Aluminum Matrix Syntactic Foams Research Articles

Tribological Properties of Aluminium Matrix Syntactic Foams Manufactured with Aluminium Smelter Waste

Aluminium smelter waste (ASW) is a big contributor to landfills, and its recycling has been of great interest. This study investigates the tribological properties of aluminium matrix syntactic foams manufactured using an Al 6082 alloy and ASW. Ball-on-disc tests were conducted under both dry and lubricated conditions. Under dry sliding conditions, the coefficient of friction (COF) had an initial sharp increase, followed by a gradual decrease and finally a steady state as the sliding distance increased. The wear surfaces showed the presence of adhesive, abrasive and oxidative wear, with some presence of delamination. Syntactic foams containing small ASW particles led to a decrease in surface roughness, decrease in the average COF and decrease in specific wear. Heating large ASW particles before manufacturing the syntactic foams enhanced overall wear properties because the particles are hardened due to a compositional change. The T6 treatment of the syntactic foams enhanced the wear properties due to the hardening of the Al matrix. The average COF of the ASW syntactic foams was higher than that of the E-sphere syntactic foam, which was predominantly abrasive wear. The specific wear of the ASW syntactic foams can be higher or lower than the E-sphere syntactic foam, depending on the ASW particle size. Under lubricated sliding test conditions, the wear was reduced significantly, and the type changed from predominantly adhesive to predominantly abrasive. The porous ASW particles acted as lubricant reservoirs and provided a constant supply of lubricant, further improving the lubrication effect.

Experimental and numerical analysis of the compression behavior of aluminum syntactic foams reinforced with alumina hollow particles

In this study, analytical, numerical, and experimental methods are used to investigate the compressive behavior of alumina hollow particles reinforced aluminum matrix syntactic foams (AMSF). The representative volume element (RVE) models are generated for different volume fractions to analyze the elastic and elastio-plastic behavior of AMSFs using the FE solver ABAQUS. The geometric feature of the hollow particles is selected close to the actual physical dimensions. The effective elastic properties are estimated using linear homogenization models. For example, the elastic properties predicted using the Mori-Tanaka model are close to the FE-based RVE model data. Later, the macroscopic response (stress-strain data) is determined using the volume-averaging method proposed in the literature. The stress-strain response of the FE model with a 30% volume fraction has shown close agreement with the experimental data. Further, a parametric study is conducted for different particle wall thicknesses. These FE models have great potential in studying the ceramic hollow particles reinforced metal matrix syntactic foams and developing new porous composites under compression loading using RVE-based models.

Dynamic Mechanical Properties of Ceramic Hollow Sphere-Reinforced Aluminum Matrix Syntactic Foams

Dynamic Mechanical Properties of Ceramic Hollow Sphere-Reinforced Aluminum Matrix Syntactic Foams

Dynamic response and residual compressive characteristics of syntactic foams at high and low temperatures

The dynamic response at low and high temperatures and compression after impact of aluminum matrix syntactic foams were studied. There were many cracks in syntactic foams after dynamic compression. The failure behaviors of compression after impact were almost identical to those of quasi-static compression in the late plateau stage and densification stage. The dynamic compressive properties of syntactic foams are greatly affected by the hollow sphere size at low strain rate, but this phenomenon is not remarkable at medium and high strain rates. The compressive strength and plateau stress are insensitive to the strain rate, but the energy absorption increases when increasing the strain rate. The dynamic compressive properties of syntactic foams have low-temperature strengthening and high-temperature softening effects, but the latter no longer changes above 100 ℃. The residual energy absorption is high, which indicates syntactic foams have potential as energy absorbing materials after dynamic damage.

Boosting energy absorption performance of aluminum matrix syntactic foam with carbon coated glass cenospheres

In this study, glass cenospheres are coated with resorcinol/formaldehyde resin in an alkaline solution, and the polymer layer is subsequently transformed into carbon shell by pyrolysis. Because carbon is a strong and light-weight material, the resulting aluminum matrix syntactic foam reinforced with carbon coated glass cenospheres shows low density of 1.35 g cm−3, and high energy absorption capacity of 80.3 MJ m−3. The excellent energy absorption properties are ascribed to the conformal carbon shell that can disperse stress, leading to high compressive strength of the foam. The improved wettability of filler surfaces by liquid metals during pressure infiltration casting is verified using both optical and electron microscopy. In addition, XRD results suggest that no obvious interfacial reactions happen during the preparation of foam.

