Overview
EN ISO 21765:2021 (ISO 21765:2020) specifies an automatic test method for determining the deformability of textile fabrics by forced mechanical distension. The method applies to a wide range of textiles including woven and knitted fabrics, nonwovens, non‑crimp fabrics, and continuous‑fibre reinforcement textiles (for example fabrics made from glass rovings or untwisted carbon filament yarns). It is not applicable to resin‑impregnated fabrics. The procedure can be used with fabrics treated with powder binder and, for multi‑axial non‑crimp fabrics, evaluation of fibre orientation and gaps is limited to the uppermost layer.
Keywords: EN ISO 21765:2021, ISO 21765:2020, fabric deformability, forced mechanical distension, textile testing standard, deformability test.
Key Topics
- Principle: automatic forced mechanical distension to provoke fabric deformation and capture geometric and mechanical responses.
- Apparatus & Test Specimen: requirements for the test machine and specimen preparation to ensure repeatable results.
- Test Procedure: automated insertion, test parameters, evaluation parameters and standardized test sequences.
- Evaluation & Calculations: characteristic values and calculations vary by fabric type (non‑crimp, woven, knitted, nonwovens) and include:
- Deformation force
- Gap width, gap area, gap portion and gap shape
- Fibre‑angle change, shearing angle (where applicable)
- Undulation, waviness, loop formation, out‑of‑roundness
- Residual deformation, anisotropy, thinning‑out
- Reporting & Annexes: standardized test report contents, example images and statistical data guidance.
Applications
EN ISO 21765 is practical for:
- Textile manufacturers assessing drapability and forming behavior of fabrics.
- Composite materials engineers selecting reinforcement textiles (glass, carbon, non‑crimp) for molding and lay‑up processes.
- R&D and test laboratories performing objective, repeatable deformability measurements for quality control and product development.
- Process engineers who use deformability data to set tooling, forming speeds, and binder treatments.
Use cases include predicting fabric behaviour during thermoforming, validating materials for automated layup, comparing treatments (e.g., powder binders), and providing specification data for suppliers and OEMs.
Related Standards
- Standard prepared by ISO/TC 38 and CEN/TC 248; it complements other ISO textile testing standards covering conditioning atmospheres, mechanical tests, and composite material testing. Consult relevant ISO/CEN catalogs for associated test methods and conditioning standards.
For procurement or compliance searches, use terms like EN ISO 21765:2021, fabric deformability test, and textile forced mechanical distension to find full normative text and detailed procedures.