graphene oxide (GO) and reduced graphene oxide (RGO) foams were prepared using a unidirectional freeze-drying method. These porous carbon materials were characterized by thermal gravimetric analysis, differential scanning calorimetry, X-ray photoelectron spectroscopy and scanning electron microscopy. The adsorption behavior of the two kinds of foams for acetone was studied. The result showed thatmore » the saturated adsorption efficiency of the GO foams was over 100%, and was higher than that of RGO foams and other carbon materials.« less

Fabrication of nickel-foam-supported layered zinc-cobalt hydroxide nanoflakes for high electrochemical performance in supercapacitors.

PubMed

Yuan, Peng; Zhang, Ning; Zhang, Dan; Liu, Tao; Chen, Limiao; Liu, Xiaohe; Ma, Renzhi; Qiu, Guanzhou

2014-10-04

Nickel foam supported Zn-Co hydroxide nanoflakes were fabricated by a facile solvothermal method. Benefited from the unique structure of Zn-Co hydroxide nanoflakes on a nickel foam substrate, the as prepared materials exhibited an excellent specific capacitance of 901 F g(-1) at 5 A g(-1) and remarkable cycling stability as electrode materials in supercapacitors.

Shock Tube Test for Energy Absorbing Materials

DTIC Science & Technology

2013-09-13

rigid and lightweight foam material with a closed-cell structure, and a very high strength-to-weight ratio (7). It is commonly used as a sandwich...including application in helmet liners (8). Zorbium™ is the viscoelastic polyurethane foam used in military helmet suspension system pads (9). 8...viscoelastic polyurethane foam which shows strain rate dependent behavior when compressed. This is displayed by the significant difference in response

Studies of Sound Absorption by and Transmission Through Layers of Elastic Noise Control Foams: Finite Element Modeling and Effects of Anisotropy

NASA Astrophysics Data System (ADS)

Kang, Yeon June

In this thesis an elastic-absorption finite element model of isotropic elastic porous noise control materials is first presented as a means of investigating the effects of finite dimension and edge constraints on the sound absorption by, and transmission through, layers of acoustical foams. Methods for coupling foam finite elements with conventional acoustic and structural finite elements are also described. The foam finite element model based on the Biot theory allows for the simultaneous propagation of the three types of waves known to exist in an elastic porous material. Various sets of boundary conditions appropriate for modeling open, membrane-sealed and panel-bonded foam surfaces are formulated and described. Good agreement was achieved when finite element predictions were compared with previously established analytical results for the plane wave absorption coefficient and transmission loss in the case of wave propagation both in foam-filled waveguides and through foam-lined double panel structures of infinite lateral extent. The primary effect of the edge constraints of a foam layer was found to be an acoustical stiffening of the foam. Constraining the ends of the facing panels in foam-lined double panel systems was also found to increase the sound transmission loss significantly in the low frequency range. In addition, a theoretical multi-dimensional model for wave propagation in anisotropic elastic porous materials was developed to study the effect of anisotropy on the sound transmission of foam-lined noise control treatments. The predictions of the theoretical anisotropic model have been compared with experimental measurements for the random incidence sound transmission through double panel structure lined with polyimide foam. The predictions were made by using the measured and estimated macroscopic physical parameters of polyimide foam samples which were known to be anisotropic. It has been found that the macroscopic physical parameters in the direction normal to the face of foam layer play the principal role in determining the acoustical behavior of polyimide foam layers, although more satisfactory agreement between experimental measurements and theoretical predictions of transmission loss is obtained when the anisotropic properties are allowed in the model.

Process for making carbon foam

DOEpatents

Klett, James W.

2000-01-01

The process obviates the need for conventional oxidative stabilization. The process employs mesophase or isotropic pitch and a simplified process using a single mold. The foam has a relatively uniform distribution of pore sizes and a highly aligned graphic structure in the struts. The foam material can be made into a composite which is useful in high temperature sandwich panels for both thermal and structural applications.

A novel and facile strategy for highly flame retardant polymer foam composite materials: Transforming silicone resin coating into silica self-extinguishing layer.

PubMed

Wu, Qian; Zhang, Qian; Zhao, Li; Li, Shi-Neng; Wu, Lian-Bin; Jiang, Jian-Xiong; Tang, Long-Cheng

2017-08-15

In this study, a novel strategy was developed to fabricate highly flame retardant polymer foam composite materials coated by synthesized silicone resin (SiR) polymer via a facile dip-coating processing. Applying the SiR polymer coating, the mechanical property and thermal stability of SiR-coated polymer foam (PSiR) composites are greatly enhanced without significantly altering their structure and morphology. The minimum oxygen concentration to support the combustion of foam materials is greatly increased, i.e. from LOI 14.6% for pure foam to LOI 26-29% for the PSiR composites studied. Especially, adjusting pendant group to SiOSi group ratio (R/Si ratio) of SiRs produces highly flame retardant PSiR composites with low smoke toxicity. Cone calorimetry results demonstrate that 44-68% reduction in the peak heat release rate for the PSiR composites containing different R/Si ratios over pure foam is achieved by the presence of appropriate SiR coating. Digital and SEM images of post-burn chars indicate that the SiR polymer coating can be transformed into silica self-extinguishing porous layer as effective inorganic barrier effect, thus preserving the polymer foam structure from fire. Our results show that the SiR dip-coating technique is a promising strategy for producing flame retardant polymer foam composite materials with improved mechanical properties. Copyright © 2017 Elsevier B.V. All rights reserved.

3D-Printing ‘Smarter’ Energy Absorbing Materials

ScienceCinema

Duoss, Eric

2018-01-16

Foams are, by nature, disordered materials studded with air pockets of varying sizes. Lack of control over the material’s architecture at the micrometer or nanometer scale can make it difficult to adjust the foam’s basic properties. But Eric Duoss and a team of Livermore researchers are using additive manufacturing to develop “smarter” silicone cushions. By architecting the structure at the micro scale, they are able to control macro-scale properties previously unachievable with foam materials.

Macro-cellular silica foams: synthesis during the natural creaming process of an oil-in-water emulsion.

PubMed

Sen, T; Tiddy, G J T; Casci, J L; Anderson, M W

2003-09-07

The room-temperature synthesis of a macro-mesoporous silica material during the natural creaming process of an oil-in-water emulsion is reported. The material has 3-dimensional interconnected macropores with a strut-like structure similar to meso-cellular silica foams with mesoporous walls of worm-hole structure. The material has very high surface area (approximately 800 m2 g(-1)) with narrow mesopore size distribution.

Characterization of synthetic foam structures used to manufacture artificial vertebral trabecular bone.

PubMed

Fürst, David; Senck, Sascha; Hollensteiner, Marianne; Esterer, Benjamin; Augat, Peter; Eckstein, Felix; Schrempf, Andreas

2017-07-01

Artificial materials reflecting the mechanical properties of human bone are essential for valid and reliable implant testing and design. They also are of great benefit for realistic simulation of surgical procedures. The objective of this study was therefore to characterize two groups of self-developed synthetic foam structures by static compressive testing and by microcomputed tomography. Two mineral fillers and varying amounts of a blowing agent were used to create different expansion behavior of the synthetic open-cell foams. The resulting compressive and morphometric properties thus differed within and also slightly between both groups. Apart from the structural anisotropy, the compressive and morphometric properties of the synthetic foam materials were shown to mirror the respective characteristics of human vertebral trabecular bone in good approximation. In conclusion, the artificial materials created can be used to manufacture valid synthetic bones for surgical training. Further, they provide novel possibilities for studying the relationship between trabecular bone microstructure and biomechanical properties. Copyright © 2017 Elsevier B.V. All rights reserved.

Irradiation response and stability of nanoporous materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fu, Engang; Wang, Yongqiang; Serrano De Caro, Magdalena

2012-08-28

Nanoporous materials consist of a regular organic or inorganic framework supporting a regular, porous structure. Pores are by definition roughly in the nanometre range, that is between 0.2 nm and 100 nm. Nanoporous materials can be subdivided into 3 categories (IUPAC): (1) Microporous materials - 0.2-2 nm; (2) Mesoporous materials - 2-50 nm; and (3) Macroporous materials - 50-1000 nm. np-Au foams were successfully synthesized by de-alloying process. np-Au foams remain porous structure after Ne ion irradiation to 1 dpa. Stacking Fault Tetrahedra (SFTs) were observed in RT irradiated np-Au foams under the highest and intermediate fluxes, but not undermore » the lowest flux. SFTs were not observed in LNT irradiated np-Au foams under all fluxes. The vacancy diffusivity in Au at RT is high enough so that the vacancies have enough time to agglomerate and then collapse to form SFTs. The high ion flux creates more damage per unit time; vacancies don't have enough time to diffuse or recombine. As a result, SFTs were formed at high ion fluxes.« less

An experimental investigation of using carbon foam-PCM-MWCNTs composite materials for thermal management of electronic devices under pulsed power modes

NASA Astrophysics Data System (ADS)

Alshaer, W. G.; Rady, M. A.; Nada, S. A.; Palomo Del Barrio, Elena; Sommier, Alain

2017-02-01

The present article reports on a detailed experimental investigation of using carbon foam-PCM-MWCNTs composite materials for thermal management (TM) of electronic devices subjected to pulsed power. The TM module was fabricated by infiltrating paraffin wax (RT65) as a phase change material (PCM) and multi walled carbon nanotubes (MWCNTs) as a thermal conductivity enhancer in a carbon foam as a base structure. Two carbon foam materials of low and high values of thermal conductivities, CF20 and KL1-250 (3.1 and 40 W/m K), were tested as a base structure for the TM modules. Tests were conducted at different power intensities and power cycling/loading modes. Results showed that for all power varying modes and all carbon foams, the infiltration of RT65 into carbon foam reduces the temperature of TM module and results in damping the temperature spikes height. Infiltration of MWCNTS into RT65 further improves the effectiveness of TM module. Temperature damping was more pronounced in stand-alone pulsed power cycles as compared to pulsed power spikes modes. The effectiveness of inclusion of RT65 and RT65/MWCNTs in damping the temperature spikes height is remarkable in TM modules based on KL1-250 as compared to CF-20.

Cellular structures with interconnected microchannels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shaefer, Robert Shahram; Ghoniem, Nasr M.; Williams, Brian

A method for fabricating a cellular tritium breeder component includes obtaining a reticulated carbon foam skeleton comprising a network of interconnected ligaments. The foam skeleton is then melt-infiltrated with a tritium breeder material, for example, lithium zirconate or lithium titanate. The foam skeleton is then removed to define a cellular breeder component having a network of interconnected tritium purge channels. In an embodiment the ligaments of the foam skeleton are enlarged by adding carbon using chemical vapor infiltration (CVI) prior to melt-infiltration. In an embodiment the foam skeleton is coated with a refractory material, for example, tungsten, prior to meltmore » infiltration.« less

Pore Size Control in Aluminium Foam by Standardizing Bubble Rise Velocity and Melt Viscosity

NASA Astrophysics Data System (ADS)

Avinash, G.; Harika, V.; Sandeepika, Ch; Gupta, N.

2018-03-01

In recent years, aluminium foams have found use in a wide range of applications. The properties of these foams, as good structural strength with light weight have made them as a promising structural material for aerospace industry. Foaming techniques (direct and indirect) are used to produce these foams. Direct foaming involves blowing of gas to create gas bubbles in the melt whereas indirect foaming technique uses blowing agents as metallic hydrides, which create hydrogen bubbles. Porosity and its distribution in foams directly affect its properties. This demands for more theoretical studies, to control such cellular structure and hence properties. In present work, we have studied the effect of gas bubble rise velocity and melt viscosity, on pore size and its distribution in aluminium foam. A 15 PPI aluminium foam, prepared using indirect foaming technique having porosity ~86 % was used for study. In order to obtain metal foam, the bubble must not escape from the melt and should get entrapped during solidification. Our calculations suggest that bubble rise velocity and melt viscosity are responsible for vertical displacement of bubble in the melt. It is observed that melt viscosity opposes bubble rise velocity and help the bubbles to stay in the melt, resulting in porous structure.

Water Impact of Syntactic Foams

PubMed Central

Shams, Adel; Zhao, Sam; Porfiri, Maurizio

2017-01-01

Syntactic foams are particulate composite materials that are extensively integrated in naval and aerospace structures as core materials for sandwich panels. While several studies have demonstrated the potential of syntactic foams as energy absorbing materials in impact tests, our understanding of their response to water impact remains elusive. In this work, we attempt a first characterization of the behavior of a vinyl ester/glass syntactic subject to slamming. High-speed imaging is leveraged to elucidate the physics of water impact of syntactic foam wedges in a free-fall drop tower. From the images, we simultaneously measure the deformation of the wedge and the hydrodynamic loading, thereby clarifying the central role of fluid–structure interaction during water impact. We study two different impact heights and microballoon density to assess the role of impact energy and syntactic foam composition on the slamming response. Our results demonstrate that both these factors have a critical role on the slamming response of syntactic foams. Reducing the density of microballoons might help to reduce the severity of the hydrodynamic loading experienced by the wedge, but this comes at the expense of a larger deformation. Such a larger deformation could ultimately lead to failure for large drop heights. These experimental results offer compelling evidence for the role of hydroelastic coupling in the slamming response of syntactic foams. PMID:28772581

Numerical modeling of the effect of heat and mass transfer in porous low-temperature heat insulation in composite material structures on the magnitude of stresses which develop

NASA Astrophysics Data System (ADS)

Kuznetsov, G. V.; Rudzinskaya, N. V.

1997-05-01

The stressed state of multilayer low-temperature heat insulation for a cryogenic fuel tank is considered. Account is taken of heat and mass transfer in foam plastic (the main heat insulation material) occurring at cryogenic temperatures. A method is developed for solving a set of differential equations and boundary conditions. Numerical studies of the main features of these processes are performed. It is established that below 200 K the stresses which arise in foam plastic markedly exceed the ultimate strength for this material. Stresses develop as a result of both a reduction in temperature and a drop in pressure in the foam plastic pores connected with material cooling. On the basis of the results obtained it is established that the combination of thermophysical processes which occur in foam plastic during cooling to cryogenic temperatures leads to changes in the stress-strained state of structure, which should be considered in planning aerospace technology.

Porous Media Approach for Modeling Closed Cell Foam

NASA Technical Reports Server (NTRS)

Ghosn, Louis J.; Sullivan, Roy M.

2006-01-01

In order to minimize boil off of the liquid oxygen and liquid hydrogen and to prevent the formation of ice on its exterior surface, the Space Shuttle External Tank (ET) is insulated using various low-density, closed-cell polymeric foams. Improved analysis methods for these foam materials are needed to predict the foam structural response and to help identify the foam fracture behavior in order to help minimize foam shedding occurrences. This presentation describes a continuum based approach to modeling the foam thermo-mechanical behavior that accounts for the cellular nature of the material and explicitly addresses the effect of the internal cell gas pressure. A porous media approach is implemented in a finite element frame work to model the mechanical behavior of the closed cell foam. The ABAQUS general purpose finite element program is used to simulate the continuum behavior of the foam. The soil mechanics element is implemented to account for the cell internal pressure and its effect on the stress and strain fields. The pressure variation inside the closed cells is calculated using the ideal gas laws. The soil mechanics element is compatible with an orthotropic materials model to capture the different behavior between the rise and in-plane directions of the foam. The porous media approach is applied to model the foam thermal strain and calculate the foam effective coefficient of thermal expansion. The calculated foam coefficients of thermal expansion were able to simulate the measured thermal strain during heat up from cryogenic temperature to room temperature in vacuum. The porous media approach was applied to an insulated substrate with one inch foam and compared to a simple elastic solution without pore pressure. The porous media approach is also applied to model the foam mechanical behavior during subscale laboratory experiments. In this test, a foam layer sprayed on a metal substrate is subjected to a temperature variation while the metal substrate is stretched to simulate the structural response of the tank during operation. The thermal expansion mismatch between the foam and the metal substrate and the thermal gradient in the foam layer causes high tensile stresses near the metal/foam interface that can lead to delamination.

Multiscale Analysis of Open-Cell Aluminum Foam for Impact Energy Absorption

NASA Astrophysics Data System (ADS)

Kim, Ji Hoon; Kim, Daeyong; Lee, Myoung-Gyu; Lee, Jong Kook

2016-09-01

The energy-absorbing characteristics of crash members in automotive collision play an important role in controlling the amount of damage to the passenger compartment. Aluminum foams have high strength-to-weight ratio and high deformability, thus good crashworthiness is expected while maintaining or even saving weights when foams are implemented in crash members. In order to investigate the effect of the open-cell aluminum foam fillers on impact performance and weight saving, a multiscale framework for evaluating the crashworthiness of aluminum foam-filled members is used. To circumvent the difficulties of mechanical tests on foams, a micromechanical model of the aluminum foam is constructed using the x-ray micro tomography and virtual tests are conducted for the micromechanical model to characterize the behavior of the foam. In the macroscale, the aluminum foam is represented by the crushable foam constitutive model, which is then incorporated into the impact test simulation of the foam-filled crash member. The multiscale foam-filled crash member model was validated for the high-speed impact test, which confirms that the material model characterized by the micromechanical approach represents the behavior of the open-cell foam under impact loading well. Finally, the crash member design for maximizing the energy absorption is discussed by investigating various designs from the foam-only structure to the hollow tube structure. It was found that the foam structure absorbs more energy than the hollow tube or foam-filled structure with the same weight.

Thermally Sprayed High Temperature Sandwich Structures: Physical Properties and Mechanical Performance

NASA Astrophysics Data System (ADS)

Salavati, Saeid

Metallic foam core sandwich structures have been of particular interest for engineering applications in recent decades due to their unique physical and mechanical properties. One of the potential applications of open pore metallic foam core sandwich structures is in heat exchangers. An investigation of sandwich structures fabricated from materials suitable for application at high temperatures and in corrosive environments was undertaken in this project. A novel method for fabrication of metallic foam core sandwich structures is thermal spray deposition of the faces on the prepared surfaces of the metallic foam substrate. The objective of the current study was to optimize the twin wire arc spray process parameters for the deposition of alloy 625 faces with controllable porosity content on the nickel foam substrate, and to characterize the physical and mechanical properties of the sandwich structure. The experimental investigations consisted of microstructural evaluation of the skin material and the foam substrate, investigation of the effect of alloying on the mechanical and thermal properties of the nickel foam, optimization of the grit-blasting and arc spray processes, observation of mechanical properties of the alloy 625 deposit by tensile testing and evaluation of the overall mechanical properties of the sandwich structure under flexural loading condition. The optimization of arc spraying process parameters allowed deposition of alloy 625 faces with a porosity of less than 4% for heat exchanger applications. Modification of the arc spraying process by co-deposition of polyester powder enabled 20% porosity to be obtained in the deposited faces for heat shield applications with film cooling. The effects of nickel foam alloying and heat treatment on the flexural rigidity of the sandwich structures were investigated and compared with as-received foam and as-fabricated sandwich structures. Available analytical models were employed to describe the effect of constituents' mechanical properties on the overall mechanical performance of the sandwich structures. Finite element modeling using ANSYS Structural was used to simulate the behaviour of the sandwich structures in four-point bending. The analytical and simulation results were compared with the experimental results obtained from the flexural tests.

Porous materials based on foaming solutions obtained from industrial waste

NASA Astrophysics Data System (ADS)

Starostina, I. V.; Antipova, A. N.; Ovcharova, I. V.; Starostina, Yu L.

2018-03-01

This study analyzes foam concrete production efficiency. Research has shown the possibility of using a newly-designed protein-based foaming agent to produce porous materials using gypsum and cement binders. The protein foaming agent is obtained by alkaline hydrolysis of a raw mixture consisting of industrial waste in an electromagnetic field. The mixture consists of spent biomass of the Aspergillus niger fungus and dust from burning furnaces used in cement production. Varying the content of the foaming agent allows obtaining gypsum binder-based foam concretes with the density of 200-500 kg/m3 and compressive strength of 0.1-1.0 MPa, which can be used for thermal and sound insulation of building interiors. Cement binders were used to obtain structural and thermal insulation materials with the density of 300-950 kg/m3 and compressive strength of 0.9-9.0 MPa. The maximum operating temperature of cement-based foam concretes is 500°C because it provides the shrinkage of less than 2%.

Coated foams, preparation, uses and articles

DOEpatents

Duchane, D.V.; Barthell, B.L.

1982-10-21

Hydrophobic cellular material is coated with a thin hydrophilic polymer skin which stretches tightly over the foam but which does not fill the cells of the foam, thus resulting in a polymer-coated foam structure having a smoothness which was not possible in the prior art. In particular, when the hydrophobic cellular material is a specially chosen hydrophobic polymer foam and is formed into arbitrarily chosen shapes prior to the coating with hydrophilic polymer, inertial confinement fusion (ICF) targets of arbitrary shapes can be produced by subsequently coating the shapes with metal or with any other suitable material. New articles of manufacture are produced, including improved ICF targets, improved integrated circuits, and improved solar reflectors and solar collectors. In the coating method, the cell size of the hydrophobic cellular material, the viscosity of the polymer solution used to coat, and the surface tension of the polymer solution used to coat are all very important to the coating.

Gravity Effects in Small-Scale Structural Modeling

DTIC Science & Technology

1988-12-01

attenuating material (Reference 23). The materials tested were cellular concrete with fly ash, expanded polystyrene concrete with fly ash, foamed...polyurethane, foamed sulfer and molded expanded polystyrene . The studies showed that with proper adjustments in the cement content, water-cement ratio and foam...Compression (Ou,c) 4000 100 Tension (Ou,t) 400 10 E/Quc 1000 1000 Ou,c/Ou,t 10 10 Further analysis of the properties of expanded polystyrene concrete with

Hybrid Deployable Foam Antennas and Reflectors

NASA Technical Reports Server (NTRS)

Rivellini, Tommaso; Willis, Paul; Hodges, Richard; Spitz, Suzanne

2006-01-01

Hybrid deployable radio antennas and reflectors of a proposed type would feature rigid narrower apertures plus wider adjoining apertures comprising reflective surfaces supported by open-cell polymeric foam structures (see figure). The open-cell foam structure of such an antenna would be compressed for compact stowage during transport. To initiate deployment of the antenna, the foam structure would simply be released from its stowage mechanical restraint. The elasticity of the foam would drive the expansion of the foam structure to its full size and shape. There are several alternatives for fabricating a reflective surface supported by a polymeric foam structure. One approach would be to coat the foam with a metal. Another approach would be to attach a metal film or a metal-coated polymeric membrane to the foam. Yet another approach would be to attach a metal mesh to the foam. The hybrid antenna design and deployment concept as proposed offers significant advantages over other concepts for deployable antennas: 1) In the unlikely event of failure to deploy, the rigid narrow portion of the antenna would still function, providing a minimum level of assured performance. In contrast, most other concepts for deploying a large antenna from compact stowage are of an "all or nothing" nature: the antenna is not useful at all until and unless it is fully deployed. 2) Stowage and deployment would not depend on complex mechanisms or actuators, nor would it involve the use of inflatable structures. Therefore, relative to antennas deployed by use of mechanisms, actuators, or inflation systems, this antenna could be lighter, cheaper, amenable to stowage in a smaller volume, and more reliable. An open-cell polymeric (e.g., polyurethane) foam offers several advantages for use as a compressible/expandable structural material to support a large antenna or reflector aperture. A few of these advantages are the following: 3) The open cellular structure is amenable to compression to a very small volume - typically to 1/20 of its full size in one dimension. 4) At a temperature above its glass-transition temperature (T(sub g)), the foam strongly damps vibrations. Even at a temperature below T(sub g), the damping should exceed that of other materials. 5) In its macroscopic mechanical properties, an open-cell foam is isotropic. This isotropy facilitates computational modeling of antenna structures. 6) Through chemical formulation, the T(sub g) of an open-cell polyurethane foam can be set at a desired value between about - 100 and about 0 C. Depending on the application, it may or may not be necessary to rigidify a foam structure after deployment. If rigidification is necessary, then the T(sub g) of the foam can be tailored to exceed the temperature of the deployment environment, in conjunction with providing a heater to elasticize the foam for deployment. Once deployed, the foam would become rigidified by cooling to below T(sub g). 7) Techniques for molding or machining polymeric foams (especially including open-cell polyurethane foams) to desired sizes and shapes are well developed.

Role of Temperature and SiCP Parameters in Stability and Quality of Al-Si-Mg/SiC Foams

NASA Astrophysics Data System (ADS)

Ravi Kumar, N. V.; Gokhale, Amol A.

2018-06-01

Composites of Al-Si-Mg (A356) alloy with silicon carbide particles were synthesized in-house and foamed by melt processing using titanium hydride as foaming agent. The effects of the SiCP size and content, and foaming temperature on the stability and quality of the foam were explored. It was observed that the foam stability depended on the foaming temperature alone but not on the particle size or volume percent within the studied ranges. Specifically, foam stability was poor at 670°C. Among the stable foams obtained at 640°C, cell soundness (absence of/low defects, and collapse) was seen to vary depending on the particle size and content; For example, for finer size, lower particle contents were sufficient to obtain sound cell structure. It is possible to determine a foaming process window based on material and process parameters for good expansion, foam stability, and cell structure.

Structural applications of metal foams considering material and geometrical uncertainty

NASA Astrophysics Data System (ADS)

Moradi, Mohammadreza

Metal foam is a relatively new and potentially revolutionary material that allows for components to be replaced with elements capable of large energy dissipation, or components to be stiffened with elements which will generate significant supplementary energy dissipation when buckling occurs. Metal foams provide a means to explore reconfiguring steel structures to mitigate cross-section buckling in many cases and dramatically increase energy dissipation in all cases. The microstructure of metal foams consists of solid and void phases. These voids have random shape and size. Therefore, randomness ,which is introduced into metal foams during the manufacturing processes, creating more uncertainty in the behavior of metal foams compared to solid steel. Therefore, studying uncertainty in the performance metrics of structures which have metal foams is more crucial than for conventional structures. Therefore, in this study, structural application of metal foams considering material and geometrical uncertainty is presented. This study applies the Sobol' decomposition of a function of many random variables to different problem in structural mechanics. First, the Sobol' decomposition itself is reviewed and extended to cover the case in which the input random variables have Gaussian distribution. Then two examples are given for a polynomial function of 3 random variables and the collapse load of a two story frame. In the structural example, the Sobol' decomposition is used to decompose the variance of the response, the collapse load, into contributions from the individual input variables. This decomposition reveals the relative importance of the individual member yield stresses in determining the collapse load of the frame. In applying the Sobol' decomposition to this structural problem the following issues are addressed: calculation of the components of the Sobol' decomposition by Monte Carlo simulation; the effect of input distribution on the Sobol' decomposition; convergence of estimates of the Sobol' decomposition with sample size using various sampling schemes; the possibility of model reduction guided by the results of the Sobol' decomposition. For the rest of the study the different structural applications of metal foam is investigated. In the first application, it is shown that metal foams have the potential to serve as hysteric dampers in the braces of braced building frames. Using metal foams in the structural braces decreases different dynamic responses such as roof drift, base shear and maximum moment in the columns. Optimum metal foam strengths are different for different earthquakes. In order to use metal foam in the structural braces, metal foams need to have stable cyclic response which might be achievable for metal foams with high relative density. The second application is to improve strength and ductility of a steel tube by filling it with steel foam. Steel tube beams and columns are able to provide significant strength for structures. They have an efficient shape with large second moment of inertia which leads to light elements with high bending strength. Steel foams with high strength to weight ratio are used to fill the steel tube to improves its mechanical behavior. The linear eigenvalue and plastic collapse finite element (FE) analysis are performed on steel foam filled tube under pure compression and three point bending simulation. It is shown that foam improves the maximum strength and the ability of energy absorption of the steel tubes significantly. Different configurations with different volume of steel foam and composite behavior are investigated. It is demonstrated that there are some optimum configurations with more efficient behavior. If composite action between steel foam and steel increases, the strength of the element will improve due to the change of the failure mode from local buckling to yielding. Moreover, the Sobol' decomposition is used to investigate uncertainty in the strength and ductility of the composite tube, including the sensitivity of the strength to input parameters such as the foam density, tube wall thickness, steel properties etc. Monte Carlo simulation is performed on aluminum foam filled tubes under three point bending conditions. The simulation method is nonlinear finite element analysis. Results show that the steel foam properties have a greater effect on ductility of the steel foam filled tube than its strength. Moreover, flexural strength is more sensitive to steel properties than to aluminum foam properties. Finally, the properties of hypothetical structural steel foam C-channels foamed are investigated via simulations. In thin-walled structural members, stability of the walls is the primary driver of structural limit states. Moreover, having a light weight is one of the main advantages of the thin-walled structural members. Therefore, thin-walled structural members made of steel foam exhibit improved strength while maintaining their low weight. Linear eigenvalue, finite strip method (FSM) and plastic collapse FE analysis is used to evaluate the strength and ductility of steel foam C-channels under uniform compression and bending. It is found that replacing steel walls of the C-channel with steel foam walls increases the local buckling resistance and decreases the global buckling resistance of the C-channel. By using the Sobol' decomposition, an optimum configuration for the variable density steel foam C-channel can be found. For high relative density, replacing solid steel of the lips and flange elements with steel foam increases the buckling strength. On the other hand, for low relative density replacing solid steel of the lips and flange elements with steel foam deceases the buckling strength. Moreover, it is shown that buckling strength of the steel foam C-channel is sensitive to the second order Sobol' indices. In summary, it is shown in this research that the metal foams have a great potential to improve different types of structural responses, and there are many promising application for metal foam in civil structures.

Preparation and characterization of new biologically active polyurethane foams.

PubMed

Savelyev, Yuri; Veselov, Vitali; Markovskaya, Ludmila; Savelyeva, Olga; Akhranovich, Elena; Galatenko, Natalya; Robota, Ludmila; Travinskaya, Tamara

2014-12-01

Biologically active polyurethane foams are the fast-developed alternative to many applications of biomedical materials. Due to the polyurethane structure features and foam technology it is possible to incorporate into their structure the biologically active compounds of target purpose via structural-chemical modification of macromolecule. A series of new biologically active polyurethane foams (PUFs) was synthesized with polyethers (MM 2500-5000), polyesters MM (500-2200), 2,4(2,6) toluene diisocyanate, water as a foaming agent, catalysts, foam stabilizers and functional compounds. Different functional compounds: 1,4-di-N-oxy-2,3-bis-(oxymethyl)-quinoxaline (DOMQ), partial sodium salt of poly(acrylic acid) and 2,6-dimethyl-N,N-diethyl aminoacetatanilide hydrochloride were incorporated into the polymer structure/composition due to the chemical and/or physical bonding. Structural peculiarities of PUFs were studied by FTIR spectroscopy and X-ray scattering. Self-adhesion properties of PUFs were estimated by measuring of tensile strength at break of adhesive junction. The optical microscopy method was performed for the PUF morphology studies. Toxicological estimation of the PUFs was carried out in vitro and in vivo. The antibacterial action towards the Gram-positive and Gram-negative bacteria (Escherichia coli ATC 25922, E. coli ATC 2150, Klebsiella pneumoniae 6447, Staphylococcus aureus 180, Pseudomonas aeruginosa 8180, Proteus mirabilis F 403, P. mirabilis 6054, and Proteus vulgaris 8718) was studied by the disc method on the solid nutrient. Physic-chemical properties of the PUFs (density, tensile strength and elongation at break, water absorption and vapor permeability) showed that all studied PUFs are within the operational requirements for such materials and represent fine-cellular foams. Spectral studies confirmed the incorporation of DOMQ into the PUF's macrochain. PUFs are characterized by microheterogeneous structure. They are antibacterially active, non-toxic materials with high affinity to the tissue body, self-adhesive properties and local anesthetic effect. Copyright © 2014 Elsevier B.V. All rights reserved.

Method of forming a continuous polymeric skin on a cellular foam material

DOEpatents

Duchane, David V.; Barthell, Barry L.

1985-01-01

Hydrophobic cellular material is coated with a thin hydrophilic polymer skin which stretches tightly over the outer surface of the foam but which does not fill the cells of the foam, thus resulting in a polymer-coated foam structure having a smoothness which was not possible in the prior art. In particular, when the hydrophobic cellular material is a specially chosen hydrophobic polymer foam and is formed into arbitrarily chosen shapes prior to the coating with hydrophilic polymer, inertial confinement fusion (ICF) targets of arbitrary shapes can be produced by subsequently coating the shapes with metal or with any other suitable material. New articles of manufacture are produced, including improved ICF targets, improved integrated circuits, and improved solar reflectors and solar collectors. In the coating method, the cell size of the hydrophobic cellular material, the viscosity of the polymer solution used to coat, and the surface tensin of the polymer solution used to coat are all very important to the coating.

Advanced Metal Foam Structures for Outer Space

NASA Technical Reports Server (NTRS)

Hanan, Jay; Johnson, William; Peker, Atakan

2005-01-01

A document discusses a proposal to use advanced materials especially bulk metallic glass (BMG) foams in structural components of spacecraft, lunar habitats, and the like. BMG foams, which are already used on Earth in some consumer products, are superior to conventional metal foams: BMG foams have exceptionally low mass densities and high strength-to-weight ratios and are more readily processable into strong, lightweight objects of various sizes and shapes. These and other attractive properties of BMG foams would be exploited, according to the proposal, to enable in situ processing of BMG foams for erecting and repairing panels, shells, containers, and other objects. The in situ processing could include (1) generation of BMG foams inside prefabricated deployable skins that would define the sizes and shapes of the objects thus formed and (2) thermoplastic deformation of BMG foams. Typically, the generation of BMG foams would involve mixtures of precursor chemicals that would be subjected to suitable pressure and temperature schedules. In addition to serving as structural components, objects containing or consisting of BMG foams could perform such functions as thermal management, shielding against radiation, and shielding against hypervelocity impacts of micrometeors and small debris particles.

Noninvasive 3D Visualization of Defects and Crack Propagation in Layered Foam Structures by Phase Contrast Microimaging

NASA Technical Reports Server (NTRS)

Hu, Z. W.; DeCarlo, F.

2006-01-01

Applications of polymeric foams in our modern society continue to grow because of their light weight, high strength, excellent thermal and mechanical insulation, and the ease of engineering. Among others, closed-cell foam has been structurally used for thermally insulating the shuttle external tank. However, internal defects of the foams were difficult to observe non-invasively due to limited sensitivity to the low-density structures possessed by traditional imaging tools such as computed X-ray tomography By combining phase contrast X-ray imaging with pressure loading, we succeeded in precisely mapping intact cellular structure and defects inside the bulk of layered foam and visualizing its subsequent response to the pressure in three-dimensional space. The work demonstrated a powerfir1 approach for yielding insight into underlying problems in lightweight cellular materials otherwise unobtainable.

Synthesis and development of low cost, high temperature N-arylene polybenzimidazole foam material

NASA Technical Reports Server (NTRS)

Harrison, E. S.

1975-01-01

Polymer (and foam) studies followed two basic routes: (1) formation of high molecular weight uncyclized polyamide followed by subsequent fusion and cyclodehydration to yield NABI (foam) and (2) polymer and foam formation by reaction of diphenyl esters (or anhydrides) with the tetramine. The latter route was found much more attractive since considerable versatility in both basic polymer structure and crosslinkability is achievable. Preliminary studies on BAB, phthalic anhydride (PA), and 3, 3 (prime), 4, 4(prime) benzo pheno netetracarboxylic acid dianhydride (BTDA) as crosslinked polymer precursors were conducted. Nonmelting rigid char forming foams with densities as low as 2.7 lb/cubic ft. were achieved. The program was successful in the preparation of a potentially low cost, low density, high char yield, high temperature foam material.

From Stochastic Foam to Designed Structure: Balancing Cost and Performance of Cellular Metals

PubMed Central

Lehmhus, Dirk; Vesenjak, Matej

2017-01-01

Over the past two decades, a large number of metallic foams have been developed. In recent years research on this multi-functional material class has further intensified. However, despite their unique properties only a limited number of large-scale applications have emerged. One important reason for this sluggish uptake is their high cost. Many cellular metals require expensive raw materials, complex manufacturing procedures, or a combination thereof. Some attempts have been made to decrease costs by introducing novel foams based on cheaper components and new manufacturing procedures. However, this has often yielded materials with unreliable properties that inhibit utilization of their full potential. The resulting balance between cost and performance of cellular metals is probed in this editorial, which attempts to consider cost not in absolute figures, but in relation to performance. To approach such a distinction, an alternative classification of cellular metals is suggested which centers on structural aspects and the effort of realizing them. The range thus covered extends from fully stochastic foams to cellular structures designed-to-purpose. PMID:28786935

Low density, microcellular foams, preparation, and articles

DOEpatents

Young, A.T.

1982-03-03

A microcellular low-density foam of poly(4-methyl-1-pentene) particularly useful for forming targets for inertial confinement fusion has been developed. Articles made from the foam have been machined to tolerances of 0.0001 inch, although the densities of the fragile foam are low (about 10 to about 100 mg/cc) and the cell sizes are small (about 10 to about 30 ..mu..m). Methods for forming the foam and articles are given. The yield strength of the foam of the invention is higher than was obtained in other structures of this same material.

Investigations on injection molded, glass-fiber reinforced polyamide 6 integral foams using breathing mold technology

NASA Astrophysics Data System (ADS)

Roch, A.; Kehret, L.; Huber, T.; Henning, F.; Elsner, P.

2015-05-01

Investigations on PA6-GF50 integral foams have been carried out using different material systems: longfiber- and shortfiber-reinforced PA6 as well as unreinforced PA6 as a reference material. Both chemical and physical blowing agents were applied. Breathing mold technology (decompression of the mold) was selected for the foaming process. The integral foam design, which can be conceived as a sandwich structure, helps to save material in the neutral axis area and maintains a distance between load-bearing, unfoamed skin layers. For all test series an initial mold gap of 2.5 mm was chosen and the same amount of material was injected. In order to realize different density reductions, the mold opening stroke was varied. The experiments showed that, at a constant mass per unit area, integral polyamide 6 foams have a significantly higher bending stiffness than compact components, due to their higher area moment of inertia after foaming. At a constant surface weight the bending stiffness in these experiments could be increased by up to 600 %. Both shortfiber- and longfiber-reinforced polyamide 6 showed an increase in energy absorption during foaming.

Research and analysis on electrochemical performances of α-Fe{sub 2}O{sub 3} electrode in Li-ion battery with different current collectors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Lihong, E-mail: huang.lihong@foxmail.com; Min, Zhonghua; Zhang, Qinyong

2015-06-15

Highlights: • We achieved a reversible capacity of 415 mAh g{sup −1} after 30 cycles for α-Fe{sub 2}O{sub 3} electrode in Li-ion battery. • Better electrical performance was obtained when using Cu foam as current collector. • As current collector for α-Fe{sub 2}O{sub 3} electrode, Cu foam is better than Cu foil and Ni foam. • It could avoid the active materials falling off from the current collector during cycling. • It is owe to smaller surface film resistance, charge-transfer resistance, etc. - Abstract: In this work, we reported a simple synthesis of submicron α-Fe{sub 2}O{sub 3} with rod-like structure.more » When it evaluated as electrode material for lithium ion battery, comparing with Cu foil and Ni foam, the as-prepared α-Fe{sub 2}O{sub 3} electrodes with Cu foam current collector exhibited higher reversible capacity of 415 mAh g{sup −1} and more stable cycle performance after 30 cycles. Comparative researches on electrochemical performances of the α-Fe{sub 2}O{sub 3} employing different current collectors (Cu foil, Cu foam and Ni foam) were discussed here in detail. According to our results, the improved electrochemical behaviors of α-Fe{sub 2}O{sub 3} electrode with Cu foam current collector could be attributed to its particular electrode structure, i.e., porous, good electric conductivity, closed adhere to the electrode materials. Just because of that, it may make sure an easy accessibility of electrolytes and fast transportation of lithium ions, importantly, it could avoid the active materials falling off from the current collector on account of volume expansion.« less

Biot theory and acoustical properties of high porosity fibrous materials and plastic foams

NASA Technical Reports Server (NTRS)

Allard, J.; Aknine, A.

1987-01-01

Experimental values of acoustic wave propagation constant and characteristic impedance in fibrous materials, and normal absorption for two plastic foams, were compared to theoretical predictions obtained with Biot's theory. The best agreement was observed for fibrous materials between Biot's theory and Delany and Bazley experiments for a nearly zero mass coupling parameter. For foams, the lambda/4 structure resonance effect on absorption was calculated by using four-pole modelling of the medium. A significant mass coupling parameter is then necessary for obtaining agreement between the behavior of the measured absorption coefficients and the theoretical predictions. It is shown how the formalism used for predicting foams absorption coefficients may be used for studying the acoustic behavior of multi-layered media.

Nanoreinforced xylan–cellulose composite foams by freeze-casting

Treesearch

Tobias Köhnke; Angela Lin; Thomas Elder; Hans Theliander; Arthur J. Ragauskas

2012-01-01

Structured biofoams have been prepared from the readily available renewable biopolymer xylan by employing an ice-templating technique, where the pore morphology of the material can be controlled by the solidification conditions and the molecular structure of the polysaccharide. Furthermore, reinforcement of these biodegradable foams using cellulose nanocrystals shows...

Synergistic effects from graphene and carbon nanotubes endow ordered hierarchical structure foams with a combination of compressibility, super-elasticity and stability and potential application as pressure sensors

NASA Astrophysics Data System (ADS)

Kuang, Jun; Dai, Zhaohe; Liu, Luqi; Yang, Zhou; Jin, Ming; Zhang, Zhong

2015-05-01

Nanostructured carbon material based three-dimensional porous architectures have been increasingly developed for various applications, e.g. sensors, elastomer conductors, and energy storage devices. Maintaining architectures with good mechanical performance, including elasticity, load-bearing capacity, fatigue resistance and mechanical stability, is prerequisite for realizing these functions. Though graphene and CNT offer opportunities as nanoscale building blocks, it still remains a great challenge to achieve good mechanical performance in their microarchitectures because of the need to precisely control the structure at different scales. Herein, we fabricate a hierarchical honeycomb-like structured hybrid foam based on both graphene and CNT. The resulting materials possess excellent properties of combined high specific strength, elasticity and mechanical stability, which cannot be achieved in neat CNT and graphene foams. The improved mechanical properties are attributed to the synergistic-effect-induced highly organized, multi-scaled hierarchical architectures. Moreover, with their excellent electrical conductivity, we demonstrated that the hybrid foams could be used as pressure sensors in the fields related to artificial skin.Nanostructured carbon material based three-dimensional porous architectures have been increasingly developed for various applications, e.g. sensors, elastomer conductors, and energy storage devices. Maintaining architectures with good mechanical performance, including elasticity, load-bearing capacity, fatigue resistance and mechanical stability, is prerequisite for realizing these functions. Though graphene and CNT offer opportunities as nanoscale building blocks, it still remains a great challenge to achieve good mechanical performance in their microarchitectures because of the need to precisely control the structure at different scales. Herein, we fabricate a hierarchical honeycomb-like structured hybrid foam based on both graphene and CNT. The resulting materials possess excellent properties of combined high specific strength, elasticity and mechanical stability, which cannot be achieved in neat CNT and graphene foams. The improved mechanical properties are attributed to the synergistic-effect-induced highly organized, multi-scaled hierarchical architectures. Moreover, with their excellent electrical conductivity, we demonstrated that the hybrid foams could be used as pressure sensors in the fields related to artificial skin. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr00841g

Ultralight anisotropic foams from layered aligned carbon nanotube sheets

NASA Astrophysics Data System (ADS)

Faraji, Shaghayegh; L. Stano, Kelly; Yildiz, Ozkan; Li, Ang; Zhu, Yuntian; Bradford, Philip D.

2015-10-01

In this work, we present large scale, ultralight aligned carbon nanotube (CNT) structures which have densities an order of magnitude lower than CNT arrays, have tunable properties and exhibit resiliency after compression. By stacking aligned sheets of carbon nanotubes and then infiltrating with a pyrolytic carbon (PyC), resilient foam-like materials were produced that exhibited complete recovery from 90% compressive strain. With density as low as 3.8 mg cm-3, the foam structure is over 500 times less dense than bulk graphite. Microscopy revealed that PyC coated the junctions among CNTs, and also increased CNT surface roughness. These changes in the morphology explain the transition from inelastic behavior to foam-like recovery of the layered CNT sheet structure. Mechanical and thermal properties of the foams were tuned for different applications through variation of PyC deposition duration while dynamic mechanical analysis showed no change in mechanical properties over a large temperature range. Observation of a large and linear electrical resistance change during compression of the aligned CNT/carbon (ACNT/C) foams makes strain/pressure sensors a relevant application. The foams have high oil absorption capacities, up to 275 times their own weight, which suggests they may be useful in water treatment and oil spill cleanup. Finally, the ACNT/C foam's high porosity, surface area and stability allow for demonstration of the foams as catalyst support structures.In this work, we present large scale, ultralight aligned carbon nanotube (CNT) structures which have densities an order of magnitude lower than CNT arrays, have tunable properties and exhibit resiliency after compression. By stacking aligned sheets of carbon nanotubes and then infiltrating with a pyrolytic carbon (PyC), resilient foam-like materials were produced that exhibited complete recovery from 90% compressive strain. With density as low as 3.8 mg cm-3, the foam structure is over 500 times less dense than bulk graphite. Microscopy revealed that PyC coated the junctions among CNTs, and also increased CNT surface roughness. These changes in the morphology explain the transition from inelastic behavior to foam-like recovery of the layered CNT sheet structure. Mechanical and thermal properties of the foams were tuned for different applications through variation of PyC deposition duration while dynamic mechanical analysis showed no change in mechanical properties over a large temperature range. Observation of a large and linear electrical resistance change during compression of the aligned CNT/carbon (ACNT/C) foams makes strain/pressure sensors a relevant application. The foams have high oil absorption capacities, up to 275 times their own weight, which suggests they may be useful in water treatment and oil spill cleanup. Finally, the ACNT/C foam's high porosity, surface area and stability allow for demonstration of the foams as catalyst support structures. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr03899e

Experimental Investigation of Properties of Foam Concrete for Industrial Floors in Testing Field

NASA Astrophysics Data System (ADS)

Vlcek, Jozef; Drusa, Marian; Scherfel, Walter; Sedlar, Bronislav

2017-12-01

Foam concrete (FC), as a mixture of cement, water, additives and technical foam, is well known for more than 30 years. It is building material with good mechanical properties, low thermal conductivity, simple and even high technological treatment. Foam concrete contains closed void pores, what allows achieving low bulk density and spare of raw materials. Thanks to its properties, it is usable as a replacement of conventional subbase layers of the industrial floors, the transport areas or as a part of the foundation structures of the buildings. Paper presents the preparation of the testing field (physical model) which was created for experimental investigation of the foam concrete subbase layer of the industrial floor in a real scale.

Characterization of boron coated vitreous carbon foam for neutron detection

NASA Astrophysics Data System (ADS)

Lavelle, C. M.; Deacon, Ryan M.; Hussey, Daniel S.; Coplan, Michael; Clark, Charles W.

2013-11-01

Reticulated vitreous carbon (RVC) foams coated with 3-11 μm thick layers of boron carbide (B4C) are experimentally characterized for use as an active material for neutron detection. The potential advantage of this material over thin films is that it can be fabricated in any shape and its porous structure may enhance the emission surface area for ionizing charged particles following thermal neutron capture. A coated foam is also advantageous because the neutron-absorbing material is only on the surface, which is more efficient for α particle emission on a per captured neutron basis. Measurements of the B4C layer thickness of an RVC coated foam, and determination of its elemental composition, are performed using scanning electron microscopy. Neutron transmission measurements using neutron radiography are presented and α particle emission from the coated foam in response to a moderated 252Cf thermal neutron source is demonstrated.

Liquefaction of oak tree bark with different biomass/phenol mass ratios and utilizing bio-based polyols for carbon foam production

NASA Astrophysics Data System (ADS)

Ozbay, N.; Yargic, A. S.

2017-02-01

Carbon foam is sponge like carbonaceous material with low density, high conductivity and high strength; which is used in various applications such as catalyst supports, membrane separations, high thermally conductive heat sinks, energy absorption materials, high temperature thermal insulation. Coal or fossil oils are conventionally used to fabricate pitch, phenolic resin and polyurethane as carbon foam precursor. Biomass liquefaction is a developing technique to convert biomass resources into the industrial chemicals. In this study, oak tree bark was liquefied under mild conditions with different mass ratio of biomass/phenol; and the liquefaction product was used as polyol to produce porous resin foams. Obtained resin foams were carbonized at 400 °C, and then activated at 800 °C under nitrogen atmosphere. Structure evaluation of resin foams, carbonized foams and activated carbon foams from liquefied oak tree bark was investigated by using elemental analysis, x-ray diffraction, nitrogen adsorption/desorption isotherms, scanning electron microscopy, bulk density and compressive strength tests.

Use of Carbon Nano-Fiber Foams as Strain Gauges to Detect Crack Propagation

DTIC Science & Technology

2015-06-01

FIBER FOAMS AS STRAIN GAUGES TO DETECT CRACK PROPAGATION by Ervin N. Mercado June 2015 Thesis Advisor: Claudia C. Luhrs Co-Advisor...AND DATES COVERED Master’s Thesis 4. TITLE AND SUBTITLE USE OF CARBON NANO-FIBER FOAMS AS STRAIN GAUGES TO DETECT CRACK PROPAGATION 5. FUNDING...using carbon nanofiber foams as strain gauge material to detect crack propagation in aluminum structures. We produced the tridimensional carbon

Foam composite structures. [for fire retardant airframe materials

NASA Technical Reports Server (NTRS)

Delano, C. B.; Milligan, R. J.

1976-01-01

The need to include fire resistant foams into state of the art aircraft interior paneling to increase passenger safety in aircraft fires was studied. Present efforts were directed toward mechanical and fire testing of panels with foam inclusions. Skinned foam filled honeycomb and PBI structural foams were the two constructions investigated with attention being directed toward weight/performance/cost trade-off. All of the new panels demonstrated improved performance in fire and some were lighter weight but not as strong as the presently used paneling. Continued efforts should result in improved paneling for passenger safety. In particular the simple partial filling (fire side) of state-of-the-art honeycomb with fire resistant foams with little sacrifice in weight would result in panels with increased fire resistance. More important may be the retarded rate of toxic gas evolution in the fire due to the protection of the honeycomb by the foam.

Low density, microcellular foams, preparation, and articles

DOEpatents

Young, Ainslie T.; Marsters, Robert G.; Moreno, Dawn K.

1984-01-01

A microcellular low density foam of poly(4-methyl-1-pentene) which is particularly useful for forming targets for inertial confinement fusion has been developed. Articles made from the foam have been machined to tolerances of 0.0001 inch, although the densities of the fragile foam are low (about 10 to about 100 mg/cc) and the cell sizes are small (about 10 to about 30 .mu.m). Methods for forming the foam and articles are given; and the yield strength of the foam of the invention is higher than was obtained in other structures of this same material.

Material heterogeneity in cancellous bone promotes deformation recovery after mechanical failure.

PubMed

Torres, Ashley M; Matheny, Jonathan B; Keaveny, Tony M; Taylor, David; Rimnac, Clare M; Hernandez, Christopher J

2016-03-15

Many natural structures use a foam core and solid outer shell to achieve high strength and stiffness with relatively small amounts of mass. Biological foams, however, must also resist crack growth. The process of crack propagation within the struts of a foam is not well understood and is complicated by the foam microstructure. We demonstrate that in cancellous bone, the foam-like component of whole bones, damage propagation during cyclic loading is dictated not by local tissue stresses but by heterogeneity of material properties associated with increased ductility of strut surfaces. The increase in surface ductility is unexpected because it is the opposite pattern generated by surface treatments to increase fatigue life in man-made materials, which often result in reduced surface ductility. We show that the more ductile surfaces of cancellous bone are a result of reduced accumulation of advanced glycation end products compared with the strut interior. Damage is therefore likely to accumulate in strut centers making cancellous bone more tolerant of stress concentrations at strut surfaces. Hence, the structure is able to recover more deformation after failure and return to a closer approximation of its original shape. Increased recovery of deformation is a passive mechanism seen in biology for setting a broken bone that allows for a better approximation of initial shape during healing processes and is likely the most important mechanical function. Our findings suggest a previously unidentified biomimetic design strategy in which tissue level material heterogeneity in foams can be used to improve deformation recovery after failure.

Vibration Characteristics Determined for Stainless Steel Sandwich Panels With a Metal Foam Core for Lightweight Fan Blade Design

NASA Technical Reports Server (NTRS)

Ghosn, Louis J.; Min, James B.; Raj, Sai V.; Lerch, Bradley A.; Holland, Frederic A., Jr.

2004-01-01

The goal of this project at the NASA Glenn Research Center is to provide fan materials that are safer, weigh less, and cost less than the currently used titanium alloy or polymer matrix composite fans. The proposed material system is a sandwich fan construction made up of thin solid face sheets and a lightweight metal foam core. The stiffness of the sandwich structure is increased by separating the two face sheets by the foam layer. The resulting structure has a high stiffness and lighter weight in comparison to the solid facesheet material alone. The face sheets carry the applied in-plane and bending loads (ref. 1). The metal foam core must resist the transverse shear and transverse normal loads, as well as keep the facings supported and working as a single unit. Metal foams have ranges of mechanical properties, such as light weight, impact resistance, and vibration suppression (ref. 2), which makes them more suitable for use in lightweight fan structures. Metal foams have been available for decades (refs. 3 and 4), but the difficulties in the original processes and high costs have prevented their widespread use. However, advances in production techniques and cost reduction have created a new interest in this class of materials (ref. 5). The material chosen for the face sheet and the metal foam for this study was the aerospace-grade stainless steel 17-4PH. This steel was chosen because of its attractive mechanical properties and the ease with which it can be made through the powder metallurgy process (ref. 6). The advantages of a metal foam core, in comparison to a typical honeycomb core, are material isotropy and the ease of forming complex geometries, such as fan blades. A section of a 17-4PH sandwich structure is shown in the following photograph. Part of process of designing any blade is to determine the natural frequencies of the particular blade shape. A designer needs to predict the resonance frequencies of a new blade design to properly identify a useful operating range. Operating a blade at or near the resonance frequencies leads to high-cycle fatigue, which ultimately limits the blade's durability and life. So the aim of this study is to determine the variation of the resonance frequencies for an idealized sandwich blade as a function of its face-sheet thickness, core thickness, and foam density. The finite element method is used to determine the natural frequencies for an idealized rectangular sandwich blade. The proven Lanczos method (ref. 7) is used in the study to extract the natural frequency.

[Effect of ozonated water on physical and chemical properties of vacuum sealing drainage material].

PubMed

Jiang, Nan; Ma, Yunfei; Lin, Qingrong; Chen, Anfu; Zhao, Peiran; Ni, Guoxin; Yu, Bin

2013-02-01

To investigate the influence of ozonated water on physical and chemical properties of vacuum sealing drainage (VSD) materials. VSD materials (foam and sealing membrane) were immersed in 10 µg/ml ozonated water for 1 h twice daily for 8 days. The foam appearance and microscopic structure of the materials were observed, and tensile tests and Raman spectrum scan were performed assess the effect of ozonated water. Simulated VSD devices were prepared and tested for leakproofness under negative pressure after ozonated water treatment. zonated water treatment for 8 days caused no obvious abnormal changes in the foam appearance or microscopic structure of the materials. The maximum tensile load of foam before and after ozonated water treatment was 4.25∓0.73 kgf and 2.44∓0.19 kgf (P=0.000), the momentary distance when the foam torn before and after intervention was 92.54∓12.83 mm and 64.44∓4.60 mm, respectively (P=0.000). The corresponding results for VSD sealing membrane were 0.70∓0.58 kgf and 0.71∓0.08 kgf (P=0.698), and 99.30∓10.27 mm and 100.95∓18.22 mm (P=0.966), respectively. Raman spectroscopy revealed changes in only several wave intensities and no new chemical groups appeared within the scan range of 400-4000 cm(-1). The VSD device was well hermetic after treatment with ozonated water. Except for a decreased stretch resistance property of the foam, VSD materials display no obvious changes in physical and chemical characteristics after treatment with ozonated water for 8 days.

Lithographic Printing Via Two-Photon Polymerization of Engineered Foams

DOE PAGES

Herman, Matthew J.; Peterson, Dominic; Henderson, Kevin; ...

2017-11-29

Understanding deuterium-tritium mix in capsules is critical to achieving fusion within inertial confined fusion experiments. One method of understanding how the mix of hydrogen fuels can be controlled is by creating various structured deuterated foams and filling the capsule with liquid tritium. Historically, these materials have been a stochastically structured gas-blown foam. Later, to improve the uniformity of this material, pore formers have been used which are then chemically removed, leaving behind a foam of monodisperse voids. However, this technique is still imperfect in that fragments of the pore templating particles may not be completely removed and the void distributionmore » may not be uniform over the size scale of the capsule. Recently, advances in three-dimensional printing suggest that it can be used to create microlattices and capsule walls in one single print. Demonstrated in this paper are proof-of-concept microlattices produced using two-photon polymerization with submicrometer resolution of various structures as well as a microlattice-containing capsule. Finally, with this technology, complete control of the mixing structure is possible, amenable to modeling and easily modified for tailored target design.« less

LFT foam - Lightweight potential for semi-structural components through the use of long-glass-fiber-reinforced thermoplastic foams

NASA Astrophysics Data System (ADS)

Roch, A.; Huber, T.; Henning, F.; Elsner, P.

2014-05-01

Investigations on PP-LGF30 foam sandwiches have been carried out using different manufacturing processes: standard injection molding, MuCell® and LFT-D foam. Both chemical and physical blowing agents were applied. Precision mold opening (breathing mold technology) was selected for the foaming process. The integral foam design, which can be conceived as a sandwich structure, helps to save material in the neutral axis area and maintains a distance between load-bearing, unfoamed skin layers. The experiments showed that, at a constant mass per unit area, integral foams have a significantly higher flexural rigidity than compact components, due to their greater area moment of inertia after foaming: with an increase of the wall thickness from 3.6 mm to 4.4 mm compared to compact construction, the flexural rigidity increased by 75 %. With a final wall thickness of 5.8 mm an increase of 300 % was measured. Compared to non-reinforced components that show significant embrittlement during foaming, the energy absorption capacity (impact strength) of LFT foam components remains almost constant.

Gamma-irradiated cross-linked LDPE foams: Characteristics and properties

NASA Astrophysics Data System (ADS)

Cardoso, E. C. L.; Scagliusi, S. R.; Parra, D. F.; Lugão, A. B.

2013-03-01

Foamed polymers are future materials, as they are increasingly considered "green materials" due to their interesting properties at very low consumption of raw materials. They can be used to improve appearance of insulation structures, thermal and acoustic insulation, core materials for sandwich panels, fabrication of furniture and flotation materials or to reduce costs involving materials. Low-density polyethylene is widely used because of its excellent properties, such as softness, elasticity, processibility and insulation. In general, cross-linking is often applied to improve the thermal and mechanical properties of polyethylene products, due to the formation of a three-dimensional network. In particular for the production of PE foams, cross-linking is applied prior the expansion to control bubble formation, cell characteristics and final properties of the foam. However, the usual production process of PE foams is a process in which a gaseous blowing agent is injected into a melted thermoplastic polymer, under pressure, to form a solution between blowing agent and melted polymer. An extrusion system is provided for foaming the polymer, supplied to an extruder and moving through a rotating screw. The pressure must be high enough to keep the gas blowing agent (or foaming agent) in the solution with the melt. The foaming agent is then diffused and dissolved in the molten material to form a single-phase solution. In the present work carbon dioxide was used as the bowing agent, a chemically stable and non-toxic gas, with good diffusion coefficient; gas pressure used varied within a 20-40 bar range. Some requirements for physical foaming are required, as low friction heat generation, homogeneous melt temperature distribution, melt temperature at die exit just above crystallization temperature (die) and high melt strength during expansion. This work studied foams properties gamma-irradiated within 0, 10, 15, 20, 25, and 30 kGy, from a LDPE exhibiting 2.6 g/10 min Melt Index. Accomplished tests: DSC, gel-fraction, swelling ratio in various solvents, rheological measurements, infra-red spectroscopy and melt strength. It was verified that within a given radiation dose range; the material exhibited an optimization in viscoelastic properties, providing the desired melt strength range for obtaining foams.

Modeling Manufacturing Impacts on Aging and Reliability of Polyurethane Foams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rao, Rekha R.; Roberts, Christine Cardinal; Mondy, Lisa Ann

Polyurethane is a complex multiphase material that evolves from a viscous liquid to a system of percolating bubbles, which are created via a CO2 generating reaction. The continuous phase polymerizes to a solid during the foaming process generating heat. Foams introduced into a mold increase their volume up to tenfold, and the dynamics of the expansion process may lead to voids and will produce gradients in density and degree of polymerization. These inhomogeneities can lead to structural stability issues upon aging. For instance, structural components in weapon systems have been shown to change shape as they age depending on theirmore » molding history, which can threaten critical tolerances. The purpose of this project is to develop a Cradle-to-Grave multiphysics model, which allows us to predict the material properties of foam from its birth through aging in the stockpile, where its dimensional stability is important.« less

Pore-level numerical analysis of the infrared surface temperature of metallic foam

NASA Astrophysics Data System (ADS)

Li, Yang; Xia, Xin-Lin; Sun, Chuang; Tan, He-Ping; Wang, Jing

2017-10-01

Open-cell metallic foams are increasingly used in various thermal systems. The temperature distributions are significant for the comprehensive understanding of these foam-based engineering applications. This study aims to numerically investigate the modeling of the infrared surface temperature (IRST) of open-cell metallic foam measured by an infrared camera placed above the sample. Two typical approaches based on Backward Monte Carlo simulation are developed to estimate the IRSTs: the first one, discrete-scale approach (DSA), uses a realistic discrete representation of the foam structure obtained from a computed tomography reconstruction while the second one, continuous-scale approach (CSA), assumes that the foam sample behaves like a continuous homogeneous semi-transparent medium. The radiative properties employed in CSA are directly determined by a ray-tracing process inside the discrete foam representation. The IRSTs for different material properties (material emissivity, specularity parameter) are computed by the two approaches. The results show that local IRSTs can vary according to the local compositions of the foam surface (void and solid). The temperature difference between void and solid areas is gradually attenuated with increasing material emissivity. In addition, the annular void space near to the foam surface behaves like a black cavity for thermal radiation, which is ensued by copious neighboring skeletons. For most of the cases studied, the mean IRSTs computed by the DSA and CSA are close to each other, except when the material emissivity is highly weakened and the sample temperature is extremely high.

