A cohesive zone model for fracture initiation and propagation of fused silica direct bonding interface

International audienceFused silica direct bonding is of particular interest for optical system manufacturing for spatial applications. However, in order to validate the European Space Agency standards, a better understanding of the assemblies mechanical behavior is required. Therefore, it is important to develop some predictive tools to determine numerically mechanical strength of complex assemblies. In this paper, a cohesive zone model is proposed to model the direct bonding interface behavior. In order to determine the mechanical strength of the interface, a propagation test, and an initiation test on a free edge the cleavage test have been performed on direct bonded fused silica samples. The FIT test (Flexible Initiation Test) is also used to identify the properties of the direct bonding joint. At the end, a comparative analyses is proposed between experimental results and finite elements models of the propagation and initiation tests

EFFECT OF DAMAGE ON COMPRESSIVE STRENGTH IN FIBER DIRECTION FOR CFRP

International audienceThe influence of transverse damage on compressive strength in fiber direction for carbon fiber reinforced epoxy materials is investigated by an experimental approach. Several experimental methods are proposed. The first study focuses on tubular samples. Theses samples are damaged by torsional and cyclic load and next submitted to compressive load. Results show that the transverse damage affects the compressive strength. Yet the stiffness is not modified. A model is then proposed with these results. The second study focuses on plates with stress concentrations. A non-local criterion is introduced in order to take the stress concentration into account. Results are in good agreement with the model identified on tubes

A new classification of the Turkish terranes and sutures and its implication for the paleotectonic history of the region

The Turkish part of the Tethyan realm is represented by a series of terranes juxtaposed through Alpine convergent movements and separated by complex suture zones. Different terranes can be defined and characterized by their dominant geological background. The Pontides domain represents a segment of the former active margin of Eurasia, where back-arc basins opened in the Triassic and separated the Sakarya terrane from neighbouring regions. Sakarya was re-accreted to Laurasia through the Balkanic mid-Cretaceous orogenic event that also affected the Rhodope and Strandja zones. The whole region from the Balkans to the Caucasus was then affected by a reversal of subduction and creation of a Late Cretaceous arc before collision with the Anatolian domain in the Eocene. If the Anatolian terrane underwent an evolution similar to Sakarya during the Late Paleozoic and Early Triassic times, both terranes had a diverging history during and after the Eo-Cimmerian collision. North of Sakarya, the Küre back-arc was closed during the Jurassic, whereas north of the Anatolian domain, the back-arc type oceans did not close before the Late Cretaceous. During the Cretaceous, both domains were affected by ophiolite obduction, but in very different ways: north directed diachronous Middle to Late Cretaceous mélange obduction on the Jurassic Sakarya passive margin; Senonian synchronous southward obduction on the Triassic passive margin of Anatolia. From this, it appears that the Izmir-Ankara suture, currently separating both terranes, is composite, and that the passive margin of Sakarya is not the conjugate margin of Anatolia. To the south, the Cimmerian Taurus domain together with the Beydağları domain (part of the larger Greater Apulian terrane), were detached from north Gondwana in the Permian during the opening of the Neotethys (East-Mediterranean basin). The drifting Cimmerian blocks entered into a soft collision with the Anatolian and related terranes in the Eo-Cimmerian orogenic phase (Late Triassic), thus suturing the Paleotethys. At that time, the Taurus plate developed foreland-type basins, filled with flysch-molasse deposits that locally overstepped the lower plate Taurus terrane and were deposited in the opening Neotethys to the south. These olistostromal deposits are characterized by pelagic Carboniferous and Permian material from the Paleotethys suture zone found in the Mersin mélange. The latter, as well as the Antalya and Mamonia domains are represented by a series of exotic units now found south of the main Taurus range. Part of the Mersin exotic material was clearly derived from the former north Anatolian passive margin (Huğlu-type series) and re-displaced during the Paleogene. This led us to propose a plate tectonic model where the Anatolian ophiolitic front is linked up with the Samail/Baër-Bassit obduction front found along the Arabian margin. The obduction front was indented by the Anatolian promontory whose eastern end was partially subducted. Continued slab roll-back of the Neotethys allowed Anatolian exotics to continue their course southwestward until their emplacement along the Taurus southern margin (Mersin) and up to the Beydağları promontory (Antaya-Mamonia) in the latest Cretaceous-Paleocene. The supra-subduction ocean opening at the back of the obduction front (Troodos-type Ocean) was finally closed by Eocene north-south shortening between Africa and Eurasia. This brought close to each other Cretaceous ophiolites derived from the north of Anatolia and those obducted on the Arabian promontory. The latter were sealed by a Maastrichtian platform, and locally never affected by Alpine tectonism, whereas those located on the eastern Anatolian plate are strongly deformed and metamorphosed, and affected by Eocene arc magmatism. These observations help to reconstruct the larger frame of the central Tethyan realm geodynamic evolution

