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Microstructural observations and compressive property datasets of metal matrix syntactic foam core sandwich composite at quasi-static and high strain rate (HSR) conditions (525–845 s−1) are provided. The data supplied in this article includes sample preparation procedure prior to scanning electron and optical microscopy as well as the micrographs. The data used to construct the stress–strain curves and the derived compressive properties of all specimens in both quasi-static and HSR regions are included. Videos of quasi-static compressive failure and that obtained by a high speed image acquisition system during deformation and failure of HSR specimen are also included.

Abstract Powder metallurgy and rapid microwave (MW) sintering techniques were successfully applied to engineer a hybrid cell structure into magnesium alloy AZ61 syntactic foams. The hybrid cell structure, comprising open- and closed-cells, originated from leached carbamide granules and hollow microspheres of fly ash (HS), respectively. External MW susceptors accelerated the sintering process and greatly mitigated the formation of undesirable interfacial reactions. The cell hybridisation technique facilitated control over the density and strength of the syntactic foams. Accordingly, floatable syntactic foams with a density of about 0.79 g/cm3 and compressive strength of 16 MPa were synthesised without recourse to any surface modification or chemically-induced superhydrophobicity. The processing techniques were capable of mitigating damage to the HS microspheres as confirmed by microstructural examinations. Furthermore, potential applications of the floatable syntactic foam sample, as a microboat and chemical release agent, were demonstrated by using ethanol as a propellant. AZ61 syntactic foams synthesised in this study exhibited low density and adequate strength, suggesting their applicability as alternative materials to polymer composite foams. Graphical abstract Unlabelled Image Highlights • Magnesium alloy AZ61 syntactic foams with hybrid pore structure were fabricated via microwave sintering techniques. • Floatable magnesium alloy AZ61 syntactic foam was realised with a density 0.79 g/cm3 and adequate strength. • The whole process of microwave sintering is within 20 minutes, minimizing the interfacial reactions and energy consumption. • Potential applications as a floatable metallic microboat and chemical release agent were demonstrated. [ABSTRACT FROM AUTHOR]

Abstract In this paper, the effect of arctic conditions on the flexural response of cenosphere/epoxy syntactic foams is investigated. Understanding the behavior of such foams under extreme conditions is critical for exploring their suitability for constructing lightweight platforms used in arctic explorations. Such platforms are exposed to subzero temperatures for extended periods of time potentially degrading their mechanical properties. In the research study presented here, samples of cenosphere/epoxy syntactic foams were conditioned under arctic environment at −60 °C temperature for a period of 57 days. Flexural tests were then conducted at room temperature as well as in-situ −60 °C on the conditioned samples and compared against unconditioned samples. Combinations of surface modification and cenosphere volume fractions were considered. Experimental findings showed that an increase in flexural modulus can be observed at room temperature with increasing cenosphere volume content for both untreated and treated cenosphere reinforced syntactic foams. In contrast, a decrease in flexural strength was observed as compared to neat resin. For the case of arctic exposed samples, an apparent increase in flexural modulus was recorded between 7-15% as compared to room temperature cenospheres/epoxy syntactic foams. In addition, an apparent increase of 3–80% in the flexural strength was observed under arctic environment. The conditioning of cenosphere/epoxy syntactic foams under low temperatures manifested lower strains to failure as compared to neat epoxy and they exhibit quasi-brittle behavior leading to sudden failure in the post peak regime. [ABSTRACT FROM AUTHOR]

