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

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

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)

Vibration damping in polygonal plates using the acoustic black hole effect : model based on the image source method

A method for damping flexural vibrations in thin polygonal plates using the acoustic black hole effect is proposed. Acoustic black holes in thin plates consist of a zone of decreasing thickness in which flexural waves slow down, acting as wave sinks. An acoustic black hole of axisymmetric thickness profile is here tested on different polygonal plates. A parabolic edge is added in order to focus waves into the black hole area. The experimental results show significant reduction of the vibration level. A model based on the image source method provides qualitative agreement with the experiments

Modélisation de panneaux multicouches composés de matériaux poro-élastiques anisotropes par méthodes d'ondes planes

L'anisotropie des propriétés mécaniques et acoustiques des matériaux poro-élastiques est un facteur déterminant dans le comportement de panneaux multicouches utilisés dans différents domaines de l'ingénierie. La compréhension des différents mécanismes physiques conditionnant la réponse en fréquence de ces structures est alors nécessaire. En particulier, l'anisotropie intrinsèque des matériaux poreux visco-élastiques présente un potentiel pour l'optimisation multi-fonctionnelle de parois multicouches. En effet, ces parois doivent souvent respecter des contraintes de poids, de raideur et isolation sonore et thermique de manière simultanée. Une méthode par superposition d'ondes planes dans des parois composées de matériaux poro-visco-élastiques est présentée afin d'analyser la sensibilité de la réponse acoustique de structures multicouches à l'alignement relatif des couches poreuses anisotropes dans celles-ci. La méthode est validée et appliquée au cas d'une mousse de mélamine située entre deux parois métalliques

Цеховой устав виленских кушниров как источник организации норм морали среди ремесленников середины XVI века

Материалы VI Междунар. науч. конф. студентов, аспирантов и молодых ученых, Гомель, 26 апр. 2013 г. / М-во образования Респ. Беларусь, Гомел. гос. техн. ун-т им. П. О. Сухого; под общ. ред. В. В. Кириенко. – Гомель: ГГТУ им. П. О. Сухого, 2013

Propagation de coupure dans des tissus de verre de pâles arrières d'hélicoptères

L'objet de ce travail est l'étude de la propagation de coupure en fatigue dans des tissus composites de verre/époxy utilisés pour la fabrication de pâles arrières d'hélicoptères par la société EUROCOPTER. Une étude des directions chaîne et trame du tissu a été menée et a montré une différence de comportement importante sur la vitesse de propagation d'une coupure; en particulier le temps d'initiation dans la direction trame s'est révélé près de 10 fois plus important que celui de la chaine

Real-time sound synthesis of pass-by noise: comparison of spherical harmonics and time-varying filters

This paper proposes and compares two sound synthesis techniques to render a moving source for a fixed receiver position based on indoor pass-by noise measurements. The approaches are based on the time-varying infinite impulse response (IIR) filtering and spherical harmonics (SH) representation. The central contribution of the work is a framework for realistic moving source sound synthesis based on transfer functions measured using static far-field microphone arrays. While the SHs require a circular microphone array and a free-field propagation (delay, geometric spread), the IIR filtering relies on far-field microphones that correspond to the propagation path of the moving source. Both frameworks aim to provide accurate sound pressure levels in the far-field that comply with standards. Moreover, the frameworks can be extended to additional sources and filters (e.g. sound barriers) to create different moving source scenarios by removing the room size constraint. The results of the two sound synthesis approaches are preliminary evaluated and compared on a vehicle pass-by noise dataset and it is shown that both approaches are capable of accurately and efficiently synthesize a moving source

Observation of Orbitally Excited B_s Mesons

We report the first observation of two narrow resonances consistent with states of orbitally excited (L=1) B_s mesons using 1 fb^{-1} of ppbar collisions at sqrt{s} = 1.96 TeV collected with the CDF II detector at the Fermilab Tevatron. We use two-body decays into K^- and B^+ mesons reconstructed as B^+ \to J/\psi K^+, J/\psi \to \mu^+ \mu^- or B^+ \to \bar{D}^0 \pi^+, \bar{D}^0 \to K^+ \pi^-. We deduce the masses of the two states to be m(B_{s1}) = 5829.4 +- 0.7 MeV/c^2 and m(B_{s2}^*) = 5839.7 +- 0.7 MeV/c^2.Comment: Version accepted and published by Phys. Rev. Let

Designed Metal-ATCUN Derivatives: Redox- and Non-redox-Based Applications Relevant for Chemistry, Biology, and Medicine

UID/QUI/50006/2019The designed "ATCUN'' motif (amino-terminal copper and nickel binding site) is a replica of naturally occurring ATCUN site found in many proteins/peptides, and an attractive platform for multiple applications, which include nucleases, proteases, spectroscopic probes, imaging, and small molecule activation. ATCUN motifs are engineered at periphery by conjugation to recombinant proteins, peptides, fluorophores, or recognition domains through chemically or genetically, fulfilling the needs of various biological relevance and a wide range of practical usages. This chemistry has witnessed significant growth over the last few decades and several interesting ATCUN derivatives have been described. The redox role of the ATCUN moieties is also an important aspect to be considered. The redox potential of designed M-ATCUN derivatives is modulated by judicious choice of amino acid (including stereochemistry, charge, and position) that ultimately leads to the catalytic efficiency. In this context, a wide range of M-ATCUN derivatives have been designed purposefully for various redox- and non-redox-based applications, including spectroscopic probes, target-based catalytic metallodrugs, inhibition of amyloid-beta toxicity, and telomere shortening, enzyme inactivation, biomolecules stitching or modification, next-generation antibiotic, and small molecule activation.publishersversionpublishe