Norbert Abramczyk

Annually, 1.5 billion tires—composed of up to 90% vulcanized rubber—are discarded worldwide. Due to its complex and cross-linked structure, vulcanized rubber is extremely difficult to recycle and reprocess. This study investigates the potential application of recycled rubber as a core...

The article presents an analysis of the results obtained during the three-point bending test for seven variants of epoxy rubber–glass composites manufactured according to innovative technology. Different contents of rubber recyclate (3, 5, and 7%) and different methods of distribution of the recyclate in the composite structure (1, 2, and 3 layers with a constant share of 5% of the recyclate) were used in the tested materials. To determine the stress values at which critical failures of the tested materials are initiated in the bending test, an analysis was carried out using the Kolmogorov–Sinai (E_K-S) metric entropy calculations. The analysis results showed that for each of the above-mentioned variants of the tested epoxy–glass composites, the onset of critical changes occurring in the material structure occurs below the recorded values of the flexural strength Rmg. The decrease in the Rmg_K-S value in relation to Rmg is different for different material variants and depends mainly on the % content of rubber recyclate and the amount and method of decomposition of rubber recyclate in the layers of the analyzed materials. The research showed that the introduction of rubber recyclate into the composition of composites has a positive effect on their strength properties. This process allows for the efficient use of hard to degrade waste and opens up the possibility of using the newly developed materials in many industrial sectors.

Recycling of composite materials is an important global issue due to the wide use of these materials in many industries. Waste management options are being explored. Mechanical recycling is one of the methods that allows obtaining polyester–glass recyclate in powder form as a result of appropriate crushing and grinding of waste. Due to the fact that the properties of composites can be easily modified by adding various types of fillers and nanofillers, this is one of the ways to improve the properties of such complex composite materials. This article presents the strength parameters of composites with the addition of fillers in the form of polyester–glass recyclate and a nanofiller in the form of gamma-phase aluminum nanopowder. To analyze the obtained results, Kolmogorov-Sinai (K-S) metric entropy was used to determine the transition from the elastic to the viscoelastic state in materials without and with the addition of nanoaluminum, during a static tensile test. The tests included samples with the addition of fillers and nanofillers, as well as a base sample without any additives. The article presents the strength parameters obtained from a testing machine during a static tensile test. Additionally, the acoustic emission method was used during the research. Thanks to which, graphs of the effective value of the electrical signal (RMS) were prepared as a function of time, the parameters were previously identified as extremely useful for analyzing the destruction process of composite materials. The values obtained from the K-S metric entropy method and the acoustic emission method were plotted on sample stretching graphs. The influence of the nanofiller and filler on these parameters was also analyzed. The presented results showed that the aluminum nanoadditive did not increase the strength parameters of the composite with recyclate as a result of the addition of aluminum nanofiller; however, its addition influenced the operational parameters, which is reflected in a 5% increase in the UTS value (from 55% to 60%).

This paper presents the results of investigations of the mechanical properties of epoxy–glass composites with the addition of rubber recyclate. For the purposes of the study, seven variants of materials were designed and manufactured, which differed in terms of the percentage of recyclate content (3, 5 and 7%) and the way the recyclate was distributed in the composite (one, two and three layers with a constant share of 5%). Tests of comparative mechanical properties were carried out using a static tensile test. As a result of the conducted tests, the following values were obtained for all variants of materials: tensile strength (R_m), Young’s modulus (E) and percentage relative strain ε. In addition, for a deeper analysis of the results obtained, statistical calculations of Kolgomorov–Sinai E_K-S metric entropy were performed on the experimental data sets, which were then analyzed. The results of the analysis indicate that the application of metric entropy calculations E_K-S can be helpful in identifying changes in the internal structure of the composite material that occur during its loading, and which do not manifest themselves in any other tangible way. The data obtained as a result of the research can be used to optimize production processes and to determine the further direction of development of epoxy–glass composites with the addition of rubber recyclate, while saving time and resources.

