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A reduction in composite action using a partial shear connection (PSC) in the hogging moment region of a steel–concrete bridge can mitigate the concrete tensile cracking risk while maintaining the structural ultimate bearing capacity. To date, specific mechanical effects, important for the establishment of evaluation theory, have not been studied. To this end, four girders and six push-out specimens were tested for the effect investigation. Numerical analysis with material damage plasticity models and an analytical study were conducted for parametric and mechanistic investigations. The push-out test results showed that a wrapping rubber sleeve reduced the shear stiffness of the stud by 91.9%, whereas its strength varied slightly. The girder test results showed that arranging rubber sleeved stud (RSS) connectors in the composite girders reduced the girder load-carrying capacity and bending stiffness by 17% and 12%, respectively. Moreover, the concrete tensile cracking performance was improved. The analysis results showed that, for reducing the concrete tensile stress, the RSS connector in the girder had a more favourable effect on prestress distribution than increasing the ordinary stud spacing. In addition, an evident stress concentration appeared when the stud distance was increased. According to the analytical analysis of the girder under negative bending, the concrete tensile stress is exponentially related to the interlayer stud stiffness, and the exponential is expected to be 5/3. The research revealed the detailed mechanical behaviour of the girder with a PSC and simultaneously compared the effects of the two PSC methods. This research will help establish design and evaluation methods for PSC action. This research was sponsored by the National Natural Science Foundation of China (No. 51978501), Fundamental Research Funds for the Central Universities (No. 22120210437), and China Scholarship Council (No. 202106260050). This support is greatly appreciated.

One of the most common load modes is flexure. The paper measures and models the flexural strength and modulus of a bio-polyethylene reinforced with thermos-mechanical fibers from corn stover. Moreover, the authors use modified rules of mixtures to evaluate the contribution of the reinforcements to the properties of the composite. It was found a high impact of coupling agent content on the strength of the composites, and materials with a 6% of such agent and 50% of reinforcement increased 181% the strength of the matrix, and 464% its modulus. The obtained values are noticeable higher than polypropylene and some of its composites. Micromechanics analysis shows that the effect of natural fiber reinforcement on the flexural properties of a bio-based PE is similar to the effects on a polyolefin. Thus, the use of fully bio-based composites can be proposed as a substitute for some oil-based polymers, partially bio-based materials, and their composites

The increasing need of society to develop more sustainable and renewable materials has made vegetal fibers an interesting potential substitute for synthetic fibers in strengthening systems, due to their considerable strength and deformation capacity. This paper aims to increase the knowledge on how the materials interact between them in vegetal FRCM composites to strengthen concrete structures. To do it, two fibers were selected: cotton (CO), due to its good deformation capacity, and hemp (HE), due to its high strength. A low-viscosity and high adherence epoxy resin was used to coat the yarns to protect them from the alkali environment of the cementitious matrix. To study the FRCM-substrate interaction, an adaptation of the test methodology described in ISO 10080:2005 was developed and performed. Three different lengths (30, 40, and 50 cm) were used to obtain the optimal bonding length for hemp case. A single case (50 cm) for cotton was tested to compare its behaviour against hemp. In the FRCM-substrate interaction, it is noticed that hemp-FRCM shows complete bonding as all except one specimen failed by mesh failure. In the case of cotton-FRCM, its deformation capacity (at least 4 times hemp-FRCM) made all specimens deform until the geometric end of the testing set up without the mesh breakage, bearing a lower load but keeping it constant through fiber-matrix friction. In terms of load, hemp-FRCM reached the highest load, 10% higher than cotton-FRCM’s peak load. To conclude, the testing method for assessing steel reinforcement bonding in reinforced concrete was proved to be satisfactory at assessing FRCM-concrete interaction, being able to transmit the load from the substrate to the composite without the slippage of the vegetal-FRCM Objectius de Desenvolupament Sostenible::11 - Ciutats i Comunitats Sostenibles Objectius de Desenvolupament Sostenible::9 - Indústria, Innovació i Infraestructura

The growing concern for the preservation of old buildings and the wide use of masonry in the construction of civil works has led to a great development of specific techniques to strengthen masonry structures. FRCM (fabric reinforced cementitious matrix) of vegetal fibres arises as a strengthening option to be considered because low cost, low density, recyclability and biodegradability brought by vegetal fibres. In this study, numerical models were used to represent masonry walls unreinforced and strengthened with FRCM (hemp, cotton and glass). The numerical model presents a new way of simulation of FRCM systems and their failure pattern. This was validated by comparison to previous experimental and analytical results. Results showed that proposed model is an effective calculation tools to reproduce the maximum shear of masonry walls strengthened with FRCM and subjected to cyclic loads, with variations between 7 and 15% with respect to the experimental and analytical. The numerical model was also useful to reproduce the walls hysteresis behavior, although showed some inability to reproduce the reversible crack opening-closing that was observed in the experimental tests. Authors want to thanks the research project SEVERUS (RTI2018-099589-B-I00) of the Spanish Research Agency. Authors also want to acknowledge the support provided by Bernat Almenar Muns during experimental testing. Second author is a Serra Húnter Fellow. Peer Reviewed Objectius de Desenvolupament Sostenible::9 - Indústria, Innovació i Infraestructura

Composite materials with complex internal microstructures, such as the flax nonwoven bio-composite studied in this work, require advanced numerical models in order to predict their mechanical performance. Otherwise, the micro-structural interactions that take place between their components makes very difficult to obtain their mechanical properties and failure mechanisms. This paper presents a novel methodology that couples two homogenization formulations: a phenomenological one, the serial-parallel mixing theory; and a numerical multiscale procedure. The resulting methodology has a minimal computational cost, while it is capable to account for the different interactions that take place among the composite constituents. With the proposed approach, it is possible to characterize the mechanical response of nonwoven composites and to predict their structural failure. The methodology developed is applied to a flax nonwoven biocomposite manufactured and tested by the German Aerospace Center (DLR). The good results obtained from the simulation, when compared with the experimental values, allow considering the proposed procedure an excellent approach for the analysis of large structures made with complex microstructures, such as nonwoven biocomposites.

Microplastics (MPs, size < 5 mm) are among the most environmentally challenging pollutants. Their continuous and cumulative inflow or generation in the environment is what makes them drastically problematic. These pollutants can come from a wide variety of sources; hence, they are potential vectors that pose extensive risks to environmental and human health. Microfibers (MFs) are one type of MPs. Among the most well-known types of MFs are those detached from textile articles from household laundering or industrial processes. Currently, there are many ways to retain the MFs detached from textile articles. However, as far we know, there are no methods of valorizing the retained MFs. As such, we propose a novel and sustainable treatment method to immobilize MFs in a polymeric matrix, turning them into a composite. To determine the mechanical properties of the expected composites, different proportions of polyester MFs were mixed with low-density polyethylene, which is the material proposed for the immobilization of MFs. The results show that the optimum manufacturing composition was 10% (v/v) polyester MFs in the polymeric matrix. This composition improved some of the tensile mechanical properties of the polymeric matrix. Once the composites are obtained, these can be used for different purposes This research was funded by the Secretaria d’Universitats i Recerca del Departament d’Empresa i Coneixement de la Generalitat de Catalunya (AGAUR 2018_DI_022)

The Ares mission is part of a student-led project with the aim of developing a two-stage supersonic amateur rocket. This paper discusses the progress since its foundation in 2016 and how it is planned to continue progressing to achieve this objective. Currently, 4 rockets have been built and launched, evolving different aspects of the design and construction process in each one. From the Ares I, a two-stage rocket intended to test the electronics and the structure, the mission has evolved into designing the Phobos, a rocket whose aim is to compete in European Rocketry Challenges for universities. The final objective of the Ares Mission is to launch a two-stage supersonic rocket, the Ares III

In this study, the mechanical behavior under monotonic loads of tungsten carbide-cobalt (WC-Co) composites is investigated extensively by analyzing (1) nanoindentation tests on WC particles and Co matrix, (2) nanowires made of WC-Co composites tested in tension and (3) micropillars made of WC-Co composites tested in compression. To this end, a novel computational framework consisting of two different microplane constitutive models developed for WC and Co phases are proposed. For the Co matrix, the microplane J2-plasticity, called the model MPJ2, and for the WC particles a modified version of the microplane model M7, called the model M7WC, are employed. Furthermore, finite element meshes in 3D obtained from experimental tomography reconstructions of WC-Co composites are employed to rule out any spurious geometric features that is likely to be encountered in artificially generated meshes. After calibrating the aforementioned models, it is shown that the finite element predictions not only confirm the extensive experimental observations but also shed further light into the mechanical behavior of these composites.