Abstract In this study, a novel grid skeleton (i.e., the 3D printed healing-agent based honeycomb structure) was embedded in a syntactic foam matrix to enable the composites to own crack closing and healing capabilities. There is always a trade-off between crack healing efficiency and overall structural properties. The new type grid skeleton was proposed here to make syntactic foam composites owning excellent crack healing ability without sacrificing overall mechanical properties. The volume fraction of glass microballoons within syntactic foam matrix remained constant at 30%. The reinforcing honeycomb cell sizes varied with a ratio from 3.8, to 5.4 and 7.3, which resulted in various physical and mechanical properties, such as different density and compressive strength. The thermal properties of the syntactic foam composites were tested through Differential Scanning Calorimetry (DSC). The interfaces between the syntactic foam matrix and PCL grid skeleton (i.e., printout) was investigated by the Fourier Transform Infrared (FTIR) spectrum. It displayed that the interaction between those phases were completely in a physical manner. Nano-indentation tests were conducted to study the composite component mechanical properties. Three-point bending tests were conducted to initiate structural level cracks to examine the crack healing capability. Healing efficiency was obtained according to the comparison between specific flexural strength before and after the crack healing event. Under free constraint condition, the 3D printed PCL honeycomb reinforced syntactic foam exhibited promising crack healing performance with healing efficiencies above 80%. This study provided an understanding on the interface property and crack healing mechanisms in the 3D printed honeycomb reinforced syntactic foam system. Graphical abstract Image 1 Highlights • A syntactic foam matrix was reinforced by a 3D printed polycaprolactone (PCL) honeycomb as a new type of grid skeleton. • The interfaces between foam matrix and PCL printout was investigated by the FT-IR and nano-indentation. • Compressive behavior of the syntactic foam composites was investigated under in-plane and out-of-plane loading conditions. • Flexural behavior of the syntactic foam composite was investigated under in-plane and out-of-plane loading conditions. • Under free constraint condition, the composites exhibited promising self-healing performance with efficiencies above 80%. [ABSTRACT FROM AUTHOR]

Experimental investigation on deflection behaviour of fly ash cenosphere/epoxy syntactic foam at room temperature and under thermal environment (three different heating conditions) is investigated. Influence of fly ash cenosphere volume fraction and nature of temperature variation on deflection behaviour of syntactic foam beam is discussed elaborately. Results reveal that the syntactic foam beam experience snap-through buckling under thermal environment and is reflected by two bifurcation points in temperature-deflection plot. It is observed that the time duration for which the foam beam stays in the first buckled position increases with increase in cenosphere content. Thermal environment induces compressive stresses in the samples causing such snap-through buckling. However, such phenomenon is not observed when mechanical compressive loads are applied under room temperature conditions. Temperature variation across the beam strongly influences snap-through buckling in syntactic foams in addition to volume fraction of filler content. [ABSTRACT FROM AUTHOR]

Quasi-static compressive behavior of different density glass microballoon (GMB) reinforced high density polyethylene (HDPE) syntactic foams are investigated in the present work. Reducing the weight of thermoplastic components has been always a high priority in transportation, aerospace, consumer products and underwater vehicle structures. Despite continued interest in developing lightweight thermoplastic syntactic foams, they have not been studied extensively for quasi-static response with focus on wall thickness and volume fraction variations. Compression molded GMB/HDPE sheets are subjected to 0.001, 0.01 and 0.1 s −1 strain rates. Compressive modulus of foams is higher compared to neat HDPE. Increasing strain rates and decreasing filler content increases yield strength for all the foams investigated compared to neat HDPE. Yield strain and energy absorption of GMB/HDPE foams increases with an increasing strain rate and wall thickness. Specific modulus and strength of GMB/HDPE foams are superior and are comparable to neat HDPE. GMB/HDPE foam achieved high stiffness to weight ratio making them suitable for wide variety of applications. Theoretical model based on differential scheme predicts a good estimate of elastic modulus for all the type of GMB/HDPE foams. Finally, property map is exhibited to present comparative studies with existing literature. [ABSTRACT FROM AUTHOR]

Lightweight porous materials for electromagnetic interference (EMI) shielding applications are reviewed. EMI shielding refers to the capability of a material to protect from electromagnetic fields (EMFs) generated by electronic devices. Traditionally conducting metals are used in EMI shielding applications, which are slowly being replaced by conducting polymer based shields. This review is narrowly focused on understanding the approaches related to porous high EMI shielding composite materials that have very low density values. While metallic fillers can increase the EMI shielding capabilities of polymers, they also increase the weight, which can be offset by inducing the porosity in the matrix. Porosity is found to be effective in providing higher shielding effectiveness at low filler volume fraction due to concentrating the filler in the solid polymers. However, use of gas porosity results in composites with low mechanical properties. This problem can be alleviated to some extent by reinforcing polymer foams with lightweight conductivefillers such as carbon nanofibers (CNFs), carbon nanotubes (CNTs) and graphene. But the properties of pores such aspore size and distribution cannot be effectively controlled in such cases. Syntactic foams containing hollow particle fillers seem to be the best combination of EMI shielding capabilities and mechanical properties. These composites can be either filled with a second phase conducting filler, or hollow particles can be coated with a conducting layer, or hollow particles made of conducting materials can be used as fillers. The hollow particle wall thickness and volume fractions can be optimized to obtain the desired combination of properties in syntactic foams to enable their multifunctional applications. [ABSTRACT FROM AUTHOR]

