The oil and gas industry faces constant problems with internal corrosion in pipelines and the integrity of structures and pipes. In these environments, the presence of carbon dioxide (CO2) acts as a contaminant that intensifies corrosive processes, a phenomenon known as sweet corrosion. This type of corrosion occurs when dissolved CO2 reacts with water to form carbonic acid, which contributes to lowering the pH and increasing the aggressiveness of the environment. A characteristic aspect of this mechanism is the formation of iron carbonate (FeCO3), which can act as a protective barrier, reducing the corrosion rate. However, corrosion in CO2 environments can manifest itself in different ways, mainly as generalized corrosion and localized corrosion. Generalized corrosion occurs uniformly, resulting in the continuous loss of material, while localized corrosion is more severe and unpredictable, concentrating in specific areas and forming pitting. Both mechanisms are affected by flow, as local turbulence can cause rapid variations in wall shear and turbulent kinetic energy, which influences the mass transfer process and, consequently, the precipitation and adhesion of FeCO3 films. This study evaluated the behavior of API X65 carbon steel under static conditions, varying parameters such as temperature, CO2 pressure and acetic acid concentration, by means of autoclave immersion tests. The most aggressive condition (60 °C temperature, 10 bar CO2 pressure, 60000 ppm NaCl and 1000 ppm HAc) was also evaluated in dynamic tests using a rotating cage (RC) at 800 rpm. To assess the effect of flow, artificial defects were machined into the RC specimens. The results indicated that the different experimental conditions caused variations in the morphology and adhesion of the iron carbonate (FeCO3) films, directly affecting the corrosion rate of the carbon steel. In addition, it was observed that in the dynamic condition, the generalized corrosion rate increased sharply and the emergence of the localized corrosion mechanism was observed. In this condition, the detachment of the FeCO3 film and an increase in the size of the artificial defects were identified, possibly due to the combined effect of the more aggressive environment and the flow over the surface of the specimen.

Currently, machining has been the process of metal-mechanical transformation of great importance and use, demanding several developments of technologies that aim at better efficiency of operations. As technology advances, consumers demand products with better cost/benefit, which in machining, impact on cutting tools with longer life, or in reducing operating costs such as the use of cutting fluids. However, in some cases, special needs outweigh these requirements, such as the presence of cutting oil in products from the oil/gas sector, making it important to search for techniques that can replace emulsions and increase tool life. In this sense, this work analyzed the use of the air-cooled system in the internal turning of a product from the oil and gas sector, compared with the use of emulsion and dry cutting. For this, the responses of forces in the cut, roughness and cylindricity in cutting conditions similar to those used in the industrial environment were evaluated. The results showed that, although the use of emulsion provides better responses, in some cases, there is improvement in the cutting forces with the replacement of the air cooled system. But, there was a worsening in the geometric deviation responses, roughness and cylindricity, due to the air flow.

Superalloys are widely used in high temperature applications and harsh environments. Inconel 625 is one of the most applied superalloys due to its high resistance to oxidation and mechanical properties. In this work, the microstructure and oxidation mechanism at 900 and 1000 °C of the Inconel 625 superalloy manufactured by the directed energy deposition (DED) and conventionally manufactured (CNV) additive manufacturing process were studied. The samples were cyclically oxidized for up to 100 cycles and isothermally oxidized at 900 °C for 200 hours and at 1000 °C for 100h. Each thermal cycle consisted of 60 minutes at the oxidation temperature and 10 minutes in which the samples were exposed to room temperature for cooling. To characterize the oxidized layers, X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) analyzes were carried out. The microstructure of the DED samples alternated between fine equiaxed grains and columnar grains, with Nb and Mo segregations located in the dendritic and interdendritic regions. At 900 °C the oxidation rate was similar for both materials, both in the cyclic and isothermal tests, but was clearly higher for the DED material at 1000 °C in both tests. Inconel 625 (CNV and DED) showed detachment at 900 and 1000 oC in cyclic tests. The oxide layer was identified as predominantly Cr2O3 under all conditions, providing good resistance to oxidation. In addition, oxides such as NbCrO4 as well as NiCr2O4 were identified for the CNV and DED samples. In isothermal tests, the delta phase Ni3(Nb,Mo) was observed for the CNV and DED alloys at the grain boundaries at 900 °C and at the metal/oxide interface for both temperatures as a result of chromium depletion. Finally, Inconel 625 produced by DED showed lower resistance to oxidation, being related to the microstructure, the segregation and the open porosity observed in the samples produced by DED.

