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Anantharaman H.,New York University | Shunmugasamy V.C.,New York University | Strbik O.M.,Deep Springs Technology | Gupta N.,New York University | Cho K.,U.S. Army
International Journal of Impact Engineering | Year: 2015

Metal matrix syntactic foams of very low density (0.97 g/cc) were prepared using silicon carbide hollow particles dispersed in a magnesium alloy (AZ91D) matrix. The composite was evaluated for quasi-static and high strain rate (1330-2300/s) compression and dynamic mechanical properties. The compression test results show that the peak stress and the elastic energy absorbed were strain rate sensitive and the values at high strain rates were up to 1.5 times higher than the quasi-static values. The failure mechanisms of syntactic foams at high strain rates were observed to be failure of the hollow particles, plastic deformation of the matrix and fracture of precipitates that are oriented along the grain boundaries of the alloy. Extensive dynamic mechanical analysis was conducted under the conditions of (a) temperature variation at a constant frequency and (b) frequency variation over a wide range of temperatures to conduct time-temperature superposition (TTS). The damping parameter of the composites was observed to be higher than those of the matrix alloy at all temperatures. The TTS principle allowed extrapolating the material behavior over a wide frequency range from a limited frequency dataset range of 1-100 Hz. Such very low density syntactic foams can be useful in marine vessel and aerospace structures for weight saving. In addition, composites in this density range can directly compete with polymer matrix composites with added advantage of dimensional stability and mechanical property retention at higher temperatures. © 2015 Elsevier Ltd. All rights reserved.


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.


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.


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.


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.


Grant
Agency: Department of Defense | Branch: Navy | Program: STTR | Phase: Phase I | Award Amount: 150.00K | Year: 2011

Under this STTR, Deep Springs Technology (DST) in cooperation with Georgia Tech will demonstrate the feasibility of producing affordable high strength Mo-Si-B extrusions based on the Georgia Tech method of ultrasonic spray drying Mo, Si3N4, BN powders, reaction/sintering of the granules at high temperatures to MoSiB composites, and reduction extruding granules at high temperature into dense composite rods. As detailed below, the GT Reaction Sintered (GTRS) process has been demonstrated to provide low interstitial impurities (O, C, N) and to produce both microstructures, oxidation resistance, and high temperature, high strength, ductility competitive with MoSiB composites from other processes. However, high temperature extrusion or similar deformation which imparts substantial mechanical work is believed to be required for MoSiB composites to produce defect free, structural material on an industrial scale with the necessary reliability required for high safety margin applications such as aircraft engines. If successful, developments under this STTR will increase high temperature strength, extent ductility to lower temperatures, maintain reasonable oxidation resistance and low interstitial impurity concentration. These advances would open a range of applications above 1100oC because no reasonable cost metal is available in this arena.


Grant
Agency: Department of Defense | Branch: Navy | Program: STTR | Phase: Phase I | Award Amount: 80.00K | Year: 2013

The objective of the work described in this proposal is to aid in the advancement of Mo-Si-B alloys for use in high temperature applications such as hot gas stream components in turbine engines. Such alloys are being characterized for their monotonic tensile properties in tension and compression as well for their creep resistance. Likewise, multiphase Mo-Si-B alloys have been studied in terms of monotonic and cyclic crack growth and creep fatigue interactions. Less is known about their cyclic deformation response. Computer modeling has been applied to the Mo-Si-B alloy system. However, only 2D studies have been conducted on this material. The accuracy of prediction was found to be very good when the 2D microstructure based simulations were conducted. These studies can be extended to model the failure mechanisms with high level of accuracy because of capturing the stress profile in the material with very high level of accuracy, including the stress concentration location and magnitude and crack length for intergranular fracture. The present work will strive to develop 3D models of the alloy microstructure, and conduct analysis over a range of temperatures and strain rate; all of which are not yet available for this alloy in the existing studies.


Grant
Agency: Department of Defense | Branch: Navy | Program: STTR | Phase: Phase II | Award Amount: 500.00K | Year: 2012

Under this STTR, Deep Springs Technology (DST) in cooperation with Georgia Tech is testing the feasibility of producing high strength Mo-Si-B composites based on the Georgia Tech method of ultrasonic spray drying Mo, Si3N4, BN powders, reacting the granules at high temperatures to MoSiB composites, and reduction extruding the sintered granules at high temperature into dense composite rods. The GT Reaction Sintered (GTRS) process, in Mo3Si1B composition, has been demonstrated to provide low interstitial impurities (O, C, N) and to produce both microstructures, oxidation resistance up to 1200C, and high temperature, high strength, ductility competitive with MoSiB composites from other processes. However, high temperature extrusion or similar deformation may be required for MoSiB composites to have oxidation resistance to 1300C and to produce defect free, structural material on an industrial scale with the necessary reliability required for high safety margin applications such as aircraft engines.


Grant
Agency: NSF | Branch: Standard Grant | Program: | Phase: | Award Amount: 145.70K | Year: 2010

This Small Business Innovation Research (SBIR) Phase I Project is focused on research to develop reinforced silicon carbide hollow spheres. This effort will apply a modified version of its proprietary hollow sphere production process in combination with novel materials. Novel characteristics resulting from the hollow sphere structure to be realized include: low cost bulk production of individual loose hollow spheres, uniform shape, uniform dimensions, dimensional stability, and low apparent density. Additionally, the hollow spheres will possess the important structural and thermal characteristics of silicon carbide including extreme hardness, high thermal conductivity, low thermal expansion coefficient, thermal shock resistance, high abrasion resistance, high melting point, and high resistance to oxidation or corrosion caused by other materials. These hollow spheres will ultimately be used to form continuous complex net shapes.

The broader impact/commercial potential of this project will be the availability of lightweight, high-strength, high-temperature material structures not previously possible. Hollow silicon carbide spheres have commercial potential for high-performance applications, especially for net shape superstructures in supersonic and hypersonic aircraft, spacecraft, and missiles. These materials find specific applications in high-temperature environments, such as the exterior surfaces of space reentry vehicles, inside combustion chambers, and as nozzles in jet engines, rocket engines, and power generators. Hollow silicon carbide spheres have applications that include thermal insulation, impact absorption (armor), catalyst support, metal and gas filtration, automotive heat engines, and mechanical seals. The knowledge generated about silicon carbide during this project can also be transferred to other related materials such as boron carbide.


PubMed | U.S. Army, Deep Springs Technology and New York University
Type: | Journal: Data in brief | Year: 2015

Microstructural observations and compressive property datasets of metal matrix syntactic foam core sandwich composite at quasi-static and high strain rate (HSR) conditions (525-845s(-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.

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