Overview
ISO/TS 17958:2013 - "Paper and board - Determination of fracture toughness - Constant rate of elongation method (1.7 mm/s)" specifies a laboratory method to determine the fracture toughness of paper and paperboard using a tensile testing machine operated at a constant elongation rate. The Technical Specification combines tensile testing and notched fracture testing (based on nonlinear fracture mechanics / J‑integral theory) to produce material parameters used to rank fracture strength and fracture strain for a defined ISO paper web geometry.
Key topics and technical requirements
- Test principle: Two material tests (un‑notched and centre‑notched) under a constant rate of elongation, with force and elongation recorded to compute fracture toughness (Jcr) and related parameters.
- Constant rate: Test run at 1.7 mm/s (constant rate of elongation method).
- Test pieces & geometry: Requirements for 50 mm wide fracture toughness pieces with a 20 mm centre notch, and provision for 15 mm and 50 mm test widths. Notch and positioning tolerances are specified for repeatability.
- ISO reference web geometry: A standardized notched web (2 m × 1 m with a 10 mm edge notch) used to derive ISO fracture strength and ISO fracture strain for ranking materials.
- Apparatus & fixtures: Tensile testing machine per ISO 1924‑3, anti‑buckling guide to keep notched region flat (specified compression force), cutting and notch‑making devices, and a computer for calculations.
- Preparations & conditions: Sampling, conditioning, and determination of grammage are required (references to ISO sampling and conditioning practices).
- Calculations and reporting: Procedures for calculating fracture toughness, apparent tensile strength/strain, indexed parameters, uncertainty, and reporting test results.
- Scope limits: Applicable to most paper and board grades, but excludes special grades that do not show monotonically decreasing tangential stiffness (e.g., creped paper) and does not apply to corrugated fibreboard.
Applications and users
- Practical applications:
- Ranking and comparing fracture properties of paper grades.
- Predicting web breaks and fracture behaviour in continuous web handling (manufacture, winding, printing).
- Material development and quality control where fracture performance matters.
- Who should use it:
- Paper and paperboard manufacturers, converters, and print operation engineers.
- Testing laboratories and R&D teams conducting mechanical performance evaluation.
- Material scientists applying fracture mechanics to thin sheet materials.
Related standards
- ISO 1924‑3 - Tensile properties (constant rate of elongation)
- ISO 186 - Sampling to determine average quality
- ISO 187 - Standard atmosphere and conditioning
- ISO 536 - Determination of grammage
Keywords: ISO/TS 17958:2013, fracture toughness, paper and board, constant rate of elongation, tensile testing, fracture strength, fracture strain, notched test piece, ISO paper web geometry, J‑integral.