Aquest projecte final de grau pretén portar a terme el desenvolupament d’un producte escumós per tal d’estudiar el seu comportament tèrmic i posar, en un futur, la seva aplicació en el sector de l’edificació. La idea principal d’aquest projecte va sorgir a partir de la motivació d’avançar en el coneixement actual dels materials compostos de prestacions d’aïllament tèrmic basats en polímers d’origen animal de manera sostenible, així com a la possible contribució a l’estalvi energètic en edificacions, tant d’habitables com no habitable, existent o de nova construcció. Tot i que es proposa el projecte sense conèixer gairebé res del producte resultant, el tutor va donar l’aprovació d’aquesta idea i de seguida es va contactar amb el grup de recerca del Laboratori de Materials Sostenible i Disseny del Producte, del departament d’Enginyeria Química, Agrària i Tecnologia Agroalimentària, de l’Escola Politècnica Superior de la Universitat de Girona per tal de desenvolupar el producte i escollir les millors tècniques i mètodes aplicats. S’inicia el projecte amb la idea de mesclar diferents materials, juntament amb la caseïna, per formar una massa suficient per determinar propietats mecàniques i tèrmiques. Donats els resultats negatius a la immersió en aigua es va decidir provar amb el mètode de liofilització amb un únic component: la caseïna. El desenvolupament d’aquesta tècnica la vàrem portar a terme a la Unitat Enginyeria Ambiental, ubicat al Parc Científic i Tecnològic de la Universitat de Girona. This final degree project aims to carry out the development of a foamy product for in order to study its thermal behavior and put, in the future, its application in the sector of the building The main idea of this project arose from the motivation to advance knowledge current of composite materials with thermal insulation benefits based on polymers of origin animal in a sustainable way, as well as the possible contribution to energy savings in buildings, both habitable and non-habitable, existing or new construction. Although the project is proposed without knowing almost anything about the resulting product, the tutor gave the approval of this idea and immediately contacted the research group of the Laboratory of Sustainable Materials and Product Design, from the Department of Chemical, Agricultural and Engineering Engineering Agro-food Technology, from the Higher Polytechnic School of the University of Girona in order to develop the product and choose the best applied techniques and methods. The project begins with the idea of mixing different materials, together with casein, to form a sufficient mass to determine mechanical and thermal properties. Given the negative results in water immersion it was decided to try the freeze-drying method with a single component: the casein We carried out the development of this technique in the Engineering Unit Environmental, located in the Science and Technology Park of the University of Girona.

Composites in 25 kg batches were compounded of cellulose nanocrystals (CNC) and thermomechanical pulp (TMP) and shaped into caps at industrial facilities on a pilot-plant scale. Some of the material was also injection molded into plaques to compare the effect of laboratory-scale and pilot-scale compounding of poly(ethylene-co-acrylic acid) (EAA7) and poly(caprolactone) composites reinforced with 10 wt% CNC and TMP. The materials compounded under laboratory-scale conditions showed a different morphology, improved mechanical properties, and a higher viscosity, than the materials compounded on a pilot-scale. In some cases, the rheological properties of the melts indicated the presence of a relatively strong percolating cellulosic network, and the interphase region between the cellulose and the matrix appears to be important for the mechanical performance of the composites. After the compounding on a pilot scale, both the length and width of the pulp fibers was reduced. The TMP provided better reinforcement than the CNC possibly due to the higher aspect ratio.

In the mass production of composite materials, an unrealistic interpretation of specific parameters such as raw material consumption or cycle time per process may be counterproductive to business performance. This study proposes integrating a lean tool (Value Stream Map) into a DMAIC-based approach to improve process performance in composite padel racket manufacturing. The system presented is particularly useful in mass production as it is a customer-driven approach that aims to reduce waste (both material and time) and variation, thereby enhancing the quality of end-use composite products and their common manufacturing processes (cutting, laminating, and curing). The proposed procedure's effectiveness in improving CoFRP processing within the sporting goods industry is noteworthy as cost savings and process performance have been increased by 18.5% and 15%, respectively, in workstations where advanced composite materials are processed This work was supported by the Agència de Gestió d’Ajuts Universitaris i de Recerca [2018DI0053]

Sandwich panels composed of fabric-reinforced cementitious matrix (FRCM) and extruded polystyrene foam (EPS) represent a light and insulating solution compared with other types of enclosure walls, such as steel-reinforced concrete (RC) panels. To improve the sustainability and lightness of FRCM sandwich panels used for building enclosures, this study proposes the use of hemp fabrics in contrast to glass fabrics. Modal analysis and bending and compression tests were conducted on full-scale panels with hemp- and glass-FRCMs. The results obtained from these tests indicate that the use of hemp fabrics with greater equivalent thickness and deformation capacity than glass fabrics make the production of ductile and strength (35 % more than glass-FRCM) sandwich panels possible. Nevertheless, glass-FRCMs allow the production of more stiffened panels. In addition, this study presents a simplified analytical model of sandwich FRCM panels based on the definition of cracked section strength, which is useful in the case of full composite action in the sandwich solution. This study has been partially carried out within the project ‘‘Desarrollo de paneles industriales prefabricados tipo sándwich con materiales compuestos de matriz cementicia (FRCM) y con digitalizacion ´ BIM incorporada. PANELPLUS’’, funded by the Spanish Ministry of Science, Innovation and University through the Torres Quevedo program. The materials support of Sika AG and Mapei Spain S.A. is acknowledged. Authors want to thanks the research project SEVERUS (RTI2018- 099589-B-I00) of the Spanish Research Agency. Second author is a Serra Húnter Fellow.

Fabric reinforced cementitious matrix (FRCM) are a type of sustainable materials for structures strengthening and envisaging to develop new construction solutions. However, the wide range of possible combinations of fabric and cementitious matrixes makes it necessary to study the particular contribution of mortar and fabric in the composite action of the FRCM. In this line, this study presents the experimental, analytical and numerical evaluation of the tensile behaviour of FRCM composites. 85 FRCM specimens of different thicknesses were manufactured, with one or two embedded fabrics of different type of fibres and geometry. Fabrics made of coated vegetal fibres were also considered to be compared with commercial fabrics of coated synthetic fibres. The results show a significant increase of the ultimate tensile strength with the increase of the FRCM thickness due to a residual contribution of the mortar after the cracking stage. The analytical model was effective for the cases that showed a cracking stabilization stage. However, the numerical model allows a closer approximation to experimental results because of considering the mortar contribution in the post-cracking stage. This study has been partially financed by the “European Union – NextGenerationEU”, through the Margarita Salas program, from the Spanish Ministry of Universities. The materials support of Sika AG and Mapei Spain S.A. is acknowledged. Authors want to thanks the research project SEVERUS (RTI2018- 099589-B-I00) of the Spanish Research Agency. Third author is a Serra Húnter Fellow.

