Strength Of Foams Research Articles

Friction Welding of Polycarbonate Plate and Aluminum Foam Fabricated by Precursor Foaming Process

Aluminum foam is expected to be one of the candidates for lightweight materials for structural components as it is lightweight and has excellent shock absorption and sound absorption properties. However, aluminum foam has low tensile and flexural strength due to its thin cell walls. Therefore, aluminum foam is used by combining with dense materials. In particular, with the recent trend toward multi-materials, research on the combination with lightweight resins is expected. In this study, we attempted to join aluminum foam fabricated by the precursor method to a thermoplastic resin polycarbonate (PCTA) plate by friction welding. It was found that the aluminum foam and PCTA plate can be joined in about 1 min by friction welding, by rotating the aluminum foam at 2000 rpm and pressing 1 mm into the PCTA plate. In addition, in the friction welding of aluminum foam and PCTA plate, it was found that the pores of the aluminum foam were maintained without being collapsed. The anchoring effect is presumably caused by the penetration of PCTA softened by the frictional heat generated by the friction welding into the pores. Furthermore, tensile tests of the joined samples showed that fracture occurred either at the joining interface or at the base material of the aluminum foam, and that the joining strength was equivalent to the tensile strength of the aluminum foam itself.

Influence of Melt Infiltration Parameters on Structural and Mechanical Properties of Al-4.3wt.%Cu-EP Syntactic Foam

The present research concerns fabrication of Al-4.3wt.%Cu metal syntactic foams using expanded perlite particles (EPPs). A gas pressure infiltration technique was employed to fabricate the aluminium syntactic foams under different infiltration temperatures and pressures. Ambient air pressure and 750 °C were identified as the favoured processing conditions for full infiltration of the melt. The average density and EP volume percentage of the fabricated foams were measured to be about 1.55 g/cm3 and 50.3%, respectively. Melt infiltration is believed to be mainly controlled by the breakage of the aluminium oxide layer on the melt surface and melt viscosity. Preferential infiltration of the melt between the mould wall and the EP particles bed complemented by radial melt infiltration toward the centre of the samples was identified. The effects of EP particles on growth of the nucleated primary α-aluminium phase were discussed. XRD and EDS analyses suggested some chemical reactions at the interface of EPPs with the molten aluminium. T6 heat treatment in the ambient atmosphere improved the average compressive tensile strength, plateau stress, and absorption capacity of the syntactic foams by more than 100%. Uniform deformation and similar densification strains (about 40%) of the as-fabricated and heat-treated syntactic foams during the compression test suggested uniform distribution of EP particles and metallic struts in the aluminium alloy matrix.

Fabrication and characterization of glassy carbon foams with controllable porosity and high compressive strength

Glassy carbon (GC) foams for a long time have two mainly problems. First, GC foams cannot withstand heavy load application due to its relatively low strength. Second, the matrix is easy to crack during pyrolysis precursor process, leading to a long carbonization time. In this study, high-strength GC foams were fabricated by sacrificial templates method using SiO2 powder and phenolic resin as raw materials. SiO2 powder is uniformly dispersed into phenolic resin, and the interface of SiO2/phenolic resin provides fast diffusing channels for the pyrolysis gases, that reduce the risk of cracks formed in GC matrix during fast carbonization. The compressive strength of as-prepared GC foams with density ranging of 0.324–0.781 g/cm3 is 21.6–106.4 MPa. The stretch-dominated mechanical response of the porous structure accounts for the high strength of the prepared GC foams.

Analytical and Numerical Investigations of Circular Metal Foam Sandwich Tube Under Free Inversion

Abstract The foam sandwich tube contains inner and outer tubes and filling foam. The foam sandwich tube is widely used in engineering, due to its lightweight, high specific strength, energy absorption, and other excellent characteristics. In this paper, the free inversion of the circular metal foam sandwich tube (CMFST) under axial loading is studied analytically and numerically. The plastic deformation occurs in the CMFST, and its main deformation modes include circumferential expansion, radial bending of the CMFST, and compression of the metal sandwich foam. An analytical model for the free inversion of the CMFST under axial loading is established, considering metal tube expansion, the radial bending of metal circular tube wall, and metal foam compression. The commercial abaqus software is adopted to numerically study the free inversion behavior of the CMFST. The analytical predictions agree well with the numerical ones. It is shown that the specific energy absorption (SEA) of the CMFST under free inversion is significantly better than the empty tube. When the non-dimensional foam strength is 0.05, the SEA of the CMFST under free inversion is 107.68% higher than the empty tube. Thus, the metal foam sandwich tube under free inversion is an excellent energy-absorbing device.

