Composite Materials and Structures

A new methodology of using impact-based vibration measurement of a suspended beam coupled with circle-®t approach is discussed to measure damping of SiC particulate reinforced magnesium composites. This study also focuses on the dependence of damping capability of the composite with SiC particulate size variation.

Pure Al was reinforced with alumina particles with size ranging from micro to nano-size dimension. Magnesium was added to the Al matrix to enhance the wettability of alumina particles. Synthesis of materials was accomplished using the solidification route viz., disintegrated melt deposition technique. Energy dissipation in the form of damping capacity was determined using free-free type suspended beam arrangement coupled with circle-fit approach. Three samples with Al-4 wt.% Mg matrix were prepared that were reinforced by alumina particles whose size ranged from m to nm length scale (viz., 10, 0.3 m and 50 nm and with a volume percentage of 10.13, 1.47 and 0.94, respectively). Damping per unit volume percentage of alumina particles in the Al-Mg matrix increased by 58%, 30% and 3% for the alumina particles size of 50 nm, 0.3 and 10 m, respectively, with respect to the monolithic Al-Mg specimen. Such increase in damping can be rationalized in terms of microstructural changes that arise due to the presence of the alumina particles in the composite samples compared to that of unreinforced sample.

Coconut wood industry waste is very large in potential, which produces sawdust waste and an unused set at 40% of the yield. The industrial waste can be used as raw material for particle board. However, coconut wood sawdust waste still contains extractives which can reduce the quality of particle board. The study aims to determine the quality of coconut wood waste particle board by material treatment and the amount of urea formaldehyde adhesive (UF). The study used a Completely Randomized Design (CRD) with factorial experiments, with the treatment of ingredients (benzene alcohol 5 %, 10 % and control) and adhesive content (5% and 7%) with Tukey's further tests. The parameters observed were density, thickness swelling and internal stickiness. The results showed the treatment of adhesive levels significantly affected the development of thickness and internal adhesion. The average density value is 0.59 -0.64 g / cm3, thickness swelling is 10,98 -13,19 % and internal internal stickiness is 0.89 -1.38 kg / cm2. The particle board research results all meet the Indonesian National Standard (SNI).

The recent collapses of massive masonry structures like towers and domes have shown that the traditional stress-strain analysis is not prepared to take into account some particular aspects that are relevant for the safety assessment of ancient buildings. In this paper, the important influence of persistent loads into the damage of historic masonry is put forward and a further step into the appraisal of creep behaviour of ancient masonry is presented. By means of an experimental and numerical investigation (carried out on the material collected from the ruins of the Civic Tower of Pavia collapsed in 1989), some significant parameters describing the deviatoric and volumetric visco-elastic behaviour of the material are detected. The aim of the research is to gain experimental knowledge as a basis for mathematical modelling of long-term behaviour of masonry structures.

This document is the author's post-print version, incorporating any revisions agreed during the peer-review process. Some differences between the published version and this version may remain and you are advised to consult the published version if you wish to cite from it.

This research explores the production of polysaccharide-reinforced thin-film composites using digital light processing (DLP) 3D printing, aiming to advance options in reinforcing photocurable resin systems. Polysaccharide thin films─including cellulose nanofibers (CNF), TEMPO-oxidized cellulose nanofibers (ToCNF), chitin nanofibers (ChNF), and electrospun cellulose acetate (CA)─were synthesized and incorporated into resin matrices to develop innovative composites. The films and composites were fabricated and characterized for surface properties, mechanical strength, and thermal stability using contact angle measurements, Fourier transform infrared spectroscopy, scanning electron microscopy, profilometry, and thermogravimetric analysis. CNF composites exhibited superior tensile strength and modulus, while ChNF and CA composites demonstrated enhanced impact resistance and flexural properties due to their fibrous architecture. ToCNF composites showcased well-balanced mechanical performance attributed to the carboxyl groups introduced during oxidation. Thermal analysis revealed that CA composites had the highest onset degradation temperature and residual mass, indicating improved thermal stability. These findings highlight the potential of polysaccharide films as robust reinforcements for DLP resins, offering tailored structural properties based on thin film performance.

