Overview
ISO 13931:2013 specifies laboratory procedures for determining the volume resistivity of carbon fibre. The standard defines two test methods: Method A (single filament) and Method B (strand), including required apparatus, specimen preparation, measurement procedures and reporting. ISO 13931 is intended for producers, test laboratories and users who need reliable, comparable measurements of carbon fibre electrical resistivity for quality control, R&D and specification compliance.
Key topics and requirements
- Two test methods
- Method A (single filament): measures resistance of individual filaments. Assumes circular filament cross‑section and calculates volume resistivity from measured resistance, filament diameter and gauge length.
- Method B (strand): measures resistance of a strand. Cross‑sectional area is derived from strand linear density (tex) and density, then used with measured resistance and length to calculate volume resistivity.
- Apparatus and accuracy
- Length meter accurate to 0.1 mm.
- DC resistance meter with precision of 0.5% or better.
- Method B requires flat copper plate electrodes and an insulating board for electrode spacing.
- Specimen preparation
- Method A: isolate single filaments from a 40–50 mm fibre sample, mount on a thin template with conductive adhesive and attach a copper lead wire.
- Method B: prepare whole strands; pretreatment (drying or size removal per ISO 10548) if sizing or moisture could affect results.
- Measurement procedure
- Measure resistance and gauge length; read resistance shortly after powering the meter (example: within ~30 s in Method B).
- Volume resistivity is computed from the specimen resistance, length and cross‑sectional parameters (diameter for single filaments; linear density and density for strands). Variables used in formulas include S (volume resistivity), R (resistance), L (length), D (diameter), T (linear density), ρ (density).
- Reporting
- Report must reference ISO 13931, method used, material identification, test conditions (temperature/humidity/conditioning time), specimen dimensions, individual results and mean (if required), number of specimens and date.
Applications and users
- Who uses it: carbon fibre manufacturers, composite fabricators, test laboratories, material engineers and R&D teams.
- Why it matters: volume resistivity is critical for applications where electrical conductivity or insulation matters-antistatic materials, EMI shielding, conductive composites, sensors and certain aerospace, automotive and electronics components where consistent electrical properties are required.
Related standards
Normative references cited in ISO 13931 include:
Keywords: ISO 13931, carbon fibre volume resistivity, carbon fiber resistivity testing, volume resistivity test method, Method A single filament, Method B strand.