Single Foam Research Articles

Concussion History’s Impact On Instrumented Bess Scores In Division I Contact-Sport Athletes

PURPOSE: The purpose of this study was to determine if concussion history has an impact on sway velocity. A concussion injury can disrupt proper functioning of the vestibular system, and chronic disruption of this system can increase the chances of subsequent musculoskeletal or concussive injury. Athletes with a history of concussion injury who present with balance deficits, should be targeted for interventions to decrease the risk of sustaining a musculoskeletal or concussive injury. METHODS: 175 healthy Division I football & men’s lacrosse players (age = 19.8 ± 1.2; ht = 71.9 ± 2.2”; wt = 202.1 ± 33.9 lbs) participated in this study. Players were provided with a brief, 1-on-1, concussion discussion and then answered the questions “have you ever sustained a concussion? If yes, how many?”. All players underwent a balance assessment as part of their preseason screening and were medically cleared to participate in sports. Players performed the BESS test (double leg, single leg, & tandem) on firm & foam surfaces while standing on the VSR SportTM force plate by NeuroCom®. RESULTS: No difference was found between those with and without a previous concussion injury on any of the instrumented BESS stances (Table 1). To further analyze the data, a Spearman Rho correlation determined there was a smaller than typical correlation between number of concussions sustained and sway velocity measurements; double leg firm (rs = 0.02), single leg firm (rs = 0.09), tandem firm (rs = 0.08), double leg foam (rs = 0.01), single leg foam (rs = 0.01), tandem foam (rs = 0.02), & composite (rs = 0.06). CONCLUSION: Concussion history does not appear to have an impact on sway velocity measurements in contact sport athletes. The vestibulospinal system may be resilient to long-term deficits associated with concussion injury. In the absence of individualized baseline data, normative data may be used to determine balance deficits in those with a suspected concussion, regardless of previous concussion history.

Influence of cascaded graphite foams on thermal performance of high temperature phase change material storage systems

In this study, a numerical analysis is used to compare the effects of uniform and cascaded graphite foams on the charge–discharge cycle performance of thermal energy storage systems where a phase change material (PCM) with a phase change temperature of 855 K is used as the storage media. Firstly, for a constant PCM mass, the insertion of single graphite foams with respective porosities of 80%, 85%, 90% & 95% in the storage tank resulted to an exponential increase in the charge–discharge time. It was therefore concluded that a graphite foam with a porosity higher than 90% is less beneficial because the gradient of the porosity versus charge–discharge time graph becomes steeper. Secondly, for a constant PCM mass, graphite foams of porosity 80%, 85% and 90% were combined to obtain a cascaded porosity structure. The three foam structures were cascaded in such a way that the average porosity was either 85% or 89%. Overall, results obtained for cascaded porosity structures showed that combinations having a low porosity graphite foam near the cooling/heating wall performed better than their counterparts having a higher porosity foam near the heating/cooling wall. Particularly, the best combination at an average porosity of 85% and 89% accelerated the charge–discharge time by 5% and 4%, respectively, as compared to their respective single graphite foam cases.

Energy Absorption Analysis of aluminum Filled Foam Tube Under Axial Load using Finite Element Method with Cross Section Variations.

This study aims to determine the effect of the use of aluminum-filled foam tubes on crash boxes and the effect of cross-sectional variations in the use of aluminum-filled foam tubes on crash boxes. There are several parameters to determine crashworthiness performances such as energy absorption and deformation. Test specimens used are single walled (SW), single walled foam filled (SWFF), and double walled foam filled (DWFF), where DWFF is varied into 4 different wall thicknesses. All models have validated with experiment data from relevant reference and it evident that there are good agreement between simulation and experiment results. Tubes are impacted by rigid wall as impactor with velocity 0.4 m/s. From the simulation results, it was concluded that the aluminum crushbox construction added with aluminum foam is able to absorb more energy, where the recommended thickness is neither too thin nor too thick. Tube of DWFF 3 has energy absorption of 11.911 Joule, however the highest of deformation value is 178.66 mm for SWFF.

Electrochemical removal of gaseous elemental mercury in liquid phase with a novel foam titanium-based DSA anode

The dimensional stable Ti/Sb-SnO2/PbO2 electrode was prepared by the impregnation method. To remove gaseous elemental mercury (Hg0) from coal combustion, the study of Hg0 oxidation was performed in a gas diffusion electrochemical reactor with the stainless steel mesh cathode and the Ti/Sb-SnO2/PbO2 anode. Hg0 is oxidized into highly water-soluble oxidation states of mercury as a result of the loss of electrons on the anode, which can be removed later utilizing WFGD and other devices. By investigating the effects of applied voltage, the concentration and pH of the electrolyte, reaction temperature, flue gas flow and initial Hg0 concentration on removal, the appropriate conditions for the experiment were obtained. At the pH of 3, the removal efficiency can reach over 90%, which is about 1.7 times the removal of a single foam Ti under the same conditions.

