Compressed Foam Research Articles

Experimental Research on Foam Concrete with Partial Replacement of Fine Aggregates by Blast Furnace Slag, Fly Ash, and Glass Powder

Aerated concrete blocks are made according to the design proportions in this project. Cement, fine particles, a foaming agent, and water are the ingredients of foam concrete. Sand prices are significantly rising these days. We may lower the cost of sand by replacing it with a replacement material. In the current investigation, sand is partially substituted by varying weights and quantities of blast furnace slag, fly ash, and glass powder. To gain a better understanding of the utilization of blast furnace slag, Fly Ash, and glass powder in various literatures, their impact on Compressive Strength foam concrete is explored.

Experimental study on the dynamic compression of materials at XGIII facility by laser proton photography

A new method for material dynamic density measurement based on proton photography is developed at XGIII facility. The protons produced by the picosecond laser of XGIII was used as the proton source to diagnose the density distribution of lattice foam under the compression of the nanosecond beam of XGIII. The density of lattice foam was calculated from the photographic results using Monte Carlo simulation method. Benefitting fromn this newly developed method, the images of the compressed lattice foam and the shock front at 5.2 ns is obtained successfully. The density distribution of the lattice foam was obtained from the images and the density of lattice foam increases about 20 times at the shock front due to the compression of the shock. The velocity of shock wave in lattice foam is also given, about 40 km/s. The density and spatial resolution of the method are further calibrated by using diamond step objects, and experimental results show that they are better than 4% and 12 <i>μ</i>m, respectively. In order to further improve the density and spatial resolution of the proton photography at XGIII facility, a new radiogrphy method utilizing quasimonoenergetic proton beams obtained from an energy selector is proposed in this paper, and the resolution of this method is simulated by Monte Carlo program. The simulation results show that the relative density resolution can be improved to more than 1%. Through the above experimental and the simulation results, we demonstrated that diagnostic capability has been established for fast process (nanosecond scale), high pressure (nearly 100 GPa) conditions at XGIII facility.

Effects of temperature and thermal cycles on the mechanical properties of expanded polystyrene foam

Understanding the effects of high temperature and thermal cycles on the mechanical properties of expanded polystyrene (EPS) foam is critical for its use in sandwich panels. This paper presents an experimental investigation of these effects in typical environmental conditions that exist in construction applications. A total of 117 small specimens were cut from metal-faced sandwich panels with EPS core and were exposed to different numbers of thermal cycles and/or sustained high temperatures. The specimens were then loaded under compression, tension, and four-point bending for evaluating the degradation of the mechanical properties of the foam. The thermal cycles reflect typical surface temperature during daily summer conditions, with a period of 24 h each and with a temperature varying between 24°C to 80°C. The results show that the modulus of elasticity of EPS foam in compression reduced by about 38% after exposure to thermal cycles for 45 days, whereas the tensile and shear moduli reduced by about 5.7% and 13.8%, respectively. Exposure to sustained high temperature after thermal cycles led to larger degradation of the elastic and shear moduli in the range of 38%–50%. These degradations can lead to early failures in applications that rely on the EPS foam as a structural component like in insulating sandwich panels.

Development and investigation of the applicability of computed tomography data-based modelling technique for polymeric high-density foams

As foams have become very important in several areas and since characterizing their properties is a crucial task, a finite element simulation model for high-density closed cell foams based on computed tomography (CT) measurements is developed. The model includes realistic microstructural features like cell size distribution due to the utilization of CT data. Moreover, a ‘skin-core-skin’ microstructure resulting from the manufacturing process (injection moulding) of the foams is also considered in the model. The mechanical behaviour of the foam’s core layer under tension and compression load is characterized based on the microstructural model to develop constitutive material models of the foam. These constitutive models enable further mechanical characterization of the foam with less computational effort. Compression and bending test simulations of injection moulded foams with three different densities are validated with corresponding experimental results. Thus, conclusions can be drawn regarding the reliability, applicability and possible further extensions of the high-density foam model.

