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, Leon Phung1, Cyril Williams2

1

Department of Mechanical and Aerospace Engineering, California State University, Long Beach, California 90840, USA US Army Research Laboratory, Aberdeen Proving Ground, Adelphi, Maryland 21005, USA a) Address all correspondence to this author. e-mail: [email protected] 2

Received: 5 December 2018; accepted: 31 January 2019

Metal matrix composites (MMCs) have great potential to replace monolithic metals in many engineering applications due to their enhanced properties, such as higher strength and stiffness, higher operating temperature, and better wear resistance. Despite their attractive mechanical properties, the application of MMCs has been limited primarily due to their high cost and relative low fracture toughness and reliability. Microstructure determines material fracture toughness through activation of different failure mechanisms. In this paper, a 3D multiscale modeling technique is introduced to resolve different failure mechanisms in MMCs. This approach includes 3D microstructure generation, meshing, and cohesive finite element method based failure analysis. Calculations carried out here concern Al/SiC MMCs and focus on primary fracture mechanisms which are correlated with microstructure characteristics, constituent properties, and deformation behaviors. Simulation results indicate that interface debonding not only creates tortuous crack paths via crack deflection and coalescence of microcracks but also leads to more pronounced plastic deformation, which largely contributes to the toughening of composite materials. Promotion of interface debonding through microstructure design can effectively improve the fracture toughness of MMCs.

Introduction Metal matrix composites (MMCs) exhibit excellent material properties such as higher specific strength, operating temperature, and wear resistance than monolithic metals. These properties make MMCs attractive for many structural applications. To facilitate successful application of MMCs, an in-depth understanding of the microstructure–property relationship is required. It has been reported that microstructure and constituent properties combine to determine the overall fracture toughness of MMCs through the activation of different fracture mechanisms [1, 2, 3]. Specifically, interface debonding and particle cracking are two competing fracture mechanisms during the crack–reinforcement interactions [4]. Qian et al. [5] experimentally evaluated the fracture toughness of 6061 Al MMCs and concluded that MMCs with large reinforcement particles exhibit lower initiation fracture toughness, crack propagation energy, and total absorbed energy. Jarzabek et al. [6] further observed that large particles correspond to higher interface strength which discourages interface debonding and

ª Materials Research Society 2019

negatively influence the fracture toughness of MMCs. Alaneme and Aluko [7] reported that interface debonding is a beneficial failure mechanism which can lead to improved fracture toughness of MMCs. This is because the propagation of i