Effect of particle size and distribution of hollow spheres on the compressive behavior of aluminum matrix syntactic foams

Effect of particle size and distribution of hollow spheres on the compressive behavior of aluminum matrix syntactic foams

A novel approach for in-situ producing Al2O3/aluminum matrix syntactic foam with high specific strength

Low-density foams with high strength are eagerly desired to use as energy absorption and shock isolation systems during transportation. In this work, an Al2O3/aluminum matrix syntactic foam with a density of 1.41 g/cm3 and a compressive strength of 238 MPa was prepared by a novel approach, which specific strength outperforms the most advanced aluminum matrix syntactic foams as reported in the literature. Especially, the hollow Al2O3 spheres were produced by an in-situ reaction of the hollow glass beads in this foam. Moreover, an electric current was first utilized in this new approach, which proved to have a crucial effect on the in-situ reaction, making the hollow glass beads rapidly and completely transform into Al2O3 spheres to improve interface conditions. The approach is believed to provide a favorable strategy to design different metal matrix syntactic foams with improved performance.

Preparation and characterization of light weight aluminum matrix syntactic foams with high energy absorbing capacity

Aluminum matrix syntactic foams (AMSFs) with low density are widely utilized in the field of impact resistance owing to their high energy absorbing properties. In present study, to further lower the density and improve the energy absorption of AMSFs, a low-temperature micro-pressure infiltration was utilized to avoid destroying the hollow structure and a bi-continuous structure was designed to increase the energy absorbing interface and improve the deformation behavior. Results show that the hollow sphere content was up to 65% and a breakage rate was below 4% in the composites. Meanwhile, the composites displayed a rather low density of 1.23–1.41 g cm−3, a high compressive strength of 83.96–243.31 MPa, and an excellent energy absorbing capacity of 38.07–99.51 MJ m−3 under quasi-static loading, which outperforms the most advanced AMSFs as reported in the literatures. With the increase of strain rate, the composites showed higher plateau stress and energy absorbing capacity under dynamic loading. The energy was absorbed by shear deformation of cenospheres and interfacial tearing between cenospheres and aluminum matrix. A unique “fracture ring” was observed in bi-continuous structure preventing crack growth.

Quasi-static compressive response and energy absorption properties of aluminum matrix syntactic foams: Room temperature and elevated temperature conditions

Aluminum matrix syntactic foams(AMSF) are lightweight composite foams with functional and structural properties such as low relative density and high energy absorbing nature. These qualities made AMSFs a practical alternative to conventional materials desirable for automotive, aerospace and shipbuilding industries as energy absorbers. Many studies have reported the mechanical aspects of these materials. However, a detailed analysis of energy-absorbing behavior on aluminum matrix syntactic foams is sparse. This work produces alumina-reinforced aluminum syntactic foams using the powder metallurgy route. A systematic study on quasi-static room temperature (RT) and elevated temperature (ET) is conducted to understand the effect of the volume fraction and size of the particle individually. The compressive stress-strain response shows volume fraction and temperature dependency for different particle size ranges. The maximum densification strain (RT-58% and ET- 55%) and energy absorption efficiency (RT- 70.61% and ET-75.77%) of samples tested in quasi-static- RT and ETs are observed, respectively. Despite large deformation, no sudden drop in stress-strain response and macroscopic stability were observed in the samples.

Preparation and quasi-static compression properties of hybrid aluminum matrix syntactic foam reinforced with glass cenospheres and silicon carbide nanowires

Conventional hybrid aluminum matrix syntactic foam with various hollow fillers shows low density and high densification strain. However, its peak stress can hardly be increased, resulting in a limited improvement in the energy absorption capacity. Although composites can be reinforced by adding ceramic nanoparticles, it is difficult to achieve dispersion of both hollow and dense fillers in the metal matrix due to their distinct density difference. In this study, we use silicon carbide nanowires reinforced aluminum swarf as the source of ceramic fillers, and prepare hybrid aluminum syntactic foam reinforced by both glass cenospheres and silicon carbide nanowires. The resulting syntactic foam shows low density of 1.3 g cm −3 , high peak stress of 128.6 MPa, and high energy absorption capacity of 60.70 MJ m −3 . Moreover, we demonstrate a novel way to recycle silicon carbide reinforced aluminum composites for reprocessing. • HASF reinforced with a hollow and a dense nanowire filler. • Glass cenospheres and SiCnw forming high dispersion of microscale domains in HASF. • Reprocessing both metal matrix and SiCnw fillers at the same time. • HASF showing strength of 128.6 MPa and energy absorption capacity of 60.70 MJ m −3 .

