Background and Objectives: The aim of the research is to study the effect of ultrasound on the wettability of carbon fibers with a thermosetting binder and to determine the work of adhesion in the ...binder-fiber contact as part of the filament prepreg for additive technologies. Materials and Methods: Carbon fibers and carbon fiber roving with a width of 2 mm GG-200P were used in the research. Impregnation was carried out with ED-20 epoxy resin with a PEP hardener by pulling a harness at a speed of 10 mm/s through a gap of 2-3 mm between the endof the ultrasonic concentrator and the lower surface of the container with a binder. In total, 5 control and 5 experimental samples with a length of 300 mm were impregnated. Ultrasonic processing of samples was carried out on an experimental ultrasonic installation with an experimental ultrasonic generator controlled from a laptop and providing a discreteness of 10 Hz adjustment. The impregnation was carried out at a resonant frequency of 21650 Hz and an oscillation amplitude of the output end of the concentrator - 15 microns. The diameter of the output part of the concentrator was 14 mm, respectively, the length of the fiber bundle section was the same size at each time. After curing of the binder, the surface of the fibers was studied using a digital microscope Bresser LCD 50x-2000x at magnification x40 and x300. When impregnating control samples, the ultrasonic transducer of the installation was not included. Microphotographs were used to evaluate the wettability of the fibers with a binder under the influence of ultrasound and without ultrasound, and also to determine the edge angle of wetting and then - according to the Young - Dupree equation - the adhesion of the binder to the fiber surface. Results: The control bundle of carbon fibers is characterized by incomplete consolidation of fibers into a bundle, there are separate disoriented fibers, as well as separately existing conglomerates of fibers. Experimental bundles impregnated under the influence of ultrasound are monolithic structures with a continuous filling with a binder. At the same time, areas with inflows of the cured binder that violate the geometric shape of the prepreg are noted. Both control and experimental samples of harness are generally fully impregnated consolidated prepregs, there are no individual fibers or groups of fibers, which may be due to the initially regular structure of harness compared to randomly organized individual fibers into a thread. At the same time, in the control samples, the binder is unevenly distributed over the surface, individual inflows are noted, which indicates an insufficiently uniform impregnation of the harness. which is not observed on the prototypes. By calculating the adhesion performance for control and experimental samples using the experimentally obtained values of the wetting angle, it was found that its value is 44.71-48.98 mJ/m2 and 64.46-66.4 mJ/m2 , respectively, for control and experimental samples. Conclusion: A significant improvement in the wettability of the fibers with a binder has been found, manifested in a decrease in the wetting edge angle from 70-77° to 35-40°. Using the Young - Dupree equation, the adhesion of the binder to the fiber has been calculated and it has been shown that the effect of ultrasound during the impregnation of fibers increases the adhesion by an average of 39.7%
This investigation focused on obtaining samples from ceramic composite materials, based on the ZrO₂⁻20%Al₂O₃ system, using the additive layer-by-layer fusion technology for thermoplastic systems. The ...structure and phase composition of the initial powders were studied, experimental samples were produced, and the structure and properties of the experimental samples that were obtained using additive technologies were analysed. The measured static bending strength of the samples was 450 ± 70 MPa, microhardness was 14 GPa, and the elasticity modulus was 280 ± 25 GPa. The strength of these samples are slightly inferior to that of similar materials, obtained using Ceramic Injection Molding technology because our samples were characterised by the residual porosity of about 15%.
According to the technology of wire-arc additive manufacturing a nonequiatomic composition CoCrFeMnNi high-entropy alloy (HEA) was obtained. Deformation curves of samples in tension are plotted and ...analyzed after the HEA fabrication by the methods of wire-arc additive manufacturing (initial state) and after the electron-beam processing (EBP). The EBP results in a decrease in the HEA's strength and plastic properties. Along with a pit character of the fracture a presence of micropores and microlayerings are identified. A study of the HEA's fracture surface after the EBP except for regions with a ductile fracture mechanism revealed regions with a band (lamellar) structure. The area with a band structure increases with a growth in the beam electron density from 25% at 10 J/cm2 to 65% at 30 J/cm2. A diameter of separation pits in fracture bands varies in the limits (0.1–0.2) μm, which is considerably less than those of the remaining part of the HEA sample. An average size of crystallization cells formed in the EBP depends on the energy density of electron beam and increases from 310 nm at 15 J/cm2 to 800 nm at 30 J/cm2. A non-monotonous change in the scalar dislocation density, reaching a maximum value of ∼5.5 · 1010 cm-2 at a distance of 25 μm from the irradiation surface is revealed. It is suggested that defects being formed in surface layers in the EBP may be one of the reasons for decreasing the values of HEA strength and plasticity.
The purpose of the article is to analyse the manufacturing factors that affect the cost of manufacturing a part. Nowadays the cost of equipment used for metal 3D printing, as well as metal powders, ...are still very expensive. The cost of additive manufacturing of metal parts is mainly dependent on the volume of printing, therefore, reducing the volume of printing can lead to a significant reduction in the cost of manufacturing the part. Manufacturing of a metal shell, the cavity of which is filled with a cheap metal polymer, can be an excellent alternative to an all-metal part. The article provides a method for calculating the cost of manufacturing a lever part using various technologies: subtractive, additive, and composite part manufacturing technology. According to the calculated data, the dependence of the cost of manufacturing a part on piece time has been built, which can be interpreted as the amount of machining. The constructed linear dependence can give an idea of the effectiveness of the application of a particular technology for obtaining a part. In addition, non-economic factors affecting the possibility of using various technological processes for manufacturing a part are described.
Additive technologies are relatively new for the field of mechanical engineering, but they are extremely relevant and promising. Understanding the possibilities of such technologies and determining ...their place among established technologies is an important task today. The article analyzes the place of additive technologies, their capabilities in terms of shaping, creating extremely complex parts with a developed internal structure and surface structures. The possibilities provided by multi-material additive technologies are considered. The reasons for the paradoxical property of additive technologies to be invariant for the complexity of details are explained. The main opportunities and trends in the use of additive technologies in the design and manufacture of high-tech parts in mechanical engineering and biomedical engineering are analyzed.
This article introduces an innovative approach to significantly broaden the bandwidth of Cylindrical Dielectric Resonators. A four-element Camembert-Shaped Cylindrical Dielectric Resonator Antenna ...(CDRA) is presented, using an air gap separating the resonators to enhance the antenna bandwidth. The radiators, i.e., the DRA blocks, are made of high relative-permittivity ceramic material (εr = 25 & 30) and are excited by microstrip-line feed. The proposed methodology involves the strategic design of these resonators, incorporating dielectric materials to finely optimize the frequency response. Experimental validation demonstrates a remarkable improvement in bandwidth when compared to conventional methodologies. This novel technique holds immense promise for applications requiring wideband antennas. The demonstrated effectiveness of this approach not only addresses contemporary challenges but also opens up new avenues in antenna design, catering to the escalating demands of modern communication systems. In addition to the compact dimensions of the elementary radiating element, the separation distance between them, set at λ/4, enhances the array antenna overall size, and its gain is nearly 10 dBi. The proposed antenna covers cellular network applications such as UMTS mobile phone band around 2.1 GHz, as well as wireless DECT phone bands around 1.9 GHz, facilitating data transmission over short distances and beyond, with an impedance bandwidth of 20%.
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