This work deals with experimental buckling and free vibration behavior of silane-treated cenosphere/epoxy syntactic foams subjected to axial compression. Critical buckling loads are computed from compressive load–deflection plots deduced using universal testing machine. Further, compressive loads are applied in the fixed intervals until critical loading point on different set of samples having similar filler loadings to estimate natural frequency associated with the first three transverse bending modes. Increasing filler content increases critical buckling load and natural frequency of syntactic foam composites. Increasing axial compressive load reduce structural stiffness of all the samples under investigation. Syntactic foams registered higher stiffness compared to neat epoxy for all the test loads. Similar observations are noted in case of untreated cenosphere/epoxy foam composites. Silane-modified cenosphere embedded in epoxy matrix registered superior performance (rise in critical buckling load and natural frequencies to the tune of 23.75% and 11.46%, respectively) as compared to untreated ones. Experimental results are compared with the analytical solutions that are derived based on Euler–Bernoulli hypothesis and results are found to be in good agreement. Finally, property map of buckling load as a function of density is presented by extracting values from the available literature. [ABSTRACT FROM AUTHOR]

Glass microballoon filled ZA8 alloy matrix syntactic foams are studied for the effect of heat treatment on the microstructure, compressive properties and energy absorption capacity. Normalizing and quenching resulted in reduction or dissolution of eutectic (α + η) phase in the matrix alloy. Blocky Al 3 Ni precipitates were observed in the matrix due to the reaction between matrix and the nickel coating of the particles. The average density and porosity of the syntactic foam were around 3 g/cm 3 and 51.5%, respectively. The heat-treated composites had higher yield strength, compressive strength, plateau stress, densification strain and energy absorption capacity than the as-cast composite. The normalized and quenched composites showed the highest compressive strength, plateau stress and energy absorption capacity. In fact, their highest values were 216.8 MPa and 211.9 MPa, 226.9 MPa and 223.4 MPa, and 125.3 MJ/m 3 and 117.7 MJ/m 3 , respectively. The improvement in the compressive properties is attributed to composition homogenization of alloying elements and relief of the residual stresses. The superior properties of syntactic foams compared to those of the conventional metal foams suggest their potential applications in marine vessels and submarine structures. [ABSTRACT FROM AUTHOR]

The advancements in structural materials are guided by the desire of lowering the density and increasing the strength. Composite materials show promise in tuning the density and strength to meet specific design requirements. Lightweight cementitious materials, such as foamed concretes, are generally known to show poor mechanical properties (e.g., compressive strength and elastic modulus). The lack of control over the size, shape, and distribution of air voids severely limits the improvement of mechanical properties in lightweight cementitious materials. This work is focused on manufacturing and examining the mechanical properties of cementitious syntactic foams with hollow glass microspheres. Use of hollow particles to incorporate porosity allows for the control over the size, shape, and volume fraction of voids present in the composite. Hollow glass microspheres with several different densities (0.15–0.60 g/cm 3 ) are used in different volume fractions (20%–50%) to manufacture the cementitious syntactic foams. The results show that cementitious syntactic foams (CSF) have compressive strengths (32–88 MPa) and elastic moduli (10–20 GPa) for a given range of low density (1.15–1.80 g/cm 3 ), which are better than other cellular cementitious materials in the same density range. In-situ micro-CT scan results reveal that the micro-fracture mechanisms in CSFs under compressive loading depend on the microsphere density and aging of the material. [ABSTRACT FROM AUTHOR]