Spring-like sandwich foam composites reinforced by 3D Concave–Convex structured fabric: Manufacturing and low-velocity cushion response

In order to solve the problems of poor mechanical properties and incapable reuse for single cellular foam, this study proposed low-cost spring-like sandwich flexible foam composites (SFFCs) with a 3D resilient concave–convex structured fabric core (RCFC) and two gradient-structured styrene-ethylene/butene–styrene copolymer (SEBS)-g-maleic anhydride (MAH)-filled polyurethane (PU) foam faces through two-step foaming. RCFC plied with different sizes and distances constituted warp-knitted spacer fabrics (WKSF) sealed between two layers of low-melting polyester nonwovens through thermal bonding. The effects of SEBS-g-MAH content and volume content of RCFC cubes on compression and dynamic low-velocity impact properties were explored at different impact energy levels. At 3:4 (wt%) ratio of the upper-to-lower SEBS-g-MAH content faces and at 0.4 ratio of WKSF-to-PU volume ratio, the resultant SFFCs showed a compression stress of 68.4 kPa (40%) and absorbed up to 98% of impact energy under 16 J. After five cycles of impact, this sandwich foam composite maintained 98% absorption of impact energy, demonstrating excellent spring-like dynamic-impact-recovery property. Overall, this study provided a novel structure design for lower cost, higher-performance recycling cushion materials in industrial construction, transport packaging, and sports fields.

Dynamic Stabilization of Foam Films with Acoustic Sound.

This paper demonstrates the stabilization of single foam films at dynamic conditions induced by exposure to the acoustic sound. The foam films were formed from aqueous solutions using a Sheludko cell. In the presence of sound at certain sound frequencies and above certain thresholds of sound amplitude, the lifetime of the film with 1 × 10-4 M sodium dodecyl sulfate (SDS) in the presence of 0.1 M NaCl was significantly increased, and a stabilization map was drawn to show the three levels of film stability (i.e., unstable, metastable, and stable) obtained over a broad range of sound frequencies (1-19 kHz) and amplitudes (74-125 dB). In particular, stable films were observed at relatively high frequencies (14-19 kHz) and high amplitudes (>107 dB) and metastable films were observed at intermediate frequencies (8.8-9.3 kHz) and high amplitudes (>111 dB). The stabilization effect was also demonstrated with different surfactants at different concentrations, at different electrolyte concentrations (in the presence and absence of the surfactant), and at different temperatures. Image analysis suggested the presence of liquid flow within the films that were stabilized by exposure to the acoustic sound. The stabilization effect could be attributed to the hydrodynamic pressure arising at dynamic conditions.

Effect of initial adsorption coverage and dynamic adsorption layer formation at bubble surface in stability of single foam films

The paper presents the experimental studies on influence of degree of initial adsorption coverage and structure of the dynamic adsorption layer over a rising bubble on stability of single foam films formed at surfaces of solutions of surface-active-substances namely n-octanol, n-hexadecyltrimethylammonium bromide (CTAB) and polyoxyethylenesorbitan monooleate (Tween80). Stability of single foam films formed by the colliding bubble under different experimental conditions were determined on the basis of systematic measurements of a single bubble lifetime in self-elaborated set-up. The experiments were supplemented by theoretical calculations of values of rupture thicknesses of the foam films, determined according to the Radove-Dimitrov-Ivanov model of drainage, which allows to consider formation of symmetrical and unsymmetrical foam films, depending on estimated structure of the dynamic adsorption layer. It was found that film lifetime depends strongly on the structure (stage of development) of motion-induced dynamic adsorption layer over the rising bubble surface. Moreover, it was shown that the bubble with completely different degree of initial adsorption coverage can form foam film of similar stability. This effect was attributed to the fact that eventual degree of the bubble adsorption coverage can reach comparable (and in some cases even equilibrium) value before film formation with identical structure of the DAL and degree of liquid/gas interface immobilization.

Unusual magnetotransport properties in graphene fibers.

