Domain Reorientation as a Damping Mechanism in Ferroelastic-Reinforced Metal Matrix Composites
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INTRODUCTION
STRUCTURAL metals are typically selected based on high stiffness and strength. However, stiff materials are notoriously efficient in transmitting vibrations, which represent an unwanted side effect of mechanical motion since they can lead to mechanical failure via high cycle fatigue, induce physical discomfort, or compromise stealth. In practice, mechanical vibration attenuation is often extrinsically achieved by the use of active or passive-external dampers that potentially add weight and cost to the structure. Alternatively, there are other strategies that focus on microstructural solutions, for example, by incorporating secondary phases within a metallic matrix to provide benefits attributable to interfacial-based attenuation while also simultaneously improving strength and stiffness.[1] While some benefit was realized through dissipative mechanisms associated with the creation of the associated interfaces and the introduction or modification of certain microstructural defects, traditional composite-based approaches were generally only marginally successful since typical loadsharing metal matrix composite (MMC) reinforcements (such as SiC and Al2O3) have very low inherent damping characteristics in bulk form and this can serve to counteract the benefits otherwise attained. Under certain conditions, the use of functionally-active composite B.D. POQUETTE, Advanced Manufacturing Engineer, is with GE Healthcare, Milwaukee, WI 53219. T.A. ASARE, Product Engineer, is with Special Metals Corporation, New Hartford, NY 13413. J.P. SCHULTZ, Chief Technology Officer, is with Schultz-Creehan Holdings, Inc., Blacksburg, VA 24060. D.W. BROWN, Technical Staff Member, is with Los Alamos National Laboratory, LANSCE-12, Los Alamos, NM 87545. S.L. KAMPE, Professor, is with the Department of Materials Science & Engineering, Michigan Tech, Houghton, MI 49931. Contact e-mail: [email protected] Manuscript submitted September 8, 2010. Article published online April 13, 2011 METALLURGICAL AND MATERIALS TRANSACTIONS A
reinforcements, such as shape memory alloys,[2] magnetostrictive,[3,4] and ferroelectric[4–8] ceramics conceivably could offer the potential to provide both damping and strengthening if appropriately engineered and incorporated within the microstructure. In this work, we focused on ferroelectric ceramics as high damping secondary reinforcement phases in metallic matrices. Depending on the electrical state of a ferroelectric ceramic reinforcement, there are two distinct, conceivable mechanisms that could contribute to the overall damping of a metal-ferroelectric ceramic composite system. For the first, a poled, isolated ferroelectric reinforcement may be capable of mechanical vibration suppression through the conversion of mechanical strain to electrical energy if subsequently converted to resistive heat that is dissipated through the volume of the adjacent metallic matrix.[5–8] This mechanism was experimentally demonstrated in polymer matrix composites consisting of piezoelectric ceramic and carbon black dispersions.[5] Here, the
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