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Sustainable building materials with excellent thermal stability and sound insulation are crucial for eco-friendly construction. This study investigates biocomposites made from cellulose pulp reinforced with beeswax, fir resin, and natural fillers like horsetail, rice flour, and fir needles. Eight formulations were obtained, and their thermal resistance, oxidation temperature, and acoustic properties were evaluated. Biocomposites exhibited significant improvements compared to conventional materials. Oxidation temperature onset increased by 60–70 °C compared to polyurethane foam or recycled textiles, reaching 280–290 °C. Sound absorption coefficients ranged from 0.15 to 0.78, with some formulations exceeding 0.5 across mid-frequencies, indicating good sound-dampening potential. These findings demonstrate the promise of these biocomposites for sustainable construction, offering a balance of thermal and acoustic performance alongside environmental and health benefits. [ABSTRACT FROM AUTHOR]

Sound-absorbing panels are widely used in the acoustic design of aircraft parts, buildings and vehicles as well as in sound insulation and absorption in areas with heavy traffic. This paper studied the acoustic properties of sound-absorbing panels manufactured with three nozzle diameters (0.4 mm, 0.6 mm and 0.8 mm) by 3D printing from three types of polylactic acid filaments (Grey Tough PLA; Black PLA Pro; Natural PLA) and with six internal configurations with labyrinthine zigzag channels (Z1 and Z2). The absorption coefficient of the sample with the Z2 pattern, a 5.33 mm height, a 0.6 mm nozzle diameter and with Black PLA Pro showed the maximum value (α = 0.93) for the nozzle diameter of 0.6 mm. Next in position were the three samples with the Z1 pattern (4 mm height) made from all three materials used and printed with a nozzle diameter of 0.4 mm with a sound absorption coefficient value (α = 0.91) at 500 Hz. The highest value of the sound transmission loss (56 dB) was found for the sample printed with a nozzle size of 0.8 mm with the Z2 pattern (8 mm height) and with Black PLA Pro. The extruded material, the nozzle diameter and the internal configuration had a significant impact on the acoustic performance of the 3D-printed samples. [ABSTRACT FROM AUTHOR]

This article presents the results of an analysis regarding the microstructure, mechanical strength, and microhardness of two kinds of samples built through selective laser melting with Inconel 718, the most frequently used alloy in metal additive manufacturing due to its excellent mechanical properties. The sample geometry was made up of two types of lattice structures with spherical and hyperbolical stiffness elements. The goals of these studies are to determine how homogenization heat treatment influences the microhardness and the mechanical properties of the specimens and to identify the structure with the best mechanical properties. The analysis showed that heat treatment was beneficial because the regular dendritic structure disappears, the δ phase precipitates at the grain boundaries, and both the γ and γ″ phases dissolve. It has also been shown that the structures with hyperbolical stiffness elements have better compressive strength than the structures with the elliptical structures, with a 47.6% increase for the as-fabricated structures and an approximate 50% increase for the heat-treated structure. [ABSTRACT FROM AUTHOR]

One of the latest tendencies in research related to material extrusion based on additive manufacturing is to determine the mechanical characteristics of parts taking into consideration the most influential manufacturing parameters. The main research objective is to describe how the manufacturing parameters, part orientation, layer thickness and infill density influence the tensile behavior of specimens made from PET with 15% short carbon fibers. The most advantageous result is obtained for a layer thickness of 0.15 mm, with 100% material infill, and material deposition on the longitudinal direction of the part. The obtained mean values are: 65.4 MPa tensile strength, 1.93% strain at rupture, and 9 GPa Young Modulus. For these values, the tensile behavior of specimens manufactured along transverse and thickness directions are presented. The least favorable results are obtained for manufacturing by thickness. The novelty of the discussed research consists in all these aspects together with an original mathematical model that was determined based on design of experiments with a correlation of the regression model of over 90%. By optical and electronic microscopy material gaps are visible in the filament and manufactured parts, and the failure occurs in most cases in form of matrix cracks and delamination. [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) is a potential technology to be applied for replacing wood joints in the furniture industry. Overall, 3D-printed connectors have a lot of advantages in chair construction: the possibility of improving the design by using colored materials and new concepts with no limits of shape and size, avoiding the use of synthetic materials such as adhesives and finishing materials. The present research shows the results of the research conducted on 3D-printed connectors for a chair leg-stretchers joint. Larch (Larix decidua Mill.) wood was used for chair components and selective laser sintering (SLS) technology was employed for the 3D-printing connector designed to assemble the chair elements. Diagonal tensile and compression tests were performed on the L-type joints with 3D-printed connectors and the bending moments were determined and compared to the results obtained after testing the leg-stretchers mortise–tenon joints made of larch wood, taken as a reference. Micrograph investigation was finally performed on the broken areas of the 3D-printed connectors as a result of mechanical testing failures. The results show that the SLS printing technology applied to build the connector does not ensure enough strength to the assembly, and changes in printing parameters are needed for further research, in terms of laser power and scan speed. [ABSTRACT FROM AUTHOR]

