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20 pages, 4352 KiB

Open AccessArticle

Synergistic Effects of Dielectric Barrier Discharge Plasma Treatment on Hemp Fiber Surface Modification and Mechanical Properties of Hemp-Fiber-Reinforced Epoxy Composites

by Choncharoen Sawangrat, Kittisak Jantanasakulwong, Jonghwan Suhr, Kannikar Kaewapai, Thidarat Kanthiya, Parichat Thipchai, Pornchai Rachtanapun and Pitiwat Wattanachai

Appl. Sci. 2025, 15(5), 2818; https://doi.org/10.3390/app15052818 - 5 Mar 2025

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Abstract

This study focused on improving the mechanical properties of hemp-fiber-reinforced epoxy (HFRE) composites by modifying the surface of hemp fibers (HFs) using dielectric barrier discharge (DBD) plasma treatment. By exposing the fibers to different gas mixtures Ar, Ar+N₂, and Ar+O₂ [...] Read more.

This study focused on improving the mechanical properties of hemp-fiber-reinforced epoxy (HFRE) composites by modifying the surface of hemp fibers (HFs) using dielectric barrier discharge (DBD) plasma treatment. By exposing the fibers to different gas mixtures Ar, Ar+N₂, and Ar+O₂, the surface of the fibers was altered, adding functional groups, increasing surface roughness, and improving crystallinity. The researchers created HFRE composites using both untreated and plasma-treated HF, and then tested their mechanical properties. The results revealed that Ar+O₂ plasma treatment boosted both the tensile strength (by 15.2%) and energy absorption of the composites. To fine-tune the process, the response surface methodology (RSM) was used to determine the most important factors for optimizing the treatment: input power and treatment time. The ideal conditions were found to be 162.63 W of power and 10 min of treatment. These findings highlight the potential of DBD plasma as a reliable method for modifying the surface of hemp fibers, even with changes in the setup or reactor design. Overall, this approach shows great promise for industrial applications, providing an effective way to improve the strength and durability of HFRE composites for a variety of uses. Full article

(This article belongs to the Special Issue Modernly Designed Materials and Their Processing)

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20 pages, 7629 KiB

Open AccessArticle

Statistical Evaluation of Effect of Shape Imperfections on Buckling Load of Carbon Fiber-Reinforced Plastic Thin-Walled Cylinders

by Jingxuan Bao, Atsushi Takano, Ryuta Kitamura and Takuma Masai

Appl. Sci. 2025, 15(4), 2094; https://doi.org/10.3390/app15042094 - 17 Feb 2025

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Abstract

Thin-walled cylinders made from carbon fiber-reinforced plastic (CFRP) were measured using a laser displacement sensor and subjected to load tests. The effects of shape imperfections in the circumferential and axial directions, the radius–thickness ratio (r/t), and the offset compression [...] Read more.

Thin-walled cylinders made from carbon fiber-reinforced plastic (CFRP) were measured using a laser displacement sensor and subjected to load tests. The effects of shape imperfections in the circumferential and axial directions, the radius–thickness ratio (r/t), and the offset compression loads on the knockdown factor (KDF), which is the ratio of the experimental and theoretical buckling loads, were investigated. A statistical evaluation of various trends relating to the KDF and the amplitudes of the shape imperfections was conducted. The buckling load test on the cylinders showed large deviations and scatter between theory and experiment. It is known that shape imperfections are one of the key factors affecting KDF. The shape imperfection induces a local stress concentration and/or local buckling, and they may induce premature buckling. We found a correlation between the KDF and shape imperfections in the circumferential and axial directions and r/t. The KDF did not have a simple correlation with the direction of offset compression loads, the direction of the maximum and minimum amplitude of local shape imperfections, or offset distance. Full article

(This article belongs to the Special Issue Modernly Designed Materials and Their Processing)

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20 pages, 6557 KiB

Open AccessArticle

Shape Optimization of Structures by Biological Growth Method

by Jozef Bocko, Ingrid Delyová, Ján Kostka, Peter Sivák and Milan Fiľo

Appl. Sci. 2024, 14(14), 6245; https://doi.org/10.3390/app14146245 - 18 Jul 2024

Cited by 1 | Viewed by 1319

Abstract

Structural element shape optimization based on the biological growth method is increasingly used nowadays. This method consists of two main methods: topological optimization (soft kill option—SKO) and shape optimization (computer-aided optimization—CAO). This paper presents the solution procedures for both shape optimization and topological [...] Read more.