The mixing time of ready-mixed concrete may be prolonged for many reasons, which may affect the resulting properties in its fresh and hardened states. The effects of prolonged mixing time on the slump, compressive strength, porosity, and permeability of concrete were investigated in this paper. All mixtures were prepared with the proportion 1:1.5:2 by weight for cement, fine aggregate, and coarse aggregate, respectively. The investigated variable was the effect of water-to-cement ratios, which were 0.40, 0.45, 0.55, and 0.65. The materials were continuously mixed up for 15, 60, 120, and 240 minutes without any additional mixing water. To reduce the evaporation of the mixing water, the drum opening was tightly covered with a polyethylene perforated film. The results showed an increasing trend in the coefficient of permeability values with mixing time for all mixtures except for the mixture with a water-to-cement ratio of 0.65 which showed a reduction in value. A different trend of results for the coefficient of permeability in comparison with that for porosity was observed. The prolonged mixing time (longer than 90 minutes discharged limit specified by ASTM) does not cause a negative effect on compressive strength as long as it has workability that facilitates the casting process, as the mixtures with higher water-tocement ratios showed an increasing trend in compressive strength.

This paper presents a tri-uniform bond stress model for simulating the bond stress distribution along the lap splice length at the critical post-yield force of a reinforcing bar. The bond distribution consists of 3 parts, namely, the splitting part, the post-splitting part, and the yielding part. In each part, the bond stress is assumed to be constant. The model is applicable to simulate the bond strength of the lap splice strengthened by both transverse steel and fiber reinforced polymer (FRP). The lap splice strength in either the elastic range or post-yield range can be predicted by applying the proposed tri-uniform model. The strength of the lap splice calculated by the proposed model agrees well with experimental results of the columns confined by FRP sheets reported by other researchers. In general, it is found that the strength of the lap splice increases with increasing lap splice length, cover to bar diameter ratio and number of the FRP sheets.

Sexuality between female inmates is a poorly addressed issue in the scientific community, mainly due to the assumption of this theme as a taboo. However, same-sex relationships in confinement have been considered a coping mechanism to deal with the deprivations of reclusion, being seen as situational homosexuality, and reproducing heteronormativity. This research aimed to understand the perceptions of inmates in intimate relationships, regarding their involvement, and specifically the motivations, gender roles, dynamics and meanings of the relationships. We used a qualitative methodology, via semi-structured interviews, with fifteen female inmates of a Portuguese prison, involved in loving relationships with other female inmates. Subsequently, data were subjected to a categorical type of content analysis. The results show that only a minority of interviewees perceived their relationship as associated to situational factors or coping mechanisms. Most of them admit the possibility of maintaining their relationship after seclusion, and name love/passion and/or attraction as motivations for the relationship. Although these relationships may mirror heteronormative roles (butch and femme), the reproduction of these roles does not occur, either in the perceived power in the relationship or in sexual practices. We conclude that situational factors are not the focus of the establishment of these relationships, and that the reproduction of gender roles occurs only externally. Despite the specificities, the relationships are characterized by motivations and dynamics independent of context or sexual orientation. We hope that this study, by showing a reality without visibility and giving voice to inmates, will allow a better understanding of these relationships and their benefits and may lead to the improvement of life during imprisonment.

The paper concerns a part of the detailed seismic and static analysis on a XI century church located in Verona in the north of Italy. The seismic hazard of the entire country is appreciable and the effect on this structure is not negligible. After three earthquakes, and mainly after the two events happen on 2012 with epicentre in the Emilia's region, some cracks occurred on the main nave. The aim of the part of the work here presented, is mainly related to analyse and understand the real behaviour of the complex roof and its safety. The roof is a unique structure made by many struts in wood and ties in puddle iron. The structure bears the external layer of tiles and the interior ceiling with bas-reliefs in wood. In the first step about the knowledge of the structure, an accurate geometrical survey has been performed whit laser scanner and clinometers. On the other hand important Non destructive tests on humidity and resistance has been performed in order to assess the material feature and degradations. Further the dynamic identification of some elements plays a determinant role in terms of calibration. Lastly the historical information and data collected gives a wider view on the structure. During years some interventions have been done in order to strengthen the structure decreasing the internal forces. This changing of the structural configuration involves another global behaviour which changes differently in each truss and therefore it presents relative displacements throughout the wooden roof. The analysis of the entire structure is local and global and involves both linear and non linear evaluations. For each configuration during the year a model has been done in order to get the changing in stresses and stiffness.

