Damping Properties of Hybrid Composites Made from Carbon, Vectran, Aramid and Cellulose Fibers

Hybridization of carbon fiber composites can increase the material damping of composite parts. However, there is little research on a direct comparison of different fiber materials—particularly for carbon fiber intraply-hybrid composites. Hence, the mechanical- and damping properties of different carbon fiber intraply hybrids are analyzed in this paper. Quasi unidirectional fabrics made of carbon, aramid, Vectran and cellulose fibers are produced, and their mechanical properties are analyzed. The material tests show an increased material damping due to the use of Vectran and aramid fibers, with a simultaneous reduction in strength and stiffness.

Textronics spacer knitted material tests as a key element of the diagnostic system that monitors above the proper level of seat vibration

This research is focused on the construction and examination of a prototype of a spacer knitted material with integrated sensors. The combination of textiles with elements of electronics, computer science, and a knowledge of automation is called textronics. This type of material has been proposed as a component of diagnostic systems to monitor the extension level of vibration in employee seats at selected workstations or in children’s chairs. The purpose of the diagnostic system is to improve personal protective equipment (PPE) and increase employee safety. The spacer knitted material was tested with vibration frequencies in the range of 0–40 Hz to develop metrological properties under reproducible and repeatable conditions. The tested spacer knitted material meets the requirements of sensory properties such as vibration. The tested material is characterized by the following metrological parameters: total uncertainty U = 4.5%, sensitivity Sa = 0.64 [V/s2/m] and excitability threshold of 5 Pa with simultaneous high coefficient of low-frequency vibration damping of effective amplitude transmissibility (SEAT) = 2.3. Spacer knitted materials are modern constructs that enable the creation of new hybrid structures that have other properties, e.g., sensory suppression, in addition to spatial form.

Material characteristics of push-out tests

Two types of push-out tests were carried out at the Centre of Research and Innovation in Construction, the Technical University of Košice - one at a composite based on steel continuous shear connector and the second one at the same connector, however made of glass-laminate material. For further research, the material characteristics of the material used needed to be found. In this article, the material tests performed as well as their results are presented.

Chemical Composition of Alloys as Primary Material Property Influencing the Accuracy of Measurements Obtained in Energy-Dispersive X-Ray Spectroscopy (EDS), Wavelength-Dispersive X-Ray Spectroscopy (WDX) and X-Ray Fluorescence (XRF)

The properties of the material affect the quality of the manufactured product. Before transferring the finished product to the production phase and sending it to the customer, material tests should be carried out. Examined material properties such as chemical composition, phase composition, grain boundaries influence results obtained after measurements of the chemical composition. The spectrometers used in SEM or as separate XRFs can be compared due to the principle of operation. The main difference in EDS/WDX or XRF is the types of a beam that excite the characteristic X-rays radiation peaks. Unfortunately, both types of spectroscopy have limitations due to materials properties such as the application light chemical elements in alloys an example of B. As well as small quantities of chemical elements in used alloys that affect the obtained results.

STUDENT DIFFICULTIES IN SOLVING MATHEMATICS QUESTIONS BASED ON MATHEMATICAL LOGIC INTELLIGENCE DURING THE COVID-19 PANDEMIC

This study aims to analyze students' difficulties in solving mathematical problems based on mathematical logic intelligence. The population of this research is the fourth-semester students of Mathematics Education, Universitas PGRI Madiun, totaling 52. While the subjects of this research are 3 students based on mathematical logic intelligence. The subject is taken by one student each from high, medium, and low mathematical logic intelligence. This research is descriptive qualitative research using the triangulation technique. Data collection techniques used are tests, interviews, and documentation. Instruments in the form of advanced mathematical material tests and tests of mathematical logic intelligence. The data analysis technique uses data reduction, data presentation, and conclusion drawing. The conclusion in this study is that subjects who have high mathematical logic intelligence have no difficulty in working on problems, subjects of mathematical logic intelligence are having difficulty at the stage of re-examining their answers, and subjects of low mathematical logic intelligence have difficulty in solving problems properly and have not been able to re-examine the answers. Penelitian ini bertujuan untuk menganalisis kesulitan mahasiswa dalam menyelesaikan soal matematika berdasarkan kecerdasan logika matematika. Populasi penelitian ini mahasiswa semester IV Pendidikan Matematika Universitas PGRI Madiun yang berjumlah 52. Sedangkan subjek penelitian ini adalah 3 mahasiswa berdasarkan kecerdasan logika matematika. Subjek tersebut diambil masing-masing satu mahasiswa dari kecerdasan logika matematika tinggi, sedang dan rendah. Penelitian ini merupakan penelitian kualitatif deskriptif dengan menggunakan triangulasi teknik. Teknik pengumpulan data yang digunakan adalah tes, wawancara dan dokumentasi. Instrumen berupa tes materi matematika lanjut dan tes kecerdasan logika matematika. Teknik analisis data menggunakan reduksi data, penyajian data, penarikan kesimpulan. Kesimpulan pada penelitian ini adalah subjek yang memiliki kecerdasan logika matematika tinggi tidak mengalami kesulitan dalam mengerjakan soal, subjek kecerdasan logika matematika sedang kesulitan pada tahap memeriksa kembali jawabannya dan subjek kecerdasan logika matematika rendah kesulitan dalam menyelesaikan soal dengan baik dan belum mampu memeriksa kembali jawabannya.

