publications

Metal Matrix Syntactics - Emerging Possibilities In Search Of Innovative Minds


The presentation is an overview of Metal Matrix Syntactic materials and highlights Deep Springs Technology’s exploration of this adaptable material system. Previously presented at the Ohio Innovation Summit October 2014 sponsored by The University of Dayton Research Institute.



Dynamic and Thermal Properties of Aluminum Alloy A356/Silicon Carbide Hollow Particle Syntactic Foams

James Cox, Dung D. Luong, Vasanth Chakravarthy Shunmugasamy, Nikhil Gupta, Oliver M. Strbik III, and Kyu Cho

Aluminum alloy A356 matrix syntactic foams filled with SiC hollow particles (SiCHP) are studied in the present work. Two compositions of syntactic foams are studied for quasi-static and high strain rate compression. In addition, dynamic mechanical analysis is conducted to study the temperature dependent energy dissipation and damping capabilities of these materials. The thermal characterization includes study of the coefficient of thermal expansion (CTE). A356/SiCHP syntactic foams are not strain rate sensitive as the compressive strength displayed little variation between the tested strain rates of 0.001–2100 s−1. Microscopic analysis of the high strain rate compression tested specimens showed that the fracture is initiated by the failure of hollow particles at the onset of the plastic deformation region. This is followed by plastic deformation of the matrix material and further crushing of particles. The syntactic foams showed decrease in storage modulus with increasing temperature and the trend was nearly linear up to 500 °C. The alloy shows a similar behavior at low temperature but the decrease in storage modulus increases sharply over 375 °C. The loss modulus is very small for the tested materials because of lack of viscoelasticity in metallic materials. The trend in the loss modulus is opposite, where the matrix alloy has lower loss modulus than syntactic foams at low temperature. However, over 250 °C the matrix loss modulus starts to increase rapidly and attains a peak around 460 °C. Syntactic foams have higher damping parameter at low temperatures than the matrix alloy. Incorporation of SiCHP helps in decreasing CTE. Compared to the CTE of the matrix alloy, 23.4 × 10−6 °C−1, syntactic foams showed CTE values as low as 11.67 × 10−6 °C−1.

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High Strain Rate Compressive Behavior of Polyurethane Resin and Polyurethane/Al2 O3Hollow Sphere Syntactic Foams

Dung D. Luong, Vasanth Chakravarthy Shunmugasamy, Oliver M. Strbik III, and Nikhil Gupta

Polyurethane resins and foams are finding extensive applications. Seat cushions and covers in automobiles are examples of these materials. In the present work, hollow alumina particles are used as fillers in polyurethane resin to develop closed-cell syntactic foams. The fabricated syntactic foams are tested for compressive properties at quasistatic and high strain rates. Strain rate sensitivity is an important concern for automotive applications due to the possibility of crash at high speeds. Both the polyurethane resin and the syntactic foam show strain rate sensitivity in compressive strength. It is observed that the compressive strength increases with strain rate. The energy absorbed up to 10% strain in the quasistatic regime is 400% higher for the syntactic foam in comparison to that of neat resin at the same strain rate.

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Metal Matrix Syntactic Foams

Oliver M. Strbik (Contributing Author), Nikhil Gupta & Pradeep Rohatgi (Editors), June 2014, DEStech

Focused on a new type of material, the book investigates the elements, synthesis and practical applications of metal matrix syntactic foams, which share properties of foams and metal matrix composites. The text reviews how syntactic foams are synthesized from different types of hollow particles and metal matrixes. Part one explains processing techniques such as solidification and powder metallurgy and discusses foams made from a variety of matrix metals. Part two compares different syntactic foams based on density and strain rate. Original experimental data and modeling information are provided that show how metal matrix syntactic foams can be used for lighter weight components in vehicles, as well as for sensors and biomaterials.

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Compressive Characterization of Single Porous SiC Hollow Particles

Vasanth Chakravarthy Shunmugasamy, Steven E. Zeltmann, Nikhil Gupta and Oliver M. Strbik III, JOM, June 2014, Volume 66, Issue 6, pp 892-897 DOI: 10.1007/s11837-014-0954-7

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 (referrred 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 X 10-3 J and 3.18 X 10-3 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.