NDE of Fiber Reinforced Foam Composite Structures for Future Aerospace Vehicles

NASA Technical Reports Server (NTRS)

Walker, james; Roth, Don; Hopkins, Dale

2010-01-01

This slide presentation reviews the complexities of non-destructive evaluation (NDE) of fiber reinforced foam composite structures to be used for aerospace vehicles in the future.Various views of fiber reinforced foam materials are shown and described. Conventional methods of NDE for composites are reviewed such as Micro-computed X-Ray Tomography, Thermography, Shearography, and Phased Array Ultrasonics (PAUT). These meth0ods appear to work well on the face sheet and face sheet ot core bond, they do not provide adequate coverage for the webs. There is a need for additional methods that will examine the webs and web to foam core bond.

Novel robust cellulose-based foam with pH and light dual-response for oil recovery

NASA Astrophysics Data System (ADS)

Wang, Qian; Meng, Guihua; Wu, Jianning; Wang, Yixi; Liu, Zhiyong; Guo, Xuhong

2018-05-01

We fabricated pH and light dual-responsive adsorption materials which could induce the transition of surface wettability between hydrophobicity and hydrophilicity by using ATRP. The structure and morphology of adsorption materials were confirmed by ATR-FTIR, XPS, TGA and SEM. It showed that the modified cellulose (CE)-based foam was hydrophobic, which can adsorb a range of oils and organic solvents in water under pH = 7.0 or visible light irradiation (λ > 500 nm). Meanwhile, the wettability of robust CE-based foam can convert hydrophobicity into hydrophilicity and underwater oleophobicity under pH = 3.0 or UV irradiation (λ = 365 nm), giving rise to release oils and organic solvents. Most important of all, the adsorption and desorption processes of the modified CE-based foam could be switched by external stimuli. Furthermore, the modified CE-based foam was not damaged and still retained original performance after reversible cycle repeated for many times with variation of surface wettability. In short, it indicates that CE-based foam materials with switchable surface wettability are new responsive absorbent materials and have owned potential application in the treatment of oil recovery.

Novel robust cellulose-based foam with pH and light dual-response for oil recovery

NASA Astrophysics Data System (ADS)

Wang, Qian; Meng, Guihua; Wu, Jianning; Wang, Yixi; Liu, Zhiyong; Guo, Xuhong

2018-06-01

We fabricated pH and light dual-responsive adsorption materials which could induce the transition of surface wettability between hydrophobicity and hydrophilicity by using ATRP. The structure and morphology of adsorption materials were confirmed by ATR-FTIR, XPS, TGA and SEM. It showed that the modified cellulose (CE)-based foam was hydrophobic, which can adsorb a range of oils and organic solvents in water under pH = 7.0 or visible light irradiation ( λ > 500 nm). Meanwhile, the wettability of robust CE-based foam can convert hydrophobicity into hydrophilicity and underwater oleophobicity under pH = 3.0 or UV irradiation ( λ = 365 nm), giving rise to release oils and organic solvents. Most important of all, the adsorption and desorption processes of the modified CE-based foam could be switched by external stimuli. Furthermore, the modified CE-based foam was not damaged and still retained original performance after reversible cycle repeated for many times with variation of surface wettability. In short, it indicates that CE-based foam materials with switchable surface wettability are new responsive absorbent materials and have owned potential application in the treatment of oil recovery.

Casting materials

DOEpatents

Chaudhry, Anil R [Xenia, OH; Dzugan, Robert [Cincinnati, OH; Harrington, Richard M [Cincinnati, OH; Neece, Faurice D [Lyndurst, OH; Singh, Nipendra P [Pepper Pike, OH

2011-06-14

A foam material comprises a liquid polymer and a liquid isocyanate which is mixed to make a solution that is poured, injected or otherwise deposited into a corresponding mold. A reaction from the mixture of the liquid polymer and liquid isocyanate inside the mold forms a thermally collapsible foam structure having a shape that corresponds to the inside surface configuration of the mold and a skin that is continuous and unbroken. Once the reaction is complete, the foam pattern is removed from the mold and may be used as a pattern in any number of conventional casting processes.

Method for foam encapsulating laser targets

DOEpatents

Hendricks, Charles D.

1977-01-01

Foam encapsulated laser fusion targets are made by positioning a fusion fuel-filled sphere within a mold cavity of suitable configuration and dimensions, and then filling the cavity with a material capable of producing a low density, microcellular foam, such as cellulose acetate dissolved in an acetone-based solvent. The mold assembly is dipped into an ice water bath to gel the material and thereafter soaked in the water bath to leach out undesired components, after which the gel is frozen, then freeze-dried wherein water and solvents sublime and the gel structure solidifies into a low-density microcellular foam, thereafter the resulting foam encapsulated target is removed from the mold cavity. The fuel-filled sphere is surrounded by foam having a thickness of about 10 to 100 .mu.m, a cell size of less than 2 .mu.m, and density of 0.065 to 0.6 .times. 10.sup.3 kg/m.sup.3. Various configured foam-encapsulated targets capable of being made by this encapsulation method are illustrated.

16 CFR § 1633.9 - Glossary of terms.

Code of Federal Regulations, 2013 CFR

2013-01-01

... FOR THE FLAMMABILITY (OPEN FLAME) OF MATTRESS SETS The Standard § 1633.9 Glossary of terms. (a... structure may include constructed frames, foam, box springs or other materials used alone or in combination..., solid foam core segments. ...

Structure and Compressive Properties of Invar-Cenosphere Syntactic Foams.

PubMed

Luong, Dung; Lehmhus, Dirk; Gupta, Nikhil; Weise, Joerg; Bayoumi, Mohamed

2016-02-18

The present study investigates the mechanical performance of syntactic foams produced by means of the metal powder injection molding process having an Invar (FeNi36) matrix and including cenospheres as hollow particles at weight fractions (wt.%) of 5 and 10, respectively, corresponding to approximately 41.6 and 60.0 vol.% in relation to the metal content and at 0.6 g/cm³ hollow particle density. The synthesis process results in survival of cenospheres and provides low density syntactic foams. The microstructure of the materials is investigated as well as the mechanical performance under quasi-static and high strain rate compressive loads. The compressive stress-strain curves of syntactic foams reveal a continuous strain hardening behavior in the plastic region, followed by a densification region. The results reveal a strain rate sensitivity in cenosphere-based Invar matrix syntactic foams. Differences in properties between cenosphere- and glass microsphere-based materials are discussed in relation to the findings of microstructural investigations. Cenospheres present a viable choice as filler material in iron-based syntactic foams due to their higher thermal stability compared to glass microspheres.

Ultralight anisotropic foams from layered aligned carbon nanotube sheets.

PubMed

Faraji, Shaghayegh; Stano, Kelly L; Yildiz, Ozkan; Li, Ang; Zhu, Yuntian; Bradford, Philip D

2015-10-28

In this work, we present large scale, ultralight aligned carbon nanotube (CNT) structures which have densities an order of magnitude lower than CNT arrays, have tunable properties and exhibit resiliency after compression. By stacking aligned sheets of carbon nanotubes and then infiltrating with a pyrolytic carbon (PyC), resilient foam-like materials were produced that exhibited complete recovery from 90% compressive strain. With density as low as 3.8 mg cm(-3), the foam structure is over 500 times less dense than bulk graphite. Microscopy revealed that PyC coated the junctions among CNTs, and also increased CNT surface roughness. These changes in the morphology explain the transition from inelastic behavior to foam-like recovery of the layered CNT sheet structure. Mechanical and thermal properties of the foams were tuned for different applications through variation of PyC deposition duration while dynamic mechanical analysis showed no change in mechanical properties over a large temperature range. Observation of a large and linear electrical resistance change during compression of the aligned CNT/carbon (ACNT/C) foams makes strain/pressure sensors a relevant application. The foams have high oil absorption capacities, up to 275 times their own weight, which suggests they may be useful in water treatment and oil spill cleanup. Finally, the ACNT/C foam's high porosity, surface area and stability allow for demonstration of the foams as catalyst support structures.

Microstructure and Deformation Response of TRIP-Steel Syntactic Foams to Quasi-Static and Dynamic Compressive Loads

PubMed Central

Ehinger, David; Weise, Jörg; Baumeister, Joachim; Funk, Alexander; Krüger, Lutz; Martin, Ulrich

2018-01-01

The implementation of hollow S60HS glass microspheres and Fillite 106 cenospheres in a martensitically transformable AISI 304L stainless steel matrix was realized by means of metal injection molding of feedstock with varying fractions of the filler material. The so-called TRIP-steel syntactic foams were studied with respect to their behavior under quasi-static compression and dynamic impact loading. The interplay between matrix material behavior and foam structure was discussed in relation to the findings of micro-structural investigations, electron back scatter diffraction EBSD phase analyses and magnetic measurements. During processing, the cenospheres remained relatively stable retaining their shape while the glass microspheres underwent disintegration associated with the formation of pre-cracked irregular inclusions. Consequently, the AISI 304L/Fillite 106 syntactic foams exhibited a higher compression stress level and energy absorption capability as compared to the S60HS-containing variants. The α′ -martensite kinetic of the steel matrix was significantly influenced by material composition, strain rate and arising deformation temperature. The highest ferromagnetic α′-martensite phase fraction was detected for the AISI 304L/S60HS batches and the lowest for the TRIP-steel bulk material. Quasi-adiabatic sample heating, a gradual decrease in strain rate and an enhanced degree of damage controlled the mechanical deformation response of the studied syntactic foams under dynamic impact loading. PMID:29695107

Microstructure and Deformation Response of TRIP-Steel Syntactic Foams to Quasi-Static and Dynamic Compressive Loads.

PubMed

Ehinger, David; Weise, Jörg; Baumeister, Joachim; Funk, Alexander; Waske, Anja; Krüger, Lutz; Martin, Ulrich

2018-04-24

The implementation of hollow S60HS glass microspheres and Fillite 106 cenospheres in a martensitically transformable AISI 304L stainless steel matrix was realized by means of metal injection molding of feedstock with varying fractions of the filler material. The so-called TRIP-steel syntactic foams were studied with respect to their behavior under quasi-static compression and dynamic impact loading. The interplay between matrix material behavior and foam structure was discussed in relation to the findings of micro-structural investigations, electron back scatter diffraction EBSD phase analyses and magnetic measurements. During processing, the cenospheres remained relatively stable retaining their shape while the glass microspheres underwent disintegration associated with the formation of pre-cracked irregular inclusions. Consequently, the AISI 304L/Fillite 106 syntactic foams exhibited a higher compression stress level and energy absorption capability as compared to the S60HS-containing variants. The α ′ -martensite kinetic of the steel matrix was significantly influenced by material composition, strain rate and arising deformation temperature. The highest ferromagnetic α ′ -martensite phase fraction was detected for the AISI 304L/S60HS batches and the lowest for the TRIP-steel bulk material. Quasi-adiabatic sample heating, a gradual decrease in strain rate and an enhanced degree of damage controlled the mechanical deformation response of the studied syntactic foams under dynamic impact loading.

Ultimate strength capacity of a square hollow section filled with fibrous foamed concrete

NASA Astrophysics Data System (ADS)

Amirah Azra Khairuddin, Siti; Rahman, Norashidah Abd; Jamaluddin, Norwati; Jaini, Zainorizuan Mohd; Ali, Noorwirdawati

2017-11-01

Concrete-filled sections used as building columns have become popular due to their architectural and structural elements. In recent years, there has been a renewed call for the improvement of materials used as concrete to fill the composite columns. Among these materials, foamed concrete has received great attention due to its structural characteristics and its potential as a construction material used in hollow sections. However, its behaviors as infill material in a hollow section, such as its strength and failure mode, should be investigated. In this study, experimental research was conducted to compare the experimental and theoretical values of its ultimate strength capacity. Eight specimens of hollow steel sections with two different thicknesses were filled with fibrous foamed concrete and then subjected to compression load. The obtained results were compared with those obtained from a hollow section with the same thicknesses, but were filled with normal foamed concrete. Results show that the ultimate strength capacity of the experimental value is the same as that of the theoretical value based on Eurocode 4. The largest percentage values between theoretical and experimental results for thicknesses of 2 and 4 mm are 58% and 55%, respectively.

Stress wave propagation and mitigation in two polymeric foams

NASA Astrophysics Data System (ADS)

Pradel, Pierre; Malaise, Frederic; Cadilhon, Baptiste; Quessada, Jean-Hugues; de Resseguier, Thibaut; Delhomme, Catherine; Le Blanc, Gael

2017-06-01

Polymeric foams are widely used in industry for thermal insulation or shock mitigation. This paper investigates the ability of a syntactic epoxy foam and an expanded polyurethane foam to mitigate intense (several GPa) and short duration (<10-6 s) stress pulses. Plate impact and electron beam irradiation experiments have been conducted to study the dynamic mechanical responses of both foams. Interferometer Doppler Laser method is used to record the target rear surface velocity. A two-wave structure associated with the propagation of an elastic precursor followed by the compaction of the pores has been observed. The compaction stress level deduced from the velocity measurement is a good indicator of mitigation capability of the foams. Quasi-static tests and dynamic soft recovery experiments have also been performed to determine the compaction mechanisms. In the polyurethane foam, the pores are closed by elastic buckling of the matrix and damage of the structure. In the epoxy foam, the compaction is due to the crushing of glass microspheres. Two porous material models successfully represent the macroscopic response of these polymeric foams.

Fabrication of Aluminum Foam-Filled Thin-Wall Steel Tube by Friction Welding and Its Compression Properties.

PubMed

Hangai, Yoshihiko; Saito, Masaki; Utsunomiya, Takao; Kitahara, Soichiro; Kuwazuru, Osamu; Yoshikawa, Nobuhiro

2014-09-19

Aluminum foam has received considerable attention in various fields and is expected to be used as an engineering material owing to its high energy absorption properties and light weight. To improve the mechanical properties of aluminum foam, combining it with dense tubes, such as aluminum foam-filled tubes, was considered necessary. In this study, an aluminum foam-filled steel tube, which consisted of ADC12 aluminum foam and a thin-wall steel tube, was successfully fabricated by friction welding. It was shown that a diffusion bonding layer with a thickness of approximately 10 μm was formed, indicating that strong bonding between the aluminum foam and the steel tube was realized. By the X-ray computed tomography observation of pore structures, the fabrication of an aluminum foam-filled tube with almost uniform pore structures over the entire specimen was confirmed. In addition, it was confirmed that the aluminum foam-filled steel tube exhibited mechanical properties superior to those of the ADC12 aluminum foam and steel tube. This is considered to be attributed to the combination of the aluminum foam and steel tube, which particularly prevents the brittle fracture and collapse of the ADC12 foam by the steel tube, along with the strong metal bonding between the aluminum foam and the steel tube.

Ag Nanoparticles-Modified 3D Graphene Foam for Binder-Free Electrodes of Electrochemical Sensors.

PubMed

Han, Tao; Jin, Jianli; Wang, Congxu; Sun, Youyi; Zhang, Yinghe; Liu, Yaqing

2017-02-16

Ag nanoparticles-modified 3D graphene foam was synthesized through a one-step in-situ approach and then directly applied as the electrode of an electrochemical sensor. The composite foam electrode exhibited electrocatalytic activity towards Hg(II) oxidation with high limit of detection and sensitivity of 0.11 μM and 8.0 μA/μM, respectively. Moreover, the composite foam electrode for the sensor exhibited high cycling stability, long-term durability and reproducibility. These results were attributed to the unique porous structure of the composite foam electrode, which enabled the surface of Ag nanoparticles modified reduced graphene oxide (Ag NPs modified rGO) foam to become highly accessible to the metal ion and provided more void volume for the reaction with metal ion. This work not only proved that the composite foam has great potential application in heavy metal ions sensors, but also provided a facile method of gram scale synthesis 3D electrode materials based on rGO foam and other electrical active materials for various applications.

Ag Nanoparticles-Modified 3D Graphene Foam for Binder-Free Electrodes of Electrochemical Sensors

PubMed Central

Han, Tao; Jin, Jianli; Wang, Congxu; Sun, Youyi; Zhang, Yinghe; Liu, Yaqing

2017-01-01

Ag nanoparticles-modified 3D graphene foam was synthesized through a one-step in-situ approach and then directly applied as the electrode of an electrochemical sensor. The composite foam electrode exhibited electrocatalytic activity towards Hg(II) oxidation with high limit of detection and sensitivity of 0.11 µM and 8.0 µA/µM, respectively. Moreover, the composite foam electrode for the sensor exhibited high cycling stability, long-term durability and reproducibility. These results were attributed to the unique porous structure of the composite foam electrode, which enabled the surface of Ag nanoparticles modified reduced graphene oxide (Ag NPs modified rGO) foam to become highly accessible to the metal ion and provided more void volume for the reaction with metal ion. This work not only proved that the composite foam has great potential application in heavy metal ions sensors, but also provided a facile method of gram scale synthesis 3D electrode materials based on rGO foam and other electrical active materials for various applications. PMID:28336878

Material heterogeneity in cancellous bone promotes deformation recovery after mechanical failure

PubMed Central

Torres, Ashley M.; Matheny, Jonathan B.; Keaveny, Tony M.; Taylor, David; Rimnac, Clare M.; Hernandez, Christopher J.

2016-01-01

Many natural structures use a foam core and solid outer shell to achieve high strength and stiffness with relatively small amounts of mass. Biological foams, however, must also resist crack growth. The process of crack propagation within the struts of a foam is not well understood and is complicated by the foam microstructure. We demonstrate that in cancellous bone, the foam-like component of whole bones, damage propagation during cyclic loading is dictated not by local tissue stresses but by heterogeneity of material properties associated with increased ductility of strut surfaces. The increase in surface ductility is unexpected because it is the opposite pattern generated by surface treatments to increase fatigue life in man-made materials, which often result in reduced surface ductility. We show that the more ductile surfaces of cancellous bone are a result of reduced accumulation of advanced glycation end products compared with the strut interior. Damage is therefore likely to accumulate in strut centers making cancellous bone more tolerant of stress concentrations at strut surfaces. Hence, the structure is able to recover more deformation after failure and return to a closer approximation of its original shape. Increased recovery of deformation is a passive mechanism seen in biology for setting a broken bone that allows for a better approximation of initial shape during healing processes and is likely the most important mechanical function. Our findings suggest a previously unidentified biomimetic design strategy in which tissue level material heterogeneity in foams can be used to improve deformation recovery after failure. PMID:26929343

Casting Protocols for the Production of Open Cell Aluminum Foams by the Replication Technique and the Effect on Porosity

PubMed Central

Elizondo Luna, Erardo M.; Barari, Farzad; Woolley, Robert; Goodall, Russell

2014-01-01

Metal foams are interesting materials from both a fundamental understanding and practical applications point of view. Uses have been proposed, and in many cases validated experimentally, for light weight or impact energy absorbing structures, as high surface area heat exchangers or electrodes, as implants to the body, and many more. Although great progress has been made in understanding their structure-properties relationships, the large number of different processing techniques, each producing material with different characteristics and structure, means that understanding of the individual effects of all aspects of structure is not complete. The replication process, where molten metal is infiltrated between grains of a removable preform material, allows a markedly high degree of control and has been used to good effect to elucidate some of these relationships. Nevertheless, the process has many steps that are dependent on individual “know-how”, and this paper aims to provide a detailed description of all stages of one embodiment of this processing method, using materials and equipment that would be relatively easy to set up in a research environment. The goal of this protocol and its variants is to produce metal foams in an effective and simple way, giving the possibility to tailor the outcome of the samples by modifying certain steps within the process. By following this, open cell aluminum foams with pore sizes of 1–2.36 mm diameter and 61% to 77% porosity can be obtained. PMID:25548938

Numerical modelling of closed-cell aluminium foam under dynamic loading

NASA Astrophysics Data System (ADS)

Hazell, Paul; Kader, M. A.; Islam, M. A.; Escobedo, J. P.; Saadatfar, M.

2015-06-01

Closed-cell aluminium foams are extensively used in aerospace and automobile industries. The understanding of their behaviour under impact loading conditions is extremely important since impact problems are directly related to design of these engineering structures. This research investigates the response of a closed-cell aluminium foam (CYMAT) subjected to dynamic loading using the finite element software ABAQUS/explicit. The aim of this research is to numerically investigate the material and structural properties of closed-cell aluminium foam under impact loading conditions with interest in shock propagation and its effects on cell wall deformation. A μ-CT based 3D foam geometry is developed to simulate the local cell collapse behaviours. A number of numerical techniques are applied for modelling the crush behaviour of aluminium foam to obtain the more accurate results. The simulation results are compared with experimental data. Comparison of the results shows a good correlation between the experimental results and numerical predictions.

Inhibition of Microbial Growth by Fatty Amine Catalysts from Polyurethane Foam Test Tube Plugs

PubMed Central

Bach, John A.; Wnuk, Richard J.; Martin, Delano G.

1975-01-01

When polyurethane foam test tube plugs are autoclaved, they release volatile fatty amines that inhibit the growth of some microorganisms. The chemical structures of these amines were determined by the use of a gas chromatographmass spectrometer. They are catalysts used to produce the foam. The problem of contaminating growth media with toxic substances released from polymeric materials is discussed. PMID:1096816

Effects of porosity distribution and porosity volume fraction on the electromechanical properties of 3-3 piezoelectric foams

NASA Astrophysics Data System (ADS)

Nguyen, B. V.; Challagulla, K. S.; Venkatesh, T. A.; Hadjiloizi, D. A.; Georgiades, A. V.

2016-12-01

Unit-cell based finite element models are developed to completely characterize the role of porosity distribution and porosity volume fraction in determining the elastic, dielectric and piezoelectric properties as well as relevant figures of merit of 3-3 type piezoelectric foam structures. Eight classes of foam structures which represent structures with different types and degrees of uniformity of porosity distribution are identified; a Base structure (Class I), two H-type foam structures (Classes II, and III), a Cross-type foam structure (Class IV) and four Line-type foam structures (Classes V, VI, VII, and VIII). Three geometric factors that influence the electromechanical properties are identified: (i) the number of pores per face, pore size and the distance between the pores; (ii) pore orientation with respect to poling direction; (iii) the overall symmetry of the pore distribution with respect to the center of the face of the unit cell. To assess the suitability of these structures for such applications as hydrophones, bone implants, medical imaging and diagnostic devices, five figures of merit are determined via the developed finite element model; the piezoelectric coupling constant (K t ), the acoustic impedance (Z), the piezoelectric charge coefficient (d h ), the hydrostatic voltage coefficient (g h ), and the hydrostatic figure of merit (d h g h ). At high material volume fractions, foams with non-uniform Line-type porosity (Classes V and VII) where the pores are preferentially distributed perpendicular to poling direction, are found to exhibit the best combination of desirable piezoelectric figures of merit. For example, at about 50% volume fraction, the d h , g h , and d h g h figures of merit are 55%, 1600% and 2500% higher, respectively, for Classes V and VII of Line-like foam structures compared with the Base structure.

Synergistic effects from graphene and carbon nanotubes endow ordered hierarchical structure foams with a combination of compressibility, super-elasticity and stability and potential application as pressure sensors.

PubMed

Kuang, Jun; Dai, Zhaohe; Liu, Luqi; Yang, Zhou; Jin, Ming; Zhang, Zhong

2015-01-01

Nanostructured carbon material based three-dimensional porous architectures have been increasingly developed for various applications, e.g. sensors, elastomer conductors, and energy storage devices. Maintaining architectures with good mechanical performance, including elasticity, load-bearing capacity, fatigue resistance and mechanical stability, is prerequisite for realizing these functions. Though graphene and CNT offer opportunities as nanoscale building blocks, it still remains a great challenge to achieve good mechanical performance in their microarchitectures because of the need to precisely control the structure at different scales. Herein, we fabricate a hierarchical honeycomb-like structured hybrid foam based on both graphene and CNT. The resulting materials possess excellent properties of combined high specific strength, elasticity and mechanical stability, which cannot be achieved in neat CNT and graphene foams. The improved mechanical properties are attributed to the synergistic-effect-induced highly organized, multi-scaled hierarchical architectures. Moreover, with their excellent electrical conductivity, we demonstrated that the hybrid foams could be used as pressure sensors in the fields related to artificial skin.

X-ray micro computed tomography characterization of cellular SiC foams for their applications in chemical engineering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ou, Xiaoxia

Open-cell SiC foams clearly are promising materials for continuous-flow chemical applications such as heterogeneous catalysis and distillation. X-ray micro computed tomography characterization of cellular β-SiC foams at a spatial voxel size of 13.6{sup 3} μm{sup 3} and the interpretation of morphological properties of SiC open-cell foams with implications to their transport properties are presented. Static liquid hold-up in SiC foams was investigated through in-situ draining experiments for the first time using the μ-CT technique providing thorough 3D information about the amount and distribution of liquid hold-up inside the foam. This will enable better modeling and design of structured reactors basedmore » on SiC foams in the future. In order to see more practical uses, μ-CT data of cellular foams must be exploited to optimize the design of the morphology of foams for a specific application. - Highlights: •Characterization of SiC foams using novel X-ray micro computed tomography. •Interpretation of structural properties of SiC foams regarding to their transport properties. •Static liquid hold-up analysis of SiC foams through in-situ draining experiments.« less

Acoustic characterisation of liquid foams with an impedance tube.

PubMed

Pierre, Juliette; Guillermic, Reine-Marie; Elias, Florence; Drenckhan, Wiebke; Leroy, Valentin

2013-10-01

Acoustic measurements provide convenient non-invasive means for the characterisation of materials. We show here for the first time how a commercial impedance tube can be used to provide accurate measurements of the velocity and attenuation of acoustic waves in liquid foams, as well as their effective "acoustic" density, over the 0.5-6kHz frequency range. We demonstrate this using two types of liquid foams: a commercial shaving foam and "home-made" foams with well-controlled physico-chemical and structural properties. The sound velocity in the latter foams is found to be independent of the bubble size distribution and is very well described by Wood's law. This implies that the impedance technique may be a convenient way to measure in situ the density of liquid foams. Important questions remain concerning the acoustic attenuation, which is found to be influenced in a currently unpredictible manner by the physico-chemical composition and the bubble size distribution of the characterised foams. We confirm differences in sound velocities in the two types of foams (having the same structural properties) which suggests that the physico-chemical composition of liquid foams has a non-negligible effect on their acoustic properties.

Multifunctional Stiff Carbon Foam Derived from Bread.

PubMed

Yuan, Ye; Ding, Yujie; Wang, Chunhui; Xu, Fan; Lin, Zaishan; Qin, Yuyang; Li, Ying; Yang, Minglong; He, Xiaodong; Peng, Qingyu; Li, Yibin

2016-07-06

The creation of stiff yet multifunctional three-dimensional porous carbon architecture at very low cost is still challenging. In this work, lightweight and stiff carbon foam (CF) with adjustable pore structure was prepared by using flour as the basic element via a simple fermentation and carbonization process. The compressive strength of CF exhibits a high value of 3.6 MPa whereas its density is 0.29 g/cm(3) (compressive modulus can be 121 MPa). The electromagnetic interference (EMI) shielding effectiveness measurements (specific EMI shielding effectiveness can be 78.18 dB·cm(3)·g(-1)) indicate that CF can be used as lightweight, effective shielding material. Unlike ordinary foam structure materials, the low thermal conductivity (lowest is 0.06 W/m·K) with high resistance to fire makes CF a good candidate for commercial thermal insulation material. These results demonstrate a promising method to fabricate an economical, robust carbon material for applications in industry as well as topics regarding environmental protection and improvement of energy efficiency.

3D-Printing ‘Smarter’ Energy Absorbing Materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Duoss, Eric

2014-08-29

Foams are, by nature, disordered materials studded with air pockets of varying sizes. Lack of control over the material’s architecture at the micrometer or nanometer scale can make it difficult to adjust the foam’s basic properties. But Eric Duoss and a team of Livermore researchers are using additive manufacturing to develop “smarter” silicone cushions. By architecting the structure at the micro scale, they are able to control macro-scale properties previously unachievable with foam materials.

Rigid closed-cell polyimide foams for aircraft applications and foam-in-place technology

NASA Technical Reports Server (NTRS)

Gagliani, J.; Straub, P.; Gagliani, J., Jr.

1983-01-01

Significant accomplishments generated are summarized. Testing of closed cell foams, which has resulted in the characterization of compositions which produce rigid foams for use in galley structure applications is reported. It is shown that the density, compressive strength and shear strength of the foams are directly related to the concentrations of the microballoons. The same properties are also directly related to the resin loading. Prototype samples of rigid closed cell foams meeting the requirements of the program were submitted. Investigation of the apparatus to produce polyimide foams using foam in place techniques, resulted in the selection of a spray gun apparatus, capable to deliver a mixture of microballoons and resin binder on substrates which cures to yield a closed cell foam. It is found that the adhesion of the foam on aluminum, titanium and steel substrates is satisfactory. It is concluded that the material meets the mechanical and thermal requirements of the program.

Manufacturing and Characterization of Temperature-Stable, Novel, Viscoelastic Polyurea Based Foams for Impact Management

NASA Astrophysics Data System (ADS)

Ramirez, Brian Josue

The aim of this thesis was to develop advance, high performance polyurea foams for multi-hit capability in protective equipment that respond over a range of impact energies, temperatures, and strain rates. In addition, the microstructure of these materials should be tunable such that the peak stress (or force) transmitted across the foam section can be limited to a specific value defined by an injury threshold while maximizing impact energy absorption. Novel polyurea foams were manufactured and found to exhibit a reversible viscoelastic shear deformation at the molecular level. The intrinsic shear dissipation process is synergistically coupled to controlled collapse of a novel pore structure. The microstructure compromises of stochastic polyhedral cells ranging from 200 - 500 mum with perforated membranes with small apertures ( 20 mum). This makes them strain rate sensitive as the rate at which the air escapes the cells depend upon the loading rate. These mechanisms operate simultaneously and sequentially, thereby significantly reducing the transmitted impact forces across the foam section. Thus, they behave as an elastically modulated layered composite because the cells stiffen or soften in response to the changing loading rate. Therefore, the newly developed polyurea foams are able to manage the varying material strain rate that occurs within the same loading event without the need to modulate the stiffness or density. Additionally, polyurea foams were found to retain its excellent impact properties over a range of temperatures (0°C to 40°C) by having a glass transition temperature well below 0°C. This is in contrast to commercially available high performance foams that have the glass transition temperature near 0°C and absorb energy through phase transformation at ambient conditions, but significantly stiffen at lower temperatures, and dramatically soften at higher temperatures. This expands the application domain of polyurea foam material considerably as it can be tailored to withstand a range of dynamic forces and impact velocities, showing further improvement over currently used protective foams. This thesis also presents a new composite foam concept that involves infiltrating a polyurea-based foam through an open 3D lattice structure with a truss-like network of 2 mm-size struts. The combination of dynamic buckling at the macro (preform lattice struts) and the micro (foam pores) levels increases the stiffness and plateau strength of the composite polyurea foam. The composite foams absorb more impact energy in same section thickness, while keeping both the peak stress and impulse duration low compared to high performance expanded polystyrene (EPS) and Poron foam technology, but without the material crushing or undergoing phase shift, respectively. Most importantly, the composite foams display stability at both low (0°C) and high temperatures (40°C) because of its extremely low Tg of -50°C. Being viscoelastic, they recover fully within 30 s after each impact, without loss of any energy absorption capability. These properties should allow these materials to have a wide range of military and civilian applications, especially in advance armors and protective body and headgear systems.

Properties of rigid polyurethane foams filled with glass microspheres

NASA Astrophysics Data System (ADS)

Yakushin, V.; Bel'kova, L.; Sevastyanova, I.

2012-11-01

The effect of hollow glass microspheres with a density of 125 kg/m3 on the properties of low-density (54-90 kg/m3) rigid polyurethane foams is investigated. The thermal expansion coefficient of the foams and their properties in tension and compression in relation to the content of the microspheres (0.5-5 wt.%) are determined. An increase in the characteristics of the material in compression in the foam rise direction with increasing content of filler is revealed. The limiting content of the microspheres above which the mechanical characteristics of the filled foams begin to decrease is found. The distribution of the microspheres in elements of the cellular structure of the polyurethane foams is examined.

A study of tensile test on open-cell aluminum foam sandwich

NASA Astrophysics Data System (ADS)

Ibrahim, N. A.; Hazza, M. H. F. Al; Adesta, E. Y. T.; Abdullah Sidek, Atiah Bt.; Endut, N. A.

2018-01-01

Aluminum foam sandwich (AFS) panels are one of the growing materials in the various industries because of its lightweight behavior. AFS also known for having excellent stiffness to weight ratio and high-energy absorption. Due to their advantages, many researchers’ shows an interest in aluminum foam material for expanding the use of foam structure. However, there is still a gap need to be fill in order to develop reliable data on mechanical behavior of AFS with different parameters and analysis method approach. Least of researcher focusing on open-cell aluminum foam and statistical analysis. Thus, this research conducted by using open-cell aluminum foam core grade 6101 with aluminum sheets skin tested under tension. The data is analyzed using full factorial in JMP statistical analysis software (version 11). ANOVA result show a significant value of the model which less than 0.500. While scatter diagram and 3D plot surface profiler found that skins thickness gives a significant impact to stress/strain value compared to core thickness.

46 CFR 160.035-1 - Applicable specifications.

Code of Federal Regulations, 2010 CFR

2010-10-01

... Laminates, Fibrous Glass Reinforced, Marine Structural. MIL-P-19644—Plastic Foam, Molded Polystyrene..., Polyester, Low Pressure Laminating, Fire Retardant. MIL-P-21929—Plastic Material, Cellular Polyurethane, Rigid, Foam-In-Place, Low Density. (3) Federal specifications: TT-P-59—Paint, Ready-Mixed, International...

46 CFR 160.035-1 - Applicable specifications.

Code of Federal Regulations, 2011 CFR

2011-10-01

... Laminates, Fibrous Glass Reinforced, Marine Structural. MIL-P-19644—Plastic Foam, Molded Polystyrene..., Polyester, Low Pressure Laminating, Fire Retardant. MIL-P-21929—Plastic Material, Cellular Polyurethane, Rigid, Foam-In-Place, Low Density. (3) Federal specifications: TT-P-59—Paint, Ready-Mixed, International...

An approach for characterising cellular polymeric foam structures using computed tomography

NASA Astrophysics Data System (ADS)

Chen, Youming; Das, Raj; Battley, Mark

2018-02-01

Global properties of foams depend on foam base materials and microstructures. Characterisation of foam microstructures is important for developing numerical foam models. In this study, the microstructures of four polymeric structural foams were imaged using a micro-CT scanner. Image processing and analysis methods were proposed to quantify the relative density, cell wall thickness and cell size of these foams from the captured CT images. Overall, the cells in these foams are fairly isotropic, and cell walls are rather straight. The measured average relative densities are in good agreement with the actual values. Relative density, cell size and cell wall thickness in these foams are found to vary along the thickness of foam panel direction. Cell walls in two of these foams are found to be filled with secondary pores. In addition, it is found that the average cell wall thickness measured from 2D images is around 1.4 times of that measured from 3D images, and the average cell size measured from 3D images is 1.16 times of that measured from 2D images. The distributions of cell wall thickness and cell size measured from 2D images exhibit lager dispersion in comparison to those measured from 3D images.

Experimental characterization of fire-induced response of rigid polyurethane foam

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chu, T.Y.; Gill, W.; Moore, J.W.

1995-12-31

Reported is the result of an experimental investigation of fire-induced response of a 96 kg/m{sup 3} closed cell rigid polyurethane foam. The specimen is 0.37 m in diameter, and 152 mm thick, placed in a cylindrical test vessel. The fire condition is simulated by heating the bottom of the test vessel to 1283 K using a radiant heat source. Real-time x-ray shows that the degradation process involves the progression of a charring front into the virgin material. The charred region has a regular and graded structure consisting of a packed bubble outer layer and successive layers of thin shells. Themore » layer-to-layer permeability appears to be poor. There are indications that gas vents laterally. The shell-like structure might be the result of lateral venting. Although the foam degradation process is quite complicated, the in-depth temperature responses in the uncharted foam appear to be consistent with steady state ablation. The measured temperature responses are well represented by the exponential distribution for steady state ablation. An estimate of the thermal diffusivity of the foam is obtained from the ablation model. The experiment is part of a more comprehensive program to develop material response models of foams and encapsulants.« less

Self-Assembly of Porous Boron Nitride Microfibers into Ultralight Multifunctional Foams of Large Sizes.

PubMed

Lin, Jing; Yuan, Xiaohai; Li, Gen; Huang, Yang; Wang, Weijia; He, Xin; Yu, Chao; Fang, Yi; Liu, Zhenya; Tang, Chengchun

2017-12-27

As a kind of macroscopic boron nitride (BN) architectures, ultralight BN cellular materials with high porosity and great resilience would have a broad range of applications in energy and environment areas. However, creating such BN cellular materials in large sizes has still been proven challenging. Here, we report on the unique self-assembly of one-dimensional porous BN microfibers into an integral three-dimensional BN foam with open-cell cellular architectures. An ultrasonic-assisted self-assembly, freeze-drying, and high-temperature pyrolysis process has been developed for the preparation of cellular BN foam with a large size and desired shape. The developed BN foam has low density, high porosity (∼99.3%), great resilience, and excellent hydrophobic-lipophilic nature. The foam also exhibits excellent absorption capacities for a wide range of organic solvents and oils (wt % of ∼5130-7820%), as well as a high recovery efficiency (∼94%). Moreover, the unique hierarchical porous structure enables the foam to demonstrate a very low thermal conductivity (∼0.035 W/K/m). The excellent thermal insulation performance, superior mechanical property, and superb chemical and thermal stability enable the developed BN foam as an integrating multifunctional material in a broad range of high-end applications.

Fabrication of Aluminum Foam-Filled Thin-Wall Steel Tube by Friction Welding and Its Compression Properties

PubMed Central

Hangai, Yoshihiko; Saito, Masaki; Utsunomiya, Takao; Kitahara, Soichiro; Kuwazuru, Osamu; Yoshikawa, Nobuhiro

2014-01-01

Aluminum foam has received considerable attention in various fields and is expected to be used as an engineering material owing to its high energy absorption properties and light weight. To improve the mechanical properties of aluminum foam, combining it with dense tubes, such as aluminum foam-filled tubes, was considered necessary. In this study, an aluminum foam-filled steel tube, which consisted of ADC12 aluminum foam and a thin-wall steel tube, was successfully fabricated by friction welding. It was shown that a diffusion bonding layer with a thickness of approximately 10 μm was formed, indicating that strong bonding between the aluminum foam and the steel tube was realized. By the X-ray computed tomography observation of pore structures, the fabrication of an aluminum foam-filled tube with almost uniform pore structures over the entire specimen was confirmed. In addition, it was confirmed that the aluminum foam-filled steel tube exhibited mechanical properties superior to those of the ADC12 aluminum foam and steel tube. This is considered to be attributed to the combination of the aluminum foam and steel tube, which particularly prevents the brittle fracture and collapse of the ADC12 foam by the steel tube, along with the strong metal bonding between the aluminum foam and the steel tube. PMID:28788213

Processing of large grain Y-123 superconductors with pre-defined porous structures

NASA Astrophysics Data System (ADS)

Sudhakar Reddy, E.; Babu, N. Hari; Shi, Y.; Cardwell, D. A.; Schmitz, G. J.

2005-02-01

Porous superconductors have inherent cooling advantages over their bulk counterparts and, as a result, are emerging as an important class of materials for practical applications. Single-domain Y-Ba-Cu-O (YBCO) foams processed with a pre-defined, open porous structure, for example, have significant potential for use as elements in resistive superconducting fault current limiters. In this case, the interconnected porosity is ideal for producing reinforced composites with improved mechanical and heat conducting properties. In this paper we describe a few simple methods for fabricating large grain YBCO superconductors with various predefined porous structures via an infiltration process from tailored, porous Y2BaCuO5 (Y-211) pre-forms manufactured by a variety of techniques, including slurry-coating of standard polyurethane foams to replicate their structure. Foams produced by this method typically have a strut thickness of a few hundred µm and pore sizes ranging from 10 to 100 pores per inch (PPI). Foams with increased strut thickness of up to millimetre dimensions can be produced by embedding organic ball spacers within the Y-211 pre-form followed by a burn-out and sintering process. Single-domain YBCO bulk materials with cellular and pre-defined 3D interconnected porosity may be produced by a similar process using tailored wax structures in Y-211 castings.

Experimental study on nonlinear vibrating of aluminum foam using electronic speckle pattern interferometry

NASA Astrophysics Data System (ADS)

Yang, Fujun; Ma, Yinhang; Tao, Nan; He, Xiaoyuan

2017-06-01

Due to its multi properties, including excellent stiffness-to-weight and strength-to-weight ratios, closed-cell aluminum and its alloy foams become candidate materials for use in many high-technology industries, such as the automotive and aerospace industries. For the efficient use of closed-cell foams in structural applications, it is necessary and important to detailly understand their mechanical characteristics. In this paper, the nonlinear vibration responses of the cantilever beams of closed-cell aluminum foams were investigated by use of electronic speckle pattern interferometry (ESPI). The nonlinear resonant mode shapes of testing specimens under harmonic excitation were measured. It is first time to obtain from the experimental results that there exist super-harmonic responses when the cantilever beams of closed-cell aluminum foam were forced to vibrate, which was caused by its specific cellular structures.

Effect of the carbonyl iron particles on acoustic absorption properties of magnetic polyurethane foam

NASA Astrophysics Data System (ADS)

Geng, Jialu; Wang, Caiping; Zhu, Honglang; Wang, Xiaojie

2018-03-01

Elastomeric matrix embedded with magnetic micro-sized particles has magnetically controllable properties, which has been investigated extensively in the last decades. In this study we develop a new magnetically controllable elastomeric material for acoustic applications at lower frequencies. The soft polyurethane foam is used as matrix material due to its extraordinary elastic and acoustic absorption properties. One-step method is used to synthesize polyurethane foam, in which all components including polyether polyols 330N, MDI, deionized water, silicone oil, carbonyl iron particle (CIP) and catalyst are put into one container for curing. Changing any component can induce the change of polyurethane foam's properties, such as physical and acoustic properties. The effect of the content of MDI on acoustic absorption is studied. The CIPs are aligned under extra magnetic field during the foaming process. And the property of polyurethane foam with aligned CIPs is also investigated. Scanning electron microscope (SEM) is used to observe the structure of pore and particle-chain. The two-microphone impedance tube and the transfer function method are used to test acoustic absorption property of the magnetic foams.

Mechanical properties of heat-treated organic foams

NASA Astrophysics Data System (ADS)

Amaral-Labat, G.; Sahimi, Muhammad; Pizzi, A.; Fierro, V.; Celzard, Alain

2013-03-01

The mechanical properties of a class of cellular material were measured. The composition of the material was progressively modified, while its pore structure was kept unchanged. Rigid foam, prepared from a thermoset resin, was gradually converted into reticulated vitreous carbon foam by pyrolysis at increasingly higher heat-treatment temperatures (HHT). The corresponding changes in the Young's modulus Y and the compressive strength σ of the materials were measured over a wide range of porosities. The materials exhibit a percolation behavior with a zero percolation threshold. At very low densities the Young's modulus and the compressive strength appear to follow the power laws predicted by percolation theory near the percolation threshold. But, whereas the exponent τ associated with the power-law behavior of Y appears to vary significantly with the material's density and the HHT, the exponent associated with σ does not change much. The possible cause of the apparent and surprising nonuniversality of τ is discussed in detail, in the light of the fact that only the materials’ composition varies, not the structure of their pore space that could have caused the nonuniversality.

Effects of ultrasound on polymeric foam porosity.

PubMed

Torres-Sanchez, C; Corney, J R

2008-04-01

A variety of materials require functionally graded cellular microstructures whose porosity is engineered to meet specific applications (e.g. mimic bone structure for orthopaedic applications; fulfil mechanical, thermal or acoustic constraints in structural foamed components, etc.). Although a huge variety of foams can be manufactured with homogenous porosity, there are no generic processes for controlling the distribution of porosity within the resulting matrix. Motivated by the desire to create a flexible process for engineering heterogeneous foams, the authors have investigated how ultrasound, applied during the formation of a polyurethane foam, affects its cellular structure. The experimental results demonstrated how the parameters of ultrasound exposure (i.e. frequency and applied power) influenced the volume and distribution of pores within the final polyurethane matrix: the data demonstrates that porosity (i.e. volume fraction) varies in direct proportion to both the acoustic pressure and frequency of the ultrasound signal. The effects of ultrasound on porosity demonstrated by this work offer the prospect of a manufacturing process that can adjust the cellular geometry of foam and hence ensure that the resulting characteristics match the functional requirements.

Multi-layer structures with thermal and acoustic properties for building rehabilitation

NASA Astrophysics Data System (ADS)

Bessa, J.; Mota, C.; Cunha, F.; Merino, F.; Fangueiro, R.

2017-10-01

This work compares the use of different sustainable materials in the design of multilayer structures for the rehabilitation of buildings in terms of thermal and acoustic properties. These structures were obtained by compression moulding and thermal and acoustic tests were further carried out for the quantification of the respective insulation properties of composite materials obtained. The experimental results show that the use of polyurethane (PUR) foams and jute fabric reinforcing biocomposites promotes interesting properties of thermal and acoustic insulation. A multi-layer structure composed by PUR foam on the intermediate layer revealed thermal resistances until 0.272 m2 K W-1. On the other hand, the use of jute fabric reinforcing biocomposites on exterior layer promoted a noise reduction at 500 Hz until 8.3 dB. These results allow to conclude that the use of PUR foams and jute fabric reinforcing biocomposites can be used successfully in rehabilitation of buildings, when the thermal and acoustic insulation is looked for.

Numerical Simulation of the Motion of Aerosol Particles in Open Cell Foam Materials

NASA Astrophysics Data System (ADS)

Solovev, S. A.; Soloveva, O. V.; Popkova, O. S.

2018-03-01

The motion of aerosol particles in open cell foam material is studied. The porous medium is investigated for a three-dimensional case with detailed simulation of cellular structures within an ordered geometry. Numerical calculations of the motion of particles and their deposition due to inertial and gravitational mechanisms are performed. Deposition efficiency curves for a broad range of particle sizes are constructed. The effect deposition mechanisms have on the efficiency of the porous material as a filter is analyzed.

Bonding of reusable surface insulation with low density silicone foams

NASA Technical Reports Server (NTRS)

Hiltz, A. A.; Hockridge, R. R.; Curtis, F. P.

1972-01-01

The development and evaluation of a reduced density, high reliable foamed bond strain isolation system for attaching reusable surface insulation to the space shuttle structure are reported. Included are data on virgin materials as well as on materials that received 100 cycles of exposure to 650 F for approximately 20 minutes per cycle. Room temperature vulcanizing silicon elastomers meet all the requirments for an adhesive bonding system.

Fabrication of Aluminum Tubes Filled with Aluminum Alloy Foam by Friction Welding.

PubMed

Hangai, Yoshihiko; Nakano, Yukiko; Koyama, Shinji; Kuwazuru, Osamu; Kitahara, Soichiro; Yoshikawa, Nobuhiro

2015-10-23

Aluminum foam is usually used as the core of composite materials by combining it with dense materials, such as in Al foam core sandwich panels and Al-foam-filled tubes, owing to its low tensile and bending strengths. In this study, all-Al foam-filled tubes consisting of ADC12 Al-Si-Cu die-cast aluminum alloy foam and a dense A1050 commercially pure Al tube with metal bonding were fabricated by friction welding. First, it was found that the ADC12 precursor was firmly bonded throughout the inner wall of the A1050 tube without a gap between the precursor and the tube by friction welding. No deformation of the tube or foaming of the precursor was observed during the friction welding. Next, it was shown that by heat treatment of an ADC12-precursor-bonded A1050 tube, gases generated by the decomposition of the blowing agent expand the softened ADC12 to produce the ADC12 foam interior of the dense A1050 tube. A holding time during the foaming process of approximately t H = 8.5 min with a holding temperature of 948 K was found to be suitable for obtaining a sound ADC12-foam-filled A1050 tube with sufficient foaming, almost uniform pore structures over the entire specimen, and no deformation or reduction in the thickness of the tube.

Fabrication of Aluminum Tubes Filled with Aluminum Alloy Foam by Friction Welding

PubMed Central

Hangai, Yoshihiko; Nakano, Yukiko; Koyama, Shinji; Kuwazuru, Osamu; Kitahara, Soichiro; Yoshikawa, Nobuhiro

2015-01-01

Aluminum foam is usually used as the core of composite materials by combining it with dense materials, such as in Al foam core sandwich panels and Al-foam-filled tubes, owing to its low tensile and bending strengths. In this study, all-Al foam-filled tubes consisting of ADC12 Al-Si-Cu die-cast aluminum alloy foam and a dense A1050 commercially pure Al tube with metal bonding were fabricated by friction welding. First, it was found that the ADC12 precursor was firmly bonded throughout the inner wall of the A1050 tube without a gap between the precursor and the tube by friction welding. No deformation of the tube or foaming of the precursor was observed during the friction welding. Next, it was shown that by heat treatment of an ADC12-precursor-bonded A1050 tube, gases generated by the decomposition of the blowing agent expand the softened ADC12 to produce the ADC12 foam interior of the dense A1050 tube. A holding time during the foaming process of approximately tH = 8.5 min with a holding temperature of 948 K was found to be suitable for obtaining a sound ADC12-foam-filled A1050 tube with sufficient foaming, almost uniform pore structures over the entire specimen, and no deformation and minimum reduction in the thickness of the tube. PMID:28793629

Advanced Heat Exchangers for Dry Cooling Systems, Phase II

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fortini, Arthur J.; Horwath, Joseph

Dry cooling systems are an option for industrial and utility power plants that cannot obtain permits for cooling water or where cooling water is unavailable. Currently available dry cooling systems are more expensive and less efficient than wet cooling systems, so significant improvements in efficiency are needed to make them economically viable. Previous attempts at using foams as cooling fin materials for power generating systems have focused on high thermal conductivity graphite foams made via the Oak Ridge process. Because these materials have high flow restrictions and hence low permeability with respect to air flow, their internal volume and surfacemore » area were not effectively used. Consequently, they performed poorly and offered no advantage over aluminum fins. A foam with a more open structure would provide increased permeability, enable greater airflow through the bulk material, increase the rate of heat transfer, and enable the material to outperform traditional fin structures. In this project, Ultramet designed, fabricated, and tested low flow restriction, high-efficiency foam-based heat exchangers. Calculations based on existing thermal and hydraulic data for Ultramet’s high-performance open-cell foams indicated that 65-ppi (pores per linear inch) pyrolytic graphite foam with a relative density of 15 vol%, produced by chemical vapor infiltration (CVI), would have an effectiveness significantly greater than that of a state-of-the-art Hamon/Balcke-Durr aluminum fin system and greater than that of the POCO graphite foams previously tested for the DOE National Energy Technology Laboratory. Using the same chevron design, test setup, and run conditions as were used with the Hamon/Balcke-Durr fin system and the POCO foams, Ultramet tested graphite foams with air flow velocities of 0.07–3.2 m/sec and pressure drops of 0.03–9.7 inH2O. The best-performing graphite foam architectures had air velocities in excess of 2.5 m/sec when the pressure drop was 1 inH2O. Because a foam-based system is more efficient than a fin-based system, a smaller heat exchanger installation can be used, significantly reducing the installation cost. Furthermore, because the foam-based system is physically smaller with no increase in flow restriction, less electrical power is needed to run the fans to drive the air through the condenser. The result is a decrease in both the installation and operating costs, which in turn will decrease the overall life cycle cost of the system.« less

Liquid foam templating - A route to tailor-made polymer foams.

PubMed

Andrieux, Sébastien; Quell, Aggeliki; Stubenrauch, Cosima; Drenckhan, Wiebke

2018-06-01

Solid foams with pore sizes between a few micrometres and a few millimetres are heavily exploited in a wide range of established and emerging applications. While the optimisation of foam applications requires a fine control over their structural properties (pore size distribution, pore opening, foam density, …), the great complexity of most foaming processes still defies a sound scientific understanding and therefore explicit control and prediction of these parameters. We therefore need to improve our understanding of existing processes and also develop new fabrication routes which we understand and which we can exploit to tailor-make new porous materials. One of these new routes is liquid templating in general and liquid foam templating in particular, to which this review article is dedicated. While all solid foams are generated from an initially liquid(-like) state, the particular notion of liquid foam templating implies the specific condition that the liquid foam has time to find its "equilibrium structure" before it is solidified. In other words, the characteristic time scales of the liquid foam's stability and its solidification are well separated, allowing to build on the vast know-how on liquid foams established over the last 20 years. The dispersed phase of the liquid foam determines the final pore size and pore size distribution, while the continuous phase contains the precursors of the desired porous scaffold. We review here the three key challenges which need to be addressed by this approach: (1) the control of the structure of the liquid template, (2) the matching of the time scales between the stability of the liquid template and solidification, and (3) the preservation of the structure of the template throughout the process. Focusing on the field of polymer foams, this review gives an overview of recent research on the properties of liquid foam templates and summarises a key set of studies in the emerging field of liquid foam templating. It finishes with an outlook on future developments. Occasional references to non-polymeric foams are given if the analogy provides specific insight into a physical phenomenon. Copyright © 2018 Elsevier B.V. All rights reserved.

Polyurethane rigid foam, a proven thermal insulating material for applications between +130°C and -196°C

NASA Astrophysics Data System (ADS)

Demharter, Anton

Polyurethanes are high molecular weight polymers based on the polyaddition of polyfunctional hydroxyl-group containing compounds and polyisocyanates. A wide variety of properties can be tailored to fulfil the requirements of different applications: soft to hard, plastic, elastic or thermoset, compact or foamed. Compared with other insulating materials, PUR rigid foam is highly competitive. There are five product-related advantages: lowest thermal conductivity, high mechanical and chemical properties at both high and low temperatures, all major international fire safety requirements can be satisfied, the ability to form sandwich structures with various facer materials, and the new generation of PUR is CFC-free and recyclable. Rigid polyurethane foams perform well in most areas of low-temperature insulations. Products in density ranging from approximately 30 to 200 kg m -3 withstand temperatures down to -196°C. Typical applications are: refrigerated vehicles, road and rail tankers, vessels for refrigerated cargo, pipelines, liquid gas tanks for LPG and LNG and cryogenic wind tunnels. The paper presents applications, corresponding properties of the rigid foams used, and also other insulating materials in competition to PUR are discussed.

Structural Continuum Modeling of Space Shuttle External Tank Foam Insulation

NASA Technical Reports Server (NTRS)

Steeve, Brian; Ayala, Sam; Purlee, T. Eric; Shaw, Phillip

2006-01-01

The Space Shuttle External Tank is covered with rigid polymeric closed-cell foam insulation to prevent ice formation, protect the metallic tank from aerodynamic heating, and control the breakup of the tank during re-entry. The cryogenic state of the tank, as well as the ascent into a vacuum environment, places this foam under significant stress. Because the loss of the foam during ascent poses a critical risk to the shuttle orbiter, there is much interest in understanding the stress state in the foam insulation and how it may contribute to fracture and debris loss. Several foam applications on the external tank have been analyzed using finite element methods. This presentation describes the approach used to model the foam material behavior and compares analytical results to experiments.

Green waste cooking oil-based rigid polyurethane foam

NASA Astrophysics Data System (ADS)

Enderus, N. F.; Tahir, S. M.

2017-11-01

Polyurethane is a versatile polymer traditionally prepared using petroleum-based raw material. Petroleum, however, is a non-renewable material and polyurethane produced was found to be non-biodegradable. In quest for a more environmentally friendly alternative, wastecooking oil, a highly abundant domestic waste with easily derivatized structure, is a viable candidate to replace petroleum. In this study,an investigation to determine physical and chemical properties of rigid polyurethane (PU) foam from waste cooking oil (WCO) was carried out. WCO was first adsorbed by using coconut husk activated carbon adsorbent prior to be used for polyol synthesis. The purified WCO was then used to synthesize polyol via transesterification reaction to yield alcohol groups in the WCO chains structure. Finally, the WCO-based polyol was used to prepare rigid PU foam. The optimum formulation for PU formation was found to be 90 polyol: 60 glycerol: 54 water: 40 diethanolamine: 23 diisocyanate. The rigid PU foam has density of 208.4 kg/m3 with maximum compressive strength and capability to receive load at 0.03 MPa and 0.09 kN, respectively. WCO-based PU can potentially be used to replace petroleum-based PU as house construction materials such as insulation panels.

Acoustic and vibrational damping in porous solids.

PubMed

Göransson, Peter

2006-01-15

A porous solid may be characterized as an elastic-viscoelastic and acoustic-viscoacoustic medium. For a flexible, open cell porous foam, the transport of energy is carried both through the sound pressure waves propagating through the fluid in the pores, and through the elastic stress waves carried through the solid frame of the material. For a given situation, the balance between energy dissipated through vibration of the solid frame, changes in the acoustic pressure and the coupling between the waves varies with the topological arrangement, choice of material properties, interfacial conditions, etc. Engineering of foams, i.e. designs built on systematic and continuous relationships between polymer chemistry, processing, micro-structure, is still a vision for the future. However, using state-of-the-art simulation techniques, multiple layer arrangements of foams may be tuned to provide acoustic and vibrational damping at a low-weight penalty. In this paper, Biot's modelling of porous foams is briefly reviewed from an acoustics and vibrations perspective with a focus on the energy dissipation mechanisms. Engineered foams will be discussed in terms of results from simulations performed using finite element solutions. A layered vehicle-type structure is used as an example.

Orbital foamed material extruder

NASA Technical Reports Server (NTRS)

Tucker, Dennis S. (Inventor)

2009-01-01

This invention is a process for producing foamed material in space comprising the steps of: rotating the material to simulate the force of gravity; heating the rotating material until it is molten; extruding the rotating, molten material; injecting gas into the extruded, rotating, molten material to produce molten foamed material; allowing the molten foamed material to cool to below melting temperature to produce the foamed material. The surface of the extruded foam may be heated to above melting temperature and allowed to cool to below melting temperature. The extruded foam may also be cut to predetermined length. The starting material may be metal or glass. Heating may be accomplished by electrical heating elements or by solar heating.

Hypervelocity Impact Performance of Open Cell Foam Core Sandwich Panel Structures

NASA Technical Reports Server (NTRS)

Ryan, Shannon; Christiansen, Eric; Lear, Dana

2009-01-01

Metallic foams are a relatively new class of materials with low density and novel physical, mechanical, thermal, electrical and acoustic properties. Although incompletely characterized, they offer comparable mechanical performance to traditional spacecraft structural materials (i.e. honeycomb sandwich panels) without detrimental through-thickness channeling cells. There are two competing types of metallic foams: open cell and closed cell. Open cell foams are considered the more promising technology due to their lower weight and higher degree of homogeneity. Leading micrometeoroid and orbital debris shields (MMOD) incorporate thin plates separated by a void space (i.e. Whipple shield). Inclusion of intermediate fabric layers, or multiple bumper plates have led to significant performance enhancements, yet these shields require additional non-ballistic mass for installation (fasteners, supports, etc.) that can consume up to 35% of the total shield weight [1]. Structural panels, such as open cell foam core sandwich panels, that are also capable of providing sufficient MMOD protection, represent a significant potential for increased efficiency in hypervelocity impact shielding from a systems perspective through a reduction in required non-ballistic mass. In this paper, the results of an extensive impact test program on aluminum foam core sandwich panels are reported. The effect of pore density, and core thickness on shielding performance have been evaluated over impact velocities ranging from 2.2 - 9.3 km/s at various angles. A number of additional tests on alternate sandwich panel configurations of comparable-weight have also been performed, including aluminum honeycomb sandwich panels (see Figure 1), Nomex honeycomb core sandwich panels, and 3D aluminum honeycomb sandwich panels. A total of 70 hypervelocity impact tests are reported, from which an empirical ballistic limit equation (BLE) has been derived. The BLE is in the standard form suitable for implementation in risk analysis software, and includes the effect of panel thickness, core density, and facesheet material properties. A comparison between the shielding performance of foam core sandwich panel structures and common MMOD shielding configurations is made for both conservative (additional 35% non-ballistic mass) and optimistic (additional mass equal to 30% of bumper mass) considerations. Suggestions to improve the shielding performance of foam core sandwich panels are made, including the use of outer mesh layers, intermediate fabric/composite layers, and varying pore density.

Simulated Tip Rub Testing of Low-Density Metal Foam

NASA Technical Reports Server (NTRS)

Bowman, Cheryl L.; Jones, Michael G.

2009-01-01

Preliminary acoustic studies have indicated that low-density, open-cell, metal foams may be suitable acoustic liner material for noise suppression in high by-pass engines. Metal foam response under simulated tip rub conditions was studied to assess whether its durability would be sufficient for the foam to serve both as a rub strip above the rotor as well as an acoustic treatment. Samples represented four metal alloys, nominal cell dimensions ranging from 60 to 120 cells per inch (cpi), and relative densities ranging from 3.4 to 10 percent. The resulting rubbed surfaces were relatively smooth and the open cell structure of the foam was not adversely affected. Sample relative density appeared to have significant influence on the forces induced by the rub event. Acoustic responses of various surface preparations were measured using a normal incidence tube. The results of this study indicate that the foam s open-cell structure was retained after rubbing and that the acoustic absorption spectra variation was minimal.

