ISO 21113:2018

Overview

ISO 21113:2018 specifies a standardized laboratory test method for determining the fracture toughness of monolithic ceramic thin plates at room temperature. It covers two specimen-based approaches: the single-edge precracked plate (SEPP) method and the single-edge V‑notch plate (SEVNP) method. The standard applies to monolithic ceramics and whisker- or particulate-reinforced ceramics regarded as macroscopically homogeneous (plate thickness 0.2 mm to <1.0 mm) and excludes continuous-fibre‑reinforced ceramic composites.

Key Topics and Technical Requirements

• Test methods: Three‑ or four‑point bending fracture tests on precracked or V‑notched rectangular plate specimens.
• Specimen geometry & tolerances:
  • Width typically 4.0 ± 0.2 mm; length ≥ 36 mm or ≥ 45 mm depending on configuration; thickness 0.2–1.0 mm.
  • Parallelism tolerance on long faces: 0.015 mm; perpendicularity tolerance: 0.01 mm; thickness variation < 10% of average.
• Precrack and notch preparation:
  • SEPP: a straight-through pop‑in precrack induced by three‑point bending of a saw‑notched specimen bonded to a brass beam (detailed preparation in Annex A).
  • SEVNP: sharp V‑notch machined using a reciprocating razor blade with diamond paste (Annex B); V‑notch method recommended only for materials with grain sizes ≳1 μm.
  • Notch‑root radius should be similar to or less than twice the average grain size; V‑notch unsuitable for Y‑TZP and some very tough/soft ceramics that do not form a sharp crack.
• Apparatus & measurement:
  • Test machine accuracy per ISO 7500‑1 (force accuracy 1%); crosshead speed typically 0.5 mm/min.
  • Roller pin diameters 4.0–5.0 mm; roller surface roughness Ra ≤ 0.4 μm.
  • Measure fracture load, specimen dimensions and precrack/notch length; precrack length measurement and validity assessment described in Annex C.
• Data analysis:
  • Fracture toughness (KIC) is calculated from fracture load, specimen geometry and a stress‑intensity shape factor (Y). The standard gives specific formulae, acceptance criteria and statistical reporting (mean and standard deviation). Minimum specimen counts and validity rules are specified (prepare ≥8 specimens; ≥5 valid results required).

Applications

ISO 21113:2018 is intended for:

• Material development and R&D - comparing toughness of fine‑ceramic formulations.
• Quality assurance and production control - routine verification of fracture properties for thin ceramic plates.
• Characterization, reliability and design data - providing KIC values for component design and failure assessment. Who uses it: materials scientists, ceramic engineers, test laboratories, QA teams, and designers of advanced ceramic components (electronic substrates, sensors, wear parts, thin structural ceramics).

Related standards

• ISO 15732 - fracture toughness by single‑edge precracked beam (SEPB) method (reference within ISO 21113).
• ISO 7500‑1 - verification/calibration of force measurement for testing machines.

Keywords: ISO 21113:2018, fracture toughness, monolithic ceramic thin plates, single-edge precracked plate, single-edge V-notch plate, fine ceramics, advanced ceramics, test method, room temperature.