Modeling and Optimization of Materials and Structures

Preface : The current economic and ecological context requires different industries towards the optimization of structures. One of the most striking examples is the soaring price of oil, which launched the major aircraft manufacturers Airbus and Boeing in a race to relief structures, to reduce their consumption. Therefore, the need of competitive products, both in terms of reliability, performance or operating cost, is pervasive and growing, aviation and elsewhere. Thus, work on the material parts by offering innovative solutions to reduce their weight and improve their performance (new materials, new processes, etc.) is essential and becomes more than ever a major industrial challenge. One way of increasing the selected aircraft is use of composite materials. Indeed, their high ratio mechanical / density properties and excellent resistance to environmental significantly improve the structural performance of the aircraft while generating a significant weight gain (20 to 30% weight of a structure). They were originally implemented in the design of secondary structures of aircraft, but improving their manufacturing processes and a better understanding of their mechanical properties and their degradation mechanisms are they now used for the manufacture of primary structures, such as the fuselage or the central box of an aircraft wing. If applications were rather the military origin, composites now particularly interested in civil aviation, the constraints are much stricter certification, which requires predictability of behavior and life of structures much finer Thus, at present, they account for over 50% of the mass of newer aircraft such as the Airbus A350, the Airbus A380 or the Boeing 787. The potential of composite materials is important, but will speak only on one condition: work not only on the basic constituents of the material (fibers, resin, ...) on the injection preparation conditions (methods, thermal cycle, shaped in the mold, ...) but also and above all on the function of the material in the structure. Indeed, the aterial is a component of a more complex system, consisting of parts, assemblies, subassemblies and the structure itself. This vision system involves understanding the material as parameters, not data, an overall optimization of the structure. This link between material and structure is evident for composites where fiber orientation, or reinforcements in a more general way, in the direction of efforts can greatly increase the performance / weight ratio. We understand that optimizing the structure requires, among other things, a design material to locally respond to the "just need" structural. The main objectives of this special issue (consisting mainly of a selection of papers presented at 5th International Symposium on AirCraft MAterials ACMA 2014) are, by means of modeling strategies and simulation out with conventional strategies, pushing the current limits in modeling and computation in response industrial and societal challenges. It is also to control the calculations and models in a framework that takes into account the major sources of uncertainty to optimize materials and structures. Particular attention is made to the modeling and validation of composite materials and structures

Les Bivalves néogènes du Maroc septentrional (façades atlantique et méditerranéenne). Biostratigraphie, paléobiogéographie et paléoécologie

Thirty seven sections are described in the neogene formations of Western and Eastern parts of Northern Morocco. They represent three sedimentary cycles (Tortonian, Messinian and Pliocene). Fifty nine outcrops of variable facies have been prospected. The 59 deposits gave a rich and varied Bivalvia fauna. One hundred and forty species have been recognized and they belong to thirty three families. The number of families and species is more important in the Pliocene. The stratigraphical distribution of the species shows that the 3 sedimentary cycles which they come from, are characterized by either dominance or exclusivity of some of these species. The geographical distribution of the Bivalvia during the Neogene indicates their atlantic origin during the Lower Miocene, then a migration towards the Alboran Sea during the later Miocene and finally a restocking during the Pliocene from the Alboran Sea and the Atlantic to the Mediterranean. The assemblages of the Bivalvia - generally well kept - correspond to suboriginal taphocoenoses. The Bivalvia give indications about the environment during the three cycles : salinity is normal except at the end of Messinian ; generally the depth corresponds to the infralittoral stage ; the hydrodynamics is rather high in the Upper Miocene and weak in the Pliocene ; the temperature is subtropical in the Late Miocene but becomes cooler in the lower Pliocene.Dans les formations néogènes des secteurs occidental et oriental du Maroc septentrional, 37 coupes sont décrites ; elles représentent trois cycles sédimentaires (Tortonien, Messinien et Pliocène) et livrent 59 gisements de faciès variables. Les 59 gisements ont fourni une faune riche et diversifiée : 140 espèces sont reconnues et appartiennent à 33 familles. Le nombre de familles et d'espèces est plus important au Pliocène. La répartition stratigraphique des espèces montre que les trois cycles sédimentaires dont elles proviennent se caractérisent par la dominance ou l'exclusivité de certaines de ces espèces. La répartition géographique des Bivalves durant le Néogène permet de mettre en évidence l'origine atlantique au Miocène inférieur, une migration des espèces vers la mer d'Alboran au Miocène supérieur et enfin un repeuplement de la Méditerranée à partir de cette mer et de l'Atlantique au Pliocène. Généralement bien conservés, les assemblages de Bivalves correspondent à des taphocénoses subautochtones. Ces Bivalves ont permis d'indiquer les conditions du milieu durant les trois cycles ; à l'exception de la dégradation vers le sommet du Messinien, la salinité est normale pendant les trois cycles ; la profondeur est généralement celle de l'étage infralittoral ; l'hydrodynamisme est assez élevé au Miocène supérieur et relativement faible au Pliocène ; la température est de type subtropical au Miocène supérieur et moins chaude au Pliocène.Ben Moussa Abdelkhalak. Les Bivalves néogènes du Maroc septentrional (façades atlantique et méditerranéenne). Biostratigraphie, paléobiogéographie et paléoécologie. In: Documents des Laboratoires de Géologie, Lyon, n°132, 1994. Les Bivalves néogènes du Maroc septentrional (façades atlantique et méditerranéenne). Biostratigraphie, paléobiogéographie et paléoécologie. pp. 3-281

