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In this study, an innovative thermal energy storage design method was developed by adding the combination of metal foam and fin to phase change materials (PCMs). A numerical model was built and verified based on the comparison among the present model prediction, experimental measurements, and numerical results in open literature. To highlight the novel design method, four cases including fin-PCM, foam-PCM, fin-foam-PCM, and PCM unit were compared by means of solidification features. The temperature distribution, solidification front propagation, and buoyancy-induced convection in the liquid PCM were accounted for. Numerical results demonstrated that metal foam outperformed fin regarding the improvement on solidification phase change. The combination of foam and fin achieved the best performance, leading to a 90.5% reduction in complete energy release time in comparison with the PCM unit. The proposed design method provided reference potentials for advancing energy storage engineering. However, buoyancy-induced convection in the liquid PCM before solidification was harmful to the formation of solidification front and its movement. A maximal 11.5% prolonging time for the complete solidification was found.

The performance of photovoltaic (PV) modules worsens due to increasing their operating temperature. In the current study, a passive cooling technique comprising an aluminum metal foam (AMF) with PCM for thermal regulation of a PV system is performed. Outdoors experiments are conducted comprising two modules: PV without any modifications and PV with AMF embedded in PCM denoted as PV/PCM/AMF. The temperature distribution on the surface of the PV panels, PCM temperature, open-circuit voltage, and output power produced were recorded during the winter period. The results revealed that the PV surface temperature of the PV-PCM/AFM system was 4 %, 7.4 %, and 13.2 % lower than that of conventional PV, and the power produced from PV-PCM/AFM system was 1.85 %, 3.38 %, and 4.14 % higher than that of conventional PV in December, January, and February, respectively.

This paper presents the numerical examination of the effect of spatial porosity variation of aluminum metal foams filled in a vertical channel. The physical domain comprises of a vertical channel in which aluminum plate cum heater assembly is placed at the center of the channel. The heat transfer from the aluminum plate is enhanced by using aluminum metal foams of different pore densities of 10, 20, 30, and 45 with varied porosities are considered in the present examination. A conjugate heat transfer analysis is carried out with the help of ANSYS FLUENT for a fluid inlet velocity of 0.1 – 1.5 m/s. The flow-through metal foam porous medium is predicted with the help of Darcy Extended Forchheimer model while heat transfer is predicted using the local thermal non-equilibrium model. The numerical methodology adopted in the current work is validated by comparing the present results with the literature. The hydrodynamic characteristics such as pressure drop and friction factor and thermal characteristics represented by Nusselt number, Colburn j factor, and overall performance factor are discussed in the present numerical investigation. The results of spatially varied porosity of metal foams are compared with uniform porosity metal foam. It is observed from the results that the spatial variation in porosity for the considered metal foam and the considered thickness of the channel does not significantly improve heat transfer but a slight decrease in pressure drop is observed compared to uniform porosity metal foam.

Three passive cooling configurations of a concentrator photovoltaic (CPV) system have been proposed to dissipate the heat via pure phase change material (PCM), Nano-PCM, and metal Foam-PCM as heat absorbers. A computational fluid dynamic model has been developed to compare the cooling capacity, thermal performance, and electrical efficiency of these configurations at three inclination angles. Evaluation of metal Foam-PCM performance, comparison between Foam- and Nano-PCM at different inclination angles, and exploring the effects on the output efficiencies are the most significant innovations of this study, which is not presented extensively before. In this regard, an experimental setup has been provided to validate the numerical simulations. The results revealed that the Foam-PCM sink could accelerate the melting process so that it mitigates the complete melting time and average PV temperature by 13.6% and 10.7%, respectively, at 150° inclination angle compared to the pure PCM. While the Nano-PCM sink does not make significant improvements. The results also indicate that the amount of absorbed heat and produced electricity till the complete melting time in Foam-PCM are increased by 7.5% and 4.8%, respectively. The superiority of the metal Foam-PCM sink could be improved by increasing the mass of metal through reducing the foam porosity.

The PCM composited with metal foam (PCM-porous system) as heat sink to cool photovoltaic (PV) panel is a potential application. However, there has little attention on the differences in cooling effect of PCM-porous systems when PV panels install with different inclination angles. To fill this research gap, the charging processes of PCM-porous systems with different inclined angles (φ = 0°, 30°, 60°, 90°) have been investigated numerically and experimentally in the current work. Meanwhile, the influences of different Rayleigh numbers (Ra = 1.4568 × 106, 1.8210 × 108, 1.1654 × 1010) have been considered. Results show that the inclined angle has little impact on the PCM-porous system with small porosity (e = 85%, 90%), which is much different from the PCM-porous system with larger porosity (e = 95%). In the discussion, an interesting phenomenon has been found that the weak natural convection of liquid PCM in porous media induced by the inclined cavity plays a negative role in melting process, which is obvious in PCM-porous system with small porosity (e = 85%, 90%). But this negative effect is not necessarily a bad thing due to that it can extend the duration time to cool the PV panel. The maximum duration time of PCM-porous system with e = 85% or 90% is 2 times of system with e = 95% (φ≠0°).

