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This study reviewed and compared the test methods for the high-temperature performance of asphalt binder, and selected repeated creep recovery (RCR) test to evaluate the high-temperature performance of three waste-based high- viscosity asphalt binders (WHABs, including D-I, D-II, and F) and a control sample (Tafpack-Super modified asphalt, TMA). Meanwhile, shear stress, test temperature, and aging degree of binders, which could influence high-temperature behavior of binders, were also investigated, and related evaluation indexes including recovery compliance (R), non-recoverable creep compliance [J.sub.nr]), and viscous stiffness modulus ([G.sub.v]) were compared. Results show that WHABs has much better high-temperature performance than TMA; shear stress has the most prominent effect on binders' high-temperature performance, followed by aging degree, and lastly the selected test temperature in y-time curve results; R, [J.sub.nr], and [G.sub.v] values results indicate aging degree has a significant effect on binders, and improving binders' aging performance can greatly improve the high-temperature performance. Key words: high-temperature performance, waste-based high-viscosity asphalt binders (WHABs), Tafpack-Super modified asphalt (TMA), repeated creep recovery (RCR) test, aging. Cette etude a examine et compare les methodes d'essai du rendement a haute temperature d'un liant d'asphalte, ainsi que certains essais de recuperation au fluage repete (RFR) pour evaluer le rendement a haute temperature de trois liants d'asphalte a haute viscosite a base de residus (<>, y compris D-I, D-II et F) et d'un echantillon temoin (asphalte modifie Tafpack-Super<>). De plus, on a etudie la contrainte de cisaillement, la temperature d'essai et le degre de vieillissement des liants, des parametres qui pourraient influer sur le comportement a haute temperature des liants, et on a compare les indices devaluation connexes, y compris la souplesse a la recuperation (R), la souplesse non recuperable au fluage [J.sub.nr]) et le module de rigidite visqueuse ([G.sub.v]). Les resultats montrent que les WHAB ont un bien meilleur rendement a temperature elevee que le TMA; la contrainte de cisaillement a l'effet le plus important sur le rendement des liants a haute temperature, puis sur le degre de vieillissement et sur la derniere temperature d'essai choisie dans les courbes y-temps. Les valeurs R, [J.sub.nr] et [G.sub.v] indiquent que le degre de vieillissement a un effet important sur les liants, et l'amelioration du rendement des liants en matiere de vieillissement peut grandement ameliorer le rendement a haute temperature. [Traduit par la Redaction] Mots-cles : rendement a haute temperature, liants d'asphalte a haute viscosite a base de residus (<< WHAB >>), asphalte modifie Tafpack-Super <>, essai de recuperation au fluage repete (RFR), vieillissement., Introduction As one of the most important properties for asphalt pavement, high-temperature performance reflects the ability of asphalt pavement to withstand long-term vehicle loads and pavement diseases like rut-resistance in [...]