Dynamic response of foam-filled X-type sandwich beam under low-velocity impact

The dynamic response of a fully clamped foam-filled X-type sandwich beam under low-velocity impact is studied analytically and numerically. The analytical model is developed for the dynamic response of the sandwich beam with foam-filled X-type core under low-velocity impact based on the yield criterion. The numerical calculations are carried out, and analytical results are in good agreement with numerical ones. The effects of face-sheet thickness, X-type folding plate thickness and foam strength on the impact resistance of the foam-filled X-type sandwich beam are discussed. It is shown that face-sheet thickness, X-type folding plate thickness, and foam strength have noticeable effects on the low-velocity impact response of the foam-filled X-type sandwich beam. The present analytical model can be used to predict the low-velocity impact of the foam-filled X-type sandwich beam.

Nanoparticles Surface Energy Effect on Mechanical Properties and Microscopic Deformation of 3D Heterogeneous Nanostructures

Nanoparticle-contained graphene foam material has attracted many practical applications in recent years, which require an in-depth comprehension of the basic mechanics of these heterogenous materials. In this paper, the effect of nanoparticles surface energy on the mechanical properties of nanoparticle-filled graphene foam under uniaxial tension and compression is systematically studied by the coarse-grained molecular dynamics simulation method. The mechanical strength of these nanoparticle-filled graphene foam is directly influenced by tuning the nanoparticles surface energy. The varying peeling-off behaviors of graphene sheets influenced by the surface energy of nanoparticles are observed. The stress distribution under uniaxial compression and tension at different nanoparticles surface energy is also studied. The mechanical behavior of nanoparticle-filled graphene foam is directly dependent on nanoparticles surface energy. The results should be helpful not only to understand the micro mechanism of such nanomaterials, but also to the design of advanced composites and devices based on porous materials mixed with particles.

A comparative study on dynamic compression response of multi-cell thin-walled structures with filling foams and connecting ribs

In order to comparatively study effect of foam filling and connecting ribs on dynamic response of multi-cell thin-walled structure (MTS), high velocity (30–70 m/s) mass block impact tests were performed on empty MTS, polyurethane foam (PUR) filled MTS (FMTS) and 2nd order MTS (MTS-2nd) with connecting ribs between sub-cells. The dynamic enhancement mechanism of energy absorption of three kinds of thin-walled structures was discussed based on experimental and numerical results. The results indicate that the dynamic enhancement coefficient (DEC) of the mean crushing force (MCF) is 1.07–1.23 and 1.08–1.33 for empty MTS and FMTS, respectively. The dynamic enhancement of total energy absorption (EA) is 11.4–26.32% for MTS, 13.83–32.52% for FMTS and 4.3–9.68% for MTS-2nd, compared to the quasi-static compression. The multi-cellularization tends to degenerate the crushing force sensitivity of MTS to the loading rate, while the foam filling increases the sensitivity. The inertia effect is the main reason for the dynamic enhancement of crushing force of thin-walled structures. The coupling effect of FMTS is related to the dimensions of sub-cells, the impact velocity and the foam strength. The folding pattern and deformation stability of MTS can be improved by filling foams and increasing impact velocity. The multi-cellularization by using connecting ribs is still the most effective method to improve the specific energy absorption of thin-walled structures, although it causes a size effect and reduces the robustness of deformation modes.

