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Fused deposition modelling is an additive manufacturing technique, classified as one of the most popular 3D manufacturing processes, because of its low cost and easy usability, resulting in good quality products. However, the mechanical properties of manufactured pieces depend on the base material properties, manufacturing parameters, and room conditions (temperature and moisture). For those reasons, to obtain the optimal conditions, three different types of experimental tests were performed: tensile, flexural, and water absorption. These tests were carried out to determine ABS and PLA’s mechanical and physical properties, which are the main materials used in the FDM technique. Results showed that PLA has higher values of tensile and flexural strength comparatively to ABS and on the other hand, ABS had a greater weight of water absorption. The authors acknowledge the financing by Fundação para a Ciência e a Tecnologia (FCT) under the strategic grants UIDB/00690/2020. This research work was also partially funded by EXPL2021CIMO_01. info:eu-repo/semantics/publishedVersion

The high demand for steel and wood as the primary shipbuilding materials will increase market prices due to decreasing supplies each year. To address this issue, new alternative materials that are more environmentally friendly and inexpensive, such as natural fibers like bamboo and coconut fiber, must be explored. This study aimed to investigate how the directional arrangement (0° unidirectional and 90° unidirectional) of laminated Petung bamboo (Dendrocalamus asper) affects the compressive and flexural strength of ship construction. The compressive strength on the X, Y, and Z-axis was measured to determine the laminated beam’s strength ratio on each side. In contrast, the flexural strength was only observed on the Y and Z-axis due to testing equipment limitations. The results showed that the directional arrangement of laminated Petung bamboo with different test axes significantly impacted the compressive and flexural strength of laminated beams made of Petung bamboo and coconut coir fiber. Laminated Petung bamboo and coconut coir fiber with 0° unidirectional fiber had better compressive and flexural strength values than those with 90° unidirectional fiber. Based on the data testing, the combination of Petung bamboo and coconut coir fiber materials can be categorized into different strength classes. These findings have important implications for using laminated bamboo in shipbuilding applications. The use of laminated bamboo with a 0° lamina direction could be recommended for ship components that require high levels of strength than laminated bamboo with a 90° lamina direction.

Recent environmental concern has been raised about the development of biocomposites because of their low cost, eco-friendliness, and biodegradability. Machining of polymeric composite is inevitable during assembly of structural components. In view of creating holes in structural composites, drilling is necessary and it is essential to carry out research to find the optimal machining parameters. The experimental assessment and prediction of the thrust force and torque involved in drilling composites reinforced with sheep horn are presented in this work. The matrix and sheep horn particles were combined in the right proportions before being moulded and poured into a mould, then allowed to cure at room temperature. Investigated properties included ultimate tensile strength, flexural strength, and hardness. To evaluate the quality of the hole, micrographs of the drilled hole were employed. When the mixture was optimised based on the properties, it was found that a 70:30 ratio produced the best results. Thrust force and torque of 58 N and 4.8 N-mm, respectively, were observed for sheep horn filler laminates which were drilled using the combination of 6 mm diameter, 0.1 mm/rev feed rate, and 400 rpm speed. This is by far the best among the combinations used in the experiment. Additionally, the experimental outcomes indicate that the feed rate and spindle speed are the most significant factors affecting the thrust force. Since there were minimal errors in the comparison, the central composite design modelling is consummate. Overall, the extensive experimental effort offers several options to utilise this composite material in future applications across a wide range of fields.

Additive manufacturing (AM) technologies have revolutionized the manufacturing sector due to their benefits, such as design flexibility, ease of operation, and wide material selection. The use of AM in composites production has also become quite popular to leverage these benefits and produce products with customized properties. In this context, thermoplastic materials are widely used in the development of plastic-based composites due to their affordability and availability. In this work, composite plastic manufacturing (CPM) has been used to manufacture plastic-based composites with bespoke properties in a cost- and time-effective manner. Various plastic-based composites have been manufactured using CPM by interlacing acrylonitrile butadiene styrene (ABS) with thermally activated materials. Three different thermally activated materials (graphene–carbon hybrid paste, heat cure epoxy, and graphene epoxy paste) have been used in this work to produce plastic-based composites. Thermally activated materials that are commercially available include graphene–carbon hybrid paste and heat cure epoxy. The graphene epoxy paste was a concoction made by incorporating three different weight percentages of graphene nanoplatelets (0.2 wt.%, 0.4 wt.%, and 0.6 wt.%) with heat cure epoxy. The composites were manufactured with multiple layers of thermally activated materials at different intervals to investigate their effect. The parts were manufactured and tested according to British and international standards. Experimental tests of mass, dimensions, ultrasonics, tensile strength, hardness, and flexural strength were conducted to evaluate the properties of composites manufactured by CPM. The parts manufactured by CPM showed superior mechanical properties compared to commercially available ABS. The increase was shown to be in the range of 8.1% to 33% for tensile strength, 17.8% to 30.2% for hardness, and 6.2% to 24.4% for flexural strength, based on the composite configurations. The results demonstrate that the CPM process can produce high-quality plastic composites and can be used to create products with customized properties in a time-effective manner.

A greener and more sustainable option is proposed to shift the construction paradigm of high embedded carbon values in concrete and the frequency of repairs when it cracks. Using low-carbon concrete with a bacterial self-healing agent can reduce the embedded carbon value while adding value to the structure. This paper aims to evaluate the interaction of a bacterial self-healing agent on the mechanical properties of low-carbon concrete, specifically 50% Ground Granulated Blast-furnace Slag (GGBS) as an Ordinary Portland Cement (OPC) replacement. A range of tests is conducted to test the evolution of mechanical properties throughout the early stages of curing for 7, 14, and 28 days. Such tests included the evaluation of compression, flexural, tensile splitting strength and dynamic elastic modulus. The results of the experiments demonstrate that early stages of GGBS mixes exhibit lower compressive capacity throughout the 28-day mark but also indicate their potential to increase sharply and surpass the control mix values after 28 days. The self-healing agent interacts slightly with the GGBS mixes, further reducing the mechanical properties in the early curing stages. However, GGBS mixes increase sharply after the 28-day mark, with the added benefit of further reducing carbon emissions by extending design life and durability. In theory, the newly developed concrete can seal cracks up to 0.3 mm (up to 0.8 mm if using the maximum dosage) but seal wider cracks from laboratory results. These changes imply that using GGBS as a replacement for OPC is viable for structures that do not require high compressive values in the early curing stages but after the 28-day mark while reducing the carbon emission values substantially, in this case, 40%, or up to 50% if using a self-healing agent. This low-carbon concrete is thus a sustainable and resilient material, especially for retrofitting existing reinforced concrete infrastructure.

