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The rapid advancement of electrical and telecommunication facilities has resulted in increasing requirements for the development of electromagnetic interference (EMI) shielding composites. Accordingly, an experimental study was conducted to evaluate the EMI shielding performance of carbon nanomaterial (CNM)-embedded carbon-fiber-reinforced polymer (CFRP) or glass-fiber-reinforced polymer (GFRP) composites. Nine combinations of CNMs and carbon or glass fibers were used to fabricate the composites. The synergistic effects of CNMs on the EMI shielding performance were systematically investigated. The results indicated that plate-type CNMs (i.e., graphene and graphite nanoplatelets) have more prominent effects than fiber-type CNMs (carbon nanofibers). The composites fabricated with CFRP afforded higher EMI shielding than the GFRP-based composites. Among the eighteen samples, 3% CNT-GNP in CFRP composites, which included plate-typed CNM, exhibited the best EMI shielding performances, showing 38.6 dB at 0.7 GHz. This study helps understand the shielding performance of CNM-embedded CFRP and GFRP composites in electrical and telecommunication facilities.

The use of fiber reinforced polymer (FRP) for flexural strengthening of reinforced concrete (RC) beams has become a popular strengthening technique. Significant amount of work is available on the short-term flexural behavior of RC beams strengthened with near-surface mounted (NSM) technique. However, their time-dependent flexural behavior, specifically under high service temperature, has not yet been addressed. This paper presents an experimental work to evaluate the time-dependent behavior of NSM carbon FRP (CFRP)-strengthened RC beams. The experimental program included 23 beams, where the effect of different parameters such as strengthening (CFRP) area, steel reinforcement ratio and applied temperature (20 and 50 °C) have been considered. Experimental results show that the effect of strengthening area is significant on the flexural short-term response of the beams, while minor effects are found on the time-dependent deflections. On the other hand, increasing the service temperature has no significant effect on the short-term tests, but it produces a large increase in the time-dependent deflection of the specimens. Finally, an analytical procedure for the prediction of time-dependent deflections, which is based on the age-adjusted effective modulus method (AEMM), is presented. Good agreement between the experimental results and analytical predictions on time-dependent deflections is shown This research was supported by the Spanish Ministry of Science and Innovation (MCIN/ AEI) under project PID2020-119015GB-C22 and the Generalitat de Catalunya (under the grant numbers: 2019FI_B 00054 and 2020_FISDU 00476) Open Access funding provided thanks to the CRUE-CSIC agreement with Elsevier

In this study, glass fiber reinforced composite layers which are with and without additives of 0.1 wt.% multi walled carbon nanotubes (MWCNTs) of epoxy were manufactured by vacuum infusion method. Unlike the conventional methods, punching was used in processing and drilling of these materials. The 62 - 64 HRC hard punches made of 1.3343 material with specially designed 90 degrees, 30 degrees, 15 degrees, V, C profiles were used for punching of composites. Additionally, made of 1.2379 material with 62 - 64 HRC hardness, the mold with 0.05, 0.01 and 0.16 mm clearance values was used. Fujifilm prescale and chatillon load cell were used for force measurement that showed the pressure applied by punches with different cutting profiles. Hole diameter, delamination and burring were analyzed by 3d laser scanner. In test values with mold's 0.05 mm clearance, no burr was observed. The cutting surface of MWCNTs doped composite materials was found to be cleaner and material strength was higher.

Considering their energy and resource efficiency, fiber-reinforced plastics (FRPs) have been displacing metals and metal alloys for lightweight constructions. During the semiautomated manufacturing process of FRPs, and in particular during the laying of reinforced fabric layers, foreign bodies are enclosed within them, which in turn reduce the mechanical performance of FRPs. The research project presented in this article investigated if the loss in mechanical properties, such as tensile, flexural, and impact strengths, depends on the position of defined local defects, polytetrafluorethylene (PTFE) in this case, in the thickness direction of FRPs. In order to achieve this aim, PTFE was placed in different layers of reinforcing fabric before infusion. Subsequently, the mechanical performance of the fabricated FRPs was tested and evaluated. On the basis of the experiment, it can be concluded that the loss in mechanical properties was maximal if PTFE was laid in the middle position of FRPs in the thickness direction.