Skirted foundations are a potential foundation solution for a range of offshore structures, including hydrocarbon and renewable energy platforms and subsea structures. Offshore foundations can be subject to cyclic loading from environmental, installation, and operational events affecting the geotechnical response. A series of centrifuge tests have been performed on a shallow skirted foundation on normally consolidated kaolin clay under a range of vertical cyclic load sequences to investigate the effect of tensile or compressive average stress, the magnitude of the applied stress, and the effect of cyclic loading of low magnitude followed by consolidation on the foundation response. Results are presented as vertical foundation displacements normalized by the foundation geometry and interpreted within the traditional shear-strain contour approach. The findings indicate that the average, rather than maximum, vertical stress defines the foundation vertical displacement response and failure mode, a threshold stress exists below which a steady state is maintained even at a high number of cycles, and geotechnical resistance increases as a result of low-level cyclic loading followed by consolidation. Key words: shallow skirted foundations, cyclic loading, centrifuge modelling. Les fondations chemisees constituent une solution de base potentielle pour toute une gamme de structures en mer, y compris les plateformes d'hydrocarbures et d'energie renouvelable et les structures sous-marines. Les fondations au large peuvent etre soumises a des charges cycliques provenant d'evenements environnementaux, d'installation et d'exploitation affectant la reponse geotechnique. Une serie d'essais de centrifugation ont ete effectues sur une fondation chemisee profonde sur de l'argile kaolin normalement consolidee sous une serie de sequences de charges cycliques verticales, pour etudier l'effet de la contrainte moyenne en traction ou en compression, l'ampleur de la contrainte appliquee et l'effet du chargement cyclique, pour etudier une faible magnitude suivie d'une consolidation sur la reponse de la fondation. Les resultats sont presentes comme des deplacements de fondations verticaux normalises par la geometrie de la fondation et interpretes dans le cadre de l'approche traditionnelle du contour de deformation de cisaillement. Les resultats indiquent que la contrainte verticale moyenne, plutot que maximale, definit la reponse de deplacement vertical de la fondation et le mode de defaillance, il existe une contrainte de seuil au-dessous de laquelle un etat stable est maintenu meme a un nombre eleve de cycles et la resistance geotechnique augmente a la suite d'une charge cyclique de faibles niveaux suivis d'une consolidation. [Traduit par la Redaction] Mots-cles: fondations chemisees profondes, chargement cyclique, modelisation de centrifugeuse., 1. Introduction Skirted foundations are an established foundation type for fixed offshore oil and gas platforms and subsea infrastructure, and more recently for offshore wind turbines (Bye et al. 1995; [...]

Buried pipeline systems form vital infrastructure, all over the world, to transport resources such as water, oil, and gas from the production stage to the locations of consumption. Failure or rupture in pipelines in general and oil or gas pipelines in particular lead to not only economic losses that are expensive, but also cause extensive damage to the environment in several scenarios. One of the key reasons for buried pipeline systems failure is associated with excavation or soil trenching within the proximity of pipelines. Soil deformation associated with excavation causes relative displacement between the pipeline and the surrounding soil, which contributes to external as well as internal stresses and strains on the pipelines. In this study, numerical analyses are carried out to investigate the behaviors of buried rigid and flexible pipelines by extending the effective stress analysis and the modified effective stress analysis approaches for saturated and unsaturated soils, respectively. The pipe displacement, strains, and internal force results from the study suggest that soil trenching in unsaturated soils contribute to limited deformations within the proximity of the embedded pipelines and result in lower internal forces. The proposed methodology can be used to determine the safe depths of unsupported excavations in unsaturated soils without causing excessive strains or internal forces in the ring of rigid and flexible pipes.Key words: buried pipelines, unsupported excavation, stresses, strains, unsaturated soils, finite-element analysis.Les reseaux de conduites souterraines constituent une infrastructure vitale, partout dans le monde, pour transporter des ressources telles que l'eau, le petrole et le gaz de l'etape de la production vers les lieux de consommation. Les defaillances ou les ruptures dans les conduites en general et dans les oleoducs et les gazoducs en particulier entrainent non seulement des pertes economiques qui sont couteuses, mais causent egalement des dommages importants a l'environnement dans plusieurs scenarios. L'une des principales raisons de la defaillance des conduites souterraines est liee a l'excavation ou a la tranchee du sol a proximite des conduites. La deformation du sol associee a l'excavation entraine un deplacement relatif entre la conduite et le sol environnant, ce qui contribue aux contraintes externes et internes et aux deformations des conduites. Dans cette etude, des analyses numeriques sont effectuees pour etudier les comportements des conduites rigides et flexibles souterraines developpant les approches d'analyse des contraintes effectives et d'analyse des contraintes effectives modifiees pour les sols satures et non satures, respectivement. Les resultats de l'etude concernant le deplacement, les deformations et les forces internes des tuyaux suggerent que le creusement du sol dans les sols non satures contribue a des deformations limitees a proximite des conduites integrees et entraine une reduction des forces internes. La methodologie proposee peut etre utilisee pour determiner la profondeur securitaire des excavations non soutenues dans les sols non satures sans causer de deformations excessives ou de forces internes dans l'anneau des tuyaux rigides et flexibles. [Traduit par la Redaction]Mots-cles : conduites souterraines, excavation non soutenue, contraintes, deformations, sols non satures, analyse en elements finis., IntroductionPipeline systems are built from polyethylene, plastic or steel pipes that extend over several millions of kilometres to transport or distribute water and petroleum products all over the world (Grigoryev [...]

