Search

Microwave (MW) technology relies on volumetric heating. Thermal energy is transferred to the material that can absorb it at specific frequencies. The complex physics involved in this process is far from being understood and that is why a simulation tool has been developed in order to solve the electromagnetic and thermal equations in such a complex material as a multilayered composite part. The code is based on the in-plane-out-of-plane separated representation within the Proper Generalized Decomposition framework. To improve the knowledge on the process, a parameter study in carried out in this paper.

The need to characterize composite surfaces for distinct mechanical or physical processes leads to different manners of evaluate the state of the surface. During many manufacturing processes deformation occurs, thus hindering composite classification for fabrication processes. In this work we focus on the challenge of a priori identifying the surfaces’ behavior in order to optimize manufacturing. We will propose and validate the curvature of the surface as a reliable parameter and we will develop a tool that allows the prediction of the surface behavior.

Welding primary structure thermoplastic composites parts is still an issue today, many technologies have been extensively studied: induction, ultrasonic, resistive welding, none is today entirely viable for this application due to various implementation reasons. On the other hand, microwave solutions are not very common in composites forming process, although being widespread in homes. Microwave (MW) technology relies on volumetric heating. Thermal energy is transferred from an electromagnetic field to materials that can absorb it at specific frequencies. Volumetric heating enables better process temperature control and less overall energy losses, which can results in shorter processing cycles and higher process efficiency. Nowadays, the main drawback of this technology is that the complex physics involved in the conversion of electromagnetic energy in thermal energy (heating) is not entirely understood and controlled for complex materials.In that work, the authors propose to look deeper in that way, first proposing a simulation tool, based on a coupling between a commercial code and a home made one, allowing the following of the electromagnetic field very precisely in the thickness of a laminate composite part, the last consisting of a stack of layers with different orientations, each layer made of a resin matrix and carbon fibers. Thermal fields are then computed and validated by experimental measurements. In a second part, the authors propose to look at a common welding case of a stringer, on a skin.

Traditionally, Simulation-Based Engineering Sciences (SBES) has relied on the use of static data inputs (model parameters, initial or boundary conditions, ... obtained from adequate experiments) to perform simulations. A new paradigm in the field of Applied Sciences and Engineering has emerged in the last decade. Dynamic Data-Driven Application Systems [9, 10, 11, 12, 22] allow the linkage of simulation tools with measurement devices for real-time control of simulations and applications, entailing the ability to dynamically incorporate additional data into an executing application, and in reverse, the ability of an application to dynamically steer the measurement process. It is in that context that traditional "digital-twins" are giving raise to a new generation of goal-oriented data-driven application systems, also known as "hybrid-twins", embracing models based on physics and models exclusively based on data adequately collected and assimilated for filling the gap between usual model predictions and measurements. Within this framework new methodologies based on model learners, machine learning and kinetic goal-oriented design are defining a new paradigm in materials, processes and systems engineering.

In this work, a Cyber Physical System called Hybrid Twin is proposed for composite parts manufactured from RTM. This allows to introduce in the virtual twin of the parts the defect and the final properties induced by the real manufacturing process and to use on line data collection for predictive maintenance.

Thermoplastic composites are widely considered in structural parts. In this paper attention is paid to squeeze flow of continuous fiber laminates. In the case of unidirectional prepregs, the ply constitutive equation is modeled as a transversally isotropic fluid, that must satisfy both the fiber inextensibility as well as the fluid incompressibility. When laminate is squeezed the flow kinematics exhibits a complex dependency along the laminate thickness requiring a detailed velocity description through the thickness. In a former work the solution making use of an in-plane-out-of-plane separated representation within the PGD – Poper Generalized Decomposition – framework was successfully accomplished when both kinematic constraints (inextensibility and in-compressibility) were introduced using a penalty formulation for circumventing the LBB constraints. However, such a formulation makes difficult the calculation on fiber tractions and compression forces, the last required in rheological characterizations. In this paper the former penalty formulation is substituted by a mixed formulation that makes use of two Lagrange multipliers, while addressing the LBB stability conditions within the separated representation framework, questions never until now addressed.

Microwave (MW) technology relies on volumetric heating. Thermal energy is transferred to the material that can absorb it at specific frequencies. In this paper, a coupled thermic and electromagnetic model is proposed in order to simulate the emerging process of microwave heating for composite materials. Solving the problem in a laminated composite material requires a high degree of discretization in the thickness direction which is made possible by introducing the in-plane-out-of-plane decomposition approach using the Proper Generalized Decomposition (PGD).

