Experimental investigation of the thermal properties of tailored expansion lattices
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Experimental investigation of the thermal properties of tailored expansion lattices Craig A. Steeves Æ Chris Mercer Æ Emilio Antinucci Æ Ming Y. He Æ Anthony G. Evans
Received: 25 June 2008 / Accepted: 12 February 2009 / Published online: 17 March 2009 Ó The Author(s) 2009. This article is published with open access at Springerlink.com
Abstract Composite bimaterial lattice structures which possess both low, tailorable thermal expansion and nearly optimal stiffness have been proposed for applications which require high structural stiffness in environments which include large temperature fluctuations, such as the surfaces of high-speed aerospace vehicles. An experimental validation of the thermal properties of these lattices when they are constructed of practical materials with easily manufactured bonded joints is contained herein. Bonded lattices, comprising aluminum and titanium alloys, have been manufactured with press-fit dovetail joints and tested in a variety of thermal environments. Results for equilibrium heating, rapid transient heating and thermal cycling leading to shakedown are presented and shown to be consistent with theoretically and numerically attained results. Keywords Low thermal expansion Composite structures Experimental testing
C. A. Steeves (&) C. Mercer E. Antinucci M. Y. He A. G. Evans Materials Department, University of California, Santa Barbara, Santa Barbara, CA 93106, USA e-mail: [email protected] C. Mercer National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan
1 Introduction In structural systems that experience large temperature changes and thermal gradients, the associated strains are a significant impediment to successful design and implementation. The large thermal strains result in excessive geometric changes and substantial thermal stresses when high-temperature components are connected to lower temperature structures with smaller thermal strains. The consequences include failure by yielding, fracture or fatigue, as well as the formation of gaps that require sealing and extreme forces on attachments to other structures. Multimaterial lattices have been proposed as a solution to these issues. By combining two or more materials with empty space, composite lattice structures can be manufactured to have a thermal expansion coefficient which is tailored to the application (and which can be zero or even negative). Lakes (1996), Sigmund and Torquato (1996), Gibiansky and Torquato (1997), and Jefferson (2006) have all proposed lattice structures with these properties. However, the Lakes and Jefferson lattices are both bending-dominated structures (see Deshpande et al. 2001) and are consequently very compliant, while the structures proposed by Torquato and his collaborators are biaxially (but not uniaxially) stiff but very difficult to manufacture. More recently, Grima et al. (2007) demonstrate a lattice material which is stiff but has highly anisotropic thermal properties.
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