Stress and strain localization three-dimensional modeling for particle-reinforced metal matrix composites
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I. INTRODUCTION
PARTICLE-REINFORCED metal matrix composites (PR MMCs) combine a ductile metal matrix (e.g., aluminum) with brittle ceramic particulate reinforcement (e.g., silicon carbide, alumina). Their advantages include specific stiffness, specific strength, wear resistance, and thermal tailorability, while their applications include the automotive, aerospace, electronics packaging, and sporting goods markets.[1] Compared to fiberreinforced composites, PR MMCs have low raw material and processing costs. However, low ductility relative to metal alloys limits their application in strength driven or toughness critical applications. Hence, improvement of the ductility of PR MMCs has become a research focus over recent years. Although many factors such as particle shape and aspect ratio influence ductility, the particle distribution, specifically particle clustering, plays a key role in damage mechanisms.[2] Since the local volume fraction inside clusters is high, clusters are stiffer than the rest of the material and they bear more load during deformation. Thus, it is not surprising to find that the clusters are preferential sites for damage initiation. Flom and Arsenault[3] observed that damage initiates in clusters, and then spreads between clusters, eventually resulting in final failure. However, Clyne and Withers[4] point out that if a cluster behaved as a single particle, it might reduce the possibility of damage initiation in that cluster. Yip and Wang[5] predicted H. SHEN, Postdoctoral Student, formerly with the Department of Engineering Science and Mechanics, Pennsylvania State University, University Park, PA 16802, is with Dept. of Mechanical Engng, Northwestern University, Evanston, IL 60208. C.J. LISSENDEN, Associate Professor, is with the Department of Engineering Science and Mechanics, Pennsylvania State University. Contact e-mail: [email protected] This article is based on a presentation made in the symposium entitled “Three Dimensional Materials Science” during the 2003 MS&T ‘03: Materials Science & Technology Conference 2003 in Chicago, Illinois, on November 11–12, 2003, under the auspices of the ASM/MSCTS: Materials Science Critical Technology Sector Committee and the TMS/SMD: Structural Materials Division Committee. METALLURGICAL AND MATERIALS TRANSACTIONS A
that a four-particle cluster with appropriate interparticle spacing may induce a hydrostatic stress state in the cluster that could suppress the onset of yielding until a much higher load is applied. The interparticle spacing is the key to elevating the hydrostatic stress and only when it is less than a threshold value is there such an effect. Zhou et al.[6] found that an aluminum matrix composite reinforced with spherical particle clusters has higher elastic modulus, ultimate strength, and ductility than if the particles are randomly distributed. These contradicting reports indicate that the particle distribution requires further investigation. Damage of PR MMCs is controlled by the local stress and strain fields, which are affected by many
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