Sustainability is one goal for all industrial process nowadays. The great challenge is to have more and more cleaned and optimized processes. Considering the negative impact of mineral or vegetal coolant on the environment and operator health, the target of this study was to provide an alternative cooling method with cold air to replace the liquid coolant. In advanced process with high cutting speeds, the function of cooling the cutting region is much more important than lubrication. To analyze the differences between the cooling methods, tests were performed using vegetal coolant, as traditional method and cold air in two different conditions, with the air flow directed to the rake surface and also directing the air to the rake surface and flank surface. The temperatures, cutting forces and average surface roughness (Ra) were measured as responses and ANOVA was used as method of analysis. The preliminary results indicate that there are no significant differences in cutting forces and surface roughness, but the cold air didn’t have the same or better cooling efficiency. New tests including liquid nitrogen will be performed in an attempt to improve the cooling efficiency keeping in the way of clean cooling methods, mainly because the results for cutting forces and surface finishing were satisfactory.

The helical milling process has been explored in the production of holes for various industries,
standing out biomedical and aerospace. Due to the high precision required and the difficulty of
machining the titanium alloy Ti-6Al-4V, the cutting parameters need to be defined in order to obtain
acceptable levels of quality and precision for such applications. Helical milling, when compared to
conventional drilling, is recommended because it presents low levels of cutting forces and better
quality due to the kinematics of the process. In this work, the main objective was to study the helical
milling to obtain holes in the titanium alloy Ti-6Al-4V. For this purpose, a Box Behnken Design
(BBD) planning was used, enabling the obtaining of second-order regression models capable of
optimization, as a function of the cutting parameters of helical milling, being them, the axial and
tangential feeds per tooth and the cutting speed. The average roughness Ra, circularity (Ront) and
material removal rate (MRR) responses were evaluated. The models obtained for the Ra and Ront
analysis presented adjustments of 87.99% and 84.92% successively, corroborating a good
proportion of explanation of the data variability, having sufficient reliability for a greater
evaluation of the effects of the variables on the responses presented. Finally, for optimization, the
multiobjective optimization method by adaptive geometry estimation (AGE-MOEA) was used to
determine a set of Pareto optimal solutions for the finishing response and the material removal rate.
According to the optimization, to minimize roughness and circularity, it is necessary to adopt as
feeds: fza = 0.71 µm/tooth and fzt = 0.06 mm/tooth and a cutting speed: vc = 59.16 mm/min, while
for greater productivity, it is necessary: fza = 1.20 µm/tooth and fzt = 0.07 mm/tooth and a cutting
speed: vc = 59,16 mm/min. As analyzed through scanning electron microscopy (SEM) images, it
was possible to conclude that for low fza levels, combined with a low cutting speed, inferior surface
quality was observed due to the dragging and adhesion of removed material, as a consequence of
the difficulty in evacuating the chip.

Currently, austenitic stainless steels are produced in large quantities, possessing good mechanical properties, including high toughness and cold workability, with nickel as the primary phase stabilizer. For economic reasons, however, some alloys use manganese as a partial or total substitute for nickel, such as FeMnSiCrNi, which offer relatively low cost, good workability, and ease of processing. Nevertheless, at high temperatures, manganese preferentially reacts with oxygen rather than chromium, preventing the formation of a protective Cr2O3 layer; furthermore, Cr2O3 tends to volatilize at higher temperatures, thus compromising the alloy's oxidation resistance. In contrast to chromium oxide, alumina (Al2O3) is more stable under such conditions; however, the amount of aluminum required to form a protective layer would result in unacceptable mechanical properties. This study evaluated the effect of a coating obtained by pack aluminizing on the oxidation resistance of an FeMnSiCrNi alloy. Cyclic and isothermal oxidation tests were conducted at temperatures of 900 and 1000 °C. At 900 °C, the coating significantly improved the alloy’s oxidation resistance, delaying degradation due to spallation. In the isothermal regime, the aluminized samples showed no spallation; despite manganese diffusion the aluminized coating remained intact. At 1000 °C, however, both aluminized and non-aluminized samples presented loss of mass under both cyclic and isothermal conditions. Compared to other studies, although, the aluminized alloys oxidized at 900 °C achieved significantly better results, given that the tests were conducted under more severe conditions of regime and temperature.