A two-step homogenization procedure is presented to investigate the stiffness of a unidirectional continuous fiber-reinforced composite material containing voids of different shapes and volume contents. Since the Mori&ndash, Tanaka scheme is limited to moderate volume contents of the inhomogeneity phase, fiber and matrix are homogenized with semi-empirical relations with use of the adjusted fiber volume content in a first step. In the second step, the Mori&ndash, Tanaka scheme is applied to obtain the homogenized stiffness tensor of a transversely isotropic material containing voids aligned with the fiber direction. The voids are modelled with infinite length, but an elliptic base characterized by the aspect ratio. The tensor components of the Eshelby tensor for this case are presented in closed form for a transversely isotropic material depending on the aspect ratio and matrix material properties. The scheme is solved directly for easy implementation and the use of fast calculations of the effective engineering constants of a composite material containing voids. Experimental results from literature for different void contents and shapes are compared to the predicted moduli with cylindrical voids. From the results it is further concluded that the aspect ratio of the void and the manufacturing process of the composite should be considered.

© 2020 by the authors., Nowadays, the interest on nanofibrillated cellulose (CNF) has increased owing to its sustainability and its capacity to improve mechanical and barrier properties of polymeric films. Moreover, this filler shows some drawbacks related with its high capacity to form aggregates, hindering its dispersion in the matrix. In this work, an improved procedure to optimize the dispersability of CNF in a thermoplastic starch was put forward. On the one hand, CNF needs a hydrophilic dispersant to be included in the matrix, and on the other, starch needs a hydrophilic plasticizer to obtain a thermoformable material. Glycerol was used to fulfil both targets at once. CNF was predispersed in the plasticizer before nanofibrillation and later on was included into starch, obtaining thin films. The tensile strength of these CNF–starch composite films was 60% higher than the plain thermoplastic starch at a very low 0.36% w/w percentage of CNF. The films showed a noticeable correlation between water uptake, and temperature and humidity. Regarding permeability, a ca. 55% oxygen and water vapor permeability drop was found by nanofiller loading. The hydrolytic susceptibility of the composite was confirmed, being similar to that of the thermoplastic starch., This research was funded by University of Girona through the Program of the Improvement of the Scientific Production and the MINECO project AGL2015-63855-C2-1-R.

This paper presents a study into bond behaviour under sustained loading of Near-Surface Mounted (NSM) Carbon-Fibre Reinforced Polymers (CFRP) concrete joints, through an experimental programme and a numerical analysis. The experimental programme consisted of eight NSM CFRP-concrete pull-out specimens tested under sustained loading and laboratory conditions (20 °C and 55%HR) inside a climatic chamber. Previously, the instantaneous bond behaviour of the NSM CFRP-concrete joint was studied using 18 specimens tested until failure. Furthermore, the tensile behaviour of the adhesive under instantaneous and sustained loading was studied at different loading levels under the same environmental conditions. Finally, a numerical procedure was proposed to predict the bonded joint response under sustained loading. A creep coefficient and a strength reduction factor were applied to the instantaneous bond-slip law to simulate the degrading effect the sustained loading had on the behaviour of the bonded joint. Good agreement between the experimental and numerical results was obtained for the tested parameters, however, further research needs to be carried out in order to extrapolate this methodology to other cases This work was supported by the Spanish Government (MINECO) [Project Ref. BIA2017-84975-C2-2-P]; the University of Girona [grant number IFUdG2018/28]; and the Generalitat de Catalunya [grant number 2019FI_B 00054] Open Access funding provided thanks to the CRUE-CSIC agreement with Elsevier

The use of mechanical anchorage systems can delay or prevent premature failure of RC structures with externally bonded fiber-reinforced polymer (EB-FRP) laminates. This work reports the results of an experimental program aimed at studying the bond behavior of a metallic anchorage plate, typically used for prestressed EB-FRP systems. The overall experimental program comprised 17 concrete prisms with carbon fiber–reinforced polymer (CFRP) laminates externally bonded to the concrete with mechanical anchorage at the end and to which different levels of normal stress were applied. Direct shear tests were carried out using two configurations: (1) steady-state tests, in which the laminate was pulled out from the block with increasing force and at constant temperature (20°C, 60°C, and 80°C); and (2) transient tests, in which the laminate was pulled out with constant force (0.36%, 0.45% and 0.54% of strain) and the temperature was gradually increased. Experimental results showed that the ultimate capacity of the mechanical anchorage can decrease by 44%–59% depending on the temperature and level of normal stress This work was supported by FEDER funds through the Operational Program for Competitiveness Factors—COMPETE and National Funds through the Portuguese Foundation for Science and Technology (FCT) under Project No. FRPLongDur POCI-01-0145-FEDER-016900 (FCT PTDC/ECM-EST/1282/2014) and partly financed by Project POCI-01-0145-FEDER-007633. The first author acknowledges Grant No. SFRH/BD/98309/2013 provided by FCT. The second author acknowledges the Spanish Government (Ministerio de Educación, Cultura y Deporte) for the José Castillejo grant ref. CAS16/00288

