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Toledo, OH, United States

Shunmugasamy V.C.,New York University | Zeltmann S.E.,New York University | Gupta N.,New York University | Strbik III O.M.,Deep Springs Technology
JOM | Year: 2014

Silicon carbide hollow spheres are compression tested to understand their energy absorption characteristics. Two types of particles having tap densities of 440 kg/m3 and 790 kg/m3 (referred to as S1 and S2, respectively) were tested in the present study. The process used to fabricate the hollow spheres leads to porosity in the walls, which affects the mechanical properties of the hollow spheres. The porosity in the walls helps in obtaining mechanical bonding between the matrix material and the particle when such particles are used as fillers in composites. The single-particle compression test results show that the S1 and S2 particles had fracture energies of 0.38 9 10̃3 J and 3.18 9 10̃3 J, respectively. The modulus and fracture energy of the particles were found to increase with increasing diameter. However, the increasing trend shows variations because the wall thickness can vary as an independent parameter. Hollow particle fillers are used in polymer and metal matrices to develop porous composites called syntactic foams. The experimentally measured properties of these particles can be used in theoretical models to design syntactic foams with the desired set of properties for a given application. © 2014 The Minerals, Metals & Materials Society.

Yaseer Omar M.,New York University | Xiang C.,New York University | Gupta N.,New York University | Strbik O.M.,Deep Springs Technology | Cho K.,U.S. Army
Materials Science and Engineering A | Year: 2015

The present work is the first attempt to study metal matrix syntactic foam core sandwich composites. The sandwich is studied for microstructure and compressive properties at quasi-static and high strain rates. Under quasi-static compressive conditions, specimens were tested in the flatwise and edgewise orientations. The compressive strength, yield strength and plateau stress were higher in the flatwise orientation. Furthermore, both orientations for the sandwich composites showed a higher specific compressive strength and specific yield strength than the foam core alone. Failure initiated in the particles in the flatwise orientation, but in the carbon fabrics in the edgewise orientation. The results show that the fabric had a reinforcing effect under quasi-static conditions. The high strain rate (HSR) characterization was conducted in the strain rate range 525-845s-1 using a split-Hopkinson pressure bar set-up equipped with a high speed image acquisition system. Within this strain rate range, the compressive strength of the sandwich is similar to that of the syntactic foam core alone. Upon review, the syntactic foam core metal matrix sandwich outperforms most of the syntactic foams in terms of energy absorption and compressive strength at comparable density levels. © 2015 Elsevier B.V.

Omar M.Y.,New York University | Xiang C.,New York University | Gupta N.,New York University | Strbik O.M.,Deep Springs Technology | Cho K.,U.S. Army
Materials and Design | Year: 2015

The present work aims at characterizing a metal matrix syntactic foam core sandwich composite under three-point bending conditions. The sandwich comprises alumina hollow particle reinforced A356 alloy syntactic foam with carbon fabric skins. Crack initiation in the tensile side of the specimen causing failure of the skin, followed by rapid failure of the core in the direction applied load, is observed as the failure mechanism. Crack propagation through the alumina particles is observed in the failed specimens instead of interfacial failure. The average maximum strength, flexural strain and stiffness were measured as 91.2 ± 5.6. MPa, 0.49 ± 0.06% and 20.6 ± 0.7. GPa respectively. The collapse load is theoretically predicted using mechanics of sandwich beams. Experimental values show good agreement with theoretical predictions. © 2015 Elsevier Ltd.

Licitra L.,New York University | Luong D.D.,New York University | Strbik O.M.,Deep Springs Technology | Gupta N.,New York University
Materials and Design | Year: 2015

Dynamic properties of two aluminum alloy A356/alumina hollow particle syntactic foams that have densities of 1.61 and 2.11g/cc are studied. The materials are characterized for quasi-static (10-3s-1) and high strain rate (445-910s-1) compression. The results show that the lower density syntactic foam has lower modulus, compressive strength and plateau stress, but the lower density provides better specific properties than either the A356 alloy and higher density syntactic foam. The fracture mechanism of the syntactic foams was investigated by using high speed cameras. The particle failure is found to initiate the failure in the specimen, followed by shear failure of the matrix and particles. The A356 alloy and syntactic foams are also characterized for their dynamic mechanical properties to understand the effect of temperature and loading frequency on the storage and loss moduli and damping parameter. The storage modulus of A356 matrix and syntactic foams decreases but the loss modulus and damping parameter increase as the temperature increases. At the same temperature, the lower density material has lower storage modulus and loss modulus. The storage modulus of A356 alloy decreases steeply as the temperature is increased above 375°C, whereas syntactic foams demonstrate better thermal stability. © 2014 Elsevier Ltd.

Labella M.,New York University | Shunmugasamy V.C.,New York University | Strbik O.M.,Deep Springs Technology | Gupta N.,New York University
Journal of Applied Polymer Science | Year: 2014

Silicon carbide hollow particle (SiCHS) reinforced vinyl ester matrix syntactic foams are prepared and characterized for compressive properties and coefficient of thermal expansion (CTE). Two types of SiCHS were utilized in 60 vol % to prepare syntactic foams. These SiCHS had ratio of inner to outer radius of 0.91 and 0.84 for the thin and thick walled particles. The specific compressive strength values were 33.4 and 38.8 kPa/kg/m3 and the specific compressive modulus values were 0.8 MPa/kg/m3 and 0.6 MPa/kg/m3 for the thin and thick walled SiCHS-filled syntactic foams, respectively. The shell of the hollow particles contained microporous voids, and the porosity was estimated as 16.6% and 24.8% in the walls of the thin and thick walled particles, respectively. The shell porosity adversely affected the specific compressive strength and the modulus of the syntactic foam. However, the SiCHS-filled syntactic foams exhibited low CTE values (26.7 and 15.9 × 10-6/°C). These CTE values were 65.1% and 79.3% lower than the CTE of the neat resin. Such properties can be useful for applications where syntactic foams are exposed to high temperatures and dimensional stability is important. A theoretical model is used to estimate the porosity level in the SiC shells and estimate the effective mechanical properties of the porous SiC material that forms the particle shell. Such analysis can help in using the models as predictive tools to estimate the mechanical properties of syntactic foams. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40689. Copyright © 2014 Wiley Periodicals, Inc.

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