Professor K. K. Chawla Honorary Symposium on Fibers, Foams and Composites: Science and Engineering: Metal Matrix Composites/Ceramic Matrix Composites II
Program Organizers: Nikhilesh Chawla, Arizona State University; Aldo Boccaccini, University of Erlangen-Nuremberg; Gary Gladysz, Trelleborg USA; Pedro D. Portella, Federal Institute of Testing and Materials BAM
Thursday 8:00 AM
October 20, 2011
Room: D234
Location: Greater Columbus Convention Center
Session Chair: Nik Chawla, Arizona State University; Burton Patterson, University of Florida
8:00 AM Invited
Double Cemented Carbide-Dual Composite: Burton Patterson1; Xin Deng2; Zak Fang3; 1University of Florida; 2Smith International; 3University of Utah
Double Cemented Carbide (DCC) is a novel dual composite composed of spherical reinforcement granules of conventional cemented carbide (WC+Co) in a metal matrix. DCC provides a flexible means for obtaining unique combinations of properties, such as for wear resistant materials that must also have good fracture toughness. Compared with conventional cemented carbide, DCC has higher toughness for similar wear resistance and vice versa. The key to obtaining these combinations of properties is the independent control of the properties and volume fractions of the granule and matrix components. Granule properties have been varied via Co content in the cemented carbide granules. This presentation will describe the effects of these variables on the resulting microstructural state and mechanical properties of double cemented carbide.
8:40 AM
Determination of Residual Stress in Functionally Graded WC-Co Cements: Leila Tahvilian1; Zhigang Zak Fang1; K. S. Ravi Chandran1; 1University of Utah
Functionally graded materials (FGMs) have continuous gradients in mechanical properties, which lead to large thermal residual stresses during manufacturing. Measuring the residual stress in FGMs is a very challenging problem because the FGM is an inhomogeneous elastic solid. In this study, residual stresses in functionally graded cemented tungsten carbide (FG WC-Co) have been investigated using a combination of analytical and experimental approaches. The analytical method consisted of modeling the residual stresses as a function of the gradient of elastic modulus leading to an analytical expression relating residual stresses to the depth gradient. The experimental approach consisted of measuring the changes in back face strain upon removal of layer of certain thickness on one side. The analytical and experimental results have been assessed in light of the finite element analysis results.
9:00 AM
Hollow Sphere Reinforced Magnesium Alloy Matrix Composites
: John DeFouw1; Ben Schultz2; Nikhil Gupta3; Dung Luong3; Pradeep Rohatgi2; 1The Ohio State University; 2University of Wisconsin - Milwaukee; 3Polytechnic Institute of New York University - Brooklyn
Low density metal matrix composites have been synthesized by reinforcing magnesium with hollow spheres of carbon, steel, alumina and flyash using melt processing techniques. Synthesis methods used for the production of high volume fraction hollow sphere reinforced composites include pressure infiltration and stir mixing/separation. Resulting densities of the composites vary from 0.7 to 1.8 g/cc based on matrix and hollow sphere type, applied infiltration pressure, and volume fraction. Materials were characterized under mechanical compression using quasi-static and high strain rate deformation with split-hopkinson pressure bar and the results on plastic stress, plateau strength, and specific energy absorption will be presented. The results show the possibility of synthesizing low density composites with high energy absorption and tailored properties.
9:20 AM
Microstructural and Mechanical Behavior of Al-Mg-Si Alloy Composite Reinforced with Carbon Nanotubes: Katsuyoshi Kondoh1; Hiroyuki Fukuda1; Junko Umeda1; Bunshi Fugetsu2; 1Osaka University; 2Hokkaido University
Microstructural and mechanical behavior of Al-Mg-Si alloy composite reinforced with multi-wall carbon nanotubes (CNTs) were evaluated with optical and scanning electron microscopy, tensile test and Vickers hardness test. The composite alloy obviously indicated higher mechanical strength than the pristine Al-Mg-Si alloy before the aging treatment. The aged composite showed lower mechanical performance, and the aging treatment was not effective to strengthen the composite reinforced with CNTs. This was because Mg elements around CNTs were consumed to form Al-Mg-C compounds, and resulted in the incomplete matrix strengthening effect after the aging.