In this study, the predicting and avoiding method of core fracture in plastic forming for aluminum foam sandwich panel (AFSP) were investigated. By observing the macroscopic core cracks and microscopic morphology of the fracture surfaces, the core fracture occurred in plastic forming of AFSP can be confirmed as ductile fracture. Five ductile fracture criteria were introduced for predicting the fracture initiation and detailed simulations on plastic forming of AFSP were performed with a mesoscopic 3D Voronoi AFSP model; besides, multi-point forming experiments of cylindrical, spherical, and saddle-shaped AFSPs were carried out. Normalized value I distributions on the cores using different fracture criteria and core cracks found experimentally indicate that Ko fracture criterion is the most suitable to predict the core cracking during curved AFSPs forming. Moreover, on the basis of the core value I distributions obtained using Ko criterion and the experimental panels in the case of different forming step numbers and core relative densities, it is found that the risk of core fracture can be reduced by adopting multi-step forming and increasing the core relative density.

Critical size of droplet on metal fiber is an important parameter during the dehumidifying process, as it determines the drainage performance of metal foam heat exchangers. In the present study, the droplet shedding characteristics on metal fibers with various fiber diameters, surface wettability and inclined angles were investigated experimentally. The results show that, the critical size of droplet on metal fibers is increased by 69%-213% as the receding contact angle reduces from 132.8° to 17.2°, and it is increased by 93%-292% as the fiber diameter increases from 0.3 mm to 2.0 mm. As the inclined angle of metal fiber increases from 0° to 90°, the critical droplet size is decreased by 78%-86%. Based on the equilibrium of gravity and capillary force, a predictive correlation for the critical droplet size on metal fibers with different wettability and inclined angles was developed, and it agrees with 90% of the experimental data within a deviation of ±15%.

The magnetron sputtering has been used to prepare metal foam wicks for heat pipes by coating the surface of copper foam with zinc oxide (ZnO) nanoparticles. The main properties, including microscop...

In the framework of third-order shear deformation shell theory, this research explores stability behavior of metal foam double-curvature shells under transverse mechanical loading. It is also assumed that the metal foam shell has been reinforced with eccentrical stiffeners. Metal foam has been considered identical to porous materials having uniform or non-uniform pores. The double-curvature foam shell has been exposed to out-of-plane pressure load which leads to post-buckling stability in nonlinear regimes. Employing an analytical procedure and taking into consideration Airy stress function, the established governing equations have been solved to determine the stability load of stiffened double-curvature metal foam shells. Curvature radius, stiffeners, pore volume and shell geometry are shown to have remarkable influences on stability curves.

This work analyzes the free vibration of a spinning functionally graded graphene platelet-reinforced metal foam (FG-GPLRMF) beam. The differential transformation method is extended to analyze flap-wise bending vibration and chordwise bending vibration with Coriolis force effect for the first time. The beam is modeled using the Euler–Bernoulli beam theory. The Halpin–Tsai micromechanics model is utilized to predict effective material properties. Various types of graphene platelet (GPL) and porosity distributions are considered. The governing equations and corresponding boundary conditions of the FG-GPLRMF beam are obtained via Hamilton’s principle. Results show that the vibration characteristics of the FG-GPLRMF beam are affected by the GPL geometry size, types of porosity, and GPL distributions. Among different types of porosity, the Porosity-A causes the highest fundamental natural frequency, while the Porosity-B corresponds to the lowest one of the spinning FG-GPLRMF beam in most cases. Moreover, the GPL pattern and porosity distribution have a coupled effect on the bending vibration of the spinning FG-GPLRMF beam.

This study conducted a simulation and an experimental study on a channel that was partly filled with open-cell metal foam block. Different blockage ratios have been considered, where the foam height could occupy more than half of the channel size. The aim is to investigate the flow behaviours across the complicated structure of the porous medium. Results show that the use of Ergun and Forchheimer models showed a similar stagnant region and recirculation zone in the partially filled channel, which agreed with the experimental results. However, the deviation in pressure drop performance at a high blockage ratio is noticeable.

Poor thermal conductivity of phase change materials (PCMs) is the principal barrier to their widespread application. As such, numerous single or hybrid techniques have been proposed to lower the thermal resistance of PCMs. In the present paper, a hybrid approach, including the dispersing of nano-sized particles and embedding in a porous medium, was employed to augment the rate of heat transfer and melting process of the resulting nano-enhanced PCM (NePCM). Aluminum foam was used as the solid matrix, and phase-change heat transfer of a NePCM comprising n-octadecane as the phase change substance and nano-sized particles of mesoporous silica (MPSiO2) was studied. Previous experimental studies have shown that, although n-octadecane behaves as a Newtonian fluid, the mentioned NePCM behavior deviates from that of Newtonian fluids. Hence, the thermal and hydrodynamic behaviors of the non-Newtonian suspension of the NePCM in porous media were investigated numerically. Governing equations, including mass and momentum conservation for the liquid NePCM and energy equations for both solid and liquid phases, were solved using the Galerkin finite element method. The deformed mesh technique was employed to address the movement of the melting front. The finite element code was validated against several experimental and numerical works and was sufficiently accurate. Results showed that owing to the alteration of the rheological and thermophysical characteristics of the NePCM, increasing concentration of nanoparticles reduced the average Nusselt number and the normalized melt volume fraction (NMVF). It was also found that porosity played an important role in the phase-change rate. Although the steady-state condition was achieved faster in the case of lowest porosity, the maximum NMVF was achieved in the case of the highest porosity after Fourier number = 0.02.