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Compressive and thermal characterization of syntactic foams containing hollow silicon carbide particles with porous shell

Matthew Labella, Vasanth Chakravarthy Shunmugasamy, Oliver M. Strbik III and Nikhil Gupta, Journal of Applied Polymer Science, 2014, 131, 40689

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. 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 x 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 temperatues 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.

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Dynamic properties of alumina hollow particle filled aluminum alloy a356 matrix syntactic foams

Luca Licitra; Dung D Luong, Ph.D.; Oliver M Strbik III; Nikhil Gupta, Journal Materials and Design (2014), DOI: 10.1016/j.matdes.2014.03.041

Dynamic properties of two aluminum alloy A356/alumina hollow particle syntactic foams that have densities of 1.61 and 2.11 g/cc are studied. The materials are characterized for quasi-static (10-3 s-1) and high strain rate (445-910 s-1) compression. The result shows that the lower density syntactic foam has lower modulus, compressive strength and plateau stress, but the lower density provides better specific properties than the A356 alloy and higher density syntactic foam. The fracture mechanism of their 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 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 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 but syntactic foams show better thermal stability.

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Applications of Polymer Matrix Syntactic Foams

Nikhil Gupta, Steven E. Zeltmann, Vasanth Chakravarthy Shunmugasamy, and Dinesh Pinisetty(2013) JOM, The Minerals, Metals & Materials Society, DOI: 10.1007/s11837-013-0796-8

A collection of applications of polymer matrix syntactic foams is presented in this article. Syntactic foams are lightweight porous composites that found their early applications in marine structures due to their naturally buoyant behavior and low moisture absorption. Their light weight has been beneficial in weight sensitive aerospace structures. Syntactic foams have pushed the performance boundaries for composites and have enabled the development of vehicles for traveling to the deepest parts of the ocean and to other planets. The high volume fraction of porosity in syntactic foams also enabled their applications in thermal insulation of pipelines in oil and gas industry. The possibility of tailoring the mechanical and thermal properties of syntactic foams through a combination of material selection, hollow particle volume fraction, and hollow particle wall thickness has helped in rapidly growing these applications. The low coefficient of thermal expansion and dimensional stability at high temperatures are now leading their use in electronic packaging, composite tooling, and thermoforming plug assists. Methods have been developed to tailor the mechanical and thermal properties of syntactic foams independent of each other over a wide range, which is a significant advantage over other traditional particulate and fibrous composites.

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Compressive Properties of Al-A206/SiC and Mg-AZ91/SiC Syntactic Foams

Gonzalo Alejandro Rocha Rivero, Benjamin Franklin Schultz, J.B. Ferguson, Nikhil Gupta and Pradeep Kumar Rohatgi (2013). Compressive properties of Al-A206/SiC and Mg-AZ91/SiC syntactic foams. Journal of Materials Research, 28, pp 2426-2435. doi:10.1557/jmr.2013.176.

Metal matrix syntactic foams are promising materials with high energy absorption capability. To study the effects of matrix strength on the quasistatic compressive properties of syntactic foams using SiC hollow particles as reinforcement, matrices of Al-A206 and Mg-AZ91 were used. Because Al-A206 is a heat-treatable alloy, matrix strength can be varied by heat treatment conditions, and foams in as-cast, T4, and T7 conditions were tested in this study. It is shown that the peak strength, plateau strength, and toughness of the foams increase with increasing yield strength of the matrix and that these foams show better performance than other foams on a specific property basis. High strain rate testing of the Mg-AZ91/SiC syntactic foams showed that there was little strain rate dependence of the peak stress under strain rates ranging from 10-3/s to 726/s.

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Reinforced Polymer Matrix Syntactic Foams - Effect of Nano and Micro-Scale Reinforcement, 2013, ISBN: 978-3-319-01242-1

Gupta, Nikhil, Pinisetty, Dinesh, Shunmugasamy, Vasanth Chakravarthy

Reinforced Syntactic Foams: Effect of Nano and Micro-Scale Reinforcement examines the fabrication processes, mechanism of reinforcement, and structure-property correlations of reinforced syntactic foams. The authors present the state of the art in this field, compare the properties of various types of syntactic foam systems comprising different matrix, hollow particle, and reinforcement materials. The book further identifies theories useful in predicting the properties of reinforced syntactic foams and conducting parametric studies to understand the possibility for tailoring their properties.