9:40 AM Break
10:00 AM
Compression-Compression Fatigue Investigation of a Pd43Ni10CU27P20 Metallic-Glass Foam: Gongyao Wang1; M. Demetriou1; J. Schramm1; Peter Liaw1; W Johnson1; 1Univ of Tennessee
Compression-compression fatigue studies of a metallic-glass foam have been conducted. A stress-life curve is established, which exhibits an endurance limit at a fatigue ratio of about 0.1. The origin of fatigue resistance of this foam material was found to be the tendency of intracellular struts to undergo elastic and reversible buckling, while the fatigue process advanced by anelastic strut buckling, resulting in localized plasticity (shear banding) and ultimate strut fracture. Plots of peak and valley strains versus number of fatigue cycles coupled with curves of hysteresis loops and estimates of energy dissipation at different loading cycles verify the four stages of foam-fatigue characteristics. Acknowledgements: G.Y. and P.K.L. are supported by the National Science Foundation programs (DMR-0231320, DMR-0909037, and CMMI-0900271) with Drs. C. Huber, D. Finotello, C. V. Cooper, and A Ardell as program directors.
10:20 AM Invited
High Temperature Stable Geopolymer Composites: Waltraud Kriven1; Timothy Dietz1; 1University of Illinois at Urbana-Champaign
High temperature, castable materials are desired for numerous applications. Presented is an experimental investigation of geopolymers to be used up to 1500C to satisfy this need. Geopolymers were synthesized with a composition based on the activation of metakaolin with an alkali hydroxide solution containing cesium plus refractory fibers for reinforcement. The reinforcement was high alumina content (95%) fiber from SaffilŽ with a melting temperature of >2000C. The flexural strength of the samples were determined at room temperature in a 4-point bend configuration for samples that were cast and fired at temperatures up to 1500C as well as samples that were tested at their respective firing temperatures. Generally the strength of heated samples improved over unheated samples and the strength of both heated and unheated samples was on par with that of unheated high strength concrete. The reinforcement also protected the samples from cracking during dehydration and from disintegration when wet.
11:00 AM Invited
Implementation Challenges for Sintered Silicon Carbide Fiber Bonded Ceramic Materials for High Temperature Applications
: Mrityunjay Singh1; 1Ohio Aerospace Institute, NASA Glenn Research Center
During the last decades, a number of fiber reinforced ceramic composites have been developed and tested for various aerospace and ground based applications. However, a number of challenges still remain slowing the wide scale implementation of these materials. In addition to continuous fiber reinforced composites, other innovative materials have been developed including the fibrous monoliths and sintered fiber bonded ceramics. The sintered silicon carbide fiber bonded ceramics have been fabricated by the hot pressing and sintering of silicon carbide fibers. However, in this system reliable property database as well as various issues related to thermomechanical performance, integration and fabrication of large and complex shape components has yet to be addressed. In this presentation, thermomechanical properties of sintered silicon carbide fiber bonded ceramics (as fabricated and joined) will be presented. In addition, critical need for manufacturing and integration technologies in successful implementation of these materials will be discussed.
11:40 AM
Effect of Age-Hardening on Dry Sliding Wear Behaviour of Mushy State Rolled
In-Situ Al-4.5Cu-5TiB2 Composite
: Krishnan Pavitra1; Rahul Mitra1; 1Indian Institute of Technology
Dry sliding wear behavior of rolling surfaces of cast in-situ Al-4.5Cu-5TiB2 composite samples subjected to two mushy state roll passes at the temperature for 20 volume percent liquid after prior hot rolling has been investigated in their solution-treated or age-hardened conditions. These samples having taken only 2 h for peak-aging, have shown higher wear resistance compared to that of composites with matrices in underaged, overaged or solution-treated condition. The surface roughness measured by stylus profilometer has been found to increase with wear rate, which in turn increases with decrease in hardness. The wear mechanisms have been studied further through careful examination of both worn surfaces and wear debris by scanning electron microscopy. Examination of the sample cross-sections just beneath the worn surfaces has shown the presence of elongated and fine grains, confirming extensive sub-surface deformation. Residual stress measured using X-ray diffraction has been found to vary with extent of age-hardening.