Structural element shape optimization based on the biological growth method is increasingly used nowadays. This method consists of two main methods: topological optimization (soft kill option—SKO) and shape optimization (computer-aided optimization—CAO). This paper presents the solution procedures for both shape optimization and topological optimization. In applying these methods, first of all, a certain stress norm must be established, where the most appropriate and most used criterion is the equivalent stress according to von Mises. The application of the mentioned optimization methods is illustrated by several examples. The aim was to compare the change in volume or mass and the maximum stress of the structural elements between the different designs: the initial design, the design after topological optimization, and the design after shape optimization. Full article

(This article belongs to the Special Issue Modernly Designed Materials and Their Processing)

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15 pages, 5955 KiB

Open AccessArticle

Comparison of the Properties and Structure of Montmorillonites Modified with Polyvinylpyrrolidone

by Volodymyr Krasinskyi, Ludmila Dulebova, Rafał Malinowski, Krzysztof Bajer and Oksana Krasinska

Appl. Sci. 2024, 14(7), 2983; https://doi.org/10.3390/app14072983 - 2 Apr 2024

Cited by 1 | Viewed by 1366

Abstract

The modification method of aluminosilicate clays and the modifier content have a decisive influence on the structure and properties of the obtained nanocomposites. Therefore, the development and research of new techniques of nanoclays modification are of great importance for polymer nano-chemistry. The work [...] Read more.

The modification method of aluminosilicate clays and the modifier content have a decisive influence on the structure and properties of the obtained nanocomposites. Therefore, the development and research of new techniques of nanoclays modification are of great importance for polymer nano-chemistry. The work studied the modification of montmorillonite (MMT) using polyvinylpyrrolidone (PVP) in an aqueous colloidal solution with the subsequent separation of three separate fractions of the solution according to the previously developed method. The influence of the initial mass ratio of components (MMT/PVP) on the structure and thermal properties of the modified MMT in each solution layer was determined. Scanning electron microscopy (SEM), X-ray diffraction (XRD), thermal gravimetry (TG), differential scanning calorimetry (DSC), and Fourier-transform infrared (FTIR) spectroscopy were used for research. It was established that the mass ratio of components in the initial solution has almost no effect on the structure of MMT in the top and middle solution layers, but significantly affects the yield of final products. Different structures can be obtained in the bottom layer of the solution. Still, intercalated MMT was obtained exclusively at the mass ratio of MMT/PVP = 1:2. In addition, the work investigated the structure and thermal properties of modified montmorillonites with the same PVP content, and it has been proven that such composites have dissimilar structures and properties when obtained by different methods. Full article

(This article belongs to the Special Issue Modernly Designed Materials and Their Processing)

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21 pages, 48365 KiB

Open AccessArticle

Evaluation of Non-Planar Tool Interaction in Milling of Shaped Surfaces Using a Copy Milling Cutter

by Ján Varga, Štefan Kender, Ľuboš Kaščák, Vladimír Rohaľ and Emil Spišák

Appl. Sci. 2024, 14(1), 285; https://doi.org/10.3390/app14010285 - 28 Dec 2023

Cited by 4 | Viewed by 1541

Abstract

When milling complex parts or curved surfaces, we encounter several problems that must be addressed in the production process. Various factors affect the quality and accuracy of production. The main objective of this paper was to analyse the size of the effective tool [...] Read more.

When milling complex parts or curved surfaces, we encounter several problems that must be addressed in the production process. Various factors affect the quality and accuracy of production. The main objective of this paper was to analyse the size of the effective tool diameter when machining a shaped surface concerning the selected position, namely at the perpendicular position of the tool. At the same time, the distribution of the engagement area on the tool surface was evaluated by extracting the area content and volume data at the point of contact. This study highlights the importance of the choice of finishing strategy in a CAM system. The results showed that the tool engagement size corresponded to the extracted data describing the area and volume for each tool position with regards to the curvature of the surface. The negative deviations obtained by the scanning method were due to machining near the tool centre, which was affected by the changing effective tool diameter. Full article

(This article belongs to the Special Issue Modernly Designed Materials and Their Processing)

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20 pages, 10941 KiB

Open AccessArticle

Comparison of Stress Concentration Factors Obtained by Different Methods

by Peter Sivák, Ingrid Delyová and Jozef Bocko

Appl. Sci. 2023, 13(24), 13328; https://doi.org/10.3390/app132413328 - 18 Dec 2023

Cited by 3 | Viewed by 3702

Abstract

This paper offers a study regarding regression and correlation analysis and intercomparison of stress concentration factors obtained from FEM analysis with factors imported from external sources. The procedure for obtaining the stress concentration factors is implemented and demonstrated on the shape configuration of [...] Read more.