Prediction and analysis of annular pressure caused by temperature effect for HP/HT/HHS and water production gas wells in Sichuan Basin

For the “three-high” gas wells in Sichuan Basin which are often regulated for production rate and shut-in for maintenance, annular pressure by temperature effect is a kind of wellbore safety threat that cannot be ignored. In this work, the wellbore temperature and pressure calculation model of gas–liquid two-phase flow with non-hydrocarbon correction and the prediction model of annular pressure by temperature effect is developed. Moreover, the judgment chart of annular pressure type is established through a large number of simulation calculations with different gas production rates and water production rates. Example calculation shows that whether water production and non-hydrocarbon components are considered in the prediction model has a non-negligible influence on calculation results. The predicted annular pressure is compared with that obtained from the actual measurement showing a good agreement. Meanwhile, the judgment chart realizes the valid determination of annular pressure type for three “three-high” gas wells in Sichuan Basin. Influential factors analysis indicates that reducing the thermal expansion coefficient of annulus fluid, adding the hollow glass spheres or injecting highly compressible protective liquid into the annulus and installing compressible foam material on the inner wall of casing are effective methods to control the annular pressure by temperature effect. To reserve partial annulus space can effectively reduce the annular pressure by temperature effect. For most of “three-high” gas wells in Sichuan Basin, the optimum height of annulus air cavity is 100 m.

Investigation on strength and failure behavior of ceramic foams prepared from silicoaluminous industrial waste under uniaxial compression

This paper experimentally investigated the compressive strength-porosity and compressive strength-bulk density dependence of ceramic foams fabricated using coal bottom ash (CBA), bauxite residue, and low-grade albite. The compressive stress-strain curves of ceramic foams with different bulk densities under pressure were compared to reveal the difference of their fracture mechanisms. The compressive strength-porosity trend of CBA foamed ceramics with a porosity range of 68-87% complied with the Rice model and could be expressed by an exponential equation σf=53852.28×exp-0.105P. However, for the porosity levels exceeding 90%, a linear equation σf=54.33-0.57P was provided the most accurate data fitting. The compressive strength-bulk density dependence of ceramic foams also satisfied the Gibson-Ashby model expressed by σf=73.54ρ∗3/2-26.64ρ∗. Finally, the variation of fracture mechanisms of compressed ceramic foams with their bulk density was revealed. Under one-dimensional compression stress, low-density ceramic foams (ρ ≤ 0.40 g/cm3) underwent plastic-like deformation, while high-density ones (ρ ≥ 0.60 g/cm3) exhibited brittle fracture behavior.

Shock Wave Mediation by Closed-Cell Aluminum Foams

Closed-cell aluminum foams of density 0.3 to 0.46 g/cc (1 g/cc=1,000 kg/m3) were exposed to incident shock waves of 10–11 bar (1 bar=1.01325×105 N/m2) pressure in a shock tube to study the shock-induced stress on the end wall, which was measured using a fast-response polyvinylidene difluoride (PVDF) sensor. The experimental results revealed amplification of the end-wall stress by 2.5 to 4 times compared to pressure exerted on the front surface of the foams. Shock compression of foams is discussed based on the stress history output of the PVDF. The properties of the densified foam samples, the particle and plastic wave speeds in foams, based on theory, are presented. A numerical analysis of loading the foams with shocks was conducted using Abaqus software to complement the experimental results. The numerical prediction of the end-wall stress also suggests stress amplification by a factor of 2.6 to 3.4. The information can be useful to designers of shock attenuators and defense shields using aluminum foams.

Impact behavior of natural rubber based syntactic foam core sandwich structures

Abstract In this study, the impact behavior of sandwich panels of natural rubber-based syntactic foam cores with aluminum face sheets was investigated experimentally and with the help of finite element analysis (FEA). Syntactic foam cores were produced byadding glass bubbles (GB) to the natural rubber (NR). Natural rubber was dissolved at room temperature with chemical solvents mixed with glass bubbles at 10, 20, and 30 weight percentages. Very low density (~0.8 g × cm-3) and high compressible foams were obtained depending on the GB weight percentages. Aluminum face sheets and the NR/GB syntactic foam core developed were joined by adhesive bonding to produce sandwich beam specimens. The sandwich beams manufactured in this way were subjected to impact loading under three-point bending boundary conditions experimentally. The experimental results were compared with finite element simulation results under the same loading and boundary conditions. The damage mechanism of the sandwich panels devised were analyzed. According to the results, natural rubber containing an additive of 20 wt.-% GBs showed better impact resistance than the others.

