ISO 899-2:2003

Overview

ISO 899-2:2003 - Plastics - Determination of creep behaviour - Part 2: Flexural creep by three‑point loading specifies a standardized laboratory method to measure the flexural creep of plastics using a simple freely supported beam with a mid‑span (three‑point) load. The procedure covers specimen preparation, conditioning, test apparatus, loading and deflection measurement, calculations (flexural stress, flexural‑creep strain and flexural‑creep modulus) and presentation of results (creep curves, creep‑modulus/time curves and isochronous stress‑strain plots). The method is intended to produce data for engineering design, research and quality control.

Key topics and technical requirements

• Scope and materials: Applies to rigid and semi‑rigid non‑reinforced, filled and fibre‑reinforced plastics in dumb‑bell‑shaped specimens (moulded or machined). Caution: fibre orientation can affect results and the method may be unsuitable for some fibre‑reinforced or rigid cellular plastics.
• Test geometry: Span for normal specimens = (16 ± 1) × specimen thickness (special provisions for unidirectional fibre‑reinforced specimens). Radii for loading edge and supports are specified.
• Apparatus and measurement:
  • Rigid, levelled test rack with adjustable supports and a loading system maintaining load within ±1%.
  • Deflection device with accuracy within ±0.01% of final deflection; time measurement to 0.1%.
  • Micrometers and calipers for dimensions and span measurement.
• Conditioning and environment: Condition specimens per relevant material standard or ISO 291; test atmosphere should match conditioning. Temperature must be controlled (variation within ±2 °C) and humidity recorded as required.
• Loading and timing:
  • Progressive loading to full load between 1 s and 5 s.
  • Optional preload may be used; set deflection device to zero after preload.
  • Recommended measurement schedule includes short‑term and long‑term readings (e.g., 1 min, 3 min, 1 h, 10 h, 100 h, 1 000 h, etc.).
• Data for design vs QC: Engineering‑design requires extensometers to measure gauge length; research or QC may use nominal extension (change in grip distance).

Applications and users

• Who uses it: Materials engineers, R&D teams, product design and testing laboratories, quality control personnel, and certification bodies dealing with plastics performance.
• Practical uses:
  • Assess time‑dependent flexural performance for product design and life‑prediction.
  • Compare materials or formulations under controlled stress/time/temperature conditions.
  • Generate creep curves and isochronous stress‑strain data for finite‑element models and engineering specifications.

Related standards

• ISO 899‑1 (Tensile creep)
• ISO 178 (Flexural properties)
• ISO 291 (Conditioning atmospheres)
• ISO 472 (Plastics vocabulary)
• ISO 62 (Water absorption)
• ISO 1209‑1 / ISO 1209‑2 (Rigid cellular plastics - flexural tests)

Keywords: ISO 899-2, flexural creep, three-point loading, plastics testing, creep behaviour, flexural-creep modulus, creep curves, isochronous stress-strain.