In this study, Young’s modulus of henequen fibers was estimated through micromechanical modeling of polypropylene (PP)-based composites, and further corroborated through a single filament tensile test after applying a correction method. PP and henequen strands, chopped to 1 mm length, were mixed in the presence of maleic anhydride grafted polypropylene (MAPP). A 4 wt.% of MAPP showed an effective enhancement of the interfacial adhesion. The composites were mold-injected into dog-bone specimens and tensile tested. The Young’s modulus of the composites increased steadily and linearly up to 50 wt.% of fiber content from 1.5 to 6.4 GPa, corresponding to a 327% increase. Certainly, henequen fibers showed a comparable stiffening capacity of PP composites than glass fibers. The intrinsic Young’s modulus of the fibers was predicted through well established models such as Hirsch or Tsai-Pagano, yielding average values of 30.5 and 34.6 GPa, respectively. The single filament test performed to henequen strands resulted in values between 16 and 27 GPa depending on the gauge length, although, after applying a correction method, a Young’s modulus of 33.3 GPa was obtained. Overall, the present work presents the great potential for henequen fibers as PP reinforcement. Moreover, relationships between micromechanics models and filament testing to estimate Young’s modulus of the fibers were explored.

A novel bio-based flame retardant (Phytic acid - trometamol, PA-THAM) was prepared via salt formation reaction between phytic acid and trometamol. The chemical structure and thermal stability of this novel phytate were characterized by Nuclear magnetic resonance spectroscopy (NMR), Fourier transform infrared spectroscopy (FTIR), and Thermogravimetric analysis (TGA). Afterward, the effect of PA-THAM on the flammability of PLA was investigated. On the basis of the results, 3 wt% incorporation of PA-THAM in PLA exhibited better results than pure PLA in flame combustion tests, for example, LOI value increased from 19.9 to 25.8% and ratings in UL-94 varied from No Rating to V-0 rating. This ignitionresistance performance was analyzed investigating the relationship between properties and structure. The results elucidated that the incorporation of PA-THAM significantly reduced the molten viscosity of biocomposite, which facilitated the 'heat transfer' effect to rapidly decrease the surface temperature. In comparison with neat PLA, the same load of PA-THAM in PLA had little effect on the mechanical properties of PLA-based biocomposite, which indicated that the optimum load of PA-THAM maintained the balance of fire retardancy and mechanical properties of the PLA biocomposite.

In this paper the strength of steel deck-concrete composite slabs is studied. Conventional slabs with open and dovetail profiles are studied with different designs, galvanized and stainless steel. Partial connection method (PCM) in Eurocode-4 is permitted for slabs with ductile longitudinal shear behavior. Ductility, as explained in the clause 9.7.3(3), depends on the fact that the failure load exceeds the load corresponding to the slip (0.1 mm) in more than 10%; then the slab is classified as ductile. Apparently, the aim of this criterion is to ensure the slab can undergo further deflections until the whole yielding of the cross-section is achieved, as required hypothesis by the PCM. The aim of this paper is to study the stresses developed at the cross-section of composite slabs with open and dovetail profile, in order to evaluate the yielding degree of the cross-section. Based on the results of this study, it is recommended to exclude open profiles from partial connection method (PCM), even if the slab is classified as ductile through Eurocode definition. Although all studied specimens are classified as ductile according to Eurocode-4 clause 9.7.3(3), the observed stress distribution at cross-section proves that yielding occurs in the slab with re-entrant profile only, whereas slabs with open-rib profiles remain almost elastic until their brittle failure.

In this paper, the interlaminar stresses in open-hole laminates subjected tocompressive loadsare analysed using a numerical model. This model implements the Serial/Parallel Mixing Theory (S/PMT) and aContinuum Damage Mechanics(CDM) approach. The S/PMT estimates the global stiffness in the laminate from fibre and matrix properties. The CDM approach models the damage initiation due to fibre microbuckling. The global response estimated by the model was verified with experimental data from the literature. The model predicts that the damage initiates in the laminate middle-plane where the thickest block of plies oriented in the load direction is located, and progressively propagates to the nearest block of layers with the same orientation. Two laminate stacking sequences were analysed. The interlaminar stresses around the hole presented symmetry with respect to the load direction and the perpendicular axis, being located the maximum and minimum values in different angular positions for each stress component and laminate.

This paper presents an analytical model to predict the stress redistribution around broken fibres in hybrid polymer composites. The model is used under the framework of a progressive failure approach to study the load redistribution around breaks in hybrid composites. The outcomes of the model are validated by comparing it with a spring element model. Moreover, the approach is further used to study the tensile behaviour of different hybrid composites. The results obtained show that the load redistribution around breaks depends on the stiffness ratio between both fibres as well as the matrix behaviour considered and the hybrid volume fraction. Furthermore, the different material parameters have a large effect on the tensile behaviour, with an increase of ductility achieved if the failure process of the two fibres is gradual.

Interfacial interactions between matrix and reinforcement of composites influences greatly in final properties of the material. Carbon Fibers are characterized for to have low interactions with resins when forming a composite material. In the present study, 0.3 wt% of GO/rGO were incorporated in three systems of epoxy resin/carbon fiber as reinforcing fillers, trying to profit the chemical affinity between aromatics structures of GO/rGO and polar interactions with epoxy resin. GO/rGO were characterized by XPS, TGA was performed on carbon fiber, epoxy resins and composites obtained and SEM was utilized to observe composite samples in detail once mechanical tests were conducted. Composites experienced noticeable enhancements by employing Bisphenol Epoxy (BP) cured with methyl cyclohexane-1,2-dicarboxylic anhydride (MCHDA) as matrix and carbon fiber of 300 g/cm2 as reinforcement; Youngs modulus, rupture stress and elongation to fail- ure increased almost twofold compared to non-modified composites by adding GO in the system and even superior boosts can be appreciated with rGO, which additionally improves the flexural stress from 14.6 to 30.1 GPa.

In this work, we present the development and characterisation of new cement-based composite panels reinforced with fibres recovered from wastes of protective technical clothing. The developed panels present a flexural strength (~15 MPa) and fracture toughness (~3.5 kJ/m2) that are suitable for their application on ventilated façades. The environmental impact of these panels was evaluated through the life-cycle assessment (LCA) from a cradle-to-gate approach and was compared with similar engineered materials and commercial materials used for ventilated façades (fibre cement facing tiles, ceramic tiles, and natural stone plates). Two functional units were assessed: the panel necessary to cover 1 m2 of façade, and the panel necessary to cover 1 m2 of façade providing a maximum bending stress of 17 or 24 MPa. For 17 MPa, the new composite developed has presented similar environmental performance to fibre cement facing tiles and significantly better than the traditional ceramic tiles and natural stone plates This work was supported by the Spanish AEI (Agencia Estatal de Investigación, Government of Spain) [grant number PID2019-108067RB- I00]. The author Heura Ventura is a Serra-Húnter fellow. Monica Ardanuy aknowledges the Ministerio de Universidades (Ministry of Universities, Government of Spain) for the mobility grant PRX21/00264 (Subprograma de Movilidad, Plan Estatal de Investigación Científica y Técnica y de Innovación 2017–2020) Objectius de Desenvolupament Sostenible::12 - Producció i Consum Responsables

In this work, a numerical procedure to obtain the fatigue performance of composite laminates is proposed. The formulation used is based on the Serial/Parallel Mixing Theory (SP-RoM) and a fatigue damage model. The SP-RoM acts as a constitutive law manager, obtaining the mechanical performance of the composite by solving the behaviour of each constituent material. The fatigue damage model modifies the constitutive performance of the composite constituents in order to consider the degradation of their mechanical properties due to cyclic loading. The proposed formulation is validated for two composite systems, a carbon/epoxy system and a glass/polyester system. In addition, different composite configurations are numerically evaluated and compared with experimental data, in order to prove the capabilities of the formulation. All results prove that the numerical procedure develop is an excellent tool for obtaining the fatigue life and failure mechanisms of composite materials.

