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Double bandgap formation in a locally resonant metamaterial micromorphic beam
No full textInternational audienc
Vibration and stability of two-phase peridynamic Euler-Bernoulli beams under general boundary conditions - Exact and numerical approaches
No full textInternational audienc
Influence of precursor molecular weight on swelling and elastic modulus of cross-linked PDMS films
No full textInternational audienceThe influence of precursor molecular weight on cross-linked poly(dimethylsiloxane) (PDMS) thin films was studied at constant cross-linker ratio. Increasing molecular weight lowers cross-link density, enhances swelling, and reduces elastic modulus
Processing of Poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P(3HB-co-4HB)) Using Acetic Acid: An Eco-friendly Alternative to Chloroform
No full textInternational audienceAbstract The pervasive accumulation of plastic waste in terrestrial and aquatic environments has become a critical environmental issue, largely due to the resistance of petroleum-derived polymers to microbial degradation. This persistence leads to the long-term generation of microplastics and widespread ecosystem contamination. As a response, biodegradable and bio-based materials such as polyhydroxyalkanoates (PHA) have emerged as promising sustainable alternatives. Among them, poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P(3HB-co-4HB)) is a microbial polyester that exhibits excellent biodegradability, biocompatibility, and tunable mechanical properties. Owing to these characteristics, P(3HB-co-4HB) can be employed in a wide range of applications, from environmentally friendly packaging to biomedical devices. However, its processing has traditionally relied on toxic solvents such as chloroform. In this study, acetic acid is evaluated as a green alternative solvent for producing P(3HB-co-4HB) films and porous gels. Compared with chloroform, acetic acid caused moderate reductions in molecular weight (–12% for 10 mol% 4HB and − 5% for 34 mol% 4HB) and slight decreases in thermal stability, while degradation kinetics remained unaffected. DSC analyses revealed enhanced melting enthalpy for P(3HB-co-10 mol%4HB) films and the emergence of additional crystalline populations for P(3HB-co-34 mol%4HB). Mechanical tests showed moderate reductions in ductility and modulus at low 4HB content, whereas high 4HB content was unaffected. FTIR spectra confirmed the absence of solvent-induced chemical modifications. In addition, a simple thermally induced phase separation method produced highly porous (≈ 90%) gels. Overall, this study demonstrates that acetic acid offers a sustainable processing route for P(3HB-co-4HB), while preserving key material properties comparable to those obtained with chloroform
La vigne et l’herbe : alimentation et environnement végétal au château de Thouars au XVe siècle
No full textAu XVe siècle, l'image des sires de La Trémoïlle, réputés amateurs de viande, masque une réalité plus nuancée : l'alimentation aristocratique repose avant tout sur le pain et le vin, produits de vastes redevances céréalières et viticoles. Les comptes de Thouars révèlent une consommation végétale bien plus large qu'il n'y paraît : légumes modestement présents, souvent issus de l'autoproduction, mais fruits variés, consommés frais ou secs selon les saisons, parfois valorisés pour leurs vertus symboliques et médicinales. Le végétal intervient aussi dans l'hygiène et la pharmacopée, témoignant de l'influence des savoirs médicaux savants. Autour du château, jardins, vergers, vignes et cultures céréalières structurent un paysage intensément exploité, complété par les ressources forestières. Si la viande domine dans les représentations culturelles de l'aristocratie, les sources comptables mettent en évidence le rôle essentiel et multiforme des productions végétales dans l'économie, la santé et la vie quotidienne seigneuriale
Replacing strain gages by line camera DIC in Hopkinson bar experiments
No full textInternational audienc
Dire l'aidance dans le cas de la maladie d'Alzheimer : du dit, du suggéré à l’impensé,
No full textInternational audience« Je ne suis pas son aidante, je suis sa femme ». Malgré une visibilité grandissante de l’aidance dans l’espace public se dire « aidant » reste compliqué. Le mot véhicule des représentations sociales empreintes de valeurs contradictoires. Dans le contexte de la maladie d’Alzheimer, il s’inscrit en plus dans un impensé culturel : celui de vivre avec une maladie qui efface progressivement l’histoire sur laquelle s’est construit le lien affectif et pourtant d’accepter le rôle d’aidant en vertu de ce lien. Le choix d’aborder l’aidance par les discours, par une analyse des mots et formulations langagières, permet de comprendre comment ces discours (re)construisent une identité dans et à travers l’aidance. Nous identifions ainsi des pratiques plus ou moins opérationnelles, des savoirs progressivement construits, mais aussi des résistances – matérielles ou subjectives – auxquelles les aidants se heurtent pour assumer les tâches nécessaires, sans négliger les sources de satisfaction ou d’insatisfaction qu’ils trouvent dans la relation d’aide. L’ouvrage, inscrit en sciences du langage, apporte un point de vue complémentaire à celui des sciences humaines et sociales sur un maillon essentiel de la chaine de soin mais encore mal connu et reconnu
Modelling the yield stress of cement pastes and mortars containing heterogeneous and unconventional aggregates like raw crushed wind turbine blade
No full textInternational audienceAbstract Determining the yield stress of cementitious materials is crucial for casting and concrete mix design. Fresh concrete possesses yield stress, behaving as a solid with viscoelastic properties below this threshold. When the yield stress is exceeded, concrete flows with a steady-state behavior commonly described by the Bingham or Herschel-Bulkley models. As the construction industry increasingly consumes more and more scarce raw materials, there is a growing need to develop and explore alternative construction materials to replace traditional ones while valorizing waste. Raw Crushed Wind Turbine Blade (RCWTB) has demonstrated interesting results when included in cementitious mixtures. However, a full characterization of rheology including the yield stress of mixtures containing RCWTB is still missing and would be of great practical interest. In this paper, the yield stress of cementitious pastes and mortars containing RCWTB with two different water/cement ratios is measured. Results demonstrate higher yield stress for higher RCWTB inclusion, this is mainly due to the bridge effect of the Glass Fiber Reinforced Polymer (GFRP) contained in the RCWTB. Finally, a physical model is applied for RCWTB to predict GFRP fibers maximum packing fraction based on their geometry, elastic properties, and the rheology of the surrounding cement-based material. This model is then validated with experimental yield stress of cement pastes and mortars
