ED Sciences Chimiques
Synthesis of biobased amphiphiles combining oligoxylanes and fatty acid derivatives
by Manon CARRE (Laboratoire de Chimie des Polymères Organiques)
The defense will take place at 9h30 - Amphithéâtre CRPP 115 Avenue du Dr Albert Schweitzer 33600 Pessac
in front of the jury composed of
- Henri CRAMAIL - Professeur - Université de Bordeaux - Directeur de these
- Thierry BENVEGNU - Professeur - Université de Rennes - Rapporteur
- Stéphane GRELIER - Professeur - Université de Bordeaux - CoDirecteur de these
- Muriel BLANZAT - Chargée de recherche - Université Toulouse III – Paul Sabatier - Rapporteur
- Maud SAVE - Directrice de recherche - Université de Pau et Pays de l'Adour - Examinateur
- Guillaume CHOLLET - Docteur - ITERG - Examinateur
This thesis is part of the development of biobased surfactants that meet environmental and industrial challenges, in particular the development of bioresources and the reduction in the use of fossil fuels. These surfactants, derived from oligosaccharides and fatty acids, aim at offering environmentally-friendly alternatives and increase the catalogue of biobased surfactants available on the market. In this work, Xylans from maize cobs, mainly composed of Xylobiose and Xylotriose, were used and coupled with fatty acid derivatives (oleic, ricinoleic and stearic) previously functionalized by transamidation with a diamine. The surfactants were synthesized by coupling the two biobased blocks. Reductive amination was carried out between the aldehyde functions at the reducing end of the xylans and the amine function brought by the fatty acid derivatives. Initially, the reducing agent NaBH3CN was used, and then replaced by the reducing agent picoline-borane (Pic-BH3), which did not present any toxicity problems. Different acid catalysts (ethanoic acid and HCl) were investigated in these latter cases. The use of ethanoic acid led to purification issues, which have an impact on the physicochemical properties of the various surfactants obtained. The self-assembly and surface-active properties of different surfactants with the structure XOS2,7-NH-Cx (with x : 8, 12, 18:1) or XOS2,7-NH-C4-CONH-Cy (with y : C18:1, C18:1(OH), C18:0) were evaluated by measuring surface tension at the water/air interface (hanging drop), light diffusion and electron microscopy. Relationships between structure and properties were established. It was also shown that environmental factors linked to the different synthesis processes, in particular the difference in pH, had also an impact on the surfactant properties. Finally, the surfactants were applied to the stabilization of O/W emulsions and appear promising for this type of application, although the formulation will need further optimization to obtain stable emulsions over time.
ED Sciences Physiques et de l'Ingénieur
Study of cracking mechanisms of bonded composite joints and crack propagation / disbond arresting features
by Pierre PLUMEL (I2M - Institut de Mécanique et d'Ingénierie de Bordeaux)
The defense will take place at 9h30 - Amphithéâtre (à définir) Site ENSAM - Esplanade des Arts et Métiers 33405 TALENCE
in front of the jury composed of
- Christophe BOIS - Professeur des universités - Université de Bordeaux, I2M - Directeur de these
- Éric PAROISSIEN - Professeur - ISAE-SUPAERO, ICA Toulouse - Rapporteur
- Julien JUMEL - Professeur - ENSTA Bretagne, IRDL - CoDirecteur de these
- Olivier CATY - Maître de conférences - INP Bordeaux - ENSEIRB/MATMECA, LCTS - Examinateur
- Véronique LAZARUS - Professeure - ENSTA Paris, IMSIA - Examinateur
- Christian HOCHARD - Professeur des universités - Aix Marseille Université, LMA - Rapporteur
- Jean-François CARON - Directeur de recherche - Ecole des Ponts, laboratoire Navier - Examinateur
This thesis is part of the development of assembly solutions for composite structures, with a particular focus on bonding. This assembly technique offers numerous advantages in terms of lightweight design, reduced mechanical stress, and the ability to join heterogeneous materials. However, its integration into structural applications, particularly in the space sector with ArianeGroup, is hindered by challenges related to the reliability of bonded joints. The main objective of this research is to analyze the cracking mechanisms in bonded composite joints and to evaluate the effectiveness of crack arrest devices (DAF) in limiting damage propagation. An experimental and numerical approach is adopted to understand and model these phenomena. The first part of the thesis presents a state-of-the-art review on composite bonding, including the technologies used, surface preparation techniques, control methods, and the different types of failure observed. The fragility of bonded assemblies largely results from the rapid propagation of cracks, which justifies the need for solutions to improve damage