The purpose of this study was to investigate the bioactive compounds of araçá-roxo by applying the Box–Behnken experimental design to evaluate the effect of temperature, time, and ethanol concentration on the extraction of phenolic compounds. The three variables evaluated significantly affected (p < .05) the extraction, and temperature proved to be the most influential variable. The optimum conditions were as follows: extraction temperature of 50°C, extraction time of 30 min, and ethanol concentration of 40%. Under such optimum conditions, the phenolic compounds, flavonoids, and anthocyanins present in the peel, pulp, and seed were determined and, separately, the phenolic and carotenoid compounds present in the extracts were identified and quantified by high-performance liquid chromatography. This study helped confirm the importance of araçá-roxo as a source of bioactive compounds, thereby demonstrating its potential for consumption

Actualment, les expectatives de la tecnologia d’impressió 3D són molt elevades, aplicant-se aquesta tecnologia en camps molt diversos com ara la biomedicina, arquitectura, electrònica, aeronàutica, tèxtil, prototipatge industrial... Alhora, la constant evolució de les ciències de materials per tal d’obtenir nous compostos amb noves propietats, dona lloc a nous materials que poden aplicar-se a la impressió 3D amb aplicacions molt diverses. Així doncs, quan es van aconseguir aïllar nanopartícules de grafè l’any 2004, l’interès per aquest material degut a les seves altes prestacions electròniques ha fet emergir innovacions industrials per la fabricació de diferents dispositius electrònics. En aquest sentit, aquest Treball Final de Grau té per objectius: utilitzar la dissolució de polímers amb la barreja del reforç en dissolució i la fusió de polímers amb la mescla del reforç en estat fos per l’elaboració de nanocompòsits per tal de determinar quina presenta millors propietats conductores, comparar les propietats conductores de dos polímers termoplàstics; el PLA i la PCL i finalment, donar una aplicació al material obtingut elaborant un prototip de placa de circuit impresa Currently, the expectations of 3D printing technology are very high high, applying this technology in very diverse fields such as biomedicine, architecture, electronics, aeronautics, textiles, prototyping industrial... At the same time, the constant evolution of material sciences in order to obtain new compounds with new properties, gives rise to new materials that can apply to 3D printing with very diverse applications. So when is managed to isolate graphene nanoparticles in 2004, the interest in this material due to its high electronic performance has emerged industrial innovations for the manufacture of different electronic devices. In this sense, this Final Degree Thesis aims to: use the dissolution of polymers with the mixture of reinforcement in dissolution and the melting of polymers with the mixture of reinforcement in a molten state for the preparation of nanocomposites in order to determine which has better conductive properties, compare the conductive properties of two thermoplastic polymers; the PLA and the PCL i finally, give an application to the material obtained by making a plate prototype of printed circuit

Every year, the textile industry generates large amounts of cellulosic waste during the production and fabrication stages. This waste is made up of fibers, with lengths are less than 10 mm that prevent its reintroduction into the manufacturing process of textile products and they end up dumped or incinerated. In this doctoral thesis, polypropylene composite materials reinforced with cellulosic waste from the textile industry have been obtained, in order to give them added value and reduce their environmental impact. The cellulosic waste that has been used is cotton wool, due to cotton is the natural fiber that is the most used in making clothes. In this process, a greater amount of this waste is generated. To obtain a polypropylene (PP) composite material reinforced with natural fibers, it is necessary to use a coupling agent to ensure a good interface between them. In addition, from a dyed cellulosic fiber, it has been used to study the effect of dye on the interface of the composite material. During this study, it was found that the organic dyes present in the cotton wool affect the quality of the interface in two ways. On the one hand, dyes increase the affinity between the cotton fibers and the matrix due to the hydrophilic character of the fibers decreases. So, they increases their chemical compatibility with the matrix. On the other hand, dyes limit the effect of coupling agents because they increase the difficulty they have in reacting with the hydroxyl groups present on the surface of the fiber. The mechanical properties of the different composite materials produced using different amounts of reinforcement and coupling agent (MAPP) have been analyzed here. The results of the tensile tests have shown a remarkable increase of the tensile strength of the matrix. However, compounds formulated with MAPP have shown significantly higher tensile strength than compounds formulated without this coupling agent. In terms of stiffness, a linear evolution has been observed in the values of the Young’s Module of the composites directly proportional to the applied reinforcement content. In contrast, it has been found that the slope of the linear fit equation obtained through the graphical representation mentioned above is lower than that other polypropylene compounds reinforced with natural fibers Cada any, la industria tèxtil genera grans quantitats de residu cel·lulòsic durant les etapes de producció i confecció de teixits. Aquest residu es compon de fibres amb longituds inferiors a 10 mm que impedeixen la seva reintroducció en el procés de fabricació de productes tèxtils i acaben abocades o incinerades. En aquesta tesi doctoral s’han obtingut materials compostos de polipropilè reforçats amb residus cel·lulòsics provinents de la indústria tèxtil, per tal de donar-los un valor afegit i reduir el seu impacte mediambiental. El residu cel·lulòsic que s’ha utilitzat és la borra de cotó doncs, el cotó és la fibra natural que més s’utilitza en la confecció de vestits, procés en el que es genera una major quantitat d’aquests residus. Per a l’obtenció d’un material compost de polipropilè (PP) reforçat amb fibres naturals és necessària la utilització d’un agent d’acoblament per a garantir una bona interfase entre elles. A més a més, en partir d’una fibra cel·lulòsica tenyida, s’ha aprofitat per estudiar quin efecte té el tint sobre la interfase del material compost. Durant aquest estudi s’ha trobat que els colorants orgànics presents a la borra de cotó afecten la qualitat de la interfase de dues maneres. Per una banda, augmenten la compatibilitat química entre les fibres de cotó i la matriu degut a que disminueixen el caràcter hidrofílic de les fibres. Per una altra banda, els tints limiten l’efecte dels agents d’acoblament degut a que incrementen la dificultat que tenen aquests per reaccionar amb els grups hidroxils presents a la superfície de la fibra. Aquí mateix s’han analitzat les propietats mecàniques dels diferents materials compostos produïts utilitzant diferents quantitats de reforç i d’agent d’acoblament (MAPP). Els resultats dels assajos a tracció, han mostrat un increment notable de la resistència a tracció de la matriu. No obstant, els compostos formulats amb MAPP han mostrat una resistència a tracció sensiblement més alta que els compostos formulats sense aquest agent d’acoblament. Pel que fa a la rigidesa, s’ha observat una evolució lineal en els valors del Mòdul de Young dels compòsits directament proporcional al contingut de reforç aplicat. Per contra, s’ha constatat que el pendent de l’equació d’ajust lineal obtinguda a través de la representació gràfica esmentada anteriorment, és inferior al d’altres compostos de polipropilè reforçats amb fibres naturals Programa de Doctorat en Tecnologia

The final publication is available at Springer via https://doi.org/10.1617/s11527-020-01583-9. Masonry is one of the eldest construction systems in the building industry, currently in use because some advantages like compressive capacity, traditional aesthetics, low cost and good practices. However, damages recorded in walls as a result of cyclic loads, have given rise to an important development in the area of strengthening and rehabilitation of this type of structural element. To counteract this problem, the vegetal FRCM arises as a strengthening competitive system for the improvement of the mechanical properties of masonry walls. In this study, an analytical model evaluates the behaviour of walls strengthened with FRCM. The model is compared with existing codes and it is validated with experimental results of shear diagonal-compression tests and shear under cyclic loads. It proved to be an effective calculation tool, useful enough to reproduce the behaviour of masonry walls strengthened with FRCM, but limited to failures not related with debonding neither sliding of FCRM material and substrate.

Currently, the huge use of tires generates large quantities of waste material which represents a severe environmental problem. The common technique used for processing waste tires is crushing using mechanical methods and separating tire components like fibers, metals, and rubber from the used tire. The aim of this research is the recycling of this rubber from crushed tires, called ground tire rubber (GTR). With this aim, the manuscript analyses key mechanical properties of the thermoplastic composites produced by blending of crushed and micronized small particles of waste rubber tires with several industrial thermoplastic polymers. These types of composites are defined based on the total amount GTR in percent by weight, in the composite, and also, the particle sizes used in each case, so these aforementioned two variables (microparticle size and amounts) along with seven common industrial polymers define a series of composites for which the mechanical properties were tested, studied, analyzed and finally presented. Finally, the results obtained show that this proposed recycling method could be a way to enhance some specific polymer properties and could contribute to reducing the total of end of life used tire stocks environmental problem.