Enhanced energy absorption and microstructural studies on hollow glass microsphere filled closed cell aluminum matrix syntactic foam

The research on lightweight materials for advanced engineering applications attracted the development of metal matrix syntactic foams. The automobile sector has started using Al-based alloys in structural components such as crash-box, underride-guard, fenders, dampers, A, B, and C Pillars. The present study explores the energy absorption behavior; microstructural characterization such as SEM, EDS, and XRD analysis of hollow glass microsphere (HGM) filled aluminum matrix syntactic foam. A380 aluminum alloy reinforced with different volume fractions 10%, 20%, 30%, and 35% of hollow glass microspheres were used in the fabrication of syntactic foam using the stir casting technique. The quasi-static compression test conducted, evaluated the plateau strength, which improved from 284.14 to 341.69 MPa, and energy absorption capacity was observed in the range 139.25–187.92 MJ/m3. The plateau strength and energy absorption capacity were improved by 16.82% and 25.89% for the 35 vol.% HGM sample as compared with 10 vol.% HGM filled aluminum matrix syntactic foam. The addition of a calcium thickening agent in the casting process improved the bonding between aluminum and HGM particle and also the homogeneous distribution of HGM. The XRD analysis revealed the chemical reaction that occurred between aluminum and SiO2 that produced the AlSiO2 and Al2SiO5 interfacial compounds. This reaction tends to collapse the HGM cell wall and fills it with matrix material.

Dynamic response of aluminium matrix syntactic foams subjected to high strain-rate loadings

This paper presents experimental work to characterise the dynamic behaviour of aluminium matrix syntactic foams subjected to compression, Split Hopkinson Pressure Bar and terminal ballistic impact tests as well as blast loading. Numerical models have also been developed to simulate the dynamic response of the composite foams. The effect of strain-rate on their compressive crush behaviour has been investigated, given that the rate-dependent characteristics of these materials are required for designing dynamically loaded structures. Characterisation of the behaviour of the foam under high strain-rate loadings and the identification of the underlying failure mechanisms were also undertaken to evaluate their effective mechanical performance. The results show that the aluminium syntactic foam is sensitive to strain-rate in terms of initial stiffness, peak stress and plateau stress and show a pronounced high-rate dependence at a strain rate above 1000 s-1. The concrete damage plasticity model with rate-dependent features were used to simulate the dynamic behaviour of the foams, with the failure modes being captured. The model was verified and validated against the experimental results, and predictions were made for the normal and oblique ballistic impact response. Overall, the level of agreement between the numerical simulations and the experimental results is encouraging.

Enhanced Electromagnetic Interference Shielding Effectiveness of an Eco-Friendly Cenosphere-Filled Aluminum Matrix Syntactic Foam

Enhanced Electromagnetic Interference Shielding Effectiveness of an Eco-Friendly Cenosphere-Filled Aluminum Matrix Syntactic Foam

Production of syntactic metal foams reinforced in the matrix material

Metal foams are cellular materials where the matrix material is metallic, and gaseous cells are present in this enclosing material. Due to these cells, metal foams are low-density materials and have good energy-absorbing properties to their structure. Reinforcing materials can highly increase the load capacity of the structure. Our goal is to produce a low-cost, reinforced syntactic metal foam with an easy production process. The mechanical properties of A356 (AlSi7Mg) aluminium matrix syntactic foams are investigated, produced with lightweight expanded clay aggregate particles (LECAPs) as filler material and reinforced with aluminum-oxide (Al2O3) with a diameter of 1 mm and 0.5 mm, and silicon carbide (SiC) with a diameter of 0.4 mm in the matrix. 20 wt.% of the reinforcement was used in each case. The foams were produced by low-pressure infiltration, and the specimens, which were cut by conventional machining methods, were subjected to heat treatment. The grain structures of the materials were studied via optical microscopy, their mechanical properties were tested with compression tests. Results show that the production is successful, and reinforcement can be achieved with these materials.

Influences of reinforcement size and artificial aging on the compression features of hybrid ceramic filled aluminum syntactic foams

Over the past years, the number of scientific efforts on aluminum matrix syntactic foams (AMSFs) has increased in a noteworthy manner, and different investigation teams have tried to figure out the physical, microstructural, and mechanical properties of AMSFs. In this paper, different from the previous valuable efforts, an industrial-focused cold chamber die casting machine was utilized during the fabrication instead of commonly used lab-scale techniques. Also, the effects of the reinforcement diameter on the compressive features were analyzed for pumice and expanded glass-added hybrid AMSFs. To ascertain the mechanical properties, quasi-static compression tests were conducted and stress–strain curves were obtained. During the compression tests, the deformation styles of the hybrid foams were followed to comprehend their damage mechanisms. Moreover, half of the samples were subjected to artificial aging treatment and the results were checked up with as-cast samples. According to experimental outcomes, it was obvious that the artificial aging treatment caused superior mechanical properties and triggered brittle-style deformation.