This study focuses on a lightweight syntactic foam constituted by an epoxy matrix filled with polydispersed Glass Microballoons (GMs) up to 0.75 volume fraction. We present experimental results on hydrostatic loading which demonstrate the possibility of different failure modes depending on whether the surface of the composite is painted/coated or not. In order to explain this surprising behaviour, we propose a three-dimensional Finite Element (FE) micromechanical model. First, we develop a cubic MultiParticle Unit Cell (MPUC) which includes 100 randomly placed GMs and accounting for their polydispersion, in terms of both size and radius ratio. This model is validated by subjecting it to effective uniaxial stress and comparing its predictions of the elastic moduli with experimental findings and an analytical homogenisation technique. Second, towards modelling failure, we implement a structural criterion proposed by our group, which posits that any GM undergoes brittle failure when its average elastic energy density reaches a critical value. We then utilise our measurements of the effective strength under uniaxial compressive stress to identify different critical values for selected types of GMs. Third, on the basis of the MPUC, we reach our goal by developing a larger FE model, including 300 GMs, which enables the study of the stress diffusion from the external surface through an appropriately thick layer of composite, under macroscopic uniform pressure. This micromechanical model allows us to demonstrate the influence of the paint/coating on the syntactic foam failure mode through a detailed analysis of the collapsed GMs and the matrix stress state. [ABSTRACT FROM AUTHOR]

In this paper, syntactic foam is investigated as an alternative solid insulation material for cryogenic applications. Compared to conventional insulation materials based on liquid nitrogen, syntactic foam offers advantages like higher dielectric strength and it maintains its dielectric properties even during quenching of superconductors. Being an inhomogeneous material, syntactic foam features numerous interfaces between materials with different dielectric constants, which might be temperature de-pendent. It has been shown in previous investigations that improving bonding quality between materials of syntactic foam can be beneficial for mechanical and electrical strength. A broader variety of foam modifications using coupling agents are investigated in electrical tests for breakdown voltage at both 293 K and 77 K. To examine the initiation of breakdown, partial discharge measurements are performed at both ambient and liquid nitrogen temperature (LNT), and the results are compared to the existing model of electrical breakdown. The application of coupling agents shows no significant overall improvement for ac- and dcbreakdown stress. At LNT, syntactic foams show a higher partial discharge inception field stress, when microspheres are being treatedwith a coupling agent compared to untreated microspheres. [ABSTRACT FROM AUTHOR]

The aim of present study is to clean the dye contaminated wastewater in an efficient and environmentally affordable manner using coal fly ash, a waste by-product of thermal power plant. Initially, the low densities, inert and hollow cenospheres were segregated from coal fly ash which are blended with chitosan in 3:10 stoichiometric ratio via glutaraldehyde cross-linking to prepare chitosan-cenospheres nanosyntactic foam. Further, batch adsorption studies were performed to achieve amplified removal of Disperse Orange 25 and Disperse Blue 79:1 dyes from wastewater with respect to various operational parameters such as pH, adsorbent dose, dye concentration, agitation speed, contact time and temperature. Maximum removal of 90% in case of Disperse Orange 25 and 87% in case of Disperse Blue 79:1 dye were obtained at an optimized nanosyntactic foam dose of 0.2 g/L at pH 6 with agitation speed of 200 rpm at 40 mg/L dye concentrations. Interestingly, the high adsorption capacity of chitosan-cenospheres nanosyntactic foam (∼500.0 mg/g) at 45 °C establishes the superiority of the aforementioned technique compared to works reported earlier for dyes removal. Furthermore, isotherm and kinetic studies along with thermodynamic parameters substantiated that spontaneous and exothermic monolayer adsorption of the dyes occur onto chitosan-cenospheres nanosyntactic foam following pseudo second order reaction kinetics. Reusability of chitosan-cenospheres nanosyntactic foam for four successive runs were carried out to ensure sustainable use of this adsorptive technique. The present work offers a pragmatic tool for water pollution abatement control, especially pollution from textile effluents by utilizing a waste by-product as adsorbent. [ABSTRACT FROM AUTHOR]