The aim of this paper is to evaluate the influence of sustainable surface treatments —performed on flax nonwoven fabrics as textile reinforcement— on the durability of calcium aluminate cement (CAC) based composites. Two treatments are considered: an alkaline treatment (for increased stability and adhesion), and a treatment with soybean oil (to reduce fiber degradation). The cement hydration was studied by analysis of back-scattered scanning electron microscopy images, which revealed variations nearby the fibers owing their capacity for water absorption and presence of oil on the surface. A retarding effect on cement hydration was observed on the composites prepared with the oil-treated fabrics. The composites containing the alkali treated fabrics had better mechanical properties and also the highest durability. For these composites it was found an optimized fiber-matrix adhesion and penetrability of the cement to the fabric.

The design codes prescribe “a close simulation” of the uniformly distributed loads for bending tests, since, applying an ideal uniform load on the slab surface, is not technically as simple as applying concentrated loads by spreader beams. The 4-point bending test used in both standard methods m-k and PCM to determine the shear resistance of composite slabs is currently the most conventional loading arrangement. This article presents the comparison between the 4-point bending and uniform load results, obtained from both experimental tests and numerical simulations. Two groups of specimens, made with a common trapezoidal steel profile and concrete, including short and long spans, have been tested under the two loading setups. The numerical analysis of these slabs has been carried out through modelling the realistic interaction of steel and concrete. For the 4-point bending simulation, predefined vertical cracks are modelled representing the real crack inducers, whereas, for the uniform load case, the Willam-Warnke model is used. Both the experimental and the numerical results indicated that the 4-point bending test provides higher shear strength than uniform load. The experimental part was conducted by LERMA (Universitat Politècnica de Catalunya – BarcelonaTech) in collaboration with AdMaS-BUT at Brno University of Technology. The 3D FEM of composite slabs has been made through ANSYS software.

The most restrictive failure mode of steel–concrete composite slabs is longitudinal shear. The partial connection method (PCM) is a design method for longitudinal shear capacity limited to slabs showing ductile failure and assumes the complete yielding of the slab cross-section. Ductility is defined in Eurocode-4 in terms of additional strength after the first slip occurs, regardless of the total slip magnitude. This article shows that the slip behavior is significantly different depending on the shape of the sheeting profile. The slip magnitude in reentrant slabs can be large enough to drive the steel sheeting and the concrete to their yielding stresses since the two materials remain vertically clamped always. Conversely, in open-rib profiles, the slip mechanics cannot drive the materials to the yielding stresses since the vertical release of the two materials occurs earlier, when the slip exceeds specific values related to the embossments’ geometry, after which the vertical clamping is no longer possible. The results show that the vertical release between the concrete and the profiled steel sheeting is reached after the slip values about 2–5 mm in open rib profiles, whereas they remain permanently clamped in reentrant profiles. This paper demonstrates that the maximum load in open-rib slabs is related to the vertical release before the materials reach their yielding stresses. These findings are consistent with both the FEM and experimental tests presented and suggest the need to review the ductility definition in standards or the applicability of the PCM in open-rib slabs. The experimental campaign includes tests conducted at the Laboratory of Elasticity and Strength of Materials, LERMA, Universitat Politècnica de Catalunya, and external resources.

In the present work, a functionalization of polylactic acid (PLA) has been carried out to anchor maleic anhydride onto the main polymer chain to promote improvement in the compatibility of this polymer matrix with cellulose fibres. Low-molecular-weight PLA has been reacted with maleic anhydride following different procedures: a bulk reaction in an internal mixer and a solution reaction. The presence of oxygen during bulk processing did not allow for functionalization, guiding the reaction towards a decrease in the molecular weight of the material. On the contrary, a controlled reaction under an inert atmosphere in the presence of dioxane as the solvent, at reflux temperature, led to the functionalization of the polymer reaching different yields depending on the percentage of radical initiator and maleic anhydride added and reaction time. The yield of functionalization has been monitored by acid number titration as well as 1H NMR, with optimal yield values of functionalization being up to 3.5%. The PLA-functionalized formula has been used to make commercial PLA compatible with cellulose fibres derived from a thermomechanical treatment. The addition of 10% w/w of fibres to PLA increases the ultimate tensile strength (UTS) of PLA by up to 15%. The incorporation of 4 w/w of the already-functionalized coupling agent to the composite produces improvements in UTS of up to 24% regarding PLA, which confirms the functionalization from a performance point of view This research was funded by Spanish government MINECO in the framework of project MAT2017-83347-R

[EN] The thermal stability and decomposition kinetics of PLA/sisal biocomposites was discussed to evaluate the suitability of their use in energy recovery processes such as pyrolysis and combustion. The influence of the addition of sisal up to 30%wt, the presence of coupling agent, and the atmosphere of operation, i.e. inert or oxidative was discussed by means of multi-rate linear non-isothermal thermogravimetric experiments. All biocomposites showed a mean high heating value of 15 MJ/kg indicating their suitability for energy recovery processes. The thermal requirements of PLA/sisal decomposition were assessed in terms of onset decomposition temperature and apparent activation energy. A minimum of 240 degrees C and 174 kJ mol(-1) in inert environment and 225 degrees C and 190 kJ mol(-1) in oxidative environment ensured the feasibility of the reactions regardless the composition of the PLA/sisal biocomposites. The atmosphere of work lead to a greater amount of residue in case of pyrolysis reactions that would need further treatment whereas an oxidative atmosphere resulted in nearly zero final waste stream. The similar kinetics obtained for all samples regardless the amount of sisal or use of coupling agent eases the operability of energy facilities aimed of turning these biowastes into new fuels., The Spanish Ministry of Economy and Competitiveness and European Regional Development Funds are acknowledged for the projects ENE2014-53734-C2-1-R, ENE2017-86711-C3-1-R (UPOV13-3E-1947). Generalitat Valenciana is thanked for the APOSTD/2014/041 for J.D. Badia. The financial support given by the Prince of Songkla University and KTH Royal Institute of Technology is gratefully acknowledged. Rossella Acerbo and Emanuele Righi are gratefully acknowledged for their activity in the framework of their Bachelor Theses.

© 2018. This version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/ Fabric Reinforced Cementitious Matrix (FRCM) is a composite strengthening material used to strengthen masonry and concrete structures in a passive way due to the requirement of crack activation. Prestressing fabric is proposed to overcome this limitation, to increase the cracking strength and to obtain a stiffer response. With this aim, over 200 tensile tests on FRCM specimens were performed to analyse the influence of prestressing fabrics. Other variables, like fixation system, testing speed, matrix material and fabric material, were also discussed. Evidences lead to conclude that prestressing fabric of FRCM is an effective way to increase its tensile cracking strength (over 30%) and tensile stiffness.

Control of curing rate and exothermicity during processing of thermosetting composite materials is essential in order to minimize the formation of internal stresses leading to mechanical and dimensional defects in the samples, especially in thick composite samples. It was recently proposed that sequential heat release, an approach based on the kinetic control of the curing sequence of dual-curing thermosets, would enable a step-wise release of the reaction heat and therefore a better control of conversion and temperature profiles during the crosslinking stage. In this article, it is shown experimental proof of this concept obtained by means of an instrumented mold that can be used for the processing of small samples with and without carbon fiber reinforcement. Safe processing scenarios have been defined by numerical simulation using a simplified two-dimensional heat transfer model and validated experimentally.

This work represents the first step towards the application of machine learning techniques in the prediction of statistical design allowables of composite laminates. Building on data generated analytically, four machine algorithms (XGBoost, Random Forests, Gaussian Processes and Artificial Neural Networks) are used to predict the notched strength of composite laminates and their statistical distribution, associated to the uncertainty related to the material properties and geometrical features. This work focuses not only on the so-called Legacy Quad Laminates (0°/90°/ ± 45°), typically used in the design of composite aerostructures, but also on the newer concept of double-double (or double-angle ply) laminates. Very good representations of the design space, translating in low generalization relative errors of around ± 10%, and very accurate representations of the distributions of notched strengths around single design points and corresponding B-basis allowables are obtained. All machine learning algorithms, with the exception of the Random Forests, show very good performances, with Gaussian Processes outperforming the others for very small number of data points while Artificial Neural Networks have better performance for larger training sets. This work serves as basis for the prediction of first-ply failure, ultimate strength and failure mode of composite specimens based on non-linear finite element simulations, providing further reduction of the computational time required to virtually obtain the design allowables for composite laminates.