Interface characterization and mechanical property of an aluminum matrix syntactic foam with multi-shelled hollow sphere structure

The novel aluminum matrix (Al-matrix) syntactic foam with multi-shelled hollow sphere structure (HSS) was fabricated by introducing double-layered 316L-Al2O3 metal-ceramic hollow spheres (M-C HSs) through powder metallurgy method. Microstructure characterization and mechanical properties of multi-shelled HSS have been investigated by XRD, SEM, TEM/EDS and nanoindentation. Quasi-static compressive tests of Al matrix, Al-matrix syntactic foams with Al2O3 HS and M-C HS have been performed. Compressive strength (σ0.2), plateau stress (σp), plateau end strain (εpe), and energy absorption (W50) were used to analyze the effect of multi-shelled HSS in the syntactic foam. The results showed that in multiple interfaces formed in the syntactic foam, main elements diffusion was found in interface between Al2O3 and 316L shells. While, the intermetallic shell formed in interface between 316L shell and Al matrix was composed of Fe4Al13 substrate, and precipitations of Cr phases and Mo-rich phases. Therefore, a “ceramic-metal-intermetallic” multi-shelled HSS was formed in syntactic foam with M-C HS. Compressive strength of the syntactic foam was increased by 8.04% compared with that of syntactic foam with Al2O3 HS, which led to high energy absorption (W50 = 93.28 MJ/m3). Deformation mechanism of multi-shelled HSS has been discussed in this work.

Production and Functional Properties of Graded Al-Based Syntactic Metal Foams

As cellular materials are gaining more ground in the automotive, airplane, and railway industries, the demand for functionally graded metal foams has appeared. In the case of syntactic metal foams, by changing the distribution of the filler material, the properties of the foams can be precisely adjusted according to the desired area of application. Several kinds of graded aluminum matrix syntactic foams (GMSFs) were fabricated with lightweight expanded clay aggregate particles and ceramic hollow spheres as filler materials. Their mechanical properties were observed by modal analysis and compression tests, supplemented with an accurate density determination by computer tomography measurements. The compressive properties were set up on a large scale by adjusting the density by adding specific amounts of Al particles to the filler. Based on the modal analysis results, simple averaging the density of GMSFs produces an inaccurate result in mode shapes and material parameters, so the varying density distributions should be taken into account. By simply varying the distribution of the filler material, we can modify the effective material properties of metal foams to better fit industrial requirements.

Effect of single and hybrid hollow sphere reinforcement on the deformation mechanism of aluminum matrix syntactic foam at a low strain rate

The combination of soft matrix alloys and brittle spheres has gained unceasing demand due to its structural strength and tailored properties to meet industrial and commercial needs. Single sphere aluminum matrix syntactic foams (AMSFs) show poor ductility and fracture strength at high volume fractions of reinforcement. In the present investigation, three different volume fractions of the single sphere (alumina hollow spheres and cenospheres), syntactic foams (SF) and hybrid SF were prepared using a powder metallurgy route with a maximum reinforcement fraction of 30%. The lowest density of 2.17 g cm -3 was produced with no chemical reaction observed between matrix and reinforcement. The quasi-static compression studies have shown a significant effect of particle size and volume fraction with respective mechanical properties (peak stress = 601 MPa (Sample #1), 610 MPa (Sample #4) and 525 MPa (Sample #10)). The densification strain, energy absorption, energy absorption efficiency (EAE) and ideal EAE have been predicated for all the samples. The macroscopic deformation of SFs is in good agreement with stress-strain data. The results show that the slope of the plateau region follows a negative linear trend against the strain hardening exponent.

Preparation and Quasi-Static Compression Properties of Hybrid Aluminum Matrix Syntactic Foam Reinforced with Glass Cenospheres and Silicon Carbide Nanowires

Preparation and Quasi-Static Compression Properties of Hybrid Aluminum Matrix Syntactic Foam Reinforced with Glass Cenospheres and Silicon Carbide Nanowires

Quasi-State Compressive Properties of Functionally Graded Aluminum Matrix Syntactic Foams

The uniform aluminum matrix syntactic foams (SFs) were prepared by the stir casting method, with alumina hollow spheres (2-3 mm and 3-4 mm) and expanded glass (2-3 mm) as reinforcements, and ZL111 aluminum alloy as matrix. The functionally graded aluminum matrix syntactic foams (FG-SFs) were obtained by superimposing two uniform aluminum matrix syntactic foams. Quasi-static compression tests were performed. The plateau stress of FG-SFs containing only hollow spheres decreased slightly with increasing volume fraction of SF containing 3-4 mm hollow spheres. The FG-SFs containing 2-3 mm hollow spheres and 2-3 mm expanded glass showed the highest plateau stress. The energy absorption behavior of all samples fluctuated in a small range. The initial position of shear band depended on the volume fraction of uniform aluminum matrix syntactic foams, reinforcement type and size. The cracks always appeared first in the uniform aluminum matrix syntactic foams containing expanded glass.