Biomedical Engineering Reference
In-Depth Information
4
Failure mechanisms of ceramic
nanocomposites
P. HVIZDOS
ˇ
, P. TATARKO, A. DUSZOVA
and J . DUSZA , Slovak Academy of Sciences, Slovakia
Abstract: This chapter first builds a basic understanding of structural
failure and its determining critical factors. It describes typical fracture
origins and modes of crack propagation. It then deals with the concept
of reinforcing ceramic nanocomposites. Different strategies for
preventing failures are discussed, and the influence of microstructure and
secondary nanometric phases on friction and wear properties of some
ceramic nanocomposites is described.
Key words: mechanical properties, strength, fracture toughness, damage
mechanism, wear.
4.1
Introduction
Due to their crystallographic structure and strong atomic bonds, modern
ceramic materials have many excellent properties. These include extremely
high hardness and strength, high thermal and chemical stability, high
corrosion and wear resistance. However, these strong atomic bonds (usually
covalent or ionic) limit the possibility of dislocation movement and plastic
deformation. This leads to their well-known weakness - low fracture
toughness and poor resistance to crack growth and the resultant high
brittleness and lower reliability.
Reliability is closely related to the presence of technological defects within
the microstructure (i.e. flaws that arise during processing steps such as
mixing and sintering). These flaws include pores and their clusters,
impurities, clusters of secondary phases and large grains. Flaws in
manufactured parts are difficult to identify and cannot be eliminated easily,
thus creating stress concentrators during machining and/or shaping.
