Overview
ISO 13118:2024 specifies a standardized test method for determining the biaxial elasticity properties of woven fabrics that exhibit stretch due to elastomeric fibres, mechanical processing, or chemical treatment. The method uses a cruciform test piece and a constant rate of extension (CRE) biaxial tensile testing machine to apply simultaneous orthogonal loads and record force and extension for calculation of elasticity, force decay, permanent deformation and related parameters.
Key topics and technical requirements
- Test specimen: cruciform shape (recommended overall arm length and widths given in the standard); internal corners rounded (radius R = 15 mm) and gauge marks placed symmetrically for optical measurement. Specimens must be cut away from edges (no closer than 150 mm) and free of folds or selvedges.
- Sampling & quantity: two sets of specimens (warp and weft), each set typically containing at least five specimens unless higher precision is required.
- Conditioning: preconditioning and testing atmospheres as specified in ISO 139; specimens conditioned at least 24 h in a tension‑free state.
- Apparatus: CRE biaxial tensile testing machine capable of simultaneous orthogonal loading, optical extensometry, and data recording for force and gauge length in both warp and weft directions.
- Machine performance: force-measuring system accuracy conforming to class 1 of ISO 7500-1 (error not exceeding ±1% for force; gauge length error not exceeding ±1 mm). CRE speed capability typically in the range indicated by the standard (machine accuracy ±10%); standard rate example: set extension/retraction to 6 N·cm·min^-1.
- Test procedure: set grip separation (default 200 mm ± 1 mm), align warp/weft axes with loading axes, cycle between gauge length and specified load or grip separation, and record simultaneous force/strain data.
- Measured outcomes: biaxial stress–strain behaviour, maximum force/extension, force decay (time and exercising), permanent deformation, recovered elongation.
Applications and users
ISO 13118:2024 is relevant for:
- Textile testing laboratories performing quality control of stretch woven fabrics
- Fabric manufacturers and converters developing elastomeric or mechanically/chemically elastic woven products
- Apparel and technical textile R&D teams validating biaxial elongation behavior for comfort, fit, and performance
- Test-equipment manufacturers and certification bodies implementing CRE biaxial test setups
This standard supports consistent evaluation of fabric elasticity where biaxial loading better represents real-use conditions (e.g., garments, upholstery, automotive textiles, and engineered textile products).
Related standards
- ISO 139 - Standard atmospheres for conditioning and testing
- ISO 7500-1 - Calibration and verification of static uniaxial testing machines (force-measuring accuracy)
- ISO 20932-1 (referenced for terminology)