Analysis of a ceramic/metal laminate under thermal shock
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A ceramic/metal laminated system has lately been proposed by the authors. It is capable of maintaining high mechanical strength and structural integrity after high-temperature thermal shock. In this investigation, a multilayered, multimaterial system with strong interface, subjected to thermal shock loading, was analyzed. The analysis was based on a 1-D finite difference scheme and considers the thermal residual stresses. Using a failure criterion based on crack initiation, the number of broken layers due to thermal shock and the residual mechanical strength at room temperature was determined. A comparison with experimental results of three different lay-ups was made, demonstrating the ability of the program to predict the experimental results. The program was thus shown to be a significant tool for designing multimaterial multilayered systems for thermal shock applications.
I. INTRODUCTION
The need for high-performance structures such as jet engines, space shuttles, rockets, etc., is associated with a demand for materials that can operate at high temperatures and in harsh environments, for which ceramics are excellent candidates.1–4 In many respects, the behavior of engineering components made from advanced ceramics is superior to that of their metallic counterparts. In addition to their high melting point and good corrosion, fatigue, and wear resistances, ceramics may be used in extreme operating conditions such as cyclic thermomechanical loadings, etc. It is widely recognized that resistance to thermal shock, resulting from either rapid cooling or rapid heating, is an important property required from materials operating at high temperatures in order to eliminate catastrophic failure.1 It is therefore an immense challenge to develop such a material and a ceramic material in particular. While some ceramics and glasses offer only limited resistance to thermal shock, others such as Si3N4 and AlN are known for their superior thermal shock resistance.4–6 This property is associated with the high toughness of the materials, good thermal conductivity, and low thermal expansion coefficient and Young’s modulus. Ceramic/ceramic laminated systems have shown increased fracture energy due to crack deflection and renucleation mechanisms.4–6 Metal/ceramic laminates have been examined for enhanced fracture energy due to the plastic deformation of the metallic layers.10–12 The use of high toughness ceramics for thermal shock application has been suggested, and the candidate materials J. Mater. Res., Vol. 16, No. 3, Mar 2001
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are fiber-reinforced ceramics matrix composites.10–12 The integrity of such a system after thermal shock cycles is, however, questionable. A laminated system consisting of thin alumina layers alternating with thinner metallic interlayers has lately been investigated by the authors. The aim was to increase the thermal shock temperature while maintaining significant mechanical strength.15 The basic features of this architecture were as follows: (i) absen
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