Mechanical behaviour in shear and compression of polyurethane foam at elevated temperature

This paper presents an experimental investigation about the effect of elevated temperature on the mechanical properties of two polyurethane (PUR) foams, with densities of 40 kg/m3 and 93 kg/m3. The experimental campaign included shear and compressive tests over a temperature range of 20°C–200°C, performed to assess the degradation of the mechanical properties of the PUR foams with temperature. To validate the diagonal tension shear test method adopted in this investigation, a numerical study was also performed, namely to assess the (shear) stress state developed within the foam. The results obtained validated the adopted test procedures, showing that the compressive and shear responses are strongly affected by elevated temperature, due to the softening of the polymeric material when it undergoes the glass transition process. For the temperature range considered in this study, both strength and modulus in shear and compression present an approximately linear reduction with temperature.

Functional Wood–Foam Composites for Controlled Uptake and Release

Wood–foam hierarchical composites were produced via the shear-forced infiltration of shear-thinning nanocellulose-based foams or gels into the tracheids of Picea abies. Shear processing viscoelastic and shear-thinning aqueous foams composed of cellulose nanocrystals, methylcellulose, and tannic acid (total solids content: 2 wt %) resulted in foam-filled wood composites containing 15–20 wt % foam, with open foam structures and compression strengths similar to those of unmodified P. abies. An amino-functionalized nanocellulose-containing foam confined in wood reversibly adsorbed CO2, retaining 15% of its theoretical uptake capacity over 50 cycles in the thermogravimetric analyzer, and a citronellol-loaded foam released this mosquito-repellent compound over four days, as evaluated using solid-phase microextraction. Shear-forced infiltration of functional foams into wood is an operationally simple route to hierarchically porous composites based on renewable materials.

Comparison of Gaseous and Water-Based Medium-Expansion Foam Depopulation Methods in Cull Sows.

Simple SummaryIn the face of a swine health crisis, emerging zoonotic diseases or environmental catastrophe, the mass depopulation of swine may be required to prevent the additional spread of disease and to minimize animal pain or suffering. Due to the increasing risk of global disease outbreaks, the U.S. swine industry needs feasible guidelines in place in preparation for such events. Current American Veterinary Medical Association (AVMA) approved swine depopulation methods can be difficult to implement under field conditions. Emergency depopulation using inhalants such as carbon dioxide (CO2) and nitrogen gas (N2) or the use of aspirated foam agents have been approved and conducted in poultry in the US, but are not approved for use in other livestock. Our findings, using cull sows, demonstrate that although CO2, N2 and aspirated foam combinations successfully killed all the animals, CO2 and aspirated foam did so in the shortest timeframe. In addition, the use of aspirated foam was as effective as CO2 for sow depopulation while having potential operational advantages, such as no use of lethal gases and reduced risk of associated equipment failure.The U.S. swine industry is currently inadequately prepared to counteract the increasing threat of high-consequence diseases. Although approved and preferred depopulation guidelines exist, ventilation shutdown (VSD+) is currently the only method being deployed during a state of emergency to depopulate large swine populations. However, the permitted use of VSD+ during constrained circumstances has been criticized due to raised swine welfare concerns. The objective of this study was to investigate the effectiveness of carbon dioxide gas (CO2), nitrogen gas (N2), compressed air foam (CAF), compressed nitrogen foam (CAF-N2) and aspirated foam (AF) during a 15-min dwell time on adult swine in an emergency depopulation situation. A small-scale trial using 12 sows per depopulation method showed the highest efficiency to induce cessation of movement for AF and CO2 (186.0 ± 48 vs. 202.0 ± 41, s ± SD). The ease of implementation and safety favored AF for further investigation. A large-scale field study using AF to depopulate 134 sows in modified rendering trailers showed a mean fill time of 103.8 s (SD: 5.0 s) and cessation of movement of 128.0 s (SD: 18.6 s) post filling. All sows were confirmed dead post-treatment for both trials. The implementation of AF in modified rendering trailers may allow for a safe and reliable method that allows for the expedient and mobile depopulation of both small and large numbers of sows during an emergency.

