Band 39, Heft 3

This investigation aims to elucidate friction and wear features of additively manufactured recycled-ABS components by utilizing neural network algorithms. In that sense, it is the first initiative in the technical literature and brings fused deposition modeling (FDM) technology, recycled filament-based products, and artificial neural network strategies together to estimate the friction coefficient and volume loss outcomes. In the experimental stage, to provide the required data for five different neural algorithms, dry-sliding wear tests, and hardness measurements were conducted. As FDM printing variables, layer thickness (0.1, 0.2, and 0.3 mm), infill rate (40, 70, and 100 %), and building direction (vertical, and horizontal) were selected. The obtained results pointed out that vertically built samples usually had lower wear resistance than the horizontally built samples. This case can be clarified with the initially measured hardness levels of horizontally built samples and optical microscopic analyses. Besides, the Levenberg Marquard (LM) algorithm was the best option to foresee the wear outputs compared to other approaches. Considering all error levels in this paper, the offered results by neural networks are notably acceptable for the real industrial usage of material, mechanical, and manufacturing engineering areas.

The current study investigated the potential application of agricultural waste chicken eggshell (CES) as a reinforcement in composites made of poly (lactic acid) (PLA). With the use of twin extruder and injection molding machine, polymer composites have been developed. The performance of the composites was assessed with respect to its mechanical, thermal, and wear properties. It was shown that the increase in eggshell content led to the increase in void content and water absorption. Despite the increase in void content, the mechanical properties, in particular, micro-hardness, tensile strength and flexural strength were significantly improved. Conversely, when the eggshell content increased from 0 to 30 wt%, the impact strength was decreased. A slight decrease in fracture toughness was observed. Thermal properties, such as thermal stability and thermal degradation temperature, were improved with an increase in eggshell content. PLA, PLA-CES-10, PLA-CES-20, and PLA-CES-30 composites exhibited increase in erosion rate by 13.8 %, 10 %, 9 %, and 6 %, respectively, when the impact velocity was increased from 30 m/s to 50 m/s. Data were analyzed statistically with one-way ANOVA and post hoc Tukey’s HSD test ( α  < 0.05). Overall, PLA/eggshell based polymer composites performed exceptionally well, in addition to their environmental benefits, pollution control, waste utilization, and reduced production cost.

This study aims to investigate the effect of fiber diameter on the mechanical and water absorption characteristics of short bamboo fiber-reinforced polyester composites. Three different fiber sizes (180–250 µm, 250–500 µm, and 700–1000 µm) were used to prepare composites with varying fiber loadings of 10 wt.%, 20 wt.%, and 30 wt.%. The fabricated composites were cut to standard dimensions, and tension tests, impact tests, and water absorption tests were performed. Reproducible results were obtained, revealing that using fibers of smaller diameter (180–250 µm) increased the tensile strength of the composite by 20 % compared to composites with larger diameter fibers (700–1000 µm), while the tensile modulus showed a 22 % enhancement with decreasing fiber diameter. Composites with larger diameter fibers exhibited more defects (voids and matrix detachment), as revealed by SEM analysis of fractured surfaces. The impact strength of composites with a diameter size of 700–1000 µm increased by 33 % compared to composites reinforced with the smallest fiber diameter. Water absorption of the composites was also studied by long-term immersion in water, showing that water intake was high initially, reaching a saturation point after a certain time interval. The absorbed water values indicated that composites with the smallest diameter (180–250 µm) showed maximum water intake due to the creation of more water intake sites (increased interfacial area), while composites with the largest diameter fibers (700–1000 µm) exhibited the least water absorption as the interaction region between fibers and matrix was reduced.

This study introduces a novel approach by incorporating pristine ZnO nanorods and Ag nanoparticles decorated ZnO nanorods into a polyurethane foam matrix. This synergistic combination aims to enhance the foam’s antibacterial properties while investigating its impact on mechanical strength. Nanoparticles and prepared nanopolymer were characterized by different methods like XRD, TEM, SEM, and EDS. The mechanical characteristics and antibacterial properties of prepared polyurethane composites were investigated in the presence of Escherichia coli and Bacillus subtilis . A much higher level than reported in the literature was found for PU films filled with ZnO nanorods. Incorporating nanoparticles into polyurethane nanocomposites has been demonstrated to significantly improve polyurethane’s antibacterial properties. The results revealed that ZnO/PU antibacterial efficiency decreased with increasing ZnO nanofiller content, while AgNPs@ZnO/PU composite antibacterial efficiency increased with increasing AgNPs@ZnO nanofiller content. Also, the weak coordinate bond between ZnO and Ag in the PU chain extender was demonstrated. Increasing the ZnO content to 1.4 wt% resulted in greater Young’s modulus and tensile strength, which increased when the ZnO content was increased further. Such a dual-functional enhancement holds promise for applications requiring both antimicrobial efficacy and mechanical integrity.

