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In the present study, aluminum alloy (Al/3.25Cu/8.5Si) composites reinforced with fly ash particles was fabricated using stir casting technique. Fly ash particles of three different size ranges 53–75, 75–103 and 103–125$\mu$m of 3, 6 and 9 weight percentages was reinforced in aluminum alloy. The effect of peak current, pulse on time, and pulse off time on surface roughness (SR), material removal rate (MRR) and tool wear rate (TWR) of electric discharge machining (EDM) was investigated. A central composite design using response surface methodology (RSM) was selected for conducting experiments, and mathematical models were developed using Design Expert V7.0.0 software. Analysis of variance (ANOVA) technique was used to check the significance of the models developed. Peak current was the major factor influencing the EDM of aluminum fly ash composites. The MRR, TWR, and SR of aluminum fly ash composites were also influenced by the size of the fly ash particles.

In this paper, a comparative experimental analysis of die-sinking electric discharge machining (EDM) to two most exhaustively used aluminum metal matrix composites (AMMCs) has been performed using Copper and Tungsten as tool electrodes. AMMCs containing silicon carbide (SiC) and alumina (Al₂O${}_3)$ as reinforcement (10wt%) were fabricated by stir casting method. The Box–Behnken Design (BBD) approach of response surface methodology was used to develop experimental models for material removal rate (MRR) and surface roughness (SR). Effect of input parameters such as current ($I=4$–12A), gap voltage ($V_g=40-60$V), pulse-on time ($T_{\mathrm{\text{on}}}=100-200\mu$s), and duty factor ($\tau =4$–6) on the output responses has been investigated with response surface plots. Effectiveness of design of experiment (DoE) and evolutionary algorithm-based multi-objective optimization (MOO) technique have been compared to find the best feasible optimal solution. ANOVA analysis reveals that for alumina reinforced AMMC interaction between $I\times V$ has significant effect on both MRR and SR using Cu electrode. But for tungsten, electrode interaction between $I\times T_{\mathrm{\text{on}}}$, $I\times \tau$, and $V\times \tau$ have major role on MRR whereas SR is mostly influenced by interaction between $I\times V_g$ and $I\times T_{\mathrm{\text{on}}}$. The parametric analysis reveals that an increase of current from 4A to 12A at a higher pulse-ontime increases the MRR more significantly, and higher MRR occurs in cases of alumina-reinforced AMMC. Increase of pulse-ontime at low current (4A) reduces the MRR in AMMC/Al₂O₃. Good surface finish can be obtained by combining high voltage (60V) with either small current (4A) or small duty factor (4) for both AMMCs. Both DoE and metaheuristic-based MOO technique reveals that copper electrode should be preferred for die-sinking EDM of AMMC/SiC. Metaheuristic approach should be preferred for optimization of die-sinking EDM of AMMCs using different electrodes because it requires low current for effective machining of different AMMCs.

Composites were prepared with carbon fiber used as the reinforcement. The influence of carbon fiber content and coupling agents on the mechanical properties of the fluorine rubber was studied. Infrared Spectroscopy (IR) showed that C-Si-O bonds were generated in the composites. These improved the compatibility between carbon fiber and fluorine rubber. Scanning Electron Microscopy (SEM) showed that the carbon fiber, treated with KH550, was aligned within the rubber with no obvious sections or pores, indicating a good interphase combination between them. Optimal mechanical properties of the composites were obtained when fluorine rubber had 12 parts per hundred rubber (phr) of chopped carbon fiber.

In this paper, the polyaniline (PANI) and PANI-Co_0.5Zn_0.5La_0.1Fe_1.9O₄ (x wt %, x = 10 and 20) composites were synthesized by an in situ polymerization. X-ray diffraction (XRD), scanning electron microscope (SEM) and ultraviolet-visible spectrometer (UV-vis) were used to characterize the morphologies and phase formation of the prepared products. The dielectric loss (tan ε) and the magnetic loss (tan μ) of the samples were measured in Xband (8.2-12.4 GHz) by using vector network analyzer (HB8510B). The results demonstrated that the dielectric loss of PANI-Co_0.5Zn_0.5La_0.1Fe_1.9O₄ were lower than that of the pure PANI and vice versa for magnetic loss. Furthermore, the dielectric loss and magnetic loss of the composites decreased and increased respectively, when the relative content of Co_0.5Zn_0.5La_0.1Fe_1.9O₄ increased. In the measuring frequency range of 8.2∼12.4 GHz, the reflection loss of composites increased with an increase in Co_0.5Zn_0.5La_0.1Fe_1.9O₄ relative content. PANI-Co_0.5Zn_0.5La_0.1Fe_1.9O₄ (20 wt %) composite has the highest reflection loss in the range of -8.73 dB to -12.75 dB, with a maximum reflection loss value at -12.75 dB at the frequency of 11.0 GHz (full frequency width at about half of the peak response).

In the measuring frequency range of 8.2~12.4 GHz, with the increase of Co_0.5Zn_0.5La_0.1Fe_1.9O₄ relative content, the reflection loss of composites increased, and the PANI-Co_0.5Zn_0.5La_0.1Fe_1.9O₄ (20 wt%) composite has the highest reflection loss, which is in the range of -8.73 dB to -12.75 dB, and the maximum values of the reflection loss is -12.75 dB at the frequency of 11.0 GHz. (full frequency width at about a half of the peak response).