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EVALUATION OF LOCALIZED CORROSION AND FORMATION OF FeCO3 WITH THE PRESENCE OF FLOW IN DIFFERENT CONCETRATIONS OF SODIUM CHLORIDE

Composite materials can have excellent mechanical properties between the combination of materials and fiber orientation in order to produce optimized and specific structures for each application. When considering factors such as low cost, low density and the search for biodegradable materials, natural fibers and resins obtained from renewable sources has gained relevance in the production of composite structures. Thus, the present work aims to investigate, through a complete 2² factorial design, the effect of the matrix phase, epoxy resin or castor oil, and the reinforcement stage arrangement, unidirectional staple fibers or bidirectional fabric, on the physical and mechanical performance of polymer composites reinforced with jute staple fibers. The reinforcement phases jute staple fibers and bidirectional jute fabric were characterized by mechanical tensile test. The composite materials were characterized in tensile, bending, impact, apparent density, apparent porosity and water absorption tests. The mechanical behavior of composites reinforced with unidirectional staple fibers for three-point bending was investigated through numerical simulation with a nonlinear implicit and incremental formulation. The experimental study indicated that the use of castor oil as a matrix phase reduced the apparent density of the composites and increased the impact resistance. However, it also provided an increase in apparent porosity and water absorption, and reduced the flexural strength of the composites. The alteration of phase reinforcement in materials from bidirectional fabric to unidirectional staple fibers caused expressive increase in all mechanical properties. The averages of physical properties of apparent density, apparent porosity and water absorption were not statistically altered by changing the arrangement of cords. The composite made of epoxy resin and unidirectional staple jute fibers presented the best mechanical behavior in tensile and bending tests. Numerical simulations were well correlated with experimental tests for small displacements. The tensile modulus for the jute fiber obtained by numerical simulation was in line with the values found in the literature. The manufactured composite materials proved to be a sustainable and economical alternative for engineering applications, mainly those manufactured with unidirectional staple jute fibers, which exhibited satisfactory mechanical properties.

The employing the principle to drilling holes in metal is a more recent development. Friction drilling, also known as flow drilling or friction drilling, is an unconventional manufacturing process in which a tapered-tipped carbide rotating tool is pressed into a material, usually metallic. With the contact between tool and part, there is an increase in temperature, and consequently, a decrease in the resistance to deformation of the material due to its flow, thus causing the hole to be made. In this process, there is no chip formation, what occurs is the formation of a bushing due to the flow of the material. The bushing can be used, for example, as a fixing point by brazing or be threaded, serving as a connection point for screw fixings. With different possibilities of applications, the possibility of performing the drilling procedure by friction in different materials is also highlighted, among them, the material studied here is commercially pure titanium, known to be a promising material in applications in the naval and aeronautical industries, and for being considered one of the best biocompatible metallic materials. In this context, this work evaluates the geometric deformations caused in the height of the bushing and diameter of the hole formed in the process of drilling by friction. For that, the rotation speed and the feed were compared, both in dry and lubricated conditions.

Most composite materials are heterogeneous when observed microscopically. However, ordinary finite element analyses of composites do not consider the influence of phases on the mechanical behaviour of the material. This work evaluates different composites using a sequential multiscale methodology, which models each phase with a micromechanical computational analysis of the representative volume element (RVE) and brings the homogenised results to the macroscale. Three types of composites are made with epoxy matrix phase and are classified as silica particle-reinforced polymer (SPRP), carbon fibre-reinforced polymer, and carbon fibre silica particle- reinforced polymer or hybrid. RVE uses a 3D Finite Element (FE), and it is restricted with different boundary conditions. The macroscale represents the geometry of ASTM specimens fabricated for experimental testing with the FEM. A User Material subroutine (UMAT) reproduces the behaviour of micromechanical analyses at the higher scale. Experimental analysis characterise and validate numerical results. In particular, for the SPRP, the results were taken from literature. For fibrous composites, a hand layup method is performed considering the fibre volume fraction of 30%. In addition, the hybrid configuration considers 9wt% of the particles in relation to the total mass of the matrix. Tensile, compression, and in-plane shear tests are performed. Unidirectional laminates are characterised in the longitudinal (0º) and transverse (90º) directions for tensile and compression tests, while a 45º/-45º ply configuration is employed for the shear test. The results show good accuracy for elastic and inelastic responses when compared to experimental and numerical mechanical behaviours. This methodology can support future researches in the same field.