Glass microballoon syntactic foams consisting of 60–70 vol% hollow glass microballoons and epoxy resin matrix have gained considerable attention in recent years due to their unique combination of mechanical properties and low density, with applications in the naval and aerospace industries. An important limitation of these materials is the volume fraction ceiling (∼0.74) and subsequent density limit (0.36 g/cm3). Utilizing thermoplastic microballoons, syntactic foams were produced with densities as low as 0.067 g/cm3, achieved by developing a method that produces epoxy/microballoon compositions comprising an unusually high volume fraction of microballoons (0.75–0.95). The resulting morphology features microballoons which, having expanded in a restricted volume, are deformed into irregular shapes that efficiently pack together and are encapsulated by a thin coating of epoxy. The compressive yield strength, tensile strength and initial modulus of these highly loaded syntactic foams exhibit a non-linear decrease with increasing microballoon volume fraction to values typical of highly porous polymers, but display a high degree of recovery, or rebound, from large compressive strain compared with glass microballoon syntactic foams. [ABSTRACT FROM AUTHOR]

Syntactic foams are commonly fabricated with sodalime–borosilicate glass hollow microsphere fillers, which are susceptible to degradation after long-term or high temperature moisture exposure. In comparison, borosilicate glass hollow particles offer higher degradation resistance to moisture, lower thermal expansion, and higher softening temperature. This work explores borosilicate glass hollow microspheres for use as fillers in syntactic foams and studies their thermophysical properties. The coefficient of thermal expansion over the temperature range 35–90℃ was observed to decrease from 62.4 μ/K for the matrix resin to a minimum of 24.3 μ/K for syntactic foams, representing higher thermophysical stability of syntactic foams. Theoretical models are used to conduct parametric studies and understand the correlation between material parameters and coefficient of thermal expansion of syntactic foams. The dynamic mechanical analysis results show that the storage modulus of syntactic foams increases with increasing glass hollow microsphere wall thickness and with decreasing glass hollow microsphere volume fraction in the glassy region at 40℃. The β-relaxation of the matrix resin found at 66.1 ± 2.0℃ was suppressed in the majority of syntactic foams, further improving the stability around typical application temperatures. [ABSTRACT FROM AUTHOR]

Syntactic foam is a lightweight and strong material which can be used in marine and aeronautical applications. However, the brittleness of the material limits its application to a broader range. Adding crumb rubber to the syntactic foam can increase its energy absorption capacity. The effect of crumb rubber on the fracture toughness and energy absorption capacity of 2-phase and 3-phase syntactic foam is evaluated under both static and impact loads. The experimental results have shown that the fracture toughness of the 2-phase rubberized syntactic foam increased by 8% while an increase of 22% of its fracture energy was observed. Under quasi-static loads, the 3-phase rubberized syntactic foam showed decreases in the compressive strength and elastic modulus but an increase in the energy absorption capacity as compared to the syntactic foam without crumb rubber. In addition, the impact energy absorption of the 3-phase rubberized syntactic foam increased by 24% as compared to that of the 3-phase syntactic foam without crumb rubber. [ABSTRACT FROM AUTHOR]

Syntactic foams comprising glass microballoons have gained considerable attention over the past several years due to mechanical and thermal properties that are advantageous for use as a core material in naval and aerospace applications. Recent advancements in the production of thermoplastic microballoon syntactic foams have allowed for an increase in microballoon volume fraction (up to 0.9 volume fraction), with correspondingly lower densities but reduced mechanical properties. In this work, carbon nanofibers and halloysite nanotubes were incorporated in thermoplastic microballoonbased syntactic foam to enhance the mechanical properties and the relative effects of these two nanoscale reinforcements were compared. X-ray micro-computed tomography was employed to analyze the microstructure of the materials produced, and scanning electron microscopy was used to assess the dispersion of nano-additives within the resin. Compressive strength and modulus enhancements as large as 180% and 250% respectively were achieved with a 0.25 wt% addition of carbon nanofiber and increases of 165% and 244% respectively were achieved with a 0.5 wt% addition of halloysite nanotube. Tensile strength and modulus enhancements as large as 110% and 165% respectively were achieved with a 0.125 wt% addition of carbon nanofiber and increases of 133% and 173% respectively were achieved with a 0.125 wt% addition of halloysite nanotube. [ABSTRACT FROM AUTHOR]

