Fatigue crack growth in thin notched woven glass composites under tensile loading. Part I: experimental

Helicopter blades are made of composite materials mainly loaded in fatigue and have normally relatively thin skins. A through-the-thickness crack could appear in these skins. The aim of this study is to characterize the through-the-thickness crack propagation due to fatigue in thin woven glass fabric laminates. A technological test specimen is developed to get closer to the real loading conditions acting on these structures. An experimental campaign is undertaken which allows evaluating crack growth rates in several laminates. The crack path is linked through microscopic investigations to specify damage in woven plies. Crack initiation duration influence on experimental results is also underlined

Influence of woven ply degradation on fatigue crack growth in thin notched composites under tensile loading

This paper deals with the fatigue of the through the-thickness crack propagation in thin notched composite laminates made of two glass woven plies. It highlights the different crack growths between warp and weft directions of the woven ply. Experimental results show a decrease of the crack growth rate per cycle with the increase of the crack initiation time. Moreover, it has been shown that it is necessary to take into account the fatigue damage of the woven plies in term of loss of rigidity in the initiation phase. The fatigue crack growth rates are then quantified using Paris law type equations and linear elastic fracture mechanics (LEFM)

Fatigue crack growth in thin notched woven glass composites under tensile loading. Part II: modelling

Fatigue propagation of a through-the-thickness crack in thin woven glass laminates is difficult to model when using homogeneous material assumption. Crack growth depends on both the fatigue behaviour of the fibres and of the matrix, these two phenomena occurring at different time and space scales. The developed finite element model is based on the architecture of the fabric and on the fatigue behaviours of the matrix and the fibre, even if the pure resin and fibre behaviours are not used. That thus limits the physical meaning of this model. Basically, the objective of this simulation is to illustrate and to confirm proposed crack growth mechanism. The fatigue damage matrix is introduced with user spring elements that link the two fibre directions of the fabric. Fibre fatigue behaviour is based on the S-N curves. Numerical results are compared to experimental crack growth rates and observed damage in the crack tip. Relatively good agreement between predictions and experiments was found

Sous le regard de l’autre. Transmission des pratiques musicales en Haut-Ossau (Béarn)

During the 19th century in the Bearnese Pyrenees, the Ossau Valley became a centre of European spa tourism. For two centuries, musical practices and community rituals have been a part of the tourism experience there. Throughout this history, which shifts from a monumental regime to a patrimonial regime, the asymmetrical relationship between visitor and visited, between demand and local supply, is reversed. The valorizing external view that favoured the transmission of practices over time has given way to an ambiguous relationship: the visited oscillating between traditional desires and a duty to “implement a heritage.”Dans les Pyrénées béarnaises, la vallée d’Ossau devient au xixe siècle un haut lieu du tourisme thermal européen. Durant deux siècles, pratiques musicales et rituels communautaires participent d’une mise en tourisme. Au long de cette histoire qui voit le passage d’un régime monumental à un régime patrimonial, la relation asymétrique entre visiteur et visité, entre demande et offre locale, s’inverse. Le regard extérieur valorisant qui a favorisé la transmission des pratiques dans la durée cède la place à une relation ambiguë, le visité oscillant entre désir de ce regard et devoir de « mettre en oeuvre un patrimoine »

Bibliographie neuchâteloise

Analyse: Bibliographie rétrospective des origines à mars 1990, recensant 2723 titres

Fragmentation, regroupement et remembrement (du milieu du XIXe siècle à nos jours)

Le 25e colloque de l'ARF se déroulera du 24 au 26 octobre dans les locaux du Musée maritime de l'île de Tatihou, commune de Saint-Vaast-la-Hougue. Nous ne publions qu'un programme provisoire, annonçant la plupart des communications classées selon l'ordre alphabétique des patronymes des intervenants. Le programme définitif sera adressé à chaque communicant et aux membres de l'Association des ruralistes français , il sera également « mis en ligne » sur le site internet de Ruralia (http:/..