Carbon fiber reinforced poly(urethane-isocyanurate)-nanosilica composites CF-(PUI-NS) were manufactured by means of the vacuum-assisted resin transfer moulding technique (VARTM) at very low NS concentrations (0-4 wt%). The high strain to failure of the PUI matrix (>7%) affected tensile tests by CF reorientation. Both the tensile strength and strain to failure were highly dependent on its kinematics. CF(PUI-NS) caused an increase of the static toughness with a maximum improvement of tensile strain to failure and modulus of +28.8% and +39% at 1 wt% and 2 wt% of NS, respectively. The interlaminar shear strength ([G.sub.IC]) of the composites showed both a deterioration of -12.9% and an improvement of +9.9% for NS concentrations of 1 wt% and 4 wt%, respectively. Regardless of the Gic value, all of the composites prepared with NS presented secondary maxima of the force versus displacement plots, indicating a substantial arrest of the crack propagation velocity after delamination started. Fractographic analysis revealed several features, such as fiber pull-out, bridging as well as river patterns whereas the composites prepared with NS behaved in a more ductile fashion due to the presence of river patterns and a reduced fiber pull-out., INTRODUCTION Concerns about the effect of carbon dioxide emissions on the earth atmosphere have led to more demanding regulations within the globalized automotive industry. Within the European Union (EU), regulations [...]

In this paper, the possibility of using air as an alternative cooling medium for testing asphalt binder in the bending beam rheometer (BBR) is considered and evaluated. For this purpose, five asphalt binders were characterized with the BBR; creep stiffness, m-value, performance grade (PG), thermal stress, and critical cracking temperature were computed both for ethanol and air. In addition, the rheological Huet model was fitted to the experimental measurements to further investigate the effect of the cooling medium. It was found that air measurements result in stiffer materials, with higher low PG, higher thermal stress, and critical cracking temperature. The parameters of the Huet model confirm such a stiffening effect when air is used. Based on the material response observed in this study, further research is recommended before potentially replacing ethanol with air in the BBR, as the latter appears to provide a substantially different material grading. Key words: asphalt binder, bending beam rheometer (BBR), cooling medium, low temperature, Huet model. Dans le cadre de cette etude, on envisage et on evalue la possibility d'utiliser l'air comme substitut a l'agent de refroidissement utilise pour les essais de liants d'asphalte au moyen d'un rheometre a flexion de poutre (<< BBR >>). A cette fin, cinq liants d'asphalte ont ete caracterises avec le rheometre a flexion de poutre; la rigidite par fluage, la valeur m, la classe de rendement (<< performance grade >>), la contrainte thermique et la temperature de fissuration critique ont ete calculees tant pour l'ethanol que l'air. De plus, le modele Huet rheologique a ete adapte aux mesures experimentales afin d'etudier davantage l'effet de l'agent de refroidissement. Il s'est avere que les mesures d'air donnent lieu a des materiaux plus rigides, avec une plus grande proportion de classe de rendement bas, une plus haute contrainte thermique et une plus haute temperature de fissuration critique. Les parametres du modele Huet confirment un effet de raidissage lorsque l'air est utilise. En se fondant sur la reponse des materiaux observes dans cette etude, on recommande des recherches plus approfondies avant de potentiellement remplacer l'ethanol par l'air dans le BBR, puisque ce dernier semble produire une classification de materiau considerablement differente. [Traduit par la Redaction] Mots-cles: liant d'asphalte, rheometre a flexion de poutre (<< BBR >>), agent de refroidissement, basse temperature, modele Huet., 1. Introduction Low temperature cracking represents one of the major distresses for asphalt pavement built in regions experiencing a cold climate such as northern U.S., Canada, and northern Europe (Marasteanu [...]

