Within IRDL, Kilian Demilly explored the impact of damage on the fatigue of composite materials.
Kilian Demilly, chercheur·e au sein de IRDL (Institut National Polytechnique de Bretagne).
Thèse soutenue en 2025 à l'école doctorale École doctorale Sciences pour l'ingénieur et le numérique.
Référencée dans le réseau ABES/STAR, cette thèse répond aux critères de rigueur de l'enseignement supérieur français.
Research on laminated composite materials is crucial in many sectors, including aerospace, automotive, and construction. These materials, valued for their lightness and strength, have become essential in the design of modern structures. However, despite their many advantages, these composites can undergo degradations that compromise their performance and safety. The study conducted by Kilian Demilly focuses on the influence of initial damage on the fatigue properties of unidirectional (UD) laminated composites. By integrating self-heating measurements, this research aims to assess the residual lifespan of these materials, a major issue for ensuring their reliability in critical applications.
Laminated composites are often subjected to repeated loading conditions, which can lead to failures. For example, in the aerospace sector, aircraft structures must withstand extreme pressure and temperature cycles, which can cause cracks invisible to the naked eye. The impact of initial damage, such as a shock or cracking, can be decisive for the durability of the materials. Previous studies have shown that even small imperfections can propagate and lead to catastrophic failures. The use of advanced techniques, such as X-ray tomography, allows for the observation of delaminations and cracks, thus providing a better understanding of failure mechanisms. This rigorous experimental approach is essential for developing standardized testing protocols that could revolutionize the evaluation of composite fatigue.
Self-heating measurements, which involve monitoring the temperature of materials during their loading, add an additional dimension to durability assessment. By detecting thermal variations, it is possible to anticipate degradations and evaluate the residual lifespan of composites. For example, an increase in temperature could indicate increased friction within the material, signaling the onset of failure. This paves the way for innovations in the design and use of materials, particularly in sectors where safety is paramount. By integrating these measurements into testing protocols, engineers can better predict the behavior of materials under real conditions, which is essential for applications such as bridges, buildings, or vehicles.
However, this research raises questions about the standardization of tests and the integration of new methods into industrial practices. Decision-makers must consider how these advancements can be implemented to improve the reliability of composite materials. The transition to self-heating-based testing methods requires close collaboration between researchers, industry professionals, and standardization bodies. The stakes are high: ensuring the safety and durability of structures using these materials while meeting the growing demands of the markets. Furthermore, it is crucial to train engineers and technicians in these new methods to ensure effective adoption.
In conclusion, Kilian Demilly's study offers a new perspective on the management of fatigue in composite materials. By integrating self-heating measurements into evaluation protocols, it is possible to enhance the understanding of composite performance under real conditions. This could not only strengthen the safety of critical applications but also stimulate innovation in the composite materials sector. At the regional level, particularly in West Africa, where infrastructures are rapidly developing, the application of this research could have a significant impact. By integrating more reliable composite materials into constructions, it could improve the durability of infrastructures while reducing long-term maintenance costs. Thus, this research is not limited to mere academic interest but is part of a dynamic of technological progress and safety for all.
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Sources et accès
Kilian Demilly. Influence d'un endommagement initial sur les propriétés à la fatigue des matériaux composites stratifiés UD : apport des mesures d'auto-échauffement pour évaluer la durée de vie résiduelle. Mécanique des structures [physics.class-ph]. École Nationale Supérieure de Techniques Avancées, 2025. Français. ⟨NNT : 2025ESTA0014⟩. ⟨tel-05589446⟩