Das untere Paläozoikum in Iberia - eine plattentektonische Interpretation

10 páginas.[EN] The present-day distribution of the Ossa-Morena, Central Iberian, West Asturian-Leonese, and Cantabrian tectono-metamorphic Zones resulted from the complex Variscan evolution, juxtaposing along the Eurasian margin domains formerly located at the Gondwana margin in Early Palaeozoic times. Characterized by mainly thick detrital Cambrian and/or Ordovician sediments, all four regions with their different sedimentary evolution indicate specific emplacements along the Gondwana margin. The elaboration of tectonic subsidence curves for each region and their comparison during the Cambrian, result in a time-space relationship characterized by the following stages: Late Proterozoic to Early Cambrian Cadomian active margin setting (Ossa-Morena and Central Iberian Zones), potential accretion to Gondwana; since the Early Cambrian extending continental crust, leading to an initial subsidence in the Ossa-Morena Zone and to a strong subsidence in the West Asturian-Leonese Zone lasting until the Late Cambrian, related to the opening of the Prototethys. A new pulse of subsidence is recorded since the Arenigian, during the deposition of the "Armorican Quartzite" in the Central Iberian Zone, which is thought to represent a rim-basin forming behind the shoulder of the opening Rheic Ocean. The moderate subsidence in the Cantabrian Zone could be the expression of its evolution of a hinterland between the two passive margins.[ES] La distribución actual de las Zonas tectonometamórficas Cantábrica, Asturoccidental-Leonesa, Centroibérica y Ossa-Morena es el resultado de una compleja evolución que yuxtapuso, durante la deformación varisca, dominios emplazados en distintos lugares del margen de Gondwana durante el Paleozoico Inferior. La diferente evolución sedimentaria de estas cuatro regiones, caracterizadas principalmente por su potente sedimentación detrítica durante el Cámbrico-Ordovícico, indica un emplazamiento específico para cada una de ellas dentro del margen gondwánico. La reconstrucción de las curvas de subsidencia tectónica de cada zona y su comparación den-tro del marco de la evolución cambro-ordovícica perigondwánica, permite distinguir varias etapas en sus relaciones espacio-temporales. Así, en la primera (Neoproterozoico-Cámbrico inicial), un margen activo sobre corteza de tipo cadomiense se desarrollaba en la periferia de Gondwana (Zonas de Ossa-Morena y Centroibérica). La segunda etapa supuso la extensión de dicha corteza entre el Cámbrico Inferior a Superior, con subsidencia incipiente en Ossa-Morena, y fuerte subsidencia en la Zona Asturoccidental-Leonesa. Finalmente y a partir del Arenigiense, se registra un nuevo pulso subsidente en la Zona Centroibérica, ligado al depósito de la Cuarcita Armoricana, lo que permite interpretarla como una cuenca marginal (rim basin) a espaldas del borde sobreelevado (shoulder) creado en la apertura del Océano Rheico. La subsidencia moderada durante esta época en la Zona Cantábrica puede ser el resultado de su evolución como un traspaís (hinterland) situado entre dos márgenes pasivos.[DE] Die heutige Zonengliederung des Iberischen Massivs in die Südportugiesische, Ossa-Morena, Zentraliberische, Westasturisch-Leonesische und Kantabrische Zone ist Folge einer komplexen variszischen Entwicklung, die verschiedene frühpaläozoische Kontinentaleinheiten des ehemaligen Gondwanarandes am Südrand von Eurasien zusammenführte. Durch eine mächtige detritische Entwicklung während des Kambriums und Ordoviziums charakterisiert, zeigen alle der vier letztgenannten Blöcke unterschiedliche Sedimentationsbedingungen und damit unterschiedliche Ablagerungsbedingungen am Gondwanarand an. Die Sedimentation ist in allen vier Gebieten durch spezifische tektonische Subsidenzkurven charakterisiert, und es lassen sich für die Zeit des Kambriums und Ordoviziums folgende plattentektonische Entwicklungsabschnitte unterscheiden: neoproterozoisch bis frühkambrischer aktiver Plattenrand (Ossa-Morena und Zentraliberische Zonen) und mögliche Akkretion an den Gondwanarand; seit dem Unterkambrium Dehnung der kontinentalen Kruste mit initialer Subsidenz in der OssaMorena Zone, und mit starker Subsidenz im Bereich der Westasturisch-Leonesischen Zone bis zum oberen Kambrium im Zusammenhang mit der Öffnung der Prototethys. Mit der Ablagerung des Armorikanischen Quarzits seit dem Arenig wird in der Zentraliberischen Zone eine neue Subsidenzphase erkennbar, die auf eine ,,Rim-Basin Situation hinter der Riftschulter des sich öffnenden Rheischen Ozeans gedeutet werden kann. Die relativ geringen Subsidenzraten in der Kantabrischen Zone könnten Ausdruck einer Entwicklung zwischen zwei passiven Rändern im Hinterland des Riftsystems sein.Peer reviewe