F-44 phenolic epoxy fibers were produced through high-temperature dry spinning utilizing F-44 phenolic epoxy resin as the base material, combined with n-butanol and ethylenediamine (EDA) as the curing agent. The fibers were subsequently analyzed for their structural, thermal stability, microstructural, and mechanical properties using techniques such as Fourier transform infrared spectroscopy, micro-infrared imaging, thermogravimetric analysis, nuclear magnetic resonance, scanning electron microscopy, and fiber strength testing. The limitations of phenolic resins, including high brittleness, poor toughness, and low elongation at break, restrict their potential applications, necessitating modifications to broaden their utility. Research findings indicate that modifying EDA induces a ring-opening reaction of epoxy groups, thereby enhancing the resin’s structure and improving the thermal stability and mechanical properties of fibers. The thermal stability and mechanical strength of the fibers were optimized at an EDA concentration of 2.0 wt% and curing time of 30 min, resulting in a tensile strength of 105 MPa and an elongation at break of 27.6 %.

Barium phytate (Pa–Ba) was prepared by phytic acid and barium carbonate, and then the flame-retardant modified polyurethane foam (PUF) was synergized with Pa–Ba and ammonium polyphosphate (APP). The flame retardant properties and thermal stability of the modified PUFs were investigated by thermogravimetric analysis, cone calorimetry (CONE) and smoke density (Ds). The results showed the modified PUF with the addition of 5 % Pa–Ba and 10 % APP (PUF-A10-PB5) had the highest integral programmed decomposition temperature and the activation energy, indicating that its thermal stability was better compared with other samples. In addition, PUF-A10-PB5 had the lowest total heat release under different radiation intensities, and it had the smallest Ds and the highest light transmittance under the flame and flameless condition. The current results indicated that PUF-A10-PB5 had better flame-retardant properties and thermal stability, which can provide a useful reference for future experimental studies on the flame retardant properties of phytate-modified PUF.

Natural composites are gaining attention among researchers due to its characteristics like low density, eco-friendliness, and cost-effectiveness. However, their performance falls short when compared to traditional materials, necessitating research focused on enhancing the strength of natural composites. The limited attention given by researchers to Terminalia arjuna fiber, a natural fiber, prompted an exploration to unveil novel scientific insights into Terminalia arjuna fiber-based composites. This study involved the creation of a natural composite through the hand layup process, combining Terminalia arjuna fiber and epoxy resin. Additionally, nanofiller like silica (SiO 2 ) were introduced as reinforcing agents. Various materials were fabricated for different weight percentages of fiber and particles. The assessment covered mechanical and water absorption characteristics. The composite composed of epoxy with 30 wt% Terminalia arjuna and 2 wt% SiO 2 showcased excellent mechanical properties, including high tensile strength (74 MPa), flexural strength (98 MPa), impact resistance (6.6 kJ/m 2 ), and hardness (90 shore-d). Furthermore, it demonstrated minimal water absorption (18.4 % after 10 days). This research suggests that the epoxy/ Terminalia arjuna /2 wt% SiO 2 composite could be a preferred choice for industrial applications due to its outstanding performance.

The objective of this research work is to examine the effect of mixing operation in the reinforcement of linear low density polyethylene (LLDPE) with almond shell powder (ASP). Two groups of bio-composites mixed in solid state and melt extrusion state were developed by the standard thermo compression molding process. For each group of bio-composites developed, the mass percentage of ASP was varied from 5 % to 40 %. Tensile and friction tests and micro structural analyzes were carried out. The main results show that the addition of ASP particles: decreases the maximum tensile stress and increases the rigidity of the two types of bio-composites produced. A significant improvement was observed in terms of maximum stress and Young’s modulus of the bio-composites mixed in the molten state compared to those mixed in the solid state. Microscopic observations concluded that the melt-blended ASPs were better covered by the LLDPE matrix and the dispersion was successfully achieved. Friction tests have shown an improvement in tribological performance thanks to the addition of an optimal percentage of ASP equal to 20 % in the case of bio-composites mixed in the molten state. From this research work, it can be concluded that the LLDPE/ASP homogenization method influences the mechanical and tribological properties of bio-composites.

An important machine setting parameter of the injection moulding process is the injection velocity, which influences the local process parameters in the mould cavity and as a result the final part properties. In order to avoid surface defects by too low or too high melt front velocities along the flow path, profiling of the injection velocity can be necessary. Therefore, in previous work, a methodical approach has been developed, which calculates an injection velocity profile that can be set directly at the injection moulding machine, in order to gain a constant melt front velocity along the flow path. Using the existing approach, two different part geometries are injection moulded with an injection velocity profile from two different materials. The resulting microscopic and macroscopic part properties are evaluated and compared with the samples produced at a constant injection velocity. By keeping the melt front velocity constant, the surface quality can be specifically influenced, while other properties are hardly affected by profiling the injection velocity.