The 3D printing process allows complex structures to be obtained with low environmental impact using biodegradable materials. This work aims to develop and acoustically characterize 3D-printed panels using three types of materials, each manufactured at five infill densities (20%, 40%, 60%, 80% and 100%) with three internal configurations based on circular, triangular, and corrugated profiles. The highest absorption coefficient values (α = 0.93) were obtained from the acoustic tests for the polylactic acid material with ground birch wood particles in the triangular configuration with an infill density of 40%. The triangular profile showed the best acoustic performance for the three types of materials analysed and, from the point of view of the mechanical tests, it was highlighted that the same triangular configuration presented the highest resistance both to compression (40 MPa) and to three-point bending (50 MPa). The 40% and 60% infill density gave the highest absorption coefficient values regardless of the material analyzed. The mechanical tests for compression and three-point bending showed higher strength values for samples manufactured from simple polylactic acid filament compared to samples manufactured from ground wood particles. The standard defects of 3D printing and the failure modes of the interior configurations of the 3D-printed samples could be observed from the microscopic analysis of the panels. Based on the acoustic results and the determined mechanical properties, one application area for these types of 3D-printed panels could be the automotive and aerospace industries. [ABSTRACT FROM AUTHOR]

In this paper, a blade with unconventional structure, corrugations and BERP tip, used in UAV helicopters, was designed, analyzed and additively manufactured. Aerodynamically, the unconventional blade shows better performance compared to the conventional blade at positive angles of attack. Acoustically, the unconventional blade showed a reduced noise level compared to the conventional blade. Acoustic testing of additively manufactured samples with five honeycomb core configurations showed higher performance for the 1.5 mm honeycomb cell samples 3D printed from T-PLA. [ABSTRACT FROM AUTHOR]

The first part of this paper is dedicated to obtaining 3D-printed molds using poly lactic acid (PLA) incorporating specific patterns, which have the potential to serve as the foundation for sound-absorbing panels for various industries and aviation. The molding production process was utilized to create all-natural environmentally friendly composites. These composites mainly comprise paper, beeswax, and fir resin, including automotive function as the matrices and binders. In addition, fillers, such as fir needles, rice flour, and Equisetum arvense (horsetail) powder, were added in varying amounts to achieve the desired properties. The mechanical properties of the resulting green composites, including impact and compressive strength, as well as maximum bending force value, were evaluated. The morphology and internal structure of the fractured samples were analyzed using scanning electron microscopy (SEM) and an optical microscopy. The highest impact strength was measured for the composites with beeswax, fir needles, recyclable paper, and beeswax fir resin and recyclable paper, 19.42 and 19.32 kJ/m2, respectively, while the highest compressive strength was 4 MPa for the beeswax and horsetail-based green composite. Natural-material-based composites exhibited 60% higher mechanical performance compared to similar commercial products used in the automotive industry. [ABSTRACT FROM AUTHOR]

The paper presents the influence of the loading modelling on the simulation process results of the bending behaviour for 3D printed structures. The study is done on structures having different geometries of the cross section, and the type of structure is bar or tube. The materials used for 3D printing are poly(lactic) acid and poly(lactic acid) mixed with glass fibres. The simulation was carried out both based on a simple modelling (schematization) of the bending loading and a complex one. The complex modelling reproduces the bending of 3D printed structures more accurately but is also more time-consuming for the computer-aided design stage. Analysis of the study results shows that in terms of the Von Mises stresses determined by simulation, they are in line with those of the tests but with a slight advantage for the complex modelling compared to the simple one. In terms of deformations, the simulation introduces errors compared to the test results, but the source of the errors is the high elasticity of some 3D printed structures. The study also shows that the high elasticity is due to both the shape of the structure cross section and its arrangement during the bending test. [ABSTRACT FROM AUTHOR]

