Analysis of thermoelastic damping in laminated composite micromechanical beam resonators

Minimization of structural damping is an essential requirement in the design of multifunctional composite micromachined resonators used for sensing and communications applications. Here, we study thermoelastic damping in symmetric, three-layered, laminated, micromechanical Euler-Bernoulli beams using an analytical framework developed by Bishop and Kinra in 1997. The frequency dependence of damping in two representative sets of structures-metallized ceramic beams and ceramic/ceramic laminates-is investigated in detail. The effects of material properties and relative volume fractions are numerically evaluated. The results indicate that metallization of Si and SiC beams using Al, Cu, Ag or Au leads to a considerable increase in damping over a broad frequency range. Similarly, coating silicon with SiC leads to a monotonic increase of the peak damping value as a function of the volume fraction of silicon carbide but, remarkably, there exists a range of frequencies at which the damping in the composite is less than that of bare silicon. Implications for the design of metallized ceramic beams, and for the simultaneous optimization of natural frequency and damping, are discussed.