Numerical design studies of meander structures for self-expanding absorbable stents

Absorbable stents made of poly-L-lactic acid (PLLA) exhibit inferior mechanical properties compared with metal based devices. Therefore, design optimization by means of finite element analysis (FEA) plays an important role in development of high performance absorbable stents. In the present study, three different meander structures made of PLLA material were compared in terms of their radial resistive force (RRF) using FEA. Material tests were performed to obtain input parameters of PLLA for the simulation. FEA was carried out to simulate the RRF and the length change of the meander structures as a function of the diameter. In addition, the numerical results were compared to the experimental outcome using corresponding meander based stents performing radial testing with a segmented head mechanism. Comparable high stresses occurred in the Ubends of the examined stent designs. In designs with a large radius of curvature less stress was observed while crimping. One meander structure developed comparatively higher structural resistance against radially acting forces, due to its curved strut design. In general, FEA revealed consistent results compared to the experimental investigations.

Flexural Behavior of T-Shaped UHPC Beams with Varying Longitudinal Reinforcement Ratios

In order to investigate the transverse flexural behavior of the UHPC waffle deck, a total of six T-shaped UHPC beams, with varying longitudinal reinforcement ratios, were tested and analyzed. The experiments, including material tests of UHPC and beam tests, were conducted. The material tests of UHPC revealed that strain-hardening behavior in tension was exhibited, and the ratio of uniaxial compressive strength-to-cubic compressive strength was 0.85. The beam tests showed that all the T-shaped UHPC beams, even without longitudinal rebar, exhibited ductile behavior that was similar to that of properly reinforced concrete beams. As the longitudinal reinforcement ratio increased, more flexural cracks developed and a larger load-carrying capacity was provided. Furthermore, the sectional analysis for the ultimate flexural capacity of T-shaped UHPC beams was conducted. Simplified material models, under tension and compression, for UHPC were developed. Based on the reverse calculation from the experimental result, the relation between reduction factor to the ultimate tensile strength of UHPC, and longitudinal reinforcement ratios was formulated. As a result, the predictive equations for the ultimate flexural capacity of T-shaped UHPC beams were proposed, and agreed well with the experimental results in this study and existing studies, which indicates good validity of the proposed equations.

Modelling and analysis of the stability of a harbour wharf’s embankment with regards to its failure

The article presents the process of creating a computational model for the stability analysis of a harbour wharf’s embankment with regards to its failure. The described elements that were taken into account at the stage of data preparation are: historical analysis of the structure (structural calculations, and the calculations of the stability of the embankment), results of the author’s own soil and material tests (concrete, steel), environmental conditions (atmospheric and water), the possible load systems that acted on the facility, and also the results from the 3D model of the wharf’s structure. On this basis, five computational schemes were prepared for computer simulations of the stability of the embankment in a plain state of deformations. Various stages and conditions of its operation were taken into account. In conclusion, a possible course of the process of destruction of the structure of the harbour wharf, and the river embankment that cooperates with it, was proposed.

Imparting biocidal properties to insulating materials made of linen fibres

In this work, salicylic acid and copper sulfate were chosen as antimicrobial agents to impart biocidal properties to nonwoven materials. The conditions of the antibacterial finishing process were as follows: the aqueous solution of a biocidal composition of different concentration was applied by spraying to the surface of the material, then the drying and heat treatment was carried out at 180°C on the thermal conductor. A microbiological study was conducted to study the fungicidal activity of the treated material. Tests were also carried out on the toxic and dermal effects of non-woven material treated with salicylic acid and copper sulfate and demonstrated its safety to human health.

Pedagogical Consolidation of Pupil-Athletes’ Knowledge of Humanities

There appears to be the need to consolidate pupil-athletes’ knowledge of humanities (Ukrainian History, English, Ukrainian, Ukrainian literature), which greatly affect their emotional and value attitude towards the surrounding world, promote active life position and widen outlook, develop reading, linguistic and speech culture, enhance understanding of life meaning through the assimilation of ideals, universal values, norms of morality and patterns in behaviour culture. The research aims to disclose the impact of the developed system of assignments on the consolidation of knowledge of humanities in pupil-athletes in the process of training. The pedagogical experiment was conducted in Ukrainian comprehensive schools (142 participants in the experimental group and 150 participants in the control group). The diagnostic toolset includes questionnaires for identifying cognitive interest of pupils in humanities, questionnaires for teachers and parents, tests for identifying abilities to observe, concentrate attention, memorize and apply the content of educational material, tests for studying types of memory, methods of adolescents’ self-assessment, methods of unfinished sentences, notes, reading diaries, compositions. Thus, the indicator of creative nature in acquiring knowledge of humanities has increased (+ 19,1%) in the experimental group. Analyzing the results from the experiment, one can conclude that the designed system of assignments aimed at consolidating pupil-athletes’ knowledge of humanities has contributed to increasing the levels of their overall performance, responsibility and discipline.