Unmanned aerial vehicle helicopters are developing in recent years because they have better capabilities compared to unmanned aerial vehicle aircraft in terms of take-off and landing phase and controllability in areas with more difficult access. In this paper a helicopter blade was designed, aerodynamically and also by the finite element method analyzed, manufactured using 3D printing process. From the finite element analysis, it was observed that the blade will withstand the applied loadings, but also in flight of the unmanned aerial vehicle. The 3D printing of the blade was carried out in sections and after gluing, a blade made of polypropylene with 30% short glass fibres resulted. The microhardness of the blade is influenced by the proximity to the print bed and the 3D printing supports. Thus, both Shore D microhardness and Vickers microhardness showed higher values in proximity to the print bed. Microscopic analysis showed that the short glass fibre filament did not exhibit manufacturing defects, while conventional 3D printing defects such as voids and inter-track voids were found when 3D printing the blade sections. [ABSTRACT FROM AUTHOR]

Metallic additive manufacturing technology is seeing increasing use from aviation companies manufacturing prototypes or components with complex geometric shapes, which are then tested and put into operation. This paper presents the design, fabrication via a selective laser sintering process, and testing of the mechanical performance by performing three-point bending and tensile tests on A6 steel specimens. After performing the mechanical tests on specimens made from A6 steel manufactured via the SLS process, the following performances were obtained: the maximum three-point bending strength was 983.6 MPa and the maximum tensile strength was 398.6 MPa. In the microscopic analysis of the specimens manufactured by the selective laser sintering process, a homogeneous structure with defects specific to additive processes (voids) was revealed. Additionally, the feasibility of designing, manufacturing through the selective laser sintering process and subsequent testing of some components (rotor, right case, left case and motor mount) from a brushless motor made from A6 steel material was demonstrated. After testing the brushless motor, the main performances showed stable behavior of the motor and a linear dependence with the increase in electronic speed control signal or motor electrical speed, resulting in a maximum thrust force of 4.68 kgf at 7800 RPM. [ABSTRACT FROM AUTHOR]

Selective Laser Melting (SLM) is one of the powder based additive manufacturing technologies and it is, as well, the most rapidly growing technique in Rapid Prototyping. In this paper is presented a microstructure analysis using Scanning Electron Microscope (LEO 1525 SEM), of Ti6Al4V parts exposed into a corrosion environment. The corrosion environment was generated using a salt chamber with 5% and 10% NaCl concentration and an ACS-Sunrise climatic chamber. The parts were also subjected to tests in order to determine their micro-hardness, followed by a statistical processing of the obtained data. The parts, having a lattice structure, were built on a Selective Laser Melting machine.

Fused Filament Fabrication (FFF) is one of the frequently used material extrusion (MEX) additive manufacturing processes due to its ability to manufacture functional components with complex geometry, but their properties depend on the process parameters. This paper focuses on studying the effects of process parameters, namely infill density (25%, 50%, 75%, and 100%), on the mechanical and thermal response of the samples made of poly(lactic acid) (PLA) reinforced with short glass fibers (GF) produced using FFF process. To perform a comprehensive analysis, tensile, flexural, compression, differential scanning calorimetry (DSC), and thermal gravimetric analysis (TGA) tests were used. The paper also aims to manufacture by FFF process of composite structures of the fuselage section type, as structural elements of an unmanned aerial vehicle (UAV), and their testing to compression loads. The results showed that the tensile, flexural and compression strength of the additive manufactured (AMed) samples increased with the increase of infill density and therefore, the samples with 100% infill density provides the highest mechanical characteristics. The AMed samples with 50% and 75% infill density exhibited a higher toughness than samples with 100% infill. DSC analyses revealed that the glass transition (Tg), and melting (Tm) temperature increases slightly as the infill density increases. Thermogravimetric analyses (TGA) show that PLA-GF filament loses its thermal stability at a temperature of about 311 °C and the increase in fill density leads to a slight increase in thermal stability and the complete degradation temperature of the AMed material. The compression tests of the fuselage sections manufactured by FFF made of PLA-GF composite showed that their stiffening with stringers oriented at an angle of ±45° ensures a higher compression strength than the stiffening with longitudinal stringers. [ABSTRACT FROM AUTHOR]