The latent heat thermal energy storage unit (LHTESU) strengthened by metal foam can effectively store solar energy and realize the sustainable utilization of solar energy. In this paper, the metal foam with a two-dimensional (radial and circumferential direction) porosity gradient is proposed for the problem of slow melting rate and non-uniform melting in the horizontal shell-and-tube LHTESU. The non-uniform index and thermal energy storage rate are introduced to evaluate different metal foam structures. Under the same amount of metal foam, the influence of one-dimensional and two-dimensional graded structures is numerically studied. The results show that circumferential graded structure can alleviate the non-uniform melting problem. Compared with the uniform structure, the non-uniformity index decreases by 36.63% and the thermal energy storage rate is increased by 38.60%. In addition, the optimum circumferential porosity gradient also increases with the increase of Ra*. The strengthening effect of the circumferential and radial graded structures is also compared. It can be found that with the increase of porosity gradient, the strengthening effect of the circumferential graded structure increases gradually and that of radial graded structure first increases and then decreases. When the circumferential graded structure is combined with the radial graded structure, the two-dimensional porosity gradient structure can further improve the thermal performance of LHTESU. Compared with the uniform structure, the thermal energy storage rate can be increased by 47.40%.

Closed-cell porous aluminum is expected to be a prominent material in near future because of its light weight, high specific modulus of elasticity, high energy absorption efficiency and high sound-insulating capacity in the automotive and aerospace industries. Recently, a new method of foaming has been developed in which a precursor is formed using friction stir processing. In the friction stir processing route, a precursor is fabricated by embedding a mixture of blowing agent powder and stabilization agent powder into aluminum alloy plates by the significant stirring action of friction stir processing. By applying the friction stir processing route precursor method, the cost-effective Al-foam formation along with high productivity can be accomplished. In this study, titanium hydride powder has been used as the blowing agent as it is reported to be most compatible with aluminum matrix. The effect of percentage of stabilization agent, i.e. alumina powder on porosity of aluminum foams formed using friction stir processing route is analyzed. The porous aluminum formed with three different percentages of alumina is observed and their porosity is calculated. Also, the compressive performance of the obtained samples is observed in order to examine the alumina powder addition on mechanical properties of the obtained metal foam. This study aims at analyzing the significance of addition of the alumina into the blowing agent while developing the metal foam through friction stir processing route.

Large open-cell copper (Cu) foam plates were fabricated using the sintering and dissolution process with NaCl spacers. A rotating tungsten carbide (WC) tool with a flat shoulder was used to generate the temperature and pressure needed for sintering. Sintering was done on a friction stir welding machine. Tool path and die design control the sintered part shape and size. The process allows for fabrication of large three-dimensional metal foam parts on conventional milling and friction stir welding machines. NaCl volume fraction in metal powder-NaCl filler mixture was kept at 80%. Copper foam obtained in this manner had uniform porosity. Tool traverse speed affected sintering time and temperature and influenced the mechanical properties and microstructure of sintered parts. The microstructure of copper foam was studied using a scanning electron microscope. Compression tests were used to study its mechanical properties. Macro-pores were seen to have NaCl particle morphology. Foam mechanical properties were seen to be on par with that reported in literature. The sintering and dissolution process presented in this work results in open-cell foams with large surface areas. It is an attractive alternative for the fabrication of three-dimensional porous sintered parts.

The model equation method (MEM) is a new method to measure the porosity of porous materials. This paper demonstrates the application value of the MEM in the preparation of titanium foams from an experimental point of view. The results showed that the porosities calculated by the MEM were in the range of 0.533–0.701 with the spacer contents between 0.55 and -0.75. The measured values were highly consistent with those of the mass volume method, which indicates that the MEM was feasible to measure porosity. The correlation equation between porosity and spacer content has a very high prediction accuracy by a linear fitting. The elastic modulus and yield strength of titanium foams were 4.8–29 GPa and 10.2–101.1 MPa, respectively. The relative elastic modulus and relative yield strength were directly proportional to the n-th power of relative density through a nonlinear fitting. The mathematical correlations between relative mechanical properties and spacer content were established. This study not only proves that the new method of porosity measurement has an important application value, but also realizes the source control of mechanical properties of titanium foams.

The thermal performance of the latent heat thermal energy storage unit (LHTESU) can be effectively promoted by metal foam. In the present work, a new structure of metal foam with a two-dimensional porosity gradient (MFTDPG) is proposed to further accelerate the melting process inside the rectangular cavity. The MFTDPG is obtained by placing the metal foam with small porosity near the left wall and the bottom wall. With consideration of natural convection, the melting behavior under different parameters is numerically analyzed, including the direction of the porosity gradient, the temperature of the left wall, and the aspect ratio of the rectangular cavity. The results show that the structure of metal foam with vertical porosity gradient (MFVPG) and horizontal porosity gradient (MFHPG) can reduce the total melting time by 7.65% and 3.37% respectively. The MFTDPG can shorten the total melting time by 12.07% compared with the structure with uniform porosity. Furthermore, the MFTDPG can achieve the shortest melting time and the maximum thermal energy storage rate (TESR) with different wall temperatures and aspect ratios. For example, when the aspect ratio is 2.5, the total melting time of MFTDPG is reduced by 24.35%, and TESR is increased by 25.88%.