Temperature control transport system

DOEpatents

Schabron, John F; Sorini-Wong, Susan S

2014-12-09

Embodiments of the inventive technology may involve the use of layered, insulated PCM assemblage that itself comprises: modular insulating foam material 8 that, upon establishment as part of the assemblage, defines inner foam material sides 9 and outer foam material sides 10; thin reflective material 11 established against (whether directly in contact with or not) at least either the inner foam material sides or the outer foam materials sides, and modular, enclosed PCM sections 12 established between the modular insulating foam material and the interior center.

Foam patterns

DOEpatents

Chaudhry, Anil R; Dzugan, Robert; Harrington, Richard M; Neece, Faurice D; Singh, Nipendra P; Westendorf, Travis

2013-11-26

A method of creating a foam pattern comprises mixing a polyol component and an isocyanate component to form a liquid mixture. The method further comprises placing a temporary core having a shape corresponding to a desired internal feature in a cavity of a mold and inserting the mixture into the cavity of the mold so that the mixture surrounds a portion of the temporary core. The method optionally further comprises using supporting pins made of foam to support the core in the mold cavity, with such pins becoming integral part of the pattern material simplifying subsequent processing. The method further comprises waiting for a predetermined time sufficient for a reaction from the mixture to form a foam pattern structure corresponding to the cavity of the mold, wherein the foam pattern structure encloses a portion of the temporary core and removing the temporary core from the pattern independent of chemical leaching.

Exploratory development of foams from liquid crystal polymers

NASA Technical Reports Server (NTRS)

Chung, T. S.

1985-01-01

Two types of liquid crystal polymer (LCP) compositions were studied and evaluated as structural foam materials. One is a copolymer of 6-hydroxy-2-naphthoic acid, terephthalic acid, and p-acetoxyacetanilide (designed HNA/TA/AAA), and the other is a copolymer of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid (designated HBA/HNA). Experimental results showed that the extruded HNA/TA/AA foams have better mechanical quality and appearance than HBA/HNA foams. Heat treatment improved foam tensile strength and break elongation, but reduced their modulus. The injection molding results indicated that nitrogen foaming agents with a low-pressure process gave better void distribution in the injection molded LCP foams than those made by the conventional injection-molding machine and chemical blowing agents. However, in comparing LCP foams with other conventional plastic foams, HBA/HNA foams have better mechanical properties than foamed ABS and PS, but are comparable to PBT and inferior to polycarbonate foams, especially in heat-deflection temperature and impact resistance energy. These deficiencies are due to LCP molecules not having been fully oriented during the Union-Carbide low-pressure foaming process.

Development of fire-resistant, low smoke generating, thermally stable end items for aircraft and spacecraft

NASA Technical Reports Server (NTRS)

Gagliani, J.; Sorathia, U. A. K.; Wilcoxson, A. L.

1977-01-01

Materials were developed to improve aircraft interior materials by modifying existing polymer structures, refining the process parameters, and by the use of mechanical configurations designed to overcome specific deficiencies. The optimization, selection, and fabrication of five fire resistant, low smoke emitting open cell foams are described for five different types of aircraft cabin structures. These include: resilient foams, laminate floor and wall paneling, thermal/acoustical insulation, molded shapes, and coated fabrics. All five have been produced from essentially the same polyimide precursor and have resulted in significant benefits from transfer of technology between the various tasks.

Polyimide Foams Offer Superior Insulation

NASA Technical Reports Server (NTRS)

2012-01-01

At Langley Research Center, Erik Weiser and his colleagues in the Advanced Materials and Processing Branch were working with a new substance for fabricating composites for use in supersonic aircraft. The team, however, was experiencing some frustration. Every time they tried to create a solid composite from the polyimide (an advanced polymer) material, it bubbled and foamed. It seemed like the team had reached a dead end in their research - until they had another idea. "We said, This isn t going to work for composites, but maybe we could make a foam out of it," Weiser says. "That was kind of our eureka moment, to see if we could go in a whole other direction. And it worked." Weiser and his colleagues invented a new kind of polyimide foam insulation they named TEEK. The innovation displayed a host of advantages over existing insulation options. Compared to other commercial foams, Weiser explains, polyimide foams perform well across a broad range of temperatures, noting that the NASA TEEK foams provide effective structural insulation up to 600 F and down to cryogenic temperatures. The foam does not burn or off-gas toxic fumes, and even at -423 F - the temperature of liquid hydrogen - the material stays flexible. The inventors could produce the TEEK foam at a range of densities, from 0.5 pounds per cubic foot up to 20 pounds per cubic foot, making the foam ideal for a range of applications, including as insulation for reusable launch vehicles and for cryogenic tanks and lines. They also developed a unique, friable balloon format for manufacturing the foam, producing it as hollow microspheres that allowed the foam to be molded and then cured into any desired shape - perfect for insulating pipes of different sizes and configurations. The team s originally unplanned invention won an "R&D 100" award, and a later form of the foam, called LaRC FPF-44 (Spinoff 2009), was named "NASA Invention of the Year" in 2007.

46 CFR 179.240 - Foam flotation material.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 7 2010-10-01 2010-10-01 false Foam flotation material. 179.240 Section 179.240... Requirements § 179.240 Foam flotation material. (a) Foam may only be installed as flotation material on a vessel when approved by the cognizant OCMI. (b) If foam is installed as flotation material on a vessel...

46 CFR 179.240 - Foam flotation material.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 7 2011-10-01 2011-10-01 false Foam flotation material. 179.240 Section 179.240... Requirements § 179.240 Foam flotation material. (a) Foam may only be installed as flotation material on a vessel when approved by the cognizant OCMI. (b) If foam is installed as flotation material on a vessel...

Flexible and Lightweight Pressure Sensor Based on Carbon Nanotube/Thermoplastic Polyurethane-Aligned Conductive Foam with Superior Compressibility and Stability.

PubMed

Huang, Wenju; Dai, Kun; Zhai, Yue; Liu, Hu; Zhan, Pengfei; Gao, Jiachen; Zheng, Guoqiang; Liu, Chuntai; Shen, Changyu

2017-12-06

Flexible and lightweight carbon nanotube (CNT)/thermoplastic polyurethane (TPU) conductive foam with a novel aligned porous structure was fabricated. The density of the aligned porous material was as low as 0.123 g·cm -3 . Homogeneous dispersion of CNTs was achieved through the skeleton of the foam, and an ultralow percolation threshold of 0.0023 vol % was obtained. Compared with the disordered foam, mechanical properties of the aligned foam were enhanced and the piezoresistive stability of the flexible foam was improved significantly. The compression strength of the aligned TPU foam increases by 30.7% at the strain of 50%, and the stress of the aligned foam is 22 times that of the disordered foam at the strain of 90%. Importantly, the resistance variation of the aligned foam shows a fascinating linear characteristic under the applied strain until 77%, which would benefit the application of the foam as a desired pressure sensor. During multiple cyclic compression-release measurements, the aligned conductive CNT/TPU foam represents excellent reversibility and reproducibility in terms of resistance. This nice capability benefits from the aligned porous structure composed of ladderlike cells along the orientation direction. Simultaneously, the human motion detections, such as walk, jump, squat, etc. were demonstrated by using our flexible pressure sensor. Because of the lightweight, flexibility, high compressibility, excellent reversibility, and reproducibility of the conductive aligned foam, the present study is capable of providing new insights into the fabrication of a high-performance pressure sensor.

Tensile Properties and Fracture Behavior of Aluminum Alloy Foam Fabricated from Die Castings without Using Blowing Agent by Friction Stir Processing Route

PubMed Central

Hangai, Yoshihiko; Kamada, Hiroto; Utsunomiya, Takao; Kitahara, Soichiro; Kuwazuru, Osamu; Yoshikawa, Nobuhiro

2014-01-01

Al foam has been used in a wide range of applications owing to its light weight, high energy absorption and high sound insulation. One of the promising processes for fabricating Al foam involves the use of a foamable precursor. In this study, ADC12 Al foams with porosities of 67%–78% were fabricated from Al alloy die castings without using a blowing agent by the friction stir processing route. The pore structure and tensile properties of the ADC12 foams were investigated and compared with those of commercially available ALPORAS. From X-ray computed tomography (X-ray CT) observations of the pore structure of ADC12 foams, it was found that they have smaller pores with a narrower distribution than those in ALPORAS. Tensile tests on the ADC12 foams indicated that as their porosity increased, the tensile strength and tensile strain decreased, with strong relation between the porosity, tensile strength, and tensile strain. ADC12 foams exhibited brittle fracture, whereas ALPORAS exhibited ductile fracture, which is due to the nature of the Al alloy used as the base material of the foams. By image-based finite element (FE) analysis using X-ray CT images corresponding to the tensile tests on ADC12 foams, it was shown that the fracture path of ADC12 foams observed in tensile tests and the regions of high stress obtained from FE analysis correspond to each other. Therefore, it is considered that the fracture behavior of ADC12 foams in relation to their pore structure distribution can be investigated by image-based FE analysis. PMID:28788573

Tensile Properties and Fracture Behavior of Aluminum Alloy Foam Fabricated from Die Castings without Using Blowing Agent by Friction Stir Processing Route.

PubMed

Hangai, Yoshihiko; Kamada, Hiroto; Utsunomiya, Takao; Kitahara, Soichiro; Kuwazuru, Osamu; Yoshikawa, Nobuhiro

2014-03-21

Al foam has been used in a wide range of applications owing to its light weight, high energy absorption and high sound insulation. One of the promising processes for fabricating Al foam involves the use of a foamable precursor. In this study, ADC12 Al foams with porosities of 67%-78% were fabricated from Al alloy die castings without using a blowing agent by the friction stir processing route. The pore structure and tensile properties of the ADC12 foams were investigated and compared with those of commercially available ALPORAS. From X-ray computed tomography (X-ray CT) observations of the pore structure of ADC12 foams, it was found that they have smaller pores with a narrower distribution than those in ALPORAS. Tensile tests on the ADC12 foams indicated that as their porosity increased, the tensile strength and tensile strain decreased, with strong relation between the porosity, tensile strength, and tensile strain. ADC12 foams exhibited brittle fracture, whereas ALPORAS exhibited ductile fracture, which is due to the nature of the Al alloy used as the base material of the foams. By image-based finite element (FE) analysis using X-ray CT images corresponding to the tensile tests on ADC12 foams, it was shown that the fracture path of ADC12 foams observed in tensile tests and the regions of high stress obtained from FE analysis correspond to each other. Therefore, it is considered that the fracture behavior of ADC12 foams in relation to their pore structure distribution can be investigated by image-based FE analysis.

Three-dimensional N-doped graphene/polyaniline composite foam for high performance supercapacitors

NASA Astrophysics Data System (ADS)

Zhu, Jun; Kong, Lirong; Shen, Xiaoping; Chen, Quanrun; Ji, Zhenyuan; Wang, Jiheng; Xu, Keqiang; Zhu, Guoxing

2018-01-01

Three-dimensional (3D) graphene aerogel and its composite with interconnected pores have aroused continuous interests in energy storage field owning to its large surface area and hierarchical pore structure. Herein, we reported the preparation of 3D nitrogen-doped graphene/polyaniline (N-GE/PANI) composite foam for supercapacitive material with greatly improved electrochemical performance. The 3D porous structure can allow the penetration and diffusion of electrolyte, the incorporation of nitrogen doping can enhance the wettability of the active material and the number of active sites with electrolyte, and both the N-GE and PANI can ensure the high electrical conductivity of total electrode. Moreover, the synergistic effect between N-GE and PANI materials also play an important role on the electrochemical performance of electrode. Therefore, the as-prepared composite foam could deliver a high specific capacitance of 528 F g-1 at 0.1 A g-1 and a high cyclic stability with 95.9% capacitance retention after 5000 charge-discharge cycles. This study provides a new idea on improving the energy storage capacity of supercapacitors by using 3D graphene-based psedocapacitive electrode materials.

Investigation of Shock Wave Attenuation in Porous Materials

DTIC Science & Technology

2009-12-01

Foam ...... 38 Table 4. Summary of Material Characteristics of Polyurethane Foams ............ 40 Table 5. Summary of Experiment Results...polyurethane foam , he performed a simple symmetric impact simulation to investigate the material properties and wave propagation characteristics of the...describes the characteristics of the two foam materials studied in this research, namely the aluminum metal foam and rigid polyurethane foam , which

Nanosized LiFePO4-decorated emulsion-templated carbon foam for 3D micro batteries: a study of structure and electrochemical performance

NASA Astrophysics Data System (ADS)

Asfaw, Habtom D.; Roberts, Matthew R.; Tai, Cheuk-Wai; Younesi, Reza; Valvo, Mario; Nyholm, Leif; Edström, Kristina

2014-07-01

In this article, we report a novel 3D composite cathode fabricated from LiFePO4 nanoparticles deposited conformally on emulsion-templated carbon foam by a sol-gel method. The carbon foam is synthesized via a facile and scalable method which involves the carbonization of a high internal phase emulsion (polyHIPE) polymer template. Various techniques (XRD, SEM, TEM and electrochemical methods) are used to fully characterize the porous electrode and confirm the distribution and morphology of the cathode active material. The major benefits of the carbon foam used in our work are closely connected with its high surface area and the plenty of space suitable for sequential coating with battery components. After coating with a cathode material (LiFePO4 nanoparticles), the 3D electrode presents a hierarchically structured electrode in which a porous layer of the cathode material is deposited on the rigid and bicontinuous carbon foam. The composite electrodes exhibit impressive cyclability and rate performance at different current densities affirming their importance as viable power sources in miniature devices. Footprint area capacities of 1.72 mA h cm-2 at 0.1 mA cm-2 (lowest rate) and 1.1 mA h cm-2 at 6 mA cm-2 (highest rate) are obtained when the cells are cycled in the range 2.8 to 4.0 V vs. lithium.In this article, we report a novel 3D composite cathode fabricated from LiFePO4 nanoparticles deposited conformally on emulsion-templated carbon foam by a sol-gel method. The carbon foam is synthesized via a facile and scalable method which involves the carbonization of a high internal phase emulsion (polyHIPE) polymer template. Various techniques (XRD, SEM, TEM and electrochemical methods) are used to fully characterize the porous electrode and confirm the distribution and morphology of the cathode active material. The major benefits of the carbon foam used in our work are closely connected with its high surface area and the plenty of space suitable for sequential coating with battery components. After coating with a cathode material (LiFePO4 nanoparticles), the 3D electrode presents a hierarchically structured electrode in which a porous layer of the cathode material is deposited on the rigid and bicontinuous carbon foam. The composite electrodes exhibit impressive cyclability and rate performance at different current densities affirming their importance as viable power sources in miniature devices. Footprint area capacities of 1.72 mA h cm-2 at 0.1 mA cm-2 (lowest rate) and 1.1 mA h cm-2 at 6 mA cm-2 (highest rate) are obtained when the cells are cycled in the range 2.8 to 4.0 V vs. lithium. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr01682c

Blending Novatein¯ thermoplastic protein with PLA for carbon dioxide assisted batch foaming

NASA Astrophysics Data System (ADS)

Walallavita, Anuradha; Verbeek, Casparus J. R.; Lay, Mark

2016-03-01

The convenience of polymeric foams has led to their widespread utilisation in everyday life. However, disposal of synthetic petroleum-derived foams has had a detrimental effect on the environment which needs to be addressed. This study uses a clean and sustainable approach to investigate the foaming capability of a blend of two biodegradable polymers, polylactic acid (PLA) and Novatein® Thermoplastic Protein (NTP). PLA, derived from corn starch, can successfully be foamed using a batch technique developed by the Biopolymer Network Ltd. NTP is a patented formulation of bloodmeal and chemical additives which can be extruded and injection moulded similar to other thermoplastics. However, foaming NTP is a new area of study and its interaction with blowing agents in the batch process is entirely unknown. Subcritical and supercritical carbon dioxide have been examined individually in two uniquely designed pressure vessels to foam various compositions of NTP-PLA blends. Foamed material were characterised in terms of expansion ratio, cell size, and cellular morphology in order to study how the composition of NTP-PLA affects foaming with carbon dioxide. It was found that blends with 5 wt. % NTP foamed using subcritical CO2 expanded up to 11 times due to heterogeneous nucleation. Morphology analysis using scanning electron microscopy showed that foams blown with supercritical CO2 had a finer cell structure with consistent cell size, whereas, foams blown with subcritical CO2 ranged in cell size and showed cell wall rupture. Ultimately, this research would contribute to the production of a biodegradable foam material to be used in packaging applications, thereby adding to the application potential of NTP.

Industrially benign super-compressible piezoresistive carbon foams with predefined wetting properties: from environmental to electrical applications

NASA Astrophysics Data System (ADS)

Pham, Tung Ngoc; Samikannu, Ajaikumar; Kukkola, Jarmo; Rautio, Anne-Riikka; Pitkänen, Olli; Dombovari, Aron; Lorite, Gabriela Simone; Sipola, Teemu; Toth, Geza; Mohl, Melinda; Mikkola, Jyri-Pekka; Kordas, Krisztian

2014-11-01

In the present work electrically conductive, flexible, lightweight carbon sponge materials derived from open-pore structure melamine foams are studied and explored. Hydrophobic and hydrophilic surface properties - depending on the chosen treatment conditions - allow the separation and storage of liquid chemical compounds. Activation of the carbonaceous structures substantially increases the specific surface area from ~4 m2g-1 to ~345 m2g-1, while retaining the original three-dimensional, open-pore structure suitable for hosting, for example, Ni catalyst nanoparticles. In turn the structure is rendered suitable for hydrogenating acetone to 2-propanol and methyl isobutyl ketone as well for growing hierarchical carbon nanotube structures used as electric double-layer capacitor electrodes with specific capacitance of ~40 F/g. Mechanical stress-strain analysis indicates the materials are super-compressible (>70% volume reduction) and viscoelastic with excellent damping behavior (loss of 0.69 +/- 0.07), while piezoresistive measurements show very high gauge factors (from ~20 to 50) over a large range of deformations. The cost-effective, robust and scalable synthesis - in conjunction with their fascinating multifunctional utility - makes the demonstrated carbon foams remarkable competitors with other three-dimensional carbon materials typically based on pyrolyzed biopolymers or on covalently bonded graphene and carbon nanotube frameworks.

Industrially benign super-compressible piezoresistive carbon foams with predefined wetting properties: from environmental to electrical applications.

PubMed

Pham, Tung Ngoc; Samikannu, Ajaikumar; Kukkola, Jarmo; Rautio, Anne-Riikka; Pitkänen, Olli; Dombovari, Aron; Lorite, Gabriela Simone; Sipola, Teemu; Toth, Geza; Mohl, Melinda; Mikkola, Jyri-Pekka; Kordas, Krisztian

2014-11-06

In the present work electrically conductive, flexible, lightweight carbon sponge materials derived from open-pore structure melamine foams are studied and explored. Hydrophobic and hydrophilic surface properties - depending on the chosen treatment conditions - allow the separation and storage of liquid chemical compounds. Activation of the carbonaceous structures substantially increases the specific surface area from ~4 m(2)g(-1) to ~345 m(2)g(-1), while retaining the original three-dimensional, open-pore structure suitable for hosting, for example, Ni catalyst nanoparticles. In turn the structure is rendered suitable for hydrogenating acetone to 2-propanol and methyl isobutyl ketone as well for growing hierarchical carbon nanotube structures used as electric double-layer capacitor electrodes with specific capacitance of ~40 F/g. Mechanical stress-strain analysis indicates the materials are super-compressible (>70% volume reduction) and viscoelastic with excellent damping behavior (loss of 0.69 ± 0.07), while piezoresistive measurements show very high gauge factors (from ~20 to 50) over a large range of deformations. The cost-effective, robust and scalable synthesis - in conjunction with their fascinating multifunctional utility - makes the demonstrated carbon foams remarkable competitors with other three-dimensional carbon materials typically based on pyrolyzed biopolymers or on covalently bonded graphene and carbon nanotube frameworks.

Preparation and characterization of cellulose-based foams via microwave curing

PubMed Central

Demitri, Christian; Giuri, Antonella; Raucci, Maria Grazia; Giugliano, Daniela; Madaghiele, Marta; Sannino, Alessandro; Ambrosio, Luigi

2014-01-01

In this work, a mixture of a sodium salt of carboxymethylcellulose (CMCNa) and polyethylene glycol diacrylate (PEGDA700) was used for the preparation of a microporous structure by using the combination of two different procedures. First, physical foaming was induced using Pluronic as a blowing agent, followed by a chemical stabilization. This second step was carried out by means of an azobis(2-methylpropionamidine)dihydrochloride as the thermoinitiator (TI). This reaction was activated by heating the sample homogeneously using a microwave generator. Finally, the influence of different CMCNa and PEGDA700 ratios on the final properties of the foams was investigated. The viscosity, water absorption capacity, elastic modulus and porous structure were evaluated for each sample. In addition, preliminary biological characterization was carried out with the aim to prove the biocompatibility of the resulting material. The foam, including 20% of PEGDA700 in the mixture, demonstrated higher viscosity and stability before thermo-polymerization. In addition, increased water absorption capacity, mechanical resistance and a more uniform microporous structure were obtained for this sample. In particular, foam with 3% of CMCNa shows a hierarchical structure with open pores of different sizes. This morphology increased the properties of the foams. The full set of samples demonstrated an excellent biocompatibility profile with a good cell proliferation rate of more than 7 days. PMID:24501679

Architected cellular ceramics with tailored stiffness via direct foam writing

NASA Astrophysics Data System (ADS)

Muth, Joseph T.; Dixon, Patrick G.; Woish, Logan; Gibson, Lorna J.; Lewis, Jennifer A.

2017-02-01

Hierarchical cellular structures are ubiquitous in nature because of their low-density, high-specific properties, and multifunctionality. Inspired by these systems, we created lightweight ceramic architectures composed of closed-cell porous struts patterned in the form of hexagonal and triangular honeycombs by direct foam writing. The foam ink contains bubbles stabilized by attractive colloidal particles suspended in an aqueous solution. The printed and sintered ceramic foam honeycombs possess low relative density (˜6%). By tailoring their microstructure and geometry, we created honeycombs with different modes of deformation, exceptional specific stiffness, and stiffness values that span over an order of magnitude. This capability represents an important step toward the scalable fabrication of hierarchical porous materials for applications, including lightweight structures, thermal insulation, tissue scaffolds, catalyst supports, and electrodes.

Architected cellular ceramics with tailored stiffness via direct foam writing

PubMed Central

Muth, Joseph T.; Dixon, Patrick G.; Woish, Logan; Gibson, Lorna J.; Lewis, Jennifer A.

2017-01-01

Hierarchical cellular structures are ubiquitous in nature because of their low-density, high-specific properties, and multifunctionality. Inspired by these systems, we created lightweight ceramic architectures composed of closed-cell porous struts patterned in the form of hexagonal and triangular honeycombs by direct foam writing. The foam ink contains bubbles stabilized by attractive colloidal particles suspended in an aqueous solution. The printed and sintered ceramic foam honeycombs possess low relative density (∼6%). By tailoring their microstructure and geometry, we created honeycombs with different modes of deformation, exceptional specific stiffness, and stiffness values that span over an order of magnitude. This capability represents an important step toward the scalable fabrication of hierarchical porous materials for applications, including lightweight structures, thermal insulation, tissue scaffolds, catalyst supports, and electrodes. PMID:28179570

Shrinkage deformation of cement foam concrete

NASA Astrophysics Data System (ADS)

Kudyakov, A. I.; Steshenko, A. B.

2015-01-01

The article presents the results of research of dispersion-reinforced cement foam concrete with chrysotile asbestos fibers. The goal was to study the patterns of influence of chrysotile asbestos fibers on drying shrinkage deformation of cement foam concrete of natural hardening. The chrysotile asbestos fiber contains cylindrical fiber shaped particles with a diameter of 0.55 micron to 8 microns, which are composed of nanostructures of the same form with diameters up to 55 nm and length up to 22 microns. Taking into account the wall thickness, effective reinforcement can be achieved only by microtube foam materials, the so- called carbon nanotubes, the dimensions of which are of power less that the wall pore diameter. The presence of not reinforced foam concrete pores with perforated walls causes a decrease in its strength, decreases the mechanical properties of the investigated material and increases its shrinkage. The microstructure investigation results have shown that introduction of chrysotile asbestos fibers in an amount of 2 % by weight of cement provides the finely porous foam concrete structure with more uniform size closed pores, which are uniformly distributed over the volume. This reduces the shrinkage deformation of foam concrete by 50%.

Characterization of Solid Polymers, Ceramic Gap Filler, and Closed-Cell Polymer Foam Using Low-Load Test Methods

NASA Technical Reports Server (NTRS)

Herring, Helen M.

2008-01-01

Various solid polymers, polymer-based composites, and closed-cell polymer foam are being characterized to determine their mechanical properties, using low-load test methods. The residual mechanical properties of these materials after environmental exposure or extreme usage conditions determines their value in aerospace structural applications. In this experimental study, four separate polymers were evaluated to measure their individual mechanical responses after thermal aging and moisture exposure by dynamic mechanical analysis. A ceramic gap filler, used in the gaps between the tiles on the Space Shuttle, was also tested, using dynamic mechanical analysis to determine material property limits during flight. Closed-cell polymer foam, used for the Space Shuttle External Tank insulation, was tested under low load levels to evaluate how the foam's mechanical properties are affected by various loading and unloading scenarios.

Investigation of Mild Steel Thin-Wall Tubes in Unfilled and Foam-Filled Triangle, Square, and Hexagonal Cross Sections Under Compression Load

NASA Astrophysics Data System (ADS)

Rajak, Dipen Kumar; Kumaraswamidhas, L. A.; Das, S.

2018-02-01

This study has examined proposed structures with mild steel-reinforced LM30 aluminum (Al) alloy having diversely unfilled and 10 wt.% SiCp composite foam-filled tubes for improving axial compression performance. This class of material has novel physical, mechanical, and electrical properties along with low density. In the present experiment, Al alloy foams were prepared by the melt route technique using metal hydride powder as a foaming agent. Crash energy phenomena for diverse unfilled and foam-filled in mild steel thin-wall tubes (triangular, square and hexagonal) were studied as well. Compression deformation investigation was conducted at strain rates of 0.001-0.1/s for evaluating specific energy absorption (SEA) under axial loading conditions. The results were examined to measure plateau stress, maximum densification strain, and deformation mechanism of the materials. Specific energy absorption and total energy absorption capacities of the unfilled and filled sections were determined from the compressive stress-strain curves, which were then compared with each other.

Micromechanics of Spray-On Foam Insulation

NASA Technical Reports Server (NTRS)

Bednarcyk, Brett A.; Aboudi, Jacob; Arnold, Steven M.; Sullivan, Roy M.

2007-01-01

Understanding the thermo-mechanical response of the Space Shuttle External Tank spray-on foam insulation (SOFI) material is critical, to NASA's Return to Flight effort. This closed-cell rigid polymeric foam is used to insulate the metallic Space Shuttle External Tank, which is at cryogenic temperatures immediately prior to and during lift off. The shedding of the SOFI during ascent led to the loss of the Columbia, and eliminating/minimizing foam lass from the tank has become a priority for NASA as it seeks to resume scheduled space shuttle missions. Determining the nature of the SOFI material behavior in response to both thermal and mechanical loading plays an important role as any structural modeling of the shedding phenomenon k predicated on knowledge of the constitutive behavior of the foam. In this paper, the SOFI material has been analyzed using the High-Fidelity Generalized Method of Cells (HFGMC) micromechanics model, which has recently been extended to admit a triply-periodic 3-D repeating unit cell (RUC). Additional theoretical extensions that mere made in order to enable modeling of the closed-cell-foam material include the ability to represent internal boundaries within the RUC (to simulated internal pores) and the ability to impose an internal pressure within the simulated pores. This latter extension is crucial as two sources contribute to significant internal pressure changes within the SOFI pores. First, gas trapped in the pores during the spray process will expand or contract due to temperature changes. Second, the pore pressure will increase due to outgassing of water and other species present in the foam skeleton polymer material. With HFGMC's new pore pressure modeling capabilities, a nonlinear pressure change within the simulated pore can be imposed that accounts for both of these sources, in addition to stmdar&-thermal and mechanical loading; The triply-periodic HFGMC micromechanics model described above was implemented within NASA GRC's MAC/GMC software package, giving the model access to a range of nonlinear constitutive models for the polymeric foam skeleton material. A repeating unit cell architecture was constructed that, while relatively simple, still accounts for the geometric anisotropy of the porous foam microstructure and its thin walls and thicker edges. With the lack of reliable polymeric foam skeleton materia1 properties, many simulations were executed aimed at backing out these material properties. Then, using these properties, predictions of the thermo-mechanical behavior of the foam, including calculated internal applied pressure profiles, were performed and compared with appropriate experimental data.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gilbertson, Robert D.; Patterson, Brian M.; Smith, Zachary

An accelerated aging study of BKC 44306-10 rigid polyurethane foam was carried out. Foam samples were aged in a nitrogen atmosphere at three different temperatures: 50 °C, 65 °C, and 80 °C. Foam samples were periodically removed from the aging canisters at 1, 3, 6, 9, 12, and 15 month intervals when FT-IR spectroscopy, dimensional analysis, and mechanical testing experiments were performed. Micro Computed Tomography imaging was also employed to study the morphology of the foams. Over the course of the aging study the foams the decreased in size by a magnitude of 0.001 inches per inch of foam. Micromore » CT showed the heterogeneous nature of the foam structure likely resulting from flow effects during the molding process. The effect of aging on the compression and tensile strength of the foam was minor and no cause for concern. FT-IR spectroscopy was used to follow the foam chemistry. However, it was difficult to draw definitive conclusions about the changes in chemical nature of the materials due to large variability throughout the samples.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Herman, Matthew J.; Peterson, Dominic; Henderson, Kevin

Understanding deuterium-tritium mix in capsules is critical to achieving fusion within inertial confined fusion experiments. One method of understanding how the mix of hydrogen fuels can be controlled is by creating various structured deuterated foams and filling the capsule with liquid tritium. Historically, these materials have been a stochastically structured gas-blown foam. Later, to improve the uniformity of this material, pore formers have been used which are then chemically removed, leaving behind a foam of monodisperse voids. However, this technique is still imperfect in that fragments of the pore templating particles may not be completely removed and the void distributionmore » may not be uniform over the size scale of the capsule. Recently, advances in three-dimensional printing suggest that it can be used to create microlattices and capsule walls in one single print. Demonstrated in this paper are proof-of-concept microlattices produced using two-photon polymerization with submicrometer resolution of various structures as well as a microlattice-containing capsule. Finally, with this technology, complete control of the mixing structure is possible, amenable to modeling and easily modified for tailored target design.« less

Metal Foam Analysis: Improving Sandwich Structure Technology for Engine Fan and Propeller Blades

NASA Technical Reports Server (NTRS)

Fedor, Jessica L.

2004-01-01

The Life Prediction Branch of the NASA Glenn Research Center is searching for ways to construct aircraft and rotorcraft engine fan and propeller blades that are lighter and less costly. One possible design is to create a sandwich structure composed of two metal faces sheets and a metal foam core. The face sheets would carry the bending loads and the foam core would have to resist the transverse shear loads. Metal foam is ideal because of its low density and energy absorption capabilities, making the structure lighter, yet still stiff. The material chosen for the face sheets and core was 17-4PH stainless steel, which is easy to make and has appealing mechanical properties. This material can be made inexpensively compared to titanium and polymer matrix composites, the two current fan blade alternatives. Initial tests were performed on design models, including vibration and stress analysis. These tests revealed that the design is competitive with existing designs; however, some problems were apparent that must be addressed before it can be implemented in new technology. The foam did not hold up as well as expected under stress. This could be due to a number of issues, but was most likely a result of a large number of pores within the steel that weakened the structure. The brazing between the face sheets and the foam was also identified as a concern. The braze did not hold up well under shear stress causing the foam to break away from the face sheets. My role in this project was to analyze different options for improving the design. I primarily spent my time examining various foam samples, created with different sintering conditions, to see which exhibited the most favorable characteristics for our purpose. Methods of analysis that I employed included examining strut integrity under a microscope, counting the number of cells per inch, measuring the density, testing the microhardness, and testing the strength under compression. Shear testing will also be done to examine the strengths of different types of brazes.

Nanosized LiFePO4-decorated emulsion-templated carbon foam for 3D micro batteries: a study of structure and electrochemical performance.

PubMed

Asfaw, Habtom D; Roberts, Matthew R; Tai, Cheuk-Wai; Younesi, Reza; Valvo, Mario; Nyholm, Leif; Edström, Kristina

2014-08-07

In this article, we report a novel 3D composite cathode fabricated from LiFePO4 nanoparticles deposited conformally on emulsion-templated carbon foam by a sol-gel method. The carbon foam is synthesized via a facile and scalable method which involves the carbonization of a high internal phase emulsion (polyHIPE) polymer template. Various techniques (XRD, SEM, TEM and electrochemical methods) are used to fully characterize the porous electrode and confirm the distribution and morphology of the cathode active material. The major benefits of the carbon foam used in our work are closely connected with its high surface area and the plenty of space suitable for sequential coating with battery components. After coating with a cathode material (LiFePO4 nanoparticles), the 3D electrode presents a hierarchically structured electrode in which a porous layer of the cathode material is deposited on the rigid and bicontinuous carbon foam. The composite electrodes exhibit impressive cyclability and rate performance at different current densities affirming their importance as viable power sources in miniature devices. Footprint area capacities of 1.72 mA h cm(-2) at 0.1 mA cm(-2) (lowest rate) and 1.1 mA h cm(-2) at 6 mA cm(-2) (highest rate) are obtained when the cells are cycled in the range 2.8 to 4.0 V vs. lithium.

Pu Anion Exchange Process Intensification

DOE Office of Scientific and Technical Information (OSTI.GOV)

Taylor-Pashow, Kathryn M. L.

This research is focused on improving the efficiency of the anion exchange process for purifying plutonium. While initially focused on plutonium, the technology could also be applied to other ion-exchange processes. Work in FY17 focused on the improvement and optimization of porous foam columns that were initially developed in FY16. These foam columns were surface functionalized with poly(4-vinylpyridine) (PVP) to provide the Pu specific anion-exchange sites. Two different polymerization methods were explored for maximizing the surface functionalization with the PVP. The open-celled polymeric foams have large open pores and large surface areas available for sorption. The fluid passes through themore » large open pores of this material, allowing convection to be the dominant mechanism by which mass transport takes place. These materials generally have very low densities, open-celled structures with high cell interconnectivity, small cell sizes, uniform cell size distributions, and high structural integrity. These porous foam columns provide advantages over the typical porous resin beads by eliminating the slow diffusion through resin beads, making the anion-exchange sites easily accessible on the foam surfaces. The best performing samples exceeded the Pu capacity of the commercially available resin, and also offered the advantage of sharper elution profiles, resulting in a more concentrated product, with less loss of material to the dilute heads and tails cuts. An alternate approach to improving the efficiency of this process was also explored through the development of a microchannel array system for performing the anion exchange.« less

Improving sound absorption property of polyurethane foams doped with natural fiber

NASA Astrophysics Data System (ADS)

Azahari, M. Shafiq M.; Rus, Anika Zafiah M.; Taufiq Zaliran, M.; Kormin, Shaharuddin

2017-08-01

This study investigates the acoustics behavior of wood fibre filler of Red Meranti - filled polyurethane foam as a sound absorbing material. Three different thicknesses have been selected which is 10 mm, 20 mm and 30 mm. By choosing percentage loading of Red Meranti (RM) wood fibre of 5%, 10%, 15% and 20% added with polymer foam is namely as polymer foam (PF) composites of PF5%, PF10%, PF15% and PF20%. The sound absorption coefficient (α) and pore structure of the foam samples have been examined by using Impedance Tube test and Scanning Electron Microscopy (SEM). The results revealed that the highest thickness of highest filler loading (PF20%) gives higher sound absorption coefficient (α). The absorption frequency level is observed at 0.9922 and 0.99889 which contributed from low and high frequency absorption level respectively. The smallest pores size structure was observed with highest filler loading of PF. The higher the thickness and the higher the percentage loading of wood filler gives smaller pore structure, consequently, increased the sound absorption coefficient level.

Development, testing, and numerical modeling of a foam sandwich biocomposite

NASA Astrophysics Data System (ADS)

Chachra, Ricky

This study develops a novel sandwich composite material using plant based materials for potential use in nonstructural building applications. The face sheets comprise woven hemp fabric and a sap based epoxy, while the core comprises castor oil based foam with waste rice hulls as reinforcement. Mechanical properties of the individual materials are tested in uniaxial compression and tension for the foam and hemp, respectively. The sandwich composite is tested in 3 point bending. Flexural results are compared to a finite element model developed in the commercial software Abaqus, and the validated model is then used to investigate alternate sandwich geometries. Sandwich model responses are compared to existing standards for nonstructural building panels, showing that the novel material is roughly half the strength of equally thick drywall. When space limitations are not an issue, a double thickness sandwich biocomposite is found to be a structurally acceptable replacement for standard gypsum drywall.

Hypervelocity impact testing of advanced materials and structures for micrometeoroid and orbital debris shielding

NASA Astrophysics Data System (ADS)

Ryan, Shannon; Christiansen, Eric L.

2013-02-01

A series of 66 hypervelocity impact experiments have been performed to assess the potential of various materials (aluminium, titanium, copper, stainless steel, nickel, nickel/chromium, reticulated vitreous carbon, silver, ceramic, aramid, ceramic glass, and carbon fibre) and structures (monolithic plates, open-cell foam, flexible fabrics, rigid meshes) for micrometeoroid and orbital debris (MMOD) shielding. Arranged in various single-, double-, and triple-bumper configurations, screening tests were performed with 0.3175 cm diameter Al2017-T4 spherical projectiles at nominally 6.8 km/s and normal incidence. The top performing shields were identified through target damage assessments and their respective weight. The top performing candidate shield at the screening test condition was found to be a double-bumper configuration with a 0.25 mm thick Al3003 outer bumper, 6.35 mm thick 40 PPI aluminium foam inner bumper, and 1.016 mm thick Al2024-T3 rear wall (equal spacing between bumpers and rear wall). In general, double-bumper candidates with aluminium plate outer bumpers and foam inner bumpers were consistently found to be amongst the top performers. For this impact condition, potential weight savings of at least 47% over conventional all-aluminium Whipple shields are possible by utilizing the investigated materials and structures. The results of this study identify materials and structures of interest for further, more in-depth, impact investigations.

On the balancing of structural and acoustic performance of a sandwich panel based on topology, property, and size optimization

NASA Astrophysics Data System (ADS)

Cameron, Christopher J.; Lind Nordgren, Eleonora; Wennhage, Per; Göransson, Peter

2014-06-01

Balancing structural and acoustic performance of a multi-layered sandwich panel is a formidable undertaking. Frequently the gains achieved in terms of reduced weight, still meeting the structural design requirements, are lost by the changes necessary to regain acceptable acoustic performance. To alleviate this, a design method for a multifunctional load bearing vehicle body panel is proposed which attempts to achieve a balance between structural and acoustic performance. The approach is based on numerical modelling of the structural and acoustic behaviour in a combined topology, size, and property optimization in order to achieve a three dimensional optimal distribution of structural and acoustic foam materials within the bounding surfaces of a sandwich panel. In particular the effects of the coupling between one of the bounding surface face sheets and acoustic foam are examined for its impact on both the structural and acoustic overall performance of the panel. The results suggest a potential in introducing an air gap between the acoustic foam parts and one of the face sheets, provided that the structural design constraints are met without prejudicing the layout of the different foam types.

Applicability of cranial models in urethane resin and foam as a substitute for bone: are synthetic materials reliable?

PubMed

Muccino, Enrico; Porta, Davide; Magli, Francesca; Cigada, Alfredo; Sala, Remo; Gibelli, Daniele; Cattaneo, Cristina

2013-09-01

As literature is poor in functional synthetic cranial models, in this study, synthetic handmade models of cranial vaults were produced in two different materials (a urethane resin and a self-hardening foam), from multiple bone specimens (eight original cranial vaults: four human and four swine), in order to test their resemblance to bone structure in behavior, during fracture formation. All the vaults were mechanically tested with a 2-kg impact weight and filmed with a high-speed camera. Fracture patterns were homogeneous in all swine vaults and heterogeneous in human vaults, with resin fractures more similar to bone fractures. Mean fracture latency time extrapolated by videos were of 0.75 msec (bone), 1.5 msec (resin), 5.12 msec (foam) for human vaults and of 0.625 msec (bone), 1.87 msec (resin), 3.75 msec (foam) for swine vaults. These data showed that resin models are more similar to bone than foam reproductions, but that synthetic material may behave quite differently from bone as concerns fracture latency times. © 2013 American Academy of Forensic Sciences.

Blending Novatein{sup ®} thermoplastic protein with PLA for carbon dioxide assisted batch foaming

DOE Office of Scientific and Technical Information (OSTI.GOV)

Walallavita, Anuradha, E-mail: asw15@students.waikato.ac.nz; Verbeek, Casparus J. R., E-mail: jverbeek@waikato.ac.nz; Lay, Mark, E-mail: mclay@waikato.ac.nz

2016-03-09

The convenience of polymeric foams has led to their widespread utilisation in everyday life. However, disposal of synthetic petroleum-derived foams has had a detrimental effect on the environment which needs to be addressed. This study uses a clean and sustainable approach to investigate the foaming capability of a blend of two biodegradable polymers, polylactic acid (PLA) and Novatein® Thermoplastic Protein (NTP). PLA, derived from corn starch, can successfully be foamed using a batch technique developed by the Biopolymer Network Ltd. NTP is a patented formulation of bloodmeal and chemical additives which can be extruded and injection moulded similar to othermore » thermoplastics. However, foaming NTP is a new area of study and its interaction with blowing agents in the batch process is entirely unknown. Subcritical and supercritical carbon dioxide have been examined individually in two uniquely designed pressure vessels to foam various compositions of NTP-PLA blends. Foamed material were characterised in terms of expansion ratio, cell size, and cellular morphology in order to study how the composition of NTP-PLA affects foaming with carbon dioxide. It was found that blends with 5 wt. % NTP foamed using subcritical CO{sub 2} expanded up to 11 times due to heterogeneous nucleation. Morphology analysis using scanning electron microscopy showed that foams blown with supercritical CO{sub 2} had a finer cell structure with consistent cell size, whereas, foams blown with subcritical CO{sub 2} ranged in cell size and showed cell wall rupture. Ultimately, this research would contribute to the production of a biodegradable foam material to be used in packaging applications, thereby adding to the application potential of NTP.« less

Impact Resistance of Lightweight Hybrid Structures for Gas Turbine Engine Fan Containment Applications

NASA Technical Reports Server (NTRS)

Hebsur, Mohan G.; Noebe, Ronald D.; Revilock, Duane M.

2003-01-01

The ballistic impact resistance of hybrid composite sandwich structures was evaluated with the ultimate goal of developing new materials or structures for potential gas turbine engine fan containment applications. The sandwich structures investigated consisted of GLARE-5 laminates as face sheets with lightweight cellular metallic materials such as honeycomb, foam, and lattice block as a core material. The impact resistance of these hybrid sandwich structures was compared to GLARE-5 laminates and 2024-T3 Al sheet, which were tested as a function of areal weight (material thickness). The GLARE-5 laminates exhibited comparable impact properties to that of 2024-T3 Al at low areal weights, even though there were significant differences in the static tensile properties of these materials. The GLARE-5, however, did have a greater ballistic limit than straight aluminum sheet at higher areal weights. Furthermore, there is up to a 25% advantage in ballistic limit for the GLARE-5/foam sandwich structures compared to straight 2024-T3 Al. But no advantage in ballistic limit was observed between any of the hybrid sandwich structures and thicker versions of GLARE-5. Recommendations for future work are provided, based on these preliminary data.

Structure and mechanical properties of naturally occurring lightweight foam-filled cylinder--the peacock's tail coverts shaft and its components.

PubMed

Liu, Z Q; Jiao, D; Meyers, M A; Zhang, Z F

2015-04-01

Feather shaft, which is primarily featured by a cylinder filled with foam, possesses a unique combination of mechanical robustness and flexibility with a low density through natural evolution and selection. Here the hierarchical structures of peacock's tail coverts shaft and its components are systematically characterized from millimeter to nanometer length scales. The variations in constituent and geometry along the length are examined. The mechanical properties under both dry and wet conditions are investigated. The deformation and failure behaviors and involved strengthening, stiffening and toughening mechanisms are analyzed qualitatively and quantitatively and correlated to the structures. It is revealed that the properties of feather shaft and its components have been optimized through various structural adaptations. Synergetic strengthening and stiffening effects can be achieved in overall rachis owing to increased failure resistance. This study is expected to aid in deeper understandings on the ingenious structure-property design strategies developed by nature, and accordingly, provide useful inspiration for the development of high-performance synthetic foams and foam-filled materials. Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Foam Optics and Mechanics

NASA Technical Reports Server (NTRS)

Durian, Douglas J.; Zimmerli, Gregory A.

2002-01-01

The Foam Optics and Mechanics (FOAM) project will exploit the microgravity environment to more accurately measure the rheological and optical characteristics of wet aqueous foams. Using both rheology and laser light scattering diagnostics, the goal is to quantify the unusual elastic character of foams in terms of their underlying microscopic structure and dynamics. Of particular interest is determining how the elastic character vanishes, i.e., how the foam 'melts' into a simple viscous liquid, as a function of both increasing liquid content and increasing shear strain rate. The unusual elastic character of foams will be quantified macroscopically by measurement of the shear stress as a function of shear strain rate and of time following a step strain. Such data will be analyzed in terms of a yield stress, shear moduli, and dynamical time scales. Microscopic information about bubble packing and rearrangement dynamics, from which the macroscopic non-Newtonian properties ultimately arise, will be obtained non-invasively by multiple-light scattering: diffuse transmission spectroscopy (DTS) and diffusing wave spectroscopy (DWS). Quantitative trends with materials parameters, most importantly average bubble size and liquid content, will be sought in order to elucidate the fundamental connection between the microscopic structure and dynamics and the macroscopic rheology.

Applications of Polymer Matrix Syntactic Foams

NASA Astrophysics Data System (ADS)

Gupta, Nikhil; Zeltmann, Steven E.; Shunmugasamy, Vasanth Chakravarthy; Pinisetty, Dinesh

2013-11-01

A collection of applications of polymer matrix syntactic foams is presented in this article. Syntactic foams are lightweight porous composites that found their early applications in marine structures due to their naturally buoyant behavior and low moisture absorption. Their light weight has been beneficial in weight sensitive aerospace structures. Syntactic foams have pushed the performance boundaries for composites and have enabled the development of vehicles for traveling to the deepest parts of the ocean and to other planets. The high volume fraction of porosity in syntactic foams also enabled their applications in thermal insulation of pipelines in oil and gas industry. The possibility of tailoring the mechanical and thermal properties of syntactic foams through a combination of material selection, hollow particle volume fraction, and hollow particle wall thickness has helped in rapidly growing these applications. The low coefficient of thermal expansion and dimensional stability at high temperatures are now leading their use in electronic packaging, composite tooling, and thermoforming plug assists. Methods have been developed to tailor the mechanical and thermal properties of syntactic foams independent of each other over a wide range, which is a significant advantage over other traditional particulate and fibrous composites.

DEVELOPMENT OF CONTINUOUS SOLVENT EXTRACTION PROCESSES FOR COAL DERIVED CARBON PRODUCTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Elliot B. Kennel; Stephen P. Carpenter; Dady Dadyburjor

2006-03-27

The purpose of this DOE-funded effort is to develop continuous processes for solvent extraction of coal for the production of carbon products. These carbon products include materials used in metals smelting, especially in the aluminum and steel industries, as well as porous carbon structural material referred to as ''carbon foam'' and carbon fibers. During this reporting period, efforts have focused on the development of continuous processes for hydrogenation as well as continuous production of carbon foam and coke.

Laser Irradiated Foam Targets: Absorption and Radiative Properties

NASA Astrophysics Data System (ADS)

Salvadori, Martina; Luigi Andreoli, Pier; Cipriani, Mattia; Consoli, Fabrizio; Cristofari, Giuseppe; De Angelis, Riccardo; di Giorgio, Giorgio; Giulietti, Danilo; Ingenito, Francesco; Gus'kov, Sergey Yu.; Rupasov, Alexander A.

2018-01-01

An experimental campaign to characterize the laser radiation absorption of foam targets and the subsequent emission of radiation from the produced plasma was carried out in the ABC facility of the ENEA Research Center in Frascati (Rome). Different targets have been used: plastic in solid or foam state and aluminum targets. The activated different diagnostics allowed to evaluate the plasma temperature, the density distribution, the fast particle spectrum and the yield of the X-Ray radiation emitted by the plasma for the different targets. These results confirm the foam homogenization action on laser-plasma interaction, mainly attributable to the volume absorption of the laser radiation propagating in such structured materials. These results were compared with simulation absorption models of the laser propagating into a foam target.

An Analysis of Nondestructive Evaluation Techniques for Polymer Matrix Composite Sandwich Materials

NASA Technical Reports Server (NTRS)

Cosgriff, Laura M.; Roberts, Gary D.; Binienda, Wieslaw K.; Zheng, Diahua; Averbeck, Timothy; Roth, Donald J.; Jeanneau, Philippe

2006-01-01

Structural sandwich materials composed of triaxially braided polymer matrix composite material face sheets sandwiching a foam core are being utilized for applications including aerospace components and recreational equipment. Since full scale components are being made from these sandwich materials, it is necessary to develop proper inspection practices for their manufacture and in-field use. Specifically, nondestructive evaluation (NDE) techniques need to be investigated for analysis of components made from these materials. Hockey blades made from sandwich materials and a flat sandwich sample were examined with multiple NDE techniques including thermographic, radiographic, and shearographic methods to investigate damage induced in the blades and flat panel components. Hockey blades used during actual play and a flat polymer matrix composite sandwich sample with damage inserted into the foam core were investigated with each technique. NDE images from the samples were presented and discussed. Structural elements within each blade were observed with radiographic imaging. Damaged regions and some structural elements of the hockey blades were identified with thermographic imaging. Structural elements, damaged regions, and other material variations were detected in the hockey blades with shearography. Each technique s advantages and disadvantages were considered in making recommendations for inspection of components made from these types of materials.

Thermal Expansion of Polyurethane Foam

NASA Technical Reports Server (NTRS)

Lerch, Bradley A.; Sullivan, Roy M.

2006-01-01

Closed cell foams are often used for thermal insulation. In the case of the Space Shuttle, the External Tank uses several thermal protection systems to maintain the temperature of the cryogenic fuels. A few of these systems are polyurethane, closed cell foams. In an attempt to better understand the foam behavior on the tank, we are in the process of developing and improving thermal-mechanical models for the foams. These models will start at the microstructural level and progress to the overall structural behavior of the foams on the tank. One of the key properties for model characterization and verification is thermal expansion. Since the foam is not a material, but a structure, the modeling of the expansion is complex. It is also exacerbated by the anisoptropy of the material. During the spraying and foaming process, the cells become elongated in the rise direction and this imparts different properties in the rise direction than in the transverse directions. Our approach is to treat the foam as a two part structure consisting of the polymeric cell structure and the gas inside the cells. The polymeric skeleton has a thermal expansion of its own which is derived from the basic polymer chemistry. However, a major contributor to the thermal expansion is the volume change associated with the gas inside of the closed cells. As this gas expands it exerts pressure on the cell walls and changes the shape and size of the cells. The amount that this occurs depends on the elastic and viscoplastic properties of the polymer skeleton. The more compliant the polymeric skeleton, the more influence the gas pressure has on the expansion. An additional influence on the expansion process is that the polymeric skeleton begins to breakdown at elevated temperatures and releases additional gas species into the cell interiors, adding to the gas pressure. The fact that this is such a complex process makes thermal expansion ideal for testing the models. This report focuses on the thermal expansion tests and the response of the microstructure. A novel optical method is described which is appropriate for measuring thermal expansion at high temperatures without influencing the thermal expansion measurement. Detailed microstructural investigations will also be described which show cell expansion as a function of temperature. Finally, a phenomenological model on thermal expansion will be described.

Elasticity Modulus and Flexural Strength Assessment of Foam Concrete Layer of Poroflow

NASA Astrophysics Data System (ADS)

Hajek, Matej; Decky, Martin; Drusa, Marian; Orininová, Lucia; Scherfel, Walter

2016-10-01

Nowadays, it is necessary to develop new building materials, which are in accordance to the principles of the following provisions of the Roads Act: The design of road is a subject that follows national technical standards, technical regulations and objectively established results of research and development for road infrastructure. Foam concrete, as a type of lightweight concrete, offers advantages such as low bulk density, thermal insulation and disadvantages that will be reduced by future development. The contribution focuses on identifying the major material characteristics of foam concrete named Poroflow 17-5, in order to replace cement-bound granular mixtures. The experimental measurements performed on test specimens were the subject of diploma thesis in 2015 and continuously of the dissertation thesis and grant research project. At the beginning of the contribution, an overview of the current use of foam concrete abroad is elaborated. Moreover, it aims to determine the flexural strength of test specimens Poroflow 17-5 in combination with various basis weights of the underlying geotextile. Another part of the article is devoted to back-calculation of indicative design modulus of Poroflow based layers based on the results of static plate load tests provided at in situ experimental stand of Faculty of Civil Engineering, University of Žilina (FCE Uniza). Testing stand has been created in order to solve problems related to research of road and railway structures. Concern to building construction presents a physical homomorphic model that is identical with the corresponding theory in all structural features. Based on the achieved material characteristics, the tensile strength in bending of previously used road construction materials was compared with innovative alternative of foam concrete and the suitability for the base layers of pavement roads was determined.

Microstructure and calorimetric behavior of laser welded open cell foams in CuZnAl shape memory alloy

NASA Astrophysics Data System (ADS)

Biffi, Carlo Alberto; Previtali, Barbara; Tuissi, Ausonio

Cellular shape memory alloys (SMAs) are very promising smart materials able to combine functional properties of the material with lightness, stiffness, and damping capacity of the cellular structure. Their processing with low modification of the material properties remains an open question. In this work, the laser weldability of CuZnAl SMA in the form of open cell foams was studied. The cellular structure was proved to be successfully welded in lap joint configuration by using a thin plate of the same alloy. Softening was seen in the welded bead in all the investigated ranges of process speed as well as a double stage heat affected zone was identified due to different microstructures; the martensitic transformation was shifted to higher temperatures and the corresponding peaks were sharper with respect to the base material due to the rapid solidification of the material. Anyways, no compositional variations were detected in the joints.

Development of fine-celled bio-fiber composite foams using physical blowing agents and nano-particles

NASA Astrophysics Data System (ADS)

Guo, Gangjian

As one of eco-friendly bio-fibers, wood-fiber has been incorporated in plastics to make wood-fiber/plastic composites (WPC) with an increased stiffness, durability and lowered cost. However, these improvements are usually accompanied by loss in the ductility and impact strength of the composites. These shortcomings can be significantly improved by incorporating a fine-cell foam structure in the composites. This thesis presents the development of the foaming technology for the manufacture of fine-cell WPC foams with environmentally benign physical blowing agents (PBAs), and focuses on the elucidation of the fundamental foaming mechanisms and the related issues involved. One critical issue comes from the volatiles evolved from the wood-fiber during high temperature processing. The volatiles, as a blowing agent, can contribute to the foaming process. However, they lead to gross deterioration of the cell structure of WPC foams. The presence of volatiles makes foaming of WPC "a poorly understood black art". With the use of PBAs, a strategy of lowering processing temperature becomes feasible, to suppress the generation of volatiles. A series of PBA-based experiments were designed using a statistical design of experiments (DOE) technique, and were performed to establish the relationship of processing and material variables with the structure of WPC foams. Fundamental foaming behaviors for two different PBAs and two different polymer systems were identified. WPC foams with a fine-cell morphology and a desired density were successfully obtained at the optimized conditions. Another limitation for the wider application of WPC is their flammability. Innovative use of a small amount of nano-clay in WPC significantly improved the flame-retarding property of WPC, and the key issue was to achieve a high degree of exfoliation of nano-particles in the polymer matrix, to achieve a desired flammability reduction. The synergistic effects of nano-particles in foaming of WPC were identified as well.

Plastic Materials for Insulating Applications.

ERIC Educational Resources Information Center

Wang, S. F.; Grossman, S. J.

1987-01-01

Discusses the production and use of polymer materials as thermal insulators. Lists several materials that provide varying degrees of insulation. Describes the production of polymer foam and focuses on the major applications of polystyrene foam, polyurethane foam, and polyisocyanurate foam. (TW)

46 CFR 170.245 - Foam flotation material.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 7 2011-10-01 2011-10-01 false Foam flotation material. 170.245 Section 170.245... REQUIREMENTS FOR ALL INSPECTED VESSELS Special Installations § 170.245 Foam flotation material. (a) Installation of foam must be approved by the OCMI. (b) If foam is used to comply with § 171.070(d), § 171.095(c...

46 CFR 170.245 - Foam flotation material.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 7 2010-10-01 2010-10-01 false Foam flotation material. 170.245 Section 170.245... REQUIREMENTS FOR ALL INSPECTED VESSELS Special Installations § 170.245 Foam flotation material. (a) Installation of foam must be approved by the OCMI. (b) If foam is used to comply with § 171.070(d), § 171.095(c...

Dynamic Finite Element Predictions for Mars Sample Return Cellular Impact Test #4

NASA Technical Reports Server (NTRS)

Fasanella, Edwin L.; Billings, Marcus D.

2001-01-01

The nonlinear, transient dynamic finite element code, MSC.Dytran, was used to simulate an impact test of an energy absorbing Earth Entry Vehicle (EEV) that will impact without a parachute. EEVOs are designed to return materials from asteroids, comets, or planets for laboratory analysis on Earth. The EEV concept uses an energy absorbing cellular structure designed to contain and limit the acceleration of space exploration samples during Earth impact. The spherical shaped cellular structure is composed of solid hexagonal and pentagonal foam-filled cells with hybrid graphite-epoxy/Kevlar cell walls. Space samples fit inside a smaller sphere at the center of the EEVOs cellular structure. Pre-test analytical predictions were compared with the test results from a bungee accelerator. The model used to represent the foam and the proper failure criteria for the cell walls were critical in predicting the impact loads of the cellular structure. It was determined that a FOAM1 model for the foam and a 20% failure strain criteria for the cell walls gave an accurate prediction of the acceleration pulse for cellular impact.

Fly-ash geo-polymer foamed concrete

NASA Astrophysics Data System (ADS)

Kargin, Aleksey; Baev, Vladimir; Mashkin, Nikolay

2017-01-01

In recent years, the interest of researchrs in using fly-ash as a raw material for the geo-polymer synthesis is increasing. Kuzbass region (in Russia) has a large amount of ash wastes generated, which defined the relevace of the study performed in this paper. Results of investigating load-bearing capacity of structural insulating material produced by geo-polymerization of fly-ash of Kemerovo hydro-electric power plant with the addition of complex activator are described in the paper. Hydrogen peroxide solution was used as the foaming agent. The activation time, the temperature of isothermal holding and hardening in normal conditions for all samples were constant. The compressive strength and the mean density of geo-polymer foamed concrete were determined. The influence of the material composition on its properties was revealed. It is found that of the geo-polymer foamed concrete with the optimum composition has hardness of 1,1-3,5 MPa at the density of 400 to 900 kg/m3. Thus, the production of the fly-ash geo-polymer concretes and mortars is feasible, justified and promising.

Flexible and Hierarchical Metal-Organic Framework Composites for High-Performance Catalysis.

PubMed

Huang, Ning; Drake, Hannah; Li, Jialuo; Pang, Jiangdong; Wang, Ying; Yuan, Shuai; Wang, Qi; Cai, Peiyu; Qin, Junsheng; Zhou, Hong-Cai

2018-05-18

The development of new types of porous composite materials is of great significance owing to their potentially improved performance over those of individual components and extensive applications in separation, energy storage, and heterogeneous catalysis. In this work, we integrated mesoporous metal-organic frameworks (MOFs) with macroporous melamine foam (MF) using a one-pot process, generating a series of MOF/MF composite materials with preserved crystallinity, hierarchical porosity, and increased stability over that of melamine foam. The MOF nanocrystals were threaded by the melamine foam networks, resembling a ball-and-stick model overall. As a proof-of-concept study, the resulting MOF/MF composite materials were employed as an effective heterogeneous catalyst for the epoxidation of cholesteryl esters. Combining the advantages of interpenetrative mesoporous and macroporous structures, the MOF/melamine foam composite provided higher dispersibility and more accessibility of catalytic sites, exhibiting excellent catalytic performance. This strategy constitutes an important step forward the development of other MOF composites and exploration of their high-performance catalysis. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Propagation of sound in highly porous open-cell elastic foams

NASA Technical Reports Server (NTRS)

Lambert, R. F.

1983-01-01

This work presents both theoretical predictions and experimental measurements of attenuation and progressive phase constants of sound in open-cell, highly porous, elastic polyurethane foams. The foams are available commercially in graded pore sizes for which information about the static flow resistance, thermal time constant, volume porosity, dynamic structure factor, and speed of sound is known. The analysis is specialized to highly porous foams which can be efficient sound absorbers at audio frequencies. Negligible effect of internal wave coupling on attenuation and phase shift for the frequency range 16-6000 Hz was predicted and no experimentally significant effects were observed in the bulk samples studied. The agreement between predictions and measurements in bulk materials is excellent. The analysis is applicable to both the regular and compressed elastic open-cell foams.

Free Open Access Medical Education (FOAM) Resources in a Team-Based Learning Educational Series.