This study concerns the use of the fused filament fabrication technique to create models of the landing gear of an unmanned aircraft. These components are made of filament with short fibers (chopped fibers) of carbon fiber and fiberglass. In order to identify the material with the high mechanical strength, the designed models were subjected to a finite element analysis and to a three-point bending test, followed by a microscopic examination of the tested components. Following a comparative study, both the finite element analysis results and the three-point bending test results provided similar results, with a relative error of 2%, which is acceptable in the aviation field. After analyzing all the results, it was found that the carbon fiber-reinforced polymer material has the highest mechanical performance, with a bending strength of 1455 MPa. Among the fused filament fabricated landing gears, the one with the best mechanical performance was polyethylene terephthalate with short carbon fiber, which had a bending strength of 118 MPa. Microscopic analysis of the landing gear models, manufactured by the fused filament fabrication process, indicated the typical defects of composite filaments: voids and interlayer voids. [ABSTRACT FROM AUTHOR]

Additive manufacturing, through the process of thermoplastic extrusion of filament, allows the manufacture of complex composite sandwich structures in a short time with low costs. This paper presents the design and fabrication by Fused Filament Fabrication (FFF) of composite sandwich structures with short fibers, having three core types C, Z, and H, followed by mechanical performance testing of the structures for compression and bending in three points. Flatwise compression tests and three-point bending have clearly indicated the superior performance of H-core sandwich structures due to dense core structures. The main modes of failure of composite sandwich structures were analyzed microscopically, highlighting core shear buckling in compression tests and face indentation in three-point bending tests. The strength–mass ratio allowed the identification of the structures with the best performances considering the desire to reduce the mass, so: the H-core sandwich structures showed the best results in compression tests and the C-core sandwich structures in three-point bending tests. The feasibility of the FFF process and the three-point bending test of composite wing sections, which will be used on an unmanned aircraft, have also been demonstrated. The finite element analysis showed the distribution of equivalent stresses and reaction forces for the composite wing sections tested for bending, proving to validate the experimental results. [ABSTRACT FROM AUTHOR]

In three-dimensional (3D) printing, one of the main parameters influencing the properties of 3D-printed materials is the infill density (ID). This paper presents the influence of ID on the microstructure, mechanical, and thermal properties of carbon fiber-reinforced composites, commercially available, manufactured by the Fused Filament Fabrication (FFF) process. The samples were manufactured using FFF by varying the infill density (25%, 50%, 75%, and 100%) and were subjected to tensile tests, three-point bending, and thermal analyses by Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA). It was shown that the samples with 100% ID had the highest values of both tensile, 90.8 MPa, and flexural strengths, 114 MPa, while those with 25% ID had the lowest values of 56.4 MPa and 62.2 MPa, respectively. For samples with infill densities of 25% and 50%, the differences between the maximum tensile and flexural strengths were small; therefore, if the operating conditions of the components allow, a 25% infill density could be used instead of 50%. After DSC analysis, it was found that the variation in the ID percentage determined the change in the glass transition temperature from 49.6 °C, for the samples with 25% ID, to 32.9 °C, for those with 100% ID. TGA results showed that the samples with IDs of 75% and 100% recorded lower temperatures of onset degradation (approximately 344.75 °C) than those with infill densities of 25% and 50% (348.5 °C, and 349.6 °C, respectively). [ABSTRACT FROM AUTHOR]

From a scientific point of view, heat transfer is different in solar furnaces compared with classical ones and the influence of direct concentrated solar radiation on sintered parts needs to be studied in detail to determine the feasibility of solar furnaces in manufacturing small workpieces. This study was performed on cylindrical samples with controlled morphology obtained by a powder metallurgy 3D printing technique. All samples were heated with a heating rate of 120 ± 10 °C/minute, with 0, 1, 2, 3, 4 and 5 min holding times at 900 °C and 930 °C. The morphology of the samples was analyzed microscopically, the microhardness was determined before and after sintering, and the results were correlated with the sintering parameters (temperature, heating rate and holding time). The best results were obtained at 930 °C with 5 min holding time from the microhardness value and microstructure point of view. [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) is used in many fields and is a method used to replace wood components or wood-jointed furniture components in the furniture industry. Replacing wood joints by 3D printed connectors would be an advantage, considering the fact that during the process of assembling furniture, the execution technology of the joints is difficult, time-consuming, and labor-intensive. Advanced technology of AM applied in furniture manufacturing helps the designers to create new concepts of product design, with no limits of shape, number of joints, color, or size. The diversity of 3D printers and AM technologies provides the selection of materials in relation with the applicability of the 3D printed object. In this respect, the objective of the present research is to design a 3D printed connector to be used for jointing three chair components, namely the leg and two stretchers made from larch (Larix decidua Mill.) wood, and to use reinforced polylactic acid (PLA) fiberglass (20 wt. %) filament for 3D printing this connector using AM with fused filament fabrication (FFF) technology. The design of the connector, the possibility of using this type of material, and the deposition method of filament were investigated in this research. For this purpose, several evaluation methods were applied: microscopic investigation with 50×, 100×, and 200× magnifications, both of the filament and of the 3D printed connector; mechanical testing of corner joint formed with the help of connector between chair leg and the two stretchers; and a microscopic investigation of the connectors' defects that occurred after applying the compression and tensile loads on the diagonal direction of the L-type joint. The microscopic investigation of the composite filament revealed the agglomerations of glass fibers into the core matrix and areas where the distribution of the reinforcements was poor. The heterogeneous structure of the filament and the defects highlighted in the 3D printed connectors by the microscopic investigation contributed to the mechanical behavior of L-type connecting joints. The bending moments resulting from compression and tensile tests of the 3D printed connectors were compared to the results recorded after testing, under the same conditions, the normal mortise–tenon joint used to assemble the abovementioned chair components. The larch wood strength influenced the mechanical results and the conclusions of the microscopic investigations, as well as the analysis of the broken connectors after testing recommended the change of connector design and filament deposition direction. [ABSTRACT FROM AUTHOR]