Thermal energy storage (TES) has been playing a crucial role in addressing the issue of solving the intermittent and random problems in solar energy utilization. The objective of this study is to squarely address and clarify the contribution of metal fin and foam to enhancing the phase change heat transfer by experiments. A novel hybrid fin-foam tube is proposed and its thermal performance is evaluated by experimentally comparing with other three competing structures including bare, fin, and metal foam tubes. A well-designed test rig is built and the energy storage features for the designed four TES tubes are analyzed by the complete melting time, melting front evolution, temperature variation and uniformity, and the temperature response rate. Results show that the fin-foam hybrid structure outperforms the other competing ones, demonstrating a reduction of 83.35% in complete melting time (compared with the bare tube). The transient temperature response is maximized by 529.1%. As for the single structure, both fins and metal foam can improve conductivity of phase change materials. The metal foam does a good favor to improve the uniformity of the temperature field inside the TES tube, but the fins weakened the uniformity. If the design target is temperature uniformity, adding metal foams other than fins can fulfil the task.

The space holder process (SHP) is a useful and common technique to obtain metal foams. However, an important question remains unsolved: Would the quality of the salt affect the properties of the aluminum foam obtained? In this paper, removable preforms of two types of salt (refined and unrefined) were infiltrated with A356 aluminum alloy to obtain metal foams with different pore sizes. The interaction preform-metal was studied from analyzing the morphological structure of the foams, the metal microstructure, and the corrosion resistance of the Al356 alloy. It was observed that, although the two types of salt exhibited some differences, they did not show variations in relation to the porous structure and metal microstructure in the aluminum foams obtained. Additionally, the electrochemical analyses did not show significant effects on the corrosion behavior of aluminum foams caused by the interaction with the salt preforms.

In this study, the consequence of cell-size, cell-wall-thickness and cell circularity together on the compressive performance of closed-cell aluminum foam was analyzed experimentally and with FEM simultaneously. The closed-cell metal foams (CAFs) with varying cell sizes of 55% porosity were synthesized through stir casting technique. The granular metallic calcium is used as a stabilizing/thickening agent, and TiH2 powder used as a foaming agent. The uniaxial compression tests were performed to investigate the compressive deformation behavior of CAFs. The simulation studies were carried out by taking the assumption similar to experimental constraints. The circular-shaped cells were created in FE half symmetrical model of varying cell sizes (in 2-Dimensional). The cell sizes used in FE models are 1.5 mm, 2.5 mm, 2.8 mm and of 3.5 mm. While in experimental samples, different cell sizes obtained are 1.65 mm, 2.47 mm, 2.88 mm and 3.59 mm. In both of the investigations, it is observed that the energy absorption capacity and plateau strength decrease with an increase in cell sizes or vice versa. A similar effect was also observed with an increase in cell wall thickness. The obtained FE results are acceptable and comparable with the experimental for each cell size model. The deformation mechanism was analyzed using deformed sample images, which were captured during the deformation as well as during the different stages in the FEA models.

In the last decades, Aluminum foam has attracted many researchers and manufacturers due to its unique properties which find a lot of applications, especially in a lightweight structure. The current work aims to study the effect of adding calcined alumina to the melting aluminum on the final mechanical and microstructure of produced aluminum foam. Calcium carbonate was used as a foaming agent. The study reveals that calcination times/temperature have a significant effect on the final foam porosity. with increasing calcination time from 30 min to 90 min the foam density improved from 2.27 to 1.27 g/cm3, which consequently result in increase of samples porosity from 15.9 to 52.7%. also, the results from the compression test show that the variation of calcination time can be used to alter the energy absorption capacity of samples. Tested samples achieved the highest energy absorption of 128 MPa at a calcination time of 90 min. Also, the study reveals that calcination temperature has a significant effect on the final foam porosity. with increasing calcination temperature from 400 to 800°C, the foam density improved from 2.18 to 1.09 g/cm3, which consequently result in increase of samples porosity from 18.94 to 52.79%. Tested samples achieved the highest energy absorption of 325 MPa at a calcination temperature of 800°C. The increase in porosity is measured by ImageJ software, and the energy absorption test was carried out by a quasi-static compression test. These improvements produced material can be used in applications needs high energy absorption like automotive industry.

Open-cell aluminum foams with spherical cells have great potential application due to their reliable structural and functional performance. However, a problem of poor cell connectivity always arises during fabrication. Three precursor designs were explored to optimize the cell structure. The results showed that the lack of the treatment of the space holders caused poor cell connectivity and a lower porosity, which could be resolved by introducing alcohol as a binder or hot-pressing space holders in precursor designs. Nevertheless, a poor fluid of the granules in the former had a negative effect on porosity improvement, whereas the latter created a precursor with strong bonding between the granules with good flow characteristics and led to a significant improvement in cell connectivity and porosity. This work could provide an approach to designing precursor structures in order to tailor the structure of the final open-cell aluminum foam.