Les associations de foraminifères benthiques des séries marno-diatomitiques messiniennes du bassin de Nador-Melilla (Maroc nord-oriental)

Benthic foraminiferal associations from messinian marly-diatomeous series in the Nador-Melilla basin (North eastern Morocco). The study of the benthic foraminiferal of the three sampled marly diatomeous series of the Nador-Melilla (north eastern Morocco) allows to identify 97 species, dominated especially by Bolivinidae and Buliminidae. The qualitative and quantitative analysis of this microfauna reveals a paleoenvironment with low oxygen concentrations and rich in nutrients in the bottom waters, linked to the functioning of upwellings. It is characterized by a low microfaunal diversity and a weak pelagism index, and by the dominance of Bolivinidae (Bolivina spathulata, B. dentellata, B. dilatata) and Buliminidae (Bulimina aculeata, B. elongata, B. echinata). This paleoenvironment is disturbed by periods of reoxigenation characterized by pelagism index and benthic foraminifera diversity relatively raised and sometimes by the abundant presence of the bivalve Neopycnodonta navicularis.L'étude des foraminifêres benthiques des trois séries de marnes diatomitiques messiniennes du bassin de Nador-Melilla (Maroc nord-oriental) permet d'identifier 97 espèces, dominées par les Bolivinidae et les Buliminidae. L'analyse quantitative et qualitative de cette microfaune révèle un paléoenvironnement à faible teneur d'oxygène des eaux et riche en éléments nutritifs, lié au fonctionnement des upwellings. Il est caractérisé par une diversité et par un indice de pélagisme faibles et par la dominance des Bolivinidae (Bolivina spathulata, B. dentellata, B. dilatata) et des Buliminidae (Bulimina aculeata, B. elongata, B. echinata ). Ce paléoenvironnement est perturbé par des périodes de réoxygénation marquées par une diversité et par un indice de pélagisme relativement élevés et parfois par l'abondance du bivalve Neopycnodonta navicularis.Rachid Abdellah, El Hajjaji Khalil, Ben Moussa Abdelkhalak. Les associations de foraminifères benthiques des séries marno-diatomitiques messiniennes du bassin de Nador-Melilla (Maroc nord-oriental). In: Géologie Méditerranéenne. Tome 24, numéro 1-2, 1997. pp. 29-49

Indicators in risk management: Are they a user-friendly interface between natural hazards and societal responses? Challenges and opportunities after UN Sendai conference in 2015

Risk management indicators are used to mitigate the potentially dramatic effects of natural hazards. Local authorities and managers use them in elaborating rescue and urbanism plans, which do not always work, highlighting society's vulnerability in the particular context of global environmental and climate changes. Within this context, the United Nations (Sendai, 2015) advised to construct a series of indicators to better cope with human losses and economic disasters. Actually, the question is whether or not such indicators do constitute successful decision-making tools. In this article, we critically reviewed the recent literature (from 2013 to 2017) using the Web of Science database of Clarivate Analytics to assess how indicators are currently being constructed in risk management, with a focus on risks of inundations, coastal and seismic risks. This task allowed us to discuss the spatial and temporal scale at which indicators of risk management can be applicable, to what extent they should be physically oriented and if they can fit the needs of governance framework. Based on our findings, we suggest further work on a new series of less descriptive, more dynamic and more user-friendly indicators. Finally, we encourage the dire need for continuous work to overcome the misinterpretation of used indicators and how to reduce the communication gap between the scientific community, decision makers, managers and the population

