ISO 25217:2009

Overview

ISO 25217:2009 specifies a standardized test method, based on linear elastic fracture mechanics (LEFM), for determining the mode I adhesive fracture energy (GIC) of structural adhesive joints. The method uses double cantilever beam (DCB) and tapered double cantilever beam (TDCB) specimens to measure both crack initiation and stable crack propagation under an opening (mode I) load. Results include a critical strain energy release rate and an R‑curve (G vs crack length) describing fracture resistance.

Key topics and requirements

• Test principle: Determination of adhesive fracture energy (GIC) using DCB and TDCB specimens and LEFM analysis.
• Specimens: DCB and TDCB geometries with controlled adhesive layer thickness (specified < 1 mm) and a non-stick starter film (recommended PTFE) with thickness < 13 µm.
• Number of tests: Minimum of four joints per condition.
• Conditioning: Guidance on humidity and substrate drying to control moisture effects on adhesive properties.
• Test apparatus and control:
  • Tensile test machine in displacement control at 0.1–5 mm/min.
  • Load-cell calibrated to ±1% accuracy. Typical loads 100 N–5 000 N.
  • Crack-length measurement accuracy of ±0.5 mm (microscope or video).
  • Dimensional measurement accuracy: thickness ±0.02 mm; width ±0.05 mm.
• Data collection and analysis: Procedures for precracking (insert film or precrack), re-loading, measuring system compliance, extracting initiation and propagation data, and calculating GIC.
• Special procedures: Annexes cover system compliance measurement, handling unstable or stick‑slip crack growth, and detecting plastic deformation during tests.
• Reporting: Required test report content for DCB and TDCB tests, including specimen geometry, conditioning, load‑displacement traces and calculated G values.

Applications and users

ISO 25217:2009 is used where quantitative, comparable measurements of adhesive fracture resistance are needed:

• Adhesive manufacturers for product characterization and development.
• Materials and testing laboratories performing mechanical qualification and failure‑mode analysis.
• Structural engineers and designers (aerospace, automotive, marine, composites) assessing bonded joint durability and validating joint designs.
• Quality control and R&D teams requiring reproducible mode I fracture data for specifications and modelling.

Practical benefits include reliable input data for finite element fracture models, objective comparison between adhesives and substrates, and standardized acceptance testing.

Related standards

• ISO 291 (conditioning and testing atmospheres)
• ISO 10365 (designation of failure patterns)

Keywords: ISO 25217:2009, adhesive fracture energy, GIC, mode I, double cantilever beam, DCB, TDCB, structural adhesive joints, LEFM, fracture resistance.