Part B: engineering ELSEVIER Composites: Part B 37(2006)530-541 Structure, nonlinear stress-strain state and strength of ceramic lltilayered O.N. Grigoriev a, *, A V. Karoteev ,E.N. Maiboroda I.L. Berezhinsky ,B K. Serdega DYu. ostrovo.vg. piskunoy Institute for Problems of Materials Science, NAS of Ukraine, 3 Krghizhanovskii Str, 03142 Kiev, Ukraine Institute of Physics of Semiconductors, NAS of Ukraine, Kiev, Ukraine Institute for Problems of Strength, NAS of Ukraine, Kiev, Ukraine d National University of Transport, Kiev, Ukraine Received 4 April 2005: received in revised form 7 September 2005: accepted 15 September 2005 Available online 27 April 2006 Abstract The effect of structure and residual stresses on the mechanical behavior of the SiC/TiB, multilayer composite ceramic materials was studied. The multilayered ceramics were obtained using the following scheme: a slip casting of thin films followed by a packet rolling and hot pressing. The use of B-SiC powders allowed to obtain Sic layers with porous structure reinforced by crystals. Such structures possess the relaxation ability of thermal strains that excludes formation of cracks during material production and provides enhanced strength of the SiC/TiB2 composite. Mechanical response of the laminated ceramic composites to static bending was studied experimentally. a procedure for solving the inverse problem using experimental data on the deformation of a laminated ceramic composite specimen in the form of a beam was developed. This approach allows the mechanical characteristics of the laminates to be predicted. The nonlinear stress-strain dependencies for the laminate as a quasi-homogeneous structure and for each of the two separate materials of the layers were obtained. The modeling of the stress-strain state of t aminate was performed. c 2006 Elsevier ltd. all rights reserved Keywords: A. Layered structures; A Laminates; B Residual/intemal stress; B Strength 1. Introduction zirconium borides to silicon carbide allows increasing strength for and fracture toughness by 50-100%.However, corrosion Laminated ceramic composites offer the best prospect for resistance of these ceramics decreases significantly which is rational use of the unique physical-mechanical properties of undesirable for the majority of high-temperature applications monolithic ceramics and ceramic-matrix composites providing Therefore, a design of the multilayer composites with a way to improve their durability, fracture toughness, corrosion external layers of corrosion resistive SiC and internal layers of and thermal resistance, wear, etc. [1-7 improved mechanical performance such as SiC/MeB2 may b Silicon carbide is one of the most promising ceramic promising. Moreover, in this type of material the external Sic materials for structural applications because of its unique layers are under thermal compression stresses due to their thermomechanical properties and high corrosion resistance. lower coefficient of thermal expansion compared with internal However, low fracture toughness and reliability of silicon SiC/MeB, layers. This will also increase apparent fracture carbide significantly limit its potential applications. The toughness as well as strength and reliability of laminates. The improvement of mechanical properties is possible under the studies over the last few years have shown that the increase in careful control of structure and is due to transition from strength and/or fracture toughness of multilayer ceramic monolithic ceramics to composites. In particular, it is well composites may provide increased tolerance against damages known [8-10) that the additions of 15-30% titanium and However, the production of such composites requires a solution to layer bonding problems. Also there is the possibility of generating new defects in the thermal stresses fields [11] E-mail address: oleggrig@ipms keiv. ua(O N. Grigoriev ) Therefore, optimization of both composite manufacturing 1359-8368/- see front matter o 2006 Elsevier Ltd. All rights reserved. conditions and its structure are very important to ensure elastic doi: 10.1016/j- composites. 2006.02.009 strain relaxation. The development and design of theseStructure, nonlinear stress–strain state and strength of ceramic multilayered composites O.N. Grigoriev a,*, A.V. Karoteev a , E.N. Maiboroda a , I.L. Berezhinsky a , B.K. Serdega b , D.Yu. Ostrovoi c , V.G. Piskunov d a Institute for Problems of Materials Science, NAS of Ukraine, 3 Krzhizhanovskii Str., 03142 Kiev, Ukraine b Institute of Physics of Semiconductors, NAS of Ukraine, Kiev, Ukraine c Institute for Problems of Strength, NAS of Ukraine, Kiev, Ukraine d National University of Transport, Kiev, Ukraine Received 4 April 2005; received in revised form 7 September 2005; accepted 15 September 2005 Available online 27 April 2006 Abstract The effect of structure and residual stresses on the mechanical behavior of the SiC/TiB2 multilayer composite ceramic materials was studied. The multilayered ceramics were obtained using the following scheme: a slip casting of thin films followed by a packet rolling and hot pressing. The use of b-SiC powders allowed to obtain SiC layers with porous structure reinforced by prismatic crystals. Such structures possess the relaxation ability of thermal strains that excludes formation of cracks during material production and provides enhanced strength of the SiC/TiB2 composite. Mechanical response of the laminated ceramic composites to static bending was studied experimentally. A procedure for solving the inverse problem using experimental data on the deformation of a laminated ceramic composite specimen in the form of a beam was developed. This approach allows the mechanical characteristics of the laminates to be predicted. The nonlinear stress–strain dependencies for the laminate as a quasi-homogeneous structure and for each of the two separate materials of the layers were obtained. The modeling of the stress–strain state of the laminate was performed. q 2006 Elsevier Ltd. All rights reserved. Keywords: A. Layered structures; A. Laminates; B. Residual/internal stress; B. Strength 1. Introduction Laminated ceramic composites offer the best prospect for rational use of the unique physical–mechanical properties of monolithic ceramics and ceramic-matrix composites providing a way to improve their durability, fracture toughness, corrosion and thermal resistance, wear, etc. [1–7]. Silicon carbide is one of the most promising ceramic materials for structural applications because of its unique thermomechanical properties and high corrosion resistance. However, low fracture toughness and reliability of silicon carbide significantly limit its potential applications. The improvement of mechanical properties is possible under the careful control of structure and is due to transition from monolithic ceramics to composites. In particular, it is well known [8–10] that the additions of 15–30% titanium and zirconium borides to silicon carbide allows increasing strength and fracture toughness by 50–100%. However, corrosion resistance of these ceramics decreases significantly which is undesirable for the majority of high-temperature applications. Therefore, a design of the multilayer composites with external layers of corrosion resistive SiC and internal layers of improved mechanical performance such as SiC/MeB2 may be promising. Moreover, in this type of material the external SiC layers are under thermal compression stresses due to their lower coefficient of thermal expansion compared with internal SiC/MeB2 layers. This will also increase apparent fracture toughness as well as strength and reliability of laminates. The studies over the last few years have shown that the increase in strength and/or fracture toughness of multilayer ceramic composites may provide increased tolerance against damages. However, the production of such composites requires a solution to layer bonding problems. Also there is the possibility of generating new defects in the thermal stresses fields [11]. Therefore, optimization of both composite manufacturing conditions and its structure are very important to ensure elastic strain relaxation. The development and design of these Composites: Part B 37 (2006) 530–541 www.elsevier.com/locate/compositesb 1359-8368/$ - see front matter q 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.compositesb.2006.02.009 * Corresponding author. E-mail address: oleggrig@ipms.keiv.ua (O.N. Grigoriev)