This research work is concerned with the development of unsaturated polyester composites reinforced with betelnut fibers. Moreover, the fibers were chemically modified by sodium hydroxide and its effects on the fiber/matrix interaction were also evaluated. Raw and chemically modified fibers have been used in different proportions for the preparation of these composites. The optimization of fiber proportions has been done in term of their tensile strength. The sodium hydroxide treatment effect of fibers was verified by FTIR analysis and the fibers morphological aspects of fibers by SEM. Likewise, the sound absorption coefficient of composites were studied using impedance tube method. The thermal analyses of composites were made using Thermogravimetric analysis. Compared with untreated fiber composites, there was an improvement in the tensile strength of the treated fiber composites. SEM micrographs of betelnut fiber surface revealed the rough and perforated surface of fibers. Whereas, the cross sectional of the betelnut fibers showed the bigger lumen structures. The sound absorption coefficients of composites increased as the frequency increased and thicker composites appeared to perform better than those of thinner ones. The thermal stability of the treated fiber composites was found to be higher than that of untreated fiber composites.

This study focuses on the development of epoxy/luffa composites and the investigation of their mechanical and acoustical properties. The fibers underwent an alkalization treatment, and its effects on the mechanical and sound absorption properties of the composites were measured utilizing a universal testing machine and two-microphone transfer function impedance tube methods. The effects of chemical modifications on the fibers were studied using a scanning electron microscope (SEM). The thermal analyses of composites were conducted using thermo-gravimetric analysis (TGA). The composite's functional group was identified and evaluated using Fourier transform infrared spectroscopy (FTIR). The sound absorption coefficient of untreated and treated composites across a range of frequencies was very similar. Untreated composites appeared to perform better than those that were treated. Compared with untreated fiber composites, there was an improvement in the tensile strength of the treated fiber composites. The SEM characterization showed that the alkaline treatment changed the morphology of the fibers, resulting in a decrease in the sound absorption coefficients of the composites. The thermal characterization of composites showed that dehydration and degradation of lignin occurred in a temperature range of 40 to 260 °C, and the maximum percentage of cellulose was found to decompose at 380 °C.

Microwave pyrolysis of finely ground jatropha seed biochar was used as bio-filler to develop biocomposites. Effects influencing the mechanical properties of the biocomposites were investigated based on varied material ratio. Ratios by percentage of weight were determined by D-optimal (custom) mixture design using the Stat Ease “Design Expert”. The mechanical properties, such as tensile strength, modulus of elasticity, and microhardness, were the dependent variables (response). Bio-filler content was optimised to attain the overall best mechanical properties for the biocomposites. The optimized biocomposite that showcased good tensile strength, modulus of elasticity, and microhardness biocomposite ratio’s predicted mechanical properties mean values were tensile strength (9.53 MPa), modulus of elasticity (0.730 GPa), and microhardness (20.4 HV) for polylactic acid and biofiller mixture; and tensile strength (7.92 MPa), modulus of elasticity (0.668 GPa), and microhardness (18.7 HV) for...

The effect of poly (ethylene-alt-maleic anhydride) with nanoclay on bamboo nanocomposite was reported in this chapter. The Fourier transform infrared spectroscopy (FTIR), x-ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used to characterize the nanocomposites. The mechanical test was conducted and reported in this chapter. The poly (ethylene-alt-maleic anhydride) with nanoclay enhanced the physical, mechanical and thermal properties of manufactured nanocomposites.

Due to the rapid growth of high performance electronics devices accompanied by overheating problem, heat dissipater nanocomposites material having ultra-high thermal conductivity and low coefficient of thermal expansion was proposed. In this work, a nanocomposite material made of copper (Cu) reinforced by multi-walled carbon nanotubes (CNTs) up to 10 vol. % was prepared and their thermal behaviour was measured experimentally and evaluated using numerical simulation. In order to numerically predict the thermal behaviour of Cu/CNTs composites, three different prediction methods were performed. The results showed that rules of mixture method records the highest thermal conductivity for all predicted composites. In contrast, the prediction model which takes into account the influence of the interface thermal resistance between CNTs and copper particles, has shown the lowest thermal conductivity which considered as the closest results to the experimental measurement. The experimentally measured thermal conductivities showed remarkable increase after adding 5 vol.% CNTs and higher than the thermal conductivities predicted via Nan models, indicating that the improved fabrication technique of powder injection molding that has been used to produced Cu/CNTs nanocomposites has overcome the challenges assumed in the mathematical models.

