Reinforcing the novolac matrix with glass fiber (GF) and graphite (Gr) was a promising method for producing high‐performance friction composites. In this context, the morphology of the matrix and ...additive particles used in the production of friction composites, microstructures, wear surfaces, and wear debris of friction composites were examined by scanning electron microscopy‐energy dispersive spectroscopy, while the crystal phases of the materials were scanned by X‐ray diffraction. Density measurements (Archimed's method), hardness, tensile behaviors, and thermal analyses (thermogravimetric analysis and differential scanning calorimetry) of friction composites were performed. The variations in coefficient of friction (COF) and temperature with the change in sliding time were observed in detail at different additive ratios. The tribological behaviors of these composites were tested using a computer supported block‐on ring machine at sliding speeds of 200, 250, 300, and 350 rpm, applied loads of 50, 100, 150, and 200 N and constant time of 1800 s under dry conditions. Results indicated that with increase in the GF and Gr content, the stability of the (COF) became more stable and effectively reduced the specific wear rate. In addition, the wear resistance increased in parallel with the increase in normal loads and sliding speeds for all conditions.
Fabrication of novolac/graphite (Gr)/glass‐fiber (GF) friction composites. Investigate the effect of glass fiber and graphite contents on wear behavior. Obtaining advanced tribological properties with the reinforcement of Gr and GF.
In this study, the effects of ball milling (BM) technique and carbon nanotube (CNT) content on the thermal and mechanical properties of hybrid reinforced composites were investigated. The composites ...were prepared using glass fiber (GF), novolac resin (No), and CNTs with different wt% (1, 2, and, 4). Various milling times were used to optimize the entanglement/agglomeration of CNTs in the polymer matrix and subsequently enhance the final thermal and mechanical properties. Through precise investigations, it was found that the nanocomposite with 2 wt% CNT reinforcement, subjected to 2 h of BM, exhibited remarkable enhancements in key properties. The tensile strength was significantly improved to 45.6 MPa, while the elastic modulus reached 3.419 GPa. Hardness was measured at 96 HRM, and thermal conductivity was enhanced to 0.463 W/mK. Moreover, this sample demonstrated a weight loss that was 43.65% lower compared to the sample reinforced with 1 wt% CNT and subjected to 1 h of BM. Overall, this study highlights the importance of optimizing the milling time and CNT content in the preparation of polymer nanocomposites, and it provides valuable insights for the development of advanced materials with superior performance in various applications.
The production route of nanocomposites.
This study aims to examine the physical and mechanical properties of novolac matrix glass fibers (GFs) and graphite particles (GPs) reinforced hybrid composites as the function of the GFs and GPs ...content. In accordance with this purpose, the GFs content was kept constant at 20 %wt., while the GPs ratio was changed at 20 %wt., 30 %wt., and 40 %wt. On the other hand, the GPs ratio remained constant at 40 %wt., and the GFs ratio was changed between 20 %wt., 30 %wt., and 40 %wt. To obtain homogeneous hybrid composite powders, the GFs/GPs/Novolac resin powders was blended by a mechanical mixer. Then, the hybrid composite powders were placed in a steel mold and kept in the oven followed by the pressing at 20 MPa. The morphology of the matrix and additive particles used in the production of hybrid composites, the microstructures and fracture surfaces of hybrid composites were examined by scanning electron microscopy (SEM) while the crystalline phases of the materials were investigated by X-ray difftaction (XRD). The density measurements were made by the Archimed’s method. The mechanical properties of hybrid composites (hardness and tensile strength) were investigated. Thermal and flammability analyses were performed using thermogravimetric analysis (TGA) and by limited oxygen index (LOI) tests. According to the results, an increase in hardness, maximum tensile strength was determined with the increase in GFs and GPs content in hybrid composites. The hardness and maximum tensile strength obtained in pure novolac were determined as 32 HRM and 12 MPa, respectively, while those determined in hybrid composites were 98 HRM and 33.8 MPa (30 %wt. GFs and 40 %wt. GPs). When the limited oxygen index (LOI) test results were examined, 40 %wt. GPs and 40 %wt. GFs-added composites were determined to be the material with the highest non-flammability. This value shows that the flammability was improved when the required amount of oxygen increased from 37 % to >50 % compared to that of pure novolac.
In this study, effect of recycled zinc powder reinforcement ratios and ball milling time on novolac matrix hybrid composites were investigated. The ball milling time of 2 h showed a positive effect ...on the hardness of the composites up to 100 HRM. Thermal analysis results showed that the increasing zinc reinforcement ratio was increased thermal stability of the composite powders. The assessment of wear resistance was conducted using a block-on-ring tribometer, and the results demonstrated that the incorporation of zinc particles significantly decreased wear rates. Additionally, 2 h ball milling times showed superior wear resistance. Specimens with 20 wt% Zn reinforcement and subjected to 2 h ball milling time exhibited approximately 93% less wear loss than Zn-free specimens.