The study aimed to analyse the influence of aluminum powder on the mechanical properties of polyester-glass composites. Composite materials were made of glass fibres with random fibre direction and polyester resin with the addition of aluminum powder as a filler. The strength parameters of materials obtained during the static tensile test and hardness test were compared. The results were subjected to statistical analysis, taking into account the change in the amount of filler, microstructure was also observed using optical microscopy. An analysis of the results showed that the addition of aluminum powder amounting to 2% of the weight of the composites reduces their hardness and, at the same time, the longitudinal modulus of elasticity.The addition of aluminum powder amounting to 5% and 10% of the weight of the composites increased the hardness of the composites while reducing the Young's modulus. The values of hardness measurements were subjected to statistical analyses at significance level α = 95. The Shapiro-Wilk test confirmed that the hardness variables for all tested samples were in normal distributions, and therefore the most powerful parametric tests were used to test the differences. Using the Student's t-test, it was confirmed that between pairs of variables in configurations: a standard sample with a modified sample, for all tested samples there are significant statistical differences in the distributions of hardness values. Studies have shown that the modification of the mechanical and strength properties of composite materials, through the use of an aluminum filler, makes it possible to obtain materials with variable parameters that can be useful and attractive in many new areas, depending on the application and user requirements. Celem pracy była analiza wpływu proszku aluminiowego na właściwości mechaniczne kompozytów poliestrowo-szklanych. Materiały kompozytowe wykonano z włókien szklanych o losowym kierunku włókien oraz żywicy poliestrowej z dodatkiem proszku aluminiowego jako wypełniacza. Porównano parametry wytrzymałościowe materiałów uzyskane podczas statycznej próby rozciągania i próby twardości. Wyniki poddano analizie statystycznej, biorąc pod uwagę zmianę ilości napełniacza, obserwowano także mikrostrukturę za pomocą mikroskopii optycznej. Analiza wyników wykazała, że dodatek proszku aluminiowego w ilości 2% masy kompozytów powoduje zmniejszenie twardości przy jednoczesnym zwiększeniu modułu sprężystości wzdłużnej. Dodatek proszku aluminiowego w ilości 5% i 10% masy kompozytów spowodował zmniejszenie twardości kompozytów przy jednoczesnym zwiększeniu modułu Younga. Wartości pomiarów twardości poddano analizom statystycznym na poziomie istotności α = 95. Test Shapiro-Wilka potwierdził, że zmienne twardości dla wszystkich badanych próbek miały rozkłady normalne, dlatego do sprawdzenia różnic wykorzystano najsilniejsze testy parametryczne. Za pomocą testu t-Studenta potwierdzono, że pomiędzy parami zmiennych w konfiguracjach: próbka standardowa i próbka zmodyfikowana, dla wszystkich badanych próbek występują istotne statystycznie różnice w rozkładach wartości twardości. Badania wykazały, że modyfikacja właściwości mechanicznych i wytrzymałościowych materiałów kompozytowych, poprzez zastosowanie napełniacza aluminiowego, pozwala na otrzymanie materiałów o zmiennych parametrach, które mogą być użyteczne i atrakcyjne w wielu nowych obszarach, w zależności od zastosowania i wymagań użytkownika.

Composites are materials that are widely used in industry, including yachting, railway and aviation. The properties of these materials can be modified by changing the type of reinforcement, the type of matrix, as well as the use of additives in the form of fillers and nanofillers that improve their mechanical or specific parameters. Due to the fact that these materials are often used for important structures, computational models using FEM tools may not be sufficient to determine the actual strength parameters, and what is more, to check them during operation. When designing structures made of composite materials, it is necessary to use high safety factors due to their behavior under several different types of loads, which is still difficult to determine precisely. This situation makes these structures much heavier and characterized by much higher strength properties than those that would actually be needed. In this article, the Kolmogorov-Sinai (K-S) metric entropy was used to determine the transition from the elastic to the viscoelastic state in GFRP (glass fiber reinforced polymer) composite materials without and with the addition of nanoaluminum, during a static tensile test. Additionally, the acoustic emission method was used during the research. This signal was further processed, and graphs were made of the number of events and the amplitude as a function of time. The obtained values were plotted on tensile graphs. The influence of the nano-filler on these parameters was also analyzed. The presented results show that it is possible to determine additional parameters affecting the strength of the structure for any composite materials.