Curaua, as a leaf-based natural fiber, appears to be a promising component with aramid fabric reinforcement of hybrid composites. This work deals with the investigation of flexural, impact and elastic properties of non-woven curaua–aramid fabric hybrid epoxy composites. Five configurations of hybrid composites in a curaua non-woven mat with an increasing quantity of layers, up to four layers, were laminated through the conventional hand lay-up method. The proposed configurations were idealized with at least 60 wt% reinforcement in the non-alternating configuration. As a result, it was observed that the flexural strength decreased by 33% and the flexural modulus by 56%. In addition, the energy absorbed in the Charpy impact also decreased in the same proportion as the replaced amount of aramid. Through the impulse excitation technique, it was possible observe that the replacement of the aramid layers with the curaua layers resulted in decreased elastic properties. However, reduction maps revealed proportional advantages in hybridizing the curaua with the aramid fiber. Moreover, the hybrid composite produced an almost continuous and homogeneous material, reducing the possibility of delamination and transverse deformation, which revealed an impact-resistant performance.

Prestressed, precast concrete piles using High-Strength Steel Strands (PPCPs using HSSS) are a new type of precast pile. Compared with prestressed high-strength concrete (PHC) piles, the adoption of ultra-high-strength concrete and HSSS not only improves the load-bearing capacity, but also enhances the ductility of precast piles. The engineering application of PPCPs using HSSS requires not only a high bearing capacity of the pile segments, but also reliable splicing to ensure cooperation between pile segments. Based on the characteristics of strand anchorage plates, this paper proposes a new combination splice using the clamp ring and welding (Combination Splice). The theoretical analysis and design method of this Combination Splice is introduced. This research gives a thorough investigation into the flexural performance of PPCPs using HSSS with the Combination Splice. The flexural tests of PPCPs using HSSS with the Combination Splice were firstly conducted on eight full-scale pile specimens with three different pile diameters and four different steel reinforcement ratios. The flexural performances are evaluated in terms of crack resistance, flexural capacities, crack distribution, as well as strain development. The results indicate that the Combination Splice remain safe and intact when the piles reach the ultimate bending capacity. The ultimate bending moment of tested specimens with the Combination Splice is, on average, 10% larger than that of specimens using a theoretical formula. In light of the experimental data, a finite element analysis (FEA) model has been created to simulate the flexural performance of the piles with the Combination Splice. The FEA results show that the load–displacement curves and crack distribution regions are in good agreement with the experimental findings, which verifies the reliability and accuracy of the FEA model. The parameter analysis investigates the effects of the assembly gap and clamp ring corrosion on the flexural performance of PPCPs using HSSS. The results show that assembly gaps have a greater influence on the flexural capacity and deformation, while the influence of the clamp ring corrosion is negligible, indicating that the Combination Splice has certain advantages in terms of durability.

Precast concrete bridge structures have been extensively used because of the mature construction techniques, fast construction, and their economy. Considerable practical applications, however, present certain disadvantages, such as cracking and water infiltration in their normal strength concrete (NSC, compressive strength 40 MPa) joints connecting prefabricated deck panels. Ultra-high performance fiber reinforced concrete (UHPFRC, compressive strength 143 MPa) has been proven highly effective in replacing the conventional cementitious grout materials in precast bridge structures. In the present study, three types of UHPFRC connections, rectangular, zigzag-shaped, and diamond-shaped, were experimentally evaluated on their flexural capacities, interface bonding performances, and failure modes through four-point bending tests (loading rate 0.1 kN/s). The results showed that all the UHPFRC connections exhibited apparently higher flexural capacities than an intact precast NSC member and had such strong UHPFRC-NSC interfacial bonding that the interfacial first-crack strengths were not less than the NSC member. Having the capability of modeling the UHPFRC connections and their interface properties, the developed finite element (FE) models of the precast slabs with UHPFRC connections produce numerical results in good agreement with the flexural tests. By means of the FE models, parametric investigations were carried out to make suggestions on optimizing the UHPFRC connection designs for practical use.

Reinforcement corrosion poses a great threat to the safety of reinforced concrete structures, and the fiber-reinforced polymer is the ideal material to partially replace steel bars due to the high strength, light weight and good durability. However, the selection of appropriate fiber materials and a reasonable ratio of fiber bar to steel bar is not clear. Here, we measured the mechanical properties of fiber bars containing aramid fiber and carbon fiber. The deflection deformation, crack distribution and maximum crack width of the concrete upon various loads were experimentally and theoretically investigated. The predictions of the maximum crack width and deflection of reinforced concrete beams under various loads were proposed in ACI standard, which may provide guidance for further applications of fiber-belt-bar-containing concrete beams.

The increase in world population has led to a significant increase in the numbers of cars and used tyres. These tyres must be disposed of on an ongoing basis as a result of their consumption or deterioration. This can result in negative effects on the environment that must be preserved, especially from those materials, i.e., these waste materials are difficult to dispose of without special treatments. Hence, extensive experimental investigations and numerical simulations need to be conducted to use and recycle these wastes by exploring the possibility of using them as alternative ingredients in construction materials. For example, waste rubber pieces can be used as one of the main components of concrete. In this study, the main aim was to numerically simulate the flexural behaviours of rubberised concrete under the influence of an applied vertical loading with different contents of added rubbers by using the commercial finite element software ANSYS. The obtained numerical results were compared with the experimental results of a previous study and showed a good agreement with the deflections and moduli of rupture, with the variances from 2–7% in the deflections. However, the differences in the moduli of rupture varied between 5% and 9%. Finally, the statistical analyses indicated that these numerical mean values and standard deviations were acceptable and were very close to the experimental values.

This research investigated the flexural behavior of high-strength steel (HSS)—concrete composite beams. The effect of concrete strength on the load-deflection behavior, flexural capacity, and ductility of HSS—concrete composite beams was investigated. Four full-scale HSS—concrete composite beam specimens were tested under static load. The test results demonstrate that the failure mode of HSS—concrete composite beams is flexural failure of the steel member and compression fracture of concrete at mid-span. The HSS—concrete composite beam exhibits good mechanical performance and deformation behavior. The ultimate bending strength and ductility of HSS—concrete composite beams were improved with the increased concrete strength. The theoretical results demonstrate that the simplified plastic method overestimates the ultimate bending strength of HSS—concrete composite beams. The main reason is that only a small part of the steel beam bottom shows plastic strengthening, which is not enough to make up for the strength loss caused by the steel near the neutral axis failure to yield and the relative interface slip. The nonlinear method based on material constitutive model could predict the load-bearing capacity accurately. After analyzing the ultimate bending capacity of 192 sample beams, the simplified plastic method was modified, and the theoretical method for ultimate bearing capacity of HSS—concrete composite beams was proposed.

