PSI - Issue 27

Hammar Ilham Akbar et al. / Procedia Structural Integrity 27 (2020) 30–37 Akbar et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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material density (Zahi and Daud, 2011). Fly ash particles are generally spherical-shape with specific gravity 0.6-2.8 gm/cc (Bharathi et al., 2017). The fly ash chemical composition consists of SiO 2 , Al 2 O 3 , Fe 2 O 3, and oxides such as Mg, Ca, and P, including crystalline phases of quartz mullite and hematite in small amounts (Fan and Juang, 2016). The chemical composition of fly ash is shown in Table 1. Generally, fly ash is classified in ASTM C618, namely Class C and Class F. Class F is fly ash obtained from burning anthracite or bituminous coal, while Class C is the result of burning sub-bituminous or lignite coal. (Nizar et al., 2014). Table 1. Chemical composition of fly ash (Nizar et al., 2014) . Element SiO 2 Al 2 O 3 Fe 2 O 3 TiO 2 CaO Na 2 O K 2 O P 2 O 5 SO 3 MnO Content % 52.11 23.59 7.39 0.88 2.61 0.78 0.42 0.80 1.31 0.49 Investigations about composites with coal ash reinforcement (fly ash and bottom ash) have been carried out (Bharathi et al., 2017) using the stir-squeeze casting method LM 25-7% Si with the addition of 2.5 and 5% wt fly ash. Fly ash particles are given a pre-heat treatment before being mixed in the liquid metal. The wear resistance of MMC increases with the addition of fly ash. This increase occurs due to the hardness, stiffness, and strength of the fly ash reinforcing particles. However, the wear rate increases with increasing load and speed; this is because the bond between the reinforcing particle and the matrix breaks and also increases the friction on the contact surface. Material hardness increased from 62 HV at 0 vol% to 125 HV at 18 vol% fly ash particles by the friction stir processing method. Fly ash particles are distributed evenly so that it gives a reinforcement effect. The distribution of fly ash also inhibits dislocation, thereby increasing the mechanical properties of composites. Increased hardness is inversely proportional to the rate of wear. Wear rates drop from 411 x 10 -5 mm 3 /m at 0 vol% to 203 x 10 -5 mm 3 /m at 18 vol%. Archard's Law explains the hardness-wear rate relationship of a metallic material; the higher the hardness will decrease the wear rate because AMC's sliding wear resistance increases (Dinaharan et al., 2016). The effect of adding fly ash to aluminum composites has been studied (Fan and Juang, 2016). Before being used as an aluminum composite reinforcement, fly ash was uniformly sized between 53-106 µm. Then the fly ash is pre heated at 800ºC. Fly ash is added 5% wt to the Al-3Mg matrix and reheated after being cool for 0, 10, 20, 30, and 40 hours. The addition of fly ash increased composite hardness from 48.21 BHN to 54.96 BHN. The highest hardness is obtained when the composite is reheated for 40 hours. The decomposition reaction of non-solid fly ash particles decreases the porosity of composites. Besides that, the in situ process produces a better bond between the matrix and the reinforcement. An evaluation of the impact properties of Al-4046 hybrid composites with fly ash and S-Glass speakers was studied (Mallikarjuna et al., 2017). Hybrid composite manufacturing was successfully carried out with the stir casting method with good particle distribution results. Impact strength increases up to 6% wt fly ash addition. The impact strength increase is due to dislocation inhibition obtained by the addition of S-Glass. Differences also influence dislocation at the interface boundary in the heat coefficient between the matrix and the reinforcement. The gap in the matrix results in the plastic deformation of the matrix, which causes dislocation (Rao et al., 2020). The addition of other reinforcement such as Rice Husk Ash (RHA) to hybrid Al-Fly ash composites has also been studied (Narasaraju and Raju, 2015). The addition of reinforcement up to 20%wt improves the mechanical properties of hybrid composites. The highest tensile strength is obtained when fly ash and RHA are added as much as 10% wt. Composite hardness also increases when the variation of the reinforcement composition is 10% wt, then decreases when the RHA is increased to 15% wt. Increased tensile strength and hardness due to the addition of RHA make dislocation hampered when the load is given to the specimen, increased hardness due to increased surface area, and softening grain size. Fabrication and characterization of Al-SiC-Fly ash hybrid composites were found that increasing the amount of reinforcement would increase the value of UTS, hardness, and decrease in wear (Reddy and Srinivas, 2018). Increased UTS and hardness caused by dislocation inhibited by fly ash and SiC reinforcement particles. This decrease in power is due to the distributed reinforcing particles having a higher hardness than the matrix. Also, bottom ash can is used as reinforcement for metal matrix composites. The effect of bottom ash particle treatment on composites for propeller applications has been studied before (Prastio et al., 2017). Increasing the percentage of magnesium and oxidation temperature in the electroless coating reinforcement process decreases the composite density and increases porosity. The highest density is obtained when the oxidation temperature is at 300ºC, with a weight fraction of 0.005% Mg.