Backcalculation analysis of pavement layer moduli is typically conducted based on falling weight deflectometer (FWD) measurements; however, the stationary nature of FWD requires lane closure and traffic control. To overcome these limitations, a number of continuous deflection devices were introduced in recent years. The objective of this study was to develop a methodology to incorporate traffic speed deflectometer (TSD) measurements in the backcalculation analysis. To achieve this objective, TSD and FWD measurements were used to train and to validate an artificial neural network (ANN) model that would convert TSD deflection measurements to FWD deflection measurements. The ANN model showed acceptable accuracy with a coefficient of determination of 0.81 and a good agreement between the backcalculated moduli from FWD and TSD measurements. Evaluation of the model showed that the backcalculated layer moduli from TSD could be used in pavement analysis and in structural health monitoring with a reasonable level of accuracy. Key words: traffic speed deflectometer, backcalculation, falling weight deflectometer, 3d move, deflection velocity. Une analyse par retrocalcul des modules de couches de chaussee est typiquement effectuee a partir de mesures avec un deflectometre a masse tombante (DMT); cependant, la nature fixe du DMT exige la fermeture de voies et le controle de la circulation. Dans le but de surmonter ces limitations, un certain nombre de dispositifs de deflection en continu ont ete presentes ces dernieres annees. L'objectif de cette etude visait a developper une methodologie afin d'incorporer les mesures du deflectometre de vitesse de circulation (DVC) dans l'analyse par retrocalcul. Pour realiser cet objectif, on a utilise des mesures de DVC et de DMT pour former et valider un modele de reseau de neurones artificiels (RNA) qui convertissait les mesures de deflexion au DVC en mesures de deflexion au DMT. Le modele de RNA a montre une exactitude satisfaisante avec un coefficient de determination de 0,81 et une bonne concordance entre les modules retrocalcules a partir des mesures du DMT et du DVC. L'evaluation du modele a indique que les modules retrocalcules des couches du DVC pourraient etre utilises en analyse de chaussee et en surveillance de l'etat des structures avec un niveau d'exactitude raisonnable. [Traduit par la Redaction] Mots-cles : deflectometre de vitesse de circulation, retrocalcul, deflectometre a masse tombante, mouvement tridimensionnel, vitesse de deviation., Introduction Backcalculation of pavement layer moduli using non-destructive testing (NDT) measurements is a commonly accepted procedure for evaluating pavement structural conditions (Saltan and Terzi 2008). Structural conditions evaluation of in-service [...]

A simple, yet complete framework is introduced with the aim or modelling gram breakage in sous and crusnabie granular materials. The evolution of grain breakage is measured using a specific parameter of the grain-size distribution. The evolution of this new breakage parameter is related to the applied mechanical work, which allows the predictions to be independent of the stress paths. The correlation function proposed is trilinear, and is capable of describing the initiation, development, and stabilization of breakage. The initial state, coupled with three additional parameters, is used to calibrate this function. The three parameters are related to a grain specific quantity representing the strength of the particles that form the granular medium. The theory of fractal fragmentation is adopted, and the final state is considered to be unique and described by a single parameter: the fractal dimension. When tested against experimental results, this model was able to correctly predict the crushable behavior of a sand. Key words: particle breakage, granular media, grain crushing, fractal, particle strength, grain size distribution. Un cadre mecanique a la fois simple et complet est introduit dans le but de modeliser la rupture des grains dans les sols et autres milieux granulaires broyables. L'evolution de la rupture des grains est mesuree en utilisant un parametre caracteristique de la distribution granulometrique. L'evolution de ce nouveau parametre de rupture est reliee au travail mecanique applique, ce qui rend les predictions independantes du chemin des contraintes. La fonction de correlation proposee est trilineaire, et donc capable de decrire l'initiation, le developpement et la stabilisation de la rupture. L'etat initialainsi que trois autres parametres servent a calibrer cette fonction. Les trois parametres sont relies a une quantite propre au grain, et qui represente la resistance des particules qui forment le milieu granulaire. La theorie de la fragmentation fractale est adoptee, et l'etat final est donc suppose comme etant unique, et decrit par un seul parametre : la dimension fractale. Lorsque le modele est teste et les resultats compares a des travaux experimentaux, il devient possible d'apprecier la capacite du modele a simuler le comportement d'un sable. Mots-cles: rupture des particules, milieu granulaire, broyage des grains, fractal, resistance des particules, distribution granulometrique., Introduction Granular materials are of particular interest for civil engineers and soil mechanics specialists. Over time, the integrity of these materials varies depending on the mechanical conditions, the nature of [...]