The search for materials with less environmental impact has driven mainly biodegradable and those derived from renewable sources. Biodegradable foams and resins derived from vegetable oils have been investigated and applied in different areas of engineering. Manufacturers stipulate the “ideal” ratio between polyol and prepolymer (a certain ratio taken as the best) associated with a range of applications. However, the various applications focus on the characterization of composites, that is, on the study of the proportions between the phases, but it does not provide purely characterization of the matrix phase. Knowledge about the physical and mechanical properties of matrices prepared with different proportions between polyol and prepolymer can help better understand the performance of the manufactured composite as well as the most appropriate indication of the proportions between the proportions of the adhesive for cases of requests and conditions in different application. This work describes the mechanical and physical properties of biodegradable castor-based foams composed of 2 polyols and 1 pre-polymer. Statistical planning design is used to identify the combined effect of polymeric components on mechanical and physical properties. Contour graphs are obtained, capable of describing the material properties according to the mass percentages of each component. The specimens are obtained through the reactive expansion of the constituents in only one direction, allowing them to obtain anisotropic properties. The results show that it is possible to obtain variations of up to 80% in the mechanical properties. The increase in P2 concentration leads to lower specific properties of the foam. P2 does not affect the final mechanical properties, but the foam density increases considerably. On the contrary, the P1 component increases the density along with the mechanical properties, while PP reduces the density and mechanical properties of the foams. Finally, mathematical models can optimise the mix of the components to achieve a particular performance. The transverse properties (perpendicular direction to the expansion) are higher than the longitudinal ones.

The growing exploitation of natural resources and their unconscious use by man
emphasizes a worldwide trend to develop sustainable and resistant materials, such as sandwich
panels. Recycling and reusing products reduce the need for raw material extraction, conserving
natural resources and eliminating environmental impacts. In addition, variations in core
geometry and materials are investigated to improve the final mechanical properties. This work
presents the development and characterisation of a sustainable sandwich panel of recycled
aluminium skins bonded to an arch-shaped core obtained from reused aluminium cans. A full
factorial design was performed to identify the effects of three factors: type of adhesive (two
epoxies and one polyurethane), the average thickness of the adhesive (0.8 and 1.5 mm), and
the orientation of core arches (aligned and alternated). The sandwich panels were tested under
a three-point bending test, from which the main flexural properties were obtained. The
properties were statistically verified using Analysis of Variance (ANOVA) and the Tukey test.
The results showed the feasibility of the proposed sustainable structure, in which more
satisfactory results of strength and stiffness were obtained for panels made with epoxy polymer
type C (Epoxy RenLam-M + HY951), greater average adhesive thickness (1.5 mm), and
alternate core orientation. The panels showed to be promising for secondary structural
applications, having low weight, cost and presenting an alternative route for the reuse of
components highly discarded in nature.

Superalloys are mainly used because of their exceptional properties, such as mechanical strength and oxidation resistance. The oxidative process is commonly observed in engineering applications and it is usually accentuated under conditions involving high temperatures. These alloys are often used in operations involving high temperatures and stresses, such as gas turbines. This makes the study of oxidation for superalloys relevant. The main objective of this work was to study the oxidation process in the MAR-M247 superalloy, followed by a complementary analysis of the conventional MAR-M246 and Nb-modified MAR-M246 superalloys. MAR-M247 superalloy was exposed to isothermal tests at 1.000 and 1.100 °C for up to 300 hours. This alloy has also been tested cyclically at 1.000 °C for up to 200 cycles and at 1100 °C for up to 219 cycles. The superalloys MAR-M246 (Ta) and MAR-M246 (Nb) were evaluated in relation to cyclic oxidation at 1.100 °C, for up to 219 cycles, in order to study the influence of the replacement of Ta by Nb. The oxidation kinetics and the characterization of the oxidation products were evaluated. The characterization of the samples was performed by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and optical microscopy (OM). Some of the conclusions obtained in this work are: NiO, Al2O3, TiO2, Co3O4, NiCr2O4 e CoCr2O4 are common oxidation products for MAR-M247; the MAR-M247 alloy proved to be the most resistant to the oxidation process, followed by MAR-M246 and MAR-M246 (Nb), the last one exhibited the lowest resistance among the alloys.