El present Treball Final de Grau ha tingut per objectiu principal desenvolupar materials compòsits completament biodegradables per impressió 3D, utilitzant àcid polilàctic (PLA) i policaprolactona (PCL) com a matriu, i fibres Kraft blanquejades d’eucaliptus com a reforç. Dins la tècnica d’impressió 3D se solen utilitzar materials comercials que el mateix fabricant d’impressores 3D ofereix. Aquests materials solen ser polímers derivats del petroli no biodegradables com el polipropilè (PP) o l’acrilonitril butadiè estirè (ABS), així com polímers biodegradables com l’àcid polilàctic (PLA) o les policaprolactones (PCL). No obstant, aquests últims no ofereixen les mateixes propietats mecàniques i tèrmiques que els polímers derivats del petroli. Per tant, per tal d’aconseguir que aquests polímers biodegradables puguin competir amb els derivats del petroli en termes tècniceconòmics, una opció versemblant és la producció de materials compostos, els quals consisteixen en l’addició d’un reforç per dotar-lo de millors propietats i, tanmateix, aconseguir un material de caràcter més sostenible reduint l’impacte mediambiental.

Modification in the resin-rich region between plies, also known as the interlaminar region, was investigated to increase the toughness of laminate composites structures. To achieve suitable modifications, the complexities of the physical and chemical processes during the resin curing procedure must be studied. This includes analyses of the interactions among the co-dependent microstructure, process parameters, and material responses. This dissertation seeks to investigate these interactions via a series of experimental and numerical analyses of the geometric- and temperature-based effects on locally interleaving toughening methods and further interlaminar synergistic toughening without interleaf. Two major weaknesses in composite materials are the brittle resin-rich interlaminar region which forms between the fiber plies after resin infusion, and the ply dropoff region which introduces stress concentration under loads. To address these weaknesses and increase the delamination resistance of the composite specimens, a dual bonding process was explored to alleviate the dropoff effect and toughen the interlaminar region. Hot melt bonding was investigated by applying clamping pressure to ductile thermoplastic interleaf and fiber fabric at an elevated temperature, while diffusion bonding between thermoplastic interleaf and thermoset resin is performed during the resin infusion. This method increased the fracture energy level and thus delamination resistance in the interlaminar region because of deep interleaf penetration into fiber bundles which helped confining crack propagation in the toughened area. The diffusion and precipitation between thermosets and thermoplastics also improved the delamination resistance by forming a semi-interpenetration networks. This phenomenon was investigated in concoctions of low-concentration polystyrene additive modified epoxy system, which facilitates diffusion and precipitation without increasing the viscosity of the system. Additionally, chemical reaction induced phase separation, concentration of polystyrene, and various curing temperatures are used to evaluate their effects on diffusion and precipitation. These effects were directly investigated by performing attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). The diffusivity and curing kinetics experiments are performed to quantify the diffusivity coefficient of epoxy, hardener and thermoplastics, as well as the reaction rate constant of curing epoxy at various temperatures. Finally, mechanical testing and fracture surface imaging were used to quantify the improvements and characterize the toughening mechanism. Further improvement on delamination resistance was studied through the synergistic effect of combining different modification methods without the interleaf. Polysulfone molecules are end-capped with epoxide groups. Fiber surface is functionalized with amino groups to generate micro-mechanical interlocks. The interaction between two individual modifications chemically links the modified semi-interpenetration networks to the improved interfacial strength between fiber and epoxy to. The impact of the additive on the crosslinking density was examined through glass transition temperatures, and the chemical modification was characterized by Raman spectroscopy. Mode I and II fracture tests were performed to quantify the improvement of delamination resistance under pure opening and shear loads. The mechanism of synergistic effect was explained based on the fracture surface morphology and the interactions between the modification methods.