This paper offers a study regarding regression and correlation analysis and intercomparison of stress concentration factors obtained from FEM analysis with factors imported from external sources. The procedure for obtaining the stress concentration factors is implemented and demonstrated on the shape configuration of an axially symmetric structural element with offset, tension loading. It is a typical representation of stress concentrators of the shape-discontinuity-dimension-load configuration applied in structural elements mainly from the engineering and construction fields. The data thus obtained are then subjected to regression and simple correlation analysis. Three regression models based on 2nd- and 3rd-degree polynomials and power function are applied. These results are further subjected to a detailed procedure of comparison with the values of the stress concentration factors obtained from two other independent sources. Finally, a detailed analysis of the possible reasons for the registered value deviations is performed. Full article

(This article belongs to the Special Issue Modernly Designed Materials and Their Processing)

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12 pages, 4556 KiB

Open AccessArticle

Influence of Noble Metals on the Microstructure and Properties of Biodegradable Mg-Nd-Zr Alloy

by Viktor Greshta, Vadim Shalomeev, Svitlana Bovkun, Ivan Petryshynets, Vasily Efremenko and Michail Brykov

Appl. Sci. 2023, 13(23), 12736; https://doi.org/10.3390/app132312736 - 28 Nov 2023

Cited by 1 | Viewed by 1430

Abstract

In this work, the approach to improve the mechanical properties of a biodegradable Mg-Nd-Zr alloy through modification with noble metals (Ag and Au) was proposed. The separate and combined influence of silver and gold on the macro- and microstructure of the alloy was [...] Read more.

In this work, the approach to improve the mechanical properties of a biodegradable Mg-Nd-Zr alloy through modification with noble metals (Ag and Au) was proposed. The separate and combined influence of silver and gold on the macro- and microstructure of the alloy was studied. A qualitative and quantitative assessment of the structural components of the alloy was carried out. It was shown that when modifying the melt, noble metals form the complex intermetallic phases which served as additional crystallization centers. It has been established that adding 0.05 to 0.1 wt.% of noble metals to Mg-based alloy increase the volume fraction of intermetallic compounds by ~1.5 times, shifting them towards smaller size groups with the simultaneous formation of spherical intermetallic compounds. The latter are located in the center of the grain proving them to be the additional nucleation sites. It was shown that complex modification (0.1% Ag + 0.1% Au) of a Mg-based alloy refined its structural components by ~1.5 times, increasing the strength by ~20%, and ductility by ~2 times due to the formation of the intermetallic compounds. The proposed technology for modifying cast biodegradable Mg-based alloys is feasible to be used for the manufacture of implants for osteosynthesis. Full article

(This article belongs to the Special Issue Modernly Designed Materials and Their Processing)

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27 pages, 23017 KiB

Open AccessArticle

Surface Quality Evaluation in the Milling Process Using a Ball Nose End Mill

by Ján Varga, Peter Ižol, Marek Vrabeľ, Ľuboš Kaščák, Mário Drbúl and Jozef Brindza

Appl. Sci. 2023, 13(18), 10328; https://doi.org/10.3390/app131810328 - 15 Sep 2023

Cited by 8 | Viewed by 2619

Abstract

Shaped surfaces are increasingly used in the field of mold-making for casting or injection molding, where future products include shapes with different curvatures. These are surfaces that form convex curves, concave curves, or a combination thereof. Given these machined surfaces, it is important [...] Read more.

Shaped surfaces are increasingly used in the field of mold-making for casting or injection molding, where future products include shapes with different curvatures. These are surfaces that form convex curves, concave curves, or a combination thereof. Given these machined surfaces, it is important to know the impact of the finishing strategies on these surfaces. This paper deals with the comparison of finishing milling strategies in the production of shaped surfaces and the analysis of different methods for the evaluation of surface topography. In addition, the experimental results evaluate the roughness of the machined surface and surface shape variations. The material used for the experiments was AlCu4Mg aluminum alloy, and Constant Z, spiral and spiral circle strategies were chosen for the finishing strategies. The evaluation of surface topography and surface roughness was carried out at three different specimen heights with respect to the tool’s contact with the machined surface. Full article

(This article belongs to the Special Issue Modernly Designed Materials and Their Processing)

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18 pages, 7377 KiB

Open AccessTechnical Note

Study of Noise Effect of Slag Storage Technology on Surrounding Environment

by Anna Yehorova and Ervin Lumnitzer

Appl. Sci. 2024, 14(4), 1678; https://doi.org/10.3390/app14041678 - 19 Feb 2024

Cited by 1 | Viewed by 1183

Abstract

The metallurgical sector is one of the important sectors of the Slovak economy. Its integral part is the storage of metallurgical waste, which is accompanied by noise that bothers the inhabitants of the surrounding urban areas. This paper focuses on the analysis of [...] Read more.

The metallurgical sector is one of the important sectors of the Slovak economy. Its integral part is the storage of metallurgical waste, which is accompanied by noise that bothers the inhabitants of the surrounding urban areas. This paper focuses on the analysis of the problem of noise propagation into protected areas located in the vicinity of the metallurgical plant. The paper describes a number of measurements that have been carried out at the slag landfill. Based on these measurements, simulations were performed using a mathematical model, and predictions of noise propagation in the exterior were made. Subsequently, noise reduction measures were proposed. The results obtained by the authors form a methodological basis for addressing such situations, since, during the solution, it was often necessary to deal with non-standard situations that were specific to the area of the technology addressed. This solution was then applied in real practice. Full article

(This article belongs to the Special Issue Modernly Designed Materials and Their Processing)

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