At IRDL, Jean-Baptiste Ledru explored the potential of biocomposite actuators produced through 4D printing.
The Essentials: At IRDL, Jean-Baptiste Ledru explored the potential of biocomposite actuators produced through 4D printing.
Jean-Baptiste Ledru, researcher at IRDL (Institut National Polytechnique de Bretagne).
Thesis defended in 2026 at the doctoral school École doctorale Sciences Pour l'Ingénieur (Lorient ; 2022-....).
Listed in the ABES/STAR network, this thesis meets the rigor criteria of French higher education.
Context and Research Problem
Hygromorphic biocomposites (HBC), made of PLA reinforced with continuous flax fibers (cFF/PLA), represent a significant advance in the field of sustainable materials. These materials are designed to function as bio-inspired passive actuators, exploiting programmable architectures whose mechanical properties vary depending on the orientation and spatial arrangement of the components. The study of these biocomposites raises questions about their manufacturing and performance, particularly in relation to coextrusion and slicing processes.
Optimizing manufacturing processes is of critical importance, since variations in draw speed and temperature during filament production can influence the material's stiffness while generating microdefects such as porosity. These defects can compromise actuator efficiency, making in-depth research into production parameters and their impact on the mechanical properties of biocomposites necessary.
Methodology
The study relies on an experimental protocol developed to evaluate HBC performance based on different geometries and manufacturing parameters. Six distinct experimental methods were implemented to measure the forces and displacements generated by the actuators. The geometries analyzed include cubic and tubular shapes, each offering distinct characteristics in terms of actuation efficiency.
Biocomposite performance was normalized by specific energy density to allow direct comparison with natural actuators such as wood. This methodological approach makes it possible to quantify the impact of different geometric configurations on the actuation capabilities of the biocomposites.
Key Findings
The results indicate that increasing draw speed and temperature during the manufacturing of biocomposite filaments leads to increased stiffness, but can also cause the appearance of microdefects that impair performance. These microdefects, particularly porosity, are limiting factors that require particular attention when optimizing manufacturing processes.
HBC performance is comparable to that of natural actuators, validating their application potential in a variety of contexts. Cubic geometries proved most effective for generating rectilinear forces, while tubular geometries offer a favorable trade-off for more complex movements, indicating a diversity of potential applications for these biocomposites.
The research also highlights the importance of multi-scale design, integrating process, material, and geometry parameters. This holistic approach is essential to maximizing the efficiency of biocomposites in real-world applications.
Discussion and Outlook
Coupling biomimicry with 4D printing in biocomposite design opens promising avenues for the development of adaptive passive systems. Integrating these principles could transform our approach to materials, addressing contemporary challenges in a sustainable and effective way. The results obtained underscore the need for continued research into manufacturing processes and the optimization of biocomposite mechanical properties.
The implications of this research go beyond mere materials innovation. They raise economic and environmental considerations regarding the large-scale deployment of these technologies. Exploring new materials and processes could lead to innovative solutions to meet growing sustainability requirements across various sectors. Future work could focus on improving manufacturing techniques and exploring new material combinations to optimize biocomposite performance in specific applications.
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Sources and Access
Jean-Baptiste Ledru. Contribution à l'étude des forces et des énergies générées par des actionneurs biocomposites fabriqués par impression 4D. Matériaux. Université de Bretagne Sud, 2026. Français. ⟨NNT : 2026LORIS758⟩. ⟨tel-05648823⟩