PubMed

Fallon, Timothy; Strout, Tania D

2018-01-01

Although Free Open Access Medical Education (FOAM) has become popular within emergency medicine, concerns exist regarding its role in resident education. We sought to develop an educational intervention whereby residents could review FOAM resources while maintaining faculty oversight. We created a novel curriculum pairing FOAM from the Academic Life in Emergence Medicine (ALiEM) Approved Instructional Resources (Air) series with a team-based learning (TBL) format. Residents have an opportunity to engage with FOAM in a structured setting with faculty input on possible practice changes. This series has been well-received by residents and appears to have increased engagement with core content material. Qualitative feedback from residents on this series has been positive and we believe this is the first described use of TBL in emergency medicine.

Integrated Structural/Acoustic Modeling of Heterogeneous Panels

NASA Technical Reports Server (NTRS)

Bednarcyk, Brett, A.; Aboudi, Jacob; Arnold, Steven, M.; Pennline, James, A.

2012-01-01

A model for the dynamic response of heterogeneous media is presented. A given medium is discretized into a number of subvolumes, each of which may contain an elastic anisotropic material, void, or fluid, and time-dependent boundary conditions are applied to simulate impact or incident pressure waves. The full time-dependent displacement and stress response throughout the medium is then determined via an explicit solution procedure. The model is applied to simulate the coupled structural/acoustic response of foam core sandwich panels as well as aluminum panels with foam inserts. Emphasis is placed on the acoustic absorption performance of the panels versus weight and the effects of the arrangement of the materials and incident wave frequency.

The effect of alumina particles on the microstructural and mechanical properties of copper foams fabricated by space-holder method

NASA Astrophysics Data System (ADS)

Salvo, C.; Aguilar, C.; Lascano, S.; Pérez, L.; López, M.; Mangalaraja, R. V.

2018-05-01

The copper foam is an interesting field of research because of its several advantages as an engineering material. Powder metallurgy presents an alternative route to obtain a porous structure with high strength to weight ratio and functional properties. The viability of processing copper foam separately with two different space-holders such as ammonium hydrogen carbonate (NH4HCO3) and sodium chloride (NaCl) of 50 vol% was studied. The green compacts obtained under 200 MPa were sintered at different cycles for the complete removal of space-holder. The sintered foams were characterized by optical microscopy (OM), scanning electron microscopy (SEM) and uniaxial testing machine (UTM) to study their structural features and compressive strength, respectively. The results showed that NaCl particles were the best alternative to obtain a porous structure, hence two different sizes (1 and 0.01 μm) of alumina (Al2O3) particles with 2, 4 and 6 vol% were used to fabricate copper foams. As a result, a bimodal structure consisting of macro and micropores with a highly interconnected porosity was achieved. In addition, the smaller size alumina particles promoted a higher density of pores, however, the compressive strength was reduced for the higher volume fraction of alumina particles.

Design of Fiber Reinforced Foam Sandwich Panels for Large Ares V Structural Applications

NASA Technical Reports Server (NTRS)

Bednarcyk, Brett A.; Arnold, Steven M.; Hopkins, Dale A.

2010-01-01

The preliminary design of three major structural components within NASA's Ares V heavy lift vehicle using a novel fiber reinforced foam composite sandwich panel concept is presented. The Ares V payload shroud, interstage, and core intertank are designed for minimum mass using this panel concept, which consists of integral composite webs separated by structural foam between two composite facesheets. The HyperSizer structural sizing software, in conjunction with NASTRAN finite element analyses, is used. However, since HyperSizer does not currently include a panel concept for fiber reinforced foam, the sizing was performed using two separate approaches. In the first, the panel core is treated as an effective (homogenized) material, whose properties are provided by the vendor. In the second approach, the panel is treated as a blade stiffened sandwich panel, with the mass of the foam added after completion of the panel sizing. Details of the sizing for each of the three Ares V components are given, and it is demonstrated that the two panel sizing approaches are in reasonable agreement for thinner panel designs, but as the panel thickness increases, the blade stiffened sandwich panel approach yields heavier panel designs. This is due to the effects of local buckling, which are not considered in the effective core property approach.

Closed cell metal foam method

DOEpatents

Patten, James W.

1978-01-01

Foamed metals and metal alloys which have a closed cellular structure are prepared by heating a metal body containing entrapped inert gas uniformly distributed throughout to a temperature above the melting point of the metal and maintaining the body at this temperature a period of time sufficient to permit the entrapped gas to expand, forming individual cells within the molten metal, thus expanding and foaming the molten metal. After cell formation has reached the desired amount, the foamed molten metal body is cooled to below the melting temperature of the metal. The void area or density of the foamed metal is controlled by predetermining the amount of inert gas entrapped in the metal body and by the period of time the metal body is maintained in the molten state. This method is useful for preparing foamed metals and metal alloys from any metal or other material of which a body containing entrapped inert gas can be prepared.

Reticulation of low density shape memory polymer foam with an in vivo demonstration of vascular occlusion

PubMed Central

Rodriguez, Jennifer N.; Miller, Matthew W.; Boyle, Anthony; Horn, John; Yang, Cheng-Kang; Wilson, Thomas S.; Ortega, Jason M.; Small, Ward; Nash, Landon; Skoog, Hunter; Maitland, Duncan J.

2014-01-01

Predominantly closed-cell low density shape memory polymer (SMP) foam was recently reported to be an effective aneurysm filling device in a porcine model (Rodriguez et al., Journal of Biomedical Materials Research Part A 2013: (http://dx.doi.org/10.1002/jbm.a.34782)). Because healing involves blood clotting and cell migration throughout the foam volume, a more open-cell structure may further enhance the healing response. This research sought to develop a non-destructive reticulation process for this SMP foam to disrupt the membranes between pore cells. Non-destructive mechanical reticulation was achieved using a gravity-driven floating nitinol pin array coupled with vibratory agitation of the foam and supplemental chemical etching. Reticulation resulted in a reduced elastic modulus and increased permeability, but did not impede shape memory behavior. Reticulated foams were capable of achieving rapid vascular occlusion in an in vivo porcine model. PMID:25222869

A facile and low-cost micro fabrication material: flash foam.

PubMed

He, Yong; Xiao, Xiao; Wu, Yan; Fu, Jian-zhong

2015-08-28

Although many microfabrication methods have been reported, the preliminary replication templates used in most microfabrication still depend on the expensive and long-period photolithography. This paper explores an alternative replication templates based on a daily used material, flash foam (FF), and proposes a facile microfabrication method, flash foam stamp lithography (FFSL). When FF is exposed with a desired pattern mask, the negative of the pattern is transferred to its surface and micro structures are formed due to the shrinkage of the exposed area. As FF is commonly used in personal stamps, FFSL is very simple and cost-effective. In this paper, we demonstrated that FF is a good and low-cost template for many micro fabrication methods, such as micro casting and soft lithography. Thus, designing and fabricating micro structures at personal office immediately become possible with FFSL. Furthermore, we demonstrated that multi-scale micro structures can be easily fabricated by double exposure with FFSL. Skin textures is used as another case to demonstrate that FFSL can fabricate structures with different depth in a single exposure. As a result, FF shows a promising future in biology, and analytical chemistry, such as rapid fabrication of point of care diagnostics and microfluidic analytical devices with low cost.

Polypyrrole electrodes doped with sulfanilic acid azochromotrop for electrochemical supercapacitors

NASA Astrophysics Data System (ADS)

Chen, S.; Zhitomirsky, I.

2013-12-01

In this work we demonstrate the feasibility of deposition of polypyrrole (PPy) films by electropolymerization on stainless steel substrates and fabrication of PPy powders by chemical polymerization using sulfanilic acid azochromotrop (SPADNS) as a new anionic dopant. The problem of low adhesion of PPy films to stainless steel substrates is addressed by the use of SPADNS, which exhibits chelating properties, promoting film formation. The use of fine particles, prepared by the chemical polymerization method, allows impregnation of Ni foams and fabrication of porous electrodes with high materials loading for electrochemical supercapacitors (ES). PPy films and Ni foam based PPy electrodes show capacitive behaviour in Na2SO4 electrolyte. The electron microscopy studies, impedance spectroscopy data and analysis of the SPADNS structure provide an insight into the factors, controlling capacitive behaviour. The Ni foam based electrodes offer advantages of improved capacitive behaviour at high materials loadings and good cycling stability. The area normalized and volume normalized specific capacitances are as high as 5.43 F cm-2 and 93.6 F cm-3, respectively, for materials loading of 35.4 mg cm-2. The capacitance retention of Ni foam based electrodes is 91.5% after 1000 cycles. The Ni foam based PPy electrodes are promising for application in ES.

Literature Review: An Overview of Epoxy Resin Syntactic Foams with Glass Microballoons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Keller, Jennie

2014-03-12

Syntactic foams are an important category of composite materials that have abundant applications in a wide variety of fields. The bulk phase of syntactic foams is a three-part epoxy resin formulation that consists of a base resin, a curative (curing agent) and a modifier (diluent and/or accelerator) [12]. These thermoset materials [12] are used frequently for their thermal stability [9], low moisture absorption and high compressive strength [10]. The characteristic feature of a syntactic foam is a network of beads that forms pores within the epoxy matrix [3]. In this review, hollow glass beads (known as glass microballoons) are considered,more » however, solid beads or microballoons made from materials such as ceramic, polymer or metal can also be used [3M, Peter]. The network of hollow beads forms a closed-cell foam; the term closed-cell comes from the fact that the microspheres used in the resin matrix are completely closed and filled with gas (termed hollow). In contrast, the microspheres used in open-cell foams are either not completely closed or broken so that matrix material can fill the spheres [11]. Although closed foams have been found to possess higher densities than open cell foams, their rigid structures give them superior mechanical properties [12]. Past research has extensively studied the effects that changing the volume fraction of microballoons to epoxy will have on the resulting syntactic foam [3,4,9]. In addition, published literature also explores how the microballoon wall thickness affects the final product [4,9,10]. Findings detail that indeed both the mechanical and some thermal properties of syntactic foams can be tailored to a specific application by varying either the volume fraction or the wall thickness of the microballoons used [10]. The major trends in syntactic foam research show that microballoon volume fraction has an inversely proportionate relationship to dynamic properties, while microballoon wall thickness is proportional to those same properties [3,4,9,10]. The glass transition temperature has a proportional relationship to the volume fraction of microballoons used, however, there is limited research that supports correlations between other thermal variables and microballoons specifications. In fact, very little experimental data exists to relate thermal conductivity and volume fraction or wall thickness of microballoons [5]. This review proposes that thermal conductivity should be a topic of interest for future researchers because of how frequently syntactic foams are used in insulating applications. This paper will explore three aspects pertaining to epoxy resin syntactic foams with glass microballoons: the immense range of applications that syntactic foams are used for, the materials and fabrication techniques most commonly used, and lastly the results from characterization of syntactic foams with varying microballoon volume fractions and wall thicknesses. In addition to varying microballoon parameters, it is also possible to change the base, accelerator and curing agent used in the epoxy formulation. For simplicity, this paper will focus on a very common combination of materials produced by the Dow Chemical Company®.« less

Pyrophoric metal-carbon foam composites and methods of making the same

DOEpatents

Gash, Alexander E [Brentwood, CA; Satcher, Jr., Joe H.; Simpson, Randall L [Livermore, CA; Baumann, Theodore F [Discovery Bay, CA; Worsley, Marcus A [Belmont, CA

2012-05-08

A method for creating a pyrophoric material according to one embodiment includes thermally activating a carbon foam for creating micropores therein; contacting the activated carbon foam with a liquid solution comprising a metal salt for depositing metal ions in the carbon foam; and reducing the metal ions in the foam to metal particles. A pyrophoric material in yet another embodiment includes a pyrophoric metal-carbon foam composite comprising a carbon foam having micropores and mesopores and a surface area of greater than or equal to about 2000 m.sup.2/g, and metal particles in the pores of the carbon foam. Additional methods and materials are also disclosed.

Next Generation Car — Example of Function Integration at the Light Urban Vehicle (LUV) Vehicle Concept

NASA Astrophysics Data System (ADS)

Kopp, G.; Brückmann, S.; Kriescher, M.; Friedrich, H. E.

In times of climate change vehicle emissions have to be reduced clearly. One possibility is to reduce the mass of the body in white using lightweight sandwich structures. The department `Lightweight and Hybrid Design Methods' of the Institute of Vehicle Concepts develops a vehicle body structure by using sandwiches with aluminum top layers and polyurethane foam as core material. For that the foam and the sandwiches were investigated under different load cases, e.g. pressure loading and in-plane tests. In tests with components the high potential of the sandwich materials were shown. On the dynamic component test facility of the institute, vehicle front structures were tested successfully. The results of all investigations regarding sandwich materials, integration of functions (e.g. crash, thermal) in vehicle structures and the concept LUV are developed under the research program of Next Generation Car of the DLR. We will show the development and results of the LUV.

Correlation between structure and compressive strength in a reticulated glass-reinforced hydroxyapatite foam.

PubMed

Callcut, S; Knowles, J C

2002-05-01

Glass-reinforced hydroxyapatite (HA) foams were produced using reticulated foam technology using a polyurethane template with two different pore size distributions. The mechanical properties were evaluated and the structure analyzed through density measurements, image analysis, X-ray diffraction (XRD) and scanning electron microscopy (SEM). For the mechanical properties, the use of a glass significantly improved the ultimate compressive strength (UCS) as did the use of a second coating. All the samples tested showed the classic three regions characteristic of an elastic brittle foam. From the density measurements, after application of a correction to compensate for the closed porosity, the bulk and apparent density showed a 1 : 1 correlation. When relative bulk density was plotted against UCS, a non-linear relationship was found characteristic of an isotropic open celled material. It was found by image analysis that the pore size distribution did not change and there was no degradation of the macrostructure when replicating the ceramic from the initial polyurethane template during processing. However, the pore size distributions did shift to a lower size by about 0.5 mm due to the firing process. The ceramic foams were found to exhibit mechanical properties typical of isotropic open cellular foams.

Surface Evaluation by XPS of High Performance Foams After Exposure to Oxygen Plasma

NASA Technical Reports Server (NTRS)

Hampton, Michael D.

2001-01-01

This report will present the results of a study done during a 10-week summer faculty fellowship during the summer of 2001 working with Ms. Martha Williams of the Testbeds Group at Kennedy Space Center. The work was in a new area for this faculty and was both interesting and enjoyable. An imide is a compound in which nitrogen is bonded directly to an R group and to two other R groups through carbonyls. Polyimides have a number of properties that make them highly desirable materials for use on structures that are exposed to extreme conditions. They are strong, fire resistant, minimally outgasing, stable over a large temperature range, resistant to chemical attack, transparent to infrared and microwaves, and have a low density. One polyimide, solimide, commercially available as a foam, retains resiliency from -300 F to +500 F, is highly flame retardant, and decomposes with virtually no smoke or toxic byproduct formation. The density of this product is such that its use in place of fiberglass in the lower lobe of a 747 saves 400 lb. Shipboard applications have resulted in literally tons of weight reduction. While polyimide films have been used in structures to be placed in low earth orbit (LEO) for many years, polyimide foams have found only minimal application in this realm. NASA Langley Research Center has developed new technology that allows for the processing of new polyimide foams. The resulting increased availability of these materials, along with their highly desirable properties, has prompted a study to determine the suitability of these materials for use in structures to be placed in LEO.

Characterization and preparation of p(U-MMA-An) interpenetrating polymer network damping and absorbing material.

PubMed

Liu, Jun; Li, Qingshan; Zhuo, Yuguo; Hong, Wei; Lv, Wenfeng; Xing, Guangzhong

2014-06-01

P(U-MMA-ANI) interpenetrating polymer network (IPN) damping and absorbing material is successfully synthesized by PANI particles served as an absorbing agent with the microemulsion polymerization and P(U-MMA) foam IPN network structure for substrate materials with foaming way. P(U-MMA-ANI) IPN is characterized by the compression mechanical performance testing, TG-DSC, and DSC. The results verify that the P(U-MMA) IPN foam damping material has a good compressive strength and compaction cycle property, and the optimum content of PMMA was 40% (mass) with which the SEM graphs do not present the phase separation on the macro level between PMMA and PU, while the phase separation was observed on the micro level. The DTG curve indicates that because of the formation of P(U-MMA) IPN, the decomposition temperature of PMMA and the carbamate in PU increases, while that of the polyol segment in PU has almost no change. P(U-MMA-ANI) IPN foam damping and absorbing material is obtained by PANI particles served as absorbing agent in the form of filler, and PMMA in the form of micro area in substrate material. When the content of PANI was up to 2.0% (mass), the dissipation factor of composites increased, and with the increasing of frequency the dissipation factor increased in a straight line.

Ultra-Lightweight Nanocomposite Foams and Sandwich Structures for Space Structure Applications

NASA Technical Reports Server (NTRS)

Tan, Seng

2012-01-01

Microcellular nanocomposite foams and sandwich structures have been created to have excellent electrical conductivity and radiation-resistant properties using a new method that does not involve or release any toxicity. The nanocomposite structures have been scaled up in size to 12 X 12 in. (30 X 30 cm) for components fabrication. These sandwich materials were fabricated mainly from PE, CNF, and carbon fibers. Test results indicate that they have very good compression and compression-after-impact properties, excellent electrical conductivity, and superior space environment durability. Compression tests show that 1000 ESH (equivalent Sun hours) of UV exposure has no effect on the structural properties of the sandwich structures. The structures are considerably lighter than aluminum alloy (= 36 percent lighter), which translates to 36 percent weight savings of the electronic enclosure and its housing. The good mechanical properties of the materials may enable the electronic housing to be fabricated with a thinner structure that further reduces the weight. There was no difficulty in machining the sandwich specimens into electronic enclosure housing.

Development and characterization of a rechargeable carbon foam electrode containing nickel oxyhydroxide active mass

NASA Astrophysics Data System (ADS)

Chye, Matthew B.

2011-12-01

Batteries and asymmetric electrochemical capacitors using nickel-based positive electrodes can provide high currents due to their defect structure and low internal resistance. Nickel-based positive electrodes, therefore, are ideal for high current applications such as power tools and electric vehicles (EVs). The positive electrodes prepared in this research are monolithic graphitic foams electrochemically impregnated with nickel oxyhydroxide active mass and select additives that enhance electrode performance. Carbon foam is a good current collector due to its light-weight, porous, and graphitic nature, which give its good electrical properties and the ability to be used as a current collector. Replacing sintered nickel current collectors in nickel-based batteries with a low cost, readily available material, carbon foam, can reduce the mass of a rechargeable battery. The goal of this research has been to contribute to fundamental science through better understanding of optimizing the deposition and formation processes of the active mass onto carbon foams as well as investigating the active mass behavior under deposition, formation, and cycling conditions. Flooded cells and a PFA sealed asymmetric capacitor have been used. The effects of carbon foam surface pretreatments and how they affect the active material/carbon foam performance are demonstrated. Also the feasibility of this positive electrode as a component in nickel-based batteries, a Ni-Zn cells and an asymmetric capacitor pouch cell, is demonstrated.

Shock Mitigation in Open-Celled TiNi Foams

NASA Astrophysics Data System (ADS)

Jardine, A. Peter

2018-05-01

High-energy shock events generated by impacts are effectively mitigated by Nitinol materials. Initial evidence of this capability was suggested by the dramatically superior cavitation-erosion performance of Nitinol coatings made by plasma spray processes, over steels and brasses. A fast acting hysteretic stress-strain response mechanism was proposed to explain this result, transforming the shock energy into heat. Extending this work to bulk TiNi, dynamic load characterization using Split Rod Hopkinson Bar techniques on solid porous TiNi confirmed that the mechanical response to high strain rates below 4200 s-1 were indeed hysteretic. This paper reports on dynamical load characterization on TiNi foams made by Self-Propagating High-Temperature Synthesis (SHS) using Split Rod Hopkinson Bar and gas-gun impact characterization to compare these foams to alternative materials. This work verified that SHS-derived TiNi foams were indeed hysteretic at strain rates from 180 to 2300 s-1. In addition, Shock Spectrum Analysis demonstrated that TiNi foams were very effective in mitigating the shock spectrum range below 5 kHz, and that increasing porosity increased the amount of shock attenuation in that spectral range. Finally under impact loading, 55% porous TiNi foams were a factor of 7 superior to steel and a factor of 4 better than Al 6061 or Cu in mitigating peak g-loads and this attenuation improved with bilayer structures of 57 and 73% porous TiNi foam article.

Numerical Evaluation of Mode 1 Stress Intensity Factor as a Function of Material Orientation For BX-265 Foam Insulation Material

NASA Technical Reports Server (NTRS)

Knudsen, Erik; Arakere, Nagaraj K.

2006-01-01

Foam; a cellular material, is found all around us. Bone and cork are examples of biological cell materials. Many forms of man-made foam have found practical applications as insulating materials. NASA uses the BX-265 foam insulation material on the external tank (ET) for the Space Shuttle. This is a type of Spray-on Foam Insulation (SOFI), similar to the material used to insulate attics in residential construction. This foam material is a good insulator and is very lightweight, making it suitable for space applications. Breakup of segments of this foam insulation on the shuttle ET impacting the shuttle thermal protection tiles during liftoff is believed to have caused the space shuttle Columbia failure during re-entry. NASA engineers are very interested in understanding the processes that govern the breakup/fracture of this complex material from the shuttle ET. The foam is anisotropic in nature and the required stress and fracture mechanics analysis must include the effects of the direction dependence on material properties. Material testing at NASA MSFC has indicated that the foam can be modeled as a transversely isotropic material. As a first step toward understanding the fracture mechanics of this material, we present a general theoretical and numerical framework for computing stress intensity factors (SIFs), under mixed-mode loading conditions, taking into account the material anisotropy. We present mode I SIFs for middle tension - M(T) - test specimens, using 3D finite element stress analysis (ANSYS) and FRANC3D fracture analysis software, developed by the Cornel1 Fracture Group. Mode I SIF values are presented for a range of foam material orientations. Also, NASA has recorded the failure load for various M(T) specimens. For a linear analysis, the mode I SIF will scale with the far-field load. This allows us to numerically estimate the mode I fracture toughness for this material. The results represent a quantitative basis for evaluating the strength and fracture properties of anisotropic foam insulation material.

Cellulose Fibre-Reinforced Biofoam for Structural Applications

PubMed Central

Obradovic, Jasmina; Voutilainen, Mikko; Virtanen, Pasi; Lassila, Lippo; Fardim, Pedro

2017-01-01

Traditionally, polymers and macromolecular components used in the foam industry are mostly derived from petroleum. The current transition to a bio-economy creates demand for the use of more renewable feedstocks. Soybean oil is a vegetable oil, composed mainly of triglycerides, that is suitable material for foam production. In this study, acrylated epoxidized soybean oil and variable amounts of cellulose fibres were used in the production of bio-based foam. The developed macroporous bio-based architectures were characterised by several techniques, including porosity measurements, nanoindentation testing, scanning electron microscopy, and thermogravimetric analysis. It was found that the introduction of cellulose fibres during the foaming process was necessary to create the three-dimensional polymer foams. Using cellulose fibres has potential as a foam stabiliser because it obstructs the drainage of liquid from the film region in these gas-oil interfaces while simultaneously acting as a reinforcing agent in the polymer foam. The resulting foams possessed a porosity of approximately 56%, and the incorporation of cellulose fibres did not affect thermal behaviour. Scanning electron micrographs showed randomly oriented pores with irregular shapes and non-uniform pore size throughout the samples. PMID:28772981

Formation of Foam-like Microstructural Carbon Material by Carbonization of Porous Coordination Polymers through a Ligand-Assisted Foaming Process.

PubMed

Kongpatpanich, Kanokwan; Horike, Satoshi; Fujiwara, Yu-Ichi; Ogiwara, Naoki; Nishihara, Hirotomo; Kitagawa, Susumu

2015-09-14

Porous carbon material with a foam-like microstructure has been synthesized by direct carbonization of porous coordination polymer (PCP). In situ generation of foaming agents by chemical reactions of ligands in PCP during carbonization provides a simple way to create lightweight carbon material with a foam-like microstructure. Among several substituents investigated, the nitro group has been shown to be the key to obtain the unique foam-like microstructure, which is due to the fast kinetics of gas evolution during carbonization. Foam-like microstructural carbon materials showed higher pore volume and specific capacitance compared to a microporous carbon. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Morphology and Gas-Sensing Properties of Tin Oxide Foams with Dual Pore Structure

NASA Astrophysics Data System (ADS)

Nam, Kyungju; Kim, Hyeong-Gwan; Choi, Hyelim; Park, Hyeji; Kang, Jin Soo; Sung, Yung-Eun; Lee, Hee Chul; Choe, Heeman

2017-06-01

Tin oxide is a commonly used gas-sensing material, which can be applied as an n- or p-type gas sensor. To improve the gas-sensing performance of tin oxide, we successfully synthesized tin oxide foam via an ice-templating or freeze-casting method. The tin oxide foam samples showed different morphological features depending on the major processing parameters, which include sintering temperature, sintering time, and the amount of added powder. Based on scanning electron microscopy images, we could identify dual pore structure of tin oxide foam containing `wall' pores ranging from 5.3 μm to 10.7 μm, as well as smaller secondary pores (a few micrometers in size) on the wall surfaces. Gas-sensing performance tests for the synthesized tin oxide foams reveal a sensitivity of 13.1, a response time of 192 s, and a recovery time of 160 s at an ethanol gas concentration of 60 ppm at 300°C. This is a remarkable result given that it showed p-type semiconductor behavior and was used without the addition of any catalyst.

Comprehensive Shuttle Foam Debris Reduction Strategies

NASA Technical Reports Server (NTRS)

Semmes, Edmund B.

2007-01-01

The Columbia Accident Investigation Board (CAIB) was clear in its assessment of the loss of the Space Shuttle Columbia on February 3, 2003. Foam liberated from the External Tank (ET) impacting the brittle wing leading edge (WLE) of the orbiter causing the vehicle to disintegrate upon re-entry. Naturally, the CAB pointed out numerous issues affecting this exact outcome in hopes of correcting systems of systems failures any one of which might have altered the outcome. However, Discovery s recent return to flight (RTF) illustrates the primacy of erosion of foam and the risk of future undesirable outcomes. It is obvious that the original RTF focused approach to this problem was not equal to a comprehensive foam debris reduction activity consistent with the high national value of the Space Shuttle assets. The root cause is really very simple when looking at the spray-on foam insulation for the entire ET as part of the structure (e.g., actual stresses > materials allowable) rather than as some sort of sizehime limited ablator. This step is paramount to accepting the CAB recommendation of eliminating debris or in meeting any level of requirements due to the fundamental processes ensuring structural materials maintain their integrity. Significant effort has been expended to identify root cause of the foam debris In-Flight Anomaly (FA) of STS-114. Absent verifiable location specific data pre-launch (T-0) and in-flight, only a most probable cause can be identified. Indeed, the literature researched corroborates NASNTM-2004-2 13238 disturbing description of ill defined materials characterization, variable supplier constituents and foam processing irregularities. Also, foam is sensitive to age and the exposed environment making baseline comparisons difficult without event driven data. Conventional engineering processes account for such naturally occurring variability by always maintaining positive margins. Success in a negative margin range is not consistently achieved. Looking at the ET S spray-on foam insulation as part of the structural system (e.g., glass half full mentality) will create an environment where ET debris levels as low as reasonably achievable (ALARA) can be realized. ALARA is a NASA requirements philosophy deployed for the complex, mission altering radiation exposure requirements for life safety of astronauts. In the Shuttle s case, reasonableness is established by exhaustive engineering rigor, allowable debris size/quantity, technology maturity and programmatic constraints. A more robust urethane foam thermal protection system (TPS) will enhance the hctionality of the new Ares I Crew Launch Vehicle (CLV) Upper Stage. This paper will outline the strategy for a comprehensive effort to reduce ET foam debris and outline steps leading to an improved foam TPS. The NASA must remain committed to such an approach no matter what becomes of the next flight s actual debris field lest we fall back into a false sense of security. This commitment along with full implementation of all the other CAB recommendations such as orbiter hardening will significantly improve the Shuttle system, the engineering workforce, future capabilities & alternate policy offramps, national human resource protection, high value national asset protection and increase the level of service to the overall NASA mission.

Structural integrity of power generating speed bumps made of concrete foam composite

NASA Astrophysics Data System (ADS)

Syam, B.; Muttaqin, M.; Hastrino, D.; Sebayang, A.; Basuki, W. S.; Sabri, M.; Abda, S.

2018-02-01

In this paper concrete foam composite speed bumps were designed to generate electrical power by utilizing the movements of commuting vehicles on highways, streets, parking gates, and drive-thru station of fast food restaurants. The speed bumps were subjected to loadings generated by vehicles pass over the power generating mechanical system. In this paper, we mainly focus our discussion on the structural integrity of the speed bumps and discuss the electrical power generating speed bumps in another paper. One aspect of structural integrity is its ability to support designed loads without breaking and includes the study of past structural failures in order to prevent failures in future designs. The concrete foam composites were used for the speed bumps; the reinforcement materials are selected from empty fruit bunch of oil palm. In this study, the speed bump materials and structure were subjected to various tests to obtain its physical and mechanical properties. To analyze the structure stability of the speed bumps some models were produced and tested in our speed bump test station. We also conduct a FEM-based computer simulation to analyze stress responses of the speed bump structures. It was found that speed bump type 1 significantly reduced the radial voltage. In addition, the speed bump is equipped with a steel casing is also suitable for use as a component component in generating electrical energy.

The applicability of different waste materials for the production of lightweight aggregates.

PubMed

Ducman, V; Mirtic, B

2009-08-01

The applicability of different waste materials for the production of lightweight aggregates has been studied. The following waste materials were investigated: silica sludge, superfluous clay in the quarry, waste glass, and residue from the polishing process of different types of stone. SiC and MnO(2) were selected as foaming agents. Feldspar containing minerals and scrap glass were added in order to lower the softening point of the waste materials. The granules were prepared by mixing together finely ground waste with one or both of the selected foaming agents. The granules were then fired at different temperatures above the softening point of the glassy phase within the temperature range from 1150 to 1220 degrees C, where the foaming agent degasses, and the resulting gasses remain trapped in the glassy structure. The foaming process was observed by hot-stage microscopy. The properties of the so-obtained granules, such as their apparent density and compressive strength, were determined, and their microstructures were evaluating using SEM and polarizing microscopy. With the addition to clay of polishing residue from granite-like rocks, after firing at 1220 degrees C homogeneously porous granules with a density down to 0.42 g/cm(3) were obtained, whereas with the addition to waste silica sludge of polishing residue from granite-like rocks and waste glass with a foaming agent, after firing at 1220 degrees C densities from 0.57 to 0.82 g/cm(3) were obtained.

Thermal control structure and garment

DOEpatents

Klett, James W [Knoxville, TN; Cameron, Christopher Stan [Sanford, NC

2012-03-13

A flexible thermally conductive structure. The structure generally includes a plurality of thermally conductive yarns, at least some of which are at least partially disposed adjacent to an elastomeric material. Typically, at least a portion of the plurality of thermally conductive yarns is configured as a sheet. The yarns may be constructed from graphite, metal, or similar materials. The elastomeric material may be formed from urethane or silicone foam that is at least partially collapsed, or from a similar material. A thermal management garment is provided, the garment incorporating a flexible thermally conductive structure.

Prosthesis Material

NASA Technical Reports Server (NTRS)

1995-01-01

FAB/CAM, a subsidiary of the Harshberger Prosthetic and Orthotic Center, Inc., approached Marshall for help in replacing the heavy, fragile plaster they used to produce master molds for prosthetics. Concurrently, Marshall and Martin Marietta were creating a commercial derivative of the foam insulation used to protect the Space Shuttle External Tank from excessive heat. FAB/CAM found the foam blanks to be lighter, cheaper and easier to manufacture than plaster, resulting in lower costs to the consumer. Martin Marietta markets the foam system, MARCORE, for the prosthesis market. The system also has commercial potential in high temperature insulation and structural applications.

Two approaches for introduction of wheat straw lignin into rigid polyurethane foams

NASA Astrophysics Data System (ADS)

Arshanitsa, A.; Paberza, A.; Vevere, L.; Cabulis, U.; Telysheva, G.

2014-05-01

In present work the BIOLIGNIN{trade mark, serif} obtained in the result of wheat straw organosolv processing in CIMV pilot plant (France) was investigated as a component of rigid polyurethanes (PUR) foam systems. Different separate approaches of lignin introduction into PUR foam system were studied: as filler without chemical preprocessing and as liquid lignopolyol obtained by lignin oxypropylation in alkali conditions. The incorporation of increasing amount of lignin as filler into reference PUR foam systems on the basis of mixture of commercial polyethers Lupranol 3300 and Lupranol 3422 steadily decreased the compression characteristics of foams, their dimensional stability and hydrophobicity. The complete substitution of Lupranol 3300 by lignopolyol increases its cell structure uniformity and dimensional stability and does not reduce the physical-mechanical properties of foam. In both cases the incorporation of lignin into PUR foam leads to the decreasing of maximum values of thermodegradation rates. The lignin filler can be introduced into lignopolyol based PUR foam in higher quantity than in the reference Lupranol based PUR without reduction of compression characteristics of material. In this work the optimal lignin content in the end product - PUR foam as both polyol and filler is 16%.

Supercritical CO2 foaming of thermoplastic materials derived from maize: proof-of-concept use in mammalian cell culture applications.

PubMed

Trujillo-de Santiago, Grissel; Portales-Cabrera, Cynthia Guadalupe; Portillo-Lara, Roberto; Araiz-Hernández, Diana; Del Barone, Maria Cristina; García-López, Erika; Rojas-de Gante, Cecilia; de Los Angeles De Santiago-Miramontes, María; Segoviano-Ramírez, Juan Carlos; García-Lara, Silverio; Rodríguez-González, Ciro Ángel; Alvarez, Mario Moisés; Di Maio, Ernesto; Iannace, Salvatore

2015-01-01

Foams are high porosity and low density materials. In nature, they are a common architecture. Some of their relevant technological applications include heat and sound insulation, lightweight materials, and tissue engineering scaffolds. Foams derived from natural polymers are particularly attractive for tissue culture due to their biodegradability and bio-compatibility. Here, the foaming potential of an extensive list of materials was assayed, including slabs elaborated from whole flour, the starch component only, or the protein fraction only of maize seeds. We used supercritical CO2 to produce foams from thermoplasticized maize derived materials. Polyethylene-glycol, sorbitol/glycerol, or urea/formamide were used as plasticizers. We report expansion ratios, porosities, average pore sizes, pore morphologies, and pore size distributions for these materials. High porosity foams were obtained from zein thermoplasticized with polyethylene glycol, and from starch thermoplasticized with urea/formamide. Zein foams had a higher porosity than starch foams (88% and 85%, respectively) and a narrower and more evenly distributed pore size. Starch foams exhibited a wider span of pore sizes and a larger average pore size than zein (208.84 vs. 55.43 μm2, respectively). Proof-of-concept cell culture experiments confirmed that mouse fibroblasts (NIH 3T3) and two different prostate cancer cell lines (22RV1, DU145) attached to and proliferated on zein foams. We conducted screening and proof-of-concept experiments on the fabrication of foams from cereal-based bioplastics. We propose that a key indicator of foamability is the strain at break of the materials to be foamed (as calculated from stress vs. strain rate curves). Zein foams exhibit attractive properties (average pore size, pore size distribution, and porosity) for cell culture applications; we were able to establish and sustain mammalian cell cultures on zein foams for extended time periods.

Supercritical CO2 Foaming of Thermoplastic Materials Derived from Maize: Proof-of-Concept Use in Mammalian Cell Culture Applications

PubMed Central

Trujillo-de Santiago, Grissel; Portales-Cabrera, Cynthia Guadalupe; Portillo-Lara, Roberto; Araiz-Hernández, Diana; Del Barone, Maria Cristina; García-López, Erika; Rojas-de Gante, Cecilia; de los Angeles De Santiago-Miramontes, María; Segoviano-Ramírez, Juan Carlos; García-Lara, Silverio; Rodríguez-González, Ciro Ángel; Alvarez, Mario Moisés; Di Maio, Ernesto; Iannace, Salvatore

2015-01-01

Background Foams are high porosity and low density materials. In nature, they are a common architecture. Some of their relevant technological applications include heat and sound insulation, lightweight materials, and tissue engineering scaffolds. Foams derived from natural polymers are particularly attractive for tissue culture due to their biodegradability and bio-compatibility. Here, the foaming potential of an extensive list of materials was assayed, including slabs elaborated from whole flour, the starch component only, or the protein fraction only of maize seeds. Methodology/Principal Findings We used supercritical CO2 to produce foams from thermoplasticized maize derived materials. Polyethylene-glycol, sorbitol/glycerol, or urea/formamide were used as plasticizers. We report expansion ratios, porosities, average pore sizes, pore morphologies, and pore size distributions for these materials. High porosity foams were obtained from zein thermoplasticized with polyethylene glycol, and from starch thermoplasticized with urea/formamide. Zein foams had a higher porosity than starch foams (88% and 85%, respectively) and a narrower and more evenly distributed pore size. Starch foams exhibited a wider span of pore sizes and a larger average pore size than zein (208.84 vs. 55.43 μm2, respectively). Proof-of-concept cell culture experiments confirmed that mouse fibroblasts (NIH 3T3) and two different prostate cancer cell lines (22RV1, DU145) attached to and proliferated on zein foams. Conclusions/Significance We conducted screening and proof-of-concept experiments on the fabrication of foams from cereal-based bioplastics. We propose that a key indicator of foamability is the strain at break of the materials to be foamed (as calculated from stress vs. strain rate curves). Zein foams exhibit attractive properties (average pore size, pore size distribution, and porosity) for cell culture applications; we were able to establish and sustain mammalian cell cultures on zein foams for extended time periods. PMID:25859853

Microgravity Foam Structure and Rheology

NASA Technical Reports Server (NTRS)

Durian, Douglas J.

1997-01-01

To exploit rheological and multiple-light scattering techniques, and ultimately microgravity conditions, in order to quantify and elucidate the unusual elastic character of foams in terms of their underlying microscopic structure and dynamics. Special interest is in determining how this elastic character vanishes, i.e. how the foam melts into a simple viscous liquid, as a function of both increasing liquid content and shear strain rate. The unusual elastic character of foams will be quantified macroscopically by measurement of the shear stress as a function of static shear strain, shear strain rate, and time following a step strain; such data will be analyzed in terms of a yield stress, a static shear modulus, and dynamical time scales. Microscopic information about bubble packing and rearrangement dynamics, from which these macroscopic non-Newtonian properties presumably arise, will be obtained non-invasively by novel multiple-light scattering diagnostics such as Diffusing-Wave Spectroscopy (DWS). Quantitative trends with materials parameters, such as average bubble size, and liquid content, will be sought in order to elucidate the fundamental connection between the microscopic structure and dynamics and the macroscopic rheology.

Synthesis of palm oil fatty acid as foaming agent for firefighting application

NASA Astrophysics Data System (ADS)

Rivai, M.; Hambali, E.; Suryani, A.; Fitria, R.; Firmansyah, S.; Pradesi, J.

2017-05-01

Many factors including natural factor, human carelessness, new land clearance or agricultural burning/act of vandalism and ground fire are suspected as the causes of forest fire. Foam, which cools the fire down, covers the burning material/fuel, and avoids contact between burning materials with oxygen, is an effective material used to fight large-scale fires. For this purpose, surfactant which can facilitate foam formation and inhibit the spread of smoke is required. This study was aimed at producing prototype product of foaming agent from palm oil and its formulation as a fire fighting material. Before the formulation stage, the foaming agent was resulted from saponification process of oleic, lauric, and palmitic acids by using NaOH and KOH alkaline. Foam stability was used as the main indicator of foaming agent. Results showed that potassium palmitate had the highest foam stability of 82% until the 3rd day. The best potassium palmitate concentration was 7%.

Biomimetic cellular metals-using hierarchical structuring for energy absorption.

PubMed

Bührig-Polaczek, A; Fleck, C; Speck, T; Schüler, P; Fischer, S F; Caliaro, M; Thielen, M

2016-07-19

Fruit walls as well as nut and seed shells typically perform a multitude of functions. One of the biologically most important functions consists in the direct or indirect protection of the seeds from mechanical damage or other negative environmental influences. This qualifies such biological structures as role models for the development of new materials and components that protect commodities and/or persons from damage caused for example by impacts due to rough handling or crashes. We were able to show how the mechanical properties of metal foam based components can be improved by altering their structure on various hierarchical levels inspired by features and principles important for the impact and/or puncture resistance of the biological role models, rather than by tuning the properties of the bulk material. For this various investigation methods have been established which combine mechanical testing with different imaging methods, as well as with in situ and ex situ mechanical testing methods. Different structural hierarchies especially important for the mechanical deformation and failure behaviour of the biological role models, pomelo fruit (Citrus maxima) and Macadamia integrifolia, were identified. They were abstracted and transferred into corresponding structural principles and thus hierarchically structured bio-inspired metal foams have been designed. A production route for metal based bio-inspired structures by investment casting was successfully established. This allows the production of complex and reliable structures, by implementing and combining different hierarchical structural elements found in the biological concept generators, such as strut design and integration of fibres, as well as by minimising casting defects. To evaluate the structural effects, similar investigation methods and mechanical tests were applied to both the biological role models and the metallic foams. As a result an even deeper quantitative understanding of the form-structure-function relationship of the biological concept generators as well as the bio-inspired metal foams was achieved, on deeper hierarchical levels and overarching different levels.

Design and Optimization of New Metallic Materials (Metal Foams) for the Reduction of the Noise of the Aeronautical Turbo Engines

DTIC Science & Technology

2005-02-01

AApproved for Public Release Distribution Unlimited SANS MENTION DE PROTECTION MATERIALS AND STRUCTURES -1- ONERA BP 72 - 29. avenue de la Division Leclerc...reduction. Finding the best solution in terns balancing structural strength and acoustic properties was the main thrust of this project. Acoustic...material system for noise reduction. Finding the best solution in terms balancing structural strength and acoustic properties was the main thrust of this

Polyaniline-encapsulated silicon on three-dimensional carbon nanotubes foam with enhanced electrochemical performance for lithium-ion batteries

NASA Astrophysics Data System (ADS)

Zhou, Xiaoming; Liu, Yang; Du, Chunyu; Ren, Yang; Mu, Tiansheng; Zuo, Pengjian; Yin, Geping; Ma, Yulin; Cheng, Xinqun; Gao, Yunzhi

2018-03-01

Seeking free volume around nanostructures for silicon-based anodes has been a crucial strategy to improve cycling and rate performance in the next generation Li-ion batteries. Herein, through a simple pyrolysis and in-situ polymerization approach, the low cost commercially available melamine foam as a soft template converts carbon nanotubes into highly dispersed and three-dimensionally interconnected framework with encapsulated silicon/polyaniline hierarchical nanoarchitecture. This unique core-sheath structure based on carbon nanotubes foam integrates a large number of mesoporous, thus providing well-accessible space for electrolyte wetting, whereas the carbon nanotubes matrix serves as conductive thoroughfares for electron transport. Meanwhile, the outer polyaniline coated on silicon nanoparticles provides effective space for volume expansion of silicon, further inhibiting the active material escape from the current collector. As expected, the PANI-Si@CNTs foam exhibits a high initial specific capacity of 1954 mAh g-1 and retains 727 mAh g-1 after 100 cycles at 100 mA g-1, which can be attributed to highly electrical conductivity of carbon nanotubes and protective layer of polyaniline sheath, together with three-dimensionally interconnected porous skeleton. This facile structure can pave a way for large scale synthesis of high durable silicon-based anodes or other electrode materials with huge volume expansion.

Laser-driven heat-front propagation in foam vs. gas

NASA Astrophysics Data System (ADS)

Pérez, F.; Colvin, J. D.; May, M. J.; Gammon, S. A.; Fournier, K. B.

2014-10-01

A high-energy laser (several kJ, 1015 W/cm2) can propagate inside an underdense plasma over millimeters, along its associated heat front. This creates a large volume of hot plasma (several keV) able to produce bright hard-x-ray sources when a high-Z dopant is included in the material. In the past years, we investigated the behavior of both gases and foams under these circumstances. Their design and predictability relies on the understanding of the heat front propagation. In the case of foams, several studies tried to assess the effect of their micro-structure in altering the laser interaction and the heat front propagation, but no experimental data has shown clear evidence. We present here the design and results of a recent experiment, using the OMEGA laser, where a Ge-doped silica foam was compared to a Ne/Kr gas of very similar characteristics, the only difference between these two materials being their micro-structure to allow for a straightforward determination of its influence. The design of future similar experiments will also be reported. J. Colvin presents theoretical and modeling aspects of this subject in a companion presentation. This work was performed under the auspices of the U.S. Department of Energy by LLNL under Contract No. DE-AC52-07NA27344.

Experimental study of a passive thermal management system for high-powered lithium ion batteries using porous metal foam saturated with phase change materials

NASA Astrophysics Data System (ADS)

Li, W. Q.; Qu, Z. G.; He, Y. L.; Tao, Y. B.

2014-06-01

A highly efficient thermal strategy to manage a high-powered Li-ion battery package within the required safe temperature range is of great demand for electric vehicles (EVs) applications. A sandwiched cooling structure using copper metal foam saturated with phase change materials was designed. The thermal efficiency of the system was experimentally evaluated and compared with two control cases: a cooling mode with pure phase change materials and an air-cooling mode. The results showed that the thermal management with air natural convection cannot fulfill the safety demand of the Li-ion battery. The use of pure PCM can dramatically reduce the surface temperature and maintain the temperature within an allowable range due to the latent heat absorption and the natural convection of the melted PCM during the melting process. The foam-paraffin composite further reduced the battery's surface temperature and improved the uniformity of the temperature distribution caused by the improvement of the effective thermal conductivity. Additionally, the battery surface temperature increased with an increase in the porosity and the pore density of the metal foam.

Low density biodegradable shape memory polyurethane foams for embolic biomedical applications

PubMed Central

Singhal, Pooja; Small, Ward; Cosgriff-Hernandez, Elizabeth; Maitland, Duncan J; Wilson, Thomas S

2014-01-01

Low density shape memory polymer foams hold significant interest in the biomaterials community for their potential use in minimally invasive embolic biomedical applications. The unique shape memory behavior of these foams allows them to be compressed to a miniaturized form, which can be delivered to an anatomical site via a transcatheter process, and thereafter actuated to embolize the desired area. Previous work in this field has described the use of a highly covalently crosslinked polymer structure for maintaining excellent mechanical and shape memory properties at the application-specific ultra low densities. This work is aimed at further expanding the utility of these biomaterials, as implantable low density shape memory polymer foams, by introducing controlled biodegradability. A highly covalently crosslinked network structure was maintained by use of low molecular weight, symmetrical and polyfunctional hydroxyl monomers such as Polycaprolactone triol (PCL-t, Mn 900 g), N,N,N0,N0-Tetrakis (hydroxypropyl) ethylenediamine (HPED), and Tris (2-hydroxyethyl) amine (TEA). Control over the degradation rate of the materials was achieved by changing the concentration of the degradable PCL-t monomer, and by varying the material hydrophobicity. These porous SMP materials exhibit a uniform cell morphology and excellent shape recovery, along with controllable actuation temperature and degradation rate. We believe that they form a new class of low density biodegradable SMP scaffolds that can potentially be used as “smart” non-permanent implants in multiple minimally invasive biomedical applications. PMID:24090987

High-strength cellular ceramic composites with 3D microarchitecture.

PubMed

Bauer, Jens; Hengsbach, Stefan; Tesari, Iwiza; Schwaiger, Ruth; Kraft, Oliver

2014-02-18

To enhance the strength-to-weight ratio of a material, one may try to either improve the strength or lower the density, or both. The lightest solid materials have a density in the range of 1,000 kg/m(3); only cellular materials, such as technical foams, can reach considerably lower values. However, compared with corresponding bulk materials, their specific strength generally is significantly lower. Cellular topologies may be divided into bending- and stretching-dominated ones. Technical foams are structured randomly and behave in a bending-dominated way, which is less weight efficient, with respect to strength, than stretching-dominated behavior, such as in regular braced frameworks. Cancellous bone and other natural cellular solids have an optimized architecture. Their basic material is structured hierarchically and consists of nanometer-size elements, providing a benefit from size effects in the material strength. Designing cellular materials with a specific microarchitecture would allow one to exploit the structural advantages of stretching-dominated constructions as well as size-dependent strengthening effects. In this paper, we demonstrate that such materials may be fabricated. Applying 3D laser lithography, we produced and characterized micro-truss and -shell structures made from alumina-polymer composite. Size-dependent strengthening of alumina shells has been observed, particularly when applied with a characteristic thickness below 100 nm. The presented artificial cellular materials reach compressive strengths up to 280 MPa with densities well below 1,000 kg/m(3).

Investigation of heat transfer in cereal-based foam from a micro-scale perspective using the lattice Boltzmann method

NASA Astrophysics Data System (ADS)

Mack, Simone; Hussein, Mohamed A.; Becker, Thomas

2011-12-01

Foam materials are multicomponent and multiphase systems, where under the influence of heat several temperature-dependent processes occur. In cereal-based foams these processes include protein denaturation, starch gelatinization, phase changes such as water evaporation, and structural changes covering bubble expansion and coalescence. This research focuses on modeling heat transfer processes in cereal foams under thermal treatment from a microstructural point of view. The complex thermo-fluidic processes inside the foam are considered for the solid and the gaseous phase, respectively. Additionally, the microstructural foam characteristics are modified to establish their effect on the overall heat transfer rate, and the micro-scale dynamics are introduced by means of lattice Boltzmann methods (LBM). The objective of this study is to deliver sophisticated insight into the impact of structural properties, due to the fact that optimized parameters would help to improve the bakery industry by means of reduction in baking time, energy, and costs. The results show that altering the porosity and/or the interconnectivity of gas pores in bread crumb influences the overall heat transfer. In comparison to foams having a porosity of 55% and discrete pores, the impact of coalescence exhibits a reduction of baking time of about 2 min. Increasing the porosity about 20% results in reducing the baking time about 7 min.

Insert Design and Manufacturing for Foam-Core Composite Sandwich Structures

NASA Astrophysics Data System (ADS)

Lares, Alan

Sandwich structures have been used in the aerospace industry for many years. The high strength to weight ratios that are possible with sandwich constructions makes them desirable for airframe applications. While sandwich structures are effective at handling distributed loads such as aerodynamic forces, they are prone to damage from concentrated loads at joints or due to impact. This is due to the relatively thin face-sheets and soft core materials typically found in sandwich structures. Carleton University's Uninhabited Aerial Vehicle (UAV) Project Team has designed and manufactured a UAV (GeoSury II Prototype) which features an all composite sandwich structure fuselage structure. The purpose of the aircraft is to conduct geomagnetic surveys. The GeoSury II Prototype serves as the test bed for many areas of research in advancing UAV technologies. Those areas of research include: low cost composite materials manufacturing, geomagnetic data acquisition, obstacle detection, autonomous operations and magnetic signature control. In this thesis work a methodology for designing and manufacturing inserts for foam-core sandwich structures was developed. The results of this research work enables a designer wishing to design a foam-core sandwich airframe structure, a means of quickly manufacturing optimized inserts for the safe introduction of discrete loads into the airframe. The previous GeoSury II Prototype insert designs (v.1 & v.2) were performance tested to establish a benchmark with which to compare future insert designs. Several designs and materials were considered for the new v.3 inserts. A plug and sleeve design was selected, due to its ability to effectively transfer the required loads to the sandwich structure. The insert material was chosen to be epoxy, reinforced with chopped carbon fibre. This material was chosen for its combination of strength, low mass and also compatibility with the face-sheet material. The v.3 insert assembly is 60% lighter than the previous insert designs. A casting process for manufacturing the v.3 inserts was developed. The developed casting process, when producing more than 13 inserts, becomes more economical than machining. An exploratory study was conducted looking at the effects of dynamic loading on the v.3 insert performance. The results of this study highlighted areas for improving dynamic testing of foam-core sandwich structure inserts. Correlations were developed relating design variables such as face-sheet thickness and insert diameter to a failure load for different load cases. This was done through simulations using Computer Aided Engineering (CAE) software, and experimental testing. The resulting correlations were integrated into a computer program which outputs the required insert dimensions given a set of design parameters, and load values.

Springback Foam

NASA Technical Reports Server (NTRS)

1979-01-01

A decade ago, NASA's Ames Research Center developed a new foam material for protective padding of airplane seats. Now known as Temper Foam, the material has become one of the most widely-used spinoffs. Latest application is a line of Temper Foam cushioning produced by Edmont-Wilson, Coshocton, Ohio for office and medical furniture. The example pictured is the Classic Dental Stool, manufactured by Dentsply International, Inc., York, Pennsylvania, one of four models which use Edmont-Wilson Temper Foam. Temper Foam is an open-cell, flameresistant foam with unique qualities.

Preparation and characterization of phase transition/graphite foam composite materials.

PubMed

Yu, Jia; Tang, ChenLong; Yu, ZhiChao

2016-07-04

Phase transition/graphite foam (PCM/GF) composite materials are a kind of composite materials that fill graphite foam with phase change materials. In this paper, graphite foam was prepared firstly by the soft template method, the heat conductivity of which at room temperature is 5.44 W/(m∙K). Then, four phase change materials including eicosane, acetamide, xylitol, and erythritol were chosen for filling into the prepared graphite foam to obtain PCM/GF composite materials. Among the four kinds of materials, erythritol composite material has the highest melting point (118.5°C) and the highest enthalpy of fusion (266.3J/g), weight loss ratios of xylitol composite material after ten cycles is the lowest (2.1%), the compressive strength of xylitol composite material is the highest (9.08 MPa) and that of eicosane composite material is the lowest (3.32 MPa).

46 CFR 164.013-3 - Material properties and workmanship.

Code of Federal Regulations, 2010 CFR

2010-10-01

..., AND MATERIALS: SPECIFICATIONS AND APPROVAL MATERIALS Foam, Unicellular Polyethylene (Buoyant, Slab... polyethylene foam shall be all new material complying with the requirements outlined in this specification. Unicellular polyethylene foam must comply with the requirements of UL 1191, sections 24, 25, and 26 and its...

46 CFR 164.013-3 - Material properties and workmanship.

Code of Federal Regulations, 2011 CFR

2011-10-01

..., AND MATERIALS: SPECIFICATIONS AND APPROVAL MATERIALS Foam, Unicellular Polyethylene (Buoyant, Slab... polyethylene foam shall be all new material complying with the requirements outlined in this specification. Unicellular polyethylene foam must comply with the requirements of UL 1191, sections 24, 25, and 26 and its...

Reticulation of low density shape memory polymer foam with an in vivo demonstration of vascular occlusion

DOE PAGES

Rodriguez, Jennifer N.; Miller, Matthew W.; Boyle, Anthony; ...

2014-08-11

Recently, predominantly closed-cell low density shape memory polymer (SMP) foam was reported to be an effective aneurysm filling device in a porcine model (Rodriguez et al., Journal of Biomedical Materials Research Part A 2013: (http://dx.doi.org/10.1002/jbm.a.34782)). Because healing involves blood clotting and cell migration throughout the foam volume, a more open-cell structure may further enhance the healing response. This research sought to develop a non-destructive reticulation process for this SMP foam to disrupt the membranes between pore cells. Non-destructive mechanical reticulation was achieved using a gravity-driven floating nitinol pin array coupled with vibratory agitation of the foam and supplemental chemical etching.more » Lastly, reticulation resulted in a reduced elastic modulus and increased permeability, but did not impede the shape memory behavior. Reticulated foams were capable of achieving rapid vascular occlusion in an in vivo porcine model.« less

Assessment of Technologies for the Space Shuttle External Tank Thermal Protection System and Recommendations for Technology Improvement. Part 2; Structural Analysis Technologies and Modeling Practices

NASA Technical Reports Server (NTRS)

Knight, Norman F., Jr.; Nemeth, Michael P.; Hilburger, Mark W.

2004-01-01

A technology review and assessment of modeling and analysis efforts underway in support of a safe return to flight of the thermal protection system (TPS) for the Space Shuttle external tank (ET) are summarized. This review and assessment effort focuses on the structural modeling and analysis practices employed for ET TPS foam design and analysis and on identifying analysis capabilities needed in the short-term and long-term. The current understanding of the relationship between complex flight environments and ET TPS foam failure modes are reviewed as they relate to modeling and analysis. A literature review on modeling and analysis of TPS foam material systems is also presented. Finally, a review of modeling and analysis tools employed in the Space Shuttle Program is presented for the ET TPS acreage and close-out foam regions. This review includes existing simplified engineering analysis tools are well as finite element analysis procedures.

Honeycomb-laminate composite structure

NASA Technical Reports Server (NTRS)

Gilwee, W. J., Jr.; Parker, J. A. (Inventor)

1977-01-01

A honeycomb-laminate composite structure was comprised of: (1) a cellular core of a polyquinoxaline foam in a honeycomb structure, and (2) a layer of a noncombustible fibrous material impregnated with a polyimide resin laminated on the cellular core. A process for producing the honeycomb-laminate composite structure and articles containing the honeycomb-laminate composite structure is described.

A facile and low-cost micro fabrication material: flash foam

PubMed Central

He, Yong; Xiao, Xiao; Wu, Yan; Fu, Jian-zhong

2015-01-01

Although many microfabrication methods have been reported, the preliminary replication templates used in most microfabrication still depend on the expensive and long-period photolithography. This paper explores an alternative replication templates based on a daily used material, flash foam (FF), and proposes a facile microfabrication method, flash foam stamp lithography (FFSL). When FF is exposed with a desired pattern mask, the negative of the pattern is transferred to its surface and micro structures are formed due to the shrinkage of the exposed area. As FF is commonly used in personal stamps, FFSL is very simple and cost-effective. In this paper, we demonstrated that FF is a good and low-cost template for many micro fabrication methods, such as micro casting and soft lithography. Thus, designing and fabricating micro structures at personal office immediately become possible with FFSL. Furthermore, we demonstrated that multi-scale micro structures can be easily fabricated by double exposure with FFSL. Skin textures is used as another case to demonstrate that FFSL can fabricate structures with different depth in a single exposure. As a result, FF shows a promising future in biology, and analytical chemistry, such as rapid fabrication of point of care diagnostics and microfluidic analytical devices with low cost. PMID:26314247

Dynamics of poroelastic foams

NASA Astrophysics Data System (ADS)

Forterre, Yoel; Sobac, Benjamin

2010-11-01

Soft poroelastic structures are widespread in biological tissues such as cartilaginous joints in bones, blood-filled placentae or plant organs. Here we investigate the dynamics of open elastic foams immersed in viscous fluids, as model soft poroelastic materials. The experiment consists in slowly compacting blocs of polyurethane solid foam embedded in silicon oil-tanks and studying their relaxation to equilibrium when the confining stress is suddenly released. Measurements of the local fluid pressure and foam velocity field are compared with a simple two-phase flow approach. For small initial compactions, the results show quantitative agreement with the classical diffusion theory of soil consolidation (Terzaghi, Biot). On the other hand, for large initial compactions, the dynamics exhibits long relaxation times and decompaction fronts, which are mainly controlled by the highly non-linear mechanical response of the foam. The analogy between this process and the evaporation of a polymer melt close to the glass transition will be briefly discussed.

Structure changes in metastable and unstable foams probed by multispeckle diffusing light spectroscopy

NASA Astrophysics Data System (ADS)

Yuvchenko, S. A.; Tzyipin, D. V.; Isaeva, A. A.; Isaeva, E. A.; Ushakova, O. V.; Macheev, M. S.; Zimnyakov, D. A.

2018-04-01

The temporal evolution of the metastable and unstable foams had been studied. Diffusion wave spectroscopy was chosen as the diagnostic method, with calculation of the correlation time of the fluctuations in the intensity of the probing radiation. It was established that the correlation time increases with the time according to the power law with different parameters, depending on the type of the evolution and was found to be equal to 0.5 for the case of the metastable and to 2,52 for the unstable foam. It was also determined that the behaviour of the correlation time agrees well with the evolution of the characteristic dimensions of the scatterers in the form of bubbles in the medium, which can be used for contactless monitoring of the foaming processes in the production of the foam-like materials for various applications, for example, in the synthesis of the biocompatible polymer matrices - scaffolds.

Method of making foam-encapsulated laser targets

DOEpatents

Rinde, James A.; Fulton, Fred J.

1977-01-01

Foam-encapsulated laser fusion targets are fabricated by suspending fusion fuel filled shells in a solution of cellulose acetate, extruding the suspension through a small orifice into a bath of ice water, soaking the thus formed shell containing cellulose acetate gel in the water to extract impurities, freezing the gel, and thereafter freeze-drying wherein water and solvents sublime and the gel structure solidifies into a low-density microcellular foam containing one or more encapsulated fuel-filled shells. The thus formed material is thereafter cut and mounted on a support to provide laser fusion targets containing a fuel-filled shell surrounded by foam having a thickness of 10 to 60 .mu.m, a cell size of less than 2 .mu.m, and density of 0.08 to 0.6.times.10.sup.3 kg/m.sup.3. Various configured foam-encapsulated targets capable of being made by the encapsulation method are illustrated.

Effect of silica nanoparticles on polyurethane foaming process and foam properties

NASA Astrophysics Data System (ADS)

Francés, A. B.; Navarro Bañón, M. V.

