ISO 18319:2015

Overview

ISO 18319:2015 specifies requirements for fibre-reinforced polymer (FRP) sheets used to upgrade concrete members. The standard focuses on unidirectional FRP sheets and defines how to express mechanical properties as characteristic values, sets criteria for appearance and dimensions, and prescribes sampling and test procedures. Properties for design are derived from the characteristic values and are to be applied within an appropriate design code in accordance with ISO 14484.

Key Topics

• Mechanical properties: Characteristic values required are tensile strength, Young’s modulus and ultimate strain. The characteristic tensile strength is obtained by subtracting three times the standard deviation from the mean strength. The characteristic Young’s modulus is the mean value. The characteristic ultimate strain is calculated from the characteristic tensile strength divided by the characteristic Young’s modulus.

• Appearance and dimensions: Dry sheets must have a smooth surface without folds or notable waves and no significant breakage of fibre bundles. Length and width are to be agreed between parties; width must be measured with a precision of 1 mm.

• Nominal thickness and mass: Nominal thickness is calculated from the fibre mass per unit area of the dry sheet and the dry sheet density (see Clause 6.2.2 and Annex A). Annex A describes the procedure to determine fibre mass per unit area using square specimens and a precision balance.

• Sampling and testing: Initial testing requires at least 20 test pieces; periodic inspection requires at least five. Tensile tests are to be carried out in accordance with ISO 10406-2. Appearance inspections should use daylight or daylight-type lighting (around 6 500 K). Measurements are normally at room temperature; in disputes, standard conditions per ISO 291 apply (27 °C ± 2 °C, 65 % ± 5 % RH for warm climates).

Applications

ISO 18319:2015 is intended for manufacturers, specifiers, testing laboratories and designers involved in retrofitting and upgrading concrete structures with FRP sheets. Practical uses include:

• Establishing reliable design input values for structural strengthening projects.
• Defining quality control and acceptance criteria during production and on-site inspection.
• Supporting procurement specifications and supplier verification for FRP reinforcement.

Using the standard helps ensure consistent material properties and repeatable test methods across projects, improving safety and predictability of FRP-based repairs and upgrades.

Related Standards

• ISO 10406-2 - FRP reinforcement test methods (FRP sheets)
• ISO 14484 - Performance guidelines for design using FRP materials
• ISO 291 - Standard atmospheres for conditioning and testing
• ISO 5725 - Accuracy (trueness and precision) of measurement methods
• ISO 10548 - Determination of size (referenced for sizing agent content)

For implementation, combine ISO 18319 characteristic-value procedures with the appropriate design code and laboratory methods described in the referenced standards to achieve robust, code-compliant FRP reinforcement solutions.