Microscopic and macroscopic instabilities in elastomeric foams

The present work is a thorough study on the elastic instabilities of flexible polymeric foams under compression. Tessellation-based topologies are employed to generate micromechanical models of open-cell random foams with controlled morphologies. Solid distribution on the resulting topologies is assigned based on a closed-form expression for the relative density that accounts for material overlap at the nodes. Simulations of foams with different microstructures are used to first reproduce experimentally obtained results, and subsequently to elucidate the connection between microstructure and the corresponding buckling mode. Compression of an anisotropic foam along the rise and transverse directions displays two distinct buckling modes that have previously been reported experimentally: a long-wavelength instability corresponding to a limit-load type response, and a microscopic instability that produces a monotonically increasing nonlinear response. The presence of large cell size distributions, i.e. polydispersity, is shown to also lead to a monotonic response, which is associated with the increased compaction of the largest cells that are present within the domain. The agreement between experimental and numerical responses is very favorable. The critical stresses are subsequently calculated as a function of key microstructural characteristics including foam density, anisotropy, cell-size distributions and ligament uniformity. The results indicate that a strong amount of anisotropy is needed for the transition from a microscopic instability to the macroscopic one while polydisperse foams produce a stable monotonic response, even in the presence of cell anisotropy.

Highly Insulative PEG-Grafted Cellulose Polyurethane Foams-From Synthesis to Application Properties.

In this paper, native cellulose I was subjected to alkaline treatment. As a result, cellulose I was transformed to cellulose II and some nanometric particles were formed. Both polymorphic forms of cellulose were modified with poly(ethylene glycol) (PEG) and then used as fillers for polyurethane. Composites were prepared in a one-step process. Cellulosic fillers were characterized in terms of their chemical (Fourier transformation infrared spectroscopy) and supermolecular structure (X-ray diffraction), as well as their particle size. Investigation of composite polyurethane included measurements of density, characteristic processing times of foam formation, compression strength, dimensional stability, water absorption, and thermal conductivity. Much focus was put on the application aspect of the produced insulation polyurethane foams. It was shown that modification of cellulosic filler with poly(ethylene glycol) has a positive influence on formation of polyurethane composites—if modified filler was used, the values of compression strength and density increased, while water sorption and thermal conductivity decreased. Moreover, it was proven that the introduction of cellulosic fillers into the polyurethane matrix does not deteriorate the strength or thermal properties of the foams, and that composites with such fillers have good application potential.

Optimized metal foam liners with spatially gradient properties for aircraft engine noise reduction

Recent studies conducted by NASA have identified over the rotor liners as one of the most promising avenues for aircraft noise reduction. However, conventional noise absorption technologies cannot withstand the harsh pressure and temperature conditions near the engine core. While open celled metal foams are an alternative material choice, their open porous structure results in comparatively lower absorption characteristics. In this talk, we summarize the results from our recent efforts on improving the acoustical properties of metal foams for aircraft noise reduction applications. We show that compressing the foams substantially improves their absorption coefficient because of the reduction in the effective pore size. Unfortunately, this improvement comes with an undesirable weight penalty. To overcome this, we propose an optimized layered configuration to create a step-wise relative density gradient that provides comparable absorption characteristics while being over 20% lighter than the benchmark compressed foam. Our results show that metal foam liners with spatially gradient property configurations can provide broadband engine noise reduction while minimizing the resulting weight penalty.

Surface-active extracts from plants rich in saponins – effect on lipid mono- and bilayers

The aqueous extracts of the seeds of oat (Avena sativa L.), horse chestnut (Aesculus hippocastanum L.), soybean (Glycine max L.), cowherb (Vaccaria hispanica [P. Mill.] Rauschert) and quinoa (Chenopodium quinoa Willd.), and the roots of soapwort (Saponaria officinalis L.) without any preservatives were characterized in terms of their surface tension, surface compression (dilational) rheology, foamability and foam stability. The saponin content in the extracts was determined using UPLC-MS and their interaction with model lipid monolayers consisting of dipalmitoylphosphatidylcholine (DPPC)/cholesterol and Ceramide AP/stearic acid/cholesterol were analyzed by surface pressure relaxation, surface compression elasticity and neutron reflectometry (NR). The lipid composition was chosen to mimic the cell membrane of keratinocytes – major constituents of the human deeper skin layers, and the intercellular lipids (“mortar”) in the “bricks and mortar” model of the outermost layer of the epidermis (stratum corneum). Bilayers of DPPC/cholesterol were additionally characterized using dynamic light scattering (DLS) and NR. The oat and soybean extracts were shown to be much less abundant in saponins as compared to cowherb, horse chestnut, soapwort or quinoa, and showed limited foaming abilities. They did not affect significantly the model lipid mono- and bilayers mimicking the skin outer layers, either. The horse chestnut extract affected both model membranes to the highest extent, yet without solubilizing the lipids.

