Ceramic Matrix Composites: On-Demand Oral Presentations
Sponsored by: ACerS Engineering Ceramics Division
Program Organizers: Narottam Bansal, NASA Glenn Research Center; Jacques Lamon, CNRS; Sung Choi, Naval Air Systems Command
Friday 8:00 AM
October 22, 2021
Room: On-Demand Room 4
Location: MS&T On Demand
Invited
Subcritical Crack Growth during Static Fatigue of Hi-Nicalon-S SiC Fiber: Randall Hay1; Marina Ruggles-Wrenn2; 1U.S. Air Force Research Laboratory; 2Air Force Institute of Technology
Three subcritical crack growth (SCG) laws were used to model sequential filament failure and ultimately tow failure during static fatigue of Hi-NicalonTM-S SiC fiber tows in air and steam. Model parameters were updated to fit tow failure times and steady-state strain rates for brittle creep previously measured at 700 to 1100°C to new data at 500 and 600°C under initial applied stresses up to 1350 MPa. The stress increase on intact filaments as others fractured and as filaments oxidized, and the increase in stress intensity geometric factors as crack size increased were incorporated in the models. The stress dependence of SCG rates and activation energies are determined. The fits to data for different models and model validity are discussed. The change in filament strength distributions after SCG are determined, possible effects of residual stress are calculated, and SCG mechanisms are discussed.
Invited
Static Fatigue of Hi-Nicalon-S Fiber Tows at Elevated Temperature in Air and in Steam: Scott Robertson1; Marina Ruggles-Wrenn1; Randall Hay2; Theodore Shillig1; Ronald Mitchell1; Brian Kroeger1; Logan Gumucio1; 1Air Force Institute of Technology; 2AFRL
A facility for testing SiC fiber tows in static fatigue at elevated temperatures in air, in steam and in steam saturated with silicic acid was developed. Static fatigue of Hi-Nicalon™-S fibers was investigated at 800-1100°C at stresses of 115-1250 MPa in air, in steam, and in steam saturated with silicic acid. Fibers tested in silicic acid-saturated steam and in air had silica scales throughout the test sections, but those tested in unsaturated steam did not develop scales near the steam injection point. The presence of steam reduced fiber lifetimes under static fatigue. Fiber lifetimes were much shorter in unsaturated steam than in Si(OH)4(g)-saturated steam. Failure strains did not exceed 0.3%. Steady–state strain rates and static fatigue lifetimes are modelled empirically by the Monkman–Grant relationship. The MG relationship was demonstrated to successfully predict creep lifetimes in air, steam and steam saturated with silicic acid. Failure mechanisms are discussed.
Tribological Performance of HfB2-ZrB2 Based Ultra High Temperature Ceramics Consolidated via Spark Plasma Sintering: Shruti Dubey1; Kantesh Balani1; Ambreen Nisar2; Shikha Awasthi3; 1Indian Institute of Technology; 2Florida International University; 3Indian Institute of Science Bangalore
HfB2-ZrB2 based ultra-high temperature ceramics (UHTCs) are used as protecting tiles for leading edges and nose cones of aerospace and hypersonic vehicles to sustain harsh environmental conditions.In the present work, the effect of SiC (20 vol %) and CNTs (6 vol %) incorporation on the wear behaviour of these ceramics consolidated via spark plasma sintering (SPS) is studied. It has been observed that the wear rate reduced by almost > 90%, when CNT and SiC reinforced in HfB2-ZrB2 composites (for both fretting and scratch tests).The implementation of tribological models shows the effect of normal load on the wear of HfB2-ZrB2 based UHTC. Hertzian contact pressure (~15 GPa and ~21 GPa for fretting as well as scratch, respectively) and scratch hardness (~27 GPa to ~46 GPa) increased for CNT reinforced sample.Thus, CNT with SiC added composite endorsed improved tribological performance and can be established as a damage-tolerant material for aerospace applications.
The Effect of Nanosized Additives on the Properties of Silicon Carbide-based Materials: Ihor Hnylytsia; 1
The formation of samples of SiC fraction 30-40 μm was performed with the addition of 12% oil coke and nanopowders SiC, Cr2C3 with a specific surface area of ~ 40 m2/g in an amount of 1% to 8%. Sintering of the formed samples was performed in vacuum at 2000-2100 0C for 30 minutes. The density without nanosized additives was obtained at the level of 3.04-3.06 g/cm3. For samples with SiC nanoadditives density at the level of 2.5-2.6 g/cm3 was obtained at a content of 4-5% nanopowders and an increase of almost 3.1 g/cm3 at a content of 7% additives. For samples with Cr2C3, first at 2-3% of the additive there is an increase in density, followed by a decrease in density with a local peak at 7%. A significant decrease in the electrical resistance of SiC - Cr2C3 samples at a content of 3% Cr2C3 nanopowder was found.
Developmental Efforts on Alternative Building Material using Kaolin-based Geopolymer from Local Sources in Nigeria: Oluwafemi Adelabu1; Oluwagbenga Odewole2; Augustine Nsah2; Tolulope Akinbogun2; 1University of Johannesburg; 2Federal University of Technology, Akure
Lack of access to sustainable and affordable housing is becoming a serious concern, especially in developing nations such as Nigeria. While the production of Portland cement contributes largely to CO2 emission, the development of geopolymers as a viable alternative building material is gaining more attention globally. However, research efforts on geopolymer in Nigeria are still at the budding stage, where most of the studies have focused on establishing the potentialities of the locally available pozzolanic materials. Findings have shown that Nigeria has abundant kaolin-rich minerals which are still underutilized. This paper examines most research efforts that have been made on the development of geopolymer binders using locally available kaolin minerals in Nigeria. It also presents an ongoing research exploring ways of applying kaolin-based geopolymer for building and construction purposes. This would advance practical solutions for affordable and eco-friendly building in the country, as seen in other parts of the world.