Suresh G Advani - Academia.edu (original) (raw)

Papers by Suresh G Advani

Integrating materials and manufacturing innovation, Mar 18, 2015

HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés. THE 14TH INTERNATIONAL CONFERENCE ON FLOW PROCESSING IN COMPOSITE MATERIALS

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Advanced Composites Letters, 2000

One-dimensional mould filling experiments were done in Land T-shaped moulds with constant flow ra... more One-dimensional mould filling experiments were done in Land T-shaped moulds with constant flow rate injection, and the pressure history was measured. Transient relationship between the preform permeability along the flow direction and the time derivative of pressure was used to measure the permeability. It was found that the resistance to flow around the bend increased by an order of magnitude within the boundary layer of the 90 o bend. A simple resistive model with three different permeabilities could be used to describe the decrease in the permeability around the bend using a corner model and hence one could predict the permeability in the bend region. While considering numerical simulations of complicated geometries with bends, one should account for the variation in the bend section to capture the physics of flow in such structures.

Entropy, Dec 24, 2019

Fiber-fiber interaction plays an important role in the evolution of fiber orientation in semi-con... more Fiber-fiber interaction plays an important role in the evolution of fiber orientation in semi-concentrated suspensions. Flow induced orientation in short-fiber reinforced composites determines the anisotropic properties of manufactured parts and consequently their performances. In the case of dilute suspensions, the orientation evolution can be accurately described by using the Jeffery model; however, as soon as the fiber concentration increases, fiber-fiber interactions cannot be ignored anymore and the final orientation state strongly depends on the modeling of those interactions. First modeling frameworks described these interactions from a diffusion mechanism; however, it was necessary to consider richer descriptions (anisotropic diffusion, etc.) to address experimental observations. Even if different proposals were considered, none of them seem general and accurate enough. In this paper we do not address a new proposal of a fiber interaction model, but a data-driven methodology able to enrich existing models from data, that in our case comes from a direct numerical simulation of well resolved microscopic physics.

International Journal of Material Forming, Jan 30, 2019

A numerical methodology is proposed to predict void content and evolution during autoclave proces... more A numerical methodology is proposed to predict void content and evolution during autoclave processing of thermoset prepregs. Starting with the initial prepreg void content, the void evolution model implements mechanisms for void compaction under the effect of the applied pressure, including Ideal Gas law compaction, and squeeze flow for single curvature geometries. Pressure variability in the prepreg stack due to interactions between applied autoclave pressure and anisotropic material response are considered and implemented. A parametric study is conducted to investigate the role of material anisotropy, initial void content, and applied autoclave pressure on void evolution during consolidation of prepregs on a tool with single curvatures. The ability of the model to predict pressure gradient through the thickness of the laminate and its impact on void evolution is discussed.

Journal of Rheology, 2019

A numerical study is presented for fiber suspension flows through a parallel plate channel and a ... more A numerical study is presented for fiber suspension flows through a parallel plate channel and a planar 4:1 contraction. Besides examining a Newtonian suspending fluid, a non-Newtonian matrix exhibiting a pseudoplastic behavior and describing a power-law model is also investigated. Furthermore, instead of using orientation tensors for the macroscopic constitutive modeling, the proposed approach addresses the macroscopic scale by describing the fiber orientation state with the probability distribution function (PDF). It enables us to eliminate the error introduced due to the closure approximation when using orientation tensor description as our numerical scheme solves the PDF in both the spatial and configurational spaces. This allows us to correctly implement expressions for both the fiber extra stress, especially for the suspending matrix displaying a pseudoplastic behavior, and the fiber orientation state, describing the configuration. Hence, these two constitutive relations for suspensions are used to perform simulations in which flow and fiber orientation are fully coupled. Results are presented in planar geometries involving channel and 4:1 contraction flows. It is found that the coupling effect flattens the velocity profile for both suspending fluids but has a small impact on the fiber orientation distributions at the geometry outlets. However, in the corner region where a vortex is observed, its magnitude increases with the coupling and this enhancement is more pronounced for the Newtonian suspending fluid. The Newtonian viscosity model is replaced with the Carreau model and results are compared to a bi-viscosity model. It gives qualitatively correct results if no rapid fiber orientation change occurs along the streamlines.

International Journal of Material Forming, 2019

In this work we develop a void filling and void motion dynamics model using volatile pressure and... more In this work we develop a void filling and void motion dynamics model using volatile pressure and squeeze flow during tape placement process. The void motion and filling are simulated using a non-local model where their presence is reflected in the global macroscale behavior. Local pressure gradients during compression do play a critical role in void dynamics, and hence the need for a non-local model. Deriving a non-local model accounting for all the void motion and dynamics entails a prohibitive number of degrees of freedom, leading to unrealistic computation times with classical solution techniques. Hence, Proper Generalized Decomposition-PGD-is used to solve the aforementioned model. In fact, PGD circumvents the curse of dimensionality by using separated representation of the space coordinates. For example, a 2D problem can be solved as a sequence of 1D problems to find the 2D solution. The non-local model solution sheds light on the fundamental of the void dynamics including their pressure variation, motion and closure mechanisms. Finally, a post treatment of the transient compression of the voids is used to derive conclusions regarding the physics of the void dynamics.

