ISO 10119:2020

Overview

ISO 10119:2020 specifies standardized laboratory methods for determining the density of carbon fibre tested as a yarn. The third edition defines four test methods and associated requirements for specimens, conditioning, apparatus, procedure, precision and reporting. Method C (density‑gradient column) is designated as the reference method in cases of dispute. The edition adds the gas pycnometer method (Method D) to the existing liquid‑based techniques.

Key topics and technical requirements

• Four approved methods:
  • Method A - Liquid‑displacement: weigh yarn in air and in an immersion liquid that wets the fibre; density derived from the buoyant force.
  • Method B - Sink/float: two variants (dynamic mixture or series of mixtures) to find the liquid density at which fibres are neutrally buoyant.
  • Method C - Density‑gradient column (reference): fibres locate at their equilibrium position in a prepared density gradient.
  • Method D - Gas pycnometer: uses inert gas to measure volume; higher resolution and avoids organic solvents.
• Specimen preparation: tests are normally carried out on desized fibres; size removal methods follow ISO 10548. Testing on sized fibre is permitted by agreement.
• Conditioning and environment: specimens and apparatus must be conditioned in a standard atmosphere per ISO 291 (preferred: 23 °C ± 2 °C and 50 % ± 10 % RH) and maintained at test conditions.
• Apparatus and calibration: requirements cover analytical balances, pycnometers/hydrometers, density‑gradient columns and gas pycnometers. Annexes address column preparation and calibration of measurement/expansion cells for pycnometry.
• Sources of error and controls: the standard identifies common errors (air bubbles, surface tension, convection) and notes optional measures (vacuum, ultrasonic treatment) and best practices to minimize them.
• Precision and reporting: procedures for expressing results, reporting test conditions, and recording calibration and method variant used are specified.

Practical applications

• Quality control of carbon fibre production (batch acceptance, in‑process checks).
• Material data verification for design calculations (density used to compute tensile strength and modulus on a per‑volume basis).
• Comparative testing and supplier‑customer disputes, with Method C serving as the reference.
• R&D and characterization where high resolution (Method D) or solvent‑free testing is preferred.
• Regulatory and certification testing where standardized measurement is required.

Who should use this standard

• Carbon fibre manufacturers and suppliers
• Independent testing laboratories and QC departments
• Composite material designers and engineers
• R&D teams developing fibre treatments or new fibre types

Related standards

• ISO 291 - Standard atmospheres for conditioning and testing
• ISO 1675 - Density determination by pyknometer method
• ISO 10548 - Carbon fibre - Determination of size content

Keywords: ISO 10119:2020, carbon fibre density, density determination methods, liquid‑displacement, sink/float, density‑gradient column, gas pycnometer, fibre testing, conditioning, ISO standards.