| NSF Org: |
CMMI Division of Civil, Mechanical, and Manufacturing Innovation |
| Recipient: |
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| Initial Amendment Date: | May 5, 2020 |
| Latest Amendment Date: | May 5, 2020 |
| Award Number: | 2029860 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Lucy Zhang
CMMI Division of Civil, Mechanical, and Manufacturing Innovation ENG Directorate for Engineering |
| Start Date: | January 1, 2020 |
| End Date: | August 31, 2021 (Estimated) |
| Total Intended Award Amount: | $54,002.00 |
| Total Awarded Amount to Date: | $54,002.00 |
| Funds Obligated to Date: |
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| Recipient Sponsored Research Office: |
874 TRADITIONS WAY TALLAHASSEE FL US 32306-0001 (850)644-5260 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
2525 Pottsdamer Street Tallahassee FL US 32310-6046 |
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Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| NSF Program(s): | BMMB-Biomech & Mechanobiology |
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| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.041 |
ABSTRACT
Fracture and wear are common issues in engineering - to the extent that the terms "worn," "fractured," and "broken" are generally synonymous with the end-of-utility of devices. In many cases, traditional materials fail to meet the complex, simultaneous performance requirements that would be ideal for next generation engineering systems. The enamel of the teeth of grazing animals represents one of nature's most remarkable biological materials -- a ceramic-like composite showing exceptional strength, toughness, wear-resistance, and ability to slow crack propagation. This is an important set of properties for a structure that is key to long-term survival in these animals - as functional teeth are required for feeding. This EArly-Concept Grant for Exploratory Research (EAGER) project will study these damage-tolerant biomaterials using a combination of evolutionary biology, biomechanics, and materials science. Results and methods from this research will be of considerable interest to investigators in many disciplines, including engineering, materials science, evolutionary biology, ecology, comparative anatomy, mammalogy, and paleontology. The research will also support the development of novel, sustainable materials with improved wear and fracture behavior. Graduate students will be involved in this truly interdisciplinary project and learn how the various fields can work together to tackle challenging questions. This research will also introduce a more effective, evolutionary approach for exploring nature for biomimetic examples.
The goal of this interdisciplinary research is to specifically understand the biomechanical form, function and performance of enamel lattices, known as Modified Radial Enamel (MRE), in the grinding teeth of large herbivorous mammals. Samples will be obtained from numerous species, including equines (horses), bovids (e.g. bison and cattle) and suids (e.g. warthogs). This study will specifically focus on how these animals' teeth endure tens to hundreds of millions of high stress contact loading cycles and impacts while chewing tough and abrasive plant matter, such as grasses whose roots are laden with hard, fracture-promoting sediment inclusions. The underlying hypothesis is that MRE is an evolutionarily optimized compromise for: 1) incredible fracture resistance due to prism arrangements that localize damage and strategically control crack direction; 2) unexpected strength and toughness made possible by compliant proteinaceous prism sheaths that circumvent hydroxyapatite's inherent brittleness; and 3) wear resistance conveyed through hard, hyper-mineralized, oriented enamel prisms. The project will investigate this hypothesis through two objectives. First, the study will use an evolutionary biology approach to identify the ancestral enamel fabric character states to MRE that independently evolved in horses, bovids and warthogs. From this information, it will be possible to readily identify the specific evolutionary modifications to the enamel fabrics that enabled grinding and identify living species that can be used to undertake comparative biomechanical assessment. Second, the project will investigate the structure-property relationships of the enamel across multiple length scales by comprehensively characterizing the material properties using micro-and nano-mechanical tools, spectroscopy, and advanced electron microscopy. Teeth of grinding species with MRE will be compared with close relatives that retain the ancestral enamel fabrics, thereby revealing the salient anatomical changes that enabled the optimized combination of biomechanical properties.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
PROJECT OUTCOMES REPORT
Disclaimer
This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
The objective of this NSF EAGER award was to understand the remarkable biomechanical properties of enamels in grinding dentitions of vertebrates. Our Intellectual Merit is rooted on how the multiscale structure and composition of enamel tissues contribute to damage tolerance.
The Major Findings of this study include:
1) Enamel of grazing vertebrates resist catastrophic fracture from impacts with harder inclusions, unexpected of a ceramic-like material. This is achieved by the tissue’s ability to:
- Strategically control crack directionality (aligning cracks to prevent crack merging and catastrophic damage).
- Form many smaller, parallel cracks to dissipate strain energy, facilitating fracture toughness.
- Introducing undulations to each crack, further dissipating strain energy.
2) These tissue’s ability to resist fracture is governed by their unique and multiscale microstructure/tissue architectures.
- In grazing mammals, modified radial enamel (MRE) consists of rows of enamel prisms (columns) separated by more-complaint interprismatic matrix (i.e. loosely organized hydroxy-apatite crystals and proteinaceous sheaths).
- In analogous hadrosaurid dentitions, the wavy enamel achieves the same crack-steering and toughening mechanisms using a different microstructure. This consists of undulating layers of compacted and loosely compacted aprismatic enamel with alternating mechanical properties. The alternating layers from stiff to compliant contribute to crack steering in the tissue. The undulations of the layers control the spacing and separation of parallel cracks.
3) The teeth of large grazing vertebrates, including horses, bison, elephants, mammoths and hadrosaur dinosaurs (a reptilian analog to mammalian grazers) are all self-regulated by wear. This is achieved by composite architectures where each tissue contributes different mechanical and wear properties that result in whole-tooth features to enable grinding of plant fodder.
The Broader Impacts of this research include:
1) We developed bio-inspired, damage tolerant materials composed of undulating, multilayer PVD metal/metal-nitride analogs to the wavy enamel. This new design paradigm for materials has possible applications in many industrial sectors, including aerospace, manufacturing tools and other applications where lightweight, damage-tolerant, and wear-resistant materials are needed.
2) A new approach towards sourcing bio-inspiration through the fossil record, was coined PIE (Phylogenetically Informed Engineering ), whereby the salient architectural attributes contributing to the unique biomechanical properties of can be more readily identified by comparing biomechicanical performance in related animals to those in those showing attributes of interest in evolutionary (genealogical) contexts .
3) Research opportunities and training of a diverse group of undergraduate and graduate students, including women and under-represented minorities. This includes cutting-edge techniques and interdisciplinary training in mechanical engineering, materials science, and biological sciences.
Last Modified: 01/20/2022
Modified by: Brandon A Krick
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