# Chen Li

Doctorant - Institut Universitaire de Technologie de Tarbes (IUT de Tarbes)Membre du groupe Matériaux et Structures Composites (MSC)IUT, 1 rue Lautréamont 65016 Tarbes (recherche) |

**Activités de recherche :**

Simulation numérique

de la fabrication de composites à renfort fibreux 3D par le procédé d’infusion

Doctorant: Chen LI^{1}

Encadrants:

Xiaojing GONG^{2}, Arthur CANTAREL^{3}

^{1}* lichen.buaa@gmail.com*^{}

^{2}* xiaojing.gong@iut-tarbes.fr**,** *^{3}* arthur.cantarel@iut-tarbes.fr*

**Résumé** : La fabrication de pièces composites structurales aéronautiques

nécessite l'utilisation de renforts complexes et notamment des renforts tridimensionnels.

Le procédé d'infusion permettrait la fabrication de ces pièces tout en

maitrisant leur qualité et les coûts. L'objectif de la thèse est de développer

un modèle, à différentes échelles, de l'écoulement de résine à traverse le

réseau fibreux du renfort et de proposer une simulation numérique plus fine du

procédé d'infusion. L’influence des structures de renforts 2D et 3D, sera ainsi

étudié aux différentes échelles: micro (intra-mèches), méso (inter-mèches)

et macro (renfort, pièce).

**Abstract **"” The

manufacture of composite aeronautical structural parts requires the use of more

complex reinforcements, especially the 3D reinforcements. Resin infusion is the

key process of Liquid Composites Molding (LCM) which will determine the quality

and cost of the parts. The target of this thesis is to develop models at

different scales of fibrous network of the reinforcement and to propose a finer

numerical simulation of the infusion process. The influence of the 2D and 3D

reinforcement structures on the infusion process will be studied at the different

scales: micro (intra-tow), meso (inter-tows) and macro (reinforcement, part).

1. Introduction

LCM is

a promising method for composites manufacture with various advantages. It has

four main steps including preform set, resin infusion, curing and disclosing

process. Among all these processes, infusion is the most important step which

will determine the final quality of the part. Thus, numerical simulation of the

resin infusion is meaningful [1]. The work performed and the results obtained

will be presented in the second part, which mainly focus on the permeability

estimation on random fiber models [2] and dual scales models and then the

future work is listed in the perspective.

2. Permeability estimation intra tow in the

section (2D)

For porous media, permeability tensor

*K*

is the most significant parameter to describe the property of the reinforcement

for infusion processing. As an intrinsic property of the porous material, *K*

can be calculated by Darcy's law based on the velocity field obtained by solving

Navier-Stokes equation and continuity equation together. Hence, the Stokes

equation can be used for free flow with the consideration of incompressible

fluid and the inertial term can be neglected in micro, meso and macro scales.

The

random position and size of the fiber producing codes are developed to set up

realistic geometrical models. Numerical simulation has been realized based on

these models.

In fact,

we have studied the influences of several parameters on the flow of the resin

during infusion. It includes 3 micro-structural parameters: *Î´ _{min}*,

*L*,

*Î”*

*r*and a

macro parameter:

*Îµ*. Here

*Î´*

_{min}_{ }is defined as

the minimum distance between two neighbor fibers among all the fibers;

*âˆ†r*is the range of the fiber radius,

*L*is the length of the square domain and

*Îµ*is the porosity. We have also used

Morris sensitivity method to analyze the influences of these parameters.

Porosity

*Îµ*has the most obvious

influence on permeability while

*L*has

a significant effect on average velocity compared with other parameters. These

influences observed in a Representative Elementary Volume (REV) can be

generated to whole structure.

3. Permeability estimation of dual scales in 3

directions

In order to estimate the permeability in 3 directions

using dual scales: intra and inter tows, the model with random position codes

have been developed in this work. The idea of this model is to generate the

real position of the fibers, the determination of the permeability of 3

directions can be achieved by applying the calculation method mentioned above for

intra as well as inter tow. The results from this model seem very promising,

because the permeability obtained in the transverse section (Fig. 1) correlate

well with the results published in the reference [3]. Moreover, the

permeability in the longitudinal direction obtained from

this model is much closed to that calculated by traditional method. Actually, to our knowledge no

any other works has been realized in the literature on the determination of 3D permeability at dual scales.

(1) Adaptable

3D geometrical models of braided and woven fiber will be studied to set up for

numerical simulation.

(2) The two phases coupling free flow and porous flow will be studied to

detect the infusion character on both of 2D and 3D models. Parameters of

structure which may influence the infusion process will be defined. Their

interactive influences on the infusion will also be explored.

(3) A final method will be developed for flow front prediction at macro

scale with various local permeability on different position of the part(Fig. 2 for 3D simple part and Fig. 3 for 3D car bonnet).

Figure. 2. Macro porous flow at part level (3D simple part)

Figure. 3. Macro infusion process at part level (3D car bonnet)

References

[1]R.

Gantois, A. Cantarel, B. Cosson, G. Dusserre, J.-N. Félices, F. Schmidt, BEM-based

models to simulate the resin flow at macroscale and microscale in LCM

processes, Polymer Composites, 34 (8), 2013

[2]F.

Zhang, B. Cosson, S. Comas-Cardona, C. Binetruy, Efficient stochastic

simulation approach for RTM process with random fibrous permeability.

*Composites Science and Technology*,

71, 2011.

[3]W.R. Hwang, S.G. Advani. Numerical simulations of Stokes-Brinkman equations for permeability

prediction of dual scale fibrous porous media.* Physics of Fluids*, 22 (11), 2010