Micromechanical modeling-based self-consistent scheme of polymer-layered silicate nanocomposites

Although few investigations recently proposed to describe the overall elastic response of polymer-clay nanocomposites using micromechanical-based models, the applicability of such models for nanocomposites is far from being fully established. In this communication, we present a micromechanical approach for the prediction of the overall moduli of polymer-clay nanocomposites using a self-consistent scheme based on the double-inclusion model. The efficiency of the proposed model to predict the experimental elastic response of various polymer-clay nanocomposites is pointed out

Profil radiologique des traumatises de la voie publique : A propos de 420 cas.

Objectifs : évaluer les aspects épidémiologiques des traumatisés de la voie publique, de répertorie radiologiquement des lésions traumatiques observées et de préciser leur fréquence.Patients et méthode : Il s’est agi d’une étude transversale de 420 patients victimes d’accident de la voie publique reçus au service de Radiologie et d’Imagerie Médicale et au pavillon Scanner du CHU Sylvanus Olympio de Lomé de Juillet 2012 à Décembre 2012 pour une exploration radiologique.Résultats : notre échantillon comporte 308 hommes et 112 femmes avec un sex ratio de 2,75. La majorité de nos patients était des élèves et étudiants avec 26.90% des cas. La plaie a été le signe physique le plus fréquent représentée avec 236 cas (56,19%). A la radiographie standard les lésions ont été observées chez 287 patients (86,55%).Les fractures des membres inférieurs ont représenté 84,88%. Cent trente-six (136) patients ont réalisé le scanner crânio-encéphalique et 97 patients présentaient des lésions traumatiques. Il se dégageait une prédominance des lésions péri cérébrales (51,54%) dont 50% d’hématome sous-dural et 40% d’hématome extra-dural.Conclusion : les traumatismes par AVP restent élevés. Le profil des traumatisés de la voie publique est celui d'un adulte jeune de sexe masculin, pouvant être soit un passager soit un piéton. Ainsi, les traumatismes par accident de la voie publique demeurent un problème de santé publique dans notre pays.Mots clés: AVP, lésions, aspects radiologiques, radiographie standard, TDM, Afrique noire.ABSTRACTObjectives: To evaluate the epidemiological aspects of trauma of the highway, lists of radiologically observed injuries and specify their frequency.Patients and methods: It was a matter of a cross sectional study of 420 patients victims of highway accidents received Radiology Department and Medical Imaging and pavilion Scanner CHU Sylvanus Olympio Lome July 2012 to December 2012 radiological exploration. Results: Our sample includes 308 men and 112 women with a sex ratio of 2.75. The majority of our patients was of pupils and students with 26.90% of cases. The wound was the most common physical sign represented with 236 cases (56.19%). A standard radiography lesions were observed in 287 patients (86.55%). The lower extremity fractures accounted for 84.88%. One hundred and thirty six (136) patients completed the Cranioencephalic scanner and 97 patients had traumatic injuries. It gave off a predominance of brain lesions died (51.54%), 50% of subdural hematoma and 40% of extra-dural hematoma.Conclusion: AVP by trauma remain high. The public road traumatized profile is that of a young adult male, which can be either a passenger or a pedestrian. Thus, trauma by highway accident remains a public health problem in our country.Keywords: AVP, injuries, radiological aspects, plain radiography, CT, Black Africa

Micromechanics-based constitutive modeling of plastic yielding and damage mechanisms in polymer-clay nanocomposites: Application to polyamide-6 and polypropylene-based nanocomposites

International audienceThe present work focuses on the continuum-based micromechanical modeling of the elastic-plastic stress-strain response including damage mechanisms of polymer-clay nanocomposites. The micromechanical elastic-plastic-damage model includes both the actual microstructure of the said composites using a multi-scale approach and the microstructural evolution related to damage accumulation under applied macroscopic deformation. The interfacial debonding between clay nanoparticles and polymer matrix, and the polymer matrix voiding are the two prevalent damage events considered. The tensile stress-strain response and micromechanical deformation processes of polyamide-6 and polypropylene-based systems reinforced with modified montmorillonite clay at various concentrations are experimentally investigated by a video-controlled technique. The usual shear yielding deformation mode of neat polyamide-6 is altered by the presence of clay platelets which induce a dilatational process due to interfacial debonding. In addition to matrix shear yielding, a dual-dilatational deformation mechanism by crazing and interfacial debonding is revealed in polypropylene-clay nanocomposites. Using the intrinsic deformation micromechanisms and elastic-plastic properties of the polymer matrix, and the nanocomposite structural characteristics, the micromechanical model is found to successfully describe the experimental results of the two nanocomposite materials in terms of tensile stress-strain response and inelastic volumetric strain