Papers by Keyword: Alumina Fiber

Abstract: The growth of carbon nanofibers (CNFs) with ordered macroscopic structures could be achieved by CVD technique. Silica fiber, alumina fiber, and AAO membrane were selected as the typical ordered macroscopic substrates for CNFs growth. It turned out that silica fiber could act as the promising and effective substrate for CNFs growth on its surface. While alumina fiber and AAO membrane could also be expected to act as the potential substrates for CNFs growth on their surface.

Abstract: Alumina fiber products have high modulus and strength that are resistant toward the attacks of molten metals and non-oxide materials up to 1000°C. Fibers also have low thermal conductivity and high melting point. In this work, alumina fibers were synthesized by sol-gel electrospinning technique (e-spinning). The sol was prepared by mixing aluminum nitrate nonahydrate (ALN) and aluminum isopropoxide at 1:3 molar ratios. The precursor sol was stirred vigorously for 24 hours until ALP completely dissolved. After stirring, the precursor sol with PVA and without PVA was evaporating to obtain the suitable viscosity to spin. The rheology and viscosity were checked by viscometer. At the appropriate viscosity range about 0.2 to 7 Poise, the sol was then spinning into fibers using electrospinning machine. The green fibers were then dried at room temperature then calcined at 1200°C. The fibers produced were characterized using X-Ray Diffraction (XRD) and Field Emission Scanning Electron Microscope (FESEM). The XRD analysis had shown the α-alumina was formed at 1200 °C and SEM micrograph shows the formation of fibers with PVA addition.

Abstract: This paper examines the stress distribution around a fiber break in alumina-fiber reinforced aluminum matrix (Al2O3/Al) composites using finite element analysis and predicts the tensile strength using tensile failure simulations. In particular, we discuss the effect of the matrix hardening on the tensile failure of the Al2O3/Al composites. First, we clarify the differences in the stress distribution around a fiber break between an elastic-perfect plastic matrix and an elastic-plastic hardening matrix using finite element analysis. Second, the procedure for simulating fiber damage evolution in the Al2O3/Al composites is presented. The simulation incorporates the analytical solution for the axial fiber stress distribution of a broken fiber in the spring element model for the stress analysis of the whole composite. Finally, we conduct Monte Carlo simulations of fiber damage evolution to predict the tensile strength of the Al2O3/Al composites, and discuss the effect of matrix hardening on the tensile strength of the Al2O3/Al composites. Coupled with size-scaling analysis, the simulated results express the size effect on the strength of the composites, which is seen in experimental results.

Abstract: In order to develop the alumina fiber reinforcements optimized to FRMMCs, the effect of characteristics of alumina fibers on the fabrication process and the characteristics of the alumina fiber reinforced Al alloy composites was investigated. Alumina fibers which have different alumina content were prepared. Alumina content in the fibers was varied from 80% to 100%. Al-4mass%Cu alloy, Al-12mass%Si alloy and Al-10masss%Mg alloy were used as matrix. The FRMMC specimens were fabricated by a low-pressure infiltration process (LPI process). The formability of the preform was improved with increasing alumina content in the fibers. However, broken fibers were observed in the preform when alumina fibers with high alumina content were used. The number of the broken fibers seemed to be increased with increasing alumina content in the fibers. This result could be attributable to a change of fiber strength resulting from a change of alumina content in the fiber. The FRMMC specimens were characterized by using Vickers hardness test. The Vickers hardness of FRMMC specimens depended on the elasticity or the hardness of the fibers. The results obtained suggest that the characteristics of the FRMMCs largely depend on the intrinsic characteristics of the reinforcement fibers.

Abstract: Metal matrix composites (MMCs) have been used for aviation, automobile and nuclear application due to their highlight properties such as superior strength, high specific stiffness, wear, and creep resistance at elevated temperature. For developing MMCs by liquid infiltration, preform will be required. In this research paper, developed a hybrid fiber preform and investigated their microstructure properties. Graphite nano fiber (GNF) and Alumina fiber were used for fabrication of the preform. The main objective of developing a preform is i) attainment of uniform distribution of reinforcement ii) minimization of mechanical and chemical damage. Since, it is extremely difficult to disperse nano-size fibers uniformly into the preform. An attempt has been made for hybrid preform with alumina micro-fiber and graphite nano fiber. Microscopic investigations revealed good disperse of the nanofibers in the preform.

Abstract: To improve the transverse properties of fiber-reinforced metal matrix composites, a three-phase material model was proposed. In the model the reinforcing fibers are surrounded by a weak metal matrix, which in turn is encircled by another strong metal matrix. The weak matrix acts as a role to protect the fibers from damage and the strong matrix acts as a role to improve the transverse properties of the composite. Based on the material model, FEM model was established and parameter analysis was carried out to determine the influence of matrix strengths and fibers spatial distribution on the transverse mechanical behavior of the three-phase composite. It was found that the yield strength of the three-phase composite was mainly dictated by the matrix directly surrounding fibers and the effect from another matrix on the yield strength can be neglected. The three-phase composite has a higher transverse strength with hexagonal fiber arrangement than with regular square fiber arrangement.