Patent

Composite layer material for dampening external load, obtaining process, and uses thereof

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Abstract

The present disclosure relates to the customization of a composite layer material for absorbing or dissipating mechanical energy under impacts or vibrations. The composite layer material comprises at least a support layer of a resilient material, said support layer having recessed fluid-tight microchannels comprising a fluid, wherein the channel section and fluid viscosity is such to dampen the external load by the constricted fluid flow through said microchannels. Therefore, the present disclosure relates to a maximization of safety and/or comfort.

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Chapter
This chapter provides to the students an up-to-date overview of the current challenges in the numerical simulations of complex fluid-flows at microscale. At such reduced length scales, phenomena involving viscous forces, reactive flows and surface effects (electrokinetics, slip flows, capillarity, surface tension) may become more important, and eventually overcame the effects of other macro scale predominant forces, such as inertial or gravitational effects. Therefore, numerical methods to simulate complex fluid-flows at microscale need to account with this new forces interplay arrangement. This chapter includes detailed insights into the main differences between macro and micro numerical simulations, presented in a modular view, and containing the synopsis of the theoretical models, numerical methods and simulation tools.
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Preprint
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Rotational rheometers are extremely sensitive instruments that are able to provide very accurate measurements of low values of different material functions, such as viscosity and viscoelastic moduli, under certain ideal flow conditions. Nevertheless, they fail in providing reliable data for the viscosity when measured at short time scales due to either instrument or fluid inertia. In 1948, Bikerman [“A penetroviscometer for very viscous liquids,” J. Colloid Sci. 3, 75 (1948)] proposed the penetroviscometer device as an instrument to measure the viscosity of highly viscous (10²–10⁴ Pa · s) Newtonian fluids under steady shear conditions. In the penetroviscometer, the fluid sample undergoes a kind of flow, which is currently known as back extrusion flow, and it is nowadays used to characterize the rheological properties of foodstuff under steady flow conditions. In this study, we perform a parametric analysis (blockage ratio, initial position, velocity profile of the inner cylinder, and viscosity of Newtonian fluids) of the back extrusion flow to determine its potential to provide reliable viscosity measurements at short time scales. Three-dimensional numerical simulations including free surface effects and inertial terms allowed us to determine its limits of operation. We additionally provide an analytical expression to calculate the time-resolved viscosity, relating the force and velocity of the inner cylinder by means of a geometric factor.
Article
This work presents a simple model of the flow generated in microchannels when the upper lid has a vertical deformation that depends on time and space. This model is able to capture the dynamics of the flow generated for two fundamental cases: full displacement of the upper lid and the flow generated by an impactor. The results for these cases have been compared with full 3D simulations with a moving mesh and experiments providing very accurate results. Once the model is validated, it is used for the analysis of the effect of the different parameters that control the flow, and for providing general laws for the non-dimensional energy consumed up to a time t0 in which the microchannel reaches half of its initial height. Finally, it is demonstrated that the general laws obtained for the non-dimensional energy are fully independent of the closing laws used.
Book
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Book of Abstracts AUXDEFENSE2018 - 1st World Conference on Advanced Materials for Defense September 2018 Lisbon - Portugal
Presentation
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The processing of fabricated potato crisps is a delicate art that is heavily reliant on the functionality of the starch combined with potato flakes to make the dough. Starch selection impacts dough characteristics, such as stickiness, sheetability, and expandability, which in turn impacts the uniformity, pillowing nature, crispness, crunchiness, hardness, and breakdown rate of final crisps. Combining deep insights of physical behavior of starch and dough with descriptive profiling for the crisps, one can select the suitable starch with key attributes that may have the biggest influence on the quality of the final product. Rheology of starch at high solids is indicative of dough rheology. Moderately elastic doughs give good sheeting and high expansion. High expansion is correlated to crispy texture.
Chapter
Complex fluids are everywhere, literally, just need to look around you, or even closer, inside your own body. These fluids are named complex because when they flow, they do not hold a linear relationship between the rate of deformation and the stress tensors, and consequently the Newton’s law of viscosity is not suitable for them. In this chapter, the importance of the performing a rheological characterization and choosing the right constitutive model is highlighted, in particular when flowing at microscale, where the elastic behavior of these complex fluids is enhanced even at very small Reynolds numbers. Additionally, the potential of microfluidics as a platform for performing rheological characterizations is tackled.
Article
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The development of engineered systems for energy dissipation (or absorption) during impacts or vibrations is an increasing need in our society, mainly for human protection applications, but also for ensuring the right performance of different sort of devices, facilities or installations. In the last decade, new energy dissipating composites based on the use of certain complex fluids have flourished, due to their non-linear relationship between stress and strain depending on the flow/field configuration. This manuscript intends to review the different approaches reported in the literature, analyses the fundamental physics behind them and assess their pros and cons from the perspective of their practical applications.
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