Hierarchical Multiscale Models of Nanotubes Strengthening and Toughening of Ceramic Matrix Composites

Pavia, Fabio

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Year:: 2013
Contributor:: Pavia, Fabio (creator); Curtin, William (Director); Blume, Janet (Reader); Sheldon, Brian (Reader); Brown University. ENGINEERING: Solid Mechanics (sponsor)
Genre:: theses
Subject:: Ceramic Matrix Composites; Fracture; Interface Properties; Carbon nanotubes; Molecular dynamics; Ceramic-matrix composites
Extent:: xvii, 120 p.
DOI: https://doi.org/10.7301/Z0DN43C1

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Abstract:: Carbon nanotubes (CNTs) have the potential to introduce significant improvements in fracture strength and toughness of ceramic materials when compared to traditional microscale reinforcements. Ceramic matrix composites (CMCs) with CNTs are attractive as coatings and structural components in sectors where strong materials with low-weight and resistant to elevated temperature are needed. We develop atomistic simulations to characterize the mechanical behavior of the interface between a diamond matrix and an embedded nanotube, and we extend our analysis to the microscale by applying the properties obtained at a molecular level in shear-lag models of realistic nanoceramic composites. We capture bonding between a diamond matrix and a carbon nanotube by considering interstitial carbon atoms located at the interface, with a frictional force generated by the energy dissipated during breaking and reforming of bonds involving the interstitials. Using atomistic models of diamond nanocomposites, we find that, even for very strong interfaces coupling nanotube and matrix, an incident crack does not immediately penetrate into the nanotube but does induce shear distortions in the interstitial/matrix or interstitial/CNT bonds until the tube fractures from a critical small-scale defect nucleated near the matrix crack faces. At high density of interstitials the nanotube does not debond from the matrix and the composite behaves as a brittle ceramics, thus, a balance of toughness and strength must be tailored. The analytic models studying the optimization of realistic nanocomposites show that the control of interstitial carbon density and nanotube functionalization through material processing, for instance chemistry and atmosphere control during CVD deposition of the diamond matrix, along with tailoring of the nanotube morphology (interwall coupling, diameter, wall thickness, waviness), could permit the engineering of materials having high hardness and damage tolerance at submicron scales.
Notes:: Thesis (Ph.D. -- Brown University (2013)

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Rights: In Copyright
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Citation

Pavia, Fabio, "Hierarchical Multiscale Models of Nanotubes Strengthening and Toughening of Ceramic Matrix Composites" (2013). Mechanics of Solids Theses and Dissertations. Brown Digital Repository. Brown University Library. https://doi.org/10.7301/Z0DN43C1

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Mechanics of Solids Theses and Dissertations

Theses and Dissertations for the Mechanics of Solids department.
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