Overview
ISO 11093-9:2019 defines a standardized method to determine the maximum flat crush resistance of wound paper and board cores. The procedure measures the load acting at right angles to the core axis at the first maximum (or levelling off) of the crushing force. Results are reported in kilonewtons per metre (kN/m) and are intended to provide consistent core strength data for design, quality assurance and conversion processes.
Note: If the wall thickness of the core is less than 5 mm, the breaking point is not detectable and the note in the scope applies.
Key Topics
- Principle: A test piece is compressed between parallel pressure platens with its axis parallel to the platen plane until the first maximum or levelling of the load is exceeded.
- Apparatus:
- Compression testing machine calibrated per ISO 7500-1. Force measurement accuracy: ±1 % of the smallest crushing load measured.
- Flat, rigid, parallel upper and lower platens; platen travel limited to vertical motion only.
- Cutting device (recommended circular saw) producing 90° ± 1° cuts without feathering or deformation.
- Preparation:
- Sampling in accordance with ISO 11093-1.
- One test piece per specimen, taken at least 100 mm from core ends.
- Test piece length: (100 ± 1.5) mm for nominal internal diameter ≤ 300 mm; (300 ± 1.5) mm for > 300 mm.
- Conditioning per ISO 11093-2 and testing in the same standard atmosphere.
- Procedure details:
- Compression rate: constant relative platen rate between 50 mm/min and 65 mm/min.
- Switch-off limit for automatic break detection: 30 N or 3 % from the true value.
- Convert measured force to kN/m to ensure comparability across core diameters.
- Calculation & Reporting:
- Flat crush resistance is calculated from the measured force and expressed in kN/m.
- Test report must reference ISO 11093-9 and include specimen details, sampling/testing dates, individual values and mean (rounded to 1 %), and any departures from the procedure.
Applications
This standard is directly applicable to:
- Packaging designers assessing core performance under lateral load.
- Converters and manufacturers performing incoming inspection and process control.
- Quality assurance teams establishing acceptance criteria for cores used in winding, shipping or storage.
Practical benefits include reproducible strength data for product specification, reduced variability in acceptance testing, and improved compatibility between suppliers and users.
Related Standards
For implementation, follow the procedures and reporting requirements in ISO 11093-9:2019 and consult the referenced parts for sampling, conditioning and machine calibration to ensure valid, comparable results.