Local Risk Awareness and Precautionary Behaviour in a Multi-Hazard Region of North Morocco

International audienceNorth Morocco (region Tangier-Tetouan-Al Hoceima) is characterized by high demographic and economic pressures, which intensify the vulnerability of the coastal areas. Morocco lies both along the Atlantic and the Mediterranean coast, having a rich relief of mountain chains (Atlas and Rif). This diverse context induces the challenge of adapting to environments that are drastically different, and of answering the question to which extent the local population is aware of different natural risks. Risk awareness is addressed as a predictor of precautionary behaviour in a questionnaire-based survey. Here the variables explaining the readiness of inhabitants to protect themselves and their belongings from natural risks in the present and the willingness to invest and to protect in the future are explored. Furthermore, based on the different response patterns in the survey, we used multiple correspondence analysis to identify profiles of typical dwellers. The results indicate local regional differences, where the Rif Mountain dwellers are more prone to protect themselves than the ones living in other parts of North Morocco. Finally, environmental identity indicates that the relationship with nature has an impact on risk awareness and precautionary behaviour. This study brings out information which could be useful for policy makers who should promote ecological concerns and encourage local action in resolving environmental issues when promoting risk mitigation measures

Les bryozoarites du Miocène supérieur du bassin de Charf el Akab (Maroc nord occidental) : sédimentologie et paléoenvironnements

The Upper Miocene bryozoarites of Charf el Akab (NW of Morocco) and their sedimentary environments. The high concentration of bryozoan skeletons in the Upper Miocene carbonate deposits of Charf el Akab allows to propose a new termination for this type of sediment : the bryozoarites where the fragmentai remains of bryozoan colonies are the dominant contributor, they could constitute up to 80 % of the bioclastic content. The textural and paleoecological analysis of these formation indicates two types : 1 -Massive bryozoarites where encrusting bryozoans especially celleporiforms are predominant. 2 -Bedded bryozoarites formed by interbedding of sandy levels and bioclastic beds where erect, flexible bryozoan (cellariiform) are dominant. The sedimentological and paleoecological studies underline wave-dominated ramp or platform setting sedimentation of massive bryozoarites. Bedded bryozoarites reflect tidal control during the filling of the basin. The quantitative analysis of bryozoan zoarial forms suggests that the paleodepth range decreases from -30 to -70 meters for the massive bryozoarites to -5 -1 5 m during the deposition. The presence of the genus Metrarabdotos seems indicate that Upper Miocene water was warmer than present Atlantic Ocean.Les roches carbonatées du Miocène supérieur de Charf el Akab (Maroc nord-occidental) comportent une concentration remarquable de restes de bryozoaires. Le terme de bryozoarite est proposé pour qualifier une biocalcarénite de texture rudstone à grainstone dont la fraction biogène est dominée par les bryozoaires, ceux-ci pouvant représenter jusqu'à 80 % du contenu bioclastique, le ciment étant cal-citique. L'étude texturale et paléoécologique de ces roches permet de distinguer deux types de faciès : 1 -les bryozoarites massives constituées principalement de bryozoaires encroûtants, massifs appartenant au groupe des cellépori-formes ; 2 -les bryozoarites litées formées par une alternance de niveaux bioclastiques à bryozoaires surtout érigés flexibles et de lits quartzeux. La succession lithologique de ces deux faciès met en évidence une sédimentation dominée par l'action de la houle en domaine de rampe subsidente pour les bryozoarites massives, et du comblement du bassin sous le contrôle des marées pour le dépôt des bryozoarites litées. L'étude paléoécologique quantitative des formes zoariales des bryozoaires indique des paléoprofondeurs s'étageant de -30 à -70 m au début de la sédimentation, jusqu'à -5 -15 m vers la fin du fonctionnement du bassin. La présence du genre Metrarabdotos indique une température des eaux plus élevée que celle de l'Atlantique actuel.Lamarti-Sefian N., Pouyet Simone, El Hajjaji Khalil, André Jean-Pierre, Ben Moussa Abdelkhalak. Les bryozoarites du Miocène supérieur du bassin de Charf el Akab (Maroc nord occidental) : sédimentologie et paléoenvironnements. In: Géologie Méditerranéenne. Tome 24, numéro 3-4, 1997. pp. 161-173