In this study, syntactic foams with honeycomb like structure were prepared with hollow glass microspheres (HGMs), epoxy resin, and expanded polystyrene (EPS) beads. A novel manufacturing approach of Vacuum Assisted Resin Transfer Mould (VARTM) was designed to avoid the effect of buoyancy on the EPS beads, due to the different densities of the raw materials. The EPS beads were served as sacrificial templates and shrank at high temperature, and thus produced hollow structure. EPS beads with four types of size were used. The average diameters are 0.75 mm, 1.50 mm, 2.50 mm and 4.00 mm, respectively. The foam density of the obtained syntactic foam can vary from 0.24 g/cm 3 to 0.28 g/cm 3 . It was demonstrated by scanning electron microscope (SEM) that the EPS beads and HGMs could be dispersed uniformly in the resin system. Test results indicated that the resin permeating time, compressive strength, and syntactic foam densities presented an increasing tendency as the decrease of the EPS beads' diameters. Correspondingly, the average compressive strength enhanced from 3.6 MPa to 9.3 MPa. The resin permeating time increased from 6 min to 27 min with a thickness of 100 mm. In summary, this work provides an optimized way for the preparation of the low-density syntactic foams. [ABSTRACT FROM AUTHOR]

In order to examine the effect of microballoons type on microstructure and compressive deformation behaviour of aluminum syntactic foam, alumina reinforced and cenosphere reinforced aluminum syntactic foams have been made through stir-casting technique. Alumina microballoons reinforced aluminum syntactic foam (AMRASF) has been developed using stir casting technique. Volume fraction of alumina microballoons in AMRASF varies in the range of 0.39–0.74. The compressive deformation behavior of these AMRASF is compared with that of cenosphere reinforced aluminum syntactic foam (CPRASF). The AMRASF does not exhibit clear plastic collapse stage as observed in case of CPRSAF. It is further noted that AMRASF shows the existence of work hardening phenomena after yielding but CPRASF does not show any significant work hardening after yielding even at higher relative densities of foam. This is explained on the basis of characteristics of alumina microballoons and cenospheres and interface characteristics between matrix and respective microballoons used. Effect of individual microballoons’ characteristics on the foam properties has also been explained. [ABSTRACT FROM AUTHOR]

In this paper, the effects of arctic condition on the compressive response of ceno-sphere/epoxy syntactic foams are investigated. Understanding the behavior of such foams under extreme conditions is critical for exploring their suitability for constructing lightweight platforms used in arctic explorations, which are exposed to subzero temperatures for extended periods of time potentially degrading their mechanical properties. In the research study presented here, samples of cenosphere/epoxy syntactic foams were conditioned under arctic environment at a temperature of −60 °C for a period of 57 days. Compression tests were then conducted at room temperature as well as in-situ −60 °C on the conditioned samples and compared against unconditioned samples tested at room temperature. Combinations of surface modification and cenosphere volume fractions were considered. For the case of unconditioned samples, compressive strength decreased with increasing cenosphere volume fraction for both surface modified and unmodified cenospheres. For the arctic conditioned samples, cenospheres/epoxy foams did not present visible signs of degradation prior to testing, but manifested a reduction in compressive modulus in a range of 47–57% and 47–65% for untreated and treated cenospheres/epoxy syntactic foams as compared to their unconditioned counterparts. On the other hand, the compressive strength increased in a range between 32–68% for untreated and 59–80% for treated cenosphere foams in arctic environment, which can be attributed to the matrix hardening introduced by frigid in-situ environment. Also, under in-situ arctic compressive loading, the post peak response for all foam types have shifted from a progressive failure to a brittle type behavior. [ABSTRACT FROM AUTHOR]

Mechanical properties of ternary composites consisting of fibres, particles and polymer matrix are strongly influenced by the interface combination status of the three components. We investigated the interfacial bond properties of fibre-microballoon-epoxy ternary composites using a microbond test and finite element simulation. The finite element simulation using ANSYS software predicted force-displacement curves and interfacial shear strength (IFSS) consistent with those determined by the microbond test for a wide range of fibre-microballoon-epoxy ternary composites. It is found that fibre diameter has the largest influence on the IFSS of the ternary composites, followed by the volume fraction and size of the microballoon particle. The von Mises and contact friction stress contour plots from the simulation models were used to explain the influences of these parameters on the IFSS of the ternary composites determined by the microbond test. [ABSTRACT FROM AUTHOR]