Two geosynthetic clay liners (GCLs) reported to have experienced significant shrinkage at other locations are examined on both a 3H:1V south-facing slope and a relatively flat base on a silty sand. The GCLs were overlapped by 300 mm with 400 g/m of supplemental bentonite and covered by a black 1.5 mm high-density polyethylene (HDPE) geomembrane to form a composite liner that was left exposed in a full-scale field test embankment for a period of almost 5 years. It is shown that despite the relatively uniform exposure conditions, shrinkage is highly variable with a maximum shrinkage of GCL A being 165 mm on the slope and 415 mm on the base while GCL B shrunk by up to 75 mm on the side slope and only up to 25 mm on the base. The dominant role played by variable overlap stick and heterogeneity to the locations where the overlaps are re-wetted are discussed. Based on this study of shrinkage and a related study of downslope erosion at the same site, it is concluded that neither GCLs A nor B should be left in exposed composite liners when they can be subjected to thermal cycles that can lead to hydration and dehydration of the GCL. Key words: geosynthetics, composite liner, geosynthetic clay liner, overlap, shrinkage. Deux doublures d'argile geosynthetique (GCL) qui ont connu un retrecissement significatif a differents endroits sont examines sur une pente orientee au sud de 3H:1V et d'une base relativement plate sur un sable limoneux. Les GCL ont ete chevauches de 300 mm avec 400 g/m de bentonite supplementaires et recouverts d'une geomembrane en polyethylene haute densite (HDPE) noire de 1,5 mm pour former une doublure composite qui a ete laissee exposee dans un talus d'essai a grande echelle pour une periode de pres de 5 annees. Il a ete demontre que, malgre les conditions d'exposition relativement uniformes, le retrecissement est tres variable avec un retrecissement maximal de la GCL de 165 mm sur la pente et de 415 mm sur la base tandis que la GCL B est retrecie jusqu'a 75 mm sur la pente laterale et seulement jusqu'a 25 mm sur la base. Le role dominant joue par l'adhesion du chevauchement variable et aleatoire aux endroits ou les chevauchements sont a nouveau en contact avec le produit est discute. Sur la base de cette etude du retrecissement et d'une etude connexe de l'erosion descendante sur le meme site, on conclut que ni les GCL A et ni B ne devraient etre laissees dans des revetements plastiques exposes lorsqu'ils peuvent etre soumis a des cycles thermiques pouvant entrainer l'hydratation et la deshydratation de la GCL. [Traduit par la Redaction] Mots-cles: geosynthetiques, doublure composite, revetement d'argile geosynthetique, chevauchement, retrecissement., Introduction Composite liners comprised of a geomembrane over a geosynthetic clay liner (GCL) are extensively used in landfills and increasingly in mining applications (Shackelford et al. 2000; Bouazza 2002; Rowe [...]