Splitting and curling collapse of metal foam core square sandwich metal tubes: Experimental and theoretical investigations

Axial splitting and curling collapse of square sandwich metal tubes with metal foam core is investigated analytically and experimentally. The square sandwich metal tube split axially and curl outward along prefabricated cracks. Axial compressive tests of square sandwich metal tubes with prefabricated cracks are conducted and deformation modes are observed. An analytical model for axial splitting and curling behavior of square sandwich metal tube considering plastic bending, crack tearing, curling, foam compression, friction is proposed. It is demonstrated the analytical predictions are in good agreement with experimental results. Influences of foam thickness, tube thickness, die angle, prefabricated crack length, and foam strength are of vital importance to axial splitting and curling of square sandwich metal tube.

Undrained compressibility characteristics and pore pressure calculation model of foam-conditioned sand

Soil conditioning with foam is widely used to transform natural soil into the desired state suitable for mechanised tunnelling. Since the excavated soil is rapidly discharged out with little water drained during earth pressure balance (EPB) shield tunnelling, it is necessary to investigate the undrained compressibility characteristics of foam-conditioned soil under chamber pressure. In this study, a series of compression tests were carried out in a large-scale, self-designed compression device equipped with pore pressure and lateral earth pressure sensors. The results demonstrated that the foam considerably enhanced the compressibility, pore pressure and lateral pressure of the conditioned sand. The workability of foam-conditioned sand may be well conducted in slump tests under the atmospheric condition, but the compressibility of foam-conditioned probably cannot satisfy its requirement for EPB shield tunnelling due to compression of foam under high chamber pressure. In addition, the total and effective lateral pressure coefficients of the foam-conditioned sand increased and decreased, respectively with increasing foam injection ratio and total vertical pressure. Then, the mechanism of the compressibility of foam-conditioned sand is explained with an existing two-dimensional (2-D) model. Finally, according to Boyle’s law, an analytical model is proposed to predict the pore pressure of the foam-conditioned sand under compression pressure, and a satisfactory agreement between the calculated values and the test results was found.

Wide range continuously tunable and fast thermal switching based on compressible graphene composite foams

Thermal switches have gained intense interest recently for enabling dynamic thermal management of electronic devices and batteries that need to function at dramatically varied ambient or operating conditions. However, current approaches have limitations such as the lack of continuous tunability, low switching ratio, low speed, and not being scalable. Here, a continuously tunable, wide-range, and fast thermal switching approach is proposed and demonstrated using compressible graphene composite foams. Large (~8x) continuous tuning of the thermal resistance is achieved from the uncompressed to the fully compressed state. Environmental chamber experiments show that our variable thermal resistor can precisely stabilize the operating temperature of a heat generating device while the ambient temperature varies continuously by ~10 °C or the heat generation rate varies by a factor of 2.7. This thermal device is promising for dynamic control of operating temperatures in battery thermal management, space conditioning, vehicle thermal comfort, and thermal energy storage.

A computational method to simulate mono- and poly-disperse two-dimensional foams flowing in obstructed channel

A modified phase-field model is presented to numerically study the dynamics of flowing foam in an obstructed channel. The bubbles are described as smooth deformable fields interacting with one another through a repulsive potential. A strength of the model lies in its ability to simulate foams with wide range of gas fraction. The foam motion, composed of about hundred two-dimensional gas elements, was analyzed for gas fractions ranging from 0.4 to 0.99, that is below and beyond the jamming transition. Simulations are preformed near the quasi-static limit, indicating that the bubble rearrangement in the obstructed channel is primarily driven by the soft collisions and not by the hydrodynamics. Foam compression and relaxation upstream and downstream of the obstacle are reproduced and qualitatively match previous experimental and numerical observations. Striking dynamics, such as bubbles being squeezed by their neighbors in negative flow direction, are also revealed at intermediate gas fractions.

Random laser and stimulated Raman scattering in compressible porous polymeric foam

In this work, Random laser (RL) and stimulated Raman scattering (SRS) are investigated using Rhodamine 6G ethanol solution in poly (melamine formaldehyde) foam with micro/nano-sized porous structures. At low dye concentration, the RL containing multiple discrete narrow peaks is observed in both its natural and compressed state of foam. It is found that the cavity length in the compressed state is significantly shorter through the power Fourier transform of the spectra. At high dye concentration, in the natural state of the foam, the coexistence of the RL and SRS is observed, while only the SRS peaks appear in the compressed state. It may provide a novel approach to achieving mode-controllable RL emission.