With the fourth industrial revolution, Additive Manufacturing started to offer new possibilities of manufacturing, Fused Deposition Modeling being one of the most used processes for fabrication. In this paper, the studied specimens are manufactured based on the Fused Deposition Modeling (FDM) method, with a filament of short carbon fiber and polyethylene terephthalate (PET) matrix, with a variation of the layer thickness. For the resulted specimens the tensile properties are determined according to ASTM D638. The most advantageous results are obtained for the layer thickness of 0.15 mm, with the tensile strength of 58 MPa. Based on the stress-strain curves which are presented in this paper, it also can be assumed that the material is brittle. The results of the mechanical properties are very similar for each group of specimens and it can be assumed that the mechanical properties are homogenous due to the material quality and the machine performances. For all the specimens the rupture location is almost in the same area. Due to the difficulty of carbon fiber filament printing, the manufacturing defectives which appear during the manufacturing process are detected, the most common manufacturing defectives being the material gaps from each specimen, which are identified with microstructural analysis. As failure modes, the most common failure criteria are the delamination and the matrix cracks. [ABSTRACT FROM AUTHOR]

UAV systems used automated pilots which can be configured based on the mission. The entry level market for this type of systems is not focus mainly on fixed-wing configurations. On this paper we asses, develop and simulate missions for an automated piloting system, built on a Cube Orange architecture. The flight controller is mounted on a fixed-wing twin-engine airplane built using additive manufacturing technologies. For the management and simulation of UAV mission we use Mission Planner, and open-source software from ArduPilot. The missions is simulated to obtain an improvement of the automated piloting system, evaluate the terrain from the flight path, avoid dangers, keep out of restricted areas and find the optimal routes. [ABSTRACT FROM AUTHOR]

When controlling a UAV, we have to rely on the line of site of the operator and aft wards on the communication with the ground control station. This implies expensive equipment used in communication, a skilled operator and a UAV with low autonomy. In order to address these issues an automated piloting system needs to be implemented thus offering the needed autonomy to the UAV. An automated pilot can also stabilize the aircraft and allow for the control of the UAV to be done by people without intensive training or special skills. In the present paper we present the development and implementation of such a system, built on Cube Orange flight controller, and implemented on a fixed-wing UAV with twin-engines, fabricated using additive manufacture technologies. [ABSTRACT FROM AUTHOR]

The main objective was to reduce the consumption of material when obtaining 3D printed parts (different empty shapes inside) and the secondary one was to maintain the mechanical properties closer to the full printed version. In order to achieve these objectives, two internal configurations were designed - a configuration with hexagonal gaps (material reduction was 30%) and a configuration with sinuous gaps (material reduction was 15%). The specimens thus obtained were tested for traction, threepoint bending and shock (resilience). Hexagonal hollow configuration has a resistance values close to those of solid specimens but with the advantage of consuming with 30% less material. [ABSTRACT FROM AUTHOR]

The continuous development of modern industries rises the necessity for functionally graded materials. This research starts from the consideration that the incorporation of SiC particles in the molten aluminum alloy can be difficult due to the very low wettability of SiC particles. In order to increase their wettability, SiC particles were covered with a layer of metallic copper. The incorporation of SiC particles into the aluminum alloy mass was performed by centrifugal casting. The secondary hypoeutectic Al-Si alloy used in this study was elaborated within the crucible of a resistors heated furnace. The metallic coating of SiC particles, in addition to the effect of increasing their wettability by molten metal, also has a role in preventing the formation of aluminum carbide in case of heating above 700 °C. A great amount of attention was paid to the parameters used during the centrifugal casting process. The results showed that adjusting the proportion of SiC particles within the composite allows us to obtain values of the thermal expansion coefficient within previously established limits. The present work demonstrates that the coating of SiC particles covered with a thin layer of metallic Cu creates the conditions to easily incorporate them into the molten Al mass, thus obtaining FGMs with controlled properties. [ABSTRACT FROM AUTHOR]