Advanced Composites Letters, 2003

To manufacture composite parts with the Resin Transfer Moulding process, a fluid resin is injecte... more To manufacture composite parts with the Resin Transfer Moulding process, a fluid resin is injected into a mould containing a fibrous preform. Often, due to variations in the preform structure, the flow behaviour can be drastically different from what was anticipated, which may not wet some of the fibrous regions causing dry spots. A common disturbance is race tracking, where the preform does not fit precisely along the mould edge. With the help of sensors, one can track the flow and measure the level of the disturbance in the mould. Decisions can be made on-line to redirect the flow to avoid dry spots. A methodology was developed to measure the level of the race tracking and implement control actions to compensate for that race tracking disturbance. Fully automated experiments were run several times. For each experiment, although the level of race tracking was unknown beforehand, the controller properly compensated for the race tracking to successfully complete the mould filling.

Integrating Materials and Manufacturing Innovation, 2015

The partial wetting of cylindrical surfaces is encountered in many industrial applications such a... more The partial wetting of cylindrical surfaces is encountered in many industrial applications such as composites manufacturing, MEMS, hair care products, and textile engineering. Understanding the impact of key parameters such as resin and fiber surface interaction properties and the geometric arrangement of the fibers on wetting would lead to tailoring a desired interface between the resin and the fiber surface. A three-dimensional model of resin wetting a single fiber is presented. This model is then extended to study a finite volume of resin wetting fibers in square and triangular packing arrangements. The impact of changing wetting properties and fiber volume fraction is examined for each packing arrangement.

Materials, 2003

Ceramic armors are known to provide excellent ballistic resistance, but the precise mechanisms of... more Ceramic armors are known to provide excellent ballistic resistance, but the precise mechanisms of projectile defeat in these systems are not fully understood. A critical stage in the penetration process is the flow of the pulverized ceramic past the projectile. To further understand this phenomenon, we are investigating the flow and energy dissipation of granular beds, specifically under conditions of high pressure. Two different viscometer systems are designed and fabricated to characterize the behavior of ceramic particles under shear stress and high pressures. The first system is a Couette flow device with ability to exert pressure on the particles during its rotation and measure the torque and angular velocity of the system. These data are used to extract viscosity and energy dissipation due to friction between particles as a function of the shear rate. The second system focuses on the movement of a cylinder through a bed of compacted ceramic particles. By measuring the force required to move the cylinder through the compacted bed, we can evaluate the effective resistance of the particle bed under various compaction pressures. By characterizing the friction coefficient, we obtain the apparent viscosity of the compacted granules under different pressure loads for low strain rates. This characterization should prove useful in understanding the shearing and dissipation mechanisms between granular particles under high pressures.

Composites Manufacturing, 1991

Physics of Fluids, 2010

A new finite-element scheme to solve the Stokes–Brinkman equation for flow analyses in dual scale... more A new finite-element scheme to solve the Stokes–Brinkman equation for flow analyses in dual scale porous media is presented and has been applied to predict the effective permeability of dual scale fibrous media. Both continuous and discontinuous stress conditions at the interface between a porous media and a surrounding fluid are explored by introducing an equivalent momentum equation for the Brinkman equation. The proposed scheme uses a uniform structured regular rectangular mesh to discretize the domain and employs the level-set method to describe the porous media allowing for inclusion of complex geometrical features easily. Biperiodic boundary conditions have been applied to conduct the flow analysis in a representative volume of mesoscale porous structures. Numerical solutions in a parallel channel flow over a porous media are presented and compared with analytic solutions to assess the accuracy of the proposed scheme. The scheme is then applied to flow past two regular periodi...

Physical Review E, 2005

The behavior of polydisperse granular materials, composed of mixtures of particles of different s... more The behavior of polydisperse granular materials, composed of mixtures of particles of different sizes, is studied under conditions of high pressure and confinement. Two types of experiments are performed. In the first type, granular mixtures are compressed, with the resulting force-displacement curve used to calculate density and volume modulus. In the second set of experiments, the drag force is measured by pulling a cylinder, horizontally, through a compressed granular mixture. The density, volume modulus, and drag forces for the mixtures are quantified in terms of the mixture composition. The results show that the behavior of these mixtures depends strongly on the mass fractions of the different sized particles, with density, volume modulus, and drag force all reaching values significantly higher than observed in the monodisperse granular materials. Furthermore, the trends for density and drag force show strong correlation, suggesting that drag resistance of confined granular media could be directly related to packing effects. These results should prove useful in understanding the physics of drag in granular materials under high pressure, such as ballistic penetration of soils or ceramic armors.