The closed-cell aluminum alloy foams were fabricated by the molten body transitional foaming process. In this research, the closed-cell aluminum foams were successfully fabricated with different zinc contents (4, 8, and 12wt%) using the melt-foaming method and blowing agents. Calcium was used to increase the melt viscosity and CaCO3 was used as a foaming agent. Uniaxial compressions tests were performed on the foams to investigate the effects of zinc addition on the mechanical behavior of fabricated Al–Zn foams. The effects of zinc additions on the foam properties such as density, porosity, pore diameter, yield strength, plateau stress, and energy absorption were investigated. According to the X-ray analysis results, the reaction between Al–Ca–Zn leads to the formation of oxide phases in the melt and increases the melt viscosity and also the cell wall thickness. Foam with 4wt% Zn has a good yield strength and longer plateau region than pure aluminum foam due to the uniform cell structure. The foam density and the absorbed energy per unit volume of Al–Zn foams increase with increasing zinc content to foams.

In this study, the vibration and flutter characteristics of the graphene platelets reinforced functionally graded porous cylindrical panels subjected to the supersonic flow are investigated for the first time. The considered panels are constructed of the nanocomposites that made of matrix of open-cell metal foams with graded pore distributions and are reinforced uniformly by the graphene platelets. The typical mechanical properties of porous matrix are determined using open-cell metal foam model, which provides a typical mechanical feature to determine the relationship between coefficients of density and porosity. The effective elasticity modulus of the nanocomposite is determined based on a modified Halpin-Tsai micromechanics model, and the rule of mixture is used to calculate the Poisson's ratio and mass density. A high order shear deformable computational framework is developed with inclusion of the trapezoidal shape factor to eliminate the errors introduced by the curvature of the panels. The standard Lagrange processing in conjunction with the Navier-solution technique, with the help of the first-order piston theory, is applied to derive the equations of motion related to the vibration and flutter characteristics of the cylindrical panel with simple-supported boundary condition. Comparisons of the natural frequencies with the previous works are performed to validate the proposed model. Parameter studies are carried out, and the results in the form of graphs or tables reveal the effects of pore, graphene platelets on the supersonic flutter characteristics of the nanocomposite cylindrical panels subjected to the aerodynamic flow.

In this paper, the Taguchi optimization methodology was utilized for optimizing the production parameters of aluminum foam sandwich panels (AFSP) with different skin layers under low-velocity impact loading. The core material of AFSP was A356 aluminum foam reinforced with SiC particles produced by the CaCO3 foaming agent with 20, 30, and 40 mm thicknesses. The skin layers of plates were made of glass/epoxy with the quasi-isotropic and cross-ply layout as well as the pure aluminum layer. The drop weight impact device was used for the impact test. Three types of impactors (spherical, parabolic, and cone) were used. The evaluated impact parameters are the skin layer layout, impactor shape and core thickness of AFSP. Also, the measured response factors were the specific absorbed energy (SAE), maximum displacement (MD), and maximum impact force (MIF). The Taguchi method was used to check the effect of the production parameters on the response factors by creating the orthogonal array (OA). The results indicated that the best combination of production parameters can be determined by the application of the Taguchi method. These results can provide the optimal impact responses (the largest SAE, the smallest MD, and the smallest value of MIF). For the best SAE and MIF, A1–B1–C1 (pure aluminum/conical/20 mm core) was also investigated. Meanwhile, the optimized combination of levels for all the three production factors was examined to provide the lowest MD (A3–B2–C1, cross-ply/parabolic/20 mm core).

Metal foams are typically subjected to quasi-static or dynamic shear-compression combined loading in applications such as energy absorbers and structure protectors. The yield behavior of a metal foam under dynamic and quasi-static shear-compression combined loadings is investigated in this study. First, quasi-static and dynamic compression-shear combined tests at different loading angles are conducted using a universal testing machine and a rotatable Hopkinson bar system, respectively. Shear deformation reduces the plateau stress as the loading angle increases. Subsequently, the yield modes of the metal foam under combined loadings are investigated. Only one yield band occurs under a combined loading with large loading angles (mode I), whereas several yield bands occur under a combined loading with small loading angles (mode II). Finally, the yield surface plot of metal foam indicates significant enhancement in terms of normal stress and shear stress under dynamic loading. Quasi-static and dynamic phenomenological yield criteria for a shear-normal stress space are established to provide a brief and precise prediction of the behavior of metal foam under quasi-static and dynamic combined loadings.

The outstanding mechanical properties and lightness of aluminum foam make it attractive as buffering and energy absorption material for spacecraft landing in deep space exploration. In this paper, cell-based model of open-cell aluminum foam has been established by Voronoi tessellation method. Through quantitative comparisons of energy absorption performance between different simulation models, it can be found that the improvement of base material properties can lead to significant enhancement of energy absorption ability, and there is an approximate linear relationship between relative density and relative energy absorption at low speeds. Characteristic deformation mode has been discussed under different compression speeds. The isotropic buffering characteristic of aluminum foam materials has been verified by the simulation of a footpad filled with aluminum foam impacting on a sloping ground.

PurposeThe purpose of this paper is to provide a summarization and review of the present author's main investigations on failure modes of reticular metal foams under different loadings in engineering applications.Design/methodology/approachWith the octahedral structure model proposed by the present authors themselves, the fundamentally mechanical relations have been systematically studied for reticular metal foams with open cells in their previous works. On this basis, such model theory is continually used to investigate the failure mode of this kind of porous materials under compression, bending, torsion and shearing, which are common loading forms in engineering applications.FindingsThe pore-strut of metal foams under different compressive loadings will fail in the tensile breaking mode when it is brittle. While it is ductile, it will tend to the shearing failure mode when the shearing strength is half or nearly half of the tensile strength for the corresponding dense material and to the tensile breaking mode when the shearing strength is higher than half of the tensile strength to a certain value. The failure modes of such porous materials under bending, torsional and shearing loads are also similarly related to their material species.Originality/valueThis paper presents a distinctive method to conveniently analyze and estimate the failure mode of metal foams under different loadings in engineering applications.

