NIANG Ndeye Fatim : "Study and understanding of the pellet-based 3D printing process for bio-based composites reinforced with short hemp fibers: applications to the study of mechanical behavior"

PhD Abstract : Plant fibres are an environmentally friendly alternative compared to synthetic fibres that dominate the composites market. Short plant fibre-based composites are lightweight, inexpensive, and have good mechanical properties. They are widely used in injection moulding in the automotive industry. However, their mechanical properties obtained after additive manufacturing by 3D printing do not yet rival those achieved through injection moulding, despite advances in understanding the printing process.
The objective of this thesis is to master 3D printing using PLA reinforced with short hemp fibres to improve their mechanical properties.
Using a pellet-based 3D printer, a formulation containing 20 % hemp fibres was developed, offering a good balance between extrusion quality and mechanical performance. Tensile and flexural tests revealed competitive properties, in line with expectations for this type of biocomposites. Additionally, a viscoelastic-plastic model was developed to predict the mechanical behaviour of these materials under various stresses, including uniaxial tension, relaxation, and creep.
This study demonstrates the potential of pellet-based 3D printing for the fabrication of biocomposites, while identifying optimization avenues to improve print quality and result reproducibility, thereby reinforcing the appeal of these materials in sustainable industrial applications

Jury Composition : 

• Mr. Guessasma Sofiane - Research Director, INRAE Nantes - Rapporteur
• Mr. Bourmaud Alain - Research Engineer, HDR UBS-IRDL - Rapporteur
• Mr. Bouvard Jean-Luc - University Professor, Mines Paris Tech - Examiner
• Mr. Charmeau Jean-Yves - University Professor, INSA Lyon - Examiner
• Mr. Sahli Mohamed - Associate Professor, University of Caen - Examiner
• Mr. Barriere Thierry - University Professor, UFC - Thesis Supervisor
• Mr. Placet Vincent - Research Engineer, UFC - Co-supervisor
• Mr. Holopainen Sami - Postdoc Researcher, Tampere University, HdR UFC - Co-supervisor
• Mr. Daux Virgile - Engineer, APM Dijon - Guest