Being a relatively new process, additive manufacturing needs many studies to be able to produce parts with the required properties. The aim of the paper is to establish whether, based on the physical and mechanical properties determined by tensile testing and by applying finite element analysis (FEA), viable results can be obtained regarding the behavior of the 3D printed structures at the different, static loading. The application of FEA for the tensile testing of 3D specimens led to the results close to those obtained by the tests. The values of the results obtained by simulation are higher by up to 7.2% compared with those recorded by tests. The simulation was applied both for the printed specimens from a single material and from two materials (multi‐material). Regardless of the materials used in printing and the simulation method, the results of applying FEA are close to those recorded by testing. [ABSTRACT FROM AUTHOR]

To effectively utilize a feature set to further improve fault diagnosis of a rolling bearing vibration signal, a method based on multi-fractal detrended fluctuation analysis (MF-DFA) and smooth intrinsic time-scale decomposition (SITD) was proposed. The vibration signal was decomposed into several proper rotation components by applying this new SITD method to overcome noise effects, preserve the effective signal, and improve the signal-to-noise ratio. Wavelet analysis was embedded in iteration procedures of intrinsic time-scale decomposition (ITD). For better results, an adaptive threshold function was used for signal recovery from noisy proper rotation components in the wavelet domain. Additionally, MF-DFA was used to reveal the multi-fractality present in the instantaneous amplitude of the proper rotation components. Finally, linear local tangent space alignment was applied for feature dimension reduction and to obtain fault characteristics of different types, further improving identification accuracy. The performance of the proposed method is determined to be superior to that of the ITD-MF-DFA method. [ABSTRACT FROM AUTHOR]

The paper presents a study concerning the characterisation of EN 1.4136 stainless steel heat-treated by means of concentrated solar energy in orde to improve some mechanical properties. In addition to the standard chemical composition, this steel was alloyed with nickel (Ni 1.5%wt) and copper (Cu 0.30%wt). Nickel was added to increase corrosion strength in acids, oxidising or non-oxidising environments, also facilitating an improved tenacity of the material. The addition of copper allows an increasing atmospheric corrosion strength (for copper content over 0.20%), at the same time intensifying the austenitising effect of nickel. The obtained steel was subjected to a solution heat treatment (hyper-hardening) with a heating time up to a austenitisation temperature (TA = 1050 °C) for 20 (lot A) and for 33 min (lot B), respectively. The maintaining duration for austenitisation was 7 (lot A) and 21 min (lot B), respectively, followed by cooling in water. After the heat treatment in the solar furnace, the specimens were analysed from the structural point of view as well as to their behaviour when subjected to tribological stress, in accordance with the operational requirements for these types of steels. The analysed characteristics were the dynamic friction coefficient (CoF), the wear rates and the hardness (HRC) tests. Based on the collected data, a specific characterisation was made for EN 1.4136 stainless steel heat-treated in a solar furnace. By applying the thermal treatments in the solar furnace, the hardness values have been increased (of about 55%) and the average wear rates have decreased compared to the base material. [ABSTRACT FROM AUTHOR]

ABSTRACT: In this article, poly(vinyl chloride) (PVC) sandwich‐structured hybrid composites with amorphous calcium carbonate and wood‐filled cores were obtained by compression molding. It has been determined that wood addition up to a weight ratio of 33% reported to the total filler amount is beneficial in improving both the inter‐filler and filler‐matrix interfacial adhesion, which alongside with the promoting of the amorphous PVC matrix crystallization is responsible for an increase up to 34% in the flexural strength of the composites, compared to unfilled PVC. The hybrid filled composites present up to 35% lower friction coefficients and up to 20% higher Brinell hardness values than the composites filled with calcium carbonate alone. Subsequently, wood addition determines an increase in the oxidation onset temperature for PVC and an increase with up to 20% in the sound and thermal‐insulative properties of the composites, compared to unfilled PVC. The dominating dispersive part of the composites surface energy aids in improving the mass and dimensional stability of the assembly to both water and dilute hydrochloric acid aqueous solutions. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46317. [ABSTRACT FROM AUTHOR]