Currently, there is a noticeable trend of modifying new materials by using additives from the recycling of harmful waste. This is to protect the environment by using waste to produce composites and at the same time to reduce the cost of their production. The article presents an analysis of the impact of the use of rubber recyclate obtained from the utilization of car tires as a sandwich layer of epoxy–glass composites and its impact on the strength parameters of the composite. The presented research is an extension of the previously conducted analyses on composite materials modified with the addition of rubber recyclate. The four variants of the materials produced contained the same percentage amount of rubber recyclate, but differed in the way it was distributed and the number of layers. Static tensile tests as well as impact strength and kinetics of damage to samples made with and without the addition of recyclate were carried out. Observation of the structures of the materials with the use of SEM was also performed. A significant influence of the method of distributing the recyclate in layers on the strength parameters of the materials was found. In the case of composites with three and two sandwich layers of recyclate, more favorable results were obtained compared to the blank sample. In addition, the values of the impact strength measurements were subjected to statistical analysis at the significance level of α = 95%. The distributions were tested for normality with the Shapiro–Wilk test, differences between pairs were tested with the Student’s t-test for dependent groups, and ANOVA differences were tested for independent groups. Using the Student’s t-test, it was confirmed that between the pairs of variables in the configurations reference sample and modified sample, there were significant statistical differences in the distribution of impact strength measurement results for all the analyzed materials. Statistical analysis showed a significant usefulness in the selection of the material with the best strength parameters and a significant role of statistical methods in the study of anisotropic materials.

The article describes an innovative post-weld surface finishing method, which is characterized by moving a specialized cutting tool along a butt weld. The aforementioned method is unique for the machining allowance, which is treated as the weld bead height and is removed in one step with one pass of the cutting tool. The tool is equipped on one side with linearly arranged tooth-shaped cutting elements, with the adjacent teeth height changing and increasing according to the direction of the feed. The non-standard geometry of the cutting tool enables the finishing of a heterogeneous post-weld surface with increased hardness. The results of studying the 2D profile parameters and the 3D stereometric characteristics of the surface roughness using the optical method are presented in the article. Test samples were made of S235JR steel and butt welded with the MMA, MIG, and TIG methods. Subsequently, the welding bead was ground and finished in accordance with the innovative method to flush the bead and the base metal’s surface. Additionally, residual stress analyses were performed using the X-ray diffraction method in the surface layers of the test samples. Based on the conducted research, the influence of the innovative finishing method on the surface quality is described.

The article presents a method of modifying the strength properties of epoxy–glass composite by changing the percentage composition of the matrix by the addition of rubber recyclate. Taking into account environmental protection and economic conditions in the process of recycling and utilisation of waste, it is advisable to look for applications of non-degradable waste materials. Based on epoxy resin, a glass mat with a random direction of fibres and rubber recyclate, a test material with different percentage compositions was produced. Samples from the manufactured materials were subjected to a static tensile test on a ZwickRoell testing machine using the ARAMIS SRX measuring system. In addition, CT (computerized tomography) scans of the inside of the samples were made using a ZEISS METROTOM 6 Scout tomograph, and observations of the internal structures were made using a scanning electron microscope. The use of optical and microscopic techniques enabled the precise determination of strength parameters of the examined composites and the analysis of the behaviour of samples under load. The analysis of deformations over time in the examined samples showed a beneficial effect of the addition of rubber recyclate on the elastic properties of the examined composites.