Innovative conductive polymer composite coating for aircrafts lightning strike protection

A new kind of high electrical conductive epoxy coating with low filler rate was investigated for lightning strike protection (LSP) of carbon fiber reinforced polymer (CFRP). The coating without CFRP substrate was firstly studied. The influence of silver submicronic wires (AgSWs) with a high aspect ratio on the electrical behavior is observed; that is, the electrical resistivity evolution, the current density value, and the electrical conduction mechanisms as function of temperature. The preponderant electrical conduction mechanism is an Ohmic behavior. The higher level of conductivity obtained is 5.5 × 105 S m−1 for 9% vol of AgSWs. Lightning strike tests were carried out on an epoxy/AgSWs coating filled with 8% in volume (74 gsm) and deposited on a CFRP. The ultrasonic testing after lightning strike on coated CFRP shows no structural delamination and demonstrates the interest of this new route for an efficient LSP

Influence of silver nanowires on thermal and electrical behaviors of a poly(epoxy) coating for aeronautical application

Thermal and electrical behaviors of a poly(epoxy) coating with high electrical conductivity used for aeronautic applications are investigated. The poly(epoxy) used is designed for resin transfer molding (RTM) applications, it have a low viscosity at room temperature (around 1 Pa s) and a high Tg (>160°C). This study details the influence of silver nanowires with a high aspect ratio, on the thermal behavior such as the relative degree of reaction α and the kinetics parameters thanks to dynamic and isothermal differential scanning calorimetry. Conductivity measurements of surface and volume have permitted to determine a very low percolation threshold at around 0.7% in volume. The value of electrical conductivity above the percolation threshold is upper than 102 S m−1 and the lowest surface resistivity was measured around 13 mΩ sq−1 both for 8% in volume of AgNWs. This kind of coating has a great interest for lightning strike protection of aircraft parts due to the high electrical conductivity obtained with a low overweight

Étude du phénomène de percolation électrique dans les composites à matrice polymère pour une application de protection foudre sur structures aéronautiques

L’étude propose la réalisation de composites conducteurs faiblement chargés pour des applications aéronautiques exposées à de forts courants électriques de type foudre. Les fils submicroniques d’argent de haut facteur de forme (250), sont introduits dans une matrice poly(époxy). L’étude de la matrice poly(époxy) par analyse calorimétrique diatherme a validé le choix de la matrice époxy, avec une température de transition vitreuse de 173°C, conforme aux exigences aéronautiques. Les propriétés mécaniques ont été étudiées par analyse mécanique dynamique et ont permis de montrer l’influence de l’humidité ainsi que du rapport stoechiométrique (résine/durcisseur). Il a été mis en évidence que l’humidité et un surplus de durcisseur plastifient le poly(époxy). Puis, les mesures de conductivité électrique effectuées démontrent l’intérêt des charges conductrices à haut facteur de forme au sein de la matrice pour de faible taux de charge

Technical aspects of an impact acceleration traumatic brain injury rat model with potential suitability for both microdialysis and PtiO2 monitoring

This report describes technical adaptations of a traumatic brain injury (TBI) model-largely inspired by Marmarou-in order to monitor microdialysis data and PtiO2 (brain tissue oxygen) before, during and after injury. We particularly focalize on our model requirements which allows us to re-create some drastic pathological characteristics experienced by severely head-injured patients: impact on a closed skull, no ventilation immediately after impact, presence of diffuse axonal injuries and secondary brain insults from systemic origin...We notably give priority to minimize anaesthesia duration in order to tend to banish any neuroprotection. Our new model will henceforth allow a better understanding of neurochemical and biochemical alterations resulting from traumatic brain injury, using microdialysis and PtiO2 techniques already monitored in our Intensive Care Unit. Studies on efficiency and therapeutic window of neuroprotective pharmacological molecules are now conceivable to ameliorate severe head-injury treatment

Dynamic electrical and mechanical properties of epoxy/silver nanowires composites

The aim of this work is to study electrically conductive composites from an epoxy matrix loaded with silver nanowires (AgNWs). Dynamic mechanical analysis (DMA) and dynamic dielectric spectroscopy (DDS) were used to study the molecular mobility of the epoxy matrix and its epoxy/AgNWs composites. The influence of the epoxy/amine ratio on the macroscopic properties was analyzed. The loss modulus of the epoxy matrix highlights two major relaxations, β and α. The β relaxation is due to the localized mobility initiated by hydroxyl groups. The α trelaxation is the anelastic effect liberated at the glass transition. The introduction of a small amount of AgNWs (<8 vol%) has practically no influence on the mechanical properties of the glassy state. For the rubbery state, AgNWs cause an increase in the storage modulus as a function of the filler content. The loss modulus profile is modified: The ω relaxation due to heterogeneities of the 3D network is observed independently from the hydration level of composites. The magnitude of the α mode is increased due to the stick– slip phenomenon. Moreover, it is shifted toward lower temperatures upon the introduction of AgNWs. In other words, the activation enthalpy decreases for both modes. Electrical study through DDS and conductivity measurement of epoxy/AgNWs composites shows the consequence of a lower relative degree of conversion caused by the insertion of AgNWs. Epoxy/AgNWs composites allow us to obtain one of the highest values of the electrical conductivity for polymerbased composites without any drastic evolution of mechanical properties