2014-08-01

Flexible polyurethane foams (FPUF) are commonly used as cushioning material in upholstered products made on several industrial sectors: furniture, automotive seating, bedding, etc. Polyurethane is a high molecular weight polymer based on the reaction between a hydroxyl group (polyol) and isocyanate. The density, flowability, compressive, tensile or shearing strength, the thermal and dimensional stability, combustibility, and other properties can be adjusted by the addition of several additives. Nanomaterials offer a wide range of possibilities to obtain nanocomposites with specific properties. The combination of FPUF with silica nanoparticles could develop nanocomposite materials with unique properties: improved mechanical and thermal properties, gas permeability, and fire retardancy. However, as silica particles are at least partially surface-terminated with Si-OH groups, it was suspected that the silica could interfere in the reaction of poyurethane formation.The objective of this study was to investigate the enhancement of thermal and mechanical properties of FPUF by the incorporation of different types of silica and determining the influence thereof during the foaming process. Flexible polyurethane foams with different loading mass fraction of silica nanoparticles (0-1% wt) and different types of silica (non treated and modified silica) were synthesized. PU/SiO2 nanocomposites were characterized by FTIR spectroscopy, TGA, and measurements of apparent density, resilience and determination of compression set. Addition of silica nanoparticles influences negatively in the density and compression set of the foams. However, resilience and thermal stability of the foams are improved. Silica nanoparticles do not affect to the chemical structure of the foams although they interfere in the blowing reaction.

Flexible Foam Protection Materials for Constellation Space Suit Element Portable Life Support Subsystem Packaging Study

NASA Technical Reports Server (NTRS)

Tang, Henry H.; Orndoff, Evelyne S.; Thomas, Gretchen A.

2009-01-01

This paper discusses the effort in evaluating and selecting a light weight impact protection material for the Constellation Space Suit Element (CSSE) Portable Life Support Subsystem (PLSS) conceptual packaging study. A light weight material capable of holding and protecting the components inside the PLSS is required to demonstrate the viability of the flexible PLSS packaging concept. The material needs to distribute, dissipate, and absorb the impact energy of the PLSS falling on the lunar surface. It must also be very robust and function in the extreme lunar thermal vacuum environment for up to one hundred Extravehicular Activity (EVA) missions. This paper documents the performance requirements for selecting a foam protection material, and the methodologies for evaluating commercial off-the-shelf (COTS) foam protection materials. It also presents the materials properties test results and impact drop test results of the various foam materials evaluated in the study. The findings from this study suggest that a foam based flexible protection system is a viable solution for PLSS packaging. However, additional works are needed to optimize COTS foam properties or to develop a composite foam system that will meet all the performance requirements for the CSSE PLSS flexible packaging.

Characterization of Space Shuttle Thermal Protection System (TPS) Materials for Return-to-Flight following the Shuttle Columbia Accident Investigation

NASA Technical Reports Server (NTRS)

Wingard, Doug

2006-01-01

During the Space Shuttle Columbia Accident Investigation, it was determined that a large chunk of polyurethane insulating foam (= 1.67 lbs) on the External Tank (ET) came loose during Columbia's ascent on 2-1-03. The foam piece struck some of the protective Reinforced Carbon-Carbon (RCC) panels on the leading edge of Columbia's left wing in the mid-wing area. This impact damaged Columbia to the extent that upon re-entry to Earth, superheGed air approaching 3,000 F caused the vehicle to break up, killing all seven astronauts on board. A paper after the Columbia Accident Investigation highlighted thermal analysis testing performed on External Tank TPS materials (1). These materials included BX-250 (now BX-265) rigid polyurethane foam and SLA-561 Super Lightweight Ablator (highly-filled silicone rubber). The large chunk of foam from Columbia originated fiom the left bipod ramp of the ET. The foam in this ramp area was hand-sprayed over the SLA material and various fittings, allowed to dry, and manually shaved into a ramp shape. In Return-to-Flight (RTF) efforts following Columbia, the decision was made to remove the foam in the bipod ramp areas. During RTF efforts, further thermal analysis testing was performed on BX-265 foam by DSC and DMA. Flat panels of foam about 2-in. thick were sprayed on ET tank material (aluminum alloys). The DSC testing showed that foam material very close to the metal substrate cured more slowly than bulk foam material. All of the foam used on the ET is considered fully cured about 21 days after it is sprayed. The RTF culminated in the successful launch of Space Shuttle Discovery on 7-26-05. Although the flight was a success, there was another serious incident of foam loss fiom the ET during Shuttle ascent. This time, a rather large chunk of BX-265 foam (= 0.9 lbs) came loose from the liquid hydrogen (LH2) PAL ramp, although the foam did not strike the Shuttle Orbiter containing the crew. DMA testing was performed on foam samples taken fiom a simulated PAL ramp panel. It was found that the smooth rind on the foam facing the cable tray did significantly affect the properties of foam at the PAL ramp surface. The smooth rind increased the storage modulus E' of the foam as much as 20- 40% over a temperature range of -145 to 95 C. Because of foam loss fiom the PAL ramp, future Shuttle flights were grounded indefinitely to allow further testing to better understand foam properties. The decision was also made to remove foam from the LH2 PAL, ramp. Other RTF efforts prior to the launch of Discovery included

Evaluation of Canisterized Foams and Evaluation of Radiation Hardened Foams for D&D Activities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nicholson, J. C.

The introduction of polyurethane foams has previously been examined elsewhere within the DOE complex with regards to decontamination and decommissioning (D&D) activities, though its use has been prohibited as a result of excessive heat generation and flammability concerns per the safety basis. Should these foams be found compatible with respect to the facility safety basis requirements, D&D work involving large void containing structures such as gloveboxes could be eased through the fixation of residual contamination after decontamination efforts have concluded. To this end, SRNL embarked on a characterization of commercial epoxy foams to identify the characteristics that would be mostmore » important to safety basis requirements. Through SRNL’s efforts, the performance of commercial two-part epoxy foams was evaluated for their foaming characteristics, temperature profiles, loading capability with high-Z (high density) additives, and applicability for shielding gamma emission from isotopes including; Am-241, Cs-137, and Co-60. It was found that these foams are capable of encapsulation of a desired volume, though the ideal and experimental expansion coefficients were found to differ. While heat is generated during the reaction, no samples generated heat above 70 °C. Of the down–selected materials, heating was on the order of 40 °C for the flexible foam and 60 °C for the rigid foam. Both were found to return to room temperature after 20 minutes regardless of the volume of foam cast. It was also found that the direct introduction of high-Z additives were capable of attenuating 98% of Am-241 gamma signal, 16% of Cs-137 signal, and 9.5% of Co-60 signal at 1:1 loading capacities of total liquid constituent weight to additive weight. These efforts are currently being reviewed for the ASTM January 2017 subcommittee discussions to address the lack of test methods and standards regarding these materials with respect to D&D environments.« less

Ultra low density biodegradable shape memory polymer foams with tunable physical properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Singhal, Pooja; Wilson, Thomas S.; Cosgriff-Hernandez, Elizabeth

Compositions and/or structures of degradable shape memory polymers (SMPs) ranging in form from neat/unfoamed to ultra low density materials of down to 0.005 g/cc density. These materials show controllable degradation rate, actuation temperature and breadth of transitions along with high modulus and excellent shape memory behavior. A method of m ly low density foams (up to 0.005 g/cc) via use of combined chemical and physical aking extreme blowing agents, where the physical blowing agents may be a single compound or mixtures of two or more compounds, and other related methods, including of using multiple co-blowing agents of successively higher boilingmore » points in order to achieve a large range of densities for a fixed net chemical composition. Methods of optimization of the physical properties of the foams such as porosity, cell size and distribution, cell openness etc. of these materials, to further expand their uses and improve their performance.« less

Corrosion Behavior of Magnesium Based Foam Structure in Hank’s Solution

NASA Astrophysics Data System (ADS)

Franciska, P. L.; Erryani, A.; Annur, D.; Kartika, I.

2017-05-01

Metal foam is a new class of materials with promising applications and a unique combination of physical, chemical, and mechanical properties. The purpose of biodegradable implants is to support tissue regeneration and healing in a particular application by material degradation and implant replacement through the surrounding tissue. Magnesium alloys are expected to be degraded in the body and its corrosion products not deleterious to the surrounding tissue. In the present study, the foam metal was manufactured via powder metallurgy with a different variation of sintering temperature and TiH2 used as a foaming agent which are added to Mg-1Ca-3Zn alloy as much 3% wt TiH2. The sintering temperatures were 500, 550 and 600 °C with a constant holding time of 5 hours. It’s critical that the sintering temperature is carefully selected in consideration of their corrosion behavior. This paper reports the study of the behavior of the Mg-Ca-Zn alloy metal foam which evaluated by SEM, EDX, and electrochemical corrosion test in Hank’s solutions. After exposure, the SEM result of Mg-Ca-Zn-3TiH2 to Hank’s solution, a volcano-like structure is formed. The streams of H2 bubbles form at local sites on the Mg alloy surface where electrochemical reactions are taking place, leading to the particular structure with around shape and often with a hole in the center. The corresponding EDS result maps reveal enrichment of O, Ca, P and Mg as corrosion product. Potentiodynamic polarization experiments conducted at 37 °C and pH 7.4 indicated the increased biodegradation rates resulted from porous structure of foam samples. Corrosion rate in 500oC sintering temperature were 1.99 millimiles per year (mmpy) with corrosion current density (I corr ) 87.3.10-6 A/cm2, corrosion rate in 550 °C sintering temperature were 2,16 mmpy with I corr 94.4.10-6 A/cm2 and rate in 600 °C sintering temperature were 2.41 mmpy with I corr 105.10-6 A/cm2. The results showed that the increasing of sintering temperature could influence the corrosion resistance of Mg alloy.

The Effects of Foam Thermal Protection System on the Damage Tolerance Characteristics of Composite Sandwich Structures for Launch Vehicles

NASA Technical Reports Server (NTRS)

Nettles, A. T.; Hodge, A. J.; Jackson, J. R.

2011-01-01

For any structure composed of laminated composite materials, impact damage is one of the greatest risks and therefore most widely tested responses. Typically, impact damage testing and analysis assumes that a solid object comes into contact with the bare surface of the laminate (the outer ply). However, most launch vehicle structures will have a thermal protection system (TPS) covering the structure for the majority of its life. Thus, the impact response of the material with the TPS covering is the impact scenario of interest. In this study, laminates representative of the composite interstage structure for the Ares I launch vehicle were impact tested with and without the planned TPS covering, which consists of polyurethane foam. Response variables examined include maximum load of impact, damage size as detected by nondestructive evaluation techniques, and damage morphology and compression after impact strength. Results show that there is little difference between TPS covered and bare specimens, except the residual strength data is higher for TPS covered specimens.

Shockwave dynamics: a comparison between stochastic and periodic porous architectures

NASA Astrophysics Data System (ADS)

Branch, Brittany; Ionite, Axinte; Clements, Bradford; Montgomery, David; Schmalzer, Andrew; Patterson, Brian; Mueller, Alexander; Jensen, Brian; Dattelbaum, Dana

Polymeric foams are used extensively as structural supports and load mitigating materials in which they are subjected to compressive loading at a range of strain rates, up to the high strain rates encountered in blast and shockwave loading. To date, there have been few insights into compaction phenomena in porous structures at the mesoscale, and the influence of structure on shockwave localization. Of particular interest is when the properties of the inherent mesoscopic, periodic structure begin to emerge, versus the discrete behavior of the individual cell. Here, we illustrate, for the first time, modulation of shockwave dynamics controlled at micron-length scales in additively manufactured periodic porous structures measured using in situ, time-resolved x-ray phase contrast imaging at the Advanced Photon Source. Further, we demonstrate how the shockwave dynamics in periodic structures differ from stochastic foams of similar density and we conclude that microstructural control in elastomer foams has a dramatic effect on shockwave dynamics and can be tailored towards a variety of applications. Laboratory Directed Research and Development (LDRD) program at Los Alamos National Laboratory (project# 20160103DR) and DOE/NNSA Campaign 2.

46 CFR 164.015-3 - Material and workmanship.

Code of Federal Regulations, 2010 CFR

2010-10-01

...: SPECIFICATIONS AND APPROVAL MATERIALS Plastic Foam, Unicellular, Buoyant, Sheet and Molded Shape § 164.015-3 Material and workmanship. (a) The unicellular plastic foam shall be all new material complying with the... values within the limits shown in Table 164.015-4(a). (b) The unicellular plastic foam shall be produced...

46 CFR 164.015-3 - Material and workmanship.

Code of Federal Regulations, 2014 CFR

2014-10-01

...: SPECIFICATIONS AND APPROVAL MATERIALS Plastic Foam, Unicellular, Buoyant, Sheet and Molded Shape § 164.015-3 Material and workmanship. (a) The unicellular plastic foam shall be all new material complying with the... values within the limits shown in Table 164.015-4(a). (b) The unicellular plastic foam shall be produced...

Fire-resistant materials for aircraft passenger seat construction

NASA Technical Reports Server (NTRS)

Fewell, L. L.; Tesoro, G. C.; Moussa, A.; Kourtides, D. A.

1979-01-01

The thermal response characteristics of fabric and fabric-foam assemblies are described. The various aspects of the ignition behavior of contemporary aircraft passenger seat upholstery fabric materials relative to fabric materials made from thermally stable polymers are evaluated. The role of the polymeric foam backing on the thermal response of the fabric-foam assembly is also ascertained. The optimum utilization of improved fire-resistant fabric and foam materials in the construction of aircraft passenger seats is suggested.

Dynamic Finite Element Predictions for Mars Sample Return Cellular Impact Test #4

NASA Technical Reports Server (NTRS)

Fasanella, Edwin L.; Billings, Marcus D.

2001-01-01

The nonlinear finite element program MSC.Dytran was used to predict the impact pulse for (he drop test of an energy absorbing cellular structure. This pre-test simulation was performed to aid in the design of an energy absorbing concept for a highly reliable passive Earth Entry Vehicle (EEV) that will directly impact the Earth without a parachute. In addition, a goal of the simulation was to bound the acceleration pulse produced and delivered to the simulated space cargo container. EEV's are designed to return materials from asteroids, comets, or planets for laboratory analysis on Earth. The EEV concept uses an energy absorbing cellular structure designed to contain and limit the acceleration of space exploration samples during Earth impact. The spherical shaped cellular structure is composed of solid hexagonal and pentagonal foam-filled cells with hybrid graphite-epoxy/Kevlar cell walls. Space samples fit inside a smaller sphere at the enter of the EEV's cellular structure. The material models and failure criteria were varied to determine their effect on the resulting acceleration pulse. Pre-test analytical predictions using MSC.Dytran were compared with the test results obtained from impact test #4 using bungee accelerator located at the NASA Langley Research Center Impact Dynamics Research Facility. The material model used to represent the foam and the proper failure criteria for the cell walls were critical in predicting the impact loads of the cellular structure. It was determined that a FOAMI model for the foam and a 20% failure strain criteria for the cell walls gave an accurate prediction of the acceleration pulse for drop test #4.

Low density microcellular carbon or catalytically impregnated carbon foams and process for their prepartion

DOEpatents

Hopper, Robert W.; Pekala, Richard W.

1988-01-01

Machinable and structurally stable, low density microcellular carbon, and catalytically impregnated carbon, foams, and process for their preparation, are provided. Pulverized sodium chloride is classified to improve particle size uniformity, and the classified particles may be further mixed with a catalyst material. The particles are cold pressed into a compact having internal pores, and then sintered. The sintered compact is immersed and then submerged in a phenolic polymer solution to uniformly fill the pores of the compact with phenolic polymer. The compact is then heated to pyrolyze the phenolic polymer into carbon in the form of a foam. Then the sodium chloride of the compact is leached away with water, and the remaining product is freeze dried to provide the carbon, or catalytically impregnated carbon, foam.

Low density microcellular carbon or catalytically impregnated carbon foams and process for their preparation

DOEpatents

Hooper, R.W.; Pekala, R.W.

1987-04-30

Machinable and structurally stable, low density microcellular carbon, and catalytically impregnated carbon, foams, and process for their preparation, are provided. Pulverized sodium chloride is classified to improve particle size uniformity, and the classified particles may be further mixed with a catalyst material. The particles are cold pressed into a compact having internal pores, and then sintered. The sintered compact is immersed and then submerged in a phenolic polymer solution to uniformly fill the pores of the compact with phenolic polymer. The compact is then heated to pyrolyze the phenolic polymer into carbon in the form of a foam. Then the sodium chloride of the compact is leached away with water, and the remaining product is freeze dried to provide the carbon, or catalytically impregnated carbon, foam.

Dynamic characterization of frequency response of shock mitigation of a polymethylene diisocyanate (PMDI) based rigid polyurethane foam

DOE PAGES

Song, Bo; Nelson, Kevin

2015-09-01

Kolsky compression bar experiments were conducted to characterize the shock mitigation response of a polymethylene diisocyanate (PMDI) based rigid polyurethane foam, abbreviated as PMDI foam in this study. The Kolsky bar experimental data was analyzed in the frequency domain with respect to impact energy dissipation and acceleration attenuation to perform a shock mitigation assessment on the foam material. The PMDI foam material exhibits excellent performance in both energy dissipation and acceleration attenuation, particularly for the impact frequency content over 1.5 kHz. This frequency (1.5 kHz) was observed to be independent of specimen thickness and impact speed, which may represent themore » characteristic shock mitigation frequency of the PMDI foam material under investigation. The shock mitigation characteristics of the PMDI foam material were insignificantly influenced by the specimen thickness. As a result, impact speed did have some effect.« less

Dynamic characterization of frequency response of shock mitigation of a polymethylene diisocyanate (PMDI) based rigid polyurethane foam

DOE Office of Scientific and Technical Information (OSTI.GOV)

Song, Bo; Nelson, Kevin

Kolsky compression bar experiments were conducted to characterize the shock mitigation response of a polymethylene diisocyanate (PMDI) based rigid polyurethane foam, abbreviated as PMDI foam in this study. The Kolsky bar experimental data was analyzed in the frequency domain with respect to impact energy dissipation and acceleration attenuation to perform a shock mitigation assessment on the foam material. The PMDI foam material exhibits excellent performance in both energy dissipation and acceleration attenuation, particularly for the impact frequency content over 1.5 kHz. This frequency (1.5 kHz) was observed to be independent of specimen thickness and impact speed, which may represent themore » characteristic shock mitigation frequency of the PMDI foam material under investigation. The shock mitigation characteristics of the PMDI foam material were insignificantly influenced by the specimen thickness. As a result, impact speed did have some effect.« less

Multi-Functional Sandwich Composites for Spacecraft Applications: An Initial Assessment

NASA Technical Reports Server (NTRS)

Adams, Daniel O.; Webb, Nicholas Jason; Yarger, Cody B.; Hunter, Abigail; Oborn, Kelli D.

2007-01-01

Current spacecraft implement relatively uncoupled material and structural systems to address a variety of design requirements, including structural integrity, damage tolerance, radiation protection, debris shielding and thermal insulation. This investigation provided an initial assessment of multi-functional sandwich composites to integrate these diverse requirements. The need for radiation shielding was addressed through the selection of polymeric constituents with high hydrogen content. To provide increased damage tolerance and debris shielding, manufacturing techniques were developed to incorporate transverse stitching reinforcement, internal layers, and a self-healing ionomer membrane. To assess the effects of a space environment, thermal expansion behavior of the candidate foam materials was investigated under a vacuum and increasing temperature. Finally, a thermal expansion model was developed for foam under vacuum conditions and its predictive capability assessed.

Degradable and porous Fe-Mn-C alloy for biomaterials candidate

NASA Astrophysics Data System (ADS)

Pratesa, Yudha; Harjanto, Sri; Larasati, Almira; Suharno, Bambang; Ariati, Myrna

2018-02-01

Nowadays, degradable implants attract attention to be developed because it can improve the quality of life of patients. The degradable implant is expected to degrade easily in the body until the bone healing process already achieved. However, there is limited material that could be used as a degradable implant, polymer, magnesium, and iron. In the previous study, Fe-Mn-C alloys had succesfully produced austenitic phase. However, the weakness of the alloy is degradation rate of materials was considered below the expectation. This study aimed to produce porous Fe-Mn-C materials to improve degradation rate and reduce the density of alloy without losing it non-magnetic properties. Potassium carbonate (K2CO3) were chosen as filler material to produce foam structure by sintering and dissolution process. Multisteps sintering process under argon gas environment was performed to generate austenite phase. The product showed an increment of the degradation rate of the foamed Fe-Mn-C alloy compared with the solid Fe-Mn-C alloy without losing the Austenitic Structure

Rigid polyurethane foam as an efficient material for shock wave attenuation

NASA Astrophysics Data System (ADS)

Komissarov, P. V.; Borisov, A. A.; Sokolov, G. N.; Lavrov, V. V.

2016-09-01

A new method for reducing parameters of blast waves generated by explosions of HE charges on ground is presented. Most of the traditional techniques reduce the wave parameters at a certain distance from the charge, i.e. as a matter of fact the damping device interacts with a completely formed shock wave. The proposed approach is to use rigid polyurethane foam coating immediately the explosive charge. A distributed structure of such a foam block that provides most efficient shock wave attenuation is suggested. Results of experimental shock wave investigations recorded in tests in which HE charges have been exploded with damping devices and without it are compared.

Biocompatible evaluation of barium titanate foamed ceramic structures for orthopedic applications.

PubMed

Ball, Jordan P; Mound, Brittnee A; Nino, Juan C; Allen, Josephine B

2014-07-01

The potential of barium titanate (BT) to be electrically active makes it a material of interest in regenerative medicine. To enhance the understanding of this material for orthopedic applications, the in vitro biocompatibility of porous BT fabricated using a direct foaming technique was investigated. Characterization of the resultant foams yielded an overall porosity between 50 and 70% with average pore size in excess of 30 µm in diameter. A mouse osteoblast (7F2) cell line was cultured with the BT to determine the extent of the foams' toxicity using a LDH assay. After 72 h, BT foams showed a comparable cytotoxicity of 6.4 ± 0.8% to the 8.4 ± 1.5% of porous 45S5 Bioglass®. The in vitro inflammatory response elicited from porous BT was measured as a function of tumor necrosis factor alpha (TNF-α) secreted from a human monocytic leukemia cell line (THP-1). Results indicate that the BT foams do not cause a significant inflammatory response, eliciting a 9.4 ± 1.3 pg of TNF-α per mL of media compared with 20.2 ± 2.3 pg/mL from untreated cells. These results indicate that porous BT does not exhibit short term cytotoxicity and has potential for orthopedic tissue engineering applications. © 2013 Wiley Periodicals, Inc.

Preparation of amine-impregnated silica foams using agar as the gelling agent

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jardim, Iara M., E-mail: iaramj01@yahoo.com.br

In this work we successfully prepared amine-impregnated gel-cast silica foams using agar and atmospheric air as the gelling agent and heat treatment atmosphere, respectively. The concentration of 3,6-anhydrogalactose in agar was evaluated by ultraviolet–visible spectroscopy (UV–Vis). The obtained foams were examined by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TG) coupled to mass spectrometry (TG-MS), scanning electron microscopy (SEM), X-ray microtomography (micro-CT), and Archimedes method. The cold crushing strength of the materials prepared in this work was assessed using a mechanical testing stage available in the micro-CT system. The obtained foams exhibited a highly interconnected pore network, with an expressivemore » presence of open pores. Samples heat-treated at 1300 °C for 2 h showed both an expressive porosity (≈ 77%) and a significant cold crushing strength (≈ 1.4 MPa). It was observed that the calcination of the prepared materials at 1200 °C for times as long as 16 h may lead to the rupture of pore walls. FTIR and TG-MS revealed that amine groups were properly incorporated into the foams structure. - Highlights: •Successful preparation of amine-impregnated gel-cast silica foams •Agar used as the gelling agent •Samples with expressive porosity and cold crushing strength •Sintering times as long as 16 h led to the rupture of the pore network.« less

[Phenolic foam prepared by lignin from a steam-explosion derived biorefinery of corn stalk].

PubMed

Wang, Guanhua; Chen, Hongzhang

2014-06-01

To increase the integral economic effectiveness, biorefineries of lignocellulosic materials should not only utilize carbohydrates hydrolyzed from cellulose and hemicellulose but also use lignin. We used steam-exploded corn stalk as raw materials and optimized the temperature and alkali concentration in the lignin extraction process to obtain lignin liquor with higher yield and purity. Then the concentrated lignin liquor was used directly to substitute phenol for phenolic foam preparation and the performances of phenolic foam were characterized by microscopic structure analysis, FTIR, compression strength and thermal conductivity detection. The results indicated that, when steam-exploded corn stalk was extracted at 120 degrees C for 2 h by 1% NaOH with a solid to liquid ratio of 1:10, the extraction yield of lignin was 79.67%. The phenolic foam prepared from the concentrated lignin liquor showed higher apparent density and compression strength with the increasing substitution rate of lignin liquor. However, there were not significant differences of thermal conductivity and flame retardant properties by the addition of lignin, which meant that the phenolic foam substituted by lignin liquor was approved for commercial application. This study, which uses alkali-extracted lignin liquor directly for phenolic foam preparation, provides a relatively simple way for utilization of lignin and finally increases the overall commercial operability ofa lignocellulosic biorefinery derived by steam explosion.

Foam composition for treating asbestos-containing materials and method of using same

DOE Office of Scientific and Technical Information (OSTI.GOV)

Block, J.; Krupkin, N.V.; Kuespert, D.R.

A composition for transforming a chrysotile asbestos-containing material into a non-asbestos material is disclosed. The composition comprises water, at least about 30% by weight of an acid component, at least about 0.1% by weight of a source of fluoride ions, and a stable foam forming amount of a foaming agent system having both cationic and non-ionic functionality. A method of transforming the asbestos-containing material into a non-asbestos material using the present composition in the form of a foam also disclosed.

Foam composition for treating asbestos-containing materials and method of using same

DOEpatents

Block, Jacob; Krupkin, Natalia Vera; Kuespert, Daniel Reid; Nishioka, Gary Masaru; Lau, John Wing-Keung; Palmer, Nigel Innes

1998-04-28

A composition for transforming a chrysotile asbestos-containing material into a non-asbestos material is disclosed, wherein the composition comprises water, at least about 30% by weight of an acid component, at least about 0.1% by weight of a source of fluoride ions, and a stable foam forming amount of a foaming agent system having both cationic and non-ionic functionality. A method of transforming the asbestos-containing material into a non-asbestos material using the present composition in the form of a foam also disclosed.

Foam composition for treating asbestos-containing materials and method of using same

DOEpatents

Block, J.; Krupkin, N.V.; Kuespert, D.R.; Nishioka, G.M.; Lau, J.W.K.; Palmer, N.I.

1998-04-28

A composition for transforming a chrysotile asbestos-containing material into a non-asbestos material is disclosed. The composition comprises water, at least about 30% by weight of an acid component, at least about 0.1% by weight of a source of fluoride ions, and a stable foam forming amount of a foaming agent system having both cationic and non-ionic functionality. A method of transforming the asbestos-containing material into a non-asbestos material using the present composition in the form of a foam also disclosed.

A New Light Weight Structural Material for Nuclear Structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rabiei, Afsaneh

2016-01-14

Radiation shielding materials are commonly used in nuclear facilities to attenuate the background ionization radiations to a minimum level for creating a safer workplace, meeting regulatory requirements and maintaining high quality performance. The conventional radiation shielding materials have a number of drawbacks: heavy concrete contains a high amount of elements that are not desirable for an effective shielding such as oxygen, silicon, and calcium; a well known limitation of lead is its low machinability and toxicity, which is causing a major environmental concern. Therefore, an effective and environmentally friendly shielding material with increased attenuation and low mass density is desirable.more » Close-cell composite metal foams (CMFs) and open-cell Al foam with fillers are light-weight candidate materials that we have studied in this project. Close-cell CMFs possess several suitable properties that are unattainable by conventional radiation shielding materials such as low density and high strength for structural applications, high surface area to volume ratio for excellent thermal isolation with an extraordinary energy absorption capability. Open-cell foam is made up of a network of interconnected solid struts, which allows gas or fluid media to pass through it. This unique structure provided a further motive to investigate its application as radiation shields by infiltrating original empty pores with high hydrogen or boron compounds, which are well known for their excellent neutron shielding capability. The resulting open-cell foam with fillers will not only exhibit light weight and high specific surface area, but also possess excellent radiation shielding capability and good processability. In this study, all the foams were investigated for their radiation shielding efficiency in terms of X-ray, gamma ray and neutron. X-ray transmission measurements were carried out on a high-resolution microcomputed tomography (microCT) system. Gamma-emitting sources: 3.0mCi 60Co, 1.8mCi 137Cs, 13.5mCi 241Am, and 5.0mCi 133Ba were used for gamma-ray attenuation analysis. The evaluations of neutron transmission measurements were conducted at the Neutron Powder Diffractometer beam facility at North Carolina State University. The experimental results were verified theoretically through XCOM and Monte Carlo Z-particle Transport Code (MCNP). A mechanical investigation was performed by means of quasi-static compressive testing. Thermal characterizations were carried out through effective thermal conductivity and thermal expansion analyses in terms of high temperature guarded-comparative-longitudinal heat flow technique and thermomechanical analyzer (TMA), respectively. The experimental results were compared with analytical results obtained from, respectively, Brailsford and Major’s model and modified Turner’s model for verification. Flame test was performed in accordance with United States Nuclear Regulatory Commission (USNRC) standard. CMF sample and a 304L stainless steel control sample were subjected to a fully engulfing fire with an average flame temperature of 800°C for a period of 30 minutes. Finite Element Analysis was conducted to secure the credibility of the experimental results. This research indicates the potential of utilizing the light-weight close-cell CMFs and open-cell Al foam with fillers as shielding material replacing current heavy structures with additional advantage of high-energy absorption and excellent thermal characteristics.« less

Composite panels based on woven sandwich-fabric preforms

NASA Astrophysics Data System (ADS)

van Vuure, Aart Willem

A new type of sandwich material was investigated, based on woven sandwich-fabric preforms. Because of the integrally woven nature of the sandwich-fabric the skin-core debonding resistance of panels and structures based on the preform is very high. As the sandwich-fabrics are produced by a large scale textile weaving process (velvet weaving or distance weaving) and already a preform of a sandwich is available, the cost of the final panel or structure can potentially stay limited. Most attention in this work is focussed on the mechanical performance of sandwich-fabric panels. The high skin-core debonding resistance was verified and also indications were found of a good damage tolerance. Both unfoamed and foamed panels were evaluated and compared with existing sandwich panels. Microstructural parameters investigated for unfoamed cores are pile length, pile density, woven pile angles, degree of pile stretching, tilt angles of the piles induced during panel production and resin content and distribution. For foamed panels it is especially the foam density which has an important influence. There appears to be a synergistic effect between piles and foam in the sandwich core, leading to very acceptable mechanical properties. For panels for (semi) structural applications, foaming is almost indispensable once the panel thickness is higher than about 15 mm. To understand the behaviour of foamed panels, attention was paid to the modelling of the mechanics of pure foam. The foam microstructure was modelled with the model of an anisotropic tetrakaidecahedron. The mechanical properties of unfoamed panels were modelled with the help of finite elements. A detailed geometrical description of the core layout was made which was incorporated into a preprocessing program for a finite element code. Attention is paid to the production of panels based on the woven preforms. A newly developed Adhesive Foil Stretching process was investigated. Also the foaming of panels was studied. A lot of attention was paid to a special application in the field of structural damping, where sandwich-fabric panels could be used as spacer in a constrained layer application. The vibrations and damping were modelled with the help of finite elements.

Flexible Foam Protection Materials for Portable Life Support System Packaging Study

NASA Technical Reports Server (NTRS)

Tang,Henry H.; Dillon, Paul A.; Thomas, Gretchen A.

2009-01-01

This paper discusses the phase I effort in evaluating and selecting a light weight impact protection material for the Constellation Space Suit Element (CSSE) Portable Life Support System (PLSS) conceptual packaging study. A light weight material capable of holding and protecting the components inside the PLSS is required to demonstrate the viability of the flexible PLSS packaging concept. The material needs to distribute, dissipate, and absorb the impact energy of the PLSS falling on the lunar surface. It must also be robust to consistently perform over several Extravehicular Activity (EVA) missions in the extreme lunar thermal vacuum environment. This paper documents the performance requirements for selecting a foam protection material, and the methodologies for evaluating some commercial off-the-shelf (COTS) foam material candidates. It also presents the mechanical properties and impact drop tests results of the foam material candidates. The results of this study suggest that a foam based flexible protection system is a viable solution for PLSS packaging. However, additional works are needed to optimize COTS foam or to develop a composite foam system that will meet all the performance requirements for the CSSE PLSS flexible packaging.

Foam-mat drying technology: A review.

PubMed

Hardy, Z; Jideani, V A

2017-08-13

This article reviews various aspects of foam-mat drying such as foam-mat drying processing technique, main additives used for foam-mat drying, foam-mat drying of liquid and solid foods, quality characteristics of foam-mat dried foods, and economic and technical benefits for employing foam-mat drying. Foam-mat drying process is an alternative method that allows the removal of water from liquid materials and pureed materials. In this drying process, a liquid material is converted into foam that is stable by being whipped after adding an edible foaming agent. The stable foam is then spread out in sheet or mat and dried by using hot air (40-90°C) at atmospheric pressure. Methyl cellulose (0.25-2%), egg white (3-20%), maltodextrin (0.5-05%), and gum Arabic (2-9%) are the commonly utilized additives for the foam-mat drying process at the given range, either combined together for their effectiveness or individual effect. The foam-mat drying process is suitable for heat sensitive, viscous, and sticky products that cannot be dried using other forms of drying methods such as spray drying because of the state of product. More interest has developed for foam-mat drying because of the simplicity, cost effectiveness, high speed drying, and improved product quality it provides.

The design and modeling of periodic materials with novel properties

NASA Astrophysics Data System (ADS)

Berger, Jonathan Bernard

Cellular materials are ubiquitous in our world being found in natural and engineered systems as structural materials, sound and energy absorbers, heat insulators and more. Stochastic foams made of polymers, metals and even ceramics find wide use due to their novel properties when compared to monolithic materials. Properties of these so called hybrid materials, those that combine materials or materials and space, are derived from the localization of thermomechanical stresses and strains on the mesoscale as a function of cell topology. The effects of localization can only be generalized in stochastic materials arising from their inherent potential complexity, possessing variations in local chemistry, microstructural inhomogeneity and topological variations. Ordered cellular materials on the other hand, such as lattices and honeycombs, make for much easier study, often requiring analysis of only a single unit-cell. Theoretical bounds predict that hybrid materials have the potential to push design envelopes offering lighter stiffer and stronger materials. Hybrid materials can achieve very low and even negative coefficients of thermal expansion (CTE) while retaining a relatively high stiffness -- properties completely unmatched by monolithic materials. In the first chapter of this thesis a two-dimensional lattice is detailed that possess near maximum stiffness, relative to the tightest theoretical bound, and low, zero and even appreciably negative thermal expansion. Its CTE and stiffness are given in closed form as a function of geometric parameters and the material properties. This result is confirmed with finite elements (FE) and experiment. In the second chapter the compressive stiffness of three-dimensional ordered foams, both closed and open cell, are predicted with FE and the results placed in property space in terms of stiffness and density. A novel structure is identified that effectively achieves theoretical bounds for Young's, shear and bulk modulus simultaneously, over a wide range of relative densities, greatly expanding the property space of available materials with a pragmatic manufacturable structure. A variety of other novel and previously studied ordered foam topologies are also presented that are largely representative of the spectrum of performance of such materials, shedding insight into the behavior of all cellular materials.

Effect of Coversheet Materials on the Acoustic Performance of Melamine Foam

NASA Technical Reports Server (NTRS)

McNelis, Anne M.; Hughes, William O.

2015-01-01

Melamine foam is a highly absorptive material that is often used inside the payload fairing walls of a launch vehicle. This foam reduces the acoustic excitation environment that the spacecraft experiences during launch. Often, the melamine foam is enclosed by thin coversheet materials for contamination protection, thermal protection, and electrostatic discharge control. Previous limited acoustic testing by NASA Glenn Research Center has shown that the presence of a coversheet material on the melamine foam can have a significant impact on the absorption coefficient and the transmission loss. As a result of this preliminary finding a more extensive acoustic test program using several different coversheet materials on melamine foam was performed. Those test results are summarized in this paper. Additionally, a method is provided to use the acoustic absorption and transmission loss data obtained from panel level testing to predict their combined effect for the noise reduction of a launch vehicle payload fairing.

Tuning Interfacial Properties and Processes by Controlling the Rheology and Structure of Poly( N-isopropylacrylamide) Particles at Air/Water Interfaces.

PubMed

Maestro, Armando; Jones, Daniel; Sánchez de Rojas Candela, Carmen; Guzman, Eduardo; Duits, Michel H G; Cicuta, Pietro

2018-06-05

By combining controlled experiments on single interfaces with measurements on solitary bubbles and liquid foams, we show that poly( N-isopropylacrylamide) (PNIPAM) microgels assembled at air/water interfaces exhibit a solid to liquid transition changing the temperature, and that this is associated with the change in the interfacial microstructure of the PNIPAM particles around their volume phase transition temperature. We show that the solid behaves as a soft 2D colloidal glass, and that the existence of this solid/liquid transition offers an ideal platform to tune the permeability of air bubbles covered by PNIPAM and to control macroscopic foam properties such as drainage, stability, and foamability. PNIPAM particles on fluid interfaces allow new tunable materials, for example foam structures with variable mechanical properties upon small temperature changes.

Biofoam II

DOEpatents

Morrison, R.L.

1994-11-01

Biofoam is a rigid, microcellular organic foam made from organic materials derived from natural products and biological organisms. Starting materials include agar, agarose, gelatin, algin, alginates, gellan gum, and microcrystalline cellulose. The organic material is dissolved in a polar solvent, typically water, and the mixture is gelled. The water in the gel pores is replaced at least once with another solvent to reduce the pore size of the final biofoam. The solvent in the gel pores may be replaced several times. After the final replacement of solvent, the gel is frozen and freeze-dried to form a biofoam. Translucent biofoams are formed by selecting a final solvent that forms very small crystals. A variety of crystalline, fibrous, amorphous, or metallic additives may be incorporated into the foam structure to produce lightweight composite materials with enhanced strength and insulating properties. 1 fig.

Biofoam II

DOEpatents

Morrison, Robert L.

1994-01-01

Biofoam is a rigid, microcellular organic foam made from organic materials derived from natural products and biological organisms. Starting materials include agar, agarose, gelatin, algin, alginates, gellan gum, and microcrystalline cellulose. The organic material is dissolved in a polar solvent, typically water, and the mixture is gelled. The water in the gel pores is replaced at least once with another solvent to reduce the pore size of the final biofoam. The solvent in the gel pores may be replaced several times. After the final replacement of solvent, the gel is frozen and freeze-dried to form a biofoam. Translucent biofoams are formed by selecting a final solvent that forms very small crystals. A variety of crystalline, fibrous, amorphous, or metallic additives may be incorporated into the foam structure to produce lightweight composite materials with enhanced strength and insulating properties.

46 CFR 160.049-3 - Materials.

Code of Federal Regulations, 2010 CFR

2010-10-01

...: SPECIFICATIONS AND APPROVAL LIFESAVING EQUIPMENT Specification for a Buoyant Cushion Plastic Foam § 160.049-3... requirements of subpart 164.019. (b) Unicellular plastic foam. The unicellular plastic foam shall be all new material complying with the requirements of Specification subpart 164.015 for Type A or B foam. (c) Cover...

46 CFR 160.049-3 - Materials.

Code of Federal Regulations, 2011 CFR

2011-10-01

...: SPECIFICATIONS AND APPROVAL LIFESAVING EQUIPMENT Specification for a Buoyant Cushion Plastic Foam § 160.049-3... requirements of subpart 164.019. (b) Unicellular plastic foam. The unicellular plastic foam shall be all new material complying with the requirements of Specification subpart 164.015 for Type A or B foam. (c) Cover...

Foam injection molding of poly(lactic acid) with physical blowing agents

NASA Astrophysics Data System (ADS)

Pantani, R.; Sorrentino, A.; Volpe, V.; Titomanlio, G.

2014-05-01

Foam injection molding uses environmental friendly blowing agents under high pressure and temperature to produce parts having a cellular core and a compact solid skin (the so-called "structural foam"). The addition of a supercritical gas reduces the part weight and at the same time improves some physical properties of the material through the promotion of a faster crystallization; it also leads to the reduction of both the viscosity and the glass transition temperature of the polymer melt, which therefore can be injection molded adopting lower temperatures and pressures. These aspects are of extreme interest for biodegradable polymers, which often present a very narrow processing window, with the suitable processing temperatures close to the degradation conditions. In this work, foam injection molding was carried out by an instrumented molding machine, able to measure the pressure evolution in different positions along the flow-path. The material adopted was a biodegradable polymer, namely the Poly(lactic acid), PLA. The effect of a physical blowing agent (PBA) on the viscosity was measured. The density reduction and the morphology of parts obtained by different molding conditions was assessed.

Finite Element Modeling of Deployment, and Foam Rigidization of Struts and Quarter Scale Shooting Star Experiment

NASA Technical Reports Server (NTRS)

Leigh, Larry, Jr.

2002-01-01

Inflated cylindrical struts constructed of kapton polyimide film and rigidized with foam have considerable practical application and potential for use as components of inflatable concentrator assemblies, antenna structures and space power systems, Because of their importance, it is of great interest to characterize the dynamic behavior of these components and structures both experimentally and analytically. It is very helpful to take a building-block approach to modeling and understanding inflatable assemblies by first investigating in detail the behavior of the components such as the struts. The foam material used for rigidization of such cylinders has varying modulus, which is a function of different factors, such as density of the foam. Thus, the primary motivation of the tests and analytical modeling efforts was to determine and understand the response of foam-rigidized cylinders for different densities, sizes, and construction methods, In recent years, inflatable structures have been the subject of renewed interest for space applications such as communications antennae, solar thermal propulsion, and space solar power. A major advantage of using inflatable structures in space is that they are extremely lightweight. This makes inflatables a perfect match for solar thermal propulsion because of the low thrust levels available. An obvious second advantage is on-orbit deployability and subsequent space savings in launch configuration. It can be seen that inflatable cylindrical struts and torus are critical components of structural assemblies. In view of this importance, structural dynamic and static behaviors of typical rigidized polyimide struts are investigated in this paper. The paper will focus on the finite element models that were used to model the behavior of the complete solar collector structure, and the results that they provided, as compared to test data.

[Experimental Study of PMI Foam Composite Properties in Terahertz].

PubMed

Xing, Li-yun; Cui, Hong-liang; Shi, Chang-cheng; Han, Xiao-hui; Zhang, Zi-yin; Li, Wei; Ma, Yu-ting; Zheng, Yan; Zhang, Song-nian

2015-12-01

Polymethacrylimide (PMI) foam composite has many excellent properties. Currently, PMI is heat-resistant foam, with the highest strength and stiffness. It is suitable as a high-performance sandwich structure core material. It can replace the honeycomb structure. It is widely used in aerospace, aviation, military, marine, automotive and high-speed trains, etc. But as new sandwich materials, PMI performance testing in the THz band is not yet visible. Based on the Terahertz (THz) time-domain spectroscopy technique, we conducted the transmission and reflection experiments, got the time domain waveforms and power density spectrum. And then we analyzed and compared the signals. The MATALB and Origin 8. 0 was used to calculate and obtain the transmittance (transfer function), absorptivity Coefficient, reflectance and the refractive index of the different thickness Degussa PMI (Model: Rohacell WF71), which were based on the application of the time-domain and frequency-domain analysis methods. We used the data to compared with the THz refractive index and absorption spectra of a domestic PMI, Baoding Meiwo Technology Development Co. , Ltd. (Model: SP1D80-P-30). The result shows that the impact of humidity on the measurement results is obvious. The refractive index of PMI is about 1. 05. The attenuation of power spectrum is due to the signal of the test platform is weak, the sample is thick and the internal scattering of PMI foam microstructure. This conclusion provides a theoretical basis for the THz band applications in the composite PMI. It also made a good groundwork for THz NDT (Non-Destructive Testing, NDT) technology in terms of PMI foam composites.

Research of hail impact on aircraft wheel door with lattice hybrid structure

NASA Astrophysics Data System (ADS)

Li, Shengze; Jin, Feng; Zhang, Weihua; Meng, Xuanzhu

2016-09-01

Aimed at a long lasting issue of hail impact on aircraft structures and aviation safety due to its high speed, the resistance performance of hail impact on the wheel door of aircraft with lattice hybrid structure is investigated. The proper anti-hail structure can be designed both efficiency and precision based on this work. The dynamic responses of 8 different sandwich plates in diverse impact speed are measured. Smoothed Particle Hydrodynamic (SPH) method is introduced to mimic the speciality of solid-liquid mixture trait of hailstone during the impact process. The deformation and damage degree of upper and lower panel of sandwich plate are analysed. The application range and failure mode for the relevant structure, as well as the energy absorbing ratio between lattice structure and aluminium foam are summarized. Results show that the tetrahedral sandwich plate with aluminium foam core is confirmed the best for absorbing energy. Furthermore, the high absorption characteristics of foam material enhance the capability of the impact resistance for the composition with lattice structure without increasing the structure surface density. The results of study are of worth to provide a reliable basis for reduced weight aircraft wheel door.

Fascinating Foam - Diverse Applications, Unexpected Properties, and Characterization Challenges (PD2P Talk)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kropka, Jamie M.

2009-09-24

Foam pervades our everyday lives: we use it to bathe and shave, it floats atop our beer, cappuccino and pie, and it can even infect our bodies in the form of viruses. Although we are able to manipulate foam in these and many other common practices, there is still much we do not know about this fascinatingly complex material. In this talk, some of the intriguing aspects of foam, which could not be predicted based on its constituent components, will be discussed. Some challenging aspects of foam characterization, which have impeded the development of a thorough understanding of the materialmore » despite over a century of investigations, will also be presented. Despite these challenges, there are some known aspects of foams and these will be outlined along with how today's modern tools are being utilized to tell us more about foam structure and dynamics. A brief introduction to Sandia's interest in foams will then be given, and some of the current research we are conducting to further those interests will be discussed. This work is focused on the preparation of 'model' organic foams for use in developing an understanding of how to tune their stability and rheological response. Finally, physical and chemical methods to stabilize the foam will be described and possible new directions for the work will be presented.« less

Preparation of highly stable zeolite-alginate foam composite for strontium(90Sr) removal from seawater and evaluation of Sr adsorption performance.

PubMed

Hong, Hye-Jin; Kim, Byoung-Gyu; Ryu, Jungho; Park, In-Su; Chung, Kang-Sup; Lee, Sang Moon; Lee, Jin-Bae; Jeong, Hyeon Su; Kim, Hyunchul; Ryu, Taegong

2018-01-01

Alginate bead is a promising strontium (Sr) adsorbent in seawater, but highly concentrated Na ions caused over-swelling and damaged the hydrogel bead. To improve the mechanical stability of alginate bead, flexible foam-type zeolite-alginate composite was synthesized and Sr adsorption performance was evaluated in seawater; 1-10% zeolite immobilized alginate foams were prepared by freeze-dry technique. Immobilization of zeolite into alginate foam converted macro-pores to meso-pores which lead to more compact structure. It resulted in less swollen composite in seawater medium and exhibited highly improved mechanical stability compared with alginate bead. Besides, Sr adsorption efficiency and selectivity were enhanced by immobilization of zeolite in alginate foam due to the increase of Sr binding sites (zeolite). In particular, Sr selectivity against Na was highly improved. The 10% zeolite-alginate foam exhibited a higher log K d of 3.3, while the pure alginate foam exhibited 2.7 in the presence of 0.1 M Na. Finally, in the real seawater, the 10% zeolite-alginate foam exhibited 1.5 times higher Sr adsorption efficiency than the pure alginate foam. This result reveals that zeolite-alginate foam composite is appropriate material for Sr removal in seawater due to its swelling resistance as well as improved Sr adsorption performance in complex media. Copyright © 2017 Elsevier Ltd. All rights reserved.

Foam injection molding of thermoplastic elastomers: Blowing agents, foaming process and characterization of structural foams

NASA Astrophysics Data System (ADS)

Ries, S.; Spoerrer, A.; Altstaedt, V.

2014-05-01

Polymer foams play an important role caused by the steadily increasing demand to light weight design. In case of soft polymers, like thermoplastic elastomers (TPE), the haptic feeling of the surface is affected by the inner foam structure. Foam injection molding of TPEs leads to so called structural foam, consisting of two compact skin layers and a cellular core. The properties of soft structural foams like soft-touch, elastic and plastic behavior are affected by the resulting foam structure, e.g. thickness of the compact skins and the foam core or density. This inner structure can considerably be influenced by different processing parameters and the chosen blowing agent. This paper is focused on the selection and characterization of suitable blowing agents for foam injection molding of a TPE-blend. The aim was a high density reduction and a decent inner structure. Therefore DSC and TGA measurements were performed on different blowing agents to find out which one is appropriate for the used TPE. Moreover a new analyzing method for the description of processing characteristics by temperature dependent expansion measurements was developed. After choosing suitable blowing agents structural foams were molded with different types of blowing agents and combinations and with the breathing mold technology in order to get lower densities. The foam structure was analyzed to show the influence of the different blowing agents and combinations. Finally compression tests were performed to estimate the influence of the used blowing agent and the density reduction on the compression modulus.

Effects of porosity on corrosion resistance of Mg alloy foam produced by powder metallurgy technology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aghion, E., E-mail: egyon@bgu.ac.il; Perez, Y.

2014-10-15

Magnesium alloy foams have the potential to serve as structural material for regular light-weight applications as well as for biodegradable scaffold implants. However, their main disadvantage relates to the high reactivity of magnesium and consequently their natural tendency to corrode in regular service conditions and in physiological environments. The present study aims at evaluating the effect of porosity on the corrosion resistance of MRI 201S magnesium alloy foams in 0.9% NaCl solution and in phosphate buffer saline solution as a simulated physiological electrolyte. The magnesium foams were produced by powder metallurgy technology using space-holding particles to control the porosity content.more » Machined chips were used as raw material for the production of Mg alloy powder by milling process. The microstructure of the foams was examined using optical and scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy analysis. The corrosion behavior was evaluated by immersion test and potentiodynamic polarization analysis. The results obtained clearly demonstrate that the porosity has a significant effect on the corrosion resistance of the tested foams. Foams with 14–19% porosity have a corrosion rate of 4–10 mcd and 7–15 mcd in NaCl and phosphate buffer saline solution, respectively, compared to only 0.10 mcd for the same alloy in as cast conditions. This increased corrosion degradation of the Mg foams by more than one order of magnitude compared to the cast alloy may limit their potential application in regular and physiological environments. - Highlights: • Porosity has a detrimental effect on corrosion resistance of MRI 201S Mg foams. • 14–19% porosity increases the corrosion rate by more than one order of magnitude. • Accelerated corrosion limits the use of foams in regular/physiological environments.« less

Processing, Microstructure, and Properties of Engineered Diboride Structures

NASA Astrophysics Data System (ADS)

Wittmaier, Connor Charles

The mechanical properties and processing parameters of boride ceramics in foam and laminate architectures were evaluated. The ceramic reticulated foam was produced through a polymer substrate replication technique and the hardness and compressive strength were tested. The laminate structure was tested to evaluate the flexure strength and work of fracture as a function of temperature. The foam architecture was produced using a TiB2 slurry coating on a polyurethane reticulated foam preform. Foams sintered to 2150°C displayed an average grain size of 8.9 +/- 7.3 microm, and a hardness of 17.3 +/- 2.4 GPa. Crush testing foams were sintered at 1975°C, and displayed a specific strength of 208 +/- 63 kPa with an overall porosity of 97%. For these specimens, it is likely that microcracking lowered the hardness, but the overall strength was controlled by the bulk density. The laminate structures were fabricated using alternating layers of ZrB 2 and C-10 vol% ZrB2. The structures were fabricated through the shaping of ceramic loaded thermoplastic polymers that underwent burnout and hot pressing cycles. These specimens had strong phase ZrB2 layers that were about 150 mum thick alternating with weak phase layers that were about 20 mum thick. Specimens exhibited a maximum flexure strength of 311 +/- 10 MPa at 1600°C, and an increased work of fracture compared to conventional ZrB2 ceramics. The maximum fraction of inelastic work of fracture occurred at room temperature, and decreased as temperature increased. This was reflected in the length of the crack path through the specimen. Deflected cracks travelled through the center of the C-ZrB2 layers in the material in Mode II fracture.

Development of ultralight, super-elastic, hierarchical metallic meta-structures with i3DP technology

NASA Astrophysics Data System (ADS)

Zhang, Dongxing; Xiao, Junfeng; Moorlag, Carolyn; Guo, Qiuquan; Yang, Jun

2017-11-01

Lightweight and mechanically robust materials show promising applications in thermal insulation, energy absorption, and battery catalyst supports. This study demonstrates an effective method for creation of ultralight metallic structures based on initiator-integrated 3D printing technology (i3DP), which provides a possible platform to design the materials with the best geometric parameters and desired mechanical performance. In this study, ultralight Ni foams with 3D interconnected hollow tubes were fabricated, consisting of hierarchical features spanning three scale orders ranging from submicron to centimeter. The resultant materials can achieve an ultralight density of as low as 5.1 mg cm-3 and nearly recover after significant compression up to 50%. Due to a high compression ratio, the hierarchical structure exhibits superior properties in terms of energy absorption and mechanical efficiency. The relationship of structural parameters and mechanical response was established. The ability of achieving ultralight density <10 mg cm-3 and the stable \\bar{E}˜ {\\bar{ρ }}2 scaling through all range of relative density, indicates an advantage over the previous stochastic metal foams. Overall, this initiator-integrated 3D printing approach provides metallic structures with substantial benefits from the hierarchical design and fabrication flexibility to ultralight applications.

Thermo-mechanical characterization of silicone foams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rangaswamy, Partha; Smith, Nickolaus A.; Cady, Carl M.

Cellular solids such as elastomeric foams are used in many structural applications to absorb and dissipate energy, due to their light weight (low density) and high energy absorption capability. In this paper we will discuss foams derived from S5370, a silicone foam formulation developed by Dow Corning. In the application presented, the foam is consolidated into a cushion component of constant thickness but variable density. A mechanical material model developed by Lewis (2013), predicts material response, in part, as a function of relative density. To determine the required parameters for this model we have obtained the mechanical response in compressionmore » for ambient, cold and hot temperatures. The variable density cushion provided samples sufficient samples so that the effect of sample initial density on the mechanical response could be studied. The mechanical response data showed extreme sensitivity to relative density. We also observed at strains corresponding to 1 MPa a linear relationship between strain and initial density for all temperatures. Samples taken from parts with a history of thermal cycling demonstrated a stiffening response that was a function of temperature, with the trend of more stiffness as temperature increased above ambient. This observation is in agreement with the entropic effects on the thermo-mechanical behavior of silicone polymers. In this study, we present the experimental methods necessary for the development of a material model, the testing protocol, analysis of test data, and a discussion of load (stress) and gap (strain) as a function of sample initial densities and temperatures« less

Cost Benefit Analysis: Closed-Cell Polyurethane Foam Use in DOD Forward-Deployed Structures and As An Alternative Building Material to Reduce Operational Fuel Demand and Associated Costs

DTIC Science & Technology

2015-06-01

23 6. Disposal ...............................................................................................23 7. Health Hazards ...component spray foams, to as much as 8 to 24 hours for OCSF or CCSF. Due to the significant health hazards , the EPA stresses to err on the side of... Hazards and Concerns The EPA has indicated that there are serious health risks associated with the airborne aerosols, mists, and vapors that result

46 CFR 164.015-1 - Applicable specifications and standards.

Code of Federal Regulations, 2011 CFR

2011-10-01

..., CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL MATERIALS Plastic Foam, Unicellular, Buoyant, Sheet... following specification and standard, of the issue in effect on the date the plastic foam material is... be kept on file by the plastic foam manufacturer with this subpart. (1) The Federal Specification and...

46 CFR 164.015-1 - Applicable specifications and standards.

Code of Federal Regulations, 2014 CFR

2014-10-01

..., CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL MATERIALS Plastic Foam, Unicellular, Buoyant, Sheet... following specification and standard, of the issue in effect on the date the plastic foam material is... be kept on file by the plastic foam manufacturer with this subpart. (1) The Federal Specification and...

Poisson's Ratio of a Hyperelastic Foam Under Quasi-static and Dynamic Loading

DOE PAGES

Sanborn, Brett; Song, Bo

2018-06-03

Poisson's ratio is a material constant representing compressibility of material volume. However, when soft, hyperelastic materials such as silicone foam are subjected to large deformation into densification, the Poisson's ratio may rather significantly change, which warrants careful consideration in modeling and simulation of impact/shock mitigation scenarios where foams are used as isolators. The evolution of Poisson's ratio of silicone foam materials has not yet been characterized, particularly under dynamic loading. In this study, radial and axial measurements of specimen strain are conducted simultaneously during quasi-static and dynamic compression tests to determine the Poisson's ratio of silicone foam. The Poisson's ratiomore » of silicone foam exhibited a transition from compressible to nearly incompressible at a threshold strain that coincided with the onset of densification in the material. Poisson's ratio as a function of engineering strain was different at quasi-static and dynamic rates. Here, the Poisson's ratio behavior is presented and can be used to improve constitutive modeling of silicone foams subjected to a broad range of mechanical loading.« less

Poisson's Ratio of a Hyperelastic Foam Under Quasi-static and Dynamic Loading

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sanborn, Brett; Song, Bo

Poisson's ratio is a material constant representing compressibility of material volume. However, when soft, hyperelastic materials such as silicone foam are subjected to large deformation into densification, the Poisson's ratio may rather significantly change, which warrants careful consideration in modeling and simulation of impact/shock mitigation scenarios where foams are used as isolators. The evolution of Poisson's ratio of silicone foam materials has not yet been characterized, particularly under dynamic loading. In this study, radial and axial measurements of specimen strain are conducted simultaneously during quasi-static and dynamic compression tests to determine the Poisson's ratio of silicone foam. The Poisson's ratiomore » of silicone foam exhibited a transition from compressible to nearly incompressible at a threshold strain that coincided with the onset of densification in the material. Poisson's ratio as a function of engineering strain was different at quasi-static and dynamic rates. Here, the Poisson's ratio behavior is presented and can be used to improve constitutive modeling of silicone foams subjected to a broad range of mechanical loading.« less

Determination of elastomeric foam parameters for simulations of complex loading.

PubMed

Petre, M T; Erdemir, A; Cavanagh, P R

2006-08-01

Finite element (FE) analysis has shown promise for the evaluation of elastomeric foam personal protection devices. Although appropriate representation of foam materials is necessary in order to obtain realistic simulation results, material definitions used in the literature vary widely and often fail to account for the multi-mode loading experienced by these devices. This study aims to provide a library of elastomeric foam material parameters that can be used in FE simulations of complex loading scenarios. Twelve foam materials used in footwear were tested in uni-axial compression, simple shear and volumetric compression. For each material, parameters for a common compressible hyperelastic material model used in FE analysis were determined using: (a) compression; (b) compression and shear data; and (c) data from all three tests. Material parameters and Drucker stability limits for the best fits are provided with their associated errors. The material model was able to reproduce deformation modes for which data was provided during parameter determination but was unable to predict behavior in other deformation modes. Simulation results were found to be highly dependent on the extent of the test data used to determine the parameters in the material definition. This finding calls into question the many published results of simulations of complex loading that use foam material parameters obtained from a single mode of testing. The library of foam parameters developed here presents associated errors in three deformation modes that should provide for a more informed selection of material parameters.

Advanced nondestructive techniques applied for the detection of discontinuities in aluminum foams

NASA Astrophysics Data System (ADS)

Katchadjian, Pablo; García, Alejandro; Brizuela, Jose; Camacho, Jorge; Chiné, Bruno; Mussi, Valerio; Britto, Ivan

2018-04-01

Metal foams are finding an increasing range of applications by their lightweight structure and physical, chemical and mechanical properties. Foams can be used to fill closed moulds for manufacturing structural foam parts of complex shape [1]; foam filled structures are expected to provide good mechanical properties and energy absorption capabilities. The complexity of the foaming process and the number of parameters to simultaneously control, demand a preliminary and hugely wide experimental activity to manufacture foamed components with a good quality. That is why there are many efforts to improve the structure of foams, in order to obtain a product with good properties. The problem is that even for seemingly identical foaming conditions, the effective foaming can vary significantly from one foaming trial to another. The variation of the foams often is related by structural imperfections, joining region (foam-foam or foam-wall mold) or difficulties in achieving a complete filling of the mould. That is, in a closed mold, the result of the mold filling and its structure or defects are not known a priori and can eventually vary significantly. These defects can cause a drastic deterioration of the mechanical properties [2] and lead to a low performance in its application. This work proposes the use of advanced nondestructive techniques for evaluating the foam distribution after filling the mold to improve the manufacturing process. To achieved this purpose ultrasonic technique (UT) and cone beam computed tomography (CT) were applied on plate and structures of different thicknesses filled with foam of different porosity. UT was carried out on transmission mode with low frequency air-coupled transducers [3], in focused and unfocused configurations.

Preparation of Microcellular Epoxy Foams through a Limited-Foaming Process: A Contradiction with the Time-Temperature-Transformation Cure Diagram.

PubMed

Wang, Lijun; Zhang, Chun; Gong, Wei; Ji, Yubi; Qin, Shuhao; He, Li

2018-01-01

3D cross-linking networks are generated through chemical reactions between thermosetting epoxy resin and hardener during curing. The curing degree of epoxy material can be increased by increasing curing temperature and/or time. The epoxy material must then be fully cured through a postcuring process to optimize its material characteristics. Here, a limited-foaming method is introduced for the preparation of microcellular epoxy foams (Lim-foams) with improved cell morphology, high thermal expansion coefficient, and good compressive properties. Lim-foams exhibit a lower glass transition temperature (T g ) and curing degree than epoxy foams fabricated through free-foaming process (Fre-foams). Surprisingly, however, the T g of Lim-foams is unaffected by postcuring temperature and time. This phenomenon, which is related to high gas pressure in the bubbles, contradicts that indicated by the time-temperature-transformation cure diagram. High bubble pressure promotes the movement of molecular chains under heating at low temperature and simultaneously suppresses the etherification cross-linking reaction during post-curing. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Using Shock Waves to Improve the Acoustic Properties of Closed-Cell Foams

NASA Astrophysics Data System (ADS)

Brouillette, M.; Hébert, C.; Atalla, N.; Doutres, O.