In this study, a theoretical model based on the fiber buckling theory was established to predict the compression strength of a new type of syntactic foam, namely the syntactic foam reinforced by the warp-knitted spacer fabric (SF-WKSF). In order to verify the availability of this model, compression strength values of theoretical simulations were compared with the experiment results. The comparison results showed that the model can accurately simulate the compression strength values of different SF-WKSF samples with slight deviation. Finally, the causes of deviation was analyzed in detail. [ABSTRACT FROM AUTHOR]

Shock tube experiments were performed to investigate the blast response of corrugated steel cellular core sandwich panels filled with a silicone based syntactic foam at room and high temperatures. The syntactic foam filler was prepared by mixing a two-part silicone mixture with glass microspheres; its microstructure, and mechanical properties were also characterized. The syntactic foam-filled sandwich panels were loaded via air shock pressure by using the shock tube with a fixture capable of testing materials at temperatures up to 900℃. High-speed photo-optical methods, digital image correlation techniques, were used in tandem with optical band-pass filters and high intensity light sources for providing sufficient contrast at elevated temperatures. Back-face deformation images were captured using two synchronized high-speed cameras while a third camera captured the side view deformation images. The shock pressure profiles and digital image correlation analysis were used to obtain the impulse imparted to the specimen, transient deflection, in-plane strain and out-of-plane velocity of the back-face sheet. It was observed that using the syntactic foam as a filler material decreased the front face and back face deflections by 42% and 27%, respectively, as compared to the empty sandwich panel. At high temperatures, the silicone-based syntactic foam decomposes into silica, a stable and non-hazardous byproduct. The highest impulse was imparted to the specimen at room temperature and subsequently lower impulses with increasing temperatures were observed. Due to the increased ductility of steel at high temperatures, the specimens demonstrated an increase in back face deflection, in-plane strain and out-of-plane velocity with increased temperatures, with weld failure being the primary form of core damage. [ABSTRACT FROM AUTHOR]

Graphite reinforced hollow epoxy macrospheres (GR-HEMS) and hollow glass microspheres (HGMS) were used to prepare three phase epoxy syntactic foam (ESF) using 'molding method', and the physical and mechanical properties of ESF were also studied and investigated. An innovative 'rolling ball method' was implemented in the GR-HEMS preparation process. The performance tests show that higher GR-HEMS stacking volume fraction, lower GR-HEMS thickness, higher GR-HEMS diameter, higher HGMS volume fraction, lower HGMS density are beneficial to reducing the density of ESF, but the effects of the five factors on the strength of ESF are the opposite. Therefore, in order to obtain 'high strength and low density' ESF composites, the various factors should be considered to achieve a balance of the strength and the density. Scanning electron microscope (SEM) shows that the 'rolling ball method' can make graphite form a graphite spherical x-y network throughout the macrosphere wall, which can make GR-HEMS and ESF have great compressive strength. The ESF (450 kg/m, 20.75 MPa) can withstand the 2075 meters water pressure and provide 550 kg/m buoyancy, which can give some advice to the preparation of buoyancy material used in deepwater oil exploration. [ABSTRACT FROM AUTHOR]

In this work, PEDOT: PSS syntactic foams with different glass bubbles (GB) contents were prepared. The effect of the generated microstructure on the electrical conductivity and its thermal stability were experimentally studied. Additionally, a finite element analysis was carried out to determine the effect of microstructures of the syntactic foams on the prediction of their electrical and thermal conductivity. The result of DMSO doping on electrical conductivity was also analyzed. The syntactic foams showed two types of microstructures depending on the content of GB. The most efficient material to conduct the electric field was obtained with 75 wt % of GB because an electrically conductive segregated network was formed. The finite element simulation showed that the microstructure is not the only key factor in improving electrical conductivity; being the intrinsic electrical conductivity of the matrix also very important. Doping with DMSO increased, even more, the electrical conductivity of the foams with high percentages of GB. Finally, the thermal stability was positively influenced by the microstructure with segregated phases and by the low thermal conductivity of the materials. Essentially, this work reveals a novel and more sustainable process for generating materials like aerogels which potentially could be used as thermoelectric material. [Display omitted] • Syntactic foam of PEDOT: PSS with high content of glass increases the electrical conductivity. • Finite Element Analysis could be a powerful tool for predicting the electrical and thermal conductivity of syntactic foams. • Novel and more sustainable process for generating materials like aerogels with potential thermoelectrical applications. [ABSTRACT FROM AUTHOR]