Carbon composite foams from the wasted banana leaf for EMI shielding and thermal insulation

Low-density fire-resistant materials with high EMI shielding effectiveness and low thermal conductivity are extremely important in aerospace and defence applications. Utilization of agricultural residues for achieving this reduces CO2 emission as well as produces wealth for the farmers. Herein, a fibre extracted from the wasted matured banana leaf by a simple chopping and grinding using a mixture-grinder is used for the preparation of carbon composite foams. The banana leaf fibres dispersed in sucrose solution are consolidated by filter-pressing followed by freeze drying to produce banana leaf fibre-sucrose composites. The carbon produced from sucrose during carbonization binds the carbonized banana leaf fibre to produce the carbon composite foams. The XRD pattern and Raman analysis indicated the turbostratic nature of the carbon, and XPS analysis shows the presence of oxygen-containing functional groups. The textural property measurement and TEM analysis indicated the presence of micro and meso pores in the carbon composite foams. The foam density (0.14–0.28 g cm−3), compressive strength (0.14–0.88 MPa), electrical conductivity (3.7–8.7 S m−1), and thermal conductivity (0.095–0.144 W m-1 K−1) of the carbon composite foams increases with an increase in sucrose solution concentration (300–700 g L−1). The carbon composite foams exhibit a reflection-dominated EMI shielding with high total shielding effectiveness in the range of 48.3–77.5 dB. The multiple internal reflections within a range of macropores available in the carbon composite foams, leading to enhanced absorption, are responsible for the excellent EMI shielding characteristics.

The ambient and elevated temperature performance of hemp fibre reinforced alkali-activated cement foam: Effects of fibre dosage and alkali treatment

Hemp fibre is gaining attention as a sustainable alternative to synthetic fibres in cementitious composites. This study investigates the effects of dosage and alkali treatment of hemp fibre (HF) on the strength, shrinkage, and fire resistance of alkali-activated cement foam (AACF). Raw untreated and NaOH-treated HFs were added at 0.3%, 0.7%, and 1% of the volume of precursor slurry. The findings reveal that alkali-treated HF increases the compressive strength, which increased with dosage up to 0.7% and then dropped slightly at 1%. Whereas raw HF lowered compressive strength except for 0.7%. Flexural strength was enhanced by both treated and untreated fibre, which increased with the dosage up to 0.7% and then dropped slightly at 1%. The flexural strength enhancement (up to 260%) was higher than compressive strength (up to 54%) at all dosages. Moreover, alkali-treated HF exhibited higher strength compared to raw HF (54% vs 32% under compression and 260% vs 220% under flexure). Residual compressive strength after exposure was measured as an indicator of fire resistance. It followed a similar variation with fibre dosage to their ambient compressive strength when exposed to 100°C and 200°C, where the optimum dosage of 0.7% had up to 65% higher strength for treated fibre and 16% higher strength for raw fibre. However, HF did not improve the residual strength for higher temperatures (400°C and 800°C). In contrast, they caused a higher proportion of strength loss by up to 83–91% of the original strength compared to 67–84% in the control.

Axial Crushing Behaviors of Metal Density Gradient Foam-Filled Square Taper Tubes: Analytical Model and Numerical Calculation

Abstract Metal tube is a traditional energy-absorbing structure, and metal foam is a lightweight material with advantages, i.e., high energy absorption and high specific strength. The foam-filled square tube can improve crashworthiness and has better energy absorption, which is higher than the sum of the energy absorption of the tube and foam. Axial crushing behaviors of metal density gradient foam (DGF) filled square taper tubes are studied analytically and numerically in this paper. An analytical model is presented to study the crushing behavior of DGF-filled square taper metal tube under axial loading, in which the interaction between square taper tube and DGF is considered. The numerical calculation is conducted, and the deformation mode is obtained. The analytical predictions are well consistent with the experimental and numerical results. The influences of taper angle, foam strength, maximum relative density, and minimum relative density of gradient foam on the compressive behavior of metal DGF-filled square taper tubes under axial loading are considered. It is demonstrated that when the taper angle is less than 85 deg, the average crushing force increases as the minimum density of the DGF increases. However, when the taper angle is greater than 85 deg, the average crushing force decreases with the increase of the minimum density of the gradient. This proposed analytical model can effectively predict the axial crushing behaviors of metal DGF-filled square taper tubes.

