In-situ measurements of temperature distribution during transmission laser welding of poly(aryletherketone)

In this work, the temperature distribution inside the specimens has been measured during transmission laser welding. The material studied is a high performance thermoplastic of the polyaryletherketone (PAEK) family. The assembly consists of a quasi-amorphous sample as the upper part and a semi-crystalline sample as the lower part. The temperature fields were measured by infrared thermography with the camera sensor perpendicular to the welded interface. With an energy beam of 28 J.mm-2 and irradiation time of 15s, we have noticed that the maximum temperature inside the sample is kept far from the PAEK degradation one. Moreover, the temperature at the interface reaches the melting temperature thus assuring enough mobility for polymeric chains to get adhesion at the interface. Finally, the location and size of the heat-affected zone (HAZ) has been determined

Emulsion models and rheology of filled polymers

cited By 20International audienceThe rheological behavior of narrow polybutadiene samples filled with rigid silica spheres has been investigated. Generally the rheological behavior of biphasic blends of polymers can be interpretated in terms of emulsion models when the concentration of the dispersed phase is low enough so as to avoid interparticle interactions. The main feature is the presence of a relaxation domain which appears in the low frequency zone of the complex shear modulus. The most general emulsion model proposed by Palierne [Palierne, J. F., Rheologica Acta, 1991, 30, 497.] explains that occurrence by the shape relaxation of the viscoelastic dispersed phase. But the model fails when the dispersed phase is very little deformable or non deformable (mineral fillers). Nevertheless a slow relaxation process is also seen experimentally in that case which can not be assumed due to shape relaxation. Those slow relaxation processes were measured and analyzed as a function of polybutadiene molecular weight and size and volume concentration of the silica spheres. They have been interpretated by an adsorption of polybutadiene chains on the silica surface that creates a monomolecular layer whose thickness is comparable to the bulk radius of gyration of the chains and whose relaxation time scales in the same way as branches of star polymers. © 1998 Elsevier Science Ltd. All rights reserved

Le test couronne pour la mesure de l'adhérence substrat-adhésif

Cet article est dédié à la présentation d'un test mécanique de rupture, adapté à la mesure de l'adhérence entre un substrat et un adhésif structural. L'assemblage collé testé a une géométrie axisymétrique. Il est constitué d'un substrat cylindrique central entouré d'une couronne d'adhésif épaisse moulée autour du substrat. Pendant le test, la couronne d'adhésif est en appui sur la traverse fixe de la machine d'essais et la traverse mobile pousse le substrat central vers le bas, le long de son axe de révolution, jusqu'à la rupture provoquant la séparation du substrat et de l'adhésif. Ces conditions expérimentales ont été modélisées, en utilisant le code de calcul ANSYS 11.0, afin d'évaluer la distribution des contraintes dans l'assemblage sous charge. Le résultat le plus important de cette modélisation est l'extrême concentration des valeurs maximales positives des contraintes principales, dans une zone annulaire interfaciale cylindre-couronne, au bord libre de la partie inférieure de la couronne d'adhésif. C'est dans cette zone qu'a lieu l'initiation des ruptures provoquées par un cisaillement et une ouverture de l'interface. Dans ces conditions, des ruptures interfaciales sont attendues, ce qui a été vérifié par les résultats expérimentaux avec, de plus, des faibles valeurs de la charge à la rupture. Avec un tel comportement mécanique, le test couronne est un outil efficace pour évaluer l'adhérence entre un substrat et un adhésif structural

Thermorheological behavior of polypropylene and polycarbonate inclusions in an ethylene copolymer matrix

cited By 9International audienceWe investigated the rheological behavior of incompatible polymer blends made of a semicrystalline ethylene-methyl acrylate (EMA) matrix and two different species of inclusions - a semicrystalline polypropylene and an amorphous polycarbonate. The emulsion model of Palierne which describes the linear viscoelastic behavior of incompatible blends of polymers was applied to both polymer blends at temperatures below and above the melt or glass temperature of the dispersed polymer. The Palierne model fits well the experimental results for temperatures above the transition temperatures of the minor phases. When the dispersed phase is rigid, the fit is good all over the frequency range for the blend of EMA/polypropylene (PP), whereas a noticeable deviation occurs at low frequencies for the EMA/polycarbonate (PC). That behavior is explained by strong van der Waals interactions between EMA and PC molecules, which creates a layer of EMA chains irreversibly adsorbed onto the PC surface. © 1997 John Wiley & Sons, Inc

Reversible/irreversible networks formation in thermally removable adhesive

International audienc

Reversible/irreversible networks formation in thermally removable adhesive

International audienc

The power to pardon in late medieval and early modern Europe: New perspectives in the history of crime and criminal justice

Over the past 30 years, few sources have been the subject of more scholarly attention than medieval and early modern pardon letters. These charters, issued by the royal or princely chancery in response to a petition addressed to the monarch and his council, were the strongest manifestation of the sovereign's right to remit crimes in many European polities, including France, England, the Low Countries, Castile, and Portugal. Following the paradigmatic interpretation of ordinary violence as the expression of well‐integrated social behaviours, historians of crime and criminal justice have found in petitions and pardon letters records of powerful narratives describing episodes of violence in the population's everyday life. Yet scholars have also debated the reliability of these stories, as they were obviously designed to support the petitioners' claim for pardon. Another major historiographical controversy concerns the articulation between the power to pardon and the criminal policies of the monarchs. While some historians considered the granting of pardon letters as the product of a weak or corrupted justice system that preferred to remit crimes in exchange for money rather prosecuting the perpetrators, others argued that the rise of the power to pardon followed the process of early modern State‐building and served to temper criminal prosecutions and assert the sovereign's right over the life and death of his subjects. This essay introduces the reader to the historiography of pardon letters and shows its connections with the recent developments in the history of crime and criminal justice in late medieval and early modern Europe