Sedimentology and sequence stratigraphy of the late-Messinian - Early pliocene continental to marine deposits of the Boudinar basin (North Morocco)

International audienceDuring the Messinian Salinity Crisis (MSC), between 5.97 and 5.33 Ma, the marine connections between the Atlantic Ocean and the Mediterranean Sea were temporarily restricted. The post-MSC reflooding of the Mediterranean Sea by the Atlantic waters and its sedimentary record are debated. The Boudinar basin (North-Morocco) provides an exceptional record of this period between ca 5.32–5.27 and 4.37 Ma at youngest (Zanclean - Zone PL1). The sedimentary succession of this basin comprises seven facies associations corresponding to depositional settings ranging from continental to open marine environments.We provide a new sequence stratigraphic framework, based on twelve stratigraphic sections. Two orders of depositional sequences (4th, 3rd order), related to base-level changes during the Late-Messinian Early-Pliocene time interval, are correlated at the basin scale. According to our reconstruction, the post-MSC base level rise and the Zanclean reflooding lasted from a minimum of several tens up to hundreds thousands years, suggesting a gradual, not catastrophic event indicative of a progressive transgression

Response to the comment by A. Salhi (2020) regarding the published article ’Local Risk Awareness and Precautionary Behaviour in a Multi-Hazard Region of North Morocco.’

International audienceIn a comment on our manuscript recently published in this journal (Ivčević et al., 2020) [1], Salhi (2020) raises concerns about the manuscript and the study on which it was based, concluding that ‘the article provides a distorted picture of the reality in the study area’. The points raised by the comment are mainly dealing with the literature review and methodological issues related with sampling, and finally little on the content and the results

L'ichtyofaune messinienne à la périphérie de la plate-forme carbonatée de Melilla-Nador (Nord-Est du Maroc)

Messinian fish-fauna from the periphery of the Melilla-Nador carbonate platform (Northeastern Morocco). Fossil fishes have been found in three Messinian outcrops of the Melilla-Nador basin (Morocco), in distal sediments interpreted as coeval with some of the carbonate platform units. Two of them have yielded the same two species of Clupeids, one of them belonging to the genus Sardina ANTEPA. The third outcrop has mainly produced fragments of young Bregmaceros and isolated scales of Clupeids. The Messinian fish-fauna of the Melilla-Nador basin is characterized by its oligospecificity which is probably the consequence of a relative geographical isolation of this basin. Moreover, the identified species are indicative of a shallow marine environmentDes poissons fossiles ont été récoltés dans le Messinien en trois points du bassin de Melilla-Nador (Maroc) dans des sédiments représentant l'équivalent distal d'unités de plate-forme carbonatée. Deux d'entre eux ont livré uniquement les deux mêmes espèces de Gupeidae, dont l'une au moins appartient au genre Sardina ANTIPA. Le troisième affleurement a produit principalement des fragments de jeunes Bregmaceros et des écailles isolées de Clupeidae. L'ichthyofaune messinienne du bassin de Melilla-Nador est caractérisée par son oligospécificité qui est probablement la conséquence d'un relatif isolement géographique de ce bassin. En outre, les espèces identifiées témoignent d'un environnement marin de faible profondeur.Gaudant Jean, Saint Martin Jean-Paul, Benmoussa A., Cornée Jean-Jacques, El Hajjaji Khalil, Muller J. L'ichtyofaune messinienne à la périphérie de la plate-forme carbonatée de Melilla-Nador (Nord-Est du Maroc). In: Géologie Méditerranéenne. Tome 21, numéro 1-2, 1994. Récifs et plates-formes carbonatées miocènes de Méditerranée / Miocene reefs and carbonate platforms of the Mediterranean. Interim colloquium R.C.M.N.S. (Marseille 3-6 mai 1994) sous la direction de Jean-Paul Saint-Martin et Jean-Jacques Cornée. pp. 25-35

Direct dating of brittle extensional deformation in the internal zones of the Rif Chain

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