The mechanical properties of ceramics

In this chapter we examine the mechanical properties of ceramics and, particularly, what is meant by their strength . 

Most ceramics are intrinsically hard ionic or covalent bonds present an enormous lattice resistance to the motion of a dislocation. Take the covalent bond first. The covalent bond is localised the electrons which form the bond are concentrated in the region between the bonded atoms they behave like little elastic struts joining the atoms (Eig. 17.1b). When a dislocation moves through the structure it must break and reform 

Nickel 9x10 Stainless steel 6x10-2 Zirconia 6x10-2 

Iron 9x10 Low alloy steel 1.5 X 10-2 Silicon carbide 6x10-2 

metals 1 X 10- Mean, alloys 1 X 10-2 Mean, ceramics 8x10-2 

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The mechanical properties of ceramics maybe increased by minimising impurity segregation, decreasing grain size and increasing sintered density. 

Rigby, G.R., The effect of expansion mismatch on the mechanical properties of ceramic materials , Trans. Indian. Ceram. Soc., 1972 31(1) 18-30. 

Residual stress resulting from the thermal expansion mismatch between the fiber and matrix is another factor which will affect the interfacial properties, matrix cracking stress and the mechanical properties of ceramic... 

In Chapter 12 of this book, the mechanical properties of ceramic suspensions, pastes, and diy ceramic powders are discussed. Ceramic suspension rheology is dependent on the viscosity of the solvent with polymeric additives, particle volume fraction, particle size distribution, particle morphology, and interparticle interaction energy. The interparticle forces play a veiy important role in determining the colloidal stability of the suspension. If a suspension... 

R. C. Bradt, Introduction to the Mechanical Properties of Ceramics, Class Notes, The Pennsylvania State University, 1980. 

This book is a comprehensive introduction to the mechanical properties of ceramics, and is designed primarily as a textbook for undergraduate and graduate students in materials science and engineering. 

FIGURE 16.3 Factors affecting the mechanical properties of ceramics. 

We would also like to know these parameters as a function of temperature, in particular, over the temperature range at which our ceramic component is going to be used. Many different types of tests are used to obtain the mechanical properties of ceramics. There are major differences between how metals are tested compared to ceramics ... 

Flaws dominate the mechanical properties of ceramics. They determine how we test them and how we design components from them. Flaws are also the reason why ceramics are stronger in compression than tension. In this chapter we described the methods used to measure mechanical properties of ceramics. The important ones are bend testing, compression testing, and indentation. To determine the mechanical properties of small volumes we use nanoindentation. This technique is especially important for thin hlms, surfaces, and nanomaterials. An understanding of statistics is particularly important when using ceramics in load-bearing applications. The Weibull approach is the one most widely used for ceramics. 

Although we often think of the mechanical properties of ceramics entirely in terms of their brittleness, in this chapter we showed that plastic deformation is also important. The main difference between plasticity in ceramics and in metals is that for ceramics the primary mechanism... 

Davidge, R.W. (1979) Mechanical Behaviour of Ceramics, Cambridge University Press, Cambridge, UK. Green, D.J. (1998) An Introduction to the Mechanical Properties of Ceramics, Cambridge University Press,... 

Rico, A., Garrido, M. A., Otero, E. Rodriguez, J. Roughness Effect on the Mechanical Properties of Ceramic Materials Measured from Nanoindentation Tests. Key Engineering Materials 333, 247-250 (2007). 

Despite the use of identical specimens, the mechanical properties of ceramics show considerable scatter in the measured results. The main reason for the scatter in the values measured is a consequence of the presence, size and distribution of cracks in ceramics. A mean value must be determined via statistical evaluation. The most commonly used statistical approach for describing experimental data is Gaussian normal distribution. In ceramics, however, the use of the Weibull distribution is preferable, reviewed below. 

The mechanical properties of ceramics are influenced by the particle size of both the base ceramic and of the added phases. Thus, to obtain a fine-grained... 

Garter, G. Barry, and M. Grant Norton. Ceramic Materials Science and Engineering. New York Springer, 2007. Covers ceramic science, defects, and the mechanical properties of ceramic materials and how these materials are processed. Provides many examples and illustrations relating theory to practical applications suitable for advanced undergraduate and graduate study. 

The mechanical properties of ceramic materials are strongly influenced by the strong interatomic bonds that prevail. Dislocation mechanisms, which create slip mechanisms in softer metals, are relatively scarce in ceramics, and failure may occur with very little plastic deformation. Ceramics also tend to fracture with little resistance. 

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