Syntactic Foam

This paper presented the stress concentration factor (SCF) around the half circular edge of tensile specimens made of syntactic foam using finite element software Strand7 software. The study is a preliminary effort, which investigates the effect of variations of crack geometry on the stress concentration factor on a tensile specimen subjected to a constant, uniform, uniaxial tensile load. The material property is graded for varying Young's Modulus and Poisson's Ratio with different composition of glass microballoons. Finally, a uniform pressure is applied at the top and the model is constrained with symmetric boundary conditions at the left and bottom. As the result, these numerical results for both SCF experimental and simulation model are compared to those obtained from analytic fracture mechanics procedures and are found to be varied. In addition, the SCF is sensitive to the modulus of elasticity, particularly for lower composition weight percentage (wt.%), while it is also varied with the different weight percentage (wt.%) of glass microballoons, which is led by 2 wt.% specimen.

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 com-pressive 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.

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 (0.15e0.60 g/ cm 3) are used in different volume fractions (20%e50%) to manufacture the cementitious syntactic foams. The results show that cementitious syntactic foams (CSF) have compressive strengths (32e88 MPa) and elastic moduli (10e20 GPa) for a given range of low density (1.15e1.80 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.

This work aims at understanding the effect of particle–matrix interfacial debonding on the tensile response of syntactic foams. The problem of a single hollow inclusion with spherical-cap cracks embedded in a dissimilar matrix material is studied. Degradation of elastic modulus, cavity formation in the proximity of debonded regions, stress localization phenomena in the inclusion, debonding energetics, and crack kinking are studied for a broad range of inclusion wall thickness and debonding extent. A series solution based on ...

The hollow sphere epoxy were produced by the coating of expended polystyrene (EPS) by the epoxy before the EPS were shrank and produce the hollow sphere epoxy. The main variables that focused in this research are closely related to the epoxy hollow sphere (EHoS). There are two distinct size of EHoS were studied in this research. Besides that, the thickness of the epoxy layer that coated the hollow sphere was also the important parameter that has been observed along of this study. There were several testing run to determine the mechanical and physical properties of the different cell size ESF and different cell wall thickness of EHoS in the ESF.

The production of low-temperature clay lightweight aggregates is pursued eagerly as low energy and low cost lightweight aggregate concrete (LAC) building blocks become more popular. Clay ceramic hollow spheres (CCHS) with waste glass (WG) additive was developed and studied as aggregate in cement composite. CCHS with diameter 6-8 mm were produced by a sacrificial template technique with subsequent sintering at 900 °C. CCHS had differing WG content of 0 wt%, 5 wt%, 7 wt% or 10 wt%. The effect of sintering temperature and WG content on physical properties and morphology of the CCHS-cement composites were studied by means of optical microscopy and mechanical tests. Obtained composite materials were compared to commercially available lightweight fillers-foamed glass granules or lightweight expanded clay aggregates (LECA). The compressive strength of CCHS containing LAC is much higher (4.8–7.1 MPa) compared to LECA-cement LAC (3.5 MPa). Reduction of CCHS open porosity due to higher content of WG (10 %) leads to lower absorption of cement paste. This allows lower cement
consumption, lower bulk density and higher compressive strength. LAC with CCHS proved to be promising construction material due to low-temperature production process (i), widely available raw material (clay) and secondary material (glass cullet) (ii), reduction of amount of cement paste needed for material production (iii).

Quasi-static and dynamic experiments are conducted to characterise the mechanical response of a syntactic foam comprising hollow glass microballoons in a polyurethane matrix. Stress versus strain histories are measured in uniaxial tension and compression as well as in pure shear, at strain rates ranging from 10
'4 to 10'3 s
1, via non-standard experimental techniques; quasi-static in-situ tests are conducted to visualise the deformation mechanisms in tension and compression. The material displays a pronounced sensitivity to the imposed strain rate and relatively high tensile and shear ductility at both low and high strain rates. A tension/compression asymmetry is displayed in quasi-static tests but is lost at high rates of strain.

The present work was focused on studying the strain rate sensitivity of cementitious syntactic foams (CSF), which are particulate composites reinforced with hollow glass microspheres (HMG). Different density CSFs (1.31-1.74 g/cm 3) with different volume fractions (20-40%) of HGMs were tested with a split-Hopkinson pressure bar setup. The true particle densities of the HGMs were in the range of 0.38-0.60 g/cm 3. In addition, the macro-and micro-scale failure mechanisms were investigated with high-speed camera imaging, micro-CT scanning, and electron microscopy. The results showed that both the CSFs and the baseline material (control sample), which is the cement paste matrix of the CSFs, showed strain rate sensitivity in mechanical properties in the 10 2-10 3 s −1 strain rate range. CSFs had relatively lower strain rate sensitivity in comparison to the matrix material. In the same range of strain rate, both the CSFs and the control sample showed significant changes in their macro and micro failure mechanisms depending on their age, composition and loading rate. The level of damage at the peak load for the high strain rate was higher in comparison to the same materials tested under quasi-static loading conditions for CSFs and the cement matrix.

The present work is aimed at characterizing syntactic foams for flatwise (specimen aspect ratio of 0.5) properties and investigating the effect of change in the internal radius of cenospheres. The density and mechanical properties of the syntactic foam can be ...

Novel syntactic foams for potential building material applications were developed using starch as binder and ceramic hollow micro-spheres available as waste from coal-fire power stations. Foams of four different micro-sphere size groups were manufactured with ...

Recent studies have shown cementitious syntactic foams (CSF) to have great potential as a low density and high strength structural material. However, CSFs are made with hollow glass microsphere (HGM) inclusions and cementitious materials with amorphous silica inclusions such as glass are known to have a potential for the deleterious alkali silica reaction (ASR). In this study, CSFs containing HGMs are tested for ASR expansion and compressive strength along with solid particles of soda-lime and borosilicate glass to compare. Results show that in the 30-90 μm average particle size range, only solid borosilicate particles lead to more than 0.2% expansion of the composite material in an accelerated ASTM C1260 lab test for ASR, which is considered as the limit for deleterious effects. Similarly, compressive strength tests show that only solid borosilicate particles lead to reduced compressive strengths (from ~95 to ~40 MPa) in the long term, while CSFs showed no sign of loss of compressive strength even at extremely alkaline conditions. Scanning electron microscopy investigations suggest that CSFs are safe from ASR expansion of the composite and internal stresses due to their hollow geometry, which provides reservoir space for the alkaline silica gel expansion and mitigates the ASR effects.

Syntactic foams are hollow particle filled composites that have recently emerged as attractive materials for use in advanced structural applications. The present study focuses on the effect of radius ratio and volume fraction of microballoons on the ultrasonic properties of syntactic foam composites. Twenty-four different types of syntactic foams, with different radius ratios and volume fractions, are used in this