Internal corrosion is one of the main failure mechanisms in oil and gas (O&G) pipelines. In order to protect the integrity of the pipelines, several researchers are dedicated to reproducing in the laboratory the environments to which the pipelines in the O&G sector are constantly exposed. Currently, the rotating cage (GR) of the ASTM G170-06 standard is one of the most used methodologies for testing the vulnerability of materials in corrosive media or the efficiency of corrosion inhibitors under turbulent flow regimes. However, the GR is a very conservative methodology and there are several factors responsible for this conservatism, for example, the non-uniformity in the loss of mass in the specimens. The objective of the present study is to evaluate, through a computational study, changes in the geometric attributes of the GR of the ASTM G170-06 standard, in order to verify the possibility of obtaining a more uniform distribution of the shear stresses in the specimens.

The growing demand for materials that promote sustainable development and the preservation of the environment make natural fibres stand out in the development of composite materials. In order to improve the properties of these materials, much research has focused on several natural fibres, manufacturing techniques and process parameters. This work investigates the mechanical performance of papaya fibre-reinforced polymeric composites based on epoxy and castor-oil biopolymer. Design of Experiment (DoE) and analysis of variance (ANOVA) techniques are used to analyse the influence of papaya fibre type (inner and intermediate), fibre morphology (without holes, with alternating or coincident holes, and randomly-oriented ground fibres) and fibre orientation (longitudinally or transversally oriented fibres relative to the load). Papaya fibres are also characterised. The specimens are manufactured by hand lay-up, followed by cold uniaxial compaction, and characterized by tensile, flexural and impact drop tower tests. For epoxy-papaya composites, longitudinally oriented provide superior mechanical properties relative to transversely oriented fibres. Composites with longitudinally oriented fibres, without holes, exhibit better mechanical properties. Randomly-oriented short fibres provide much lower reinforcing levels compared to the other morphologies. The Tukey’s test reveals that the morphologies, composites without holes and with alternating holes, are statistically equivalent for traction and flexion properties. In the drop tower test, in contrast, short random fibres provide greater energy absorption. The density of papaya fibres, among the lowest in the plant kingdom, varies according to the fibre layer.

Studies to improve the understanding of machining processes are important for efficient production. The performance of these processes depends on several factors, operational parameters, and other variables. Among the various processes, grinding stands out for its versatility and high dimensional accuracy. Although widely used, it still has some shortcomings, as chip removal is more complex when compared to conventional machining processes with defined geometry tools. In this context, this work aimed to monitor the electrical power of the main motor of the machine, correlating with the dimensional deviation and surface roughness in Ra and Rz parameters of AISI H13 steel in the process of tangential plane grinding process. The input variables tested were working penetration at three levels (0.015; 0.03 and 0.05 mm) and workpiece speed at two levels (10 and 22 m/min). A vitrified aluminium oxide wheel in three conditions was used, being in worn condition, and dressed with two dressing overlap ratios (1 and 5) correlating the dressing parameters and the wheel topography. The results showed that the increase of the working penetration caused an increase in the power signals, the dimensional deviations, and the surface roughness for the three conditions of the grinding wheel. Increasing the workpiece speed also caused an increase in the power; however, regarding the dimensional deviation and surface roughness, the values obtained were lower. The worst results were presented for the conditions imposed on the wheel while worn. In contrast, when dressed, the same wheel had a substantial performance improvement. Higher electrical power values, lower-dimensional deviations, and lower surface roughness were observed significantly when increasing the dressing overlap ratio. The results showed that the electrical power signal was sensitive to variations of the input parameters analysed. Its relationship with possible dimensional deviations and surface roughness values may be able to analyse and diagnose distortions that affect the final quality of the ground parts.