This study uses a critical state soil mechanics perspective to understand the mechanics behind the liquefaction of metallic ores during transport by ship. These metallic ores are transported at relatively low densities and have variable gradings containing a wide range of particle sizes and fines contents. The effect of the fines content on the location of the critical state line (CSL) and the cyclic liquefaction behaviour of well-graded materials was investigated by performing saturated, standard drained and undrained monotonic and compression-only cyclic triaxial tests. Samples were prepared at four different gradings containing particle sizes from 9.5 mm to 2 [micro]m with fines ( Key words: laboratory tests, well-graded materials, silt, fabric-structure of soils, cyclic triaxial. Cette etude utilise un point de vue selon la mecanique des sols a l'etat critique pour comprendre la mecanique derriere la liquefaction de minerais metalliques pendant le deplacement en transport. Ces minerais sont transportes a des densites relativement faibles et ont un grade variable contenant une large gamme de dimensions de particules et de contenu de fine. L'effet de la teneur en particules fines sur l'emplacement de la ligne de l'etat critique (critical state line - CSL) et le comportement de liquefaction cyclique de materiaux bien grade a ete etudie en effectuant des essais triaxiaux cycliques satures, draines et non draines monophoniques et en compression uniquement. Les echantillons ont ete prepares a quatre grades differents contenant des particules de taille 9,5 mm a 2 [micro]m avec des contenues de fines ( Mots-cles: essais en laboratoire, materiaux bien grades, limon, tissus-structure des sols, triaxiaux cycliques., Introduction Between 1988 and 2014, 24 large ore carriers with cargoes of iron and nickel ores have capsized, resulting in the loss of 177 lives (Rose 2014). The most recent [...]

During autoclave processing of composites for highperformance applications, it is mandatory to limit the porosities, which mainly depend on the hydrostatic pressure in the resin. This pressure, which is not constant during heating being affected either by resin flow either by elastic stress in the fiber stack, can be significantly different from the autoclave pressure. Modeling of resin flow and stress in the fiber stack is a key issue for prediction of the resin hydrostatic pressure, which can be related to void development. Also, the viscosity of the thermosetting matrix is a relevant parameter since it is not constant but evolves during curing going through a minimum and then increasing to an infinite value at gel point. In this work, a viscoelastic model is adopted to calculate the evolution of resin pressure during an autoclave cycle up to gelation, accounting for viscosity and degree of reaction changes. Therefore, the model includes a kinetic and rheological model whose input parameters have been experimentally determined by Differential Scanning Calorimetry and rheological analysis. The predicted resin pressure for three case studies associated to different composite and bleeder thicknesses and reinforcement materials have been discussed., INTRODUCTION Advanced polymer matrix composites are finding applications in a wide range of industries and the technology for their manufacturing is continually evolving [1]. High performance structural components are often [...]

An experimental activity, in order to assess the impact behavior at room and low temperature, of carbon fiber in vinylester resin laminates used in the shipbuilding industry, was conducted. The conditions, which simulate the impact of a tool that drop on the panel mounted on a boat hull in contact with water, were reproduced. This is a condition named water backing, in the middle between the pure impact (air backing) and the hull slamming, and not already tested before. An innovative equipment was designed and realized at University of Naples 'Federico II,' to reproduce the real dynamic material behavior in the presence of water, at the aim to investigate the influence of the water backed on the response of laminates under impact conditions. The results were obtained impacting the laminates placed between the cylindrical steel impactor and a bag containing water. A falling weight machine, equipped with a thermal chamber, was adopted for the experimental tests. The simulated test condition is completely new since no similar research is possible to find in literature. The impact behavior in hostile environments was compared to the room conditions, and the data obtained by the water backed loading tests were compared with the results by the pure impact tests. In the latter case, a completely different behavior was observed between the two different loading conditions, in terms of both load-displacement curve and the internal damage. The effect of the impact load on the laminates has been analyzed through the delamination and the indentation., INTRODUCTION Low temperature represents an environmental condition critical for structures made of composite material, in particular under dynamic loads. This problem is really important in the Artie Ocean navigation since [...]

The aim of this work is to study the structural changes that take place during the heat setting of simultaneously and sequentially biaxially stretched polyethylene terephthalate films. The rate of structural rearrangement, as detected by real-time birefringence and off-line Raman spectroscopy, DSC thermal analysis and X-rays, was found to be dependent on the state of the orientation and crystallinity attained by the samples during the stretching step. This suggested that the annealing behavior can be categorized into three regimes according to the birefringence behavior of the samples. At low deformations, the films not crystallized by strain exhibit complete birefringence relaxation without showing any sign of crystallization. The intermediate ratio samples that were stretched to the onset of the strain-induced crystallization exhibited the highest levels of birefringence increase after a short relaxation. The samples stretched well above the onset of the strain-induced crystallization exhibited intermediate level of birefringence and crystallinity increase. Therefore, the classification of the three regimes was found to be related to the onset of the strain-induced crystallization during the stretching step. POLYM. ENG. SCI., 57:550-562, 2017. [C] 2016 Society of Plastics Engineers, INTRODUCTION Heat setting is an important stage in the PET polymer film stretching processes to enhance thermal stability of stretched films. This is accomplished by in-plane dimensionally constraining the oriented [...]

