Overview
ISO 11093-7:2011 specifies a standardized three‑point bending method for determining the flexural modulus (Young’s modulus) of cylindrical paper and board cores. It applies to cores with an internal diameter of 50 mm to 350 mm, a minimum wall thickness of 0.05 × internal diameter (but not less than 10.0 mm), and a minimum core length of 10 × internal diameter (but not less than 1 000 mm). The method treats the core as a slender beam and uses static bending theory to compute flexural modulus from measured load and deflection.
Key topics and technical requirements
- Scope and sample rules
- Minimum of five test pieces; length normally 10 × internal diameter or (1 000 ± 2) mm when shorter.
- Sampling and moisture conditioning per ISO 11093-1 and ISO 11093-3.
- Apparatus
- Lower and upper vee‑arranged bearings (120° ± 2°); roll diameter (30 ± 1) mm.
- Displacement gauge to measure deflection (accuracy ±0.01 mm when machine used).
- Load applied by a belt with hanging weights (≈50 mm wide) or by a material‑testing machine.
- When using a testing machine, loading rate (10 ± 0.1) mm/min and force measurement accuracy ±0.1 N.
- Test procedure
- Centre test piece on supports with specified centre‑to‑centre distances: lower bearings L = length − 300 mm; upper bearings l = length − 600 mm (tolerances ±2 mm).
- Apply load at midpoint; required deflection f must be between 0.20 mm and 0.70 mm.
- Read deflection within 2 s of applying hanging weight, or determine force producing the specified f when using a machine.
- Calculation and reporting
- Flexural modulus E is calculated from the recorded load (F), deflection (f), bearing distances (L, l), and core diameters (D, d) using the equation in Clause 8 (based on slender‑beam bending theory).
- Test report must include sample IDs, moisture content, L/D/d, F and f, individual and mean E, method of loading, and any deviations.
Applications and users
- Ensures core stiffness and bending resistance specifications for:
- Paper and board core manufacturers
- Reel and winding operations in paper mills
- Packaging converters and roll‑handling equipment designers
- Quality control and materials testing laboratories
- R&D teams assessing core materials and designs
- Useful for comparing core materials, verifying supplier claims, and ensuring reliable winding/reel performance.
Related standards
Keywords: ISO 11093-7:2011, flexural modulus testing, three-point method, paper cores, core stiffness, testing of cores, paper and board standards.