Mechanical characteristics and deformation mechanism of boron nitride nanotube reinforced metal matrix nanocomposite bas
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Mahmoud Shariati Department of Mechanical Engineering, Faculty of Engineering, Ferdowsi University of Mashhad, Mashhad 91779-48974, Iran
Hossein Tavakoli-Anbaran Faculty of Physics, Shahrood University of Technology, Shahrood 36199-95161, Iran (Received 20 January 2018; accepted 26 March 2018)
Boron nitride nanotubes (BNNTs) have been utilized to strengthen various engineering materials especially metal matrix composites thanks to their extraordinary high tensile strength, elastic modulus, and failure strain. In this paper, single- and multi-walled BNNTs were therefore used to combine with aluminum (Al) metal matrix. Mechanical characteristics and deformation mechanism of nanocomposites reinforced with long (continuous) and short (discontinuous) BNNTs were then investigated for different loadings including uniaxial tension and compression and different boundary conditions based on molecular dynamics simulations. It was found that long BNNTs remarkably improved tensile mechanical properties of the matrix and effectively enhanced elastic modulus and strength of the nanocomposites by 82% and 79.4%, respectively. They could provide effective barriers to propagation path of dislocations formed inside the matrix. Diameter and wall number of the reinforcement did not leave considerable impacts on the nanocomposite behavior while its atomic fraction remarkably influenced the material response.
I. INTRODUCTION
It has been proved that boron nitride nanotubes (BNNTs) behave mechanically similar to carbon nanotubes (CNTs) providing exceptionally high tensile strength,1 excellent elastic modulus (.1 TPa),2–4 high failure strain,5,6 and high flexibility.5,7 Furthermore, BNNTs exhibit better thermal and oxidation stability so that they start oxidizing at higher temperature 950 °C as compared to CNTs at 500 °C,7–9 which is an important advantage in their applications in combination with metal matrix composites (MMCs). The outstanding mechanical characteristics of BNNTs make them appropriate to combine with different engineering materials especially MMCs to strengthen their mechanical behavior and therefore to obtain lighter and stronger composite materials. As reported in the literature, it has been proved that BNNTs are promising reinforcements and have successfully been used to reinforce polymeric,10–18 ceramic,19–22 glass,23 and metallic composites.8,24–27 However, there are yet a limited number of published research regarding a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2018.93
the influence of BNNT addition on the mechanical behaviors of reinforced MMCs. Al-based composites reinforced with BNNTs have been successfully synthesized using the method of spark plasma sintering by Lahiri et al.8 They achieved an improvement of more than 50% in yield strength and fracture strength of the composite with 5 vol% BNNT addition by micropillar compressive tests. Their microstructural analysis revealed the effective role of the reinforcement in load bearing and transfer through crack brid
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