Ioanna Tsimouri

Last Name

Tsimouri

First Name

Ioanna

ORCID

0000-0002-2623-1742

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Publications 1 - 6 of 6

Stiff, Damping, and Lightweight Laminated Composites with Submicron Comb-Polymer Viscoelastic Interlayers
Tsimouri, Ioanna (2023)
A constitutive hemorheological model addressing the deformability of red blood cells in Ringer solutions
Stephanou, Pavlos S.; Tsimouri, Ioanna (2020)
Soft Matter
Red blood cells (RBCs) can deform substantially, a feature that allows them to pass through capillaries that are narrower than the largest dimension of an undeformed RBC. Clearly, to understand how they transport through our microcirculation, we need a constitutive model able of accurately predicting the deformability of RBCs, which seems currently unavailable. To address this void, we herein propose a new model that accounts for the deformability of RBCs by modeling them as deformed droplets with a constant volume. To make sure the model is by construction thermodynamically admissible we employ non-equilibrium thermodynamics as our tool. Since RBCs are merely droplets with the inner fluid exhibiting a higher viscosity than that of the outer one, RBCs are described by a conformation tensor constrained to have a constant determinant (volume). The model predicts the second normal stress coefficient in steady-state simple shear flow to first shear thicken and then shear thin, which is an unexpected behavior; however, we cannot judge whether such a prediction is aphysical or not due to unavailable experimental rheological data in the literature. We show that the new model is capable of addressing the deformability of isolated (very low hematocrit) RBCs in simple shear and the shear viscosity of non-aggregating blood. As derived the model addresses only non-aggregating blood, but can very easily be generalized to account for aggregating blood. © 2020 The Royal Society of Chemistry.
Lightweight silicon and glass composites with submicron viscoelastic interlayers and unconventional combinations of stiffness and damping
Tsimouri, Ioanna; Caseri, Walter; Hine, Peter J.; et al. (2024)
Composites Part B: Engineering
The necessity of stiff structural materials with advanced damping characteristics has arisen naturally along with the technological evolution. However, despite ever-growing demand, the achievement of stiff materials with high damping factor remains challenging because of the antagonistic nature of the two properties. Here, this challenge is accomplished by exploiting the non-affine deformation of laminated composites paired with the dissipative nature of the viscoelastic phase. Guided by a finite element design analysis, composites with flat submillimeter stiff layers and submicron viscoelastic interlayers are fabricated. The viscoelastic component consists of a prudently chemically architectured comb-like polydimethylsiloxane (PDMS) elastomer that properly adheres to the stiff silicon or glass layers, strong enough to withstand repeated dynamic cycles. The composites are fabricated using an unconventional but simple stacking route based on the diffusion of a platinum catalyst precursor into a reactive solvent-free PDMS melt. The fabricated composites, Si/PDMS and glass/PDMS, exhibit an elastic modulus higher than common monolithic glass, they are as light as glass but have about four orders of magnitude higher loss factor. The composites markedly outperform numerous customary materials, they escape the Ashby limit for mechanical damping – stiffness trade-off, and their exceptional combinations of properties are maintained over a broad range of temperatures and frequencies.
Correction: A constitutive hemorheological model addressing the deformability of red blood cells in Ringer solutions
Stephanou, Pavlos S.; Tsimouri, Ioanna (2022)
Soft Matter
A simulation-driven design approach to the manufacturing of stiff composites with high viscoelastic damping
Tsimouri, Ioanna; Montibeller, Samuel; Kern, Leyla; et al. (2021)
Composites Science and Technology
Materials with enhanced vibration damping properties are of ever-growing technological interest. The ability of a material to limit mechanical vibrations, indeed, not only may extend its service life, but also reduces its susceptibility to mechanical noise generation. The selection and design of damping structural materials usually aims to maximize the loss coefficient, while sacrificing the stiffness, to achieve the proper vibration damping capability. In this work, we overcome this typical stiffness tradeoff by geometrically confining thin viscoelastic layers between stiff thicker ones in a layered composite, thus enhancing its viscoelastic shear response. The preparation of the composite is guided by a simple design methodology based on the effective properties of its homogenized counterpart. An optimal design window, defined for the viscoelastic volume fraction, directs the manufacturing of the composite. This approach allows to manufacture composites that exhibit enhanced damping properties, with over three orders of magnitude increase of loss coefficient and less than one order of magnitude decrease of stiffness compared to the constituent stiff material. Such materials might find applications in fields where high stiffness is required but a damping component is necessary to avoid the build-up of dangerous vibrational modes: from the aerospace industry to the design of “silent” infrastructures.
A Comparison between Predictions of the Miller–Macosko Theory, Estimates from Molecular Dynamics Simulations, and Long-Standing Experimental Data of the Shear Modulus of End-Linked Polymer Networks
Tsimouri, Ioanna; Schwarz, Fabian; Bernhard, Tim; et al. (2024)
Macromolecules
Long-standing experimental data on the elastic modulus of end-linked poly(dimethylsiloxane) (PDMS) networks are employed to corroborate the validity of the Miller-Macosko theory (MMT). The validity of MMT is also confirmed by molecular dynamics (MD) simulations that mimic the experimentally realized networks. It becomes apparent that for a network formed from bulk, where the fractions of the loops are small, it is sufficient to account for the topological details of a reference tree-like network, i.e., for its degree of completion, junction functionalities, and trapped entanglements, in order to practically predict the modulus. However, a mismatch is identified between the MMT and MD simulations in relating the fraction of the soluble material to the extent of reaction. A large contribution of entanglements to the modulus of PDMS networks prepared with short precursor chains is presented, suggesting that the elastic modulus of commonly used end-linked PDMS networks is in fact entanglement-dominated.

Publications 1 - 6 of 6

Ioanna Tsimouri

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