Preferably in testing, building structures need not be destroyed. Tests that can be used on the concrete can use non-destructive methods that do not damage the test objects. Examples of testing can use UPV tests that are aimed at knowing the quality of concrete from the pulse velocity . The test objects used in this study are reinforced concrete beams with dimensions 20 x 20 x 100 cm. T est objects are differentiated into 3 quality variations of reinforced concrete with quality of concrete 12.5 MPa, 18.75 MPa, and 25 MPa. To conduct analysis of the concrete density used PUNDIT PL-200. Ultrasonic pulse velocity into parameters on this test. From the results of the tests, there are differences in the value of different coefficient of the R 2 determination. Acquired coefficient value of determination R 2 = 0.9076 in direct method. The coefficient value of determination R 2 = 0.8718 in the semi-direct method. C oefficient value of determination R 2 = 0.3042 at Indirect Method 2 point, and in indirect method 3 point the coefficient value of determination R 2 = 0.7524. From this research also obtained comparisons between the three methods, namely between the direct method and the semi-direct method, direct method and indirect method, also semi-direct method and indirect method.

Steel reinforced grout (SRG) retrofitting systems represent a suitable technique to increase the performances of reinforced concrete (RC) structures, in particular for structural elements subjected to flexure. They can be applied even to wet surfaces and they feature a better fire resistance with respect to Fiber-Reinforced Polymer (FRP) composites. Nevertheless, the failure mode of strengthened elements can be similar to that of FRPs, i.e. debonding of the externally bonded reinforcement, especially if several layers of composite reinforcement are applied to the RC element. Different studies can be found addressing the problem of bond between SRG and RC or masonry substrates, but only few of them analyzed the bond performance when multiple layers are considered. To this purpose, the present paper presents the results of an experimental campaign focused on this specific key-aspect of the bond behavior, i.e. when multiple SRG layers are considered. Single-lap shear tests were carried out on concrete prisms strengthened by a single or multiple SRG layers, addressing the differences in terms of bond behavior and failure modes. In addition, monotonic and cyclic loading were considered in order to verify the possible bond degradation when applying high amplitude cycles; results of the cyclic loading tests were compared with those from monotonic tests on single or multiple SRG layers with the same amount of reinforcement. Flexural tests were carried out on full-scale RC beams strengthened with multiple plies of SRG reinforcement, without mechanical anchorages. Beams were subjected to either monotonic or cyclic loading. Tests were carried out under displacement control in order to properly characterize the non-linear behavior, evaluating the effect of composite reinforcement in terms of failure mode and ductility. The comparison between both small (single-lap) and full-scale (beams) tests allows to investigate the applicability of the bond relationship developed at small scale to structural elements and to evaluate the possible limits of small-scale testing.

This study aimed to understand the mechanical and interfacial properties of fiber-reinforced geopolymer (FRG) layer on the tension zone of normal concrete. A trial mix of FRG using local materials obtained in Hokkaido was investigated. Compression and splitting tensile tests on the FRG test pieces were conducted under different mixing procedures, constituents, volume fractions of the polyvinyl alcohol fiber, curing conditions, and ages. Flexural tests using FRG-normal strength concrete (NSC) composite specimens with different FRG layer thick-nesses were carried out. By placing the FRG layer on the tension side of the composite specimen, the flexural strength and energy absorption were significantly increased. The flexural strength for the NSC alone was 3.5 MPa, while the FRG-NSC composite specimens showed higher flexural strengths of 6.1-6.6 MPa. Also, XRD, FTIR, and SEM analyses were carried out for the FRG samples.

Carbon fiber-reinforced composites represent a broadly utilized class of materials in aeronautical applications, due to their high-performance capability. The studied CFRP is manufactured from a 3K carbon biaxial fabric 0°/90° with high tensile resistance, reinforced with high-performance thermoset molding epoxy vinyl ester resin. The macroscale experimental characterization has constituted the subject of various studies, with the scope of assessing overall structural performance. This study, on the other hand, aims at evaluating the mesoscopic mechanical behavior of a single-ply CFRP, by utilizing tensile test specimens with an average experimental study area of only 3 cm2. The single-ply tensile testing was accomplished using a small scale custom-made uniaxial testing device, powered by a stepper motor, with measurements recorded by two 5-megapixel cameras of the DIC Q400 system, mounted on a Leica M125 digital stereo microscope. The single-ply testing results illustrated the orthotropic nature of the CFRP and turned out to be in close correlation with the multi-ply CFRP tensile and bending tests, resulting in a comprehensive material characterization. The results obtained for the multi-ply tensile and flexural characteristics are adequate in terms of CFRP expectations, having a satisfactory precision. The results have been evaluated using a broad experimental approach, consisting of the Dantec Q400 standard digital image correlation system, facilitating the determination of Poisson’s ratio, correlated with the measurements obtained from the INSTRON 8801 servo hydraulic testing system’s load cell, for a segment of the tensile and flexural characteristics determination. Finite element analyses were realized to reproduce the tensile and flexural test conditions, based on the experimentally determined stress–strain evolution of the material. The FEA results match very well with the experimental results, and thus will constitute the basis for further FEA analyses of aeronautic structures.

The European steel industry produces about 70 million tons/year of steel by the electric arc furnace (EAF). The slag consists of about 15% by weight of the produced steel, thus from the perspective of the circular economy, it has a high potential as a co-product. This research aims to assess an innovative reuse of EAF slag as filler in different polymer matrixes: thermoplastic (polypropylene), thermosetting (epoxy resin), elastomeric (nitrile butadiene rubber), and recycled end of life rubber tire. A comparison between neat polymer and polymer filled with a certain amount of EAF slag has been carried out by tensile (or flexural), compression, and hardness tests. Experimental results show that slag as a filler increases the composites’ hardness and elastic modulus at the expense of toughness. For a safe reuse of the slag, the leaching of hazardous elements must comply with current legislation. It was found that, although the used EAF slag releases small amounts of Cr, Mo, and V, incorporating it into a polymer matrix reduces the leaching. The EAF slag particles distribution has been observed by scanning electron microscopy (SEM) images. The obtained results show good technical feasibility of this innovative slag application so that it could pave the way to a new industrial symbiosis between dissimilar sectors, bringing economic and environmental benefits.

