Overview
ISO 19375:2024 specifies a micromechanical single-fibre pull-out test for measuring the interfacial shear strength (IFSS) between a single reinforcement fibre and a surrounding matrix. The method also enables measurement of the critical energy release rate (CRE). It is intended for stiff reinforcement fibres (for example carbon fibres, glass fibres, basalt fibres) and is applicable to thermoset, thermoplastic and fine‑grained concrete matrices, as well as some polymeric and inorganic matrices.
The standard defines the principle, apparatus, specimen preparation, test procedure, evaluation methods and reporting requirements for reliable IFSS and CRE data.
Key topics and technical requirements
- Scope and applicability
- Applicable to stiff reinforcement fibres and thermoset/thermoplastic/concrete matrices.
- Not applicable to: elastomeric fibres or matrices, matrices that cure/melt above 400 °C, matrices prone to significant bubbling/expansion during preparation, or foams.
- Apparatus and measurements
- Fibre diameter determination (optical methods and vibroscopic linear density).
- Embedding station and controlled matrix droplet formation.
- CRE testing machine for precise force–displacement recording.
- Specimen preparation
- Detailed steps for fibre sampling, insertion, matrix preparation, droplet formation, solidification and conditioning.
- Validation checks and specimen acceptance criteria before testing.
- Test procedure
- Standardized pull-out test setup, clamping, testing conditions and validation procedures.
- Evaluation and results
- Recorded parameters: fibre diameter, embedded length, maximum pull-out force.
- Derived values: apparent interfacial shear strength, interfacial frictional force/stress, local IFSS (from debonding force), and critical energy release rate.
- Requirements for test reporting and statistics.
Applications
ISO 19375:2024 is designed for practical use in:
- Materials research and development for composite systems.
- Quality assurance and product development of fibre‑reinforced composites.
- Comparative assessment of fibre–matrix bonding (e.g., sizing/treatment effects).
- Fracture mechanics studies where CRE at the fibre–matrix interface is relevant.
- Calibration and validation of micromechanical models of composite behaviour.
Who should use this standard
- Composite materials researchers and academic laboratories.
- Materials and process engineers in aerospace, automotive, wind energy and construction.
- Quality control and testing laboratories performing micromechanical interfacial characterisation.
Related standards
For comprehensive composite testing programs, consult the ISO catalogue for other ISO test methods on fibre characterization, composite mechanical testing and fracture mechanics. Refer to ISO 19375:2024 for full procedural details, annex examples and reporting templates.