Breviary Technical Ceramics






7.6 Summary of Important Guiding Principles

  • Design with ceramic materials requires an approach fundamentally different from design with metals. Different principles of construction, calculation procedures and joining processes must be applied.
  • The integration of ceramic parts with a metallic system results in different requirements from the ceramic part, the assembly environment and the bond between the two. Compromises are often necessary, and these may also lead to changes in the metallic system.
  • As a rule, copying a metal part or its exact conversion to ceramic leads to failure.
  • The advantages of using ceramic for the system should be utilized as far as possible, while the weaknesses should be avoided and unfavourable loading minimized.
  • The properties resulting from the nature of the chemical bonding in ceramics, which is the reason for their high hardness, must be taken into account differently compared with metals:
    • brittleness,
    • cracks and crack growth in the material,
    • high scatter of strength data,
    • low tensile strength,
    • limited variety of forms and
    • larger tolerances for non-machined parts.
  • Finishing is typically time and cost intensive and should thus be avoided, or at least reduced to a minimum.
  • Very close cooperation with the ceramic manufacturer is necessary, since the technical and economic implementation using ceramics is even more demanding than with metals or plastics.

An indicator for the cost of a part is the degree of difficulty represented by the demands on a ceramic part. This can be divided into five levels. A low level of difficulty should therefore be aimed at if a cost-effective product is to be obtained.

Degree of difficulty

Demands on the
ceramic part

Design is crucially influenced by


  • low mechanical stress
  • application temperature room temperature

forming process
(tooling costs, etc)


  • as in 1 +
  • specified dimensional and mould tolerances

forming process, finishing (possibilities and costs)


  • as in 2 +
  • specified surface quality

(possibilities and costs)


  • greater mechanical stress
  • and / or thermally
    induced stress

stress distribution in the part under load


  • as in 4 +
  • Joining with other parts

forming and finishing
(dimensional and mould
tolerances, costs)
stress distribution in the composite under load

Table 24: Levels of difficulty


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