Foam microstructure can be seen as a collection of interlinked struts forming a packing of cells interconnected to others through pores. Materials with a totality of pores closed by thin membranes are called closed-cell foams. The filtration and acoustic efficiency of closed-cell foams is poor compared to open-cell foams since it is very difficult for the fluid or the acoustic waves to penetrate inside the material.

Fracture Mechanical Analysis of Open Cell Ceramic Foams Under Thermal Shock Loading

NASA Astrophysics Data System (ADS)

Settgast, C.; Abendroth, M.; Kuna, M.

2016-11-01

Ceramic foams made by replica techniques containing sharp-edged cavities, which are potential crack initiators and therefore have to be analyzed using fracture mechanical methods. The ceramic foams made of novel carbon bonded alumina are used as filters in metal melt filtration applications, where the filters are exposed to a thermal shock. During the casting process the filters experience a complex thermo-mechanical loading, which is difficult to measure. Modern numerical methods allow the simulation of such complex processes. As a simplified foam structure an open Kelvin cell is used as a representative volume element. A three-dimensional finite element model containing realistic sharp-edged cavities and three-dimensional sub-models along these sharp edges are used to compute the transient temperature, stress and strain fields at the Kelvin foam. The sharp edges are evaluated using fracture mechanical methods like the J-integral technique. The results of this study describe the influence of the pore size, relative density of the ceramic foam, the heat transfer and selected material parameters on the fracture mechanical behaviour.

Mechanically Robust, Ultraelastic Hierarchical Foam with Tunable Properties via 3D Printing

DOE PAGES

Chen, Qiyi; Cao, Peng-Fei; Advincula, Rigoberto C.

2018-04-11

We present a mechanically robust, ultraelastic foam with controlled multiscale architectures and tunable mechanical/conductive performance is fabricated via 3D printing. Hierarchical porosity, including both macro- and microscaled pores, are produced by the combination of direct ink writing (DIW), acid etching, and phase inversion. The thixotropic inks in DIW are formulated by a simple one-pot process to disperse duo nanoparticles (nanoclay and silica nanoparticles) in a polyurethane suspension. The resulting lightweight foam exhibits tailorable mechanical strength, unprecedented elasticity (standing over 1000 compression cycles), and remarkable robustness (rapidly and fully recover after a load more than 20 000 times of its ownmore » weight). Surface coating of carbon nanotubes yields a conductive elastic foam that can be used as piezoresistivity sensor with high sensitivity. For the first time, this strategy achieves 3D printing of elastic foam with controlled multilevel 3D structures and mechanical/conductive properties. In conclusion, the facile ink preparation method can be utilized to fabricate foams of various materials with desirable performance via 3D printing.« less

Mechanically Robust, Ultraelastic Hierarchical Foam with Tunable Properties via 3D Printing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Qiyi; Cao, Peng-Fei; Advincula, Rigoberto C.

We present a mechanically robust, ultraelastic foam with controlled multiscale architectures and tunable mechanical/conductive performance is fabricated via 3D printing. Hierarchical porosity, including both macro- and microscaled pores, are produced by the combination of direct ink writing (DIW), acid etching, and phase inversion. The thixotropic inks in DIW are formulated by a simple one-pot process to disperse duo nanoparticles (nanoclay and silica nanoparticles) in a polyurethane suspension. The resulting lightweight foam exhibits tailorable mechanical strength, unprecedented elasticity (standing over 1000 compression cycles), and remarkable robustness (rapidly and fully recover after a load more than 20 000 times of its ownmore » weight). Surface coating of carbon nanotubes yields a conductive elastic foam that can be used as piezoresistivity sensor with high sensitivity. For the first time, this strategy achieves 3D printing of elastic foam with controlled multilevel 3D structures and mechanical/conductive properties. In conclusion, the facile ink preparation method can be utilized to fabricate foams of various materials with desirable performance via 3D printing.« less

Extracting material response from simple mechanical tests on hardening-softening-hardening viscoplastic solids

NASA Astrophysics Data System (ADS)

Mohan, Nisha

Compliant foams are usually characterized by a wide range of desirable mechanical properties. These properties include viscoelasticity at different temperatures, energy absorption, recoverability under cyclic loading, impact resistance, and thermal, electrical, acoustic and radiation-resistance. Some foams contain nano-sized features and are used in small-scale devices. This implies that the characteristic dimensions of foams span multiple length scales, rendering modeling their mechanical properties difficult. Continuum mechanics-based models capture some salient experimental features like the linear elastic regime, followed by non-linear plateau stress regime. However, they lack mesostructural physical details. This makes them incapable of accurately predicting local peaks in stress and strain distributions, which significantly affect the deformation paths. Atomistic methods are capable of capturing the physical origins of deformation at smaller scales, but suffer from impractical computational intensity. Capturing deformation at the so-called meso-scale, which is capable of describing the phenomenon at a continuum level, but with some physical insights, requires developing new theoretical approaches. A fundamental question that motivates the modeling of foams is `how to extract the intrinsic material response from simple mechanical test data, such as stress vs. strain response?' A 3D model was developed to simulate the mechanical response of foam-type materials. The novelty of this model includes unique features such as the hardening-softening-hardening material response, strain rate-dependence, and plastically compressible solids with plastic non-normality. Suggestive links from atomistic simulations of foams were borrowed to formulate a physically informed hardening material input function. Motivated by a model that qualitatively captured the response of foam-type vertically aligned carbon nanotube (VACNT) pillars under uniaxial compression [2011,"Analysis of Uniaxial Compression of Vertically Aligned Carbon Nanotubes," J. Mech.Phys. Solids, 59, pp. 2227--2237, Erratum 60, 1753-1756 (2012)], the property space exploration was advanced to three types of simple mechanical tests: 1) uniaxial compression, 2) uniaxial tension, and 3) nanoindentation with a conical and a flat-punch tip. The simulations attempt to explain some of the salient features in experimental data, like 1) The initial linear elastic response. 2) One or more nonlinear instabilities, yielding, and hardening. The model-inherent relationships between the material properties and the overall stress-strain behavior were validated against the available experimental data. The material properties include the gradient in stiffness along the height, plastic and elastic compressibility, and hardening. Each of these tests was evaluated in terms of their efficiency in extracting material properties. The uniaxial simulation results proved to be a combination of structural and material influences. Out of all deformation paths, flat-punch indentation proved to be superior since it is the most sensitive in capturing the material properties.

Fabrication and Properties of polyacrylic acid by ionic surfactant disturbance method

NASA Astrophysics Data System (ADS)

Lawan, S.; Osotchan, T.; Chuajiw, W.; Subannajui, K.

2017-09-01

The formation of polymeric materials can be achieved by several methods such as melting and casting, screw extrusion, cross-linking of resin or rubber in a mold, and so on. In this work, the polyacrylic acid is formed by using the emulsion disturbance method. Despite extensively used in the colour painting and coating industries, acrylic emulsion can be processed into a foam and powder configuration by a reaction between acrylic emulsion and salt. The solidification hardly changes the volume between liquid emulsion and solidified polymer which means the final structure of polyacrylic acid is filled with opened air cells. The opened air cell structure is confirmed by the result from scanning electron microscopy. The chemical analysis and crystallography of acrylic powder and foam are examined by Fourier-transform infrared spectroscopy and X-ray diffraction respectively. The phase transformation and Thermal stability are studied by differential scanning calorimetry and thermo gravimetric analysis. Moreover, the mechanical properties of acrylic foam were observed by tensile, compressive and hardness test. In addition to the basic property analysis, acrylic foam was also used in the particle filtration application.

Development of high-performance biodegradable rigid polyurethane foams using all bioresource-based polyols: Lignin and soy oil-derived polyols.

PubMed

Luo, Xiaogang; Xiao, Yuqin; Wu, Qiangxian; Zeng, Jian

2018-04-25

Development of biodegradable polyurethane materials is the most promising in the wider context of the "greening" of industrial chemistry. To tackle this challenge, a novel biodegradable polyurethane foam from all bioresource-based polyols (lignin and soy oil-derived polyols) and polymeric methyldiphenyl diisocyanate (pMDI) have been synthesized via a one-pot and self-rising process. All these foam samples have the internal cellular morphology and microstructure. FTIR result exhibits characteristic peaks of polyurethane, and indicates covalent bonds between soy-based polyurethane and lignin, and the lignin powders can react with pMDI via active -H and -CNO. In addition, hydrogen bonding also plays an important role in forming the 3D structures. These interactions and chemical bonds made the prepared foam samples form the 3D macromolecular structure with improved mechanical, thermal, and biodegradable properties. The reaction process is time-saving and cost-effective as it requires no blowing agent and minimum processing steps, while exploring the potential of using the higher content of nature bioresource constituents. Copyright © 2018 Elsevier B.V. All rights reserved.

Design and evaluation of foamed asphalt base materials.

DOT National Transportation Integrated Search

2013-05-01

Foamed asphalt stabilized base (FASB) combines reclaimed asphalt pavement (RAP), recycled : concrete (RC), and/or graded aggregate base (GAB) with a foamed asphalt binder to produce a : partially stabilized base material. The objectives of this study...

Design and evaluation of foamed asphalt base materials : [research summary].

DOT National Transportation Integrated Search

2013-05-01

Foamed asphalt stabilized base (FASB) combines reclaimed asphalt pavement (RAP), : recycled concrete (RC), and/or graded aggregate base (GAB) with a foamed asphalt : binder to produce a partially stabilized base material. Although widely used, most :...

Hole Quality Assessment in Drilling of Glass Microballoon/Epoxy Syntactic Foams

NASA Astrophysics Data System (ADS)

Ashrith, H. S.; Doddamani, Mrityunjay; Gaitonde, Vinayak; Gupta, Nikhil

2018-05-01

Syntactic foams reinforced with glass microballoons are used as alternatives for conventional materials in structural application of aircrafts and automobiles due to their unique properties such as light weight, high compressive strength, and low moisture absorption. Drilling is the most commonly used process of making holes for assembling structural components. In the present investigation, grey relation analysis (GRA) is used to optimize cutting speed, feed, drill diameter, and filler content to minimize cylindricity, circularity error, and damage factor. Experiments based on full factorial design are conducted using a vertical computer numerical control machine and tungsten carbide twist drills. GRA reveals that a combination of lower cutting speed, filler content, and drill diameter produces a good quality hole at optimum intermediate feed in drilling syntactic foams composites. GRA also shows that the drill diameter has a significant effect on the hole quality. Furthermore, damage on the hole exit side is analyzed using a scanning electron microscope.

Laminated Object Manufacturing of 3D-Printed Laser-Induced Graphene Foams.

PubMed

Luong, Duy Xuan; Subramanian, Ajay K; Silva, Gladys A Lopez; Yoon, Jongwon; Cofer, Savannah; Yang, Kaichun; Owuor, Peter Samora; Wang, Tuo; Wang, Zhe; Lou, Jun; Ajayan, Pulickel M; Tour, James M

2018-05-29

Laser-induced graphene (LIG), a graphene structure synthesized by a one-step process through laser treatment of commercial polyimide (PI) film in an ambient atmosphere, has been shown to be a versatile material in applications ranging from energy storage to water treatment. However, the process as developed produces only a 2D product on the PI substrate. Here, a 3D LIG foam printing process is developed on the basis of laminated object manufacturing, a widely used additive-manufacturing technique. A subtractive laser-milling process to yield further refinements to the 3D structures is also developed and shown here. By combining both techniques, various 3D graphene objects are printed. The LIG foams show good electrical conductivity and mechanical strength, as well as viability in various energy storage and flexible electronic sensor applications. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Phenomenological study of a cellular material behaviour under dynamic loadings

NASA Astrophysics Data System (ADS)

Bouix, R.; Viot, Ph.; Lataillade, J.-L.

2006-08-01

Polypropylene foams are cellular materials, which are often use to fill structures subjected to crash or violent impacts. Therefore, it is necessary to know and to characterise in experiments their mechanical behaviour in compression at high strain rates. So, several apparatus have been used in order to highlight the influence of strain rate, material density and also temperature. A split Hopkinson Pressure Bar has been used for impact tests, a fly wheel to test theses materials at medium strain rate and an electro-mechanical testing machine associated to a climatic chamber for temperature tests. Then, a rheological model has been used in order to describe the material behaviour. The mechanical response to compression of these foams presents three typical domains: a linear elastic step, a wide collapse plateau stress, which leads to a densification, which are related to a standard rheological model.

Fire-Retardant, Self-Extinguishing Inorganic/Polymer Composite Memory Foams.

PubMed

Chatterjee, Soumyajyoti; Shanmuganathan, Kadhiravan; Kumaraswamy, Guruswamy

2017-12-27

Polymeric foams used in furniture and automotive and aircraft seating applications rely on the incorporation of environmentally hazardous fire-retardant additives to meet fire safety norms. This has occasioned significant interest in novel approaches to the elimination of fire-retardant additives. Foams based on polymer nanocomposites or based on fire-retardant coatings show compromised mechanical performance and require additional processing steps. Here, we demonstrate a one-step preparation of a fire-retardant ice-templated inorganic/polymer hybrid that does not incorporate fire-retardant additives. The hybrid foams exhibit excellent mechanical properties. They are elastic to large compressional strain, despite the high inorganic content. They also exhibit tunable mechanical recovery, including viscoelastic "memory". These hybrid foams are prepared using ice-templating that relies on a green solvent, water, as a porogen. Because these foams are predominantly comprised of inorganic components, they exhibit exceptional fire retardance in torch burn tests and are self-extinguishing. After being subjected to a flame, the foam retains its porous structure and does not drip or collapse. In micro-combustion calorimetry, the hybrid foams show a peak heat release rate that is only 25% that of a commercial fire-retardant polyurethanes. Finally, we demonstrate that we can use ice-templating to prepare hybrid foams with different inorganic colloids, including cheap commercial materials. We also demonstrate that ice-templating is amenable to scale up, without loss of mechanical performance or fire-retardant properties.

Effect of crumb-rubber particle size on mechanical response of polyurethane foam composites

NASA Astrophysics Data System (ADS)

Sanjay, Omer Sheik

The compression properties of foam are governed by by three factors: i) cell edge bending ii) compression of cell fluid iii) membrane stresses in the cell faces. The effect of reinforcement, granular form of scrap tire rubber on contribution of each of these effects along with the physical properties of polyurethane foam is investigated. It is seen that the addition of crumb-rubber hinders the formation of cell membranes during the foaming process. Four different sizes of particles were chosen to closely study the effect of particle size on the physical properties of the foam composite. There is a definite pattern seen in each of the physical property of the composite with change in the particle size. Addition of crumb-rubber decreases the compressive strength but in turn increases the elastic modulus of the composite. The rubber particles act as the sites for stress concentration and hence the inclusion of rubber particles induces the capability to transfer the axial load laterally along the surface of the foam. Also, the filler material induces porosity into the foam, which is seen in the SEM images, and hence the addition of rubber particles induces brittleness, which makes the foam composites extensively applicable for structural application in sandwich components. The lightweight composite therefore is a potential substitute to the heavier metal foams and honeycombs as a protective layer.

Design and evaluation of low-cost stainless steel fiberglass foam blades for large wind driven generating systems

NASA Technical Reports Server (NTRS)

Eggert, W. S.

1982-01-01

A low cost wind turbine blade based on a stainless steel fiberglass foam Budd blade design concept, was evaluated for its principle characteristics, low cost features, and its advantages and disadvantages. A blade structure was designed and construction methods and materials were selected. A complete blade tooling concepts, various technical and economic analysis, and evaluations of the blade design were performed. A comprehensive fatigue test program is conducted to provide data to verify the design stress allowables.

Design and evaluation of low-cost stainless steel fiberglass foam blades for large wind driven generating systems

NASA Astrophysics Data System (ADS)

Eggert, W. S.

1982-10-01

A low cost wind turbine blade based on a stainless steel fiberglass foam Budd blade design concept, was evaluated for its principle characteristics, low cost features, and its advantages and disadvantages. A blade structure was designed and construction methods and materials were selected. A complete blade tooling concepts, various technical and economic analysis, and evaluations of the blade design were performed. A comprehensive fatigue test program is conducted to provide data to verify the design stress allowables.

Spinous α-Fe2O3 hierarchical structures anchored on Ni foam for supercapacitor electrodes and visible light driven photocatalysts.

PubMed

Zheng, Xin; Han, Zhicheng; Yao, Shunyu; Xiao, Huanhao; Chai, Fang; Qu, Fengyu; Wu, Xiang

2016-04-28

Spinous α-Fe2O3 hierarchical structures grown on a Ni foam substrate have been successfully obtained by a facile one-step hydrothermal method. The prepared products are functionalized as supercapacitor electrodes without adding any ancillary materials such as carbon black or binders. Their electrochemical properties show a high discharge areal capacitance (681 mF cm(-2) at 1 mA cm(-2)), good rate performance (495 mF cm(-2) at 5 mA cm(-2)) and long-term cycling stability (23.9% loss after 6000 repetitive cycles at 1 mA cm(-2)). Such excellent supercapacitive characteristics could be mainly attributed to their unique spatial structures which provide many active sites and enhance the combination between the electrode and Ni foam to support fast ion and electron transfer. In addition, the prepared α-Fe2O3 product is also used as a photocatalyst for the photocatalytic degradation of several harmful organic dyes under visible light illumination. By comparing the photocatalytic performance towards Congo red dye with other photocatalysts, it was observed that the prepared spinous α-Fe2O3 hierarchical structure exhibited superior photocatalytic performance. Finally, photocatalytic recycle tests showed the superiority of the prepared α-Fe2O3 product. This demonstrates that spinous α-Fe2O3 structures could be promising candidate materials for high-capacity, low-cost supercapacitor electrodes and environmentally friendly photocatalysts.

The Imagery of Sound

NASA Technical Reports Server (NTRS)

2000-01-01

Automated Analysis Corporation's COMET is a suite of acoustic analysis software for advanced noise prediction. It analyzes the origin, radiation, and scattering of noise, and supplies information on how to achieve noise reduction and improve sound characteristics. COMET's Structural Acoustic Foam Engineering (SAFE) module extends the sound field analysis capability of foam and other materials. SAFE shows how noise travels while airborne, how it travels within a structure, and how these media interact to affect other aspects of the transmission of noise. The COMET software reduces design time and expense while optimizing a final product's acoustical performance. COMET was developed through SBIR funding and Langley Research Center for Automated Analysis Corporation.

Electrical connection structure for a superconductor element

DOEpatents

Lallouet, Nicolas; Maguire, James

2010-05-04

The invention relates to an electrical connection structure for a superconductor element cooled by a cryogenic fluid and connected to an electrical bushing, which bushing passes successively through an enclosure at an intermediate temperature between ambient temperature and the temperature of the cryogenic fluid, and an enclosure at ambient temperature, said bushing projecting outside the ambient temperature enclosure. According to the invention, said intermediate enclosure is filled at least in part with a solid material of low thermal conductivity, such as a polyurethane foam or a cellular glass foam. The invention is applicable to connecting a superconductor cable at cryogenic temperature to a device for equipment at ambient temperature.

40 CFR 63.8830 - What definitions apply to this subpart?

Code of Federal Regulations, 2012 CFR

2012-07-01

... (CONTINUED) National Emission Standards for Hazardous Air Pollutants: Flexible Polyurethane Foam Fabrication... chemical substance that is applied for the purpose of bonding foam to foam, foam to fabric, or foam to any... means the process of bonding flexible foam to one or more layers of material by heating the foam surface...

40 CFR 63.8830 - What definitions apply to this subpart?

Code of Federal Regulations, 2010 CFR

2010-07-01

... (CONTINUED) National Emission Standards for Hazardous Air Pollutants: Flexible Polyurethane Foam Fabrication... chemical substance that is applied for the purpose of bonding foam to foam, foam to fabric, or foam to any... means the process of bonding flexible foam to one or more layers of material by heating the foam surface...

40 CFR 63.8830 - What definitions apply to this subpart?

Code of Federal Regulations, 2013 CFR

2013-07-01

... (CONTINUED) National Emission Standards for Hazardous Air Pollutants: Flexible Polyurethane Foam Fabrication... chemical substance that is applied for the purpose of bonding foam to foam, foam to fabric, or foam to any... means the process of bonding flexible foam to one or more layers of material by heating the foam surface...

40 CFR 63.8830 - What definitions apply to this subpart?

Code of Federal Regulations, 2011 CFR

2011-07-01

... (CONTINUED) National Emission Standards for Hazardous Air Pollutants: Flexible Polyurethane Foam Fabrication... chemical substance that is applied for the purpose of bonding foam to foam, foam to fabric, or foam to any... means the process of bonding flexible foam to one or more layers of material by heating the foam surface...

40 CFR 63.8830 - What definitions apply to this subpart?

Code of Federal Regulations, 2014 CFR

2014-07-01

... (CONTINUED) National Emission Standards for Hazardous Air Pollutants: Flexible Polyurethane Foam Fabrication... chemical substance that is applied for the purpose of bonding foam to foam, foam to fabric, or foam to any... means the process of bonding flexible foam to one or more layers of material by heating the foam surface...

Biopolymer foams - Relationship between material characteristics and foaming behavior of cellulose based foams

NASA Astrophysics Data System (ADS)

Rapp, F.; Schneider, A.; Elsner, P.

2014-05-01

Biopolymers are becoming increasingly important to both industry and consumers. With regard to waste management, CO2 balance and the conservation of petrochemical resources, increasing efforts are being made to replace standard plastics with bio-based polymers. Nowadays biopolymers can be built for example of cellulose, lactic acid, starch, lignin or bio mass. The paper will present material properties of selected cellulose based polymers (cellulose propionate [CP], cellulose acetate butyrate [CAB]) and corresponding processing conditions for particle foams as well as characterization of produced parts. Special focus is given to the raw material properties by analyzing thermal behavior (differential scanning calorimetry), melt strength (Rheotens test) and molecular weight distribution (gel-permeation chromatography). These results will be correlated with the foaming behavior in a continuous extrusion process with physical blowing agents and underwater pelletizer. Process set-up regarding particle foam technology, including extrusion foaming and pre-foaming, will be shown. The characteristics of the resulting foam beads will be analyzed regarding part density, cell morphology and geometry. The molded parts will be tested on thermal conductivity as well as compression behavior (E-modulus, compression strength).

Advanced materials for thermal protection system

NASA Astrophysics Data System (ADS)

Heng, Sangvavann; Sherman, Andrew J.

1996-03-01

Reticulated open-cell ceramic foams (both vitreous carbon and silicon carbide) and ceramic composites (SiC-based, both monolithic and fiber-reinforced) were evaluated as candidate materials for use in a heat shield sandwich panel design as an advanced thermal protection system (TPS) for unmanned single-use hypersonic reentry vehicles. These materials were fabricated by chemical vapor deposition/infiltration (CVD/CVI) and evaluated extensively for their mechanical, thermal, and erosion/ablation performance. In the TPS, the ceramic foams were used as a structural core providing thermal insulation and mechanical load distribution, while the ceramic composites were used as facesheets providing resistance to aerodynamic, shear, and erosive forces. Tensile, compressive, and shear strength, elastic and shear modulus, fracture toughness, Poisson's ratio, and thermal conductivity were measured for the ceramic foams, while arcjet testing was conducted on the ceramic composites at heat flux levels up to 5.90 MW/m2 (520 Btu/ft2ṡsec). Two prototype test articles were fabricated and subjected to arcjet testing at heat flux levels of 1.70-3.40 MW/m2 (150-300 Btu/ft2ṡsec) under simulated reentry trajectories.

Tribology and Friction of Soft Materials: Mississippi State Case Study

DTIC Science & Technology

2010-03-18

elastomers , foams, and fabrics. B. Develop internal state variable (ISV) material model. Model will be calibrated using database and verified...Rubbers Natural rubber Santoprene (Vulcanized Elastomer ) Styrene Butadiene Rubber (SBR) Foams Polypropylene Foam Polyurethane Foam Fabrics Kevlar...Axially symmetric model PC Disk PC Numerical Implementation in FEM Codes Experiment SEM Optical methods ISV Model Void Nucleation FEM Analysis

Foamed lightweight materials made from mixed scrap metal waste powder and sewage sludge ash.

PubMed

Wang, Kuen-Sheng; Chiou, Ing-Jia

2004-10-01

The porous properties and pozzolanic effects of sewage sludge ash (SSA) make it possible to produce lightweight materials. This study explored the effects of different metallic foaming agents, made from waste aluminium products, on the foaming behaviours and engineering characteristics, as well as the microstructure of sewage sludge ash foamed lightweight materials. The results indicated that aluminium powder and mixed scrap metal waste powder possessed similar chemical compositions. After proper pre-treatment, waste aluminium products proved to be ideal substitutes for metallic foaming agents. Increasing the amount of mixed scrap metal waste by 10-15% compared with aluminium powder would produce a similar foaming ratio and compressive strength. The reaction of the metallic foaming agents mainly produced pores larger than 10 microm, different from the hydration reaction of cement that produced pores smaller than 1 microm mostly. To meet the requirements of the lightweight materials characteristics and the compressive strength, the amount of SSA could be up to 60-80% of the total solids. An adequate amount of aluminium powder is 0.5-0.9% of the total solids. Increasing the fineness of the mixed scrap metal waste powder could effectively reduce the amount required and improve the foaming ratio.

Exploiting novel sterilization techniques for porous polyurethane scaffolds.

PubMed

Bertoldi, Serena; Farè, Silvia; Haugen, Håvard Jostein; Tanzi, Maria Cristina

2015-05-01

Porous polyurethane (PU) structures raise increasing interest as scaffolds in tissue engineering applications. Understanding the effects of sterilization on their properties is mandatory to assess their potential use in the clinical practice. The aim of this work is the evaluation of the effects of two innovative sterilization techniques (i.e. plasma, Sterrad(®) system, and ozone) on the morphological, chemico-physical and mechanical properties of a PU foam synthesized by gas foaming, using water as expanding agent. In addition, possible toxic effects of the sterilization were evaluated by in vitro cytotoxicity tests. Plasma sterilization did not affect the morphological and mechanical properties of the PU foam, but caused at some extent degradative phenomena, as detected by infrared spectroscopy. Ozone sterilization had a major effect on foam morphology, causing the formation of new small pores, and stronger degradation and oxidation on the structure of the material. These modifications affected the mechanical properties of the sterilized PU foam too. Even though, no cytotoxic effects were observed after both plasma and ozone sterilization, as confirmed by the good values of cell viability assessed by Alamar Blue assay. The results here obtained can help in understanding the effects of sterilization procedures on porous polymeric scaffolds, and how the scaffold morphology, in particular porosity, can influence the effects of sterilization, and viceversa.

Hierarchical NiCo2 S4 Nanotube@NiCo2 S4 Nanosheet Arrays on Ni Foam for High-Performance Supercapacitors.

PubMed

Chen, Haichao; Chen, Si; Shao, Hongyan; Li, Chao; Fan, Meiqiang; Chen, Da; Tian, Guanglei; Shu, Kangying

2016-01-01

Hierarchical NiCo2 S4 nanotube@NiCo2 S4 nanosheet arrays on Ni foam have been successfully synthesized. Owing to the unique hierarchical structure, enhanced capacitive performance can be attained. A specific capacitance up to 4.38 F cm(-2) is attained at 5 mA cm(-2) , which is much higher than the specific capacitance values of NiCo2 O4 nanosheet arrays, NiCo2 S4 nanosheet arrays and NiCo2 S4 nanotube arrays on Ni foam. The hierarchical NiCo2 S4 nanostructure shows superior cycling stability; after 5000 cycles, the specific capacitance still maintains 3.5 F cm(-2) . In addition, through the morphology and crystal structure measurement after cycling stability test, it is found that the NiCo2 S4 electroactive materials are gradually corroded; however, the NiCo2 S4 phase can still be well-maintained. Our results show that hierarchical NiCo2 S4 nanostructures are suitable electroactive materials for high performance supercapacitors. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Study of sound-absorbing properties of glass-fiber reinforced materials used in engineering

NASA Astrophysics Data System (ADS)

Egorova, V. E.; Habibova, R. R.; Shafigullin, L. N.

2017-09-01

Modern engineering makes high demands to the noise level in the passenger compartment or cabin of KAMAZ. An effective means of dealing with noise is to use sound absorbing materials produced by the automotive industry. To increase sound-absorbing capacity of materials and structures using glass fibre reinforced polyurethane foams (PUF) obtained by the technology Fiber Composite Spraying.

Lightweight solar concentrator structures, phase 2

NASA Technical Reports Server (NTRS)

Williams, Brian E.; Kaplan, Richard B.

1993-01-01

This report summarizes the results of the program conducted by Ultramet under SBIR Phase 2 Contract NAS3-25418. The objective of this program was to develop lightweight materials and processes for advanced high accuracy Space Solar Concentrators using rigidized foam for the substrate structure with an integral optical surface.

Evaluation of foaming polypropylene modified with ramified polymer

NASA Astrophysics Data System (ADS)

Demori, Renan; de Azeredo, Ana Paula; Liberman, Susana A.; Mauler, Raquel S.

2015-05-01

Polypropylene foams have great industrial interest because of balanced physical and mechanical properties, recyclability as well as low material cost. During the foaming process, the elongational forces applied to produce the expanded polymer are strong enough to rupture cell walls. As a result, final foam has a high amount of coalesced as well as opened cells which decreases mechanical and also physical properties. To increase melt strength and also avoid the coalescence effect, one of the current solution is blend PP with ramified polymers as well as branched polypropylene (LCBPP) or ethylene-octene copolymer (POE). In this research to provide extensional properties and achieve uniform cellular structures of expanded PP, 20 phr of LCBPP or POE was added into PP matrix. The blend of PP with ramified polymers was prepared by twin-screw extrusion. Injection molding process was used to produce PP foams using azodicarbonamide (ACA) as chemical blowing agent. The morphological results of the expanded PP displayed a non-uniform geometrical cell, apparent density of 0.48 g/cm3 and cell density of 13.9.104 cell/cm3. Otherwise, the expanded PP blended with LCBPP or POE displayed a homogeneous cell structure and increased the amount of smaller cells (50-100 μm of size). The apparent density slightly increased with addition of LCBPP or POE, 0.64 and 0.57 g/cm3, respectively. Thus, the cell density reduced to 65% in PP/LCBPP 100/20 and 75% in the sample PP/POE 100/20 compared to expanded PP. The thermo-mechanical properties (DMTA) of PP showed specific stiffness of 159 MPa.cm-3.g-1, while the sample PP/LCBPP 100/20 increased the stiffness values of 10%. Otherwise, the expanded PP/POE 100/20 decreased the specific stiffness values at -30%, in relation to expanded PP. In summary, blending PP with ramified polymers showed increasing of the homogenous cellular structure as well as the amount of smaller cells in the expanded material.

Plasma-Spray Metal Coating On Foam

NASA Technical Reports Server (NTRS)

Cranston, J.

1994-01-01

Molds, forms, and other substrates made of foams coated with metals by plasma spraying. Foam might be ceramic, carbon, metallic, organic, or inorganic. After coat applied by plasma spraying, foam left intact or removed by acid leaching, conventional machining, water-jet cutting, or another suitable technique. Cores or vessels made of various foam materials plasma-coated with metals according to method useful as thermally insulating containers for foods, liquids, or gases, or as mandrels for making composite-material (matrix/fiber) parts, or making thermally insulating firewalls in automobiles.

Spacecraft Shielding: An Experimental Comparison Between Open Cell Aluminium Foam Core Sandwich Panel Structures and Whipple Shielding.

NASA Astrophysics Data System (ADS)

Pasini, D. L. S.; Price, M. C.; Burchell, M. J.; Cole, M. J.

2013-09-01

Spacecraft shielding is generally provided by metallic plates in a Whipple shield type configuration [1] where possible. However, mission restrictions such as spacecraft payload mass, can prevent the inclusion of a dedicated protective structure for prevention against impact damage from micrometeoroids. Due to this, often the spacecraft's primary structure will act as the de facto shield. This is commonly an aluminium honeycomb backed with either glass fibre reinforced plastic (GFRP) or aluminium faceplates [2]. Such materials are strong, lightweight and relatively cheap due to their abundance used within the aerospace industry. However, these materials do not offer the best protection (per unit weight) against hypervelocity impact damage. A new material for shielding (porous aluminium foam [3]) is suggested for low risk space missions. Previous studies by NASA [4] have been performed to test this new material against hypervelocity impacts using spherical aluminium projectiles. This showed its potential for protection for satellites in Earth orbit, against metallic space debris. Here we demonstrate the material's protective capabilities against micrometeoroids, using soda-lime glass spheres as projectiles to accurately gauge its potential with relation to silicatious materials, such as micrometeoroids and natural solar system debris. This is useful for spacecraft missions beyond Earth orbit where solar system materials are the dominant threat (via hypervelocity impacts) to the spacecraft, rather than manmade debris.

Identifying local characteristic lengths governing sound wave properties in solid foams

NASA Astrophysics Data System (ADS)

Tan Hoang, Minh; Perrot, Camille

2013-02-01

Identifying microscopic geometric properties and fluid flow through opened-cell and partially closed-cell solid structures is a challenge for material science, in particular, for the design of porous media used as sound absorbers in building and transportation industries. We revisit recent literature data to identify the local characteristic lengths dominating the transport properties and sound absorbing behavior of polyurethane foam samples by performing numerical homogenization simulations. To determine the characteristic sizes of the model, we need porosity and permeability measurements in conjunction with ligament lengths estimates from available scanning electron microscope images. We demonstrate that this description of the porous material, consistent with the critical path picture following from the percolation arguments, is widely applicable. This is an important step towards tuning sound proofing properties of complex materials.

Influence of calcium addition and stirring on the cellular structure and foaming behavior of molten zinc

NASA Astrophysics Data System (ADS)

Hossein Elahi, S.; Arabi Jeshvaghani, R.; Shahverdi, H. R.

2015-05-01

In this paper, the influence of calcium addition and melt stirring on the structure and foaming behavior of molten zinc was investigated. In this regard, zinc foam was produced by Alporas method (in which foam alloy melts and titanium hydride is used as a blowing agent). Optical microscopy and scanning electron microscopy were used to investigate the phase distribution and structure in the foams. Results showed that addition of calcium increased foamability and foam efficiency of the molten zinc. In contrast, stirring had no significant effect on the foaming behavior of the melt. Microstructural examinations indicated that improving the foaming behavior of molten zinc was attributed to the formation of CaZn13 intermetallic phase and ZnO particles in the foam structure, which increased viscosity and reduced drainage rate.

46 CFR 108.469 - Quantity of foam producing materials.

Code of Federal Regulations, 2012 CFR

2012-10-01

... at least 5 minutes at each outlet; and (2) In a space must have enough foam producing material to... or space, the system need have only enough foam producing material to cover the largest space that the system covers or, if the liquid surface of a tank covered by the system is larger, the tank with...

46 CFR 108.469 - Quantity of foam producing materials.

Code of Federal Regulations, 2011 CFR

2011-10-01

... at least 5 minutes at each outlet; and (2) In a space must have enough foam producing material to... or space, the system need have only enough foam producing material to cover the largest space that the system covers or, if the liquid surface of a tank covered by the system is larger, the tank with...

46 CFR 108.469 - Quantity of foam producing materials.

Code of Federal Regulations, 2013 CFR

2013-10-01

... at least 5 minutes at each outlet; and (2) In a space must have enough foam producing material to... or space, the system need have only enough foam producing material to cover the largest space that the system covers or, if the liquid surface of a tank covered by the system is larger, the tank with...

46 CFR 108.469 - Quantity of foam producing materials.

Code of Federal Regulations, 2010 CFR

2010-10-01

... at least 5 minutes at each outlet; and (2) In a space must have enough foam producing material to... or space, the system need have only enough foam producing material to cover the largest space that the system covers or, if the liquid surface of a tank covered by the system is larger, the tank with...

46 CFR 108.469 - Quantity of foam producing materials.

Code of Federal Regulations, 2014 CFR

2014-10-01

... at least 5 minutes at each outlet; and (2) In a space must have enough foam producing material to... or space, the system need have only enough foam producing material to cover the largest space that the system covers or, if the liquid surface of a tank covered by the system is larger, the tank with...

Activated, coal-based carbon foam

DOEpatents

Rogers, Darren Kenneth; Plucinski, Janusz Wladyslaw

2004-12-21

An ablation resistant, monolithic, activated, carbon foam produced by the activation of a coal-based carbon foam through the action of carbon dioxide, ozone or some similar oxidative agent that pits and/or partially oxidizes the carbon foam skeleton, thereby significantly increasing its overall surface area and concurrently increasing its filtering ability. Such activated carbon foams are suitable for application in virtually all areas where particulate or gel form activated carbon materials have been used. Such an activated carbon foam can be fabricated, i.e. sawed, machined and otherwise shaped to fit virtually any required filtering location by simple insertion and without the need for handling the "dirty" and friable particulate activated carbon foam materials of the prior art.

Ultralight metal foams

NASA Astrophysics Data System (ADS)

Jiang, Bin; He, Chunnian; Zhao, Naiqin; Nash, Philip; Shi, Chunsheng; Wang, Zejun

2015-09-01

Ultralight (<10 mg/cm3) cellular materials are desirable for thermal insulation; battery electrodes; catalyst supports; and acoustic, vibration, or shock energy damping. However, most of these ultralight materials, especially ultralight metal foams, are fabricated using either expensive materials or complicated procedures, which greatly limit their large-scale production and practical applications. Here we report a simple and versatile method to obtain ultralight monolithic metal foams. These materials are fabricated with a low-cost polymeric template and the method is based on the traditional silver mirror reaction and electroless plating. We have produced ultralight monolithic metal foams, such as silver, nickel, cobalt, and copper via this method. The resultant ultralight monolithic metal foams have remarkably low densities down to 7.4 mg/cm3 or 99.9% porosity. The metal foams have a long flat stress-train curve in compression tests and the densification strain ɛD of the Ni/Ag foam with a porosity of 99.8% can reach 82%. The plateau stress σpl was measured and found to be in agreement with the value predicted by the cellular solids theory.

Ultralight metal foams.

PubMed

Jiang, Bin; He, Chunnian; Zhao, Naiqin; Nash, Philip; Shi, Chunsheng; Wang, Zejun

2015-09-08

Ultralight (<10 mg/cm3) cellular materials are desirable for thermal insulation; battery electrodes; catalyst supports; and acoustic, vibration, or shock energy damping. However, most of these ultralight materials, especially ultralight metal foams, are fabricated using either expensive materials or complicated procedures, which greatly limit their large-scale production and practical applications. Here we report a simple and versatile method to obtain ultralight monolithic metal foams. These materials are fabricated with a low-cost polymeric template and the method is based on the traditional silver mirror reaction and electroless plating. We have produced ultralight monolithic metal foams, such as silver, nickel, cobalt, and copper via this method. The resultant ultralight monolithic metal foams have remarkably low densities down to 7.4 mg/cm3 or 99.9% porosity. The metal foams have a long flat stress-train curve in compression tests and the densification strain εD of the Ni/Ag foam with a porosity of 99.8% can reach 82%. The plateau stress σpl was measured and found to be in agreement with the value predicted by the cellular solids theory.

Dielectric properties of novel polyurethane-PZT-graphite foam composites

NASA Astrophysics Data System (ADS)

Tolvanen, Jarkko; Hannu, Jari; Nelo, Mikko; Juuti, Jari; Jantunen, Heli

2016-09-01

Flexible foam composite materials offer multiple benefits to future electronic applications as the rapid development of the electronics industry requires smaller, more efficient, and lighter materials to further develop foldable and wearable applications. The aims of this work were to examine the electrical properties of three- and four-phase novel foam composites in different conditions, find the optimal mixture for four-phase foam composites, and study the combined effects of lead zirconate titanate (PZT) and graphite fillers. The flexible and highly compressible foams were prepared in a room-temperature mixing process using polyurethane, PZT, and graphite components as well as their combinations, in which air acted as one phase. In three-phase foams the amount of PZT varied between 20 and 80 wt% and the amount of graphite, between 1 and 15 wt%. The four-phase foams were formed by adding 40 wt% of PZT while the amount of graphite ranged between 1 and 15 wt%. The presented results and materials could be utilized to develop new flexible and soft sensor applications by means of material technology.

Bonding and Sealing Evaluations for Cryogenic Tanks

NASA Technical Reports Server (NTRS)

Glass, David E.

1997-01-01

Several different cryogenic tank concepts are being considered for reusable launch vehicles (RLV'S) . Though different tank concepts are being considered, many will require that the cryogenic insulation be evacuated and be bonded to a structure. In this work, an attempt was made to evaluate the effectiveness of maintaining a vacuum on a specimen where foam or honeycomb core was encased within Gr/Ep. In addition to these tests, flatwise adhesion pull off tests were performed at room temperature with PR 1664, EA 9394, FM-300, Crest 3170, and HT 435 adhesives. The materials bonded included Gr/Ep, Gr/BMI, Al, and stainless steel facesheets, and Ti honeycomb, Hexcel honeycomb, and Rohacell foam core materials.

Hydrodynamics of wet foams

NASA Astrophysics Data System (ADS)

Langevin, Dominique; Saint-Jalmes, Arnaud; Marze, Sébastien; Cox, Simon; Hutzler, Stefan; Drenckhan, Wiebke; Weaire, Denis; Caps, Hervé; Vandewalle, Nicolas; Adler, Micheàle; Pitois, Olivier; Rouyer, Florence; Cohen-Addad, Sylvie; Höhler, Reinhard; Ritacco, Hernan

2005-10-01

Foams and foaming pose important questions and problems to the chemical industry. As a material, foam is unusual in being a desired product while also being an unwanted byproduct within industry. Liquid foams are an essential part of gas/liquid contacting processes such as distillation and absorption, but over-production of foam in these processes can lead to downtime and loss of efficiency. Solid polymeric foams, such as polystyrene and polyurethane, find applications as insulation panels in the construction industry. Their combination of low weight and unique elastic/plastic properties make them ideal as packing and cushioning materials. Foams made with proteins are extensively used in the food industry. Despite the fact that foam science is a rapidly maturing field, critical aspects of foam physics and chemistry remain unclear. Several gaps in knowledge were identified to be tackled as the core of this MAP project. In addition, microgravity affords conditions for extending our understanding far beyond the possibilities offered by ground-based investigation. This MAP project addresses the challenges posed by the physics of foams under microgravity.

3D Printing Variable Stiffness Foams Using Viscous Thread Instability

NASA Astrophysics Data System (ADS)

Lipton, Jeffrey I.; Lipson, Hod

2016-08-01

Additive manufacturing of cellular structures has numerous applications ranging from fabrication of biological scaffolds and medical implants, to mechanical weight reduction and control over mechanical properties. Various additive manufacturing processes have been used to produce open regular cellular structures limited only by the resolution of the printer. These efforts have focused on printing explicitly designed cells or explicitly planning offsets between strands. Here we describe a technique for producing cellular structures implicitly by inducing viscous thread instability when extruding material. This process allows us to produce complex cellular structures at a scale that is finer than the native resolution of the printer. We demonstrate tunable effective elastic modulus and density that span two orders of magnitude. Fine grained cellular structures allow for fabrication of foams for use in a wide range of fields ranging from bioengineering, to robotics to food printing.

Continuous Carbon Nanotube-Ultrathin Graphite Hybrid Foams for Increased Thermal Conductivity and Suppressed Subcooling in Composite Phase Change Materials.

PubMed

Kholmanov, Iskandar; Kim, Jaehyun; Ou, Eric; Ruoff, Rodney S; Shi, Li

2015-12-22

Continuous ultrathin graphite foams (UGFs) have been actively researched recently to obtain composite materials with increased thermal conductivities. However, the large pore size of these graphitic foams has resulted in large thermal resistance values for heat conduction from inside the pore to the high thermal conductivity graphitic struts. Here, we demonstrate that the effective thermal conductivity of these UGF composites can be increased further by growing long CNT networks directly from the graphite struts of UGFs into the pore space. When erythritol, a phase change material for thermal energy storage, is used to fill the pores of UGF-CNT hybrids, the thermal conductivity of the UGF-CNT/erythritol composite was found to increase by as much as a factor of 1.8 compared to that of a UGF/erythritol composite, whereas breaking the UGF-CNT bonding in the hybrid composite resulted in a drop in the effective room-temperature thermal conductivity from about 4.1 ± 0.3 W m(-1) K(-1) to about 2.9 ± 0.2 W m(-1) K(-1) for the same UGF and CNT loadings of about 1.8 and 0.8 wt %, respectively. Moreover, we discovered that the hybrid structure strongly suppresses subcooling of erythritol due to the heterogeneous nucleation of erythritol at interfaces with the graphitic structures.

Ultrasonic assessment of bonding integrity in foam-based hybrid composite materials

NASA Astrophysics Data System (ADS)

Chen, M. Y.; Ko, R. T.; Hoppe, W. C.; Blackshire, J. L.

2013-01-01

Ultrasonic assessment of the bonding integrity between a composite layer and a foam substrate in foam-based hybrid composite materials was explored. The challenges of this task are: (1) the foam has air-like acoustic impedance and (2) contact surface wave generation on polymer matrix composites (PMC) is not conventional. To meet these challenges, a novel wedge made of a low velocity material was developed. The results showed that the bonding condition in these composites can be identified by monitoring the amplitude of the ultrasonic signals received.

Fluid Physics of Foam Evolution and Flow

NASA Technical Reports Server (NTRS)

Aref, H.; Thoroddsen, S. T.; Sullivan, J. M.

2003-01-01

The grant supported theoretical, numerical and experimental work focused on the elucidation of the fluid physics of foam structure, evolution and flow. The experimental work concentrated on these subject areas: (a) Measurements of the speed of reconnections within a foam; (b) statistics of bubble rearrangements; and (c) three-dimensional reconstruction of the foam structure. On the numerical simulation and theory side our efforts concentrated on the subjects: (a) simulation techniques for 2D and 3D foams; (b) phase transition in a compressible foam; and (c) TCP structures.

A finite element/level set model of polyurethane foam expansion and polymerization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rao, Rekha R.; Long, Kevin Nicholas; Roberts, Christine Cardinal

Polyurethane foams are used widely for encapsulation and structural purposes because they are inexpensive, straightforward to process, amenable to a wide range of density variations (1 lb/ft3 - 50 lb/ft3), and able to fill complex molds quickly and effectively. Computational model of the filling and curing process are needed to reduce defects such as voids, out-of-specification density, density gradients, foam decomposition from high temperatures due to exotherms, and incomplete filling. This paper details the development of a computational fluid dynamics model of a moderate density PMDI structural foam, PMDI-10. PMDI is an isocyanate-based polyurethane foam, which is chemically blown withmore » water. The polyol reacts with isocyanate to produces the polymer. PMDI- 10 is catalyzed giving it a short pot life: it foams and polymerizes to a solid within 5 minutes during normal processing. To achieve a higher density, the foam is over-packed to twice or more of its free rise density of 10 lb/ft3. The goal for modeling is to represent the expansion, filling of molds, and the polymerization of the foam. This will be used to reduce defects, optimize the mold design, troubleshoot the processed, and predict the final foam properties. A homogenized continuum model foaming and curing was developed based on reaction kinetics, documented in a recent paper; it uses a simplified mathematical formalism that decouples these two reactions. The chemo-rheology of PMDI is measured experimentally and fit to a generalized- Newtonian viscosity model that is dependent on the extent of cure, gas fraction, and temperature. The conservation equations, including the equations of motion, an energy balance, and three rate equations are solved via a stabilized finite element method. The equations are combined with a level set method to determine the location of the foam-gas interface as it evolves to fill the mold. Understanding the thermal history and loads on the foam due to exothermicity and oven curing is very important to the results, since the kinetics, viscosity, and other material properties are all sensitive to temperature. Results from the model are compared to experimental flow visualization data and post-test X-ray computed tomography (CT) data for the density. Several geometries are investigated including two configurations of a mock structural part and a bar geometry to specifically test the density model. We have found that the model predicts both average density and filling profiles well. However, it under predicts density gradients, especially in the gravity direction. Further model improvements are also discussed for future work.« less

Foamability and structure analysis of foams in Hele-Shaw cell

NASA Astrophysics Data System (ADS)

Caps, H.; Vandewalle, N.; Broze, G.; Zocchi, G.

2007-05-01

The authors have generated two-dimensional foams by imposing an intermittent drainage in a Hele-Shaw cell partially filled with a detergent/water mixture. The foam generation associated with this process is reproducible and depends on the surfactant molecules composing the solution. A kinetic model can be proposed for the foam evolution. The structure of the foam is also investigated: the average bubble side number and correlation functions are measured. Distinguishable behaviors are observed for different surfactant molecules. This way of producing a foam is thus adequate for applied foam structure characterizations and fundamental studies.

Fully recoverable rigid shape memory foam based on copper-catalyzed azide-alkyne cycloaddition (CuAAC) using a salt leaching technique.

PubMed

Alzahrani, Abeer A; Saed, Mohand; Yakacki, Christopher M; Song, Han Byul; Sowan, Nancy; Walston, Joshua J; Shah, Parag K; McBride, Matthew K; Stansbury, Jeffrey W; Bowman, Christopher N

2018-01-07

This study is the first to employ the use of the copper-catalyzed azide-alkyne cycloaddition (CuAAC) polymerization to form a tough and stiff, porous material from a well-defined network possessing a high glass transition temperature. The effect of the network linkages formed as a product of the CuAAC reaction, i.e., the triazoles, on the mechanical behavior at high strain was evaluated by comparing the CuAAC foam to an epoxy-amine-based foam, which consisted of monomers with similar backbone structures and mechanical properties (i.e., T g of 115 °C and a rubbery modulus of 1.0 MPa for the CuAAC foam, T g of 125 °C and a rubbery modulus of 1.2 MPa for the epoxy-amine foam). When each foam was compressed uniformly to 80% strain at ambient temperature, the epoxy-amine foam was severely damaged after only reaching 70% strain in the first compression cycle with a toughness of 300 MJ/m 3 . In contrast, the CuAAC foam exhibited pronounced ductile behavior in the glassy state with three times higher toughness of 850 MJ/m 3 after the first cycle of compression to 80% strain. Additionally, when the CuAAC foam was heated above T g after each of five compression cycles to 80% strain at ambient temperature, the foam completely recovered its original shape while exhibiting a gradual decrease in mechanical performance over the multiple compression cycles. The foam demonstrated almost complete shape fixity and recovery ratios even through five successive cycles, indicative of "reversible plasticity", making it highly desirable as a glassy shape memory foams.

Biopolymer foams - Relationship between material characteristics and foaming behavior of cellulose based foams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rapp, F., E-mail: florian.rapp@ict.fraunhofer.de, E-mail: anja.schneider@ict.fraunhofer.de; Schneider, A., E-mail: florian.rapp@ict.fraunhofer.de, E-mail: anja.schneider@ict.fraunhofer.de; Elsner, P., E-mail: peter.elsner@ict.fraunhofer.de

2014-05-15

Biopolymers are becoming increasingly important to both industry and consumers. With regard to waste management, CO{sub 2} balance and the conservation of petrochemical resources, increasing efforts are being made to replace standard plastics with bio-based polymers. Nowadays biopolymers can be built for example of cellulose, lactic acid, starch, lignin or bio mass. The paper will present material properties of selected cellulose based polymers (cellulose propionate [CP], cellulose acetate butyrate [CAB]) and corresponding processing conditions for particle foams as well as characterization of produced parts. Special focus is given to the raw material properties by analyzing thermal behavior (differential scanning calorimetry),more » melt strength (Rheotens test) and molecular weight distribution (gel-permeation chromatography). These results will be correlated with the foaming behavior in a continuous extrusion process with physical blowing agents and underwater pelletizer. Process set-up regarding particle foam technology, including extrusion foaming and pre-foaming, will be shown. The characteristics of the resulting foam beads will be analyzed regarding part density, cell morphology and geometry. The molded parts will be tested on thermal conductivity as well as compression behavior (E-modulus, compression strength)« less

Brushite foams--the effect of Tween® 80 and Pluronic® F-127 on foam porosity and mechanical properties.

PubMed

Unosson, Johanna; Montufar, Edgar B; Engqvist, Håkan; Ginebra, Maria-Pau; Persson, Cecilia

2016-01-01

Resorbable calcium phosphate based bone void fillers should work as temporary templates for new bone formation. The incorporation of macropores with sizes of 100 -300 µm has been shown to increase the resorption rate of the implant and speed up bone ingrowth. In this work, macroporous brushite cements were fabricated through foaming of the cement paste, using two different synthetic surfactants, Tween® 80 and Pluronic® F-127. The macropores formed in the Pluronic samples were both smaller and less homogeneously distributed compared with the pores formed in the Tween samples. The porosity and compressive strength (CS) were comparable to previously developed hydroxyapatite foams. The cement foam containing Tween, 0.5M citric acid in the liquid, 1 mass% of disodium dihydrogen pyrophosphate mixed in the powder and a liquid to powder ratio of 0.43 mL/g, showed the highest porosity values (76% total and 56% macroporosity), while the CS was >1 MPa, that is, the hardened cement could be handled without rupture of the foamed structure. The investigated brushite foams show potential for future clinical use, both as bone void fillers and as scaffolds for in vitro bone regeneration. © 2015 The Authors. Journal of Biomedical Materials Research Part B: Applied Biomaterials Published by Wiley Periodicals, Inc.

Experimental investigation of solidification in metal foam enhanced phase change material

NASA Astrophysics Data System (ADS)

Beyne, W.; Bağci, O.; Huisseune, H.; Canière, H.; Danneels, J.; Daenens, D.; De Paepe, M.

2017-10-01

A major challenge for the use of phase change materials (PCMs) in thermal energy storage (TES) is overcoming the low thermal conductivity of PCM’s. The low conductivity gives rise to limited power during charging and discharging TES. Impregnating metal foam with PCM, however, has been found to enhance the heat transfer. On the other hand, the effect of foam parameters such as porosity, pore size and material type has remained unclear. In this paper, the effect of these foam parameters on the solidification time is investigated. Different samples of PCM-impregnated metal foam were experimentally tested and compared to one without metal foam. The samples varied with respect to choice of material, porosity and pore size. They were placed in a rectangular cavity and cooled from one side using a coolant flowing through a cold plate. The other sides of the rectangular cavity were Polymethyl Methacrylate (PM) walls exposed to ambient. The temperature on the exterior walls of the cavity was monitored as well as the coolant flow rate and its temperature. The metal foam inserts reduced the solidification times by at least 25 %. However, the difference between the best performing and worst performing metal foam is about 28 %. This shows a large potential for future research.

Material Characterization and Computer Model Simulation of Low Density Polyurethane Foam Used in a Rodent Traumatic Brain Injury Model

PubMed Central

Zhang, Liying; Gurao, Manish; Yang, King H.; King, Albert I.

2011-01-01

Computer models of the head can be used to simulate the events associated with traumatic brain injury (TBI) and quantify biomechanical response within the brain. Marmarou’s impact acceleration rodent model is a widely used experimental model of TBI mirroring axonal pathology in humans. The mechanical properties of the low density polyurethane (PU) foam, an essential piece of energy management used in Marmarou’s impact device, has not been fully characterized. The foam used in Marmarou’s device was tested at seven strain rates ranging from quasi-static to dynamic (0.014 ~ 42.86 s−1) to quantify the stress-strain relationships in compression. Recovery rate of the foam after cyclic compression was also determined through the periods of recovery up to three weeks. The experimentally determined stress-strain curves were incorporated into a material model in an explicit Finite Element (FE) solver to validate the strain rate dependency of the FE foam model. Compression test results have shown that the foam used in the rodent impact acceleration model is strain rate dependent. The foam has been found to be reusable for multiple impacts. However the stress resistance of used foam is reduced to 70% of the new foam. The FU_CHANG_FOAM material model in an FE solver has been found to be adequate to simulate this rate sensitive foam. PMID:21459114

Material characterization and computer model simulation of low density polyurethane foam used in a rodent traumatic brain injury model.

PubMed

Zhang, Liying; Gurao, Manish; Yang, King H; King, Albert I

2011-05-15

Computer models of the head can be used to simulate the events associated with traumatic brain injury (TBI) and quantify biomechanical response within the brain. Marmarou's impact acceleration rodent model is a widely used experimental model of TBI mirroring axonal pathology in humans. The mechanical properties of the low density polyurethane (PU) foam, an essential piece of energy management used in Marmarou's impact device, has not been fully characterized. The foam used in Marmarou's device was tested at seven strain rates ranging from quasi-static to dynamic (0.014-42.86 s⁻¹) to quantify the stress-strain relationships in compression. Recovery rate of the foam after cyclic compression was also determined through the periods of recovery up to three weeks. The experimentally determined stress-strain curves were incorporated into a material model in an explicit Finite Element (FE) solver to validate the strain rate dependency of the FE foam model. Compression test results have shown that the foam used in the rodent impact acceleration model is strain rate dependent. The foam has been found to be reusable for multiple impacts. However the stress resistance of used foam is reduced to 70% of the new foam. The FU_CHANG_FOAM material model in an FE solver has been found to be adequate to simulate this rate sensitive foam. Copyright © 2011 Elsevier B.V. All rights reserved.

Effect of Porosity on the Properties of Open Cell Titanium Foams Intended for Orthopedic Applications

NASA Astrophysics Data System (ADS)

Lefebvre, L. P.; Baril, E.

2010-05-01

Porous metals have been used in various orthopedic applications as coating to promote implant fixation or as scaffolds for bone reconstruction. Since these materials were up to recently only used as thin coating (i.e. sintered beads or mesh) and not available into shapes adequate for detailed characterization, the effect of the structure on the static and dynamic properties of these materials has not been widely reported in the literature. This paper presents the effect of the porosity (49.3-66.7%) on the static and dynamic properties of titanium foams produced with a powder metallurgy process. All materials exhibited compression curves with three stages, typical of ductile porous materials. When the porosity level increases, the materials become more brittle. The compression yield strength increases while the modulus is more or less unaffected when the porosity increases from 49.3 to 66.7% and does not follow the power law model accepted for porous medium. The shear strength/adhesion with dense substrates increases with density and is proportional to the compression yield strength. The fatigue limit is not directly link with the porosity. The discrepancies observed are attributed to differences in the structure as the porosity increases.

Indentability of conventional and negative Poisson's ratio foams

NASA Technical Reports Server (NTRS)

Lakes, R. S.; Elms, K.

1992-01-01

The indentation resistance of foams, both of conventional structure and of reentrant structure giving rise to negative Poisson's ratio, is studied using holographic interferometry. In holographic indentation tests, reentrant foams had higher yield strength and lower stiffness than conventional foams of the same original relative density. Calculated energy absorption for dynamic impact is considerably higher for reentrant foam than conventional foam.

Healing efficiency of shape memory polyurethane fiber reinforced syntactic foam under applied load

NASA Astrophysics Data System (ADS)

Ogunmekan, Babatunde

Shape memory composite materials have received a great deal of interest in recent structural developments, both in sandwich and in lightweight structures. Experimental procedures involving the free body healing of these materials have been carried out; however, it is important to investigate the healing behaviors of these SMP materials while under load. In this study, syntactic foams reinforced with strain-hardened short-shape memory polyurethane fibers (SMPUFs) were prepared to evaluate their ability to heal wide-opened cracks using the two-step biomimetic close-then-heal (CTH) self-healing scheme while under varying loads. The syntactic foam samples manufactured consisted of an epoxy matrix with dispersed thermoplastic particles, glass microballoons and short SMPUFs. The SMPUF strands were cold-drawn (stretched-then-released) for up to four cycles and then cut to 10 mm short fibers before casting the polymer matrix. Three types of syntactic foam specimens, consisting of 5%, 10%, and 15% thermoplastic particle volume fraction compositions, respectively, were manufactured, and notched beam samples were then prepared. Fracture-healing by uniaxial tension was conducted for five cycles on each sample. Material characterization techniques, such as scanning electron microscopy (SEM) and differential scanning calorimetry (DSC), were utilized to highlight the crack healing characteristics and thermal properties. In addition, a high-resolution charge-coupled device (CCD) camera with a resolution of 3.7 x 3.7 μm/pixel was used to capture the crack tip opening displacement (CTOD). It is seen that the healing ability of the composite varies with changes in both the load carried and the volume fraction of thermoplastic particles. As the thermoplastic volume fraction increased from 5% to 10% to 15%, the tensile strength values recorded decreased, but there was also an increase in the healing efficiency. Moreover, SEM images revealed partial healing in samples with lower thermoplastic particle contents.

46 CFR 164.015-5 - Procedure for acceptance.

Code of Federal Regulations, 2010 CFR

2010-10-01

...: SPECIFICATIONS AND APPROVAL MATERIALS Plastic Foam, Unicellular, Buoyant, Sheet and Molded Shape § 164.015-5 Procedure for acceptance. (a) Unicellular plastic foam is not subject to formal approval, but will be... manufacturing methods and to select from foam already manufactured sufficient sample material for testing for...

46 CFR 164.013-6 - Production tests, inspections, and marking.

Code of Federal Regulations, 2011 CFR

2011-10-01

..., CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL MATERIALS Foam, Unicellular Polyethylene (Buoyant... shall provide in-plant quality control of polyethylene foam in accordance with the requirements of § 164.019-13 and any requirements of the recognized laboratory. The manufacturer of the foam has primary...

46 CFR 164.013-6 - Production tests, inspections, and marking.

Code of Federal Regulations, 2010 CFR

2010-10-01

..., CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL MATERIALS Foam, Unicellular Polyethylene (Buoyant... shall provide in-plant quality control of polyethylene foam in accordance with the requirements of § 164.019-13 and any requirements of the recognized laboratory. The manufacturer of the foam has primary...