Graphene, purely sp2-hybridized, has already been extensively studied for magnetoelectronics, however, the magnetotransport properties of graphene fibers (GrFib) have not been explored very well to date. Herein, unique magnetotransport properties of graphene fibers are detected. All the GrFib-samples show the highest positive magnetoresistance (MR ∼ 60%) at room temperature (300 K) that gradually decreases (MR ∼ 37%) at low temperature (5 K), indicating quite different behavior for a graphene derivative. The MR of three different morphologies are compared: single graphene sheet (60-100% at 300 K and 100-110% at 5 K under an applied magnetic field of 5 T), graphene foam (GF-100% at 300 K and 158% at 5 K under an applied magnetic field of 5 T), and graphene fiber (60% at 300 K and 37% at 300 K under an applied magnetic field of 5 T), and found that each morphology has a different magnitude of MR under similar magnitude of magnetic field and temperature. Unlike graphene and GF, GrFib shows a decreasing trend of MR at low temperatures, violating commonly used weak anti-localization phenomena in graphene. Technologically, each morphology of graphene has a unique set of magnetotransport properties that can be considered for particular magnetoelectronic devices depending upon the mechanical, electrical, and magnetotransport properties.

Effect of diesel on the froth stability and its antifoam mechanism in fine coal flotation used MIBC as the frother

Froth stability is one of the most important factors in fine coal flotation as it significantly affects the separation efficiency. Diesel is always used as the flotation collector while the effect of diesel on the froth stability is less investigated. In this study, effect of diesel on the froth stability and its antifoam mechanism in fine coal flotation used MIBC as the frother was investigated. Three-phase and two-phase froth stability tests were first carried out and the negative effect of diesel on froth stability was further explained by the single foam film drainage and spreading pressure experiments. The results of the three-phase dynamic froth stability showed that the maximum froth height and half-life of froth first increased and then decreased with the increase in diesel concentration. When diesel concentration increased to 8 kg/t, the maximum froth height and half-life of froth increased to 7.7 cm and 19 s. Deforming effect was observed when further increasing diesel dosage. Two-phase froth stability tests showed that the foaming ability and foam stability gradually decreased as the diesel concentration increased. When the diesel concentration increased from 0 to 20 and 40 ppm, the foam half-life decreased from 19 to 2.84 and 1.42 s, respectively. Single foam drainage tests showed that the diesel droplets dispersed into the middle of the foam film resulting in the formation of oil-bridge and rupture of the foam film. Meanwhile, the oil-film spreading pressure was found increased as the diesel concentration increased, directly indicating the antifoam effect of diesel. MIBC molecules were competitively adsorbed at diesel droplets, which reduced the effective concentration of the frother at the gas-water interface. Throughout this study, a certain defoaming effect of diesel on the froth stability in coal flotation was identified.

Simultaneous measurement of the thickness and the lifetime of a foam lamella.

Despite the important role of foams in industrial applications, few methods for determining the stability are present. By extending the existing light reflection-based apparatus, additional information about a single foam lamella can be obtained. Evaluation of these data delivers insight into the thinning process of the lamella. The potential of this technique is shown for the analysis of two surfactants with different head group lengths (Lutensol XP 100 and Lutensol XP 140).

Effect of NCO/OH ratio on physical and mechanical properties of castor-based polyurethane grouting materials

This research focused on fabrication of castor-based PU grout (CPUG) using castor oil with OH value of 161 mg/KOH/g and MDI with NCO content of 31%. The effect of different NCO/OH ratio on the foam reaction time, density, rheology, morphological and mechanical properties were investigated. The result shows that the rise time of CPUG decreased while tack free time increased with the increased of NCO/OH ratio. Morphological properties shows that CPUG consist of closed cell of foams and the diameter of a single cell foam decreased with the increased of NCO/OH ratio. The apparent density, rheology index, flexural strength, flexural modulus and compression strength of CPUG increased with the increasing NCO/OH ratio. CPUG’s apparent density was in the range of 230.23 kg/m3 while rheology index of CPUG was between 1.74 to 2.43 cm/g. Both values obtained were in the range of industrial PU grout’s density and rheology index (214 kg/m3 & 1.48 cm/g). CPUG4 give the best flexural and compression strength with a value of 11.01Mpa and 2Mpa respectively. Flexural and compression strength of CPUG were tantamount to the industrial PU grout’s properties which the average of flexural strength and compression strength were about 7.4MPa and 2MPa respectively.