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Balsa wood is a natural cellular material with an excellent resistance-toweight ratio that is ideal for manufacturing the core of sandwich structures. In this study, sandwich specimens with a carbon-fiberreinforced polymer (CFRP) skin and a balsa wood core were tested with static and dynamic loading. Three-point flexural tests in static regime determined the mechanical characteristics of the CFRP-balsa specimens that were needed for subsequent fatigue strength tests. Also, experimental research was performed on the Charpy impact response of the CFRP-balsa sandwich specimens. This study implemented an accelerated fatigue testing method to identify and predict the mean fatigue life of the CFRP-balsa sandwich specimens subjected to cyclic fatigue via three-point flexural tests. Using the accelerated fatigue and the three-point flexural testing methodology on the CFRP-balsa sandwich specimens, the testing period was reduced by 11.9 times, and thus the material costs necessary for the tests were also reduced. Also, the breaking surfaces were analysed to reveal the failure modes of CFRP-balsa specimens subjected to static and fatigue tests at threepoint flexural and at impact tests. [ABSTRACT FROM AUTHOR]

The use natural fibres in composites in replacement of mineral-inorganic fillers, is of great interest in the view of the reduction in the use of petroleum-based, nonrenewable resources, and in general in a more intelligent utilization of environmental and financial resources. Material revolution of this century may be provided by green composite materials. Sustainability, design, industrial ecology, eco-efficiency, and green chemistry can form the principles that are guiding the development of a new generation of "green" materials. The paper presents some application devices with green composite sustainable materials for automotive industry. [ABSTRACT FROM AUTHOR]

This study deals with the processing of Cu-TiC-graphite hybrid composites prepared by powder metallurgy route, through mechanical alloying and microwave sintering. Microwave sintering has gained worldwide acceptance as a new method for heating and sintering of a variety of materials as it offers many advantages compared with conventionally sintering like high heating rates, short processing time and lower sintering temperatures with finer microstructure and lower environmental hazards. Green metal based compacts were exposed to high intensity microwave fields and their densification mechanisms, microstructure and mechanical properties were investigated. [ABSTRACT FROM AUTHOR]

This paper deals with the processing, microstructure, mechanical properties and wear behaviour of copper based hybride composites reinforced with TiC and graphite particles. Elemental powders of copper (Cu), titanium carbide (TiC) and graphite (C) were mechanically alloyed in a planetary ball mill, compacted and sintered using spark plasma sintering technique. The addition of alloying elements in the copper have increased the composite hardness. Pin-on-disc was used to evaluate the tribological properties under testing parameters of 12N normal load and 10cm/s sliding speed. The microstructural study revealed that the titanium carbide and graphite particles were uniformly distributed in the matrix phase. [ABSTRACT FROM AUTHOR]

Thermal spraying is the process of applying coatings of high performance materials, such as metals, alloys, ceramics, onto more easily worked and cheaper base materials. Electric arc spray technique is a thermal spray process that uses a direct current electric arc. This work focuses on the microstructural and hardness properties of Ni-2Al claddings deposited on steel, iron and duralumin alloy substrates by using the Electric Arc Thermal Spraying method. The microhardness of the Ni-2Al coatings and of the three substrate materials was measured with a Vickers indenter tester. For microstructural characterization Nikon Eclipse MA100 inverted metallurgical microscope was used. [ABSTRACT FROM AUTHOR]

Flowforming technology has emerged as the most advanced metal forming technique due to its manifold advantages over conventional metal forming techniques such as extrusion and tube drawing. It offers remarkable utilization of metal, high strength high precision rotationally symmetric components with very high specific strength, excellent surface finish and close dimensional tolerances within the envelope of reasonable economics. The process is quite versatile in view of the fact that a great variety of tubular parts, flexibility provided for complicated parts nearer to net shape, can be manufactured with basically the same tooling, enabling customers to optimise designs and reduce weight and cost, all of which are vital. The ever-increasing strength demands of automotive industries, defense and aerospace sectors have given considerable impetus to research work in this area. In this paper, process details of flowforming, the major experimental studies reported in literature have been reviewed. The study brings out the potential and the ever increasing applications of this manufacturing technique in defense, automotive and aerospace sectors. [ABSTRACT FROM AUTHOR]