Erosion damage, caused by repeated rain droplet impact on the leading edges of wind turbine blades, is a major cause for cost concern. Resin Infusion (RI) is used in wind energy blades where low weight and high mechanical performance materials are demanded. The surface coating plays a crucial role in the manufacturing and performance response. The Leading Edge coating is usually moulded, painted or sprayed onto the blade surface so adequate adhesion in the layers’ characterization through the thickness is required for mechanical performance and durability reasons. In the current work, an investigation has been directed into the resulting rain erosion durability of the coating was undertaken through a combination of mass loss testing measurements with manufacturing processing parameter variations. The adhesion and erosion is affected by the shock wave caused by the collapsing water droplet on impact. The stress waves are transmitted to the substrate, so microestructural discontinuities in coating layers and interfaces play a key role on its degradation. Standard industrial systems are based on a multilayer system, with a high number of interfaces that tend to accelerate erosion by delamination. Analytical and numerical models are commonly used to relate lifetime prediction and to identify suitable coating and composite substrate combinations and their potential stress reduction on the interface. In this research, the input parameters for the appropriate definition of the Cohesive Zone Modelling (CZM) of the coating-substrate interface are outlined by means of Pull off testing and Peeling testing results. It allowed one to optimize manufacturing and coating process for blades into a knowledge-based guidance for leading edge coating material development. It was achieved by investigating the erosion degradation process using both numerical and laboratory techniques (Pull off, Peeling and Rain Erosion Testing in a whirling arm rain erosion test facility).

In the context of processing long-fiber reinforced thermoplastic composites with laser-heating, the spatial distribution of the heat flux is one of the main parameters which controls the induced processing temperature. Unfortunately, the illuminated geometry might be not trivial, and the optical properties related to absorption and scattering phenomena of such a material are not well-established. In order to study and characterize the laser/composite interaction at the scale of the micro-structure, a model based on multiple cylinders is envisaged. The method consists in the calculation of a semi-analytical solution for the electromagnetic scattering from an array of circular cylinders due to an obliquely incident plane wave.

A crucial step in many composites manufacturing processes is the impregnation of fibrous medium with the resin. The fundamental property needed to quantify the flow is the permeability of the fibrous medium. Process models require the permeability as input data to predict flow patterns and pressure fields. Efficient numerical techniques are needed to solve homogenization problems with geometrical data coming from high-resolution images, involving two-scales and linear fluids. Within this frame-work, this work addresses the question of how to compute the macroscopic permeability from a microscopic description consisting of a viscous fluid flow model defined in a two-scale porous medium, considering the saturated and unsaturated cases.

This work addresses the numerical simulation of compression moulding of Sheet Moulding Compound (SMC) where the behaviour of the polymer is supposed Newtonian and thermal effects are neglected. The proposed model relies on the Stokes formulation combined with Lubrication Theory, following the approach developed in [2]. It is solved using a Finite Element-Control Volume technique that allows one to track the flow front [1] of the SMC charge of composite during the compression phase. Finally, as a first step of a longer-term effort, we address confined orientation as in [4]. We predict the orientation of the suspended fibres, incorporating confinement effects that are absent in most theoretical descriptions derived from the classical Jeffery model [3]. A simple test case is addressed to verify the validity of the proposed approach.

We address the extension of Jeffery’s model, governing the orientation of rods immersed in a Newtonian fluid, to confined regimes occurring when the thickness of the flow domain is narrower than the rod length. The main modelling ingredients concern: (i) the consideration of the rod interactions with one or both gap walls and their effects on the rod orientation kinematics; (ii) the consideration of non-uniform strain rates at the scale of the rod, requiring higher-order descriptions. Such scenarios are very close to those encountered in real composites forming processes and have never been appropriately addressed from a microstructural point of view.

In this work, we address the modeling of in-situ consolidation considering the real description of the surfaces between two pre-impregnated (pre-pregs) tapes. A walevet-based description is used to represent the real surface between pre-pregs, using the Haar wavelet. Since the surface is well described, in order to carry out the compression of both surfaces for consolidating, the flow model during the compression of each asperity is discussed: lubrication hypotheses considering partial wall slip condition at the asperities interfaces are compared to the fully numerical solution of Newtonian and non-Newtonian flows. Once the surface deformation is properly described, the thermal contact resistance is obtained by solving the thermal problem during the compression process of both surfaces. In order to make possible the fully numerical solution of all scales involved in the surface representation (due to its fractal nature), both, the Stokes and the thermal problems are solved by using the Proper Generalized ...

This paper concerns the numerical simulation of electrified jets with application to the electrospinning process for the fabrication of fibers with controllable size, diameter, and cross section shape. Most numerical models used to simulate electrospinning rely on the Upper Convected Maxwell model (UCM) which is fit to model polymer melts. However, in most electrospinning processes the fluid is a polymer solution with a Newtonian solvent that evaporates after the fiber is deposited on the collector. In this work we propose to describe the fluid rheology using Giesekus model, which predicts the properties of polymer solutions more accurately, and show the impact of the rheological model on the prediction of the fiber radius and size.

In this paper a model of Transversely Isotropic Fluid (TIF), developed by Pipkin in [1], is presented and used for example to model in 2D the in-plane shearing of UD prepreg. This problem demonstrates the need to have a continuous fiber tension field over the elements, with the final objective of detecting the wrinkling of fibers during the forming process, at the price of a lower accuracy of the velocity field.

A coupled thermic and electromagnetic model is proposed in this paper in order to simulate the emerging process of microwave heating for composite materials. Solving the problem in a laminated composite material requires a high degree of discretization in the thickness direction which is made possible by introducing a new simulation approach using the Proper Generalized Decomposition (PGD).