Description
- Abstract:
- Despite being composed of weak and brittle constituents, some structural biological materials, such as shell and bone, have relatively high strength and toughness. These materials are often heterogeneous and consist of a ceramic and an organic phase arranged in intricate patterns. One goal of bio-inspired engineering is to understand how the arrangement of these phases, known as the material's architecture, can impart such remarkable strength and toughness enhancements. Establishing connections between architecture and mechanical properties can provide both a deeper understanding of a material's bio-mechanical function(s) and help to uncover new mechanical design principles that can be used to improve engineering composites. The first step in this type of investigation is quantifying the mechanical property enhancements provided by a material's specific architecture. The skeletal fibers of the marine sponge Euplectella aspergillum are an example of a biological material for which the toughness and strength enhancements provided by the architecture have not yet been quantified. These fibers---known as spicules---have an architecture that consists of a solid silica cylinder surrounded by concentric cylindrical silica layers that look like tree rings. I measured the spicule's bending failure strains, fracture initiation toughness, and average crack growth resistance via three-point bending tests that I performed using a custom-built mechanical testing device. I then compared the properties of the E. aspergillum spicules to those of spicules from a related sponge---Tethya aurantia---that have a similar chemical composition but lack the lamellar architecture. Through this comparison I found that the toughness enhancements provided by the spicule's architecture pale in comparison to those observed in other biological materials with similar lamellar architectures, like shell and bone. On the other hand the spicule's architecture enhances its bending failure strain by a factor of 2.4. This work suggests that flexibility or strain tolerance may be more beneficial to the mechanical function of E. aspergillum spicules than toughness.
- Notes:
- Thesis (Ph. D.)--Brown University, 2018
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Citation
Monn, Michael Alexander,
"Insights into the Mechanical Functions of Glass Sponge Spicules Through a Characterization of Their Strength and Toughness Properties"
(2018).
Mechanics of Solids Theses and Dissertations.
Brown Digital Repository. Brown University Library.
https://doi.org/10.26300/v1s9-9143
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Mechanics of Solids Theses and Dissertations
Theses and Dissertations for the Mechanics of Solids department....