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The present numerical investigation examines the performance improvement of thermoelectric generators (TEGs) by using phase change materials (PCM) and porous medium. Due to the high latent heat of PCMs, both sides of the TEG were filled with paraffin RT35 (on the cold-side) and paraffin RT69 (on the hot-side). The PCM in the cold-side of the TEG was used as a heat-sink whereas the PCM in hot-side of the TEG was used to reduce the output voltage fluctuations. Since the system was periodically subjected to heat flux from an external heat source, the paraffin in the hot-side of the TEG was also used to generate a continuous thermal heat when the heat source was cut-off. To increase the thermal conductivity of the phase change material, this investigation studied the effect of using the copper porous medium with different porosities (0.80, 0.90, and 0.95) and three different pores per inches (PPI) as 10, 20, and 40. The results show that the use of porous on the cold-side of the TEG produces more electrical energy and output voltage compared to (i) having porous medium on the hot-side and (ii) using PCM without porous medium on both sides of the thermoelectric generator. Furthermore, the results indicated that the TEG performance enhanced by increasing PPI and reducing porosity. As a result, by increasing the PPI from 10 to 40 (at 0.80 porosity) and by reducing porosity from 0.95 to 0.80 (at PPI 20), the electricity generated increases by 13.57 and 5.36%, respectively.

In the present study, we analyze the nonlinear forced vibration of thin-walled metal foam cylindrical shells reinforced with functionally graded graphene platelets. Attention is focused on the 1:1:1:2 internal resonances, which is detected to exist in this novel nanocomposite structure. Three kinds of porosity distribution and different kinds of graphene platelet distribution are considered. The equations of motion and the compatibility equation are deduced according to the Donnell’s nonlinear shell theory. The stress function is introduced, and then, the four-degree-of-freedom nonlinear ordinary differential equations (ODEs) are obtained via the Galerkin method. The numerical analysis of nonlinear forced vibration responses is presented by using the pseudo-arclength continuation technique. The present results are validated by comparison with those in existing literature for special cases. Results demonstrate that the amplitude–frequency relations of the system are very complex due to the 1:1:1:2 internal resonances. Porosity distribution and graphene platelet (GPL) distribution influence obviously the nonlinear behavior of the shells. We also found that the inclusion of graphene platelets in the shells weakens the nonlinear coupling effect. Moreover, the effects of the porosity coefficient and GPL weight fraction on the nonlinear dynamical response are strongly related to the porosity distribution as well as graphene platelet distribution.

Purpose This study aims to generate different three-dimensional (3D) foam models using computer tomography (CT) scan and solid continuum techniques. The generated foam models were used to study deformation mechanism and the elastic-plastic behaviour with the existing experimental foam behaviour. Design/methodology/approach CT scan model was generated by combing 2D images of foam in MIMICS software. Afterwards, it was imported in ABAQUS/CAE software. However, solid continuum model was generated in ABAQUS/CAE software by using crushable foam properties. Then, the generated foam models were sets boundary conditions for a compression test. Findings CT scans capture the actual morphology of foam sample which may directly an image based finite element foam model. The sectional views of both the models were used to observe deformation mechanism on compression. The real compressive behaviour of foam was visualised in CT-Scan foam model. It was observed that CT-scan model was the more accurate modelling method than crushable foam model. Originality/value The internal structure of foam is very complex and difficult to analyse. Therefore, CT-scanning may be the accurate method for capturing the macro-level detailing of foam structure. A CT-scan foam model can be used for multiple times for mechanical analysis using a simulation software, which may reduce the manufacturing and the experimental cost and time.

The purpose of present investigation is to study propagation of flexural wave in porous metal foam beams resting on Winkler–Pasternak foundation based upon refined higher-order shear deformable bea...

Future electronic packaging technology requires semiconductor chips having a larger size and higher power for advanced applications, e.g., new energy conversion systems, electric vehicles, and data center servers, yet traditional thermal interface materials (TIMs) with a high thermal conductivity are generally stiff materials with weak joints, which cause the accumulated thermal stress to concentrate at the chip corners, leading to cracking and popcorn problems. To address such a critical challenge, herein for the first time we report a low-cost and high-performance porous copper (Cu)-indium (In) laminar structure as TIM, which can provide a superior thermal conductivity (50 W m-1 K-1) comparable to indium, yet the Young's modulus (1.0 GPa) is an order of magnitude lower than indium, which is a state-of-the-art value. Additionally, the In-based intermetallic compound (IMC) joints enable more robust mechanical interconnection above the melting point of pure indium, providing better high-temperature performance. The discontinuous IMCs spread the global interfacial thermal stress into numerous isolated local areas, ensuring a reliable joint to resist thermal-mechanical fatigue. In the silicon-TIM-copper package testing vehicles with a large die size (1 × 1 square inch), this structure shows excellent thermal management ability and superior reliability, compared with classical indium and classic commercial silver pastes.