V diplomski nalogi smo najprej opravili pregled literature kompozitnih materialov in veziv za popravilo čevljev za smučarske skoke. Opisan je postopek popravila z izboljšavo lastnosti smučarskega čevlja v pregibu, s čimer ne podaljšamo le življenjske dobe čevlja, ampak omogočimo skakalcu tudi boljši občutek v vseh fazah skoka. Po dolgotrajni uporabi pa se na pregibu v kompozitu pojavljajo delaminacije in razpoke, ki so posledica nizke oprijemne trdnosti med plastmi. Na podlagi literature o kompozitnih materialih, tkaninah in njihovih površinskih obdelavah, ki omogočijo večjo oprijemno trdnost med plastmi smo izbrali dve vrsti steklenih tkanin (platno, keper) in ju primerjali glede trdnosti in kakovosti adhezijskega oprijema s strižnimi in upogibnimi preizkusi ter z mikrostrukturno analizo porušenih standardnih vzorcev. Na osnovi rezultatov in analiz smo ugotovili, da so vlakna s keper pletenjem bolj primerna za popravilo, saj se ob manjši razslojitvi predvideva tudi kasnejša obraba kompozita zaradi zunanjih vplivov, predvsem vlage, ki je stalno prisotna na ojačanem delu. In the diploma thesis, the literature review of composite materials and binders for the repair of ski boots with reinforcement of the bend was made. The repair process leads to improvement of the properties of the ski boot in the bend section, which not only prolongs the life-span of the boot, but also allows for a better feel during all phases of jump. After a long-term use, delaminations and cracks appear on the bend, which are the result of low inter-laminar strength between the layers. Aim of the research was evaluate different type of fabrics which would yield to a higher quality of material. A review of the literature on composite materials, fabrics, and their surface treatments, which provide greater grip strength between layers, was performed. We selected and compared the strength and quality of the adhesion of two types of glass fabrics (plain, twill) using shear and bending test, followed by microscopy of failed specimens. Based on the results and analyzes, we found that the fibers with twill knitting are more suitable for repair, as with less stratification, later wear of the composite due to external influences, especially moisture, which is constantly present on the reinforced part.

Epoxy resins, due to their high stiffness, ease of processing, good heat, and chemical resistance obtained from cross-linked structures, have found applications in electronics, adhesives coatings, industrial tooling, and aeronautic and automotive industries. These resins are inherently brittle, which has limited their further application. The emphasis of this study is to improve the properties of the epoxy resin with a low-concentration (up to 0.4% by weight) addition of Multi-Walled Carbon Nanotubes (MWCNTs). Mechanical characterization of the modified composites was conducted to study the effect of MWCNTs infusion in the epoxy resin. Nanocomposites samples showed significantly higher tensile strength and fracture toughness compared to pure epoxy samples. The morphological studies of the modified composites were studied using Scanning Electron Microscopy (SEM).

Utilization of advanced engineering thermoplastic materials in fused filament fabrication (FFF) 3D printing process is critical in expanding additive manufacturing (AM) applications. Polypropylene (PP) is a widely used thermoplastic material, while silicon dioxide (SiO2) nanoparticles (NPs), which can be found in many living organisms, are commonly employed as fillers in polymers to improve their mechanical properties and processability. In this work, PP/SiO2 nanocomposite filaments at various concentrations were developed following a melt mixing extrusion process, and used for FFF 3D printing of specimens’ characterization according to international standards. Tensile, flexural, impact, microhardness, and dynamic mechanical analysis (DMA) tests were conducted to determine the effect of the nanofiller loading on the mechanical and viscoelastic properties of the polymer matrix. Scanning electron microscopy (SEM), Raman spectroscopy and atomic force microscopy (AFM) were performed for microstructural analysis, and finally melt flow index (MFI) tests were conducted to assess the melt rheological properties. An improvement in the mechanical performance was observed for silica loading up to 2.0 wt.%, while 4.0 wt.% was a potential threshold revealing processability challenges. Overall, PP/SiO2 nanocomposites could be ideal candidates for advanced 3D printing engineering applications towards structural plastic components with enhanced mechanical performance.

This study studied the flexural performance of HSC one-way reinforced concrete slab reinforced with BFRP bars. The study incorporated experimental examination and Non-linear finite element study for seven BFRP concrete slabs had dimensions 700 × 1700 mm with a thickness 120 mm and 140 mm. The experimental test results showed that the ultimate flexural loads and behavior of concrete slabs reinforced with BFRP were improved compared with concrete slabs reinforced with steel reinforcement. Also, the tensile strength of BFRP bar is 2.5 times greater than the yield strength of steel reinforcement and 1.79 times greater than the tensile strength of bar. The structural behavior of the tested slabs was validated with the theoretical developing a finite element models utilize software ANSYS 2019-R1 program. Good agreement between the numerical and experimental results in first cracking loads, load-carrying capacity, crack pattern and deflections were found. The agreement between the experimental load carrying capacity and NLFE ones is about 89.0 % with coefficient of variance equals 0.001 and standard deviation of 0.03. The finite element analysis gave suitable guessing for the structural performance of the nonlinear BFRP concrete slab.

Extending service life and preventing demolition of existing structures are the primary goals of structural strengthening and rehabilitation. Fiber-reinforced polymer (FRP) composites have been the most common type of composite in the realm of structural strengthening applications. In recent years, as a new type of composite, epoxy is replaced by an inorganic matrix, named fiber reinforced cementitious mortar (FRCM), and have attracted a great deal of interest among researchers. Focusing of these kind of novel composites, this paper tries to find a connection between FRCM composites behaviour, as their maximum fiber strain, in flexural and direct shear tests. To achieve this goal, a cross section analysis of previous research works on strengthened RC beams with one layer of composites was conducted and the maximum strain of the fibers was obtained. Calculated fiber strains in flexural strengthening specimens compared with corresponding measured maximum fiber strains in direct shear test specimens. Comparison of results show that the average of maximum fiber strain obtained from flexural specimens is in good agreement with corresponding one measured in direct shear test specimens. Consequently, maximum fiber strains could be designated as the lost link between flexural and direct shear tests as two separated part of a chain.

Polypropylene (PP) is an engineered thermoplastic polymer widely used in various applications. This work aims to enhance the properties of PP with the introduction of titanium dioxide (TiO2) nanoparticles (NPs) as nanofillers. Novel nanocomposite filaments were produced at 0.5, 1, 2, and 4 wt.% filler concentrations, following a melt mixing extrusion process. These filaments were then fed to a commercially available fused filament fabrication (FFF) 3D printer for the preparation of specimens, to be assessed for their mechanical, viscoelastic, physicochemical, and fractographic properties, according to international standards. Tensile, flexural, impact, and microhardness tests, as well as dynamic mechanical analysis (DMA), Raman, scanning electron microscopy (SEM), melt flow volume index (MVR), and atomic force microscopy (AFM), were conducted, to fully characterize the filler concentration effect on the 3D printed nanocomposite material properties. The results revealed an improvement in the nanocomposites properties, with the increase of the filler amount, while the microstructural effect and processability of the material was not significantly affected, which is important for the possible industrialization of the reported protocol. This work showed that PP/TiO2 can be a novel nanocomposite system in AM applications that the polymer industry can benefit from.