tolerance. Next, an experimental study is conducted using Cracked Lap Shear (CLS) tests to characterize crack propagation in bonded joints. Different surface conditions, adhesive types, and joint architectures are tested to identify the key parameters influencing crack resistance. Microscopic and micro-tomographic observations are used to track the evolution of damage. A finite element numerical model is then developed to simulate the behavior of bonded assemblies under mechanical loading. The cohesive zone method and linear fracture mechanics approach are employed to evaluate mode mixity and energy release rates during crack propagation. The models are validated by comparison with experimental results. Finally, the thesis explores the effectiveness of two crack arrest device (DAF) concepts. The first relies on a clamping system, studied as a simplified case to understand the interactions between cracking and mechanical reinforcements. The second focuses on a bolted DAF, which combines bonding and mechanical fastening to slow crack propagation. Mechanical tests and failure analyses help identify the optimal configurations to enhance the robustness of bonded joints. In conclusion, this research provides a better understanding of cracking mechanisms in bonded assemblies and highlights technical solutions to improve their damage tolerance. The findings pave the way for a better integration of bonding technology in high-performance composite structures, particularly in aerospace and aeronautical applications.
ED Sociétés, Politique, Santé Publique
Mother tongue and learning of a second language in a Lebanese sociodidactic context.(The case of Arabic-speaking GS students from private schools in North Lebanon in a French class)
by Rania EL HALLAL (Laboratoire d'épistémologie et didactiques disciplinaires, professionnelle et comparée de Bordeaux)
The defense will take place at 9h00 - Salle INSPE 160 Av. de Verdun, 33700 Mérignac
in front of the jury composed of
- Marie-Anne CHATEAUREYNAUD - Professeur des universités - Université de Bordeaux - Directeur de these
- Alain VIAUT - Directeur de recherche émérite - Maison des sciences humaines de Bordeaux UMR5478 Iker - Rapporteur
- Naim ROUADI - Professeur émérite - Université de Balamand (retraité), Université saint Joseph - Rapporteur
- Marie-France BURGAIN - Maîtresse de conférences - INSPE de l'Académie de Bordeaux - Examinateur
- Scarlette SARRAF - Professeure des universités - Université Libanaise- Faculté de Pédagogie section 2 - Examinateur
This research explores the role of the mother tongue in the learning of French as a second language (FSL) in the Lebanese education system, marked by omnipresent plurilingualism. Through a study of parents and teachers in the pre-school cycle, particularly in Grande Section (GS), it sheds light on the country's sociolinguistic dynamics and the impact of translanguaging on the acquisition of French. Lebanon is a country where Arabic, French and English coexist, generating varied language practices such as codic alternation. Education is based on a multilingual model, with subjects often taught in French or English from an early age. This configuration underlines the importance of the mother tongue as a cognitive support enabling pupils to conceptualize notions before transposing them into the second language. However, the education system imposes a teaching style that most often limits the use of the mother tongue in the classroom. Despite regulations designed to encourage direct immersion in the target language, codic alternation is frequently used, showing a gap between educational policies and actual teaching practices. Teachers and parents recognize its usefulness in facilitating the understanding and learning of French. The use of translanguaging appears to be an alternative to the prohibition of the mother tongue in second language teaching. By enabling students to exploit all their linguistic resources, this approach promotes more natural learning and boosts their confidence. In a country where children move between several languages on a daily basis, translanguaging is a relevant pedagogical lever. The field study was based on data collection, including a questionnaire for parents, interviews with teachers and classroom observations. The results tend to show that alternating between Arabic and French improves comprehension and encourages pupil participation. In conclusion, this research highlights the need to integrate the mother tongue more flexibly into Lebanese educational practices. Translanguaging could be an approach better adapted to the country's sociolinguistic realities, facilitating FSL acquisition and reducing student frustration. Comparative studies of different pedagogical approaches would enable language policies to be fine-tuned to optimize academic success in a multilingual context.