Multiwall carbon nanotubes (MWCNTs) and glycidyl polyhedral oligomeric silsesquioxanes (GPOSS) are common additives to enhance electrical conductivity and flame resistance of polymers, respectively. Yet, these additions may appreciably influence their mechanical behavior. In the present work, the synergistic effect of the addition of MWCNTs and GPOSS on the mechanical behavior of multifunctional polymers subjected to several types of quasistatic loading was investigated. The results were discussed, supported by scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) analyses. A significant increase in the tensile strength of the polymers filled only with MWCNTs is observed as compared to the unfilled material. On the other hand, all other properties investigated, namely, compression, flexural as well as [G.sub.IC] fracture toughness properties were degraded. The incorporation of GPOSS into the polymer further deteriorates the mechanical behavior of the filled material. SEM analysis has revealed MWCNTs agglomerations of the order of 100 [micro]m, while EDS analysis has revealed some areas of incomplete dissolution of the GPOSS into the resin. The results underline the sensitivity of the mechanical behavior of the multifunctional polymers on the dispersion features of the additives and the significance of both CNT agglomerates and GPOSS aggregates for the observed mechanical behavior. POLYM. ENG. SCI., 57:528-536, 2017. [C] 2016 Society of Plastics Engineers, INTRODUCTION Polymeric materials are ideal candidates to develop multifunctional materials with enhanced tailored properties, due to their ability to be reinforced with different forms of additives and nanofillers. Multiwalled carbon [...]

Dynamic loadings, induced by earthquakes and other causes, will lead to the cyclic variation of both shear stress and normal stress components on the soil elements. A series of cyclic triaxial tests with and without variable confining pressure were carried out to investigate the coupling effects of cyclic shear stress and cyclic normal stress on the normalized shear modulus, G/[G.sub.max], characteristics of saturated clays. Results indicated that both the phase differences and ratios between the cyclic deviatoric stress and cyclic confining pressure exerted a constant and pronounced influence on the G/[G.sub.max], indicating that the G/[G.sub.max] properties under combined loadings will be more representative of actual field conditions than from single-loading conditions. A modified hyperbolic model considering the effects of cyclic confining pressure was further proposed. Key words: shear modulus, dynamic properties, cyclic confining pressure, triaxial tests, clays. Les charges dynamiques, induites par les tremblements de terre et d'autres causes, meneront la fois la variation cyclique des composantes de la contrainte de cisaillement et de la contrainte normale sur les elements de sol. Une serie d'essais triaxiaux cycliques avec et sans la pression de confinement variable ont ete effectues pour etudier les effets de couplage de la contrainte de cisaillement cyclique et de la contrainte normale cyclique sur les caracteristiques du module de cisaillement normalise G/[G.sub.max] des argiles saturees. Les resultats ont indique que les differences de phase et les ratios entre la contrainte deviatorique cyclique et la pression de confinement cyclique ont exerce une influence marquee et constante sur le G/[G.sub.max], indiquant que les proprietes G/[G.sub.max] sous des charges combinees seront plus representatives des conditions reelles sur le terrain que dans des conditions de charge unique. Un modele hyperbolique modifie tenant compte des effets de la pression de confinement cyclique est en outre propose. [Traduit par la Redaction] Mots-cles : module de cisaillement, proprietes dynamiques, pression de confinement cyclique, essais triaxiaux, argiles., Introduction Water-saturated, fine-grained soil deposits can be subjected to undrained cyclic loads induced by earthquakes, pile driving, explosions, ocean wave storms, and other causes. The dynamic response under such loads [...]