The continuous demand for thermoplastic polymers in a great variety of applications, combined with an urgent need to minimize the quantity of waste for a balanced energy-from-waste strategy, has led to increasing scientific interest in developing new recycling processes for plastic products. Glycol-modified polyethylene terephthalate (PETG) is known to have some enhanced properties as compared to polyethylene terephthalate (PET) homopolymer, this has recently attracted the interest from the fused filament fabrication (FFF) three-dimensional (3D) printing community. PET has shown a reduced ability for repeated recycling through traditional processes. Herein, we demonstrate the potential for using recycled PETG in consecutive 3D printing manufacturing processes. Distributed recycling additive manufacturing (DRAM)-oriented equipment was chosen in order to test the mechanical and thermal response of PETG material in continuous recycling processes. Tensile, flexure, impact strength, and Vickers micro-hardness tests were carried out for six (6) cycles of recycling. Finally, Raman spectroscopy as well as thermal and morphological analyses via scanning electron microscopy (SEM) fractography were carried out. In general, the results revealed a minor knockdown effect on the mechanical properties as well as the thermal properties of PETG following the process proposed herein, even after six rounds of recycling.

Made available in DSpace on 2022-04-28T19:42:45Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-01-01 Carbon fiber fabrics have been largely used in composite structures as they provide high mechanical strength and potential weigh reduction, allowing more efficiency in product design. However, the production of the parts generates scraps that is discarded as a waste, becoming a challenge to recycle the carbon fiber with predictable mechanical strength. Within this context, this research analyzed strategies of laying up carbon woven fabrics based scraps, in order to reach a desirable mechanical properties in bending loading. Three types of laminates were manufactured using varied fabric size and number of discontinuities in the layup combined with polyethylene terephthalate (PET) film as a matrix. The obtained composites were tested under four-point-bending test and an energy-strength based analysis was conducted. This analysis explained a strategic position of fabric scrap to maximize the bending strength: providing a value of 106.33 MPa for a composite with high number of discontinuities against 83.11 MPa for another with less discontinuity. Departamento de Engenharia Ambiental Instituto de Ciência e Tecnologia Universidade Estadual Paulista (UNESP) Praça Marechal do Ar Eduardo Gomes Instituto Tecnológico da Aeronáutica Departamento de Engenharia Ambiental Instituto de Ciência e Tecnologia Universidade Estadual Paulista (UNESP)

The scope of this work was to create, with melt mixing compounding process, novel nanocomposite filaments with enhanced properties that industry can benefit from, using commercially available materials, to enhance the performance of three-dimensional (3D) printed structures fabricated via fused filament fabrication (FFF) process. Silicon Dioxide (SiO2) nanoparticles (NPs) were selected as fillers for a polylactic acid (PLA) thermoplastic matrix at various weight % (wt.%) concentrations, namely, 0.5, 1.0, 2.0 and 4.0 wt.%. Tensile, flexural and impact test specimens were 3D printed and tested according to international standards and their Vickers microhardness was also examined. It was proven that SiO2 filler enhanced the overall strength at concentrations up to 1 wt.%, compared to pure PLA. Atomic force microscopy (AFM) was employed to investigate the produced nanocomposite extruded filaments roughness. Raman spectroscopy was performed for the 3D printed nanocomposites to verify the polymer nanocomposite structure, while thermogravimetric analysis (TGA) revealed the 3D printed samples’ thermal stability. Scanning electron microscopy (SEM) was carried out for the interlayer fusion and fractography morphological characterization of the specimens. Finally, the antibacterial properties of the produced nanocomposites were investigated with a screening process, to evaluate their performance against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus).

Journal of Metals, Materials and Minerals, 31, 1, 73-80

Synthetic sapphire is known for its high strength. Indeed, only diamond is susceptible to scratch it. Therefore, colourless sapphires are used as scratch-resistant Swiss watch glasses. In order to minimize shard appearance on watches, RSA Le Rubis, French sapphire manufacturer, wishes to improve its product mechanical property knowledge. How fracture strength fluctuates according to elaboration conditions, and the part of structural defects in this.Clockmaking sapphires are mainly grown at R.S.A. by historical Verneuil process or Edge-defined Fed-film Growth (EFG). Several growth conditions are studied in both processes, such as crystals size and position in the oven, or component ageing.Further, two flexural tests have been designed and massively performed : four point bending and ball on three balls test. Both show a higher flexural strength for Verneuil crystals compared to EFG ones. Transition between elastic and plastic deformation was also studied through nano-indentation pop-in analysis.X-ray characterisations at the European Synchrotron Radiation Facility (ESRF) helped mechanical results understanding by revealing structural defects in crystals. White beam topography and Rocking Curve Imaging were used, as they are complementary.It appears that Verneuil crystals high flexural strength is due to higher dislocation densities, about one hundredth more than in EFG crystals. Dislocation formation results from temperature gradient variation during growth. Higher fluctuation in Verneuil process lead to higher dislocations density., Le saphir synthétique incolore, d'une grande dureté, est notamment utilisé pour la production de glaces de montres in-rayables. La société RSA le Rubis, fournisseur de plusieurs horlogers suisses, souhaite améliorer sa connaissance du comportement mécanique des cristaux, pour limiter le risque de rupture sur le produit fini. Pour cela, il est nécessaire d'approfondir le lien entre la résistance à la rupture des saphirs, leurs conditions d'élaboration et leurs qualités cristallines.Cette étude porte sur deux procédés de fabrication, Verneuil et EFG (Edge-defined Fed-film Growth), majoritairement utilisés pour la production des cristaux pour glaces de montres. Plusieurs conditions de croissance sont étudiées au sein de chacun, telles que la dimension des cristaux, leur positionnement dans le four, ou encore le vieillissement de certains éléments.Les deux dispositifs de flexion imaginés et conçus pour étudier la rupture (la flexion quatre points, et la flexion bille sur trois billes), ont permis de révéler entre autres une meilleure résistance à la rupture des cristaux Verneuil par rapport à ceux obtenus par la méthode EFG. Des essais de nano-indentation ont également permis d'étudier le début de la plasticité dans les cristaux à travers une analyse des pop-ins.Afin de comprendre ces différences de comportements, des caractérisations structurales des cristaux ont été menées à l'ESRF (European Synchrotron Radiation Facility), en topographie en lumière blanche, et en Rocking Curve Imaging.Ainsi, il apparaît que la densité de dislocations cent fois plus élevée dans les cristaux Verneuil permet à ces cristaux d'accommoder une plus grande contrainte avant de rompre. Cette forte densité de dislocations est liée aux gradients de température dont les variations sont plus importantes dans les fours de cristallisation Verneuil.

As one of the largest environmental offenders, the construction industry is a prime candidate for the application of the principles of sustainability. Sustainability could be achieved by using environment friendly materials and structural systems in construction industry. This paper aimed to study using geopolymer concrete as a structural board in constructing insulation sandwich panels under different types of loading. Four compression tests were performed on wall specimens in order to study the behavior of the panels under vertical in plane forces. Axial capacity prediction of wall panels was discussed using four published design equations. Eight one-way slab sandwich panels specimens were tested under flexure loading with different shear span ratios in order to compare the flexural behavior of conventional concrete and geopolymer concrete sandwich panels. The capacities of the slab panels were estimated using the conventional concrete codes provisions and compared to the experimental values. Geopolymer sandwich panels approved its ability to sustain different type of loading in the same manner as that of conventional concrete. A prototype was constructed to assess the constructability and the construction cost of the proposed system. The lack of production lines of geopolymer ingredients increases the material cost. On the other hand, the calculated total cost for different construction systems revealed that the labor cost is lower for the cast in place structural insulated panels CIP-SIP system.

