Overview
ISO 23524:2022 specifies the Essential Work of Fracture (EWF) method for measuring the fracture toughness of polymeric films and thin sheets (thickness ≤ 1 mm) in mode I (crack opening) under plane stress. The standard uses double-edge-notched tensile (DENT) specimens and force–displacement data to partition the total fracture energy into an essential work (energy to create new surfaces) and a non‑essential (plastic) work dissipated around the fracture zone.
Key topics and technical requirements
- Scope and applicability: For ductile polymer films/thin sheets with stable (slow) crack propagation. If brittle, fast fracture occurs, the method is not applicable.
- Specimen geometry: Series of DENT specimens with constant thickness, width and length but varying ligament length (b). A minimum ligament length of 5 mm is specified to ensure plane stress conditions.
- Measured quantities:
- Overall fracture energy (Wf) from area under force–displacement curves.
- Specific fracture energy wsf = Wf / (h·b).
- Essential work of fracture we (kJ/m2) and non‑essential work wp (MJ/m3 via β·wp) obtained by linear regression of wsf versus b.
- Test procedure elements:
- Controlled displacement rate (test speed) and use of extensometers or grip‑displacement as defined.
- Conditioning of specimens to standard atmospheres (see ISO 291).
- Calibration and verification of force and extensometer systems per referenced standards.
- Data analysis:
- Linear least‑squares regression to determine we and β·wp.
- Outlier criteria, reporting of average maximum stress and statistical treatment are included.
- Limitations: Intended for thin, ductile materials with full or stable ligament yielding; full yielding verification is not required for routine use but affects interpretation.
Applications and users
- Practical uses:
- Characterizing fracture toughness of packaging films, coatings and flexible polymer components.
- R&D for new polymer formulations and multilayer films.
- Quality control and production testing for film manufacturers.
- Interlaboratory comparisons and materials benchmarking.
- Typical users:
- Materials testing laboratories, polymer R&D teams, quality engineers, and standards bodies requiring reproducible fracture energy metrics for thin polymer products.
Related standards
Normative references cited in ISO 23524 include:
- ISO 291 - Conditioning atmospheres for plastics
- ISO 2818 - Specimen preparation by machining
- ISO 4593 - Film/sheet thickness measurement
- ISO 7500‑1 and ISO 9513 - Calibration/verification of testing and extensometer systems
- ISO 16012 - Determination of linear specimen dimensions
Keywords: ISO 23524, essential work of fracture, EWF method, fracture toughness of films, polymeric films, thin sheets, DENT specimens, plane stress, fracture energy.