Physical Review E, 2004

The resistance offered by a cylindrical rod to creeping cross flow of granular materials under pr... more The resistance offered by a cylindrical rod to creeping cross flow of granular materials under pressure is investigated. The experimental system consists of a confined bed of granular particles, which are compacted under high pressure to consolidate the granular medium. A cylindrical rod is pulled at a constant and slow rate through the granular medium, and the measured pulling resistance is characterized as a drag force. The influence of various parameters such as the velocity of the cylindrical rod, the rod diameter and length, the granular particle size, and the compaction pressure on the required drag force is investigated experimentally. Nondimensional analysis is performed to simplify the relationships between these variables. The results show that the drag force is independent of the drag velocity, is linearly proportional to compaction pressure and rod diameter, and increases with rod length and particle size. Additional compaction experiments show that the effective density of the granular bed increases linearly with pressure, and similar behavior is noted for all particle sizes. These results should prove useful in the development of constitutive equations that can describe the motion of solid objects through compacted granular media under high pressure, such as during ballistic penetration of soils or ceramic armors.

Mechanics of Materials, 2009

Carbon Nanotube/High Density Polyethylene (CNT/HDPE) composites were manufactured and tested to d... more Carbon Nanotube/High Density Polyethylene (CNT/HDPE) composites were manufactured and tested to determine their wear behavior. The nanocomposites were made from untreated multi-walled carbon nanotubes and HDPE pellets. Thin films of the precursor materials were created with varying weight percentages of nanotubes (1%, 3%, and 5%), through a process of mixing and extruding. The precursor composites were then molded and machined to create test specimens for mechanical and wear tests. These included small punch testing to compare stiffness, maximum load and work-tofailure and block-on-ring testing to determine wear behavior. Each of the tests was conducted for the different weight percentages of composite as well as pure HDPE as the baseline. The measured mechanical properties and wear resistance of the composite materials increased with increasing nanotube content in the range studied.

Journal of Rheology, 1989

This work investigates the two-and three-dimensional description of fiber orientation in homogene... more This work investigates the two-and three-dimensional description of fiber orientation in homogeneous flow fields. Motion of the fibers is described using the Dinh-Armstrong model which was developed for semiconcentrated fiber suspensions. The calculation of rheological properties for fiber suspensions requires the determination of fourth-order moments of orientation distribution function which is defined as the fourth-order orientation tensor. Solution of the distribution function is obtamed in terms of the velocity gradients and transient calculations are presented for simple shear, planar elongational, and uniaxial extensional flows. Second-and fourth-order tensors are calculated by using the distribution function and the components of the second-order tensor are utilized to define an orientation ellipsoid for the graphical representation of the orientation state. The fourth-order tensor is approximated from second-order tensors through quadratic and hybrid closure equations, and compared with the exact results. Despite the qualitative agreement between the exact and approximated results, considerable quantitative discrepancy is observed which may result in inaccurate prediction of suspension behavior.

Journal of Rheology, 2007

Carbon nanotubes have exhibited unusually large changes in selective physical and mechanical prop... more Carbon nanotubes have exhibited unusually large changes in selective physical and mechanical properties when added to polymers or polymer composites in small quantities. To understand their rheological behavior and processibility, we mixed multiwalled carbon nanotubes (MWNT) in epoxy and created suspensions of different dispersion qualities, MWNT aspect ratios, concentrations, suspension network structures, and MWNT orientation states. Their rheological properties were measured with a cone and plate rheometer. It was found that as MWNT dispersion quality improved or their network connections, the aspect ratio or concentration increased, the MWNTs interactions became stronger as indicated by a higher storage modulus G′, complex viscosity ∣η*∣, and steady shear viscosity η. It was found that suspensions which contained a mixture of separated MWNT along with small MWNT aggregates exhibited G′ that was independent of frequency suggesting solidlike behavior. This frequency sweep method c...

Journal of Power Sources, 2006

Recent studies indicate that PEM fuel cell performance may be strongly influenced by in-plane per... more Recent studies indicate that PEM fuel cell performance may be strongly influenced by in-plane permeability of the gas diffusion layer (GDL). The current study employs a radial flow technique for obtaining in-plane permeability of GDLs, using either gas or liquid as the impregnating fluid. A model has been developed and experimentally verified to account for compressibility effects when permeability measurements are conducted using a gas. Permeability experiments are performed on samples of woven, non-woven, and carbon fiber-based GDL at various levels of compression using air as the impregnating fluid. Woven and non-woven samples are measured to have significantly higher in-plane permeability compared to carbon fiber paper at similar solid volume fractions.