Effects of wood fiber loading, silane modification and crosslinking on the thermomechanical properties and thermal conductivity of EPDM biocomposite foams

Ethylene propylene diene monomer (EPDM) rubber based bio-composites filled with silane-modified wood fiber (SiWF) were foamed by using chemical foaming method. The SiWF and the incorporation of dicumyl peroxide (DCP) generated crosslinking in the developed EPDM bio-composite foams, which showed much lower water absorption and improved thermomechanical properties. With SiWF and in situ cross-linking, the tensile strength and modulus of EPDM bio-composite foams exhibited up to 90% and 600% enhancement compared to the unfilled foam, respectively. The compressive strength and modulus individually showed up to 170% and 600% increase. The developed bio-composite foams also displayed lower apparent thermal conductivity than the unfilled EPDM foam over the heating temperature range, showing possible applications as insulation materials.

A high-entropy alloy syntactic foam with exceptional cryogenic and dynamic properties

Metal foams are in great demand in extreme service environments with cryogenic temperatures and high strain rates due to their unique properties. However, the reduced ductility and impact toughness under such conditions limit their applications. In this work, we tested the quasi-static and dynamic compression properties of CoCrFeMnNi high entropy alloy syntactic foam at liquid nitrogen temperature (−196 °C). We found that it exhibits ultra-high strengths and energy absorption capacity, especially a superior resistance to embrittlement at cryogenic temperature. Microstructural characterizations reveal that the foam matrix has a high twinning activity and shear localization propensity in cryogenic environments. Dense deformation twins and multiple shear bands intersected, forming a weave-like microstructure that can disperse the deformation and benefits energy absorption. Deformation twins can also strengthen the matrix and delay the crack nucleation and growth. While under dynamic loading, an FCC to HCP phase transformation was activated, forming a nano-laminated dual-phase (NLDP) FCC/HCP structure in the matrix, leading to further strengthening and toughening. Deformation twinning and HCP phase transformation act as additional plastic deformation mechanisms along with stacking faults and shear bands to offset the shortcomings caused by limited dislocation movements at low temperatures and high strain rate dynamic loading, enabling the high strength and energy absorption of the syntactic foam.

Salinity resistance of hydrophilic SiO2/SDS dispersions for foam stability and oil flooding effect: experiments and dynamics simulations

The foam performance of hydrophilic nanoparticles SiO2/SDS (Sodium Dodecyl Sulfonate) foam about temperature and salinity had been assessed by experiments. The concentration of Na+, Ca2+, and Mg2+ ions on foaming volume and foam half-life were verified, and the mixing dispersions with Na+, Ca2+, and Mg2+ concentration of 8:1:1 was researched the IFT, elastic modulus and foam strength by FoamScan for plugging ability. The mixing dispersions of no salinity and Na+, Ca2+, and Mg2+ of 8:1:1 were used to verify the salinity effects on foam properties by building hydrophilic SiO2 nanoparticles at the Gas-liquid interface. The flooding ability of two different foam dispersions was compared to enhance oil recovery. The flooding ability of two surfactant dispersions to oil molecules was verified by building the oil flooding models. In conclusion, the best foam performance condition was 30°Cand the sensitivity to hydrophilic SiO2/SDS dispersions could be summed up as: Ca2+> Mg2+ > Na+, hydrophilic SiO2/SDS foam dispersions with Na+, Ca2+, Mg2+ concentration of 8:1:1 had better foam stability and plugging ability at the salinity of 7.5 × 104∼12.5 × 104mg/L. The oil recovery increased from 53.62% to 68.54%, and simulation results showed that the removal of oil molecules was more efficient in mixed dispersions.

Large Deflection of Foam-Filled Triangular Tubes under Transverse Loading.