In this work, conventional sulfur and two types of organic peroxides (dicumyl peroxide (DCP) and di-(2-tert-butyl-peroxyisopropyl)-benzene (BIB)) curing systems were used to investigate the possibility for tailoring of the performance properties of GTR/NBR blends reinforced with a variable content of highly dispersive silica (0–30 phr). The curing characteristics, static mechanical and acoustical properties, swelling behavior, thermal stability, and microstructure of the prepared composites were investigated. The results show that regardless of the curing system used, increasing the content of highly dispersive silica resulted in the improvement of the mechanical properties of the studied materials. It was observed that sulfur-based systems are the best choice in terms of cross-linking efficiency determined based on torque increment and cross-link density parameters. However, further analysis of the physico-mechanical properties indicated that the cross-linking efficiency does not match the performance of specimens, and the materials obtained using organic peroxides show higher tensile properties. This is due to the improved physical interactions between the GTR/NBR matrix and highly dispersive silica when using peroxide systems. It was confirmed using the analysis of the Wolff activity coefficient, indicating the enhanced synergy.

The decomposition behaviours of composites made of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and sisal were assessed in terms of thermal stability and decomposition kinetics, under inert and oxidative conditions, by means of multi-rate linear non-isothermal thermogravimetric experiments. A statistical design of experiments was applied to study the influence of the addition of sisal (0-10-20-30%wt), the presence coupling agent (Yes/No) and the applied conditions of work (inert or oxidative). An improvement of the thermal and thermo-oxidative stability of PHBV with the addition of sisal was observed for all cases. An accurate methodology based on iso-conversional methods was applied to simulate the potential of thermal recovery technologies, such as pyrolysis and controlled combustion, to use these biocomposites after the end of their service life. The mathematical descriptions of both thermo-chemical reactions were helpful in the evaluation of the eventual optimal operational conditions to carry out a suitable energetic valorisation. A minimum of 240°C and 137 kJ/mol of activation energy in inert conditions and 236°C and 118 kJ/mol in oxidative conditions ensured the feasibility of the reactions regardless the composition of the PHBV/sisal biocomposites, which may ease the operability of further energy valorisation with the aim to turn biowaste into new fuels.

The aim of this study is to analyse the environmental impacts (EIs) of the process of preparation of new biocomposite materials obtained from polylactide (PLA) and chicken feathers (CFs). Two CFs stabilization methods and different percentages of CFs have been studied. The EIs of these new composites were compared to the impact of virgin PLA. Cradle-to-gate life cycle inventories were assessed for 0–35% v/v of CFs in a CFs/PLA biocomposite. Two CFs stabilization processes, autoclave and surfactant, were tested and compared with the aim to prioritize one of them from the environmental point of view. A composite plate of 184 × 184 × 2.2 mm3 was defined as the functional unit. Autoclave stabilization process exhibited lower environmental impact compared with surfactant stabilization process mainly due to both the lower requirements of electricity and water and the reduced pollution loads of the generated wastewater. Thus, the autoclave process was selected as the standard method when comparing the EIs of the proposed CFs/PLA biocomposites. In this sense, the addition of CFs to PLA matrix proportionally reduces all the EIs compared to pure PLA due to the replacement of PLA with CFs. This behaviour can be explained because the PLA production accounts for the 99% of the impact of the biocomposite. Consequently, CFs conveniently stabilized might be an alternative raw material to prepare CFs/PLA biocomposites with less environmental impact compared to pure PLA.

The room temperature synthesis of two Co-based hybrid layered hydroxides containing the same organic ligand (suberate [Sub]), one connected through purely electrostatic interactions (CoAl layered double hydroxide [LDH]), and the other covalently functionalized (α-CoII simonkolleite phase) has been carried out. The magnetic properties exhibit an acute difference in the magnetization temperatures (from ≈10 K for the CoAl-LDH to ≈55 K for the α-CoII). Moreover, the role of the covalent functionalization in the thermal stability and the decomposition has been investigated by a forefront characterization tool consisting of thermogravimetric analysis coupled with gas chromatography and mass spectrometry (TG-GC-MS). The LDH exhibits a higher thermal stability of ≈50 ºC with broad mass loss steps, whereas the water molecules interact stronger with the α-CoII(Sub) hybrid, suggesting a higher confinement in the interlayer space. Interestingly, at higher temperatures (>400 ºC), the α-CoII(Sub) gives rise to the selective formation of cycloheptanone, in contrast to the LDH phase leading to different carbonyl containing compounds. These findings offer new fundamental insights into the thermal behavior of hybrid materials based on layered hydroxides, highlighting the important role of covalent functionalization in its properties.

Actualment l’ús de materials plàstics en l’agricultura és indispensable. A més a més, aquests plàstics tenen usos molt diversos: s’utilitzen per a la fabricació de testos i capses per transportar les plantes, per fabricar eines per facilitar el treball, i fins i tot per millorar les condicions climàtiques a les que estan sotmeses els cultius com és el cas dels hivernacles. Tot això fa que els materials plàstics siguin necessaris pel manteniment competitiu del sector agrícola. No obstant, l’ús d’aquest plàstics representa un perjudici important pel medi ambient degut a que la major part d’aquests materials prové de fonts no renovables i que tot i haver realitzat progressos en aquests últims anys, encara no hi ha un ús suficient del reciclatge. Aquest reciclatge en el sector agrícola encara és més reduït ja que la llarga exposició a la climatologia que experimenten generalment els plàstics utilitzats en aquest sector provoca que pateixin una degradació dràstica i que dificulta el seu reciclatge o la seva reutilització. Aquest fet causa una gran quantitat de residus plàstics que acaben en abocadors i resulta indispensable reduir aquesta taxa. Per aquesta raó, actualment s’investiguen opcions més sostenibles i menys perjudicials pel medi ambient. Una de les alternatives investigades és el poli(3-hidroxibutirat) (PHB), un tipus de polihidroxialcaonat (PHA) que és una alternativa d’origen renovable i totalment biodegradable, apart de tenir unes propietats mecàniques similars a les dels polímers d’origen fòssil més utilitzats. No obstant, té un gran inconvenient, i és el seu elevat preu degut a l'elevat cost de la seva producció. Aquest fet provoca que no sigui una alternativa competitiva al mercat respecte els plàstics d’origen fòssil en les condicions actuals. Una opció per fer més assequible el preu dels materials és el reforç del PHB amb fibres naturals, un material molt més econòmic i que fins i tot pot provenir d’un residu agrícola, significat d’aquesta manera l’aprofitament de residus produïts en gran quantitats en el mateix sector en que es vol aplicar aquests materials Nowadays the use of plastic materials in agriculture is indispensable. In addition, these plastics have very diverse uses: they are used to make pots and boxes to transport plants, to make tools to facilitate work, and even to improve the climatic conditions to which crops are subjected as is the case of greenhouses All this makes plastic materials necessary for maintenance competitiveness of the agricultural sector. However, the use of this plastic represents a detriment important for the environment because most of these materials come from sources non-renewable and that despite having made progress in recent years, still not there is sufficient use of recycling. This recycling in the agricultural sector is even more reduced since the long exposure to climatology that they generally experience plastics used in this sector causes them to suffer drastic degradation and that makes it difficult to recycle or reuse. This fact causes a large amount of plastic waste that ends up in landfills and it is essential to reduce this rate. For this reason, more sustainable and less harmful options are currently being investigated for the environment. One of the investigated alternatives is poly(3-hydroxybutyrate) (PHB), a type of polyhydroxyalkanoate (PHA) which is an alternative of renewable origin and fully biodegradable, apart from having mechanical properties similar to those of most commonly used polymers of fossil origin. However, it has a big drawback, and it's his high price due to the high cost of its production. This fact causes it not to be a competitive alternative on the market with respect to plastics of fossil origin in the current conditions An option to make the price of materials more affordable is reinforcement of PHB with natural fibers, a material that is much cheaper and that can even come from of an agricultural waste, meaning in this way the use of waste produced in large amounts in the same sector in which you want to apply these materials

