Fabrication of Functionally Graded Carbon Nanotube‐Reinforced Aluminum Matrix Composite

Abstract

Functionally graded materials (FGMs) are compositionally gradient materials which were first proposed in Japan in 1984. [1] They have been suggested as a way of fabricating bulk materials with tailored properties because they can achieve the controlled distribution of the desired characteristics within the same bulk material. This FGM can be applied for engineering parts instead of coated materials. However, careful selection of the component materials, particularly the reinforcement, is required to reliably achieve a high performance from the FGM. Carbon nanotubes (CNTs), which have a unique combination of excellent mechanical, electrical, and thermal properties, have become a hot property in the engineering materials field, since their discovery in Japan in 1991. [2,3] For this reason, CNT is a satisfactory candidate to be a reinforcement material for fabricating high quality FGMs.Extensive research on the fabrication and characterization of CNT-reinforced polymer, [4,5] ceramic, [6,7] and metal matrix [8,9] composites has been carried out but CNT gradient layer-reinforced FGMs have rarely been investigated. Recently, Estili et al. have reported that the CNT gradient layer in ceramic matrix composite materials fabricated by the spark plasma sintering process shows similar hardness results to the ceramic matrix. [10] Ke et al. studied the nonlinear free vibration of functionally graded CNT nanocomposite based on numerical results. [11] Shen and Zhang have reported the mechanical behavior of functionally graded CNT-reinforced composites in thermal environments by a micromechanical model. [12,13] Indeed, most investigations regarding functionally graded CNT-reinforced composite materials were based on numerical calculations or models.In the present study, we attempted to fabricate functionally graded CNT-reinforced metal matrix composite bulk materials by a powder metallurgy route and to then characterize these composites. Aluminum (Al) was utilized for the matrix material because its high specific strength and high ductility [14] combined with the CNT offers high performance of structural materials. In particular, extremely different characteristics in the same Al-CNT bulk materials (e.g., highly strengthened surfaces and highly enhanced ductility inside) can be achieved by the FGM concept. The various Al-CNT composite powders were prepared by a planetary ball milling process and then hot pressed in a layered structure. The FGM bulk obtained was analyzed, with a focus on the hardness of each CNT gradient layer. Moreover, microstructural observations, phase analyses, and density measurements were carried out, to develop a better understanding of the hardness behavior in the FGM bulk. ExperimentalMultiwalled CNTs (Baytubes C150P, Bayer material science, purity 99.5%, diameter: 20 nm, length: 30 mm) and gas-atomized pure Al powder (ECKA Granules, purity 99.5%, mean particle size: 63 mm) were used as the starting materials. Homogeneously well dispersed CNT-Al composite powders containing 5, 10, and 15 vol% CNT were p...

Nonlinear bending of nanotube-reinforced composite cylindrical panels resting on elastic foundations in thermal environments

“…To avoid abrupt change of the material properties in the functionally graded CNTRCs, a linear variation of the volume fraction of CNTs in the thickness direction is assumed and can readily be achieved in practice [9]. As the same in [35], three types of FG-CNTRCs, i.e.…”

“…He used a linear distribution pattern of CNTs along the thickness direction of the plates and found that the functionally graded CNT reinforcements can significantly change the bending behavior of the CNTRC plates. The concept of functionally graded nanocomposites has been realized in a recent experimental study [9] where a functionally graded CNT reinforced aluminum composite was fabricated using a powder metallurgy route. These pioneer works have stimulated extensive studies on the bending, buckling and vibration responses of CNTRC structures in recent years [10][11][12][13][14][15][16][17][18][19][20][21][22][23].…”

On functionally graded Timoshenko nonisothermal nanobeams

“…Another frequent manufacturing process of FG nanocomposites uses assembling of different layers of materials. For example, aluminium -CNT composite is produced from layers containing different fractions of CNT [17]. In this particular case, Vickers hardness of each particular layer was measured with results varying by a factor of 7.…”

Free vibration of functionally graded carbon nanotube-reinforced conical panels integrated with piezoelectric layers subjected to elastically restrained boundary conditions

“…7 Numerical results of Shen reveal that nonlinear bending behavior can be considerably improved using an FG distribution of CNTs in the matrix. Recently, Kwon et al 8 have successfully achieved the linear distribution of CNTs in a matrix, rather than the uniform distribution of CNTs in a matrix using the power metallurgy fabrication process, which proves the feasibility of FG-CNTRC.…”