Ultra-high performance fibre reinforced concrete (UHPFRC) is an innovative cement-based engineering material. The mechanical properties of UHPFRC not only depend on the properties of the concrete matrix and fibres, but also depend on the interaction between these two components. The fibre distribution is affected by many factors and previous researchers had developed different approaches to test the fibre distribution. This research adopted the non-destructive C-shape ferromagnetic probe inductive test and investigated the straight steel fibre distribution of the UHPFRC plate. A simplified characterization equation is introduced with an attenuation factor to consider the different plate thicknesses. The effective testing depth of this probe was tested to be 24 mm. By applying this method, fibre volume content and the fibre orientation angle can be calibrated for the entire plate. The fibre volume content generally fulfilled the design requirement. The fibre orientation angle followed a normal distribution, with a mean value of 45.60&deg, By testing small flexural specimens cut from the plates, it was found out that the mechanical performance (peak flexural strength) correlates with the product of fibre volume content and cosine fibre orientation angle.

This study experimentally investigated the flexural fatigue behaviors of honeycomb sandwich composites subjected to low velocity impact damage by considering the type and thickness of the face sheet material, the cell size and the core height parameters. Carbon-fiber reinforced composite and the aluminum alloy was used as the face sheet material. First, the static strength of undamaged and damaged specimens was determined by three-point bending loads. Secondly, the fatigue behaviors of the damaged and undamaged specimens were determined. Low velocity impact damage decreased the flexural strength and fatigue lives but increased the damping ratio for all specimens. Maximum damping ratio values were observed on specimens with a aluminum face sheet.

The aspects regarding the stiffness of the connections between the beams that support the storage pallets and the uprights is very important in the analysis of the displacements and stresses in the storage racking systems. The main purpose of this paper is to study the effects of both upright thickness and tab connector type on the rotational stiffness and on the capable bending moment of the connection. For this purpose, a number of 18 different groups of beam-connector-upright assemblies are prepared by combining three types of beams (different sizes of the box cross section), three kinds of uprights profiles (with a different thickness of the section walls), and two types of connectors (four-tab connectors and five-tab connectors). Flexural tests were carried out on 101 assemblies. For the assemblies containing the uprights having the thickness of 1.5 mm, the five-tab connector leads to a higher value of the capable moment and higher rotational stiffness than similar assemblies with four-tab connectors. A contrary phenomenon happens in case of the assemblies containing the upright profiles having a thickness of 2.0 mm regarding the capable design moment. It is shown how the safety coefficient of connection depends on both the rotational stiffness and capable bending moment.

The study aims to develop a new approach of concrete tensile strength test characteristic by minimizing the traditional drawbacks such as load eccentricity, stress or strain non-uniformity and stress concentration in traditional test methods and of a distinguished gauge region which undergoes uniform tensile stress so the determination of the tensile stress-strain curve is simplified contrariwise of traditional methods. The elementary configuration of biaxial stress state is normalized into introduced model configuration under the effect of identical internal forces of specific alignment laid within specific compression and tension elements likewise a strut–tie model. Experimental program is considered to investigate the introduced model, flexural and Brazilian splitting tests are conducted to confirm its reliability. The obtained results are quite converged and show that the tensile strength determined by the proposed model is clearly higher than that of the Brazilian test with closer deviation and lower than that of the flexural test. Unique and sudden fracture is observed within assigned gauge length and led to separation of failed specimens without any deformation associated with loading mechanism.

Xylotrechus arvicola is an insect pest on Vitis vinifera in the main wine-producing regions of Spain. X. arvicola larvae bore inside grapevine wood, which cause structural damages in the plants´ biomechanical properties. Grapevine wood affected and unaffected by larvae, were collected from vineyards. Compression and flexural tests were used to quantify biomechanical wood properties. Affected wood broke more quickly and endured a lower supported force than unaffected wood in both varieties and moisture states. Tempranillo was the most resistant variety on trunks, while Cabernet-Sauvignon was the most resistant variety on branches, where all infested varieties showed a lower rate of bending. Grapevine wood affected by X. arvicola larvae shows an important decrease in its resistance in both moisture states - dry and wet wood - and it is observed due to the faster break in time and a lower supported force. These damages give the affected wood greater sensitivity to external mechanical factors in the vineyards, such as strong winds, harvest weight and the vibration exerted by harvesting machines. The aspect of stress-time curves in all cases follow similar patterns, so in future studies might be possible to stablish relationships between both wet and dry samples and different infestation levels.

Fabric-reinforced cementitious matrix (FCRMs) are composites that produce lighter and more durable strengthening solutions. In this study, carbon and basalt fabrics were used to manufactured FRCM plate specimens. These plates were subjected to a centered punctual load with different punch diameters. Flexural failure mode was observed. Experimental tests showed that carbon and basalt fabrics improved notably the load capacity and the stiffness of mortar plates compared to unreinforced ones. Moreover, failure in the reinforced plates was progressive, preventing the sudden brittle failure of the unreinforced ones. Analytical and numerical models were adjusted and validated from experimental results, and both have proved to be effective calculation tools. What is more, numerical model allowed to determine a sliding tensile stress for the carbon fabric used in this study. 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.

Debonding of fiber-reinforced composites can limit the increase of strength that a reinforced concrete (RC) beam can achieve due to the addition of the external layer of reinforcement provided by the composite. Small-scale direct shear tests can help understand the debonding phenomenon. However, researchers have debated for decades whether the results of direct shear tests can be used to predict the strain level at which the composite would fail in strengthened beams. This paper is the first systematic attempt to address this issue. A database of RC beam flexural tests and of direct shear tests that feature externally bonded polypara-phenylene-benzo-bisoxazole (PBO) fiber-reinforced cementitious matrix (FRCM) composite is compiled. For the beam tests, two methods are employed to determine the strain in the composite at failure due to debonding, referred to herein as the cross-sectional analysis method and the ΔM method, and the results are compared with those of direct shear tests. The relationship between the effective strain in the FRCM when composite action is lost and the debonding strain in direct shear tests is critically discussed taking into account what is prescribed by current design guidelines. The limitations of the cross-sectional analysis method to determine the effective strain are also highlighted.