•Zinc powder recycled from waste Zinc anode.•Novolac matrix Zinc reinforced hybrid composites synthesized.•Thermal stability was increased with increasing Zinc reinforcement ratio.•The highest hardness value was obtained as 100 HRM.•The minimum wear rate in this study was obtained as 0.39 × 10−5 mm3/N.m.
In this study, ZA27-Al2O3-Gr hybrid nanocomposite materials (HNMs) were prepared by powder metallurgy method including mechanical-milling and hot-pressing (HP). The physical and mechanical properties ...of ZA27-Al2O3-Gr HNMs have been investigated with the primary objective of understanding the influence of the alumina (Al2O3) nanoparticle (n-Al2O3) reinforcement. The density, hardness and tensile strength tests of HNMs carried out to determine the physical and mechanical properties of ZA27-Al2O3-Gr HNMs. Scanning Electron Microscope (SEM) is used for the microstructural evolution of the HNMs. As a result of microstructure examination results, n-Al2O3 were observed around grain boundary while the graphite (Gr) nanoparticles (n-Gr) were dispersed homogeneous throughout ZA27 matrix. Relative density values decreased with the increase of nanoparticle reinforcement ratio from 1%vol to 4%vol., while an increase in porosity values was detected for HNMs. Moreover, the results showed that the addition of n-Al2O3 significantly improved the mechanical properties of the HNMs. Additionally, the HNMs reinforced with 4%vol. n-Al2O3 and 1%vol. n-Gr exhibited the highest tensile strength of about 158 MPa and hardness of 160 HB in comparison with the other HNMs reinforced with different content of n-Al2O3.
Novolac matrix composites are crucial due to their exceptional resistance to heat, chemicals, and mechanical stress. These advanced materials find applications in aerospace, electronics, and ...automotive industries, providing high-performance solutions for components requiring superior durability and reliability. In this context, the microstructure, thermal, phase, and mechanical properties of the composites obtained as a result of the recycling-oriented reinforcement of the waste candle-soot (CS) reinforcement at the rate of 1 wt% to the pure novolac (PN) and shaping with the hot press method were examined in detail at first time in the literature. While microstructural properties and fracture mechanisms were investigated by scanning electron microscopy (SEM), thermal properties were investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The results obtained provided critical findings as the composite hardness, tensile strength, and flexural strength values were 3.28, 2.47, and 3.21 times higher than PN, respectively. CS-reinforced novolac composites made a significant contribution to the literature by introducing a novel and eco-friendly approach to enhance material properties. Their use as a filler material provided insights into sustainable novolac composites, offering potential applications in various industries, such as electronics and aerospace, with improved mechanical and thermal properties.
In this study, nanosized B
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C and graphite-reinforced ZA27 matrix hybrid nanocomposites were produced with mechanical milling followed by hot pressing. The friction coefficient values of ...nanocomposite samples remarkably decreased from 0.5036 (± 0.085) to 0.2575 (± 0.021) with the increase of milling time to 24 hours for nanocomposite powders. That was almost two times lower than those of unmilled nanocomposites. It was determined that the good distribution of reinforcement particles in the microstructure and low grain size allowed the formation of a protective oxide layer against corrosion. The corrosion resistance of the nanocomposite materials obtained from nanocomposite powders milled for 24 hours was quite superior to the others. The results revealed that the corrosion rate values were 29.068 and 4.033 mpy for hybrid nanocomposite samples produced from unmilled and milled powders for 24 hours, respectively.
In this study, definitions of Weld Penetration (WP), Depth of Fusion (DOF) and Throat Thickness (TT) in fillet welds according to related standards are evaluated. Each standard makes its own ...definition related to WP, DOF and TT. Moreover, when looking at these standards, it is seen that definitions are always made in terms of unit of length. In many studies, assessment of fusion or penetration (FOP) rate on fillet welds is performed as the ratio of the maximum FOP depth to the material thickness. Depth assessment taking into consideration unit of length is not ideal for accurate evaluation of FOP rates especially on fillet welds. In the evaluation made in terms of unit of length, FOP rate can be approximately 50 percent more than the evaluation made in terms of unit of area. Method taking into consideration unit of area will be more suitable as it allows accurate assessment of FOP rates in welded joints. In this review, in addition to evaluation of the definitions of standards, it is also suggested that the evaluation of FOP rate on fillet welds should be determined in terms of unit of area rather than length.
This study extensively investigates the effects of 10 wt% graphite reinforcement and varying B4C content (1 wt%, 2 wt%, 4 wt%) on the properties of Novolac matrix polymer composites prepared by ...mechanical milling-assisted hot pressing. The microstructures, wear surfaces, wear debris, and fracture surfaces of the produced polymer composites were examined using SEM and EDS. The density measurements were conducted according to the Archimed’s principle. Their tribological behavior was evaluated with a reciprocating ball-on-flat sliding wear test at 50 N, 75 N, and 100 N loads. After the wear tests, surface topography was analyzed in 3D with an optical profilometer. The results indicated that composites with 2 wt% B4C had the lowest specific wear rate and the highest wear resistance.
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