PAST RESEARCH PROJECTS
Fracture Characterization of Hard Biomineralized Tissues
Bone fracture is prevalent in developed countries with an estimate of two fracture events per individual over the course of their lifetime. The same is for osteoporosis–metabolic bone leading to increase leading to increased brittleness—which affect one in every two women and one in every five men over the age of fifty. The underlying scientific challenge is an in-depth understanding of the determinants of fracture resistance in cortical bone. Our research objective is to investigate fracture mechanisms in hard biomineralized tissues at the nanoscale.
- Amrita Kataruka, Kavya Mendu, Orieka Okeoghene, Jasmine Puthuvelil, Ange-Therese Akono, Microscopic assessment of bone toughness using scratch tests, Bone Reports, Vol. 6, pp. 17-25, (2017)
- Ange Therese Akono, Fracture Resistance of Biological Tissues: A Theoretical and Experimental Study, 2nd Health Care Engineering Systems Symposiums, Champaign, Illinois. September 14th 2015.
- Ange-Therese Akono, From Butter to Bone Tissues: Assessing the Fracture Resistance via Scratch Testing, p. 96 . In: Proceedings of the 13th International Symposium on Multiscale, Multifunctional and Functionally Graded Materials [Blucher Material Science Proceedings, v.1, n.1. São Paulo: Blucher, 2014. ISSN 2358-9337.
Nanomechanics of Gas Shale
Gas shale is relevant in many energy-related applications such as hydraulic fracturing in unconventional reservoirs, nuclear waste storage, or carbon dioxide geological capture and sequestration. The challenge consists in relating the mechanical performance of organic-rich shale to the structure and composition at different length-scales. A hierarchical material, gas shale is extremely heterogeneous and strong controls are needed to offset the influence of extrinsic parameters on the resulting behavior. Our approach is focused on depth-sensing methods, advanced multi-scale modelling and advanced imaging.
- Ange-Therese Akono, Pooyan Kabir, Influence of Geochemistry on Toughening Behavior of Organic-Rich Shale, Acta Geotecnica, https://doi.org/10.1007/s11440-018-0715-9, (2018).
- Pooyan Kabir, Franz-Josef Ulm, Ange-Therese Akono, Rate-Independent Fracture Toughness of Grey and Black Kerogen-Rich Shales, Acta Geotecnica, doi:10.1007/s11440-017-0562-0, (2017).
- Ange-Therese Akono, Franz-Josef Ulm, Microscopic Toughness of Viscous Solids via Scratching: From Amorphous Polymers to Gas Shale, Journal of Nanomechanics and Micromechanics, Vol. 7, (2017).
- Ange-Therese Akono, Pooyan Kabir, Nano-scale characterization of organic-rich shale via indentation methods, New Frontiers in Oil and Gas Exploration, pp. 209-233, (2016).
- Ange-Therese Akono, Pooyan Kabir, Microscopic Characterization of Gas Shale via Scratch Testing, Mechanics Research Communications, Vol. 78, Part B, pp. 86-92, (2016).
Dynamic Scratch Resistance of Nano-engineered Concrete for Sustainable Applications in Railway and Civil Construction
Crumbed rubber concrete represents an alternative to recycle tire rubber waste, thereby alleviating pressure to landfill sites. In this project, crumbed-rubber concrete is considered to extend the lifetime of railway ties via reduced wear. Our goal is to understand the tribological behavior at the microscopic scale as a function of intrinsic and extrinsic parameters. The knowledge gained will boost the design of high-performance railroad materials.
Funding Source: Birmingham-Illinois BRIDGE.
Ange-Therese Akono, Jiaxin Chen, S. Kaewunruen, Friction and Fracture Characteristics of Engineered Crumb-Rubber Concrete at Microscopic Lengthscale, Journal of Construction and Building Materials, Vol. 30, pp. 735-745, (2018).