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Advanced Composite Materials for Automotive Applications: Structural Integrity and Crashworthiness, ISBN: 978-1-118-42386-8

Macke, A., Schultz, A., Rohatgi, P. K., and Gupta, N. Metal Matrix Composites for Automotive Applications. In Advanced Composite Materials for Automotive Applications: Structural Integrity and Crashworthiness, Editor: Elmarakbi, A. Wiley, 2013, in press.

Advanced Composite Materials for Automotive Applications: Structural Integrity and Crashworthiness provides a comprehensive explanation of how advanced composite materials, including FRPs, reinforced thermoplastics, carbon-based composites and many others are designed, manufactured and utilized in vehicle structural components where structural integrity and crashworthiness are key. This book includes technical explanation of composite materials in vehicle design and analysis and covers all phases of composites design, modeling, testing and failure analysis. It also explores the performance of existing materials including carbon composites and future developments in automotive material technology which work towards reducing the weight of the vehicle structure.

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Development of high performance lightweight aluminum alloy/SiC hollow sphere syntactic foams and compressive characterization at quasi-static and high strain rates

Dung D. Luong, Oliver M. Strbik III, Vincent H. Hammond, Nikhil Gupta, and Kyu Cho, Journal of Alloys and Compounds

Aluminum alloy A356 filled with silicon carbide hollow spheres (SiCHS) is investigated for quasi-static (10-3 s-1) and high strain rate (up to 1520 s-1) compressive properties. Such closed cell composite foams, called syntactic foams, are of interest in weight sensitive structural applications. The present work is focused on understanding the compressive failure mechanism and relating them with the material microstructure. The compressive and plateau strengths of syntactic foams with SiCHS are found to be 163 and 110 MPa, respectively. The measured properties are considerably higher than the existing fly ash cenosphere filled aluminum matrix syntactic foams. Compressive failure mechanisms are studied for A356/SiCHS syntactic foams and direct evidence of hollow sphere crushing at the end of the elastic regions is obtained. The predictions of compressive strength obtained from an existing model are validated with the experimental results. Extensive analysis of data on open and closed cell foams containing gas porosity and syntactic foams is presented. A clear advantage in terms of low density and high yield strength is observed in A356/SiCHS syntactic foams compared to other foams. Yield strength of aluminum foams may be different at high strain rate compression compared to quasi-static values but most of the foams do not show strong evidence of strain rate sensitivity within the high strain rate regime.

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Light Weight High Strength Hollow Silicon Carbide Shells for Ultra Deep Sea Vessels (poster presentation)

Oliver Strbik, Noel Tessier, Joe Cochran, Peter Marshall

Hollow sphere technology is a critical component of syntactic buoyancy foam for deep diving submersibles. Syntactic foam is a composite material combining prefabricated hollow spheres in a surrounding matrix.. Syntactic foam provides positive buoyancy to counterbalance the thick hull with associated battery, motor, fairings and other components. The weight and volume of the foam itself is an important consideration. To meet the demand for more efficient syntactic foam the density of the fixed buoyancy material needs to be the same or less than that presently in use while maintaining hydrostatic strength.. A survey of potential vendors showed that this would be nearly impossible without significant technical developments in the area of hollow sphere technology.

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Magnesium Matrix Composite Foams - Density, Mechanical Properties, and Applications

Gupta N., Luong D.D., Cho K. Metals. 2012; 2(3):238-252.