Metal foam material, which serves as an alternative replacement of the conventional flow distributor of proton exchange membrane (PEM) fuel cell, has been attracting much attention over last few decades. In this work, three-dimensional modeling work for PEM fuel cell containing metal foam as cathode flow distributor has been carried out. The fuel cell performance and operating characteristics of metal foam flow field and conventional parallel flow channel have been compared and discussed. The cell performance has been reasonably validated based on the corresponding experimental tests conducted in this study. The superior performance of PEM fuel cell with metal foam as cathode flow field benefits a lot from the uniform gas flow. The porous metal foam material provides more pathways for the water delivery at the interface of metal foam flow field and gas diffusion layer (GDL), accelerating water removal capability of cathode. Because of the significant oxygen transfer loss in diffusion limited parallel channel, the operation of PEM fuel cell with parallel channel is found to be more sensitive to cathode humidification and oxygen supply at inlet. Due to the more uniform and effective electron transport though the porous electrode, it is possible to use thinner GDL in metal foam PEM fuel cell. It is expected that this study could give a good baseline of operating behavior of PEM fuel cell with metal foam flow distributor.

The present article experimentally explored heat transfer through a horizontal metal foam tube with a constant wall heat flux during the subcooled flow boiling of water, Al2O3/H2O, and CuO/H2O nanofluids. To investigate the effect of using metallic foam on the subcooled flow boiling heat transfer, the results have been compared with a simple tube. Besides, The impacts of significant parameters, including subcooled inlet temperature (25–60 °C), mass flux (150–310 kg m−2 s−1), wall heat flux (100–230 kW m−2), particle type (CuO and Al2O3), and nanofluids concentration (0.5% wt., 1% wt.) were investigated on the transfer of boiling heat while measuring pressure loss and rate of heat transfer. The results show that the use of metal foam increases the heat transfer rate by 3.5–5.8 times compared to the simple tube. Comparing the subcooled flow boiling heat transfer of water and nanofluids in both metal foam and simple tubes, it was found that water has superiority over the nanofluids. Besides, the value of the thermal performance index defined as a ratio of the heat transfer enhancement to the pressure loss degradation is more than one for water and the nanofluids.

Porous materials can be used for accidental explosion prevention and suppression in process industries. In this study, an experimental study was conducted to study the effect of an aluminum foam pl...

This research proposes an innovative configuration for modifying the thermal management system of the photovoltaic (PV) panel, integrated with a phase-change material (PCM) with an attached exterior metal-foam layer to the rear part of the PCM container. The configuration enables faster heat dissipation from the system leading to longer thermal-management duration for the PV panel during the energy storage (PCM charging) mode. Also, it supports faster energy recovery (PCM discharging) rate by decreasing the amount of heat trapped in the melted part of the PCM during the solidification mode. The effects of the foam-layer inclusion, PCM thickness, and PV tilt angle are numerically simulated and revealed. A mathematical model that accounts for natural convection effects of the melted PCM and non-Darcy effects of the metal foam, is formulated and validated via previous experiments. The results show that inclusion of an exterior foam layer could increase the PCM melting time, and the corresponding PV thermal-management duration, by up to 32% and 55% respectively, depending on the PCM thickness and PV tilt angle. The results also show that reducing the tilt angle from 90° to 30° increases the melting time by about 18%. Thus, a superior PCM-based thermal management is achieved. Moreover, utilizing PCM of thickness in the range of 20–30 mm lengthens the melting time by up to 54%, enhancing the potential for improved thermal management of PV panels.

A new method for the manufacturing of pre-determined open porosity Al foams is presented in this work. Starting from a 3D foam model designed with CAD and printed with fused deposition modeling (FDM), a porous structure of poly lactic acid (PLA) has been replicated. The choice of this material has been driven by the properties in terms of recyclability and low cost. The truncated octahedron for the porosity shape has been selected due to benefit and properties ascribable to its morphology. After creating the 3D PLA model, it has been filled with liquid plaster. After its solidification, PLA is removed in oven at 600 °C so that a negative-shaped plaster mold is obtained. Successively liquid Al at 750 °C is poured in the mold inside the oven. After Al solidification, plaster can be easily removed in ultrasonic bath thus obtaining Al foam with the same morphology of the starting PLA model. This process shows great flexibility allowing to manufacture different kind of elementary cell types. Tailoring of the selected properties of the manufactured foams, e.g. the morphology, the density or the surface/volume ratio may be obtained. With this technique many other metals and alloys can be manufactured too. The potential of this production technique can be successfully employed in many application fields of metal foam. Light-weight 3D lattice structures are widely employed for multifunctional applications such as loading bearing, negative and zero thermal-expansion structures, vibration attenuation, impact and blast proof structures.

Metal foam with excellent ductility was added into nano-Ag sintered joint to obtain the composite sintered joint with a sandwich structure of sintered Ag/metal foam/sintered Ag. The microstructure, shear behavior and fracture morphology of the composite sintered joint were investigated in this study. Experimental results indicate that the addition of ductile metal foam enhances the plasticity of composite sintered joint. As the number of pores of Cu foam increased from 110 to 500 per inch, the shear strength increased from 8.28 to 11.26 MPa. The composite sintered joint with 110ppi (pores per inch) Ni foam showed a higher shear strength than the other composite sintered joints did because of the higher Young’s modules and shear modules of Ni foam. In the Ni foam@nano-Ag composite sintered joint, cracks appeared at the interface between the metal foam and the nano-Ag sintered structure because of the mismatch of coefficient of thermal expansion (CTE). Compared with the Ni foam, the addition of Cu foam effectively depressed the generation of cracks at the interface between the metal foam and the nano-Ag sintered structure.