En el plantejament d’aquest treball final de grau s’han establert diversos objectius a assolir. D’entrada, el primer objectiu marcat ha estat la posta en marxa d’un tren de fabricació de films per extrusió dins del marc del Laboratori d’Enginyeria Paperera i Materials Polímers (LEPAMAP) que permeti la producció de films amb un gramatge i espessor considerablement baixos. En segon lloc, produir, desenvolupar i caracteritzar films biodegradables reforçats amb nanosilicats o nanofibres de cel·lulosa. La finalitat d’aquest estudi és desenvolupar materials plàstics d’origen natural i biodegradable amb bones propietats mecàniques, barrera i òptiques a fi de poder substituir els plàstics provinents de fonts fòssils per plàstics biodegradables amb un cost de fabricació competitiu

This paper presents an implementation of the Imperialist Competitive Algorithm (ICA) in optimization of intermediate epoxy adhesive layer which is bonded between two dissimilar strips of material. The recently introduced ICA has demonstrated excellent capabilities such as faster convergence and better global optimum achievement. The results of ICA are finally compared with the Finite Element Method (FEM) and Genetic Algorithm (GA). In application, comparison shows the success of ICA for designing adhesive joints in composite materials.

In the recent years the fused deposition modelling (FDM) became one of the most popular rapid prototyping (RP) techniques. With this method we are able to build a composite object layer-by-layer. However, because only a limited number of materials, such as thermoplastics have been used as a feedstock for FDM, the final products have limited mechanical properties. The fiber reinforcement materials can significantly increase the mechanical properties, such as stiffness and strength, of the final product, especially in the direction of the filament. Nevertheless, the mechanical properties of the final part on the transverse directions still relay on the poor adhesion between filament layers. In this study the main purpose is to investigate the 3D printed object structures and fiber-orientation, and find the best settings in case of carbon fiber reinforced plastic 3D printing. The study also considers the need of the tuning of different manufacturing parameters and the modification of certain parts of the 3D printer to adapt it to the new material configuration. Furthermore this study includes the effect of surface-treatment with acetone at the printed objects in order to improve the transverse mechanical properties of the final parts. To carry out the study, different test specimens will be manufactured according to different manufacturing configurations and the mechanical properties of the material will be characterized by means of different standard tests. In my study to reach the desired quality I will print specimens with several parameters and investigate the effect of the settings to obtain the best setting for the best results. After I reached the proper settings in printing of both materials I printed more than 40 specimens in 3 directions to investigate the effect of the printing direction. Independently from the thickness of the layers the surface of the printed object never will be perfectly smooth. To reach the smooth surface to use acetone vapor as a surface treatment is a feasible way. In my study I would like to examine the effect of acetone, the necessary time for the treatment. After I prepare all of the specimens I can them with a tensile test machine. With this experiment I will be able to obtain the following mechanical properties: tensile stress, Young’s modulus, Yield strength and Poisson ratio

El treball final de grau realitzat es basa en la investigació de les propietats mecàniques, físiques i tèrmiques de dos materials compostos, concretament dos tipus de fusta plàstica utilitzada en la producció de tarimes sintètiques, per a la seva posterior utilització en la construcció. L’objectiu global del treball és estudiar l’aptitud dels dos materials compostos analitzats per a ser utilitzats com a panells de revestiment per a façanes ventilades. Els materials utilitzats en el present treball són dues granses utilitzades en la producció de tarima per exterior a través d’extrusió. Una gransa fabricada per l’empresa AGT, que està formada per un 42% de polipropilè, un 50% de fibres de serradures d’origen divers i un 8% d’additius. I una gransa fabricada per l’empresa Hualong composta per un 35% de polietilè, un 45% de residus de fusta de pollancre, un 10% d’additius i un 10% de carbonat càlcic