Geopolymers are a materials class, conceived thru the aluminosilicate alkaline activation. Could be obtained by industrial residue calcination (fly ash, bottom ash, ground granulated blast furnace slag, etc.) or calcinated materials (metakaolin). Exhibiting low cost, great availability and good chemical and mechanical properties. Cheap, with good workability and environment friendly materials have been a necessity in the construction industries. with this in mind this work aims on the development of a new mortar (constituted by diffrents weigth proportions), with better workability, mechanical and structural properties thru epoxy resin incorporation in the metakaolin based geopolymer. Were investigated the effects of 0, 15, 20 and 25% resin addiction by weight in relation to the base polymer in mortar with sand in 0:1, 1:1, 2:1 and 3:1 weight proportions by the base geopolymer or with resin content, in the mechanical properties 28 days after production, with 60‰initial cure. A 24 estatistcal planning was used. Were analyzed also the structural modification of the precursor and base polymer thru MEV and EDS. Even with both being significative and with interaction between them, the most influent factor in the process was sand percentage. All investigated response variables, had their properties changed with the resin percentage increase to 15, 20 and 25%. So in this work a superior substitute to CPT was found.

Biocompatible alloys are important for the biomedical industry as they offer alternatives in different treatments. The Ti-6Al-7Nb alloy has excellent mechanical properties and can be used in implants, which can be require holes. The helical milling, compared to drilling, is recommended because presenting low levels of cutting efforts, better finishing, lower temperatures in the cutting region, all this, as a consequence of the kinematics of the process. In this dissertation, the main objective was to study the process of helical milling to obtain holes in biocompatible titanium alloy. In this study, cental composite design was used, making it possible to obtain second-order regression models, which can be optimized, depending on the cutting parameters of helical milling, namely, cutting speed, axial feed per tooth and tangencial feed per tooth. Surface roughness responses were evaluated. Principal component analysis was used to allow the transformation of a set of original intercorrelated variables was enough to represent all the roughness responses. A second-order model for the transformed response was obtained. Finally, for optimization, the NSGA-II bi-objective evolutionaty optizimation method was used to determined a set of optimal Pareto solutions for the surface quality response and material removal rate (MRR). Therefore, according to the optimization, the best values to obtain the best surface quality parameters should be set at 𝑓𝑧𝑎 = 0,033 µm/tooth and 𝑓𝑧𝑡 = 3,65 µm/tooth. While for greater productivity the factors need to be defined at 𝑓𝑧𝑎 = 0,04 µm/tooth and 𝑓𝑧𝑡 = 2,99 µm/tooth. As analyzed the images of scanning eléctron microscopy (SEM) it was possible to conclude that the ploughing effect had na influence on the deterioration of the surface quality at low levels of feed.

The present work was based on the proposal of a new methodology (RJS Method), through the three-point bending test, for the identification of the flexural modulus and shear modulus of sandwich panels with a core of non-negligible rigidity. Sandwich panels were characterised under bending in different sizes of width and length, in order to validate the proposition that, in practice, the geometry of the test specimen directly influences on parameters elastics identification. The elastic properties obtained by the RJS Method were statistically compared to theoretical values. Furthermore, these same properties were used to determine the modal shapes and the natural frequencies simulated by the finite element method. Modal parameters obtained through experimental modal analysis were compared to those obtained by the numerical simulation; as well were used in the virtual field method (VFM), applied to identify the flexural rigidity of composite material plates. The flexural modulus obtained using the RJS Method is statistically coherent when compared to the theoretical flexural modulus and to that obtained by the VFM. Although the RJS Method for identification of the flexural modulus has been validated through modal analysis, the same was not possible for the core shear modulus test – because the mode shape associated with the shear is not ideal, for this purpose, in sandwich panels. Nevertheless, the core shear modulus obtained by the RJS Method is consistent with the expected for the type of material of the cores under study.