CO2/N2 switchable aqueous foam stabilized by SDS/C12A surfactants: Experimental and molecular simulation studies

A novel CO2/N2 switchable aqueous foam was developed using a CO2-responsive surfactant N,N-dimethyl-N-dodecyl amine (C12A) and a conventional surfactant sodium dodecyl sulfate (SDS). The performance and mechanism of this switchable foam were studied by both experiment and molecular simulation methods. Experimental results demonstrate that the foam stabilized by SDS/C12A surfactants has better stability and water carrying capacity than single C12A foam. The foam could be rapidly switched between stable and unstable states at ambient temperature with CO2 or N2 as the triggers. Simulation results shows that when CO2 was introduced, most of SDS and C12A molecules aggregated in the water phase, instead of adsorbing at the air-water interface to stabilize the foam films. The strong electrostatic attraction between protonated C12A and SDS molecules could account for the aggregation. Due to the presence of limited surfactants located at the air-water interface after introducing CO2, the foam bursts quickly.

Experimental research on damage characteristics of CFRP/aluminum foam sandwich structure subjected to high velocity impact

In view of the wide demands of sandwich structure with porous material as core layer in many important fields such as protection engineering, aerospace, automobile manufacturing and ship, etc. In order to reveal the energy absorption and damage characteristics of high velocity impact aluminum foam core and CFRP/aluminum foam core structure, the quasi-static loading system, one-stage light gas gun loading system, the impact pressure testing system and the high-speed camera acquisition system were used to perform the quasi-static compression experiments of aluminum foam and the projectiles with different materials impacting on the aluminum foam core and CFRP/aluminum foam sandwich structure at the speeds of 100–300 m/s. The influences of impact velocity and projectile’ density on the damage characteristics of CFRP/aluminum foam sandwich structure and the attenuation effect of shock wave in sandwich structure have been studied. The experimental results showed that the curve of stress and strain has three typical zones similar to porous materials: elastic zone, yield platform zone and compaction zone under quasi-static compression loading. Due to its brittle and low tensile strength of aluminum foam material, the single aluminum foam plate has poor ballistic performance under the high-speed impact of projectiles with different materials. Therefore, closed cell aluminum foam needs to be combined with high strength panels to form sandwich structure to improve its ballistic performance.

Surface rheological measurements of isolated food foam systems

Liquid foams represent a key component to a vast range of food industry products, from ice creams to the crema on coffee. Longevity of these foams is a highly desirable attribute; however, in order for foam stability to be effectively controlled, a better understanding of the interdependence of the bulk liquid and air-liquid interfacial rheologies is required. This study follows an increasing trend in experimental investigations made of isolated foam structures at the microscale, where the bulk and surface dynamics of a single foam liquid channel can be accurately assessed. Isolated foam channels with adjoining nodes were studied for aqueous solutions of four food grade surfactants. Existing observations of distortions to sodium dodecyl sulphate channel geometries were confirmed for solutions of Tween 20 (T20) and Tween 80 (T80) and were well described by the theory presented here. Moreover, previously unseen distortions to liquid channels were observed for polymeric surfactant systems (hydroxypropyl methylcellulose and hydrolyzed pea protein blend), which were proposed to result from their high surface viscosities. The apparent surface viscosities, μs, of surfactants tested here ranged from high (10 g/s < μs < 10−3 g/s) for polymeric surfactants to very low (10−10 g/s < μs < 10−8 g/s) for Tweens, clearly demarking the regimes of viscous and inertial dominant flows, respectively. It is recommended that further work seeks to investigate the finding of a strong correlation between μs and channel surface tension, γ, for soluble surfactant systems, which could explain the apparent non-Newtonian values of μs that were consistently measured here.

Single steel strut mechanical testing: challenges and future research directions

ABSTRACTOpen-cell stainless steel foams, composed of hollow struts, are excellent candidates for energy absorption and thermo-mechanical applications. The basic mechanical element responsible for the function of these foams is the single strut. However, testing and characterisation of single foam struts to predict the foam strength have stirred up a new debate about approaches to micro-tensile testing of such elements. In this paper, we present a protocol for in-situ micro-tensile testing of hollow steel struts using a custom-made grip system. The adapted grips make it possible to perform analysis of the deformation of multiple sintered struts. Here we present and discuss challenges encountered during such micro-tensile testing of hollow steel struts.

On the effects of microstructure on the mechanical properties of open-pore Al–11Zn foams

The mechanical properties of investment casted open-pore metal foams have been investigated on the example of the binary alloy Al–11Zn. The samples were subjected to different cooling conditions subsequent to casting and to different homogenization and ageing treatments. Variation in cooling was done either by quenching the mold in water or slowly cooling it in air. Homogenization and ageing varied in terms of temperature and time. The effects of the different treatments were investigated through microstructural and mechanical characterization methods. Using TEM, we found that the presence of GP zones and their morphological arrangement are the main factors dominating the mechanical performance. Micro- and nanoindentation testing of single foam struts reveal maximum hardness H when room temperature ageing was applied. Ageing at a temperature of 150 °C results in the lowest H in the present study; that is approximately 2/3 of the hardness achieved when ageing at room temperature. This can also be confirmed by the strength of non-porous bulk material obtained by tensile tests, which further show an increase in ductility up to a factor of 5 due to ageing at elevated temperatures. By compression testing of open-pore Al–11Zn foams, we notice that the presence of the microstructural effects varies in extent as a function of the strain ε. At low strains, we observe differences in mechanical performance to a high extent, becoming less with increasing compaction of the samples until they behave as non-porous bulk material. Based on these findings, we deduce a strong interaction of the structural morphology of the foam and its microstructure that determines the mechanical properties dominated by strength and ductility of the base material.