The objective of this work is the production and characterization of glass-ceramic with recycled glass powder and 4% (w/w) of cerium dioxide. Eleven groups were defined with conformation pressure of 11.6 and 25.8 MPa, and cerium dioxide addition. The sintering temperatures of 650, 675, 700 and 750 °C were used. The raw material was formed into a mold with a uniaxial pressure. The density was measured by the Archimedes principle. The water absorption of the groups was also determined, as linear contraction percentage and the crystalline structure. The flexural strength was obtained by the three-point bending test and the results analyzed by the Weibull analysis. The specimens presented density ranging from 1.99 to 2.38 g/cm3. Increasing the temperature provided an increase in the density of the specimens and the flexural strength. At higher sintering temperature, this behavior was not observed. The highest flexural strength was 63.55 MPa, obtained at the sintering temperature of 700 oC, conformed with 25.8 MPa, only glass powder. The increase in the forming pressure favored crystallization. The addition of cerium dioxide favored for the increase density and the Weibull modulus, but decrease of the flexural strength. Keywords: Glass-ceramic, Flexural Test, Weibull Analysis, Wasted Glass recycling and Cerium Dioxide.

The current analysis examines the efficiency of a composite with polymer matrix reinforced with carbon fibre and graphene at the micro and nano level respectively as an alternative material for aluminium components of Orthotic callipers. An attempt has been made to use both the carbon fibre and graphene as hybrid reinforcement with the matrix as epoxy resin. The addition of graphene and carbon fibre was 2% and 10% respectively by weight of epoxy. Dispersion of graphene was carried out using an ultrasonic sonicator and carbon fibres were a reinforced using hand lay-up technique. The total fabrication was carried out under vacuum to ensure void-free test samples. The samples were tested under tension and 3 Point Bending condition to estimate the Tensile and Flexural properties, under permissible load and deflection criteria. The results found were then compared with presently used material for orthotic callipers extensively used by amputees suffering from the locomotive, gait issues, and polio-affected survivors. The proposed composite showed higher strength, lower deformation and higher stiffness with a lower weight-to-volume ratio as compared to presently used material, i.e. aluminium.

In this study, a new weaving technology with a modified heddle position system based on a self-built three-dimensional (3D) weaving loom is designed, and four typical 3D woven-structure textile groups are manufactured: layer-to-layer orthogonal weaving, through-thickness orthogonal weaving, layer-to-layer angle-interlock weaving, and through-thickness angle-interlock weaving. The new weaving technology has great potential for manufacturing various 3D woven structures effectively and efficiently. The fabricated 3D woven textile-reinforced epoxy-resin composites undergo quasi-static three-point bending tests to study the influence of the woven structure on the flexural performance and failure modes along the textile warp and weft directions. The composites along the weft direction (weft-direction beams) have a larger flexural modulus but smaller failure strain compared with the warp direction (warp-direction beams) for all woven-structure types. Among the designed 3D textile composites, the angle-interlock woven structures have a larger flexural strength (50%), modulus (40%), and failure resistance than have the orthogonal-woven structures. Overall, the through-thickness angle-interlock woven structure has the best flexural-failure resistance among all textile structures, and is the optimal structural design based on this modified weaving technology.

In this study, nanocomposites were fabricated with polycarbonate (PC) as the matrix material. Cellulose Nanofiber (CNF) at low filler loadings (0.5 wt.% and 1.0 wt.%) was used as the filler. Samples were produced using melt mixing extrusion with the Fused Filament Fabrication (FFF) process. The optimum 3D-printing parameters were experimentally determined and the required specimens for each tested material were manufactured using FFF 3D printing. Tests conducted for mechanical performance were tensile, flexural, impact, and Dynamic Mechanical Analysis (DMA) tests, while images of the side and the fracture area of the specimens were acquired using Scanning Electron Microscopy (SEM), aiming to determine the morphology of the specimens and the fracture mechanism. It was concluded that the filler’s ratio addition of 0.5 wt.% created the optimum performance when compared to pure PC and PC CNF 1.0 wt.% nanocomposite material.

Lime is among the binding agents used in binding masonry units, such as brick, in many historical buildings around the world. Its physical strength, mechanical strength, and durability properties, as well as its raw material composition, can play substantial roles in the structural behavior of historic buildings. The production technologies may also differ according to their specific use in the structural layout. Hence, the characteristics of lime mortars are of interest in the assessment of the structural characteristics of historic buildings. In addition, the determination of characteristics of lime mortars is also important for the production of intervention mortars to be used in the restoration of historic buildings. This research focused on the effects of egg white on lime mortar’s physical and mechanical properties. Five mixes were prepared by maintaining a constant lime–sand–water ratio of 1:2:0.035. As the binder material, the control mixture comprised only lime putty, while various percentages of egg white in the range of 2–10% were used to prepare the remaining mixtures. An experiment was then performed with different percentages of egg white to examine the lime mortar’s axial compressive and flexural strength, as well as the water absorption. The results indicated that the compressive and flexural strength of the lime mortar increased with the increasing percentage of egg white added into lime mortar until the mixture reached 6% egg white. The addition of 8% and 10% egg white made the compressive and flexural strength start to decrease. Lime mortar that contains 6% egg white had the highest compressive and flexural strength compared to the other mix design groups. The axial compressive strength and bending strength of lime mortar can also be influenced by the air pores.

This paper describes and discusses the results of designing and implementing a steel formwork for casting and testing concrete slab specimens with different sizes. The formwork saves space, materials and costs due to the different configurations it may adopt, which allow, for instance, casting slabs with different sizes. The formwork avoids purchasing a greater number of formworks of particular dimensions, which increases costs and the space needed for storage. The formwork performance was assessed through the analysis of numerical results (strain and stress) obtained from simulations using finite element software. Performance was also verified during construction and testing of concrete slab specimens, reinforced with welded-wire meshes or steel fibers. The novel steel formwork herein presented and discussed is currently a patent pending in the Colombian Office of Industry and Commerce.

In order to determine the characteristics that govern the out-of-plane behaviour of masonry infills, two groups of wall specimens were built and tested in the laboratory. Specimens were assembled and tested as described in EN 1052-2 provisions and constitute of flexural strength for a plane of failure parallel and perpendicular to the bedjoints specimens. By obtaining data from experiments, numerical micromodels were developed to predict their mechanical behaviour. A calibration procedure undertaken and results obtained from the experimental campaign were found to be in agreement with those obtained from the numerical models. Additionally, former in-plane infilled frame numerical models were tested with acquired out-of-plane calibrated material model. No significant difference was found.

In this study, the formability of woven carbon-fiber (CF)-reinforced polyether-ether-ketone (PEEK) composite sheets in the solid-state thermoforming process were investigated, and the failure mechanisms were discussed. The formability of the woven CF/PEEK sheets were analyzed using flexural tests, Erichsen test, and microscopic observation. The results show that the formability of CF/PEEK sheets significantly increases as the temperature rises from 165 to 325 &deg, C, and slightly decreases as the deformation speed rises from 2 to 120 mm/min. The deformation of the sheets is caused by plastic deformation, shear deformation and squeeze deformation, without plastic thinning and fiber slippage, which is due to the restriction of the solid matrix and locked fibers. Moreover, the wrinkles will cause fiber fracture at lower temperatures and delamination at higher temperatures. At higher temperatures, the wrinkles mainly occur at the position with [0&deg, /90&deg, ] fibers due to the squeezing of the matrix and fibers.