aInternational Center for Computational Methods in Engineering (CIMEC), Güemes 3450 PTLC, 3000 Santa Fe, Argentina, psanchez@intec.unl.edu.ar, http://www.cimec.org.ar bPolytechnical University of Catalunia (UPC), Campus Nord, Modul C-I, Gran Capitán s/n, 08034 Barcelona, Spain, xavier.oliver@upc.es, http://www.upc.edu/es cGIMNI, National Technological University (UTN-FRSF), Lavaise 610, 3000 Santa Fe, Argentina, storo@frsf.utn.edu.ar, http://www.frsf.utn.edu.ar

This paper covers some aspects of the development of a simple and robust electrical resistivity test method which has the potential for assessing the durability of concrete. A simple low frequency AC end-to-end resistivity test was adopted as a laboratory test method and has the potential of being preferred as a quality control test in readymixed concrete plants. The test method forgoes the need for cast-in place electrodes or silver paint for electrode-concrete interface. The work presented here examines the sensitivity of electrode contact solutions and contact pressures at the electrode-concrete interface with the use of synthetic sponges. Five concretes conforming to C32/40 compressive strength class in BS EN206-1/ BS 8500-1 made from five different cement types were investigated and the work highlighted the need for using a reference conductive contact solution and a contact pressure.

This paper presents the results of an experimental investigation of two rotary-wing UAV designs. The primary goal of the investigation was to provide a set of interactional aerodynamic data for an emerging class of rotorcraft. The present paper provides an overview of the test and an introduction to the test articles, and instrumentation. Sample data in the form of a parametric study of fixed system lift and drag coefficient response to changes in configuration and flight condition for both rotor off and on conditions are presented. The presence of the rotor is seen to greatly affect both the character and magnitude of the response. The affect of scaled stores on body drag is observed to be dependent on body shape.

This paper presents the results of an experimental investigation of two rotary-wing UAV designs. The primary goal of the investigation was to provide a set of interactional aerodynamic data for an emerging class of rotorcraft. The present paper provides an overview of the test and an introduction to the test articles, and instrumentation. Sample data in the form of a parametric study of fixed system lift and drag coefficient response to changes in configuration and flight condition for both rotor off and on conditions are presented. The presence of the rotor is seen to greatly affect both the character and magnitude of the response. The affect of scaled stores on body drag is observed to be dependent on body shape.

Streszczenie: W artykule przedstawiono rodzaje, właściwości i metody określania cech mechanicznych zbrojeniowych prętów kompozytowych FRP. Na podstawie analizy wyników badania właściwości wytrzymałościowych prętów z włóknem szklanym GFRP i prętów z włóknem bazaltowym BFRP zaprezentowano metody określania gwarantowanej wytrzymałości na rozciąganie i gwarantowanego modułu sprężystości zbrojenia niemetalicznego według standardów ACI 440.1R oraz CSA-S807. Jako przykład procedury projektowania elementu betonowego zbrojonego prętami FRP omówiono metodę obliczania nośności na zginanie według ACI 440.1R. Do obliczeń wykorzystano wyniki badań właściwości mechanicznych prętów GFRP i BFRP.

The calculations of the mixture design of concrete have been widely performed according to the compressive strength or tensile strength. However, a cracked concrete/reinforced concrete structure can only be simulated by using the principles of fracture mechanics. The purpose of this study is to obtain certain expressions based on the properties of the fresh concrete and the fracture toughness of concrete, which is the fundamental parameter in analysis of the cracked structures. In accordance with this aim, the concrete mixture design method with the monogram proposed by Monteiro et al. for cement-based materials was utilized. Accordingly, 28 sets of batches with different slump values, cement contents, and water/cement ratios were cast to obtain this monogram. Fracture toughness tests on the notched beams and wedgesplitting (WS) specimens, and compression and splitting tests on cubes were conducted for hardened concrete. The fracture toughness test results were analyzed according to the effective crack model (ECM) in concrete fracture. Consequently, a mix design approach with a monogram was proposed to design according to the fracture mechanics of concrete. Furthermore, an approach based on the WS test was initially suggested to determine the fracture toughness of concrete for the ECM, which was essentially based on beams.

