| Tow format and product range | Filament count per tow, commonly designated 1K, 3K, 6K, 12K, 24K, or 48K; product form and available sizing options. | Product specifications, technical data sheets, and sample inspection. “K” denotes approximately one thousand filaments. | Assess whether the product formats and surface treatment options match the intended process and application; tow size alone does not establish fiber quality. |
| Tensile strength and modulus | Tensile strength (MPa or GPa), tensile modulus (GPa), and elongation at break (%). | Tow testing may use ASTM D4018 or ISO 10618; single-filament tensile testing is covered by ISO 11566. Compare results obtained using equivalent test conditions. | Check the reported fiber grade, test method, sample count, and lot-to-lot results. Values should be compared within the same product class and test setup. |
| Linear density and tow consistency | Linear density, typically reported in tex, plus the measured variation across samples or production lots. | ISO 1889 specifies a method for determining the linear density of reinforcement yarns. Request the sampling plan and test records. | Consistent linear density supports predictable material handling and process control. Confirm that the supplier’s stated tolerances suit the buyer’s specification. |
| Fiber density | Density, generally reported in g/cm³, with the test method and sampling details. | ISO 10119 covers the determination of carbon fiber density. Review batch records or independent laboratory reports. | Use density as one material-identification and consistency measure; it should be interpreted alongside mechanical properties and the specified fiber grade. |
| Sizing and resin compatibility | Sizing type and content, recommended resin systems, and application-specific composite performance data. | Technical data sheets, sizing documentation, and trials using the intended resin and manufacturing process. | There is no single sizing choice suitable for every resin or process. Confirm compatibility through application-relevant testing. |
| Manufacturing capability and supply continuity | Declared production capacity, actual output, lead times, product mix, and documented delivery performance. | Facility audits, production records, capacity documentation, and shipment history relevant to the requested product. | Distinguish installed capacity from available, qualified output. Confirm that supply commitments apply to the required grade and specification. |
| Quality management and traceability | Quality-system certification status, batch identification, retained samples, nonconformance records, and corrective-action procedures. | Verify certificates with the issuing body and check their scope and validity. Review lot-level test reports and traceability records. | A certificate such as ISO 9001 indicates a quality-management system; it does not by itself certify that a particular fiber grade meets a buyer’s requirements. |
| Laboratory reliability | Test-method compliance, equipment calibration, laboratory competence, and report traceability. | Review calibration records and whether relevant testing is performed by a laboratory accredited to ISO/IEC 17025 for the applicable test scope. | Accreditation applies to defined activities within a laboratory’s scope; check that the specific test and method are covered. |
| Environmental performance | Reported energy use, emissions, waste-management practices, and applicable environmental permits or certifications. | Review dated facility records, certification scope, and the boundary and method used for any environmental metrics. | Compare figures only when their reporting boundaries, units, and periods are comparable; distinguish verified data from estimates. |