Znano je, da se poraba polimernih materialov iz dneva v dan povečuje. Posledično izrazito narašča tudi količina polimernih odpadkov, ki vstopajo na trg. Čim hitreje je potrebno najti pot, ki nas bo vodila do učinkovite izrabe sekundarnih polimernih surovin. To raziskovalno delo je opravljeno z namenom karakterizacije mehanskih in mikrostrukturnih lastnosti mešanic kompozitov s polimerno matico iz recikliranih polimerov v kombinaciji z različnimi polnili. V laboratoriju smo izvedli analizo ekstrudiranega materiala ter določili vpliv različnih pogojev izdelave na končno karakteristiko samega kompozita. Delo predstavlja tudi možnosti uporabe takšnega materiala in standarde, ki jih takšen kompozitni produkt mora izpolniti za uspešen prodor na trg. Raziskava je pokazala, da imajo kompozitni materiali s polimerno matico iz recikliranega polimera karakteristike, ki so povsem primerljive s karakteristikami primarnih polimernih materialov. Potrdili smo tezo, da je iz recikliranih polimernih materialov skupaj s kombinacijo različnih polnil mogoče izdelati preproste izdelke s primerljivimi ali celo izboljšanimi karakteristikami, ki so tako primerni za vsakdanjo uporabo. It is well known that the consumption of Polymeric materials is increasing day by day. Consequently, the quantity of polymeric waste which is entering the market is also rapidly increasing. In order to reduce the problem we need to find a path, that will lead us to the efficient use of secondary polymeric raw materials. This research work is carried out with the purpose of characterizing the mechanical and microstructural properties of composites based on recycled polymers with combination of various fillers. In the laboratory we have performed an analysis of the extruded material and determined the influence of the different manufacturing conditions on the final characteristic of the composite itself. The work also presents the possibilities of using such material and the standards that such a composite product must fulfill in order to be successfully implemented on today’s demanding market. The study showed that composite materials with polymer base consisting only recycled polymers have characteristics that are completely comparable to the characteristics of primary polymer materials. We have confirmed the thesis that simple products with comparable or even improved characteristics can be made by recycled polymeric materials, together with a combination of various fillers and are therefore suitable for everyday use.

In recent years, carbon fibre reinforced thermoplastics (CFRTP) are expected to be used as lightweight structural materials for mass-produced vehicles. CFRTP with thermoplastics as matrix allows us to weld them using melting of matrix by heating. We have been developing a direct resistance heating method, which uses carbon fibres as the resistance heating element. Carbon nanotube (CNT) is expected to be used as additive to FRP and we reported that the fibre/matrix interfacial shear strength was improved by grafting CNT on the surface of carbon fibres and tensile lap-shear strength was improved by using CNT grafted carbon fibre as the heating element for welding. For the practical use of CFRTP for structural parts, flexural strength is also necessary to be evaluated. In this study, flexural test was carried out to clarify the effect of CNT deposition time to the surface of carbon fibres on flexural strength of resistance welded CFRTP using CNT grafted carbon fibre as the heating element. The highest flexural strength was obtained when CNT10, for which CNT is grafted on the carbon fibres for deposition time of 10 min, was used for the heating element of resistance welding. In the case of CNT deposition time of 60 min, the lowest flexural strength was obtained because of the poor impregnation of the resin into the carbon fibre due to the excess CNT on the carbon fibres.

Aquest estudi busca estudiar la interacció dels diferents elements de les estructures híbrides a un nivell mecànic-resistent, enfocant-se en el material compost de Carbon Fiber Reinforced Polymer (CFRP) i formigó. Es fa un estudi del comportament del formigó amb una xapa de CFRP, on la xapa de CFRP es col·locada per l’estudi com a material de reforç estructural, estudiant diferents casos d’elements d’adherència que es troben sobre la superfície del CFRP. Es documenta el procés complet de fabricació i condicionament dels espècimens a assajar, tenint en tot moment en compte les mesures de seguretat necessàries per a la realització de cada tasca. Es sotmeten els espècimens a esforços de tallant i de flexió per determinar quin elements de nexe milloren les seves propietats i quin es el canvi en el comportament de l’estructura. S’intenta aproximar el comportament inicial de l’estructura híbrida a flexió mitjançant el teorema de l’homogeneïtzació i al punt de trencament mitjançant una suposició de la distribució d’esforços. Un cop determinats els elements de nexe que donen millors propietats, es duu a terme la fabricació d’un prototip de dipòsit d’aigua per comprovar la possible industrialització de la tecnologia

Композити з різною структурою алюмосилікатних волокон були виготовлені і випробувані для отримання оптимальної гібридної структури. Алюмополімерний композит є унікальним матеріалом, який останнім часом має широку сферу використання в інженерії, оборонному комплексі, транспортних засобах, аерокосмічній і морській галузях. Гібридні композити GLARE виробляються із додаванням надтонкого поверхнево обробленого шару алюмінію на поверхні однонаправлених тканин E-Glass із включеннями епоксидного полімеру. Спочатку було виготовлено декілька матеріалів GLARE з різним фракційним складом. У результаті досліджувалась поведінка матеріалу при згинанні для виявлення усіх параметрів гнучкості. Виявлено надвеликий коефіцієнт ударного опору такого гібридного матеріалу. Результати показали, що збільшення концентрації металу значно збільшує здатність поглинання енергії на композит, а також підтвердили незначну зміну модуля пружності першого роду. Наостанок, зруйновані поверхні були досліджені із застосуванням оптичного мікроскопу. Composites with different configuration of fiber (E-Glass) and metal (Aluminium) laminates were fabricated and tested for grasping optimum hybrid structure. GLARE (Glass laminate aluminium reinforced epoxy) is a unique composite recently being used by wide engineering domains like defense body and vehicle armors, aerospace, marine and structural applications. The GLARE hybrid composites are manufactured by adding very thin layer of aluminium sheets (surface treated) on the surface of unidirectional E-Glass fiber fabrics in presence of epoxy polymer. Firstly three hybrid GLARE laminates were fabricated with different volume fractions. Consequently, impact and flexural behaviors are measured by izod, charpy impact and flexural tests for all volume configurations. Impact resistance of such hybrid laminate is intensively great. The results depicts that the linear metal volume fraction (MVF) increment on fiber metal laminates greatly increases impact energy absorption capacity of composites and little difference in flexural modulus. Finally the fractured surfaces were analyzed by optical microscope.