In this paper, the large deflection of the foam-filled triangular tube (FFTT) is studied analytically and numerically under transverse loading. Considering the strengths of the foam and the tube, the yield criterion of FFTT is established. Based on the yield criterion, a theoretical model for the large deflection of the clamped triangular tube filled with foam under transverse loading is developed. The numerical simulations are carried out using ABAQUS/Standard software, and the analytical results are compared with the numerical ones. The effects of foam strength, thickness of the tube, and the width of the punch on the load-bearing capacity and energy absorption of the clamped FFTT loaded transversally are discussed in detail. It is demonstrated that the load-bearing ability and the energy absorption increase with increasing foam strength, tube thickness, and punch width. The closer the loading position is to the clamped end, the greater the increases in the capacity of load bearing and the energy absorption of the triangular tube filled with foam. The theoretical model can be used to foresee the large deflection of metal FFTT under transverse loading.

A comparative investigation of the effect of gas type on foam strength and flow behavior in tight carbonates

Foam generation technique has been practically applied to overcome gas mobility issue during enhanced oil recovery (EOR) processes. Incorporated with the utilized gas, the capability of foaming agent to generate persistent foam determines the flow performance under reservoir conditions. In this study, we first identified the surfactants with excellent phase behavior and foaming properties and, second, evaluated their bulk foam performance with different gases, including N2, CO2, and hydrocarbon gas (CH4) under high-pressure and high-temperature conditions. In bulk, the foam generated with the high-density gas, i.e., CO2, exhibited the greatest foamability but the lowest foam stability. With amidoamine oxide-based surfactant, CH4-foam was found to be more stable than N2-foam, while the opposite was observed for sulfobetaine-based surfactant. The most effective surfactant was later used to perform flow experiments on two tight carbonate rocks, including Minnesota Norther Cream Buff and Edwards limestone, with permeabilities of ∼0.8 and 16 mD, respectively. The core-flooding experiments showed that the optimum quality of CO2-foam was lower than that of N2- and CH4-foams. For a given flow rate and fixed foam quality, the steady-state strength followed the descending order of CH4-, N2-, and CO2-foam. However, in general, the difference in foam strength between N2- and CH4-foams was insignificant when the total flow rate was varied. We also found that the variation in rock permeability had a greater effect on the strength of the CO2-foam compared to those generated with N2 and CH4. In the presence of oil, the shear-thinning behavior of all foams was found more prominent. The increase in oil saturation had a more adverse effect on the strength of N2- and CH4-foams, particularly in the higher permeability rock. The results indicated that the foam strength, which is key in the effectiveness of foam EOR applications, is greatly influenced by several factors such as gas density, gas solubility in water, the presence of oil, and rock permeability.

Preparation and Characterization of Natural Rubber Foam Filled with Bagasse Fiber

The properties of natural rubber foam filled with bagasse fiber of varying content (0-50 phr) and different blowing agent content (5 and 8 phr) were investigated, with rubber compounds and vulcanized rubber also examined. Rubber compound properties included measurements of scorch time, cure time, minimum torque, maximum torque, density, and percentage of expansion in the mold. When bagasse fiber and blowing agent content increased, the maximum torque value of the compounded rubber increased. For rubber compound with blowing agent loading at 5 phr, cure time increased with an increasing bagasse fiber content of 40-50 phr, while scorch time and density of the rubber compound remained unchanged. The percentage of rubber compound expansion in the mold decreased with increasing bagasse fiber content. The cell size of natural rubber foams was inspected using an optical microscope. Small and homogeneous cell size was found in natural rubber foam with blowing agent content of 8 phr and higher bagasse fiber content. The incorporation of bagasse fiber enhanced the compressive strength of the natural rubber foam. Vulcanized rubber properties such as the modulus at 100% strain, tensile strength, and strain at break were also studied. The modulus increased, whereas stress at break and strain at break decreased with increasing bagasse fiber content. On the other hand, tensile strength and strain at break increased with increasing blowing agent loading.