Abstract: Potential of widespread industrial applications of magnesium has been realized in recent years. A variety of magnesium alloy matrix composites are now being studied for mechanical properties. Since magnesium is the lightest structural metal, it can replace aluminum in existing applications for further weight savings. This review presents an overview of hollow particle filled magnesium matrix syntactic composite foams. Fly ash cenospheres are the most commonly used hollow particles for such applications. Fly ash cenospheres primarily have alumino-silicate composition and contain a large number of trace elements, which makes it challenging to study the interfacial reactions and microstructure in these composites. Microstructures of commonly studied AZ and ZC series magnesium alloys and their syntactic foams are discussed. Although only a few studies are available on these materials because of the nascent stage of this field, a comparison with similar aluminum matrix syntactic foams has provided insight into the properties and weight saving potential of magnesium matrix composites. Analysis shows that the magnesium matrix syntactic foams have higher yield strength at the same level of density compared to most other metal matrix syntactic foams. The comparison can guide future work and set goals that need to be achieved through materials selection and processing method development.

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Initial Characterization of an Aluminum Based Syntactic Foam

2011, Presented at TMS's 140th Annual Meeting and The Syntactic and Composite Foams III Conference

Authors: Oliver Strbik, Satyendra Kumar, Chris Smith, Todd Osborn, Joe Cochran, Thomas Sanders, Naresh Thadhani, Laura Cerully, Tammy McCoy, Liang Quan, Vincent Hammond, Kyu Cho. Speaker Todd Osborn

Continued progress in the development of metallic, high-strength, hollow shells has generated renewed interest in syntactic metal foams. These foams, when composed of hollow shells in a lightweight metallic matrix, possess low density, high specific stiffness, high strength to weight ratios, and greatly increased energy absorbing capabilities. As a result, they are of interest for applications ranging from ballistic armor to aircraft structures to automotive structural components and crumple-zones. Recently, a metallic foam composed of AA5083 filled with 60% (Vol) of M350 shells has been produced using conventional casting methods. Following fabrication, the foam microstructure was characterized using both optical and electron microscopy. Quasi-static compression and microhardness testing was performed to determine the change in properties resulting from the in corporation of the shells. Finally, limited ballistic testing has been performed to determine the ability of the foam to provide protection against low caliber threats.

ADVANCES IN BUOYANCY FOAM USING HOLLOW spheres

Vicki Kurtz, Oliver Strbik, Todd Osborn, Christopher Smith
2011, Presented at The Syntactic and Composite Foams III Conference

Hollow sphere technology is a critical component of syntactic buoyancy foam for deep diving submersibles. The weight and volume of the foam itself is an important consideration. The density of the fixed buoyancy material needs to be the same or less than that presently in use. None of the shells currently available provide a viable solution in the present state. Deep Springs Technology (DST) is producing silicon carbide shells in the desired size and density to replace the currently available foam. The foam will meet or exceed all critical requirements of buoyancy foam. These shells would be put in foam that will include a sphere with a target density between 0.25 – 0.30 g/cc with a 4500- 6000 psi hydrostatic strength. Ideally the shells would have an average diameter in the range of 100 – 160 microns. In addition, the cost of the new foam will be comparable to the currently available buoyancy foam. This paper will discuss the currently available bouncy foams, and their inability to meet th e current needs for deep diving submersibles. It will also discuss DST’s novel silicon carbide foam, made from its unique hollow shells. The properties of the foam and its disruptive impact on the current buoyancy foam industry will be discussed.

NOVEL ARMOR COMPOSITE WITH HOLLOW SPHERES

Oliver Strbik, Victoria W. Kurtz, Todd Osborn, Chris Smith
2011, Presented at The Syntactic and Composite Foams III Conference

Continued progress in the development of metallic, high-strength, hollow spheres has generated renewed interest in syntactic metal foams. These foams, when composed of hollow spheres in a lightweight metallic matrix, possess low density, high specific stiffness, high strength to weight ratios, and greatly increased energy absorbing capabilities. As a result, they are of interest for applications ranging from ballistic armor to aircraft structures to automotive structural components and crumple-zones. Recently, a metallic foam composed of AA5083 filled with 60% (Vol) of M350 spheres has been produced using conventional casting methods. Following fabrication, the foam microstructure was characterized using both optical and electron microscopy. Quasi-static compression and microhardness testing was performed to determine the change in properties resulting from the incorporation of the spheres. Finally, limited ballistic testing has been performed to determine the ability of the foam to provide protection against low caliber threats.