The experimental investigations on fracture mechanics of cement-based materials until 1970s indicated that classical linear elastic fracture mechanics (LEFM) is invalid for quasibrittle materials such as concrete. This inapplicability of LEFM is due to existence of an inelastic zone with large scale and full cracks in front of the main crack tip in concrete. This so-called fracture process zone (FPZ) is ignored by LEFM. Consequently, several investigators have developed non-linear fracture mechanics approaches to describe failure of concrete/reinforced concrete structures. Deterministic size effect laws among these non-linear approaches, for instance size effect law (SEL) by Bazant (1984), suggest that size effect on strength is primarily related to a relatively large FPZ in concrete. One of the main requirements in this law is the need to test samples, which are geometrically similar and made of the same material, and which must provide a minimum size range=1:4. The split-tension t...

Beton ve betonarme yapılarda göçme analizi yapılırken birçok lineer ve lineer olmayan yaklaşımlar kullanılmaktadır. Betonarme bir yapıyı kırılma mekaniğine göre analiz edebilmek için ilk önce, kullanılan malzemenin kırılma parametrelerinin belirlenmesi gerekir. Betondaki neme ve zamana bağlı olarak mekanik sabitlerin değişmesi ve boyut etkisinden dolayı, Lineer Elastik Kırılma Mekaniği (LEKM), kırılma parametrelerinin tespitinde yetersiz kalmıştır. Bunun nedeni çatlağın ucunda yer alan diğer malzemelere göre daha büyük bir yer işgal eden kırılma süreci bölgesinin (KSB) var olmasıdır. Betonun kırılma parametrelerini belirlemek için şartnameler ve araştırmacılar tarafından birçok lineer olmayan kırılma mekaniği modelleri önerilmektedir. Bu lineer olmayan yaklaşımlardan boyutun dayanım üzerindeki etkisini inceleyerek betonda daha büyük bir KSB olduğunu öne sürmüş ve 'Boyut Etkisi Kanunu' geliştirmiştir. Betonun kırılma mekaniğinde kiriş numuneler yaygın olarak kullanılmakla birlikte, taşınabilirlik ve hafiflik açısından bazı avantajlara sahip olduğundan küp ve silindir numuneler son zamanlarda kullanılmaya başlanmıştır. Bununla birlikte karşılıklı basınç kuvveti uygulanan küp yarma testi ile ilgili deneysel ve teorik çalışmalar oldukça sınırlıdır. Sunulan bu çalışmada, su/çimento oranı 0.6 olan, maksimum agrega çapı 8 mm'lik kesikli ve sürekli granülometrili beton karışımları hazırlanmıştır. Aynı geometriye sahip farklı boyutlu (4:2:1) küp numuneler üzerinde boyut etkisi incelenmiştir. 50x50x50 mm 3 , 100x100x100 mm 3 , 200x200x200 mm 3 'lük küp numunelerin 28 günlük yarmada-çekme dayanımları belirlenmiş, elde edilen deney sonuçları Bazant'ın "Boyut Etkisi Kuralı"na göre analiz edilmiştir. Sonuç olarak kesikli granülometriye sahip betonların daha sünek davrandığı tespit edilmiştir.

Cracking in concrete occurs from volumetric instability, mechanical loading, and/or environmental attack. Compared to conventional vibrated concrete, self-consolidating concrete often has a higher susceptibility to crack due to different mixture design, material properties and construction practices. To obtain a better understanding of self-consolidating concrete cracking behaviors for designing and constructing crack-controlled structural elements, reported current research and practices are reviewed and analyzed in this paper. It has been believed that when well designed and well constructed, high quality selfconsolidating concrete can be successfully used in various structures with cracks properly controlled.