In Silico Investigation of the Impact of Reaction Kinetics on the Physico-Mechanical Properties of Coconut-Oil-Based Rigid Polyurethane Foam

Conventionally, designing rigid polyurethane foams (RPUFs) with improved physico-mechanical properties from new, bio-based polyols is performed by modifying foam formulations via experimentation. However, experimental endeavors are very resource-dependent, costly, cumbersome, time-intensive, waste-producing, and present higher health risks. In this study, an RPUF formulation utilizing a coconut-oil (CO)-based polyol with improved physico-mechanical properties was approximated through a computational alternative in the lens of the gel time of the RPUF formation. In the RPUF formation of most bio-based polyols, their very fast gel times negatively impact foam robustness. The computational alternative functioned by finding a CO-based RPUF formulation with a gel time in good agreement with a formulation based on commercial petroleum-derived polyol (control). The CO-based RPUF formulation with the best-fit catalyst loading was approximated by simulating temperature profiles using a range of formulations with modified catalyst loadings iteratively. The computational approach in designing RPUF with improved properties was found to effectively negate foam collapse (with a shrinkage decrease of >60%) and enhance foam strength (with a compressive strength increase of >300%). This study presents an economically and environmentally sustainable approach to designing RPUFs by enabling minimized utilization of material sources for experimentation and analysis and minimized dependence on waste-producing methods.

Green Preparation of Lightweight, High-Strength Cellulose-Based Foam and Evaluation of Its Adsorption Properties.

In recent years, the application scope of most cellulose-based foams is limited due to their low adsorbability and poor recyclability. In this study, a green solvent is used to extract and dissolve cellulose, and the structural stability of the solid foam is enhanced by adding a secondary liquid via the capillary foam technology, and the strength of the solid foam is improved. In addition, the effects of the addition of different gelatin concentrations on the micro-morphology, crystal structure, mechanical properties, adsorption, and recyclability of the cellulose-based foam are investigated. The results show that the cellulose-based foam structure becomes compact, the crystallinity is decreased, the disorder is increased, and the mechanical properties are improved, but its circulation capacity is decreased. When the volume fraction of gelatin is 2.4%, the mechanical properties of foam are the best. The stress of the foam is 55.746 kPa at 60% deformation, and the adsorption capacity reaches 57.061 g/g. The results can serve as a reference for the preparation of highly stable cellulose-based solid foams with excellent adsorption properties.

Dynamic response of multilayer sandwich beams with foam-filled trapezoidal corrugated and foam cores under low-velocity impact

The paper focuses on the dynamic response of multilayer sandwich beams with foam-filled trapezoidal corrugated and foam cores under low-velocity impact with heavy-mass using analytical and numerical methods. Based on the yield criterion for the multilayer sandwich structure, the circumscribing and inscribing loci of sandwich structure are obtained. Considering the interaction of bending and stretching, the analytical solution and “bound” solution for the dynamic response of multilayer sandwich beams with foam-filled trapezoidal corrugated and foam cores are developed. The numerical calculations are used to verify the analytical solutions, and all lie within the analytical “bound” predications. Then, the influences of impact position, foam strength and face-sheet thickness on the dynamic response of multilayer sandwich beams are discussed in detail by theoretical model. For a given deflection, the impact force decreases with impact position closer to the midspan, the impact force increases with the increase of foam strength and face-sheet thickness. The present analytical model can effectively predict the dynamic response of fully clamped multilayer sandwich beams with foam-filled trapezoidal corrugated and foam cores under low-velocity impact.

Influence of minerals on the foaming properties of milk

A comprehensive study on the effect of mineral content on milk foaming properties was conducted. Samples with increased mineral concentration were prepared by adding four different types of minerals (KH2PO4, K3Cit, CaCl2 and MgCl2) at three different concentration levels (5, 10 and 20 mM) in both reconstituted skim milk powder and milk protein concentrate. Samples with reduced minerals were prepared by reconstituting milk protein concentrate in modified simulated milk ultrafiltrates. Different mineral types showed different effects on the physicochemical properties of milk samples. The addition of K3Cit increased the viscosity and decreased the surface tension while there were no significant differences between the samples added with KH2PO4, MgCl2, or CaCl2. In terms of foaming properties, the addition of CaCl2 or MgCl2 significantly increased the foam strength and stability while decreasing foamability. In contrast, the addition of K3Cit significantly decreased foam stability and foam strength while increasing foamability. It was also found that reduction in minerals in the range studied did not affect the foaming properties of milk. These results indicate that the effect of minerals on milk foaming properties depends on the type of mineral and the concentration. This provides an insight that while designing dairy-based food products, the mineral content can be manipulated to achieve the desired foaming properties.