Sandwich panels are structures widely used in different fields of engineering. These structures are made of high-strength skins attached to a low-density core. Its main features are: high energy absorption rate, high strength and flexural stiffness, and high performance when submitted to compressive loads, in addition to low weight. This work describes the development and characterization of sandwich panels made from disposed polypropylene (PP) bottle caps, used as a circular honeycomb, and glass fibre composite skins. Three-point bending test is performed to assess the composite structure using the following parameters: Maximum Load, Core Shear Stress, Skin Stress, Core Shear Modulus, Flexural Strength and Flexural Modulus – as well as, their respective specific properties (ratio between properties and their densities). A full factorial design (DoE) along with the Analysis of Variance (ANOVA) is carried out to identify the effects of the core packing system (cubic, hexagonal and orthotropic) and micro-silica inclusions (7.5 %wt) at the upper, lower and both composite skins. Finite element (FE) analysis is developed to investigate and predict the failure mechanisms of the sandwich structure. The experimental force vs displacement curves are compared with the numerical obtained in the FE analysis to ensure a good adjustment of the model to the experimental data. ANOVA reveals that the cubic and hexagonal packing system contributes to increase the mechanical properties compared to the orthotropic packing. The presence of silica in both skins leads to enhanced panel strength and stiffness when compared to the incorporation in the upper or lower skin and in pristine condition. Specific properties follow the same behaviour as absolute properties; the best configuration is obtained when hexagonal packing and silica micro-particles are added to both composite skins.

This study aims to determine the best condition of incremental stamping of sheets by single point (association of parameters) that presents the highest resistance to fatigue for the test specimens. For this, a blank press and two punches of different diameters were designed and manufactured. Subsequently, 12 SAE 1010 steel sheets were stamped in a Sinitron CNC milling machine. The stamped steel sheets were submitted to a non-destructive ultrasound test, in order to verify if the sheets lost thickness after the stamping process, using a thickness gauge T – Gage IV Sonatest. The stamped plates will be taken to be cut the specimens. These specimens will be used to analyze the surface finish with the measurement of Roughness levels in each specimen and for tensile and fatigue tests. In conjunction with these actions, the new support for fixing the specimens of the fatigue machine was designed, in which the raw material is already in the acquisition phase. As a partial result, it was found that both the plate holder and the punches performed their functions correctly. The steel sheets were plastically deformed without breaking or structural failures. The values obtained by the Ultrasound test were statistically treated and were in line with the Sine Law for measuring sheet thickness.

A statitistical approach based on the full factorial design 2¹4¹6¹ (DoE) is applied to verify the interaction effect of the factors (levels), fibre stacking configuration (carbon-C₅, glass-G₅, C₂G₃, G₃C₂, GCGCG and CG₃C), inclusion of particles (silica, cement and carbon microfibre-CMF) and matrix-fibre volume fraction (40/60 and 60/40) on the physical, modal and mechanical properties of the hybrid system. Hybrid fibrous- particulate composites are characterised under three-point bending and drop tower impact tests, along with physical properties such as apparent porosity, water absorption, bulk density, ultra pulse velocity and damping factor. The impact and flexural fractured surfaces are examined by optical and scanning electron microscopy (SEM). The results reveal a significant synergistic effect, in which hybrid composites exhibit an overall performance improvement of approximately 20% compared to glass and carbon composites. A greater dependence on the fibre layup-sequence is found for the bulk density, damping factor, flexural modulus and strength, while the matrix/fibre volume fraction is the most relevant factor affecting the apparent porosity, water absorption and pulse velocity of the hybrid composites, indicating a mutual dependence; the impact behaviour also reveals consistent layup-dependent trends. However, the particle type factor is the main factor that affects impact energy and resistance. Flexural strength and impact resistance are increased when silica microparticles are added. A larger amount of matrix phase ratio leads to a more efficient rheology in terms of fibre-particle interface. In glass/fibre composites, the carbon fibre layers placed symmetrically on both tensile and compressive sides (CG₃C) enhance the material mechanical performance. Finally, the fibre-particle hybridisation is a promising configuration in terms of physical, modal and, mechanical behaviour, for structural engineering applications.

Desenolvimento e caracterização de compósitos cerâmicos e cerâmico-poliméricos destinados à restauração de monumentos históricos fabricados em esteatito (pedra-sabão)