Postdoc position (M/F) - Mechanics of paper materials – 3D in situ imaging and digital twin

Job Description

Missions

The packaging industry relies on more than 140 million tons of petroleum-based polymers every year, a major source of greenhouse gas emissions and pollution. Meanwhile, paper is an attractive bio-based, renewable, recyclable alternative, but its use as a lightweight and strong alternative material remains limited by its relatively low ductility and strength. Paper damage and failure almost always occur in the fiber-fiber bond zones: improving the strength and strain at failure of cellulose fiber mats therefore requires a much finer understanding of the physics and mechanics of fiber-fiber bonds and of the fiber walls surrounding them. This is precisely the ambition of the ANR FIBERBOND project (2024–2028) around the objective of drastically improving the ultimate strength and strain of wet-formed cellulose fiber mats, by enhancing the fiber-fiber bonds mechanics using physical and chemical processing routes.

Activity

The recruited postdoctoral researcher will contribute to this project. She/He will be in charge of (i) characterizing the micromechanics of fiber and fiber bonds in fiber mats and (ii) building a digital twin of the corresponding experiments. More specifically:

• Mechanical tests will be carried out at controlled relative humidities on model papers using a dedicated micro-tensile machine coupled with 3D real-time in situ observation using synchrotron X-ray microtomography (ESRF).
• 3D Image analysis routines will be used to identify fibers and fiber-fiber bonds within the reconstructed 3D images as well as 3D kinematical fields (Digital Volume Correlation).
• A digital twin of the tested fiber mats will be developed using the Multi-Particle Finite Element Method (MPFEM), each fiber being represented as a deformable finite-element body, interacting with its neighbours through contact/cohesive-zone laws at the fiber-fiber bonds. These local laws (stiffness, strength, debonding) will be identified from the 3D images, to reproduce the deformation and failure mechanisms of fibers (bending, collapse) and bonds (adhesion, friciton), and to feed a mechanical model at the upper scale

Your Profil

Skills

- Requested degree: PhD in mechanics of materials or materials science with a (solid) background in experimental and/or numerical (finite element) mechanics

- Keywords: Paper and fibrous materials, X-ray microtomography, in situ mechanical testing, Image analysis, Multi-Particle Finite Element Method (MPFEM), Digital twin


- Mots-clés : Papier et matériaux fibreux, microtomographie Rx, essais mécaniques in situ, analyse d'images, méthode des éléments finis multi-particules (MPFEM), jumeau numérique

Your Work Environment

- Context: The proposed position is part of the ANR project FIBERBOND (2024–2028) involving four academic labs – LGP² (CNRS/Grenoble INP), CERMAV (CNRS/UGA), LaMCoS (CNRS/INSA Lyon), 3SR Lab (CNRS/UGA/Grenoble INP) – and the CTP (Centre Technique du Papier). The recruited person will work within the 3SR Lab and LGP², under the supervision of L. Orgéas (CNRS Research Professor), B. Harthong (Associate Professor) and J. Viguié (Research Engineer, LGP²), with strong interactions with the CTP, LGP2 and LaMCoS teams involved in the project.

- Location: the postdoc project will be mainly located at 3SR Lab, a solid mechanics research lab of the CNRS and the Univ. Grenoble Alpes (Grenoble, France, https://3sr.univ-grenoble-alpes.fr/). Some of the experiments will be carried out at the European Synchrotron Research Facilities (ESRF, Grenoble), i.e., for mechanical tests with 3D in situ imaging using the X-ray tomographs of the BM05 beamline.

Compensation and benefits

Compensation

3041€/month

Annual leave and RTT

44 jours

Remote Working practice and compensation

Pratique et indemnisation du TT

Transport

Prise en charge à 75% du coût et forfait mobilité durable jusqu’à 300€

About the offer

About the CNRS

The CNRS is a major player in fundamental research on a global scale. The CNRS is the only French organization active in all scientific fields. Its unique position as a multi-specialist allows it to bring together different disciplines to address the most important challenges of the contemporary world, in connection with the actors of change.

CNRS

The research professions