Etude du métabolisme énergétique des tumeurs cérébrales primitives de haut grade, par microdialyse, chez l'homme

NICE-BU Médecine Odontologie (060882102) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

Exploration du métabolisme tumoral cérébral par microdialyse (étude expérimentale et clinique)

NICE-BU Sciences (060882101) / SudocSudocFranceF

Étude du phénomène de percolation électrique dans les composites à matrice polymère pour une application de protection foudre sur structures aéronautiques

International audienceL’étude propose la réalisation de composites conducteurs faiblement chargés pour des applications aéronautiques exposées à de forts courants électriques de type foudre. Les fils submicroniques d’argent de haut facteur de forme (250), sont introduits dans une matrice poly(époxy). L’étude de la matrice poly(époxy) par analyse calorimétrique diatherme a validé le choix de la matrice époxy, avec une température de transition vitreuse de 173°C, conforme aux exigences aéronautiques. Les propriétés mécaniques ont été étudiées par analyse mécanique dynamique et ont permis de montrer l’influence de l’humidité ainsi que du rapport stoechiométrique (résine/durcisseur). Il a été mis en évidence que l’humidité et un surplus de durcisseur plastifient le poly(époxy). Puis, les mesures de conductivité électrique effectuées démontrent l’intérêt des charges conductrices à haut facteur de forme au sein de la matrice pour de faible taux de charge

Administration of eptifibatide during endovascular treatment of ruptured cerebral aneurysms reduces the rate of thromboembolic events

International audienceIntroduction Thromboembolic complications are the most frequent complications of endovascular treatment of ruptured intracranial aneurysms. The optimal protocol to prevent thromboembolic complications during coil embolization does not yet exist. The aim of this study was to investigate the effectiveness and safety of eptifibatide for the prevention of thromboembolic complications during elective coil emboliza-tion of ruptured cerebral aneurysms. Methods A consecutive series of 100 patients (group 1) with ruptured intracranial aneurysm were treated using endovascular coil embolization. At the beginning of the procedure , all patients received an intra-arterial bolus (0.2 mg/kg) of eptifibatide. The following data were collected: degree of aneurysmal occlusion after treatment, thromboembolic and hemorrhagic complications and other intraoperative adverse events. The results were compared with those from a control group (group 2) which were analyzed retrospectively. Group 2 consisted of 100 previous patients with ruptured aneurysm managed with coil embolization who had received heparin and/or aspirin at the beginning of the procedure. Results (1) Patient populations in groups 1 and 2 were considered statistically comparable, except that group 1 (eptifibatide) included more wide-necked aneurysms (p=0.011). (2) There were less thromboembolic complications in group 1 (p=0.011): seven intraoperative complications in group 1 versus 20 in group 2. (3) Intraoperative hemorrhagic complications were statistically comparable in both groups (p=1). Conclusion Eptifibatide was effective in lowering the intra-operative thromboembolic complication rate in ruptured an-eurysms treated with coil embolization and did not increase the hemorrhagic risk

Prasugrel versus clopidogrel in stent-assisted coil embolization of unruptured intracranial aneurysms

International audienceBackground: Thromboembolic complications are the main problem in stent-assisted coil embolization of unruptured intra-cranial aneurysms. The combination of aspirin and clopidogrel is generally used to decrease these complications, but some patients do not respond to clopidogrel and have a higher risk of stent thrombosis. In cardiology, clinical trials have shown that prasugrel reduced the incidence of ischaemic events in patients with acute coronary syndrome compared with clopidogrel but, according to several authors, prasugrel would produce an increased risk of cerebral haemorrhagic complications.Objective: The purpose of this study was to determine whether prasugrel would be more effective than clopidogrel in reducing procedural events in patients with an unruptured aneurysm treated endovascularly with coils and stent.Materials and methods: Two hundred consecutive patients with intracranial aneurysms were treated using coiling and stenting procedures. The first 100 patients were administered a dual antiplatelet of aspirin and clopidogrel, while the remaining 100 patients were administered a dual antiplatelet of aspirin and prasugrel. In each group data were collected on procedural and periprocedural haemorrhagic and ischaemic complications.Results: Aneurysmal occlusion and haemorrhagic complications rates were identical in both groups. The number of thromboembolic events observed in the two groups of our study did not differ significantly, but the prasugrel group included more wide-neck aneurysms and more flow-diverted stents. Moreover, complications in the prasugrel group were more benign, explaining the significant difference in clinical outcomes between the two groups on Day 30.Conclusions: Prasugrel reduces the clinical consequences of thromboembolic complications of endovascular treatment with stenting and coiling of unruptured intracranial aneurysms