ISO 15024:2023

Overview

ISO 15024:2023 specifies a laboratory test method to determine mode I interlaminar fracture toughness (critical energy release rate, G_IC) of unidirectional fibre‑reinforced plastic composites using a double cantilever beam (DCB) specimen. The second edition updates the DCB configurations (including an insert‑hinge option) and provides procedures to measure both initiation and propagation fracture toughness, generate R‑curves, and report statistically valid results. The method is limited to zero‑degree unidirectional lay‑ups.

Keywords: ISO 15024:2023, G_IC, mode I interlaminar fracture toughness, DCB test, fibre‑reinforced plastic composites, unidirectional.

Key topics and technical requirements

• Test principle: Apply a mode I opening load to a DCB specimen with a non‑adhesive starter film to simulate an initial delamination and record load–displacement behaviour to obtain G_IC (initiation and propagation).
• Specimen and preparation: Guidance on test plate production, preferred and alternative specimen geometries, starter film insertion and precracking (precrack by unloading after initial delamination growth).
• Apparatus: Requirements for test machine, load blocks or piano hinges (and insert hinges), measuring devices, optional travelling microscope, and non‑adhesive insert film.
• Data acquisition and reduction: Procedures for measuring delamination length, defining key points on the load–displacement trace (VIS, NL, MAX, 5%/MAX, PROP), and calculating G_IC using specified methods:
  • Method A: Corrected beam theory (CBT)
  • Method B: Modified compliance calibration (MCC)
• R‑curve generation: Plotting G_IC versus delamination length to show initiation and propagation behaviour; discussion of fibre bridging and its effect on R‑curve shape.
• Quality and reporting: Number of specimens, conditioning (ISO 291 referenced), precision, and required test report content. Normative references include ISO 291, ISO 527‑1, ISO 1268, ISO 7500‑1 and ISO 9513.

Applications and practical value

• Provides a standardized, repeatable method to quantify delamination resistance in unidirectional polymer‑matrix composites.
• Useful for:
  • Material development and selection (resins, fibres, interleaves)
  • Comparative evaluation of composite layups and manufacturing processes
  • Failure analysis and durability studies (delamination susceptibility)
  • Qualification and quality control in aerospace, automotive, wind energy, marine and sports equipment industries
• Helps engineers and test laboratories produce defensible fracture toughness data (G_IC) for design allowables and simulation inputs.

Related standards

• ISO 291 - Conditioning and testing atmospheres
• ISO 527‑1 - Tensile properties of plastics (general principles)
• ISO 1268 - Production of composite test plates
• ISO 7500‑1 - Calibration of force measuring systems
• ISO 9513 - Calibration of extensometer systems

For practitioners performing DCB tests, ISO 15024:2023 is the authoritative reference for apparatus, specimen preparation, test execution, data reduction (CBT and MCC), and reporting of mode I interlaminar fracture toughness for unidirectional fibre‑reinforced plastics.