Cohesive zone models are widely used for modelling delamination and bonded joints under different loading conditions. In the current thesis, an objective inverse method has been developed to extract the cohesive law from experimental load-displacement data for both mode I and mode II. In addition, the influence of the mode II test configuration on the cohesive law of bonded joints is discussed. Besides, the influence of environmental conditions on the fracture behaviour of two types of adhesively bonded joints is experimentally studied for Mode I and Mode II tests. The dependence of the cohesive laws on the testing temperature and ageing is also analysed. Finally, a phenomenological expression that describes the effect of temperature and ageing on the cohesive law shape is formulated. Using this expression, a constitutive cohesive zone model is enhanced to simulate the influence of the environmental conditions on the mechanical response. Els models de zona cohesiva s’utilitzen per simular delaminació i el comportament mecànic de les unions adhesives. S'ha desenvolupat un mètode invers per extreure la llei cohesiva a partir de dades experimentals de desplaçament i càrrega en la manera I i la manera II de càrrega. A més, es discuteix la influència de la configuració de l’assaig en mode II sobre la llei cohesiva. La influència de les condicions ambientals en el comportament de fractura de dos tipus d’unions adhesives s’estudia experimentalment per a assajos de mode I i mode II. També s’analitza la dependència de les lleis cohesives de la temperatura i l’envelliment. Finalment, es formula una expressió fenomenològica que descriu l’efecte de la temperatura i l’envelliment en la llei cohesiva. Mitjançant aquesta expressió, s’actualitza la formulació d’un model de zona cohesiva constitutiva per simular la influència de les condicions ambientals en la resposta mecànica.

Los carburos cementados WC-Co (comúnmente referidos como metal duro) son materiales compuestos cuya aplicación ha ido incrementando de forma exponencial, desde su introducción hace ya casi un siglo, en distintos ámbitos industriales. En gran medida, ello es debido a la excelente combinación de propiedades mecánicas y tribológicas que estos materiales ofrecen. Sin embargo, el rendimiento de componentes y herramientas de metal duro puede experimentar roturas inesperadas, bajo la aplicación de cargas tanto monotónicas (fractura) como cíclicas (fatiga), y ello es fuertemente dependiente de la microestructura del material. En este contexto, el principal objetivo de este trabajo es identificar, analizar y entender correlaciones básicas que existen entre distintos parámetros microestructurales y las propiedades mecánicas que presentan estos materiales. Para ello, se analiza una extensa y detallada base de datos recopilada a partir de tres tesis doctorales realizadas, en el seno de grupo de investigación CIEFMA, a lo largo de los últimos 20 años. Estos datos incluyen calidades de metal duro con un amplio abanico de características microestructurales - en términos de contenido de la fase ligante metálica, así como del tamaño medio de las partículas cerámicas -, y en consecuencia, de propiedades mecánicas. A lo largo del trabajo se presta especial atención a las propiedades que describen el comportamiento a fractura y fatiga de los carburos cementados. La información y el análisis crítico realizado es de gran utilidad para poder estimar y predecir la integridad mecánica de piezas fabricadas de metal duro, de cara a incrementar su rendimiento, así como prolongar su vida útil.

In this article, with the aim of promoting sustainability, contributing to the circular economy and the fight against climate change, the production of composite materials from Bio-polyethylene reinforced with corn stover fibers has been studied. The behavior of the materials obtained has been studied experimentally and by mathematical models of micromechanics. The composite materials were produced by extrusion and then injection with from 10 to 50 wt.% of fibers. The creation of a good fiber-matrix interface was studied by the incorporation of coupling agent between (0&ndash, 8 wt.%). Increase of 131.2% on tensile strength for 40wt.% reinforcement was achieved by adding 6 wt.% of coupling agent. The correct interface was demonstrated by a correlation of 0.99 between the experimental results and the results of the mathematical models used.

In the present paper, residual stresses induced by honing processes on hardened steel cylinders were determined. Cubic boron nitride (CBN) abrasives were employed. Both surface measurements and depth profiles were obtained by means of XRD. SEM observations were performed on samples’ surface. Roughness and material removal rate were also measured. Compressive residual stresses, which are known to increase fatigue life of components, were reported both in the axial and in the tangential direction. Shearing stresses were negligible. If only rough honing is taken into account, as a general trend, the lower cutting conditions used, the higher surface stresses are. A similar situation was found when only semifinish or only finish honing is considered. In most cases studied, stress profiles similar to those obtained in grinding processes, in which compressive stresses decrease with depth, were observed. However, in rough honing at hard cutting conditions, a typical hook-shaped profile was found with maximum compressive stress at 80-µm depth. Such shape is usual in turning processes. In order to obtain high surface stresses a rough, semifinish or finish honing operation with low cutting conditions is recommended. However, if stresses are to be obtained at a certain depth, rough honing at high cutting conditions is to be selected.

Fabric-reinforced cementitious matrix (FCRMs) are promising composite materials for the retrofitting and reinforcement of existing structures. In this study, vegetal meshes consisting of hemp and cotton coated with epoxy were manufactured and combined with a cementitious matrix to strengthen masonry walls. A synthetic glass fibre mesh was also tested. Several walls were manufactured, strengthened, and tested under cyclic loading. The results allow us to compare the performances of different mesh configurations in terms of size and materials. All strengthening solutions significantly increased shear strength capacity and the ability to dissipate energy compared to unreinforced walls. Further, all strengthened walls exhibited multi-track pattern distributions and achieved distortion capacity improvements of up to 300%. Indicators of stiffness, energy dissipation, damping, residual deformation, and damage allow us to compare the strengthening performances of different solutions. The vegetal solutions provided superior efficiency compared to the glass-FRCM strengthened walls. Additionally, the use of a larger volume of vegetal fibres reduces the consumption of cement and can provide a sustainable solution. The main failure mechanism of the vegetal-FCRMs was debonding, which can be remedied by improvements to material interfaces. The authors gratefully acknowledge financial support from the Ministerio de Economía y Competitividad of the Spanish Government and the European Regional Development Fund through the MULTIMAS project (ref. num. BIA2015-63882-P). The first author also acknowledges the Ministry of Education Science and Technology of the Dominican Republic for financial support through its international scholarship program.

This study examines the use of alkenyl succinic anhydride (ASA)-surface treated calcium carbonate as a functional mineral additive for application in wood fiber (WF)-reinforced PLA composites. The influence of addition quantity on the material properties of PLA composites with 40 wt% fiber reinforcement was examined at mineral addition levels of 10 wt%, 20 wt% and 30 wt%, respectively. The benefits of ASA surface-treated calcium carbonate over untreated mineral were exemplified by comparing the thermomechanical properties of PLA composites at an addition level of 10 wt%. The results demonstrate that the addition of ASA-treated calcium carbonate has distinctive advantages over untreated mineral, in terms of both processability and material properties. First, it enables better control of the process by reducing the flowability of the PLA matrix. Furthermore, it improves the fiber adhesion with the PLA, allowing for a substantial reduction of PLA content in the composite formulation while maintaining material properties.