Atomic Layer Deposition on Carbon Nanotubes and their Assemblies

NASA Astrophysics Data System (ADS)

Stano, Kelly Lynn

Global issues related to energy and the environment have motivated development of advanced material solutions outside of traditional metals ceramics, and polymers. Taking inspiration from composites, where the combination of two or more materials often yields superior properties, the field of organic-inorganic hybrids has recently emerged. Carbon nanotube (CNT)-inorganic hybrids have drawn widespread and increasing interest in recent years due to their multifunctionality and potential impact across several technologically important application areas. Before the impacts of CNT-inorganic hybrids can be realized however, processing techniques must be developed for their scalable production. Optimization in chemical vapor deposition (CVD) methods for synthesis of CNTs and vertically aligned CNT arrays has created production routes both high throughput and economically feasible. Additionally, control of CVD parameters has allowed for growth of CNT arrays that are able to be drawn into aligned sheets and further processed to form a variety of aligned 1, 2, and 3-dimensional bulk assemblies including ribbons, yarns, and foams. To date, there have only been a few studies on utilizing these bulk assemblies for the production of CNT-inorganic hybrids. Wet chemical methods traditionally used for fabricating CNT-inorganic hybrids are largely incompatible with CNT assemblies, since wetting and drying the delicate structures with solvents can destroy their structure. It is therefore necessary to investigate alternative processing strategies in order to advance the field of CNT-inorganic hybrids. In this dissertation, atomic layer deposition (ALD) is evaluated as a synthetic route for the production of large-scale CNT-metal oxide hybrids as well as pure metal oxide architectures utilizing CNT arrays, ribbons, and ultralow density foams as deposition templates. Nucleation and growth behavior of alumina was evaluated as a function of CNT surface chemistry. While highly graphitic and defect-free CNTs were shown to produce alumina beads on their surfaces, plasma-treated CNTs with a high concentration of oxygen- containing functional groups on their surface promoted conformal film formation. Furthermore, it was determined that ultrahigh aspect ratio CNT assemblies could be uniformly coated throughout the cross-section by orienting the CNT axes parallel to the direction of precursor flow, as well as by removing any barriers to the pump/purge process such as growth substrates or non-porous sample holders. Heat treatment of CNT-alumina hybrids in air not only led to the crystallization of alumina, but also oxidative removal of CNTs from the core-shell structure. In the case of CNT arrays, this resulted in a weak array of alumina nanotubes. When the same process was applied to alumina-coated CNT foams (CNTFs) however, a robust and resilient aerogel-like material remained post-calcination. Further inspection of this novel material revealed that the foam was made up of a three-dimensional network of interconnect alumina nanotubes resulting from the direct templating of alumina on the CNTF structure. With an average density of 1.2 mg cm-3, it is an order of magnitude lower than the lowest density alumina aerogel reported to date, and is among the lowest density for any inorganic aerogel reported to date as well. The structure, and therefore, properties of these novel foams could be easily tuned by varying the thickness of the alumina coating. Evaluation of the compressive behavior of all foams revealed that their mechanical properties exceed those of various foams with similar densities. This was found to be a result of efficient load transfer through the structure due to good connectivity among nanotube ligaments. This connectivity also provided unprecedented elastic recoverability following compression, particularly for thin-walled samples with CNTFs still intact. Structural stability to liquid infiltration and drying increased with the number of ALD cycles, as well as thermal insulation ability.

Implications of interfacial characteristics of food foaming agents in foam formulations.

PubMed

Rodríguez Patino, Juan M; Carrera Sánchez, Cecilio; Rodríguez Niño, Ma Rosario

2008-08-05

The manufacture of food dispersions (emulsions and foams) with specific quality attributes depends on the selection of the most appropriate raw materials and processing conditions. These dispersions being thermodynamically unstable require the use of emulsifiers (proteins, lipids, phospholipids, surfactants etc.). Emulsifiers typically coexist in the interfacial layer with specific functions in the processing and properties of the final product. The optimum use of emulsifiers depends on our knowledge of their interfacial physico-chemical characteristics - such as surface activity, amount adsorbed, structure, thickness, topography, ability to desorb (stability), lateral mobility, interactions between adsorbed molecules, ability to change conformation, interfacial rheological properties, etc. -, the kinetics of film formation and other associated physico-chemical properties at fluid interfaces. These monolayers constitute well defined systems for the analysis of food colloids at the micro- and nano-scale level, with several advantages for fundamental studies. In the present review we are concerned with the analysis of physico-chemical properties of emulsifier films at fluid interfaces in relation to foaming. Information about the above properties would be very helpful in the prediction of optimised formulations for food foams. We concluded that at surface pressures lower than that of monolayer saturation the foaming capacity is low, or even zero. A close relationship was observed between foaming capacity and the rate of diffusion of the foaming agent to the air-water interface. However, the foam stability correlates with the properties of the film at long-term adsorption.

Constitutive modeling of aluminum foam and finite element implementation for crash simulations

NASA Astrophysics Data System (ADS)

Bi, Jing

In the past decades metallic foams have been increasingly used as filler materials in crashworthiness applications due to their relatively low cost and high capacity of energy absorption. Due to the destructive nature of crashes, studies on the performance of metallic foams using physical testing have been limited to examining the crushing force histories and/or folding patterns that are insufficient for crashworthiness designs. For this reason, numerical simulations, particularly nonlinear finite element (FE) analyses, play an important role in designing crashworthy foam-filled structures. An effective and numerically stable model is needed for modeling metallic foams that are porous and encounter large nonlinear deformations in crashes. In this study a new constitutive model for metallic foams is developed to overcome the deficiency of existing models in commercial FE codes such as LS-DYNA. The new constitutive model accounts for volume changes under hydrostatic compression and combines the hydrostatic pressure and von Mises stress into one yield function. The change of the compressibility of the metallic foam is handled in the constitutive model by allowing for shape changes of the yield surface in the hydrostatic pressure-von Mises stress space. The backward Euler method is adopted to integrate the constitutive equations to achieve numerical accuracy and stability. The new foam model is verified and validated by existing experimental data before used in FE simulations of crushing of foam-filled columns that have square and hexagonal cross-sections.

A water blown urethane insulation for use in cryogenic environments

NASA Technical Reports Server (NTRS)

Blevins, Elana; Sharpe, Jon

1995-01-01

Thermal Protection Systems (TPS) of NASA's Space Shuttle External Tank include polyurethane and polyisocyanurate modified polyurethane foam insulations. These insulations, currently foamed with CFC 11 blowing agent, serve to maintain cryogenic propellant quality, maintain the external tank structural temperature limits, and minimize the formation of ice and frost that could potentially damage the ceramic insulation on the space shuttle orbiter. During flight the external tank insulations are exposed to mechanical, thermal and acoustical stresses. TPS must pass cryogenic flexure and substrate adhesion tests at -253 C, aerothermal and radiant heating tests at fluxes up to approximately 14 kilowatts per square meter, and thermal conductivity tests at cryogenic and elevated temperatures. Due to environmental concerns, the polyurethane insulation industry and the External Tank Project are tasked with replacing CFC 11. The flight qualification of foam insulations employing HCFC 141b as a foaming agent is currently in progress; HCFC 141b blown insulations are scheduled for production implementation in 1995. Realizing that the second generation HCFC blowing agents are an interim solution, the evaluation of third generation blowing agents with zero ozone depletion potential is underway. NASA's TPS Materials Research Laboratory is evaluating third generation blowing agents in cryogenic insulations for the External Tank; one option being investigated is the use of water as a foaming agent. A dimensionally stable insulation with low friability, good adhesion to cryogenic substrates, and acceptable thermal conductivity has been developed with low viscosity materials that are easily processed in molding applications. The development criteria, statistical experimental approach, and resulting foam properties will be presented.

Continuous microcellular foaming of polylactic acid/natural fiber composites

NASA Astrophysics Data System (ADS)

Diaz-Acosta, Carlos A.

Poly(lactic acid) (PLA), a biodegradable thermoplastic derived from renewable resources, stands out as a substitute to petroleum-based plastics. In spite of its excellent properties, commercial applications are limited because PLA is more expensive and more brittle than traditional petroleum-based resins. PLA can be blended with cellulosic fibers to reduce material cost. However, the lowered cost comes at the expense of flexibility and impact strength, which can be enhanced through the production of microcellular structures in the composite. Microcellular foaming uses inert gases (e.g., carbon dioxide) as physical blowing agents to make cellular structures with bubble sizes of less than 10 microm and cell-population densities (number of bubbles per unit volume) greater than 109 cells/cm³. These unique characteristics result in a significant increase in toughness and elongation at break (ductility) compared with unfoamed parts because the presence of small bubbles can blunt the crack-tips increasing the energy needed to propagate the crack. Microcellular foams have been produced through a two step batch process. First, large amounts of gas are dissolved in the solid plastic under high pressure (sorption process) to form a single-phase solution. Second, a thermodynamic instability (sudden drop in solubility) triggers cell nucleation and growth as the gas diffuses out of the plastic. Batch production of microcellular PLA has addressed some of the drawbacks of PLA. Unfortunately, the batch foaming process is not likely to be implemented in the industrial production of foams because it is not cost-effective. This study investigated the continuous microcellular foaming process of PLA and PLA/wood-fiber composites. The effects of the processing temperature and material compositions on the melt viscosity, pressure drop rate, and cell-population density were examined in order to understand the nucleation mechanisms in neat and filled PLA foams. The results indicated that the processing temperature had a strong effect of the rheology of the melt and cell morphology. Processing at a lower temperature significantly increased the cell nucleation rate of neat PLA (amorphous and semi-crystalline) because of the fact that a high melt viscosity induced a high pressure drop rate in the polymer/gas solution. The presence of nanoclay did not affect the homogeneous nucleation but increased the heterogeneous nucleation, allowing both nucleation mechanisms to occur during the foaming process. The effect of wood-flour (0-30 wt.%) and rheology modifier contents on the melt viscosity and cell morphology of microcellular foamed composites was investigated. The viscosity of the melt increased with wood-flour content and decreased with rheology modifier content, affecting the processing conditions (i.e., pressure drop and pressure drop rate) and foamability of the composites. Matching the viscosity of the composites with that of neat PLA resulted in the best cell morphologies. Physico-mechanical characterization of microcellular foamed PLA as a function of cell morphology was performed to establish process-morphology-property relationships. The processing variables, i.e., amount of gas injected, flow rate, and processing temperature affected the development of the cellular structure and mechanical properties of the foams.

The Influence of Clocking Angle of the Projectile on the Simulated Impact Response of a Shuttle Leading Edge Wing Panel

NASA Technical Reports Server (NTRS)

Jackson, Karen E.; Fasanella, Edwin L.; Lyle, Karen H.; Spellman, Regina L.

2005-01-01

An analytical study was conducted to determine the influence of clocking angle of a foam projectile impacting a space shuttle leading edge wing panel. Four simulations were performed using LS-DYNA. The leading edge panels are fabricated of multiple layers of reinforced carbon-carbon (RCC) material. The RCC material was represented using Mat 58, which is a material property that can be used for laminated composite fabrics. Simulations were performed of a rectangular-shaped foam block, weighing 0.23-lb., impacting RCC Panel 9 on the top surface. The material properties of the foam were input using Mat 83. The impact velocity was 1,000 ft/s along the Orbiter X-axis. In two models, the foam impacted on a corner, in one model the foam impacted the panel initially on the 2-in.-long edge, and in the last model the foam impacted the panel on the 7-in.- long edge. The simulation results are presented as contour plots of first principal infinitesimal strain and time history plots of contact force and internal and kinetic energy of the foam and RCC panel.

Development of a Hopkinson Bar Apparatus for Testing Soft Materials: Application to a Closed-Cell Aluminum Foam.

PubMed

Peroni, Marco; Solomos, George; Babcsan, Norbert

2016-01-05

An increasing interest in lightweight metallic foams for automotive, aerospace, and other applications has been observed in recent years. This is mainly due to the weight reduction that can be achieved using foams and for their mechanical energy absorption and acoustic damping capabilities. An accurate knowledge of the mechanical behavior of these materials, especially under dynamic loadings, is thus necessary. Unfortunately, metal foams and in general "soft" materials exhibit a series of peculiarities that make difficult the adoption of standard testing techniques for their high strain-rate characterization. This paper presents an innovative apparatus, where high strain-rate tests of metal foams or other soft materials can be performed by exploiting the operating principle of the Hopkinson bar methods. Using the pre-stress method to generate directly a long compression pulse (compared with traditional SHPB), a displacement of about 20 mm can be applied to the specimen with a single propagating wave, suitable for evaluating the whole stress-strain curve of medium-sized cell foams (pores of about 1-2 mm). The potential of this testing rig is shown in the characterization of a closed-cell aluminum foam, where all the above features are amply demonstrated.

Enabling In-Theater Processes for Indigenous, Recycled, and Reclaimed Material Manufacturing

DTIC Science & Technology

2015-12-01

compression testing was accomplished on this material alone, as well as infused aluminum foam . The LTS-infused aluminum foam showed an interesting...protection against blast threats. 15. SUBJECT TERMS indigenous manufacturing, concrete alternatives, nondestructive evaluation, metallic foam testing...of Blocks on a FOB: CO2 Supply 11 6.7 Metallic Foam Infiltration with LTS Ceramic 12 6.8 LTS Ceramic Made with Gasified Char 21 6.9 Micro Auto

Experimental Evaluation of Equivalent-Fluid Models for Melamine Foam

NASA Technical Reports Server (NTRS)

Allen, Albert R.; Schiller, Noah H.

2016-01-01

Melamine foam is a soft porous material commonly used in noise control applications. Many models exist to represent porous materials at various levels of fidelity. This work focuses on rigid frame equivalent fluid models, which represent the foam as a fluid with a complex speed of sound and density. There are several empirical models available to determine these frequency dependent parameters based on an estimate of the material flow resistivity. Alternatively, these properties can be experimentally educed using an impedance tube setup. Since vibroacoustic models are generally sensitive to these properties, this paper assesses the accuracy of several empirical models relative to impedance tube measurements collected with melamine foam samples. Diffuse field sound absorption measurements collected using large test articles in a laboratory are also compared with absorption predictions determined using model-based and measured foam properties. Melamine foam slabs of various thicknesses are considered.

Structural Continuum Modeling of Space Shuttle External Tank Foam Insulation

NASA Technical Reports Server (NTRS)

Steeve, Brian; Ayala, Sam; Purlee, T. Eric; Shaw, Phillip

2006-01-01

This document is a viewgraph presentation reporting on work in modeling the foam insulation of the Space Shuttle External Tank. An analytical understanding of foam mechanics is required to design against structural failure. The Space Shuttle External Tank is covered primarily with closed cell foam to: Prevent ice, Protect structure from ascent aerodynamic and engine plume heating, and Delay break-up during re-entry. It is important that the foam does not shed unacceptable debris during ascent environment. Therefore a modeling of the foam insulation was undertaken.

Flame Resistant Foam

NASA Technical Reports Server (NTRS)

1984-01-01

Solimide manufactured by Imi-Tech Corporation, is a lightweight fire resistant material produced under a manufacturing process that allows it to be uniformly foamed. Can be produced in a variety of densities and structural configurations and remains resilient under exposure to temperatures ranging from minus 300 to plus 500 degrees Fahrenheit. Is resistant to open flame and generates virtually no smoke or toxic by-products. Used in aircraft for its superior damping characteristics, lighter weight and fire barrier properties, it's also applicable to ships and surface transportation systems such as transit cars, trains, buses and automobiles.

Bacteria-Affinity 3D Macroporous Graphene/MWCNTs/Fe3O4 Foams for High-Performance Microbial Fuel Cells.

PubMed

Song, Rong-Bin; Zhao, Cui-E; Jiang, Li-Ping; Abdel-Halim, Essam Sayed; Zhang, Jian-Rong; Zhu, Jun-Jie

2016-06-29

Promoting the performance of microbial fuel cells (MFCs) relies heavily on the structure design and composition tailoring of electrode materials. In this work, three-dimensional (3D) macroporous graphene foams incorporated with intercalated spacer of multiwalled carbon nanotubes (MWCNTs) and bacterial anchor of Fe3O4 nanospheres (named as G/MWCNTs/Fe3O4 foams) were first synthesized and used as anodes for Shewanella-inoculated microbial fuel cells (MFCs). Thanks to the macroporous structure of 3D graphene foams, the expanded electrode surface by MWCNTs spacing, as well as the high affinity of Fe3O4 nanospheres toward Shewanella oneidensis MR-1, the anode exhibited high bacterial loading capability. In addition to spacing graphene nanosheets for accommodating bacterial cells, MWCNTs paved a smoother way for electron transport in the electrode substrate of MFCs. Meanwhile, the embedded bioaffinity Fe3O4 nanospheres capable of preserving the bacterial metabolic activity provided guarantee for the long-term durability of the MFCs. With these merits, the constructed MFC possessed significantly higher power output and stronger stability than that with conventional graphite rod anode.

Experimental and simulation of split semi-torus key in PVC foam core to improve the debonding resistance of composite sandwich panel

NASA Astrophysics Data System (ADS)

Juliyana, M.; Santhana Krishnan, R.

2018-02-01

The sandwich composite panels consisting of facesheet and core material are used as a primary structural member for aerospace, civil and marine areas due to its high stiffness to weight ratio. But the debonding nature of facesheet from the foam core under shear loading conditions leads to failure of the composite structure. To inhibit the debonding, an innovative methodology of introducing semi-torus key is used in the present study. The polyvinyl chloride foam core(PVC) is grooved and filled with semi-torus shaped chopped strand prepregs which are sandwiched between alternate layers of woven roven(WR) and chopped strand mat(CSM) skins by vacuum infusion process. The sandwich panel manufactured with semi-torus keys is evaluated regarding experimental and numerical simulations under shear loading conditions. The present innovative concept delays the debonding between face-sheet and foam core with enhancement the shear load carrying capability as the initial stiffness is higher than the conventional model. Also, the shear behaviour of the proposed concept is in good agreement with experimental results. The split semi-torus keys sustain the shear failure resulting in resistance to debonding capability.

Chemical composition and surfactant characteristics of marine foams investigated by means of UV-vis, FTIR and FTNIR spectroscopy.

PubMed

Mecozzi, Mauro; Pietroletti, Marco

2016-11-01

In this study, we collected the ultraviolet-visible (UV-vis), Fourier transform infrared (FTIR) and Fourier transform near-infrared (FTNIR) spectra of marine foams from different sites and foams produced by marine living organisms (i.e. algae and molluscs) to retrieve information about their molecular and structural composition. UV-vis spectra gave information concerning the lipid and pigment contents of foams. FTIR spectroscopy gave a more detailed qualitative information regarding carbohydrates, lipids and proteins in addition with information about the mineral contents of foams. FTNIR spectra confirmed the presence of carbohydrates, lipids and proteins in foams. Then, due to the higher content of structural information of FTIR spectroscopy with respect to FTNIR and UV-vis, we join the FTIR spectra of marine foams to those of humic substance from marine sediments and to the spectra of foams obtained by living organisms. We submitted this resulting FTIR spectral dataset to statistical multivariate methods to investigate specific aspects of foams such as structural similarity among foams and in addition, contributions from the organic matter of living organisms. Cluster analysis (CA) evidenced several cases (i.e. clusters) of marine foams having high structural similarity with foams from vegetal and animal samples and with humic substance extracted from sediments. These results suggested that all the living organisms of the marine environment can give contributions to the chemical composition of foams. Moreover, as CA also evidenced cases of structural differences within foam samples, we applied two-dimensional correlation analysis (2DCORR) to the FTIR spectra of marine foams to investigate the molecular characteristics which caused these structural differences. Asynchronous spectra of two-dimensional correlation analysis showed that the structural heterogeneity among foam samples depended reasonably on the presence and on the qualitative difference of electrostatic (hydrogen bonds) and nonpolar (van der Waals and π-π) interactions involving carbohydrate proteins and lipids present. The presence and relevance of these interactions agree with the supramolecular and surfactant characteristics of marine organic matter described in the scientific literature.

Experiments and Models for Polymeric Microsphere Foams

NASA Technical Reports Server (NTRS)

Pipes, R. Byrona; Kyu, Thein

2005-01-01

The current project was performed under the direction of Dr. Byron Pipes as its lead investigator from January 2001 to August 2004. With the permission of the NASA, the project was transferred to Dr. Thein Kyu as the principle investigator for the period of September 2004 - June 2005. There were two major thrust areas in the original proposal; (1) experimental characterization and kinematics of foam structure formation and (2) determination of the mechanical, physical, and thermal properties, although these thrust areas were further sub- divided into 7 tasks. The present project has been directed primarily to elucidate kinematics of micro-foam formation (tasks 1 and 3) and to characterize micro-foam structures, since the control of the micro-structure of these foams is of paramount importance in determining their physical, mechanical and thermal properties. The first thrust area was accomplished in a timely manner; however, the second thrust area of foam properties (tasks 2,4-7) has yet to be completed because the area of kinematics of foam structure formation turned out to be extremely complex and thus consumed more time than what have been anticipated. As will be reported in what follows, the present studies have greatly enhances the in-depth understanding of mechanisms and kinematics of the micro-foam formation from solid powders. However, in order to implement all objectives of the second thrust areas regarding investigations of mechanical, physical, and thermal properties and establishment of the correlation of structure - properties of the foams, the project needs additional time and resources. The technical highlights of the accomplishment are summarized as follows. The present study represents a first approach to understanding the complexities that act together in the powder foaming process to achieve the successful inflation of polyimide microstructures. This type of study is novel as no prior work had dissected the fundamentals that govern the inflation process in this type of systems. The systematic approach to each of the different phenomena (i.e. morphological, diffusive, kinetic and dynamic) brings into context each of them in a way that allows separate understanding and analysis. Of the different phenomena studied, probably the one that gives a higher level of control over the inflation process has been shown to be the morphological aspects of the precursor particles. It is a major contribution of the present work to isolate and identify this phenomenon and highlight the features that with careful control during the synthesis of the precursor material can lead to a highly optimized and specialized final product (neat foam or microstructure). Some of these accomplishments have been presented in various national meetings and some of which are either published in refereed journals or still in various stages of publications. One of the presentations was selected for "Best of ANTEC 2004" Online Presentation Series of the Society of Plastics Engineers (SPE) (September 2004)

A sticky situation: management of spray polyurethane foam insulation in body orifices.

PubMed

Sowerby, Robert J; Sowerby, Leigh J; Vinden, Chris

2011-11-01

Spray polyurethane foam insulation is commonly used in the construction industry to fill gaps, seal, and insulate. We present three cases of intentional spray foam insertion in body orifices and discuss the management of such situations in the emergency department. This series includes a case of oral foam insertion used in a suicide attempt by suffocation and two cases of rectal insertion. All of these cases had potential long-term consequences; one was life-threatening. To our knowledge, this is the first published report on the medical management and removal of foam insulation from body orifices. In all three cases, the foam insulation material was successfully removed after allowing the material to harden.

Development of metal organic fromwork-199 immobilized zeolite foam for adsorption of common indoor VOCs.

PubMed

Saini, Vipin K; Pires, João

2017-05-01

Reticulated foam shaped adsorbents are more efficient for the removal of volatile organic compounds (VOCs), particularly from low VOC-concentration indoor air streams. In this study composite structure of zeolite and metal organic frameworks (MOFs), referred as ZMF, has been fabricated by immobilization of fine MOF-199 powder on foam shaped Zeolite Socony Mobil-5 (ZSM-5) Zeolitic structure, referred as ZF. The ZMF possess a uniform and well-dispersed coating of MOF-199 on the porous framework of ZF. It shows higher surface area, pore volume, and VOCs adsorption capacity, as compared to ZF-structure. Post-fabrication changes in selective adsorption properties of ZMF were studied with three common indoor VOCs (benzene, n-hexane, and cyclohexane), using gravimetric adsorption technique. The adsorption capacity of ZMF with different VOCs follow the order of benzene>n-hexane>cyclohexane. In comparison with MOF-199 and ZF, the composite structure ZMF shows improvement in selectivity for benzene from other two VOCs. Further, improvement in efficiency and stability of prepared ZMF was found to be associated with its high MOF loading capacity and unique morphological and structural properties. The developed composite structure with improved VOCs removal and recyclability could be a promising material for small to limited scale air pollution treatment units. Copyright © 2016. Published by Elsevier B.V.

Initial Evaluation of Burn Characteristics of Phenolic Foam Runway Brake Arrestor Material

DTIC Science & Technology

1993-12-01

foam immersed in a jet fuel fire when extinguished using 3-percent Aqueous Film Forming Foam ( AFFF ). Three pool...extinguishment time of phenolic foam immersed in a jet fuel fire, using 3-percent Aqueous Film Forming Foam ( AFFF ) extinguishing agent. The wind was negligible...percent Aqueous Film Forming Foam ( AFFF ) agent. This project is an initial assessment of the fire safety of phenolic foam

Fire and ecotoxicological aspects of polyurethane rigid foam.

PubMed

Wittbecker, F W; Giersig, M

2001-01-01

The main characteristics of fire effluents from polyurethane (PUR) foams are comparable to those from natural materials like wood, cork, or wool. This similarity has been demonstrated by comparative data from analytical and toxicological studies. It is therefore presumed that effluents of these materials present similar hazards to human beings and the environment. In almost all fires, dioxins can be found in the smoke and residues. In fires involving PURs, relevant quantities of halogenated dioxins or furans are not to be expected; this has been confirmed by investigations under controlled laboratory conditions. The insulation properties of rigid PUR foam contribute significantly to environmental protection and the conservation of resources. A number of methods for reusing and recycling PUR rigid foam waste have been developed and realized in practise. The possibilities range from reusing the material itself, generating liquid raw materials, and thermal recycling, even for (H)CFC-containing PUR rigid foams, by cocombustion in suitable plants.

Nano-fibrillated cellulose-hydroxyapatite based composite foams with excellent fire resistance.

PubMed

Guo, Wenwen; Wang, Xin; Zhang, Ping; Liu, Jiajia; Song, Lei; Hu, Yuan

2018-09-01

Thermally insulating materials made from renewable resources are desirable for energy efficient buildings. Traditional petroleum-derived insulating materials such as rigid polyurethane foam and expanded polystyrene display poor flame retardancy and inorganic insulating materials such as silica aerogel are fragile. Herein, we reported a facile approach to prepare cellulose nanofiber (CNF)-hydroxyapatite (HAP) composite foam by a simple freeze-drying process. The resultant HAP-CNF composite foams showed a thermal conductivity in the range of 38.5-39.1 mW/(m K) and very low peak heat release rate (20.4 kW/m 2 ) and total heat release (1.21 MJ/m 2 ). Vertical burning tests also manifested excellent fire resistance and self-extinguishing behaviours. Considering the excellent fire resistance of this composite foam, it is of significance to fire safety solution for buildings insulating materials. Copyright © 2018 Elsevier Ltd. All rights reserved.

Natural cork agglomerate employed as an environmentally friendly solution for quiet sandwich composites.

PubMed

Sargianis, James; Kim, Hyung-ick; Suhr, Jonghwan

2012-01-01

Carbon fiber-synthetic foam core sandwich composites are widely used for many structural applications due to their superior mechanical performance and low weight. Unfortunately these structures typically have very poor acoustic performance. There is increasingly growing demand in mitigating this noise issue in sandwich composite structures. This study shows that marrying carbon fiber composites with natural cork in a sandwich structure provides a synergistic effect yielding a noise-free sandwich composite structure without the sacrifice of mechanical performance or weight. Moreover the cork-core sandwich composites boast a 250% improvement in damping performance, providing increased durability and lifetime operation. Additionally as the world seeks environmentally friendly materials, the harvesting of cork is a natural, renewable process which reduces subsequent carbon footprints. Such a transition from synthetic foam cores to natural cork cores could provide unprecedented improvements in acoustic and vibrational performance in applications such as aircraft cabins or wind turbine blades.

3D Printing Variable Stiffness Foams Using Viscous Thread Instability

PubMed Central

Lipton, Jeffrey I.; Lipson, Hod

2016-01-01

Additive manufacturing of cellular structures has numerous applications ranging from fabrication of biological scaffolds and medical implants, to mechanical weight reduction and control over mechanical properties. Various additive manufacturing processes have been used to produce open regular cellular structures limited only by the resolution of the printer. These efforts have focused on printing explicitly designed cells or explicitly planning offsets between strands. Here we describe a technique for producing cellular structures implicitly by inducing viscous thread instability when extruding material. This process allows us to produce complex cellular structures at a scale that is finer than the native resolution of the printer. We demonstrate tunable effective elastic modulus and density that span two orders of magnitude. Fine grained cellular structures allow for fabrication of foams for use in a wide range of fields ranging from bioengineering, to robotics to food printing. PMID:27503148

Intertwined nanocarbon and manganese oxide hybrid foam for high-energy supercapacitors.

PubMed

Wang, Wei; Guo, Shirui; Bozhilov, Krassimir N; Yan, Dong; Ozkan, Mihrimah; Ozkan, Cengiz S

2013-11-11

Rapid charging and discharging supercapacitors are promising alternative energy storage systems for applications such as portable electronics and electric vehicles. Integration of pseudocapacitive metal oxides with single-structured materials has received a lot of attention recently due to their superior electrochemical performance. In order to realize high energy-density supercapacitors, a simple and scalable method is developed to fabricate a graphene/MWNT/MnO2 nanowire (GMM) hybrid nanostructured foam, via a two-step process. The 3D few-layer graphene/MWNT (GM) architecture is grown on foamed metal foils (nickel foam) via ambient pressure chemical vapor deposition. Hydrothermally synthesized α-MnO2 nanowires are conformally coated onto the GM foam by a simple bath deposition. The as-prepared hierarchical GMM foam yields a monographical graphene foam conformally covered with an intertwined, densely packed CNT/MnO2 nanowire nanocomposite network. Symmetrical electrochemical capacitors (ECs) based on GMM foam electrodes show an extended operational voltage window of 1.6 V in aqueous electrolyte. A superior energy density of 391.7 Wh kg(-1) is obtained for the supercapacitor based on the GMM foam, which is much higher than ECs based on GM foam only (39.72 Wh kg(-1) ). A high specific capacitance (1108.79 F g(-1) ) and power density (799.84 kW kg(-1) ) are also achieved. Moreover, the great capacitance retention (97.94%) after 13 000 charge-discharge cycles and high current handability demonstrate the high stability of the electrodes of the supercapacitor. These excellent performances enable the innovative 3D hierarchical GMM foam to serve as EC electrodes, resulting in energy-storage devices with high stability and power density in neutral aqueous electrolyte. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Thermally insulating and fire-retardant lightweight anisotropic foams based on nanocellulose and graphene oxide.

PubMed

Wicklein, Bernd; Kocjan, Andraž; Salazar-Alvarez, German; Carosio, Federico; Camino, Giovanni; Antonietti, Markus; Bergström, Lennart

2015-03-01

High-performance thermally insulating materials from renewable resources are needed to improve the energy efficiency of buildings. Traditional fossil-fuel-derived insulation materials such as expanded polystyrene and polyurethane have thermal conductivities that are too high for retrofitting or for building new, surface-efficient passive houses. Tailored materials such as aerogels and vacuum insulating panels are fragile and susceptible to perforation. Here, we show that freeze-casting suspensions of cellulose nanofibres, graphene oxide and sepiolite nanorods produces super-insulating, fire-retardant and strong anisotropic foams that perform better than traditional polymer-based insulating materials. The foams are ultralight, show excellent combustion resistance and exhibit a thermal conductivity of 15 mW m(-1) K(-1), which is about half that of expanded polystyrene. At 30 °C and 85% relative humidity, the foams retained more than half of their initial strength. Our results show that nanoscale engineering is a promising strategy for producing foams with excellent properties using cellulose and other renewable nanosized fibrous materials.

Controlling shockwave dynamics using architecture in periodic porous materials

DOE PAGES

Branch, Brittany; Ionita, Axinte; Clements, Bradford E.; ...

2017-04-07

Additive manufacturing (AM) is an attractive approach for the design and fabrication of structures capable of achieving controlled mechanical response of the underlying deformation mechanisms. While there are numerous examples illustrating how the quasi-static mechanical responses of polymer foams have been tailored by additive manufacturing, there is limited understanding of the response of these materials under shockwave compression. Dynamic compression experiments coupled with time-resolved X-ray imaging were performed to obtain insights into the in situ evolution of shockwave coupling to porous, periodic polymer foams. We further demonstrate shock wave modulation or “spatially graded-flow” in shock-driven experiments via the spatial controlmore » of layer symmetries afforded by additive manufacturing techniques at the micron scale.« less

Morphologies, Processing and Properties of Ceramic Foams from Pre-Ceramic Foams from Pre-Ceramic Polymer Routes

NASA Technical Reports Server (NTRS)

Stackpoole, Mairead; Simoes, Conan R.; Venkatapathy, Ethiras (Technical Monitor)

2002-01-01

The current research is focused on processing ceramic foams that have potential as a thermal protection material. Ceramic foams with different architectures were formed from the pyrolysis of pre-ceramic polymers at 1200 C in different atmospheres. In some systems a sacrificial polyurethane was used as the blowing agent. We have also processed foams using sacrificial fillers to introduce controlled cell sizes. Each sacrificial filler or blowing agent leads to a unique morphology. The effect of different fillers on foam morphologies will be presented. The presentation will also focus on characterization of these foams in terms of mechanical and thermal properties. Foams processed using these approaches having bulk densities ranging from 0.15 to 0.9 g per cubic centimeter and a cell sizes from 5 to 500 micrometers. Compression strengths ranged from 2 to 7 MPa for these materials.

Positive and negative impacts of specialty malts on beer foam: a comparison of various cereal products for their foaming properties.

PubMed

Combe, Alexander L; Ang, Justin K; Bamforth, Charles W

2013-07-01

The foam stability of beer is dependent on the presence of foam-stabilizing polypeptides derived from the cereals from which it is made. It has long been argued that there is a tendency to boost the foam-stabilizing capabilities of these polypeptides at the heating stages involved in the production of the grist materials. The present study started with the intent to confirm whether these changes occurred and to assess the extent to which different cereal products differed in their foam-stabilizing tendencies. Cereal products differ enormously in their foam-stabilizing capabilities. Heavily roasted grains, notably black malt and roast barley, do have superior foaming properties. However, certain specialty malts, notably crystal malts, display inferior foam performance. The observed foaming pattern is a balance between their content of foam-positive and foam-negative components. Products such as pale malt do contain foam-negative materials but have a net balance in favour of foam-stabilizing entities. By contrast, wheat malt and especially black malt have a heavy preponderance of foam-positive components. Crystal malt displays the converse behaviour: it contains low-molecular-weight foam-negative species. Several of the cereal products appear to contain higher-molecular-weight foam inhibitors, but it appears that they are merely species that are of inherently inferior foam-stabilizing capability to the foaming polypeptides from egg white that were employed to probe the system. The foam-damaging species derived from crystal malt carried through to beers brewed from them. Intense heating in the production of cereal products does lead to enhanced foam performance in extracts of those products. However, not all speciality malts display superior foam performance, through their development of foam-negative species of lower molecular weight. © 2013 Society of Chemical Industry.

Foam/Aerogel Composite Materials for Thermal and Acoustic Insulation and Cryogen Storage

NASA Technical Reports Server (NTRS)

Williams, Martha K. (Inventor); Smith, Trent M. (Inventor); Fesmire, James E. (Inventor); Sass, Jared P. (Inventor); Weiser, Erik S. (Inventor)

2011-01-01

The invention involves composite materials containing a polymer foam and an aerogel. The composite materials have improved thermal insulation ability, good acoustic insulation, and excellent physical mechanical properties. The composite materials can be used, for instance, for heat and acoustic insulation on aircraft, spacecraft, and maritime ships in place of currently used foam panels and other foam products. The materials of the invention can also be used in building construction with their combination of light weight, strength, elasticity, ability to be formed into desired shapes, and superior thermal and acoustic insulation power. The materials have also been found to have utility for storage of cryogens. A cryogenic liquid or gas, such as N.sub.2 or H.sub.2, adsorbs to the surfaces in aerogel particles. Thus, another embodiment of the invention provides a storage vessel for a cryogen.

Foam/aerogel composite materials for thermal and acoustic insulation and cryogen storage

NASA Technical Reports Server (NTRS)

Smith, Trent M. (Inventor); Fesmire, James E. (Inventor); Williams, Martha K. (Inventor); Sass, Jared P. (Inventor); Weiser, Erik S. (Inventor)

2010-01-01

The invention involves composite materials containing a polymer foam and an aerogel. The composite materials have improved thermal insulation ability, good acoustic insulation, and excellent physical mechanical properties. The composite materials can be used, for instance, for heat and acoustic insulation on aircraft, spacecraft, and maritime ships in place of currently used foam panels and other foam products. The materials of the invention can also be used in building construction with their combination of light weight, strength, elasticity, ability to be formed into desired shapes, and superior thermal and acoustic insulation power. The materials have also been found to have utility for storage of cryogens. A cryogenic liquid or gas, such as N.sub.2 or H.sub.2, adsorbs to the surfaces in aerogel particles. Thus, another embodiment of the invention provides a storage vessel for a cryogen.

Preparation and magnetic properties of the Sr-hexaferrite with foam structure

NASA Astrophysics Data System (ADS)

Guerrero, A. L.; Espericueta, D. L.; Palomares-Sánchez, S. A.; Elizalde-Galindo, J. T.; Watts, B. E.; Mirabal-García, M.

2016-12-01

This work reports an optimal way to fabricate strontium hexaferrite with porous-reticulated structure using a variation of the replication technique and taking two different precursors, one obtained from the coprecipitation and the other from the ceramic method. Changes made to the original replication technique include the addition of Arabic gum as binder, and the addition of ethylene glycol to form the ceramic sludge. In addition, some parameters such as the relation between solid material and liquid phase, the quantity of binder and the heat treatment were varied to obtain high quality magnetic foams. Two polymeric sponges were used as patterns, one with average pore size of 300 μm diameter and the other with 1100 μm. The characterization of the samples included the analysis of the structure and phase purity, the magnetic properties, the remanence properties, magnetic interactions and the microstructural characteristics. Results indicate that both, the powder precursors and the polymeric pattern play an important role in the configuration of the foam structure and this configuration has an important influence on the dipolar interactions which tend to demagnetize the samples. In addition, it was analyzed the behavior between the minimum value of the δM curves and the hysteresis properties.

New Concept Study for Repair of Bomb-Damaged Runways. Volume I. Concept Identification.

DTIC Science & Technology

1979-09-01

Expanded polystyrene beads would be pneumatically mixed with the cement to form a low density material. Initially, the ratio of foam to cement would...the combinations are presented with this concept. PRIMARY MATERIALS 0 Expanded polystyrene foam beads * Graded aggregate * Quick setting cement 61 E-4...probability of success - high ALTERNATE MATERIALS * Expanded polystyrene foam beads * Organic binders Furan Methyl Methacrylate Epoxy Aminos * Graded

Indentability of conventional and negative Poisson's ratio foams

NASA Technical Reports Server (NTRS)

Lakes, R. S.; Elms, K.

1992-01-01

The indentation resistance of foams, both of conventional structure and of re-entrant structure giving rise to negative Poisson's ratio, is studied using holographic interferometry. In holographic indentation tests, re-entrant foams had higher yield strengths sigma(sub y) and lower stiffness E than conventional foams of the same original relative density. Calculated energy absorption for dynamic impact is considerably higher for re-entrant foam than conventional foam.

Holographic study of conventional and negative Poisson's ratio metallic foams - Elasticity, yield and micro-deformation

NASA Technical Reports Server (NTRS)

Chen, C. P.; Lakes, R. S.

1991-01-01

An experimental study by holographic interferometry is reported of the following material properties of conventional and negative Poisson's ratio copper foams: Young's moduli, Poisson's ratios, yield strengths and characteristic lengths associated with inhomogeneous deformation. The Young's modulus and yield strength of the conventional copper foam were comparable to those predicted by microstructural modeling on the basis of cellular rib bending. The reentrant copper foam exhibited a negative Poisson's ratio, as indicated by the elliptical contour fringes on the specimen surface in the bending tests. Inhomogeneous, non-affine deformation was observed holographically in both foam materials.

Thermal Performance of Aged and Weathered Spray-On Foam Insulation (SOFI) Materials Under Cryogenic Vacuum Conditions (Cryostat-4)

NASA Technical Reports Server (NTRS)

2008-01-01

The NASA Cryogenics Test Laboratory at Kennedy Space Center conducted long-term testing of SOFI materials under actual-use cryogenic conditions with Cryostat-4. The materials included in the testing were NCFI 24-124 (acreage foam), BX-265 (close-out foam, including intertank flange and bipod areas), and a potential alternate material, NCFI 27-68, (acreage foam with the flame retardant removed). Specimens of these materials were placed at two locations: a site that simulated aging (the Vehicle Assembly Building [VAB]) and a site that simulated weathering (the Atmospheric Exposure Test Site [beach site]). After aging/weathering intervals of 3, 6, and 12 months, the samples were retrieved and tested for their thermal performance under cryogenic vacuum conditions with test apparatus Cryostat-4.

Characterization of a compliant multi-layer system for tactile sensing with enhanced sensitivity and range

NASA Astrophysics Data System (ADS)

Chen, Ying; Yu, Miao; Bruck, Hugh A.; Smela, Elisabeth

2018-06-01

To allow robots to interact with humans via touch, new sensing concepts are needed that can detect a wide range of potential interactions and cover the body of a robot. In this paper, a skin-inspired multi-layer tactile sensing architecture is presented and characterized. The structure consists of stretchable piezoresistive strain-sensing layers over foam layers of different stiffness, allowing for both sufficient sensitivity and pressure range for human contacts. Strip-shaped sensors were used in this architecture to produce a deformation response proportional to pressure. The roles of the foam layers were elucidated by changing their stiffness and thickness, allowing the development of a geometric model to account for indenter interactions with the structure. The advantage of this architecture over other approaches is the ability to easily tune performance by adjusting the stiffness or thickness of the foams to tailor the response for different applications. Since viscoelastic materials were used, the temporal effects were also investigated.

Potential production of palm oil-based foaming agent as fire extinguisher of peatlands in Indonesia: Literature review

NASA Astrophysics Data System (ADS)

Subekti, P.; Hambali, E.; Suryani, A.; Suryadarma, P.

2017-05-01

This study aims to analyze the potential aplication of of palm oil-based foaming agent as peat fires fighter in Indonesia. From literature review, it has been known that the foaming agent able to form foam to extinguish fire, wrap and refrigerate the burning peat. It is necessary to develop the production and application of foaming agent in Indonesia because peat fires occur almost every year that caused smoke haze. Potential raw material for the production of environmental friendly foaming agent as foam extinguishing for peat fires in Indonesia aong other is palm oil due to abundant availability, sustainable, and foam product easily degraded in the environment of the burnt areas. Production of foaming agent as fire-fighting in Indonesia is one alternative to reduce the time to control the fire and smog disaster impact. Application of palm oil as a raw material for fire-fighting is contribute to increase the value added and the development of palm oil downstream industry.

Pitch-based carbon foam and composites and use thereof

DOEpatents

Klett, James W.; Burchell, Timothy D.; Choudhury, Ashok

2006-07-04

A thermally conductive carbon foam is provided, normally having a thermal conductivity of at least 40 W/mK. The carbon foam usually has a specific thermal conductivity, defined as the thermal conductivity divided by the density, of at least about 75 Wcm.sup.3/m.degree. Kgm. The foam also has a high specific surface area, typically at least about 6,000 m.sup.2/m.sup.3. The foam is characterized by an x-ray diffraction pattern having "doublet" 100 and 101 peaks characterized by a relative peak split factor no greater than about 0.470. The foam is graphitic and exhibits substantially isotropic thermal conductivity. The foam comprises substantially ellipsoidal pores and the mean pore diameter of such pores is preferably no greater than about 340 microns. Other materials, such as phase change materials, can be impregnated in the pores in order to impart beneficial thermal properties to the foam. Heat exchange devices and evaporatively cooled heat sinks utilizing the foams are also disclosed.

Pitch-based carbon foam and composites and uses thereof

DOEpatents

Klett, James W.; Burchell, Timothy D.; Choudhury, Ashok

2004-01-06

A thermally conductive carbon foam is provided, normally having a thermal conductivity of at least 40 W/m.multidot.K. The carbon foam usually has a specific thermal conductivity, defined as the thermal conductivity divided by the density, of at least about 75 W.multidot.cm.sup.3 /m.multidot..degree.K.multidot.gm. The foam also has a high specific surface area, typically at least about 6,000 m.sup.2 /m.sup.3. The foam is characterized by an x-ray diffraction pattern having "doublet" 100 and 101 peaks characterized by a relative peak split factor no greater than about 0.470. The foam is graphitic and exhibits substantially isotropic thermal conductivity. The foam comprises substantially ellipsoidal pores and the mean pore diameter of such pores is preferably no greater than about 340 microns. Other materials, such as phase change materials, can be impregnated in the pores in order to impart beneficial thermal properties to the foam. Heat exchange devices and evaporatively cooled heat sinks utilizing the foams are also disclosed.

Electricity in foams: from one soapy interface to the macroscopic material

NASA Astrophysics Data System (ADS)

Biance, Anne-Laure

2017-11-01

Liquid foams (a dispersion of gas bubbles in a soapy solution) destabilize with time due to coarsening, coalescence and gravity driven drainage. We propose here to inhibit (or trigger) the foam destabilization by applying an electric field to the material. This effect is investigated at the different scales of the system: one soapy interface, one liquid film, the macroscopic foam. The generation of an electroosmotic flow near a soapy liquid/gas interface raises many issues. How does the flow affect surfactant repartition? Is there a Marangoni stress at the interface? At the scale of one soap film, how the electric field affects the film stability and deformation? In a macroscopic foam, one can wonder whether the electric field can indeed reverse gravity driven drainage and increase foam lifetime? These different issues are considered by developing new experimental techniques allowing us to probe surfactant repartition at liquid interfaces, soap film thicknesses and liquid foam properties when an electric field is applied. The results will be presented together with a comprehensive picture of the mechanisms arising at each scale of the material, to conclude with the potential use of electricity in liquid foams to control destabilization. Collaborators: Baptiste Blanc, Oriane Bonhomme, Laurent Joly, Christophe Ybert.

Synergistic effect of high and low molecular weight molecules in the foamability and foam stability of sparkling wines.

PubMed

Coelho, Elisabete; Reis, Ana; Domingues, M Rosário M; Rocha, Sílvia M; Coimbra, Manuel A

2011-04-13

The foam of sparkling wines is a key parameter of their quality. However, the compounds that are directly involved in foam formation and stabilization are not yet completely established. In this work, seven sparkling wines were produced in Bairrada appellation (Portugal) under different conditions and their foaming properties evaluated using a Mosalux-based device. Fractionation of the sparkling wines into four independent fractions, (1) high molecular weight material, with molecular weight higher than 12 kDa (HMW), (2) hydrophilic material with molecular weigh between 1 and 12 kDa (AqIMW), (3) hydrophobic material with molecular weigh between 1 and 12 kDa (MeIMW), and (4) hydrophobic material with a molecular weight lower than 1 kDa (MeLMW), allowed the observation that the wines presenting the lower foam stability were those that presented lower amounts of the MeLMW fraction. The fraction that presented the best foam stability was HMW. When HMW is combined with MeLMW fraction, the foam stability largely increased. This increase was even larger, approaching the foam stability of the sparkling wine, when HMW was combined with the less hydrophobic subfraction of MeLMW (fraction 3). Electrospray tandem mass spectrometry (ESI-MS/MS) of fraction 3 allowed the assignment of polyethylene glycol oligomers (n = 5-11) and diethylene glycol 8-hydroxytridecanoate glyceryl acetate. To observe if these molecules occur in sparkling wine foam, the MeLMW was recovered directly from the sparkling wine foam and was also analyzed by ESI-MS/MS. The presence of monoacylglycerols of palmitic and stearic acids, as well as four glycerylethylene glycol fatty acid derivatives, was observed. These surface active compounds are preferentially partitioned by the sparkling wine foam rather than the liquid phase, allowing the inference of their role as key components in the promotion and stabilization of sparkling wine foam.

Energy absorption capability of foam-based composite materials and their applications as seat cushions in aircraft crashworthiness

NASA Astrophysics Data System (ADS)

Kh. Beheshti, Hamid

This study is focusing on the application of foam materials in aviation. These materials are being used for acoustic purposes, as padding in the finished interior panels of the aircraft, and as seat cushions. Foams are mostly used in seating applications. Since seat cushion is directly interacting with the body of occupant, it has to be ergonomically comfortable beside of absorbing the energy during the impact. All the seats and seat cushions have to pass regulations defined by Federal Aviation Administration (FAA). In fact, all airplane companies are required to certify the subcomponents of aircrafts before installing them on the main structure, fuselage. Current Federal Aviation Administration Regulations require a dynamic sled test of the entire seat system for certifying the seat cushions. This dynamic testing is required also for replacing the deteriorated cushions with new cushions. This involves a costly and time-consuming certification process. AGATE group has suggested a procedure based on quasi-static testing in order to certify new seat cushions without conducting full-scale dynamic sled testing. AGATE subcomponent methodology involves static tests of the energy-absorbing foam cushions and design validation by conducting a full-scale dynamic seat test. Microscopic and macroscopic studies are necessary to provide a complete understanding about performance of foams during the crash. Much investigation has been done by different sources to obtain the reliable modeling in terms of demonstration of mechanical behavior of foams. However, rate sensitivity of foams needs more attention. A mathematical hybrid dynamic model for the cushion underneath of the human body will be taken into consideration in this research. Analytical and finite element codes such as MADYMO and LS-DYNA codes have the potential to greatly speed up the crashworthy design process, to help certify seats and aircraft to dynamic crash loads, to predict seat and occupant response to impact with the probability of injury, and to evaluate numerous crash scenarios not economically feasible with full-scale crash testing. Therefore, these codes are being used to find the accurate response of spinal load during the impact of model including human body, seat cushion and seat under different acceleration pulses. (Abstract shortened by UMI.)

Design of a porous cobalt sulfide nanosheet array on Ni foam from zeolitic imidazolate frameworks as an advanced electrode for supercapacitors.

PubMed

Han, Xue; Tao, Kai; Wang, Ding; Han, Lei

2018-02-08

Porous nanosheet-structured electrode materials are very attractive for the high efficiency storage of electrochemical energy. Herein, a porous cobalt sulfide nanosheet array on Ni foam (Co 9 S 8 -NSA/NF) is successfully fabricated by a facile method, which involves the uniform growth of 2D Co-based leaf-like zeolitic imidazole frameworks (Co-ZIF-L) on Ni foam followed by subsequent sulfurization with thioacetamide (TAA). Benefiting from the unique porous nanosheet array architecture and conductive substrate, the Co 9 S 8 -NSA/NF exhibits excellent electrochemical performance with a high capacitance (1098.8 F g -1 at 0.5 A g -1 ), good rate capacity (54.6% retention at 10 A g -1 ) and long-term stability (87.4% retention over 1000 cycles), when acted as a binder-free electrode for supercapacitors. Furthermore, an assembled asymmetric supercapacitor device using the as-fabricated Co 9 S 8 -NSA as the positive electrode and activated carbon (AC) as the negative electrode also exhibits a high energy density of 20.0 W h kg -1 at a high power density of 828.5 W kg -1 . The method developed here can be extended to the construction of other structured metal (mono or mixed) sulfide electrode materials for more efficient energy storage.

In vivo performance of novel soybean/gelatin-based bioactive and injectable hydroxyapatite foams

PubMed Central

Kovtun, Anna; Goeckelmann, Melanie J.; Niclas, Antje A.; Montufar, Edgar B.; Ginebra, Maria-Pau; Planell, Josep A.; Santin, Matteo; Ignatius, Anita

2015-01-01

Major limitations of calcium phosphate cements (CPCs) are their relatively slow degradation rate and the lack of macropores allowing the ingrowth of bone tissue. The development of self-setting cement foams has been proposed as a suitable strategy to overcome these limitations. In previous work we developed a gelatine-based hydroxyapatite foam (G-foam), which exhibited good injectability and cohesion, interconnected porosity and good biocompatibility in vitro. In the present study we evaluated the in vivo performance of the G-foam. Furthermore, we investigated whether enrichment of the foam with soybean extract (SG-foam) increased its bioactivity. G-foam, SG-foam and non-foamed CPC were implanted in a critical-size bone defect in the distal femoral condyle of New Zealand white rabbits. Bone formation and degradation of the materials were investigated after 4, 12 and 20 weeks using histological and biomechanical methods. The foams maintained their macroporosity after injection and setting in vivo. Compared to non-foamed CPC, cellular degradation of the foams was considerably increased and accompanied by new bone formation. The additional functionalization with soybean extract in the SG-foam slightly reduced the degradation rate and positively influenced bone formation in the defect. Furthermore, both foams exhibited excellent biocompatibility, implying that these novel materials may be promising for clinical application in non-loaded bone defects. PMID:25448348

In vivo performance of novel soybean/gelatin-based bioactive and injectable hydroxyapatite foams.

PubMed

Kovtun, Anna; Goeckelmann, Melanie J; Niclas, Antje A; Montufar, Edgar B; Ginebra, Maria-Pau; Planell, Josep A; Santin, Matteo; Ignatius, Anita

2015-01-01

Major limitations of calcium phosphate cements (CPCs) are their relatively slow degradation rate and the lack of macropores allowing the ingrowth of bone tissue. The development of self-setting cement foams has been proposed as a suitable strategy to overcome these limitations. In previous work we developed a gelatine-based hydroxyapatite foam (G-foam), which exhibited good injectability and cohesion, interconnected porosity and good biocompatibility in vitro. In the present study we evaluated the in vivo performance of the G-foam. Furthermore, we investigated whether enrichment of the foam with soybean extract (SG-foam) increased its bioactivity. G-foam, SG-foam and non-foamed CPC were implanted in a critical-size bone defect in the distal femoral condyle of New Zealand white rabbits. Bone formation and degradation of the materials were investigated after 4, 12 and 20weeks using histological and biomechanical methods. The foams maintained their macroporosity after injection and setting in vivo. Compared to non-foamed CPC, cellular degradation of the foams was considerably increased and accompanied by new bone formation. The additional functionalization with soybean extract in the SG-foam slightly reduced the degradation rate and positively influenced bone formation in the defect. Furthermore, both foams exhibited excellent biocompatibility, implying that these novel materials may be promising for clinical application in non-loaded bone defects. Copyright © 2014 Acta Materialia Inc. All rights reserved.

Engineered carbon foam for temperature control applications

NASA Astrophysics Data System (ADS)

Almajali, Mohammad Rajab

The need for advanced thermal management materials is well recognized in the electronics and communication industries. An overall reduction in size of electronic components has lead to higher power dissipation and increased the necessity for innovative cooling designs. In response, material suppliers have developed and are continuing to develop, an increasing number of light weight thermal management materials. The new carbon foam is a low density and high thermal conductivity material which has the potential to radically improve heat transfer, thereby reducing size and weight of equipment while simultaneously increasing its efficiency and capabilities. However, carbon foam exhibits low strength and low heat capacity. The present work is intended to overcome these two main drawbacks using a combinatorial approach: (i) initially, copper coating was carried out to improve the thermo-mechanical properties of carbon foam. The thermal and mechanical properties of coated foam were measured using laser flash technique and compression test, respectively. An analytical model was developed to calculate the effective thermal conductivity. It was observed that the copper-coated carbon foam with 50% porosity can attain a thermal conductivity of 180 W/mK. The results from the analytical model were in a very good agreement with experimental results. The modulus increased from 4.5 MPa to 8.6 MPa and the plateau stress increased from 54 kPa to 171 kPa. The relationships between the measured properties and the copper weight ratio were determined. The above analyses demonstrated the significance of copper coating in tailoring carbon foam properties. (ii) Numerical and experimental studies were performed to analyze the phase change behavior of wax/foam composite encapsulated in metal casing. A two-energy equation model was solved using computational fluid dynamics software (CFD). Interfacial effects at the casing-composite junction and between the wax-foam surfaces and the capillary pressure within the foam matrix were investigated. These factors lowered the heat transfer rate considerably and the melting area was reduced by more than 23%. Two samples, coated and uncoated carbon foam, were infiltrated with PCM and subjected to a uniform heat load test in a vacuum. The coated foam showed excellent performance compared to the uncoated foam. (iii) Finally, the new engineered carbon foam was used as a heat sink and heat exchanger in a thermoelectric cooler for a cooling vest application. Using carbon foam as the core material for this application, the effective transfer of heat was significantly increased while reducing the size and weight of the heat exchanger.

Tailoring properties of reticulated vitreous carbon foams with tunable density

NASA Astrophysics Data System (ADS)

Smorygo, Oleg; Marukovich, Alexander; Mikutski, Vitali; Stathopoulos, Vassilis; Hryhoryeu, Siarhei; Sadykov, Vladislav

2016-06-01

Reticulated vitreous carbon (RVC) foams were manufactured by multiple replications of a polyurethane foam template structure using ethanolic solutions of phenolic resin. The aims were to create an algorithm of fine tuning the precursor foam density and ensure an open-cell reticulated porous structure in a wide density range. The precursor foams were pyrolyzed in inert atmospheres at 700°C, 1100°C and 2000°C, and RVC foams with fully open cells and tunable bulk densities within 0.09-0.42 g/cm3 were synthesized. The foams were characterized in terms of porous structure, carbon lattice parameters, mechanical properties, thermal conductivity, electric conductivity, and corrosive resistance. The reported manufacturing approach is suitable for designing the foam microstructure, including the strut design with a graded microstructure.

Influence of carbon nanotubes on mechanical properties and structure of rigid polyurethane foam

NASA Astrophysics Data System (ADS)

Ciecierska, E.; Jurczyk-Kowalska, M.; Bazarnik, P.; Kulesza, M.; Lewandowska, M.; Kowalski, M.; Krauze, S.

2014-08-01

In this work, the influence of carbon nanotubes addition on foam structure and mechanical properties of rigid polyurethane foam/nanotube composites was investigated. Scanning electron microscopy was performed to reveal the foam porous structure and distribution of carbon nanotubes. To determine the mechanical properties, three point bending tests were carried out.

Preparation of sintered foam materials by alkali-activated coal fly ash.

PubMed

Zhao, Yelong; Ye, Junwei; Lu, Xiaobin; Liu, Mangang; Lin, Yuan; Gong, Weitao; Ning, Guiling

2010-02-15

Coal fly ash from coal fired power stations is a potential raw material for the production of ceramic tiles, bricks and blocks. Previous works have demonstrated that coal fly ash consists mainly of glassy spheres that are relatively resistant to reaction. An objective of this research was to investigate the effect of alkali on the preparation process of the foam material. Moreover, the influence of foam dosage on the water absorption, apparent density and compressive strength was evaluated. The experimental results showed that homogenous microstructures of interconnected pores could be obtained by adding 13 wt.% foaming agent at 1050 degrees C, leading to foams presenting water absorption, apparent density and compressive strength values of about 126.5%, 0.414 g/cm(3), 6.76 MPa, respectively.

Efficient continuous dryer for flexible polyurethane foam and cleaning apparatus

DOEpatents

Jody, Bassam; Daniels, Edward; Libera, Joseph A.

1999-01-01

A method of cleaning polyurethane foams where the material is transported through a wash station while alternately soaking the polyurethane foam in an organic solvent and squeezing solvent from the polyurethane foam a number of times. Then the polyurethane foam is sent through a rinse or solvent transfer station for reducing the concentration of solvent in the foam. The rinsed polyurethane foam is sent to a drying station wherein the foam is repeatedly squeezed while being exposed to hot air to remove wet air from the foam.

Efficient continuous dryer for flexible polyurethane foam and cleaning apparatus

DOEpatents

Jody, B.; Daniels, E.; Libera, J.A.

1999-03-16

A method of cleaning polyurethane foams where the material is transported through a wash station while alternately soaking the polyurethane foam in an organic solvent and squeezing solvent from the polyurethane foam a number of times. Then the polyurethane foam is sent through a rinse or solvent transfer station for reducing the concentration of solvent in the foam. The rinsed polyurethane foam is sent to a drying station wherein the foam is repeatedly squeezed while being exposed to hot air to remove wet air from the foam. 4 figs.

Cellularized Cellular Solids via Freeze-Casting.

PubMed

Christoph, Sarah; Kwiatoszynski, Julien; Coradin, Thibaud; Fernandes, Francisco M

2016-02-01

The elaboration of metabolically active cell-containing materials is a decisive step toward the successful application of cell based technologies. The present work unveils a new process allowing to simultaneously encapsulate living cells and shaping cell-containing materials into solid-state macroporous foams with precisely controlled morphology. Our strategy is based on freeze casting, an ice templating materials processing technique that has recently emerged for the structuration of colloids into macroporous materials. Our results indicate that it is possible to combine the precise structuration of the materials with cellular metabolic activity for the model organism Saccharomyces cerevisiae. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Low density microcellular carbon or catalytically impregnated carbon forms and process for their preparation

DOEpatents

Hopper, Robert W.; Pekala, Richard W.

1989-01-01

Machinable and structurally stable, low density microcellular carbon, and catalytically impregnated carbon, foams, and process for their preparation, are provided. Pulverized sodium chloride is classified to improve particle size uniformity, and the classified particles may be further mixed with a catalyst material. The particles are cold pressed into a compact having internal pores, and then sintered. The sintered compact is immersed and then submerged in a phenolic polymer solution to uniformly fill the pores of the compact with phenolic polymer. The compact is then heated to pyrolyze the phenolic polymer into carbon in the form of a foam. Then the sodium chloride of the compact is leached away with water, and the remaining product is freeze dried to provide the carbon, or catalytically impregnated carbon, foam.

Thermal conductivity and combustion properties of wheat gluten foams.