Numerical study on impact resistance of double-layer aluminum foam curved sandwich plates

The dynamic response of curved sandwich plates with double-layer aluminum foam under impact loading is simulated by LS-DYNA finite element software. The impact resistance of single and double layers aluminum foam curved sandwich plates with the same thickness is compared. The influence of the thickness of the face-sheet and the thickness of the core layer on the deformation and energy absorption capacity of the double-layer sandwich structure is analyzed. The results show that the overall mechanical properties of the double-layer curved sandwich plates are better than those of the single layer curved sandwich plates with equal thickness; the thin front and middle plates can improve the energy absorption efficiency of the aluminum foam core, thereby enhancing the impact resistance of the sandwich structure; Increasing the thickness of the upper and lower core layers can improve the deformation of the double-layered curved sandwich plates, but the overall energy dissipation of the structure is reduced, and the upper core is the main energy absorbing component. The research results have some guiding significance for the application and optimization design of curved sandwich plates with double-layer aluminum foam in practical engineering.

Deformation Behaviour of Single and Gradient Density Natural Rubber Foams

Abstract The deformation behaviour of single and gradient density natural rubber (NR) foams produced from dry natural rubber have been investigated through experimentation and simulation. Different concentrations of a sodium bicarbonate blowing agent (BA) from 4phr to 16phr were utilized to produce different cell sizes and densities. The gradient density foams were fabricated by stacking the ∼ 20 mm layer of single density foam with several layers of foams having different relative densities ranging from 0.341 to 0.185. The mechanical properties and deformation behaviors of the foams were investigated through compression test and digitally-captured progressive deformation images. The models of the foam structures were constructed for simulation study via Finite Element Analysis (FEA) to investigate the cell elastic strain deformation. The results showed that the densities of polymeric foams were crucial in determining the foams compressive stress-strain behaviors. The NR foams with a higher density exhibited the greatest compressive strength properties, and the study also found that the foam cells in the middle section experienced the most cell deformation which expected due to higher stress concentration generated in this section. Further investigation on the gradient density foams structure showed that the foam layer with the lowest density undergoes the most cell deformation, regardless of the layer position in the structure.

Solar Powder Metallurgy: Preparation of TiC – TiB2 Ceramic Foam

The solar powder metallurgy was used to prepare TiC–TiB2 ceramic foams in 40kW horizontal solar furnace at Plataforma Solar de Almeria (PSA), Spain. The foams were prepared using self-propagating high-temperature synthesis from the green compacts of powder mixture of Ti + 15 vol.% B4C. The foaming was performed under protective argon atmosphere at various heating rates. It was shown that it is possible to prepare successfully TiC–TiB2 ceramic foams with porosity around 45%. The foaming temperature or ignition temperature was found to be around 1380 °C. The optimal heating rate for foam preparation was found to be 220°C/min. It was confirmed that 2 pieces of precursor will join successfully to create single foam. Further, graphite and alumina moulds were tested for possible preparation of 3D shapes. The EDS investigations confirmed the creation of TiB2, TiC and complex TiBxC1-x phases.

Impact response and energy absorption of single phase syntactic foam

Abstract This study experimentally investigates the static and impact response of a new single phase syntactic foam which has been newly developed for impact energy absorption. The syntactic foam had different densities ranging from 172 kg/m3 to 366 kg/m3 depending on the thickness and composition of the coating layers. The impact response and impact energy absorption were investigated by using instrumented drop-weight impact tests. Under static loads, the mechanical properties of the syntactic foam including the compressive strength, the yield stress, and Young's modulus increased with the density but the rate of increment decreased at higher densities. There were two types of progressive failures of the syntactic foam under impact loads. The failure propagation was examined and found to be dependent on the material density and the impact velocity. Interestingly, the densification only occurred in the low-density specimens while this phenomenon was not observed for the specimens with the density greater than 288 kg/m3. The impact energy absorption capacity increased significantly with the density and the wall thickness of the macrospheres.