The present paper aims to be a mathematical modelling and an optimization of resin type composite materials reinforced with Stratimat fiber glass. The modelling and optimization of these composites are based on the results obtain previously from the bending test. There was used Vinalkyd 25 PE-ATA type resin reinforced with Tissue fiber glass with the specific weight of 300 and 500 [g/m²] with 3, 5 and 7 layers and Wire netting 0,8 with the specific weight 400 [g/m²] and a number of 3, 5 and 7 layers. These composites are materials which can be tailored to suit almost in any function in industry and have a very wide spread in many other areas of activity of the most diverse. [ABSTRACT FROM AUTHOR]

Industry presents growing interest in exploitation of advantages provided by foam structure. Solid foam has outstanding low weight as a great part of its volume consists of gas while the rest is of solid material incorporating structural elements. They have high strength and load ability comparing to their small mass/relative density. Solid foams can be used as thermal and sound insulators and energy absorbers as well. Owing to wide variety of applications foreseen and to rising industrial demands research works of foams have got great importance recently. Metal foam production was first realized about the early nineties last century. An example of aluminum foam application is for sound absorption of long tunnels -- being more advantageous than plastic foam used before regarding its fire resistance property as well. Open cell nickel foams have important role by element production using their vast inner surface as catalyst carrier. The first such production plant is already operating in China established by Canadian/Brazilian owners. The paper presents some experimental data for obtaining Al and Ni foams for cars catalyst reactor applications. [ABSTRACT FROM AUTHOR]

In this paper the authors propose to obtain many types of composite materials made from resin reinforced with glass fiber. These materials have been used to manufacture plates. There were obtained 34 types of composite materials for each resin, modifying numbers of layers of insertion (3, 5, 7), types of inserts (stratimat, tissue, wire netting) and specific weight of materials (300, 400, 450, 500 and 600 g/m²). Similar composite materials were used in foundry to manufacture casting patterns [3]. The theme that was chosen for the post-doc project aims to develop the optimum technology and methodology of elaborating materials in order to obtain thin-walled products with enhanced mechanical characteristics so that they are suitable for other domains as well [1]. [ABSTRACT FROM AUTHOR]

The additive manufacturing process is one of the technical domains that has had a sustained development in recent decades. The designers' attention to equipment and materials for 3D printing has been focused on this type of process. The paper presents a comparison between the results of the bending tests and those of the simulation of the same type of stress applied on 3D-printed PLA and PLA–glass structures. The comparison of the results shows that they are close, and the simulation process can be applied with confidence for the streamline of filament consumption, with direct consequences on the volume and weight of additive manufactured structures. The paper determines whether the theories and concepts valid in the strength of materials can be applied to the additive manufacturing pieces. Thus, the study shows that the geometry of the cross-section, by its shape (circular or elliptical) and type (solid or ring shaped), influences the strength properties of 3D-printed structures. The use of simulation will allow a significant shortening of the design time of the new structures. Moreover, the simulation process was applied with good results on 3D-printed structures in which two types of filaments were used for a single piece (structure). [ABSTRACT FROM AUTHOR]

A successful bone-graft-controlled healing entails the development of novel products with tunable compositional and architectural features and mechanical performances and is, thereby, able to accommodate fast bone in-growth and remodeling. To this effect, graphene nanoplatelets and Luffa-fibers were chosen as mechanical reinforcement phase and sacrificial template, respectively, and incorporated into a hydroxyapatite and brushite matrix derived by marble conversion with the help of a reproducible technology. The bio-products, framed by a one-stage-addition polymer-free fabrication route, were thoroughly physico-chemically investigated (by XRD, FTIR spectroscopy, SEM, and nano-computed tomography analysis, as well as surface energy measurements and mechanical performance assessments) after sintering in air or nitrogen ambient. The experiments exposed that the coupling of a nitrogen ambient with the graphene admixing triggers, in both compact and porous samples, important structural (i.e., decomposition of β-Ca3(PO4)2 into α-Ca3(PO4)2 and α-Ca2P2O7) and morphological modifications. Certain restrictions and benefits were outlined with respect to the spatial porosity and global mechanical features of the derived bone scaffolds. Specifically, in nitrogen ambient, the graphene amount should be set to a maximum 0.25 wt.% in the case of compact products, while for the porous ones, significantly augmented compressive strengths were revealed at all graphene amounts. The sintering ambient or the graphene addition did not interfere with the Luffa ability to generate 3D-channels-arrays at high temperatures. It can be concluded that both Luffa and graphene agents act as adjuvants under nitrogen ambient, and that their incorporation-ratio can be modulated to favorably fit certain foreseeable biomedical applications. [ABSTRACT FROM AUTHOR]