Aim: The aim of this in vitro study was to evaluate the microleakage of the new glass ionomers ChemFil Rock and IonoluxAC in comparison to Fuji IX GP Extra and the composite Aelite LS Posterior in permanent teeth. Materials and methods: Class V standardised U-shaped cavities were made on a total of 40 freshly extracted teeth and restored with different glass ionomer materials (4 groups of 10 samples each). After thermocycling, the teeth were immersed in 0.5% basic fuchsin for 24h. They were then sectioned in the buccolingual direction. Microleakage was assessed for the occlusal and gingival margins under a microscope at 40x magnification. Results: There were significant differences among the materials used (p=0.000). While there was no dye penetration in the Fuji IX GP EXTRA group, which behaved similarly to the composite resin group, ChemFil Rock showed less microleakage than Ionolux AC. The Wilcoxon rank test showed no significant differences in the occlusal and gingival scores between the groups (p>0.05). Conclusion: Although cavities filled with a conventional glass ionomer (Fuji IX GP Extra) had significantly less leakage than cavities filled with the new glass ionomers (ChemFil Rock and Ionolux AC), these results do not reflect all the variables present in vivo conditions. As the in vitro evaluation of new materials does not always reveal their full limitations or possibilities, clinical testing of new systems remains the ultimate proof of effectiveness.

Temperatura crítica, Resistência ao fogo, Elementos mistos aço betão Resumo. Neste trabalho são apresentados resultados de ensaios realizados sob acção do fogo em elementos mistos de aço e betão, constituídos por perfis laminados, parcialmente revestidos com betão armado. Os ensaios foram realizados de acordo com a norma europeia de ensaios de resistência ao fogo EN1363 parte 1. Os elementos foram ensaiados à flexão sob acção da curva de incêndio padrão ISO834. A temperatura crítica e a resistência ao fogo foram determinadas para o estado limite último de doze elementos, para três graus de utilização (40, 60 e 80%) e para diferentes configurações dos estribos (soldados e não soldados). Foi utilizado um modelo de elementos finitos para validar a temperatura medida nos diferentes materiais (aço do perfil, betão e reforço) e o deslocamento sofrido pelo elemento. O modelo termo-mecânico foi comparado com os ensaios realizados, utilizando elementos tridimensionais e elementos de interface para simular a transferência de calor e a adesão entre os blocos de betão armado e o perfil metálico. Os resultados numéricos confirmam as medições experimentais em todas as vertentes, quando comparados deslocamentos e temperaturas.

O aço inoxidável tem reconhecidamente uma resistência ao fogo superior ao aço carbono pelo que é de prever uma crescente utilização deste tipo de aço para fins estruturais. De facto, embora mais caro que o aço carbono, o aço inoxidável pode conduzir a estruturas competitivas em virtude de necessitarem de uma menor quantidade de material de protecção térmica ou mesmo, em alguns casos, não ser necessária protecção contra incêndio, como sucede na estrutura apresentada neste artigo. Com o objectivo de modelar pelo Método dos Elementos Finitos o comportamento de uma estrutura porticada de um edifício em aço inoxidável em situação de incêndio, introduziu-se a sua lei constitutiva no programa SAFIR, um programa de elementos finitos para análise não-linear geométrica e material, especialmente desenvolvido na Universidade de Liège para estudo de estruturas sujeitas à acção do fogo. Neste programa as propriedades térmicas e mecânicas do aço são função da temperatura, de acordo com o Eurocódigo 3. Compara-se o comportamento da estrutura em aço inoxidável 1.4301 (também conhecido como 304) com o comportamento que teria se a estrutura fosse em aço carbono S235 e realçam-se os benefícios da utilização do aço inoxidável resultantes da sua maior resistência ao fogo. A utilização do aço inoxidável para fins estruturais tem estado reservada a projectos de elevado valor arquitectónico em que o carácter inovador das soluções adoptadas constitui

As lajes em madeira são estruturas leves, de fácil montagem, com excelentes características arquitetónicas, térmicas e acústicas. No entanto, a sua elevada vulnerabilidade ao fogo, obriga a que se determine e avalie o seu comportamento com rigor. Com base em ensaios experimentais, realizados para a determinação da resistência ao fogo, será possível validar um modelo de laje numérico desenvolvido com a utilização de um programa de elementos finitos, ANSYS. O modelo numérico é transiente térmico, não linear e utiliza elementos hexaédricos. Considerou-se a não linearidade das propriedades a temperaturas elevadas. As condições de fronteira, admitidas no problema, são de convecção e radiação, sendo consideradas curvas típicas para a evolução da temperatura. Estas curvas foram registadas durante os ensaios experimentais e permitiram simular o efeito da ação do fogo na superfície exposta, interior das cavidades celulares e nas aberturas ou perfurações da laje. O comportamento físico da laje é também condicionado pela formação da carbonização, sendo este fenómeno considerado no modelo numérico.