Starch is a natural, renewable, sustainable, inexpensive, and degradable material which has many advantages and plays important roles in human life. Starch is also a natural polymer available everywhere in the world. Nanofibrillated cellulose (NFC) is a main material to reinforce and increase the properties of composites such as paper and packaging materials. Both of starch and NFC are degradable materials and environmental friendly. In this study, starch was used as a raw material to produce a flexible, transparent and biodegradable film which was compounded by glycerol, plasticizer, and reinforced by NFC. There were three steps which must be practiced to create such kind of film included pre–blends, blends, and films preparation. Starch, glycerol, glycerol/NFC, and added water were mixed together to obtain the pre–blends. The appropriate proportions of these compositions were found to acquire good pre–blends. For this step, there were 7 formulations to prepare the pre-blends. After that, the ready prepared blends were then passed though Brabender mixing to get the blends. Optimum temperature, rotation speed, and time of mixing were investigated and observed carefully in this step in order to achieve transparent and flexible blends. The process to obtain the blends was named as compounding. Later on, transparent, flexible, and thin thickness films were processed by those prepared blends through thermoforming. To complete these properties of films successfully, the suitable temperature, applied forces/pressures, and times of thermoforming must be rightly determined. After the films were completely obtained, they were then characterized some of their properties. Mechanical characterization, water absorption, water vapor permeability and biodegradability were the properties of films which must be determined. The effects of NFC with different amount of pulp oxidation (5, 10, and 15 mmol) and higher or lower content of fibers added in the created films were studied on these properties. There were 2 conditions, 23oC and 50% RH and 7oC and 50% RH, of mechanical characterization which would be tested as water absorption determination had 3 conditions contained 23oC and 50% RH, 23oC and 75% RH, and 7oC and 50% RH. The samples were taken to a laboratory in Valencia, Spain, to experiment and study the capacity of water vapor barrier. Finally, biodegradability property of films under enzymatic activity was analyzed and evaluated

An extensive research project is currently being carried out at The University of Manitoba, Canada, to develop lightweight glass fiber reinforced plastic (GFRP) poles for use in transmission and distribution networks. In this paper, results from tests involving full-scale tapered GFRP poles with a hollow circular cross section subjected to cantilever bending are presented. The filament winding process was employed to produce the poles using polyester resin reinforced with E-glass fibers. Cantilever bending tests were conducted on twelve full-scale poles up to failure. Test parameters included fiber orientation and number of layers. Extensive theoretical work preceded the test program and a theoretical model was developed for evaluating the failure load. The results to date indicate that the developed theoretical model can predict quite well the ultimate capacity and behavior performance of GFRP poles. This theoretical model was used in this investigation to determine the optimum cross-sectional dimensions for 6.1 m (20 ft) and 18.3 m (60 ft) Class 1 GFRP poles.Key words: transmission and distribution poles, filament winding, fiber-reinforced plastics.

This paper presents the results of an experimental investigation into the effect of the geometry of a trepanning tool on thrust and torque during the drilling of uni-directional glass fibre-reinforced plastic (UD-GFRP) laminates. It is well-known that the most effective way of achieving good quality holes while drilling fibre-reinforced plastics (FRPs) is by reducing the thrust and torque. Therefore, this investigation was aimed at exploring the possibility of reducing the thrust and torque by using the concept of trepanning. The design considerations and development methodology of the trepanning tool are discussed. The appropriate tool geometry has been determined by using statistically planned experiments and analysis. Orthogonal arrays with analysis of means as well as analysis of variance have been used to assess individual factor and interaction effects and their significance levels. The investigations have revealed that the performance of the trepanning tool is superior to that of conventional twist drills in terms of thrust, torque and hole quality. Low production cost and ease of regrinding are its major additional advantages due to its simple geometry. (C) 1999 Elsevier Science S.A. .

Structural engineering report SER 256 | SER-ID SER256

Latticed towers are used in several industrial activities due to the fact that they are a relatively inexpensive and a reliable structure. In places where the maintenance could be an issue, such as cold weather countries, there is an active research activity to develop latticed towers made of new materials such as composites. Currently, in the University of Manitoba a research about developing FRP (fibre reinforced polymers) latticed towers is being carried out by Dr. Dimos Polyzois. Part of this research is to perform a finite element analysis (FEA) of a steel lattice tower in order to be able to compare the behaviour depending on the type of material used. This project has performed a finite element analysis (FEA) of a steel latticed tower. This analysis was made using two types of models (i.e. truss type elements model and beam type elements model). The difference between the results of both models is about the 20%. Several load cases were analysed in order to get a better understanding of the behaviour of the tower. The maximum displacement (388.138 mm) is obtained with ice on the tower and wind angled 30 degrees from the perpendicular of a face. The maximum stress in the tower is about 76.708 MPa and the maximum force of the cables (12.1 kN) is about the 70% of its breaking strength. Outgoing

El objeto principal de este trabajo es diseñar y simular laminados de carbono con tejidos y materiales embebidos que minimicen la fragmentación de estructuras de material compuesto y absorban parte de la energía en impactos de vehículos de competición. Se estudiarán las nuevas propiedades mecánicas del material y serán comparadas con las propiedades originales obtenidas en ensayos de tracción, modal y de carga cuasi-estática.