ISO 899-2:2024

Overview - ISO 899-2:2024 (Flexural creep by three-point loading)

ISO 899-2:2024 specifies a standardized method to determine the flexural creep behaviour of plastics using a simple three-point loading (mid-span loaded, freely supported beam) test. The standard applies to rigid and semi-rigid non-reinforced, filled and fibre‑reinforced plastics (test specimens moulded or machined), under defined pre‑treatment, temperature and humidity conditions. It is intended to provide reliable data for engineering design, quality control, and research & development.

Key technical topics and requirements

• Test geometry and scope

  • Three‑point loading on a freely supported beam; span typically (16 ± 1) times specimen thickness for normal specimens (special spans for unidirectional fibre‑reinforced specimens).
  • Specimen shape and dimensions aligned with relevant material standards and ISO 178 guidance.

• Apparatus and measurement

  • Test rack with adjustable supports and specified loading/support radii (see Table 1 in the standard).
  • Loading system that applies load smoothly and maintains it to within ±1 %.
  • Deflection‑measuring device conforming to Class 1 of ISO 9513 (contact or contactless) to avoid influencing specimen behaviour.
  • Time‑measurement accuracy 0.1 %; micrometer resolution 0.01 mm; vernier calipers accurate to 0.1 % of span.

• Procedure essentials

  • Conditioning and controlled test atmosphere per standard (temperature and relative humidity).
  • Defined steps for preloading, loading, and a deflection‑measurement schedule.
  • Optional measurement of recovery rate after unloading.
  • Data calculation methods for flexural‑creep modulus (Et), flexural‑creep compliance (Dt), flexural stress, flexural‑creep strain, time to rupture, and creep‑strength limit.

• Results and reporting

  • Presentation formats include creep curves, creep‑modulus/time curves, isochronous stress‑strain plots, 3‑D representations, and creep‑to‑rupture curves.
  • Precision, test report content and annex on physical‑ageing effects are included.

Practical applications and users

• Materials and polymer testing laboratories performing creep testing for plastics.
• Product designers and structural engineers using long‑term mechanical property data for engineering design and component life prediction.
• Quality‑control teams assessing batch consistency and production compliance.
• R&D groups investigating material formulations, fibre orientation effects, and time‑dependent behaviour.
• Note: the method can be unsuitable for some fibre‑reinforced materials (due to fibre orientation) and certain rigid cellular plastics - see ISO 1209‑1/2.

Related standards (for cross‑reference)

• ISO 178 - Determination of flexural properties
• ISO 291 - Standard atmospheres for conditioning and testing
• ISO 472 - Plastics vocabulary (definitions)
• ISO 9513 - Extensometer calibration (Class 1)
• ISO 16012 - Determination of linear specimen dimensions
• ISO 1209‑1 / ISO 1209‑2 - Considerations for rigid cellular plastics

Keywords: ISO 899-2, flexural creep, three-point loading, plastics creep behaviour, flexural‑creep modulus, creep testing, engineering design, quality control, R&D.