The use of calcined clays as supplementary cementitious materials provides the opportunity to significantly reduce the cement industry’s carbon burden; however, use at a global scale requires a deep understanding of the extraction and processing of the clays to be used, which will uncover routes to optimise their reactivity. This will enable increased usage of calcined clays as cement replacements, further improving the sustainability of concretes produced with them. Existing technologies can be adopted to produce calcined clays at an industrial scale in many regions around the world. This paper, produced by RILEM TC 282-CCL on calcined clays as supplementary cementitious materials (working group 2), focuses on the production of calcined clays, presents an overview of clay mining, and assesses the current state of the art in clay calcination technology, covering the most relevant aspects from the clay deposit to the factory gate. The energetics and associated carbon footprint of the...

Fluid flow patterns in traditional rotational rheometers are generally well known so that rheological parameters such as viscosity can be easily calculated from experimental data of single phase fluids and analytical solutions of the flow patterns. However, when the fluid is a suspension, where some of the particles are as large as 2 mm in diameter, these rheometers may need to be modified. The distance between the shearing planes needs to be increased, which necessitates additional physical confinement of the fluid. The inclusion of a confining wall makes current analytical solutions inapplicable here. This paper presents the analysis of a modified parallel plate rheometer for measuring cement mortar and propose a methodology for calibration using standard oils and numerical simulation of the flow. A lattice Boltzmann method was used to simulate the flow in the modified rheometer, thus using an accurate numerical solution in place of the intractable analytical solution. The simulations reproduced experimental results by taking into account the actual rheometer geometry. The numerical simulations showed that small changes in the rheometer design can have a significant impact on how the rheological data should be extracted from the experimental results. 1.

The original article presented a summary of the results and conclusions of a Comparative Test conducted within the scope of RILEM TC 189-NEC ''Non destructive Evaluation of the Concrete Cover''. The Comparative Test (CT) was intended to assess, under the same conditions, the performance of different non-destructive test (NDT) methods

La crescente sensibilità nei riguardi dell'inquinamento ambientale e le nuove disposizioni legislative in materia di protezione dell'ambiente, hanno portato negli ultimi anni ad una crescente attenzione verso i cosiddetti biocompositi, cioè verso materiali compositi ecocompatibili e/o rinnovabili, ottenuti da biopolimeri rinforzati da fibre naturali come lino, kenaf, agave ecc. Il presente lavoro intende dare un contributo alla comprensione del comportamento meccanico ed alla efficiente progettazione di performanti biocompositi, ottenuti attraverso una oculata scelta di matrici termoindurenti e termoplastiche, rinforzate con fibre di agave. Dopo avere indagato sulle peculiari proprietà delle fibre di agave, attraverso prove di trazione e prove di pull-out su singola fibra, nonché sulle effettive proprietà delle matrici selezionate, si propongono modelli teorici e di micromeccanica che descrivono correttamente il comportamento meccanico di tali biocompositi. Verifiche sperimentali, eseguite su biocompositi a fibre corte e lunghe hanno consentito di correlare le proprietà meccaniche ai particolari meccanismi di danneggiamento, confermando la bontà dei modelli teorici proposti.

Due to the vulnerability of vaulted adobe buildings during the past earthquakes, it is crucial for such building typology to be evaluated in terms of seismic capacity. This paper deals with the seismic performance of historic vaulted adobe construction in adobe houses, typical from the city of Yazd, Iran. To this end, six 1:3 scaled adobe vaults were analyzed experimentally aiming at estimating their structural performance. The tests were performed in loading-unloading steps of increasing amplitude of an imposed vertical displacement at 30% of span. The tests were carried out in two unstrengthened and four strengthened adobe vaults. Vaults were strengthened with a low cost textile reinforced mortar (LC-TRM), where a low cost fiber-glass mesh is covered with an earth-based mortar. Two adobe vaults were strengthened at intrados and the other two at extrados. The experimental results show that the vaults behavior is enhanced due to the LC-TRM application, with respect to the unstrength...