[eng] Particles dispersed in nematic liquid crystals (NLCs), also called nematic colloids, are nowadays typical experimental systems studied in the field of Soft Matter. In this scenario, the interactions and forces between colloidal particles are in equilibrium, and thus, elasticity governs inter-particle interactions. Furthermore, the application of an AC electric external field leads to a totally different scenario where the system is out-of-equilibrium, and thus, new physical phenomena can emerge. Nematic colloidal particles can be propelled under the application of an electric field, which allows for driven particles scenarios. Briefly, motion of colloids arises from the appearance of electroosmotic flows surrounding the particles. The symmetry breaking of these flows at particles apexes induces net propulsion to the particles. In this dissertation, we show that the transport modes of a single particle propelled in a NLC are different for the motion parallel and perpendicular to the averaged molecular orientation of the material, the director field. Here, the observed trends do not depend on the driving mechanism neither the propulsion speed. While motion is ballistic in the driving direction (parallel to the nematic director), our experiments show that transversal fluctuations can become superdiffusive depending on the configuration of the NLC surrounding the particle. For the superdiffusive behaviour, which is related to dipolar configurations of the nematic director, we have proposed a mechanism based on the geometry of the liquid crystal backflow to justify the persistence of thermal fluctuations affecting on the orientation of the dipolar configuration, and thus, the observed superdiffusive modes. Going further, and by using hundreds of anisometric particles, we have induced colloidal clusters assembled above a topological defect. By tuning the elastic properties of the NLC material by in situ modification of the anchoring conditions, two different configurations can be induced, aster or rotating mills. This process is achieved thanks to a photosensitive surface which allows to switch from the trans (homeotropic) to the cis (planar) isomer (NLC) under UV-light irradiation. In the case of asters, we observe the formation of stationary clusters that display radially extended density gradients with three different states of aggregation, an innermost “jammed” part, followed by a liquid-like corona and ending in a diluted, gas-like, phase. Moreover, we can describe our system with a non-equilibrium equation of state and directly determine the effective pressure and temperature in the system. In contrast, for the rotating mills we obtained a dynamic assembly that has been analysed in terms of velocities and order parameters. To understand either the different assemblies obtained or the phases observed, we developed a theoretical model that combines different interactions resulting from phoretic propulsion, dipolar forces and hydrodynamics allowing to capture the basic physics of the process. The last part of this thesis is based on steering and guiding the collective colloidal transport by means of both photo-patterning and confining devices. The first set of experiments of experiments is based on understanding the dynamics of an ensemble of flocking particles dispersed in a NLC. Furthermore, we show the implementation of obstacles for the flock to pass. To conclude, this work not only increases our fundamental knowledge of micron-sized particles dispersed in anisotropic materials, such as nematic liquid crystals, but it serves as a starting platform to explore the motion of driven colloids inside them. Special emphasis will be put on the implementation of new techniques for guiding and steering the colloidal trajectories by means of both photo-patterning and microfluidic devices, as it has been demonstrated to be key towards the control of colloidal trajectories., [cat] Les partícules dispersades en un cristall líquid nemàtic (CLN), també anomenats col·loides nemàtics, són avui dia sistemes experimentals estudiats en el camp de la “Soft Matter”. En aquest escenari, les interaccions i forces entre partícules col·loïdals es troben en equilibri, així, l’elasticitat governa les interaccions entre partícules. Més enllà, l’aplicació d’un camp elèctric altern dóna lloc a un escenari totalment diferent, on el sistema es troba fora d’equilibri, i així, nous conceptes físics poden sorgir. Els col·loides nemàtics es poden propulsar sota l’acció d’un camp elèctric, el qual permet escenaris on els col·loides són dirigits. Breument, el moviment de les partícules és degut a l’aparició de fluxos electroosmòtics al voltant de les partícules. El trencament de la simetria dels fluxos a banda i banda de la partícula indueix una propulsió neta. En aquest manuscrit es mostra des de l’estudi del transport d’una partícula individual en termes de modes de transport fins a l’estudi de moviments col·loïdals col·lectius. L’estudi d’una partícula individual s’ha dut a terme sota l’acció de dos mecanismes diferents de propulsió, el de sedimentació-difusió i la “Liquid Crystal-Enabled Electrokinetics”. Per altra banda, prenent avantatge de la última hem pogut auto-assemblar centenars de partícules formant clústers amb una distribució radial inhomogènia de la densitat de partícules. Per entendre aquest tipus de clústers hem desenvolupat un model teòric i el Dr. Arthur Straube ha realitzat simulacions que concorden tant qualitativa, com quantitativament amb les tendències experimentals. Finalment, hem estudiat el fet de traslladar un eixam de partícules, però també el fet de posar-li obstacles per on hagi de passar. Per concloure, aquest treball no només augmenta el coneixement general de partícules micro- mètriques dispersades en CLNs, però serveix com a eina per iniciar-se i explorar el moviment dirigit de col·loides dispersat en aquests.

peer-reviewed This work proposes a calibration procedure to obtain the material parameters required by the Serial/Parallel Mixing Theory for the analysis of composites. A set of experimental tests are defined to obtain the main composite failure modes. Then, it is proposed to calculate the parameters required by the formulation using the experimental results. The procedure proposed is validated by comparing the numerical results, with those obtained from the experimental campaign. This comparison shows that the Serial/Parallel mixing theory is capable of representing the failure modes of the composite for different loading scenarios as well as the material toughness

[EN] Crosslinked poly(vinyl alcohol) (PVA) based composite films were prepared as polyelectrolyte membranes for low temperature direct ethanol fuel cells (DEFC). The membranes were functionalised by means of the addition of graphene oxide (GO) and sulfonated graphene oxide (SGO) and crosslinked with sulfosuccinic acid (SSA). The chemical structure was corroborated and suitable thermal properties were found. Although the addition of GO and SGO slightly decreased the proton conductivity of the membranes, a significant reduction of the ethanol solution swelling and crossover was encountered, more relevant for those functionalised with SGO. In general, the composite membranes were stable under simulated service conditions. The addition of GO and SGO particles permitted to buffer the loss and almost retain similar proton conductivity than prior to immersion. These membranes are alternative polyelectrolytes, which overcome current concerns of actual commercial membranes such as the high cost or the crossover phenomenon., The authors would like to thank the support of the European Union through the European Regional Development Funds (ERDF). The Spanish Ministry of Economy, Industry and Competitiveness, is thanked for the research project POLYDECARBOCELL (ENE2017-86711-C3-1-R). The Spanish Ministry of Education, Culture and Sports is thanked for the FPU grant for O. Gil-Castell (FPU13/01916).

The mechanical response of IM7-8552 carbon epoxy was investigated for transverse tension and transverse tension/in-plane shear loadings at static and dynamic strain rates using transverse tension and off-axis tension specimens. The dynamic tests were carried out on a split-Hopkinson tension bar at axial strain rates from 113 to 300 $$\hbox {s}^{-1}$$ . With the already available off-axis and transverse compression test data for IM7-8552, a comprehensive data set is available now, which can be used for validation and calibration of numerical models. The measured axial stress–strain response was simulated using a fully 3D transversely isotropic elastic–viscoplastic constitutive model. The constitutive model represents a viscoplastic extension of the transversely-isotropic plasticity model developed by the authors (Vogler et al. in Mech Mater 59:50–64, 2013). An invariant based failure criterion is added to the model to be able to predict the strength for a given orientation and strain rate accurately. The strain rate dependency of the elastic and ultimate strength properties is introduced in the model through scaling functions. A good correlation between the measured and numerically predicted stress–strain response and failure of the specimens was achieved for all specimen types and both strain rate regimes.

La impressió 3D de material termoplàstic mitjançant la tècnica coneguda com a Fused Deposition Modeling (FDM) és una tecnologia de fabricació additiva relativament nova i amb una gran projecció de futur. Aquest mètode de fabricació permet una creació amb gran llibertat de dissenys diversos, d’una forma ràpida i amb un relatiu baix cost. Així doncs, tot plegat suposa un seguit de millores en comparació als altres processos de fabricació tradicional 3D printing of thermoplastic material using the technique known as Fused Deposition Modeling (FDM) is a relatively new, far-reaching future additive manufacturing technology. This method of manufacturing allows for the creation of great variety of designs quickly, with relatively low cost. All in all, this means a number of improvements over other traditional manufacturing processes