Previous research on random fibre-reinforced granular materials has shown that the relative dimensions of the grains and fibres significantly affect the macro-mechanical behaviour of the mixture. However, quantitative data are scarce and most previous work has focused on fine to medium sands, leaving uncertainties regarding the applicability of current knowledge to larger size aggregates such as railway ballast. In this paper, triaxial test data on 1/3 and 1/5 scale railway ballast are used to develop scaling relationships for the size and quantity of fibres needed to achieve the same reinforcing effect in granular materials of differing grain size. It is shown that, to maintain consistency across scales, fibre content should be quantified as a numerical (i.e., number of fibres per grain) rather than a volumetric ratio. It is further shown that increasing the fibre length increases the resistance of the mixture to deviator stress if the fibres are wide enough; and that provided an allowance is made for the effect of fibre tension, the changes in the stress-strain-strength behaviour of the granular matrix resulting from the changes in void ratio associated with the addition of the fibres are consistent with conventional soil mechanics theory across scales. Key words: fibre reinforcements, granular materials, railway ballast, scaling relationships. Des recherches anterieures sur les materiaux granulaires aleatoires renforces de fibres ont montre que les dimensions relatives des grains et des fibres influencent sensiblement le comportement macromecanique du melange. Toutefois, les donnees quantitatives sont rares et la plupart des travaux anterieurs ont mis l'accent sur des sables fins moyens, laissant les incertitudes quant; a l'applicabilite des connaissances actuelles pour des agregats de taille plus grande comme les ballasts de chemin de fer. Dans cet article, des donnees d'essai traxial, sur des ballasts de chemin de fer echelle 1/3 et 1/5 permettent d'etablir des relations de mises l'echelle de la taille et de la quantite de fibres necessaires pour obtenir le meme effet de renforcement dans les materiaux granulaires de granulometrie differente. Il est demontre que, pour maintenir la coherence dans l'ensemble d'echelles, la teneur en fibres doit etre quantifiee comme un chiffre numerique (c.-; I-d., le nombre de fibres par grain) plutot qu'un rapport volumetrique. Il est montre davantage qu'augmenter la longueur des fibres augmente la resistance du melange; a la contrainte deviatorique si les fibres sont assez larges; et qu'une tolerance est prevue pour l'effet de la tension de la fibre, les changements dans le comportement de contrainte-deformation-resistance de la matrice granulaire resultant de modifications de l'indice des vides lie l'ajout des fibres sont conformes la theorie de la mecanique de sol conventionnel travers les echelles. [Traduit par la Redaction] Mots-cles : renforts de fibres, materiaux granulaires, ballast de chemin de fer, relations avec la mise l'echelle., Introduction It is well-known that the strength and ductility of a sand can be improved by the addition of randomly distributed fabric, polymer or metal fibres (e.g., Michalowski and Cermak [...]

In this work, polyamide 6 (PA6) as a charring agent has been used in combination with thermoplastic polyurethane (TPU)-microencapsulated ammonium polyphosphate (MTAPP) forming intumescent flame retardants (IFRs) which applies in polypropylene (PP). The effects of the IFRs on the flame retardancy, morphology of char layers, water resistance, thermal properties and mechanical properties of flame-retardant PP composites are investigated by limiting oxygen index (LOI), UL-94 test, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and mechanical properties test. The results show that the PP/MTAPP/PA6 composites exhibit much better flame-retardant performances than the PP/MTAPP composites. The higher LOI values and UL-94 V-2 of the PP/MTAPP composites with suitable amount of PA6 are obtained, which is attributed to the thick and compact char layer structure evidenced by SEM. The results from TGA and DSC demonstrate that the introduction of PA6 into PP/ MTAPP composites has a great effect on the thermal stability and crystallization behaviors of the composites. Furthermore, the mechanical properties of PP/MTAPP/PA6 composites are also improved greatly due to the presence of PA6 as a charring agent., INTRODUCTION Polypropylene (PP), as an important commodity plastic, has been widely applied in many fields, such as cars, electronic shells, architectural materials, furniture, interior decorations, etc. [1-3] However, PP is [...]