The effect of nanoclay on the degradation of low velocity impact responses of carbon fiber reinforced polymer (CFRP) composites manufactured by the vacuum assisted resin transfer molding (VARTM) process is experimentally investigated with and without exposure to seawater for marine applications. Nanoclay was dispersed into the matrix by using magnetic stirring. Samples (100 mm by 100 mm) exposed to seawater for 0, 6, and 12 months in laboratory conditions were impacted at 20, 30, and 40 J energy levels using a Dynatup8210. The damage sustained by the samples was evaluated by a thermographic imaging technique. Comparisons between conventional and nanophased CFRP composites both in conditioned and unconditioned cases were made in terms of peak force, absorbed energy, deflection, delamination area, and specific delamination energy. Water absorption was observed to be reduced due to nanoclay infusion. After 12 months of exposure to seawater 2% nanophased samples absorbed 0.39% moisture whereas control samples absorbed 0.67% moisture. Impact strength, toughness, and energy absorption decreased with increasing conditioning time by weakening the bond between the fiber and matrix and softening the matrix materials. However, reduction in properties is significantly extenuated by the incorporation of nanoclay in the matrix. Specific delamination energy (SDE) is observed to be higher in the nanophased CFRP compared to that of the conventional one at different aging periods indicating enhanced fracture toughness in the nanophased composites. The larger and stronger interfacial area produced by the nanoclay inclusion has been found to facilitate more energy absorption in the nanophased sample compared to the conventional one. Furthermore, nanoclay reduced the development of delamination by arresting the crack propagation path or by toughening the matrix. It is concluded that the excellent barrier capacity, higher surface area, and high aspect ratio of nanoclay are responsible for the superior performance of CFRP composites, which in turn, enhances the durability of composites.

Nos tempos atuais, um dos materiais mais usados e estudados são os materiais compósitos. Materiais compósitos são compostos por pelo menos dois materiais distintos e mecanicamente separáveis, de forma que a dispersão de um material em outro possa ser realizada de modo controlado, a fim de otimizar as propriedades finais, que serão únicas, não obteníveis de seus componentes separadamente. Os materiais compósitos são compostos por matriz e reforço. Nesta pesquisa utilizaram-se corpos de prova de matriz polimérica com reforços de fibra de vidro. Esta pesquisa tem como objetivo caracterizar materiais compósitos por via quantitativa e por via de suas propriedades mecânicas. Essa caracterização é muito importante para melhor conhecimento das propriedades do material utilizados, visando prever como ele se comportará em situações adversas. Fez-se um tratamento metalográfico com lixamento e polimento para análise em microscópio ótico e cálculos quantitativos em relação às fibras. Foram tiradas fotos no microscópio para analise de distribuição de fibras. Far-se-á futuramente ensaios mecânicos nos corpos de prova para obtenção de suas propriedades. Com a análise quantitativa das fibras, observou-se que alguns corpos de prova possuem uma distribuição mais heterogênea do que outros em relação ao diâmetro médio de fibras e também em relação à distribuição de fibras por área.

Yo, Isaac Alexander Iglesias Palacios, con cédula de identidad 1724979917, declaro que las ideas, juicios, valoraciones, interpretaciones, consultas bibliográficas, definiciones y conceptualizaciones expuestas en el presente trabajo; así cómo, los procedimientos y herramientas utilizadas en la investigación, son de absoluta responsabilidad de el/la autora (a) del trabajo de integración curricular. Así mismo, me

Active vibration control had been presented as an effective tool for vibration suppression of an aerobatic aircraft wing (CH650). In this work both numerical and experimental tests were performed for tested wing. Total wing was modeled in finite element software (ANSYS V.15) in which velocity feedback controlling method was integrated. Two materials were tested to compare the effectiveness of controller for each material. Scaled model was fabricated in laboratory with two different spars' materials which were [0/90] composite and aluminum foam. In experimental part piezoelectric transducers were used as actuators and sensors to perform controlling action with totally integrated controller circuit within (LABVIEW 2015). Results showed that using of velocity feedback controlling method can add more stability to the tested wing where 83% of wing's settling time was eliminated with using aluminum foam as a manufacturing material for wing's spars.

An experimental-numerical approach is presented to rationalize the plethora of results, sometimes contradictory, reflecting the characterization of an epoxy bonded steel-concrete interface. Based on data from a specially designed half-beam specimen and experimental results from other specimen geometries, combined with their respective nonlinear finite element idealizations, a classical Mohr-Coulomb failure law together with a tension cut-off are suggested for the steel-glue-concrete interface. This description can then be used in a finite element simulation of a plated reinforced concrete beam.