Multi-scale and Multi-Physics Modeling of Na-PS Geopolymer Cement Composites
Inorganic polysialates are novel lightweight ceramic-like materials that are twice stronger than cement with a carbon footprint five times smaller. Our research goal is to accelerate the discovery of enhanced-performance polysialate composites by simulating various alumino-silicate systems at extreme scales using a deterministic approach. The end goal is a set of optimized design parameters in a vast and complicated state space along with a first-principles understanding of inorganic polysialate composites.
Funding Source: National Center for Supercomputing Applications, Blue Waters.
Ductile-to-Brittle Transition In Scratch Testing
Scratch testing is a standard rock mechanics testing method with relevance in rock excavation, oilwell drilling, and unconventional resources extraction applications. By application of Bazant’s size effect law, we show that the ductile-to-brittle transition is governed by the depth at the microscopic scale and by the blade with and width-to-depth ratio at the macroscopic scale.
- Ange-Therese Akono, Letter to the Editor Reply to “Discussion on the Fracture mechanics interpretation of the scratch test by Akono et al.“, Engineering Fracture Mechanics, Vol. 178, pp. 14-21, (2017).
- Ange-Therese Akono, Energetic Size Effect Law at the Microscopic Scale: Application to Progressive-load Scratch Testing, ASCE’s Journal of Nanomechanics and Micromechanics, Vol. 6, (2016).
- Ange-Therese Akono, Gregory A. Bouche, Rebuttal: shallow and deep scratch tests as powerful alternatives to asses the fracture properties of quasi-brittle materials, Engineering Fracture Mechanics, Vol. 158, pp. 23-38, (2016).
- A.-T. Akono, F.-J. Ulm, Z. P. Bazant, Discussion: Strength-to-fracture scaling in scratching, Engineering Fracture Mechanics, Vol. 119, pp. 21 (2014).
Scratch Test as a Fracture Process
The scratch test consists in pushing a hard probe across the surface of a softer material. Dating pack to the pre-Hellenic area and the Mohs scale, the scratch test is one of the oldest mechanics-of-materials tests; however, the underlying mechanics are not fully understood. The research objective is to formulate a fracture mechanics model to correlate the forces and depth measurements during scratch testing to intrinsic material fracture characteristics.
Funding Source: MIT Energy Material Initiative, Schlumberger, Shell, Total
- Ange-Therese Akono, Franz-Josef Ulm, Scratch test model for the determination of fracture toughness, Engineering Fracture Mechanics, Vol. 78, pp. 334-342, (2011).
- Ange-Therese Akono, Franz-Josef Ulm, An improved technique for characterizing the fracture toughness via scratch test experiments, Wear, Vol. 313, pp. 117-124, (2014).
- Ange-Therese Akono, Franz-Josef Ulm, Rate-dependent toughness in soft materials via microscopic scratch testing. In A. Bajaj, P. Zavattieri, M. Koslowski, & T. Siegmund (Eds.). Proceedings of the Society of Engineering Science 51st Annual Technical Meeting, October 1-3, 2014, West Lafayette: Purdue University Libraries Scholarly Publishing Services, (2014).
- Ange-Therese Akono, Franz-Josef Ulm, Fracture scaling relations of axisymmetric shape, Journal of the Mechanics and Physics of Solids, Vol. 60, pages 379-390, (2012).
- Akono, Ange-Therese; Reis, Pedro Miguel; Randall, Nicholas Xavier; Ulm, Franz-Josef, Scratch test as a fracture process: from soft to hard materials, American Physical Society, APS March Meeting 2012 Proceedings, February 27-March 2, (2012).
- Ange-Therese Akono, Nicholas X. Randall, Franz-Josef Ulm, Experimental determination of the fracture toughness via micro scratch tests: application to polymers, ceramics and metals, Journal of Materials Research, Vol. 27, pp. 485-493, (2012).
- Ange-Therese Akono, Pedro Miguel Reis and Franz-Josef Ulm, Scratching as a Fracture Process: From Butter to Steel, Physical Review Letters, Vol.106, pp. 204302, (2011).