ISO 527-5:2021

Overview

ISO 527-5:2021 - Plastics - Determination of tensile properties - Part 5: Test conditions for unidirectional fibre-reinforced plastic composites - defines standardized conditions for measuring tensile behaviour of unidirectional (UD) fibre‑reinforced polymer composites. Based on the general principles of ISO 527-1, the standard covers specimen geometry, apparatus, test procedure and the calculation of tensile strength, tensile modulus, Poisson’s ratios and other stress‑strain characteristics for UD composites.

Key topics and technical requirements

• Scope and materials: Applicable to polymer matrix systems (thermoplastic or thermosetting), including prepregs, reinforced with unidirectional fibres such as carbon, glass, aramid and similar fibres. Not normally suitable for multidirectional laminates (see ISO 527-4).
• Specimen types: Two principal specimen geometries are specified - Type A (longitudinal/0°) and Type B (transverse/90°) - with guidance on gauge marks, dimensions and preparation.
• Apparatus and measurement: Equipment shall conform to ISO 527-1 with specific exceptions; a micrometre readable to 0.01 mm is required for dimensional checks. Hydraulic grips that allow constant grip pressure are recommended to avoid crushing fragile composite edges.
• Gripping and end tabs: Guidance on end-tab application and grip pressure to prevent slippage while avoiding damage; Annex B includes use of unbonded tabs and tab‑less gripping conditions.
• Strain measurement: Use of extensometers or strain gauges is described; note that transverse strain gauges on anisotropic composites require correction for transverse effects when determining Poisson’s ratio.
• Test procedure and data: Conditioning, test speed, prestress handling, alignment checks (Annex A), data recording and calculation of properties per ISO 527-1 principles are specified.
• Supporting annexes: Annex A (alignment), Annex B (unbonded tabs & fine grip faces), Annex C (specimen preparation).

Applications and practical value

• Provides robust, repeatable methods to evaluate tensile strength, elastic modulus, failure strain and Poisson’s ratios of UD composites.
• Used during material development, quality control, certification and engineering design for aerospace, automotive, sporting goods, wind energy and other composite‑intensive industries.
• Enables comparative material selection, laminate design validation and input for finite element models that require accurate tensile properties.

Who should use ISO 527-5

• Materials engineers, test laboratories, composite manufacturers, R&D teams, and certification bodies assessing unidirectional fibre‑reinforced plastics.

Related standards

• ISO 527-1:2019 (general principles)
• ISO 527-4 (isotropic/orthotropic reinforced materials)
• ISO 1268 (test plate production)
• ISO 16012 & ISO 2818 (measurement and specimen preparation)

Keywords: ISO 527-5, tensile properties, unidirectional fibre-reinforced composites, tensile modulus, Poisson’s ratio, specimen preparation, carbon fibre, glass fibre, aramid.