In this study, a nonlinear three-dimensional hydrocode numerical simulation was carried out using AUTODYN-3D to investigate the effect of blasting of a high explosive material (TNT) against several configurations of the composite structure. Several numerical models were carried out to study the effect of varying the thickness of the walls and the effect of adding an air layer or aluminum foam layer inside two layers of concrete in mitigating the effect of blast waves on the structure walls. The results showed that increasing the thickness of walls has a good effect on mitigating the effect of blast waves. When a layer of air was added, the effect of blast waves was exaggerated, while when a layer of aluminum foam was added the blast wave effects were mitigated with a reasonable percentage.

It is well-known that flow field design is of primary importance to optimization of proton exchange membrane (PEM) fuel cell. Traditional channel-rib flow fields, e.g. parallel or serpentine channels, always lead to non-uniform distributions of reactant gas, liquid, current density and so on between the channel and rib regions. Metal foam materials with high porosity (>90%) have been proposed as alternative flow fields for PEM fuel cells. In this study, influences of metal foam flow field on the transport phenomena coupled with the electrochemical reactions in PEM fuel cell are investigated using a three-dimensional (3D) multi-phase non-isothermal model. Specifically, the full morphology of metal foam flow field is taken into account in the 3D simulation after validated against experimental permeability data. The full morphology inclusion enables capture of the detailed gas flow from the flow field into the gas diffusion layer (GDL) and the current collection at the metal foam/GDL interface. In addition, compared with the conventional channel-rib flow fields, the metal foam design greatly increases fuel cell performance in the high current density regime. In addition, the oxygen and current density distributions in PEM fuel cell with the metal foam flow field are more uniform than those in the conventional one. Though the current collection area at the GDL surface is much smaller in the metal foam flow field, the relevant Ohmic loss won't increase significantly due to the improved physical contact by the fine pore structure of metal foam over the GDL.

Some important properties of the metal foams that make them attractive materials for various purposes are their excellent stiffness to weight ratio (light-weight structure), ability to take up strain by crushing at controlled pressure (energy and impact absorption), order of magnitude higher damping capacity as compared to the solids (mechanical damping), higher natural flexural vibration frequencies (vibration control), reasonable sound absorbing capacity accompanied by durability and fire resistance (acoustic absorption), and, high area of contact accompanied by high thermal conductivity (heat exchanger). Often foam is joined or connected to cover sheets of the same metal and the whole part together is called a foam sandwich. Among all the metal foams aluminium metal foam has found the widest and diverse application. This article covers important recent literature on laser processing viz. laser forming, laser welding, laser cutting and laser additive manufacturing of metal foams. Prior to this, a link is established between foam/foam sandwich and laser processing techniques stating the limitations of other relatively more conventional processing techniques. Future research direction regarding different laser processing techniques using metal foams has also been outlined.

The deformation behavior and crashworthiness of functionally-graded foam-filled tubes (FGFTs) under drop-weight impact loading were investigated. Closed cell aluminum, A356 alloy and zinc foams fabricated by the liquid state processing were used as axial grading fillers for the manufacture of single-layer and multilayer structures with different configurations. The results indicate that the deformation of multilayer foam filled tubes initiates from the low-strength components, and then propagates in the high-strength components through the gradual increment of stress. The use of more A356 alloy and aluminum foam layers provides greater specific energy absorption (SEA) for the graded structures, whereas the high-strength zinc foam has no positive effect on the crash performance. The progressive collapse of graded structures consisting of the aluminum and A356 alloy foams occurs in a symmetric mode under quasi-static and drop-weight impact conditions. However, the zinc foam causes a combination of symmetric and extension modes as well as greater localized deformation under dynamic loading and greater local rupture in quasi-static loading condition. The Al−A356 foam-filled tubes with a combination of the highest SEA (10 J/g) and the lowest initial peak stress (σmax of 10.2 MPa) are considered as the best lightweight crashworthy structures.

The purpose of innovative engineering inventions in our modern world is not necessarily to solve a new problem, but to implement and optimize an existing solution in a more energy-efficient and cost-effective manner. This can be achieved by increasing the load-bearing capacity or reducing the weight. Using these two methods simultaneously we can produce so-called syntactic metal foams. The mechanical properties of syntactic foams are highly dependent on the filler materials’ volume. Therefore, in the course of our research, we produce gradient syntactic metal foams (GSMFs) with gradient filler volume within one metal foam. Mechanical analysis as compressive tests and microstructural analysis were performed to determine the properties of the differently filled syntactic metal foams.

In the present work, the effect of low-speed impact on the static residual strength of aluminum foam sandwiches having GFRP skins has been evaluated. Two different configurations have been considered, which differs both for thickness and layup used for the manufacturing of GFRP skins. The detection and the quantification of the damage induced by impact have exploited the potentiality of pulsed thermography and phased array ultrasonic techniques, which gives the possibility to provide synergistic and complementary information. Mechanical strength has been evaluated through three-point bending tests carried out on undamaged and damaged specimens. Static tests allowed also evaluating the failure mode of panels and the changes induced by the presence of a low-speed impact zone.