PubMed

Blomfeldt, Thomas O J; Nilsson, Fritjof; Holgate, Tim; Xu, Jianxiao; Johansson, Eva; Hedenqvist, Mikael S

2012-03-01

Freeze-dried wheat gluten foams were evaluated with respect to their thermal and fire-retardant properties, which are important for insulation applications. The thermal properties were assessed by differential scanning calorimetry, the laser flash method and a hot plate method. The unplasticised foam showed a similar specific heat capacity, a lower thermal diffusivity and a slightly higher thermal conductivity than conventional rigid polystyrene and polyurethane insulation foams. Interestingly, the thermal conductivity was similar to that of closed cell polyethylene and glass-wool insulation materials. Cone calorimetry showed that, compared to a polyurethane foam, both unplasticised and glycerol-plasticised foams had a significantly longer time to ignition, a lower effective heat of combustion and a higher char content. Overall, the unplasticised foam showed better fire-proof properties than the plasticized foam. The UL 94 test revealed that the unplasticised foam did not drip (form droplets of low viscous material) and, although the burning times varied, self-extinguished after flame removal. To conclude both the insulation and fire-retardant properties were very promising for the wheat gluten foam. © 2012 American Chemical Society

Evaporation-based method for preparing gelatin foams with aligned tubular pore structures.

PubMed

Frazier, Shane D; Srubar, Wil V

2016-05-01

Gelatin-based foams with aligned tubular pore structures were prepared via liquid-to-gas vaporization of tightly bound water in dehydrated gelatin hydrogels. This study elucidates the mechanism of the foaming process by investigating the secondary (i.e., helical) structure, molecular interactions, and water content of gelatin films before and after foaming using X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry and thermogravimetric analysis (TGA), respectively. Experimental data from gelatin samples prepared at various gelatin-to-water concentrations (5-30 wt.%) substantiate that resulting foam structures are similar in pore diameter (approximately 350 μm), shape, and density (0.05-0.22 g/cm(3)) to those fabricated using conventional methods (e.g., freeze-drying). Helical structures were identified in the films but were not evident in the foamed samples after vaporization (~150 °C), suggesting that the primary foaming mechanism is governed by the vaporization of water that is tightly bound in secondary structures (i.e., helices, β-turns, β-sheets) that are present in dehydrated gelatin films. FTIR and TGA data show that the foaming process leads to more disorder and reduced hydrogen bonding to hydroxyl groups in gelatin and that no thermal degradation of gelatin occurs before or after foaming. Copyright © 2016 Elsevier B.V. All rights reserved.

Structural optimization of structured carbon-based energy-storing composite materials used in space vehicles.

PubMed

Yu, Jia; Yu, Zhichao; Tang, Chenlong

2016-07-04

The hot work environment of electronic components in the instrument cabin of spacecraft was researched, and a new thermal protection structure, namely graphite carbon foam, which is an impregnated phase-transition material, was adopted to implement the thermal control on the electronic components. We used the optimized parameters obtained from ANSYS to conduct 2D optimization, 3-D modeling and simulation, as well as the strength check. Finally, the optimization results were verified by experiments. The results showed that after optimization, the structured carbon-based energy-storing composite material could reduce the mass and realize the thermal control over electronic components. This phase-transition composite material still possesses excellent temperature control performance after its repeated melting and solidifying.

Processing and properties of Ti-6Al-4V hollow sphere foams from hydride powder

NASA Astrophysics Data System (ADS)

Hardwicke, Canan Uslu

Honeycomb structures currently used in aerospace systems are expensive to manufacture, limited to sheet form, and present joining problems and mechanical anisotropy that promotes shear failure at low stresses. Metallic foams produced by point contact bonding of monosized hollow spheres offer an alternative if they can be processed into strong, light-weight, and reasonably priced structural materials. In this work, technology has been established for fabricating good quality, Ti-6Al-4V hollow sphere foams using the coaxial nozzle powder slurry technique. It was shown that hydride form of Ti-ELI can be used as the starting precursor powder and processed into fine particles of 1-10 mum size range without increasing the impurity levels. Hydride dispersion in acetone was provided by the addition of polyester/polyamine copolymers through electrosteric stabilization. Addition of PMMA to the pseudoplastically dispersed organic slurries helped bind hydride powder spherical shells. Furthermore, monosized Ti-6Al-4V hollow spheres were sintered to 98% dense cell walls in Ar and point-contact bonded into closed-cell foams through solid-state diffusion. These findings suggest that near-net shape Ti-6Al-4V structures may be produced with isotropic properties, strength, toughness, and densities as low as 10% of the bulk. Findings concerning the optimum processing parameters and implications for future research are discussed.

Properties of Shocked Polymers: Mbar experiments on Z and multi-scale simulations

NASA Astrophysics Data System (ADS)

Mattsson, Thomas R.

2010-03-01

Significant progress has been made over the last few years in understanding properties of matter subject to strong shocks and other extreme conditions. High-accuracy multi-Mbar experiments and first-principles theoretical studies together provide detailed insights into the physics and chemistry of high energy-density matter. While comprehensive advances have been made for pure elements like deuterium, helium, and carbon, progress has been slower for equally important, albeit more challenging, materials like molecular crystals, polymers, and foams. Hydrocarbon based polymer foams are common materials and in particular they are used in designing shock- and inertial confinement fusion experiments. Depending on their initial density, foams shock to relatively higher pressure and temperature compared to shocked dense polymers/plastics. As foams and polymers are shocked, they exhibit both structural and chemical transitions. We will present experimental and theoretical results for shocked polymers in the Mbar regime. By shock impact of magnetically launched flyer plates on poly(4-methyl-1-pentene) foams, we create multi-Mbar pressures in a dense plasma mixture of hydrogen, carbon, at temperatures of several eV. Concurrently with executing experiments, we analyze the system by multi-scale simulations, from density functional theory to continuum magneto-hydrodynamics simulations. In particular, density functional theory (DFT) molecular dynamics (MD) and classical MD simulations of the principal shock Hugoniot will be presented in detail for two hydrocarbon polymers: polyethylene (PE) and poly(4-methyl-1-pentene) (PMP).

Three-Dimensional Graphene Foam Induces Multifunctionality in Epoxy Nanocomposites by Simultaneous Improvement in Mechanical, Thermal, and Electrical Properties.

PubMed

Embrey, Leslie; Nautiyal, Pranjal; Loganathan, Archana; Idowu, Adeyinka; Boesl, Benjamin; Agarwal, Arvind

2017-11-15

Three-dimensional (3D) macroporous graphene foam based multifunctional epoxy composites are developed in this study. Facile dip-coating and mold-casting techniques are employed to engineer microstructures with tailorable thermal, mechanical, and electrical properties. These processing techniques allow capillarity-induced equilibrium filling of graphene foam branches, creating epoxy/graphene interfaces with minimal separation. Addition of 2 wt % graphene foam enhances the glass transition temperature of epoxy from 106 to 162 °C, improving the thermal stability of the polymer composite. Graphene foam aids in load-bearing, increasing the ultimate tensile strength by 12% by merely 0.13 wt % graphene foam in an epoxy matrix. Digital image correlation (DIC) analysis revealed that the graphene foam cells restrict and confine the deformation of the polymer matrix, thereby enhancing the load-bearing capability of the composite. Addition of 0.6 wt % graphene foam also enhances the flexural strength of the pure epoxy by 10%. A 3D network of graphene branches is found to suppress and deflect the cracks, arresting mechanical failure. Dynamic mechanical analysis (DMA) of the composites demonstrated their vibration damping capability, as the loss tangent (tan δ) jumps from 0.1 for the pure epoxy to 0.24 for ∼2 wt % graphene foam-epoxy composite. Graphene foam branches also provide seamless pathways for electron transfer, which induces electrical conductivity exceeding 450 S/m in an otherwise insulator epoxy matrix. The epoxy-graphene foam composite exhibits a gauge factor as high as 4.1, which is twice the typical gauge factor for the most common metals. Simultaneous improvement in thermal, mechanical, and electrical properties of epoxy due to 3D graphene foam makes epoxy-graphene foam composite a promising lightweight and multifunctional material for aiding load-bearing, electrical transport, and motion sensing in aerospace, automotive, robotics, and smart device structures.

A novel highly porous ceramic foam with efficient thermal insulation and high temperature resistance properties fabricated by gel-casting process

NASA Astrophysics Data System (ADS)

Yu, Jiahong; Wang, Guixiang; Tang, Di; Qiu, Ya; Sun, Nali; Liu, Wenqiao

2018-01-01

The design of super thermal insulation and high-temperature resistant materials for high temperature furnaces is crucial due to the energy crisis and the huge wasting. Although it is told that numerous studies have been reported about various of thermal insulation materials prepared by different methods, the applications of yttria-stabilized zirconia (YSZ) ceramic foams fabricated through tert-butyl alcohol (TBA)-based gel-casting process in bulk thermal isolators were barely to seen. In this paper, highly porous yttria-stabilized zirconia (YSZ) ceramic foams were fabricated by a novel gel-casting method using tert-butyl alcohol (TBA) as solvent and pore-forming agent. Different raw material ratio, sintering temperature and soaking time were all investigated to achieve optimal thermal insulation and mechanical properties. We can conclude that porosity drops gradually while compressive strength increases significantly with the rising temperature from 1000-1500°C. With prolonged soaking time, there is no obvious change in porosity but compressive strength increases gradually. All specimens have uniformly distributed pores with average size of 0.5-2μm and show good structural stability at high temperature. The final obtained ceramic foams displayed an outstanding ultra-low thermal conductivity property with only 200.6 °C in cold surface while the hot side was 1000 °C (hold 60 min to keep thermal balance before testing) at the thickness of 10 mm.

The direct and inverse problems of an air-saturated porous cylinder submitted to acoustic radiation.

PubMed

Ogam, Erick; Depollier, Claude; Fellah, Z E A

2010-09-01

Gas-saturated porous skeleton materials such as geomaterials, polymeric and metallic foams, or biomaterials are fundamental in a diverse range of applications, from structural materials to energy technologies. Most polymeric foams are used for noise control applications and knowledge of the manner in which the energy of sound waves is dissipated with respect to the intrinsic acoustic properties is important for the design of sound packages. Foams are often employed in the audible, low frequency range where modeling and measurement techniques for the recovery of physical parameters responsible for energy loss are still few. Accurate acoustic methods of characterization of porous media are based on the measurement of the transmitted and/or reflected acoustic waves by platelike specimens at ultrasonic frequencies. In this study we develop an acoustic method for the recovery of the material parameters of a rigid-frame, air-saturated polymeric foam cylinder. A dispersion relation for sound wave propagation in the porous medium is derived from the propagation equations and a model solution is sought based on plane-wave decomposition using orthogonal cylindrical functions. The explicit analytical solution equation of the scattered field shows that it is also dependent on the intrinsic acoustic parameters of the porous cylinder, namely, porosity, tortuosity, and flow resistivity (permeability). The inverse problem of the recovery of the flow resistivity and porosity is solved by seeking the minima of the objective functions consisting of the sum of squared residuals of the differences between the experimental and theoretical scattered field data.

Science and Engineering of Carbon Foams

DTIC Science & Technology

2006-07-17

production process tends to vary, many processes start with a compacted, porous pre-form of pitch material. The pitch pre-form is then melted under high...Foams 1.11 Theory for thermal transport Carbon foam can be modeled in the manner of a porous media. Many of these models are based on the analysis of...intrinsic density of the solid, P is the porosity of the porous material, and R is the relative density. The value of thermal conductivity of foam with

Assessment of Technologies for the Space Shuttle External Tank Thermal Protection System and Recommendations for Technology Improvement. Part 1; Materials Characterization and Analysis

NASA Technical Reports Server (NTRS)

Weiser, Erik S.; SaintClair, Terry L.; Nemeth, Michael P.

2004-01-01

The use of foam insulation on the External Tank (ET) was necessitated by the potentially hazardous build up of ice on the vehicle prior to and during launch. This use of foam was initiated on the Saturn V rocket, which, like the Space Shuttle, used cryogenic fuel. Two major types of foam have been used on the ET. The first type is NCFI 24-124, an acreage material that is automatically sprayed on in a controlled environment. It replaced CPR 488 in 1998 and has been used since that time. The other major foams, BX-250 or BX-265, are handsprayed foams that are used to close out regions where the various sections of the ET are attached. The objectives of the present report are to study the chemistries of the various foam materials and to determine how physical and mechanical anomalies might occur during the spray and curing process. To accomplish these objectives, the report is organized as follows. First, the chemistries of the raw materials will be discussed. This will be followed by a discussion of how chemistry relates to void formation. Finally, a TGA-MS will be used to help understand the various foams and how they degrade with the evolution of chemical by-products.

Technology for Transportation Safety

NASA Technical Reports Server (NTRS)

1981-01-01

Boston Insulated Wire & Cable developed a new polyimide foam material, commercially known as Solimide, which resists ignition. It chars and decomposes when exposed to open flames. Used in the space shuttle, the material does not "outgas" until it begins to char making it safer than current materials with respect to toxic fumes. The polyimide can be made in two forms: a resilient foam and a rigid foam. Used in commercial transport interiors for such soft components as seat cushions to door, wall, floor, and ceiling panels. Material's flame resistance could lengthen from two minutes to five minutes, the time needed for passenger evacuation in a ground emergency. Could help reduce airline fuel consumption, since the foam is 50% lighter than current materials. Low-smoke cable assemblies used in rapid transit systems consists of an advanced wire and cable jacketing material with superior flame resistance and smoke retardation characteristics. Being supplied to mass transit systems in the U.S. and abroad.

Deployment, Foam Rigidization, and Structural Characterization of Inflatable Thin-Film Booms

NASA Technical Reports Server (NTRS)

Schnell, Andrew R.; Leigh, Larry M., Jr.; Tinker, Michael L.; McConnaughey, Paul R. (Technical Monitor)

2002-01-01

Detailed investigation of the construction, packaging/deployment, foam rigidization, and structural characterization of polyimide film inflatable booms is described. These structures have considerable potential for use in space with solar concentrators, solar sails, space power systems including solar arrays, and other future missions. Numerous thin-film booms or struts were successfully constructed, inflated, injected with foam, and rigidized. Both solid-section and annular test articles were fabricated, using Kapton polyimide film, various adhesives, Styrofoam end plugs, and polyurethane pressurized foam. Numerous inflation/deployment experiments were conducted and compared to computer simulations using the MSC/DYTRAN code. Finite element models were developed for several foam-rigidized struts and compared to model test results. Several problems encountered in the construction, deployment, and foam injection/rigidization process are described. Areas of difficulty included inadequate adhesive strength, cracking of the film arid leakage, excessive bending of the structure during deployment, problems with foam distribution and curing properties, and control of foam leakage following injection into the structure. Many of these problems were overcome in the course of the research.

Refractory Ceramic Foams for Novel Applications

NASA Technical Reports Server (NTRS)

Stackpoole, M.

2008-01-01

Workers at NASA Ames Research center are endeavoring to develop durable, oxidation-resistant, foam thermal protection systems (TPSs) that would be suitable for covering large exterior spacecraft surfaces, would have low to moderate densities, and would have temperature capabilities comparable to those of carbon-based TPSs [reusable at 3,000 F (.1,650 C)] with application of suitable coatings. These foams may also be useful for repairing TPSs while in orbit. Moreover, on Earth as well as in outer space, these foams might be useful as catalyst supports and filters. Preceramic polymers are obvious candidates for use in making the foams in question. The use of these polymers offers advantages over processing routes followed in making conventional ceramics. Among the advantages are the ability to plastically form parts, the ability to form pyrolized ceramic materials at lower temperatures, and the ability to form high-purity microstructures having properties that can be tailored to satisfy requirements. Heretofore, preceramic polymers have been used mostly in the production of such low-dimensional products as fibers because the loss of volatiles during pyrolysis of the polymers leads to porosity and large shrinkage (in excess of 30 percent). In addition, efforts to form bulk structures from preceramic polymers have resulted in severe cracking during pyrolysis. However, because the foams in question would consist of networks of thin struts (in contradistinction to nonporous dense solids), these foams are ideal candidates for processing along a preceramic-polymer route.

Thermal/acoustical aircraft insulation material

NASA Technical Reports Server (NTRS)

Struzik, E. A.; Kunz, R.; Lin, R.

1975-01-01

Attempts made to improve the acoustical properties of low density Fiberfrax foam, an aircraft insulation material, are reported. Characterizations were also made of the physical and thermal properties. Two methods, optimization of fiber blend composition and modification of the foam fabrication process, were examined as possible means of improving foam acoustics. Flame impingement tests were also made; results show performance was satisfactory.

Partitioned airs at microscale and nanoscale: thermal diffusivity in ultrahigh porosity solids of nanocellulose

PubMed Central

Sakai, Koh; Kobayashi, Yuri; Saito, Tsuguyuki; Isogai, Akira

2016-01-01

High porosity solids, such as plastic foams and aerogels, are thermally insulating. Their insulation performance strongly depends on their pore structure, which dictates the heat transfer process in the material. Understanding such a relationship is essential to realizing highly efficient thermal insulators. Herein, we compare the heat transfer properties of foams and aerogels that have very high porosities (97.3–99.7%) and an identical composition (nanocellulose). The foams feature rather closed, microscale pores formed with a thin film-like solid phase, whereas the aerogels feature nanoscale open pores formed with a nanofibrous network-like solid skeleton. Unlike the aerogel samples, the thermal diffusivity of the foam decreases considerably with a slight increase in the solid fraction. The results indicate that for suppressing the thermal diffusion of air within high porosity solids, creating microscale spaces with distinct partitions is more effective than directly blocking the free path of air molecules at the nanoscale. PMID:26830144

Porous CoO nanostructures grown on three-dimension graphene foams for supercapacitors electrodes

NASA Astrophysics Data System (ADS)

Deng, Wei; Lan, Wei; Sun, Yaru; Su, Qing; Xie, Erqing

2014-06-01

Three-dimensional graphene foams with good conductivity, light weight and chemical stability were produced by chemical vapor deposition. Then porous CoO nanowalls were deposited on graphene foam by a simple hydrothermal process and subsequent thermal treatment. This hybrid structures possessing large surface area in which the CoO nanowalls are separated by graphene foam with robust adhesion can directly serve as supercapacitor electrode including current collector without the need of any other binder materials and conductive agents. Electrochemical tests manifest a high specific capacitance of 231.87 F/g scaled to the mass of CoO (139.47 F/g for total mass of electrodes) at 1 A/g current, good rate capability and excellent cycling performance of >98% capacitance retention over 1000 cycles at 7 A/g current. The high conductivity, light weight and rational architectures, which provide fast electron pathway and the low diffusion resistance of ions, are responsible for the high performance of the electrodes.

Modeling of reduced secondary electron emission yield from a foam or fuzz surface

DOE PAGES

Swanson, Charles; Kaganovich, Igor D.

2018-01-10

Complex structures on a material surface can significantly reduce the total secondary electron emission yield from that surface. A foam or fuzz is a solid surface above which is placed a layer of isotropically aligned whiskers. Primary electrons that penetrate into this layer produce secondary electrons that become trapped and do not escape into the bulk plasma. In this manner the secondary electron yield (SEY) may be reduced. We developed an analytic model and conducted numerical simulations of secondary electron emission from a foam to determine the extent of SEY reduction. We find that the relevant condition for SEY minimization ismore » $$\\bar{u}$$≡AD/2>>1 while D <<1, where D is the volume fill fraction and A is the aspect ratio of the whisker layer, the ratio of the thickness of the layer to the radius of the fibers. As a result, we find that foam cannot reduce the SEY from a surface to less than 0.3 of its flat value.« less

Modeling of reduced secondary electron emission yield from a foam or fuzz surface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Swanson, Charles; Kaganovich, Igor D.

Complex structures on a material surface can significantly reduce the total secondary electron emission yield from that surface. A foam or fuzz is a solid surface above which is placed a layer of isotropically aligned whiskers. Primary electrons that penetrate into this layer produce secondary electrons that become trapped and do not escape into the bulk plasma. In this manner the secondary electron yield (SEY) may be reduced. We developed an analytic model and conducted numerical simulations of secondary electron emission from a foam to determine the extent of SEY reduction. We find that the relevant condition for SEY minimization ismore » $$\\bar{u}$$≡AD/2>>1 while D <<1, where D is the volume fill fraction and A is the aspect ratio of the whisker layer, the ratio of the thickness of the layer to the radius of the fibers. As a result, we find that foam cannot reduce the SEY from a surface to less than 0.3 of its flat value.« less

Superlight, Mechanically Flexible, Thermally Superinsulating, and Antifrosting Anisotropic Nanocomposite Foam Based on Hierarchical Graphene Oxide Assembly.

PubMed

Peng, Qingyu; Qin, Yuyang; Zhao, Xu; Sun, Xianxian; Chen, Qiang; Xu, Fan; Lin, Zaishan; Yuan, Ye; Li, Ying; Li, Jianjun; Yin, Weilong; Gao, Chao; Zhang, Fan; He, Xiaodong; Li, Yibin

2017-12-20

Lightweight, high-performance, thermally insulating, and antifrosting porous materials are in increasing demand to improve energy efficiency in many fields, such as aerospace and wearable devices. However, traditional thermally insulating materials (porous ceramics, polymer-based sponges) could not simultaneously meet these demands. Here, we propose a hierarchical assembly strategy for producing nanocomposite foams with lightweight, mechanically flexible, superinsulating, and antifrosting properties. The nanocomposite foams consist of a highly anisotropic reduced graphene oxide/polyimide (abbreviated as rGO/PI) network and hollow graphene oxide microspheres. The hierarchical nanocomposite foams are ultralight (density of 9.2 mg·cm -3 ) and exhibit ultralow thermal conductivity of 9 mW·m -1 ·K -1 , which is about a third that of traditional polymer-based insulating materials. Meanwhile, the nanocomposite foams show excellent icephobic performance. Our results show that hierarchical nanocomposite foams have promising applications in aerospace, wearable devices, refrigerators, and liquid nitrogen/oxygen transportation.

Experimental study on cryogenic moisture uptake in polyurethane foam insulation material

NASA Astrophysics Data System (ADS)

Zhang, X. B.; Yao, L.; Qiu, L. M.; Gan, Z. H.; Yang, R. P.; Ma, X. J.; Liu, Z. H.

2012-12-01

Rigid foam is widely used to insulate cryogenic tanks, in particular for space launch vehicles due to its lightweight, mechanical strength and thermal-insulating performance. Up to now, little information is available on the intrusion of moisture into the material under cryogenic conditions, which will bring substantial additional weight for the space vehicles at lift-off. A cryogenic moisture uptake apparatus has been designed and fabricated to measure the amount of water uptake into the polyurethane foam. One side of the specimen is exposed to an environment with high humidity and ambient temperature, while the other with cryogenic temperature at approximately 78 K. A total of 16 specimens were tested for up to 24 h to explore the effects of the surface thermal protection layer, the foam thickness, exposed time, the butt joints, and the material density on water uptake of the foam. The results are constructive for the applications of the foam to the cryogenic insulation system in space launch vehicles.

A general patterning approach by manipulating the evolution of two-dimensional liquid foams

NASA Astrophysics Data System (ADS)

Huang, Zhandong; Su, Meng; Yang, Qiang; Li, Zheng; Chen, Shuoran; Li, Yifan; Zhou, Xue; Li, Fengyu; Song, Yanlin

2017-01-01

The evolution of gas-liquid foams has been an attractive topic for more than half a century. However, it remains a challenge to manipulate the evolution of foams, which restricts the development of porous materials with excellent mechanical, thermal, catalytic, electrical or acoustic properties. Here we report a strategy to manipulate the evolution of two-dimensional (2D) liquid foams with a micropatterned surface. We demonstrate that 2D liquid foams can evolve beyond Ostwald ripening (large bubbles always consuming smaller ones). By varying the arrangement of pillars on the surface, we have prepared various patterns of foams in which the size, shape and position of the bubbles can be precisely controlled. Furthermore, these patterned bubbles can serve as a template for the assembly of functional materials, such as nanoparticles and conductive polymers, into desired 2D networks with nanoscale resolution. This methodology provides new insights in controlling curvature-driven evolution and opens a general route for the assembly of functional materials.

Bio-based Polymer Foam from Soyoil

NASA Astrophysics Data System (ADS)

Bonnaillie, Laetitia M.; Wool, Richard P.

2006-03-01

The growing bio-based polymeric foam industry is presently lead by plant oil-based polyols for polyurethanes and starch foams. We developed a new resilient, thermosetting foam system with a bio-based content higher than 80%. The acrylated epoxidized soybean oil and its fatty acid monomers is foamed with pressurized carbon dioxide and cured with free-radical initiators. The foam structure and pore dynamics are highly dependent on the temperature, viscosity and extent of reaction. Low-temperature cure hinds the destructive pore coalescence and the application of a controlled vacuum results in foams with lower densities ˜ 0.1 g/cc, but larger cells. We analyze the physics of foam formation and stability, as well as the structure and mechanical properties of the cured foam using rigidity percolation theory. The parameters studied include temperature, vacuum applied, and cross-link density. Additives bring additional improvements: nucleating agents and surfactants help produce foams with a high concentration of small cells and low bulk density. Hard and soft thermosetting foams with a bio content superior to 80% are successfully produced and tested. Potential applications include foam-core composites for hurricane-resistant housing, structural reinforcement for windmill blades, and tissue scaffolds.

Hierarchical multiscale structure–property relationships of the red-bellied woodpecker (Melanerpes carolinus) beak

PubMed Central

Lee, Nayeon; Horstemeyer, M. F.; Rhee, Hongjoo; Nabors, Ben; Liao, Jun; Williams, Lakiesha N.

2014-01-01

We experimentally studied beaks of the red-bellied woodpecker to elucidate the hierarchical multiscale structure–property relationships. At the macroscale, the beak comprises three structural layers: an outer rhamphotheca layer (keratin sheath), a middle foam layer and an inner bony layer. The area fraction of each layer changes along the length of the beak giving rise to a varying constitutive behaviour similar to functionally graded materials. At the microscale, the rhamphotheca comprises keratin scales that are placed in an overlapping pattern; the middle foam layer has a porous structure; and the bony layer has a big centre cavity. At the nanoscale, a wavy gap between the keratin scales similar to a suture line was evidenced in the rhamphotheca; the middle foam layer joins two dissimilar materials; and mineralized collagen fibres were revealed in the inner bony layer. The nano- and micro-indentation tests revealed that the hardness (associated with the strength, modulus and stiffness) of the rhamphotheca layer (approx. 470 MPa for nano and approx. 320 MPa for micro) was two to three times less than that of the bony layer (approx. 1200 MPa for nano and approx. 630 MPa for micro). When compared to other birds (chicken, finch and toucan), the woodpecker's beak has more elongated keratin scales that can slide over each other thus admitting dissipation via shearing; has much less porosity in the bony layer thus strengthening the beak and focusing the stress wave; and has a wavy suture that admits local shearing at the nanoscale. The analysis of the woodpeckers' beaks provides some understanding of biological structural materials' mechanisms for energy absorption. PMID:24812053

Porous Ceramic Cures at Moderate Temperatures, Is Good Heat Insulator

NASA Technical Reports Server (NTRS)

Eubanks, Alfred G.; Hunkeler, Ronald E.

1965-01-01

The problem: To develop a foamed-in-place refractory material that would provide good thermal insulation, mechanical support, and vibration shielding for enclosed objects at temperatures up to 30000 F. The preparation of conventional foamed refractory materials required long curing times (as much as 48 hours) and high temperatures (at least 700 F), rendering such materials unusable for in-place potting of heat-sensitive components. The solution: A foamed ceramic material that has the requisite thermal insulation and strength, and also displays other properties that suggest a wide range of applications.

Materials for fire resistant passenger seats in aircraft

NASA Technical Reports Server (NTRS)

Tesoro, G.; Moussa, A.

1980-01-01

The paper considers the selection of cushioning foam and upholstery fabric materials for aircraft passenger seats. Polyurethane, polychloroprene, polyimide, and polyphosphazene are the foam materials considered; and a variety of commercial and developmental fabrics (including wool, cotton, synthetics, and blends) are examined. Viable approaches to the design of fire-resistant seat assemblies are indicated. Results of an experimental laboratory study of fabrics and fabric/foam assemblies exposed to external point-source radiative heat flux are discussed.

Method for forming porous sintered bodies with controlled pore structure

DOEpatents

Whinnery, LeRoy Louis; Nichols, Monte Carl

2000-01-01

The present invention is based, in part, on a method for combining a mixture of hydroxide and hydride functional siloxanes to form a polysiloxane polymer foam, that leaves no residue (zero char yield) upon thermal decomposition, with ceramic and/or metal powders and appropriate catalysts to produce porous foam structures having compositions, densities, porosities and structures not previously attainable. The siloxanes are mixed with the ceramic and/or metal powder, wherein the powder has a particle size of about 400 .mu.m or less, a catalyst is added causing the siloxanes to foam and crosslink, thereby forming a polysiloxane polymer foam having the metal or ceramic powder dispersed therein. The polymer foam is heated to thermally decompose the polymer foam and sinter the powder particles together. Because the system is completely nonaqueous, this method further provides for incorporating reactive metals such as magnesium and aluminum, which can be further processed, into the foam structure.

Ni foam supported quasi-core-shell structure of ultrathin Ti3C2 nanosheets through electrostatic layer-by-layer self-assembly as high rate-performance electrodes of supercapacitors

NASA Astrophysics Data System (ADS)

Tian, Yapeng; Yang, Chenhui; Que, Wenxiu; He, Yucheng; Liu, Xiaobin; Luo, Yangyang; Yin, Xingtian; Kong, Ling Bing

2017-11-01

Supercapacitor, as an important energy storage device, is a critical component for next generation electric power system, due to its high power density and long cycle life. In this study, a novel electrode material with quasi-core-shell structure, consisting of negatively charged few layer Ti3C2 nanosheets (FL-Ti3C2) and positively charged polyethyleneimine as building blocks, has been prepared by using an electrostatic layer-by-layer self-assembly method, with highly conductive Ni foam to be used as the skeleton. The unique quasi-core-shell structured ultrathin Ti3C2 nanosheets provide an excellent electron channel, ion transport channel and large effective contact area, thus leading to a great improvement in electrochemical performance of the material. The specific capacitance of the binder-free FL-Ti3C2@Ni foam electrodes reaches 370 F g-1 at the scan rate of 2 mV s-1 and a specific capacitance of 117 F g-1 is obtained even at the scan rate of 1000 mV s-1 in the electrolyte of Li2SO4, indicating a high rate performance. In addition, this electrode shows a long-term cyclic stability with a loss of only 13.7% after 10,000 circles. Furthermore, quantitative analysis has been conducted to ensure the relationship between the capacitive contribution and the rate performance of the as-fabricated electrode.

Fracture Toughness Evaluation of Space Shuttle External Tank Thermal Protection System Polyurethane Foam Insulation Materials

NASA Technical Reports Server (NTRS)

McGill, Preston; Wells, Doug; Morgan, Kristin

2006-01-01

Experimental evaluation of the basic fracture properties of Thermal Protection System (TPS) polyurethane foam insulation materials was conducted to validate the methodology used in estimating critical defect sizes in TPS applications on the Space Shuttle External Fuel Tank. The polyurethane foam found on the External Tank (ET) is manufactured by mixing liquid constituents and allowing them to react and expand upwards - a process which creates component cells that are generally elongated in the foam rise direction and gives rise to mechanical anisotropy. Similarly, the application of successive foam layers to the ET produces cohesive foam interfaces (knitlines) which may lead to local variations in mechanical properties. This study reports the fracture toughness of BX-265, NCFI 24-124, and PDL-1034 closed-cell polyurethane foam as a function of ambient and cryogenic temperatures and knitline/cellular orientation at ambient pressure.

Honeycomb vs. Foam: Evaluating Potential Upgrades to ISS Module Shielding

NASA Technical Reports Server (NTRS)

Ryan, Shannon J.; Christiansen, Eric L.

2009-01-01

The presence of honeycomb cells in a dual-wall structure is advantageous for mechanical performance and low weight in spacecraft primary structures but detrimental for shielding against impact of micrometeoroid and orbital debris particles (MMOD). The presence of honeycomb cell walls acts to restrict the expansion of projectile and bumper fragments, resulting in the impact of a more concentrated (and thus lethal) fragment cloud upon the shield rear wall. The Multipurpose Laboratory Module (MLM) is a Russian research module scheduled for launch and ISS assembly in 2011 (currently under review). Baseline shielding of the MLM is expected to be predominantly similar to that of the existing Functional Energy Block (FGB), utilizing a baseline triple wall configuration with honeycomb sandwich panels for the dual bumpers and a thick monolithic aluminum pressure wall. The MLM module is to be docked to the nadir port of the Zvezda service module and, as such, is subject to higher debris flux than the FGB module (which is aligned along the ISS flight vector). Without upgrades to inherited shielding, the MLM penetration risk is expected to be significantly higher than that of the FGB module. Open-cell foam represents a promising alternative to honeycomb as a sandwich panel core material in spacecraft primary structures as it provides comparable mechanical performance with a minimal increase in weight while avoiding structural features (i.e. channeling cells) detrimental to MMOD shielding performance. In this study, the effect of replacing honeycomb sandwich panel structures with metallic open-cell foam structures on MMOD shielding performance is assessed for an MLM-representative configuration. A number of hypervelocity impact tests have been performed on both the baseline honeycomb configuration and upgraded foam configuration, and differences in target damage, failure limits, and derived ballistic limit equations are discussed.

46 CFR 160.049-4 - Construction and workmanship.

Code of Federal Regulations, 2011 CFR

2011-10-01

... MATERIALS: SPECIFICATIONS AND APPROVAL LIFESAVING EQUIPMENT Specification for a Buoyant Cushion Plastic Foam... box type filled with unicellular plastic foam buoyant material. Such cushions consist essentially of a...

46 CFR 160.049-4 - Construction and workmanship.

Code of Federal Regulations, 2014 CFR

2014-10-01

... MATERIALS: SPECIFICATIONS AND APPROVAL LIFESAVING EQUIPMENT Specification for a Buoyant Cushion Plastic Foam... box type filled with unicellular plastic foam buoyant material. Such cushions consist essentially of a...

Oviduct modifications in foam-nesting frogs, with emphasis on the genus Leptodactylus (Amphibia, Leptodactylidae)

USGS Publications Warehouse

Furness, Andrew I.; McDiarmid, Roy W.; Heyer, W. Ronald; Zug, George R.

2010-01-01

Various species of frogs produce foam nests that hold their eggs during development. We examined the external morphology and histology of structures associated with foam nest production in frogs of the genus Leptodactylus and a few other taxa. We found that the posterior convolutions of the oviducts in all mature female foam-nesting frogs that we examined were enlarged and compressed into globular structures. This organ-like portion of the oviduct has been called a "foam gland" and these structures almost certainly produce the secretion that is beaten by rhythmic limb movements into foam that forms the nest. However, the label "foam gland" is a misnomer because the structures are simply enlarged and tightly folded regions of the pars convoluta of the oviduct, rather than a separate structure; we suggest the name pars convoluta dilata (PCD) for this feature. Although all the foam-nesters we examined had a pars convoluta dilata, its size and shape showed considerable interspecific variation. Some of this variation likely reflects differences in the breeding behaviors among species and in the size, type, and placement of their foam nests. Other variation, particularly in size, may be associated with the physiological periodicity and reproductive state of the female, her age, and/or the number of times she has laid eggs.

Compressive Behaviour and Energy Absorption of Aluminium Foam Sandwich

NASA Astrophysics Data System (ADS)

Endut, N. A.; Hazza, M. H. F. Al; Sidek, A. A.; Adesta, E. T. Y.; Ibrahim, N. A.

2018-01-01

Development of materials in automotive industries plays an important role in order to retain the safety, performance and cost. Metal foams are one of the idea to evolve new material in automotive industries since it can absorb energy when it deformed and good for crash management. Recently, new technology had been introduced to replace metallic foam by using aluminium foam sandwich (AFS) due to lightweight and high energy absorption behaviour. Therefore, this paper provides reliable data that can be used to analyze the energy absorption behaviour of aluminium foam sandwich by conducting experimental work which is compression test. Six experiments of the compression test were carried out to analyze the stress-strain relationship in terms of energy absorption behavior. The effects of input variables include varying the thickness of aluminium foam core and aluminium sheets on energy absorption behavior were evaluated comprehensively. Stress-strain relationship curves was used for energy absorption of aluminium foam sandwich calculation. The result highlights that the energy absorption of aluminium foam sandwich increases from 12.74 J to 64.42 J respectively with increasing the foam and skin thickness.

Industrial waste utilization for foam concrete

NASA Astrophysics Data System (ADS)

Krishnan, Gokul; Anand, K. B.

2018-02-01

Foam concrete is an emerging and useful construction material - basically a cement based slurry with at least 10% of mix volume as foam. The mix usually containing cement, filler (usually sand) and foam, have fresh densities ranging from 400kg/m3 to 1600kg/m3. One of the main drawbacks of foam concrete is the large consumption of fine sand as filler material. Usage of different solid industrial wastes as fillers in foam concrete can reduce the usage of fine river sand significantly and make the work economic and eco-friendly. This paper aims to investigate to what extent industrial wastes such as bottom ash and quarry dust can be utilized for making foam concrete. Foam generated using protein based agent was used for preparing and optimizing (fresh state properties). Investigation to find the influence of design density and air-void characteristics on the foam concrete strength shows higher strength for bottom ash mixes due to finer air void distribution. Setting characteristics of various mix compositions are also studied and adoption of Class C flyash as filler demonstrated capability of faster setting.

Stochastic metallic-glass cellular structures exhibiting benchmark strength.

PubMed

Demetriou, Marios D; Veazey, Chris; Harmon, John S; Schramm, Joseph P; Johnson, William L

2008-10-03

By identifying the key characteristic "structural scales" that dictate the resistance of a porous metallic glass against buckling and fracture, stochastic highly porous metallic-glass structures are designed capable of yielding plastically and inheriting the high plastic yield strength of the amorphous metal. The strengths attainable by the present foams appear to equal or exceed those by highly engineered metal foams such as Ti-6Al-4V or ferrous-metal foams at comparable levels of porosity, placing the present metallic-glass foams among the strongest foams known to date.

Determination of Time Required for Materials Exposed to Oxygen to Return to Reduced Flammability

NASA Technical Reports Server (NTRS)

Harper, Susana; Hirsch, David; Smith, Sarah

2009-01-01

Increased material flammability due to exposure to high oxygen concentrations is a concern from both a safety and operational perspective. Localized, high oxygen concentrations can occur when exiting a higher oxygen concentration environment due to material saturation, as well as oxygen entrapment between barrier materials. Understanding of oxygen diffusion and permeation and its correlation to flammability risks can reduce the likelihood of fires while improving procedures as NASA moves to longer missions with increased extravehicular activities in both spacecraft and off-Earth habitats. This paper examines the time required for common spacecraft materials exposed to oxygen to return to reduced flammability after removal from the increased oxygen concentration environment. Specifically, NASA-STD-6001A maximum oxygen concentration testing and ASTM F-1927 permeability testing were performed on Nomex 4 HT90-40, Tiburon 5 Surgical Drape, Cotton, Extravehicular Mobility Unit (EMU) Liquid-Cooled Ventilation Garment, EMU Thermal Comfort Undergarment, EMU Mosite Foam with Spandex Covering, Advanced Crew Escape Suit (ACES) Outer Cross-section, ACES Liquid Cooled Garment (LCG), ACES O2 Hose Material, Minicel 6 Polyethylene Foam, Minicel Polyethylene Foam with Nomex Covering, Pyrell Polyurethane Foam, and Zotek 7 F-30 Foam.

Multiobjective Topology Optimization of Energy Absorbing Materials

DTIC Science & Technology

2015-08-01

absorbing liner for equestrian helmets. Part I: layered foam liner . Mater Des 30(9):3405–3413 Sethian J, Wiegmann A (2000) Structural boundary design via...Army Research Laboratory Wildman RA, Weile DS (2007) Geometry reconstruction of conduct- ing cylinders using genetic programming. IEEE Trans Antennas

Rigid polyurethane foam – kenaf core composites for structural applications

USDA-ARS?s Scientific Manuscript database

Kenaf (Hibiscus cannabinus L.) is a fast growing summer annual crop with numerous commercial applications (fibers, biofuels, bioremediation, paper pulp, building materials, cover crops, and livestock forages). The stalks of the kenaf plants contain two distinct fiber types, bast and core fibers. The...

Insulating Foams Save Money, Increase Safety

NASA Technical Reports Server (NTRS)

2009-01-01

Scientists at Langley Research Center created polyimide foam insulation for reusable cryogenic propellant tanks on the space shuttle. Meanwhile, a small Hialeah, Florida-based business, PolyuMAC Inc., was looking for advanced foams to use in the customized manufacturing of acoustical and thermal insulation. The company contacted NASA, licensed the material, and then the original inventors worked with the company's engineers to make a new material that was better for both parties. The new version, a high performance, flame retardant, flexible polyimide foam, is used for insulating NASA cryogenic propellant tanks and shows promise for use on watercraft, aircraft, spacecraft, electronics and electrical products, automobiles and automotive products, recreation equipment, and building and construction materials.

Air Activated Self-Decontaminating Polydicyclopentadiene PolyHIPE Foams for Rapid Decontamination of Chemical Warfare Agents.

PubMed

McGann, Christopher L; Daniels, Grant C; Giles, Spencer L; Balow, Robert B; Miranda-Zayas, Jorge L; Lundin, Jeffrey G; Wynne, James H

2018-06-01

The threat of chemical warfare agents (CWA) compels research into novel self-decontaminating materials (SDM) for the continued safety of first-responders, civilians, and active service personnel. The capacity to actively detoxify, as opposed to merely sequester, offending agents under typical environmental conditions defines the added value of SDMs in comparison to traditional adsorptive materials. Porous polymers, synthesized via the high internal phase emulsion (HIPE) templating, provide a facile fabrication method for materials with permeable open cellular structures that may serve in air filtration applications. PolyHIPEs comprising polydicyclopentadiene (polyDCPD) networks form stable hydroperoxide species following activation in air under ambient conditions. The hydroperoxide-containing polyDCPD materials react quickly with CWA simulants, Demeton-S and 2-chloroethyl ethyl sulfide, forming oxidation products as confirmed via gas chromatography mass spectrometry. The simplicity of the detoxification chemistry paired with the porous foam form factor presents an exciting opportunity for the development of self-decontaminating filter media. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Simultaneous Noncontact Precision Imaging of Microstructural and Thickness Variation in Dielectric Materials Using Terahertz Energy

NASA Technical Reports Server (NTRS)

Roth, Don J.; Seebo, Jeffrey P.; Winfree, William P.

2008-01-01

This article describes a noncontact single-sided terahertz electromagnetic measurement and imaging method that simultaneously characterizes microstructural (egs. spatially-lateral density) and thickness variation in dielectric (insulating) materials. The method was demonstrated for two materials-Space Shuttle External Tank sprayed-on foam insulation and a silicon nitride ceramic. It is believed that this method can be used as an inspection method for current and future NASA thermal protection system and other dielectric material inspection applications, where microstructural and thickness variation require precision mapping. Scale-up to more complex shapes such as cylindrical structures and structures with beveled regions would appear to be feasible.

Thermal highly porous insulation materials made of mineral raw materials

NASA Astrophysics Data System (ADS)

Mestnikov, A.

2015-01-01

The main objective of the study is to create insulating foam based on modified mineral binders with rapid hardening. The results of experimental studies of the composition and properties of insulating foam on the basis of rapidly hardening Portland cement (PC) and gypsum binder composite are presented in the article. The article proposes technological methods of production of insulating foamed concrete and its placement to the permanent shuttering wall enclosures in monolithic-frame construction and individual energy-efficient residential buildings, thus reducing foam shrinkage and improving crack-resistance.

Uniformly coated highly porous graphene/MnO2 foams for flexible asymmetric supercapacitors

NASA Astrophysics Data System (ADS)

Drieschner, Simon; von Seckendorff, Maximilian; del Corro, Elena; Wohlketzetter, Jörg; Blaschke, Benno M.; Stutzmann, Martin; Garrido, Jose A.

2018-06-01

Supercapacitors are called to play a prominent role in the newly emerging markets of electric vehicles, flexible displays and sensors, and wearable electronics. In order to compete with current battery technology, supercapacitors have to be designed with highly conductive current collectors exhibiting high surface area per unit volume and uniformly coated with pseudocapacitive materials, which is crucial to boost the energy density while maintaining a high power density. Here, we present a versatile technique to prepare thickness-controlled thin-film micro graphene foams (μGFs) with pores in the lower micrometer range grown by chemical vapor deposition which can be used as highly conductive current collectors in flexible supercapacitors. To fabricate the μGF, we use porous metallic catalytic substrates consisting of nickel/copper alloy synthesized on nickel foil by electrodeposition in an electrolytic solution. Changing the duration of the electrodeposition allows the control of the thickness of the metal foam, and thus of the μGF, ranging from a few micrometers to the millimeter scale. The resulting μGF with a thickness and pores in the micrometer regime exhibits high structural quality which leads to a very low intrinsic resistance of the devices. Transferred onto flexible substrates, we demonstrate a uniform coating of the μGFs with manganese oxide, a pseudocapacitively active material. Considering the porous structure and the thickness of the μGFs, square wave potential pulses are used to ensure uniform coverage by the oxide material boosting the volumetric and areal capacitance to 14 F cm‑3 and 0.16 F cm‑2. The μGF with a thickness and pores in the micrometer regime in combination with a coating technique tuned to the porosity of the μGF is of great relevance for the development of supercapacitors based on state-of-the-art graphene foams.

Uniformly coated highly porous graphene/MnO2 foams for flexible asymmetric supercapacitors.

PubMed

Drieschner, Simon; Seckendorff, Maximilian von; Corro, Elena Del; Wohlketzetter, Jörg; Blaschke, Benno M; Stutzmann, Martin; Garrido, Jose A

2018-06-01

Supercapacitors are called to play a prominent role in the newly emerging markets of electric vehicles, flexible displays and sensors, and wearable electronics. In order to compete with current battery technology, supercapacitors have to be designed with highly conductive current collectors exhibiting high surface area per unit volume and uniformly coated with pseudocapacitive materials, which is crucial to boost the energy density while maintaining a high power density. Here, we present a versatile technique to prepare thickness-controlled thin-film micro graphene foams (μGFs) with pores in the lower micrometer range grown by chemical vapor deposition which can be used as highly conductive current collectors in flexible supercapacitors. To fabricate the μGF, we use porous metallic catalytic substrates consisting of nickel/copper alloy synthesized on nickel foil by electrodeposition in an electrolytic solution. Changing the duration of the electrodeposition allows the control of the thickness of the metal foam, and thus of the μGF, ranging from a few micrometers to the millimeter scale. The resulting μGF with a thickness and pores in the micrometer regime exhibits high structural quality which leads to a very low intrinsic resistance of the devices. Transferred onto flexible substrates, we demonstrate a uniform coating of the μGFs with manganese oxide, a pseudocapacitively active material. Considering the porous structure and the thickness of the μGFs, square wave potential pulses are used to ensure uniform coverage by the oxide material boosting the volumetric and areal capacitance to 14 F cm -3 and 0.16 F cm -2 . The μGF with a thickness and pores in the micrometer regime in combination with a coating technique tuned to the porosity of the μGF is of great relevance for the development of supercapacitors based on state-of-the-art graphene foams.

High strain rate behaviour of polypropylene microfoams

NASA Astrophysics Data System (ADS)

Gómez-del Río, T.; Garrido, M. A.; Rodríguez, J.; Arencón, D.; Martínez, A. B.

2012-08-01

Microcellular materials such as polypropylene foams are often used in protective applications and passive safety for packaging (electronic components, aeronautical structures, food, etc.) or personal safety (helmets, knee-pads, etc.). In such applications the foams which are used are often designed to absorb the maximum energy and are generally subjected to severe loadings involving high strain rates. The manufacture process to obtain polymeric microcellular foams is based on the polymer saturation with a supercritical gas, at high temperature and pressure. This method presents several advantages over the conventional injection moulding techniques which make it industrially feasible. However, the effect of processing conditions such as blowing agent, concentration and microfoaming time and/or temperature on the microstructure of the resulting microcellular polymer (density, cell size and geometry) is not yet set up. The compressive mechanical behaviour of several microcellular polypropylene foams has been investigated over a wide range of strain rates (0.001 to 3000 s-1) in order to show the effects of the processing parameters and strain rate on the mechanical properties. High strain rate tests were performed using a Split Hopkinson Pressure Bar apparatus (SHPB). Polypropylene and polyethylene-ethylene block copolymer foams of various densities were considered.

46 CFR 160.010-1 - Incorporation by reference.

Code of Federal Regulations, 2014 CFR

2014-10-01

... Specification, Plastic Material, Cellular Polyurethane, Foam-In-Place, Rigid (2 and 4 Pounds per Cubic Foot....mil/quicksearch/. (1) MIL-P-19644C, Military Specification, Plastic Molding Material (Polystyrene Foam...

46 CFR 160.010-1 - Incorporation by reference.

Code of Federal Regulations, 2013 CFR

2013-10-01

... Specification, Plastic Material, Cellular Polyurethane, Foam-In-Place, Rigid (2 and 4 Pounds per Cubic Foot....mil/quicksearch/. (1) MIL-P-19644C, Military Specification, Plastic Molding Material (Polystyrene Foam...

Development of analysis technique to predict the material behavior of blowing agent

NASA Astrophysics Data System (ADS)

Hwang, Ji Hoon; Lee, Seonggi; Hwang, So Young; Kim, Naksoo

2014-11-01

In order to numerically simulate the foaming behavior of mastic sealer containing the blowing agent, a foaming and driving force model are needed which incorporate the foaming characteristics. Also, the elastic stress model is required to represent the material behavior of co-existing phase of liquid state and the cured polymer. It is important to determine the thermal properties such as thermal conductivity and specific heat because foaming behavior is heavily influenced by temperature change. In this study, three models are proposed to explain the foaming process and material behavior during and after the process. To obtain the material parameters in each model, following experiments and the numerical simulations are performed: thermal test, simple shear test and foaming test. The error functions are defined as differences between the experimental measurements and the numerical simulation results, and then the parameters are determined by minimizing the error functions. To ensure the validity of the obtained parameters, the confirmation simulation for each model is conducted by applying the determined parameters. The cross-verification is performed by measuring the foaming/shrinkage force. The results of cross-verification tended to follow the experimental results. Interestingly, it was possible to estimate the micro-deformation occurring in automobile roof surface by applying the proposed model to oven process analysis. The application of developed analysis technique will contribute to the design with minimized micro-deformation.

Improved construction materials for polar regions using microcellular thermoplastic foams

NASA Technical Reports Server (NTRS)

Cunningham, Daniel J.

1994-01-01

Microcellular polymer foams (MCF) are thermoplastic foams with very small cell diameters, less than 10 microns, and very large cell densities, 10(exp 9) to 10(exp 15) cells per cubic centimeter of unfoamed material. The concept of foaming polymers with microcellular voids was conceived to reduce the amount of material used for mass-produced items without compromising the mechanical properties. The reasoning behind this concept was that if voids smaller than the critical flaw size pre-existing in polymers were introduced into the matrix, they would not affect the overall strength of the product. MCF polycarbonate (PC), polystyrene (PS), and polyvinyl chloride (PVC) were examined to determine the effects of the microstructure towards the mechanical properties of the materials at room and arctic temperatures. Batch process parameters were discovered for these materials and foamed samples of three densities were produced for each material. To quantify the toughness and strength of these polymers, the tensile yield strength, tensile toughness, and impact resistance were measured at room and arctic temperatures. The feasibility of MCF polymers has been demonstrated by the consistent and repeatable MCF microstructures formed, but the improvements in the mechanical properties were not conclusive. Therefore the usefulness of the MCF polymers to replace other materials in arctic environments is questionable.

An overview on the characterization and mechanical behavior of nanoporous Gold

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hodge, A M; Hayes, J R; Caro, J A

2005-09-13

In this paper we present what we believe are the most pressing issues in understanding the mechanical behavior of nanoporous foams. We have postulated that a gold foam presents the best candidate for a systematic study of nanoporous foams since it can be synthesized with a wide range of ligaments sizes and densities. We have also conducted preliminary tests that demonstrate (a) Au foams have a fracture behavior dictated by the ligament size, and (b) nanoporous Au is a high yield strength material. Thus, we have demonstrated the potential in developing nanoporous foams as a new class of high yieldmore » strength/low density materials.« less

Cryoinsulation Material Development to Mitigate Obsolescence Risk for Global Warming Potential Foams

NASA Technical Reports Server (NTRS)

Protz, Alison; Bruyns, Roland; Nettles, Mindy

2015-01-01

Cryoinsulation foams currently being qualified for the Space Launch System (SLS) core stage are nonozone- depleting substances (ODP) and are compliant with current environmental regulations. However, these materials contain the blowing agent HFC-245fa, a hydrofluorocarbon (HFC), which is a Global Warming Potential (GWP) substance. In August 2014, the Environmental Protection Agency (EPA) proposed a policy change to reduce or eliminate certain HFCs, including HFC-245fa, in end-use categories including foam blowing agents beginning in 2017. The policy proposes a limited exception to allow continued use of HFC and HFC-blend foam blowing agents for military or space- and aeronautics-related applications, including rigid polyurethane spray foams, but only until 2022.

Cardiovascular Computed Tomography Phantom Fabrication and Characterization through the Tailored Properties of Polymeric Composites and Cellular Foams

NASA Astrophysics Data System (ADS)

Hoy, Carlton F. O.

The overall objective of this thesis was to control the fabrication technique and relevant material properties for phantom devices designated for computed tomography (CT) scanning. Fabrication techniques using polymeric composites and foams were detailed together with parametric studies outlining the fundamentals behind the changes in material properties which affect the characteristic CT number. The composites fabricated used polyvinylidene fluoride (PVDF), thermoplastic polyurethane (TPU) and polyethylene (PE) with hydroxylapatite (hA) as additive with different composites made by means of different weight percentages of additive. Polymeric foams were fabricated through a batch foaming technique with the heating time controlled to create different levels of foams. Finally, the effect of fabricated phantoms under varied scanning media was assessed to determine whether self-made phantoms can be scanned accurately under non-water or rigid environments allowing for the future development of complex shaped or fragile material types.

Fabrication of low-crystalline carbonate apatite foam bone replacement based on phase transformation of calcite foam.

PubMed

Maruta, Michito; Matsuya, Shigeki; Nakamura, Seiji; Ishikawa, Kunio

2011-01-01

Carbonate apatite (CO(3)Ap) foam may be an ideal bone substitute as it is sidelined to cancellous bone with respect to its chemical composition and structure. However, CO(3)Ap foam fabricated using α-tricalcium phosphate foam showed limited mechanical strength. In the present study, feasibility of the fabrication of calcite which could be a precursor of CO(3)Ap was studied. Calcite foam was successfully fabricated by the so-called "ceramic foam" method using calcium hydroxide coated polyurethane foam under CO(2)+O(2) atmosphere. Then the calcite foam was immersed in Na(2)HPO(4) aqueous solution for phase transformation based on dissolution-precipitation reaction. When CaO-free calcite foam was immersed in Na(2)HPO(4) solution, low-crystalline CO(3)Ap foam with 93-96% porosity and fully interconnected porous structure was fabricated. The compressive strength of the foam was 25.6 ± 6 kPa. In light of these results, we concluded that the properties of the precursor foam were key factors for the fabrication of CO(3)Ap foams.

Electrically conductive composite material

DOEpatents

Clough, R.L.; Sylwester, A.P.

1989-05-23

An electrically conductive composite material is disclosed which comprises a conductive open-celled, low density, microcellular carbon foam filled with a non-conductive polymer or resin. The composite material is prepared in a two-step process consisting of first preparing the microcellular carbon foam from a carbonizable polymer or copolymer using a phase separation process, then filling the carbon foam with the desired non-conductive polymer or resin. The electrically conductive composites of the present invention has a uniform and consistent pattern of filler distribution, and as a result is superior over prior art materials when used in battery components, electrodes, and the like. 2 figs.

Electrically conductive composite material

DOEpatents

Clough, R.L.; Sylwester, A.P.

1988-06-20

An electrically conductive composite material is disclosed which comprises a conductive open-celled, low density, microcellular carbon foam filled with a non-conductive polymer or resin. The composite material is prepared in a two-step process consisting of first preparing the microcellular carbon foam from a carbonizable polymer or copolymer using a phase separation process, then filling the carbon foam with the desired non-conductive polymer or resin. The electrically conductive composites of the present invention has a uniform and consistent pattern of filler distribution, and as a result is superior over prior art materials when used in battery components, electrodes, and the like. 2 figs.

Electrically conductive composite material

DOEpatents

Clough, Roger L.; Sylwester, Alan P.

1989-01-01

An electrically conductive composite material is disclosed which comprises a conductive open-celled, low density, microcellular carbon foam filled with a non-conductive polymer or resin. The composite material is prepared in a two-step process consisting of first preparing the microcellular carbon foam from a carbonizable polymer or copolymer using a phase separation process, then filling the carbon foam with the desired non-conductive polymer or resin. The electrically conductive composites of the present invention has a uniform and consistant pattern of filler distribution, and as a result is superior over prior art materials when used in battery components, electrodes, and the like.

75 FR 18446 - Airworthiness Directives; The Boeing Company Model 747-100, 747-100B, 747-100B SUD, 747-200B, 747...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-04-12

... assemblies in the ECS with burned Boeing Material Specification (BMS) 8-39 polyurethane foam insulation. This... duct assemblies in the ECS wrapped with BMS 8-39 polyurethane foam insulation, a material of which the... electrical arc from igniting the BMS 8-39 polyurethane foam insulation on the duct assemblies of the ECS...

Mitigation of Oil in Water Column: Concept Development

DTIC Science & Technology

2016-06-01

Argonne National Laboratory (ANL) proposes to use polyurethane foam , a commonly used material for many general purposes, as the material of choice to...adsorb submerged oil. Prior to use, the foam undergoes a series of chemical processes in order to render it oleophilic and thus more susceptible to...17. Key Words Adsorbent Foam , Adhesion, Microbubble, Sinking Oil, Submerged Oil, Oil Mitigation, Sorbent, Water Column 18. Distribution Statement

Acoustic structure and propagation in highly porous, layered, fibrous materials

NASA Technical Reports Server (NTRS)

Lambert, R. F.; Tesar, J. S.

1984-01-01

The acoustic structure and propagation of sound in highly porous, layered, fine fiber materials is examined. Of particular interest is the utilization of the Kozeny number for determining the static flow resistance and the static structure factor based on flow permeability measurements. In this formulation the Kozeny number is a numerical constant independent of volume porosity at high porosities. The other essential parameters are then evaluated employing techniques developed earlier for open cell foams. The attenuation and progressive phase characteristics in bulk samples are measured and compared with predicted values. The agreements on the whole are very satisfactory.

46 CFR 164.015-1 - Applicable specifications and standards.

Code of Federal Regulations, 2010 CFR

2010-10-01

..., CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL MATERIALS Plastic Foam, Unicellular, Buoyant, Sheet... following specification and standard, of the issue in effect on the date the plastic foam material is...) ASTM D4986-98, Standard Test Method for Horizontal Burning Characteristics of Cellular Polymeric...

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, Wei-Yang

Foam materials are used to protect sensitive components from impact loading. In order to predict and simulate the foam performance under various loading conditions, a validated foam model is needed and the mechanical properties of foams need to be characterized. Uniaxial compression and tension tests were conducted for different densities of foams under various temperatures and loading rates. Crush stress, tensile strength, and elastic modulus were obtained. A newly developed confined compression experiment provided data for investigating the foam flow direction. A biaxial tension experiment was also developed to explore the damage surface of a rigid polyurethane foam.

Structure formation control of foam concrete

NASA Astrophysics Data System (ADS)

Steshenko, Aleksei; Kudyakov, Aleksander; Konusheva, Viktoriya; Syrkin, Oleg

2017-01-01

The process of predetermined foam concrete structure formation is considered to be a crucial issue from the point of process control and it is currently understudied thus defining the need for additional research. One of the effective ways of structure formation control in naturally hardening foam concrete is reinforcement with dispersed fibers or introduction of plasticizers. The paper aims at studying the patterns of influence of microreinforcing and plasticizing additives on the structure and performance properties of foam concrete. Preparation of foam concrete mix has been conducted using one-step technology. The structure of modified foam concrete has been studied by means of electron microscopy. The cellular structure of foam concrete samples with the additives is homogeneous; the pores are uniformly distributed over the total volume. It has been revealed that introduction of the Neolas 5.2 plasticizer and microreinforcing fibers in the foam concrete mixture in the amount of 0.4 - 0.1 % by weight of cement leads to reduction of the average pore diameter in the range of 45.3 to 30.2 microns and the standard deviation of the pore average diameter from 23.6 to 9.2 in comparison with the sample without additive. Introduction of modifying additives has stimulated formation of a large number of closed pores. Thus porosity of conditionally closed pores has increased from 16.06 % to 34.48 %, which has lead to increase of frost resistance brand of foam concrete from F15 to F50 and to reduction of its water absorption by weight by 20 %.

Technical characteristics of rigid sprayed PUR and PIR foams used in construction industry

NASA Astrophysics Data System (ADS)

Gravit, Marina; Kuleshin, Aleksey; Khametgalieva, Elina; Karakozova, Irina

2017-10-01

The article describes the distinctive properties of rigid polyurethane foam and polyisocyanurate (PUR and PIR). A brief review of the research was carried out on their modification with an objective to improve the thermal insulation properties and reducing the combustibility. A comparative analysis of the technical characteristics of rigid PUR and PIR foams of various manufacturers is presented. The problems of the state of the market for the production of polyurethane foam and polyisocyanurate in Russia have been marked. It is established that the further development of the fabrication technology of heat-insulating sprayed rigid PUR and PIR foams requires uniformity of technical characteristics of original components and finished products. Moreover, it requires the creation of unified information base for raw materials and auxiliary materials used in the production of PUR and PIR foam.