ISO 20975-1:2023

This document specifies methods for determining the through-thickness properties (i.e. strength, modulus of elasticity, Poisson’s ratio and strain-to-failure) of fibre-reinforced plastic composites using either rectangular prism and/or waisted block specimens. The methods are suitable for use with a variety of aligned and non-aligned, continuous, and discontinuous fibre formats, with both thermoset and thermoplastic matrices, ranging from 20 mm to 40 mm in thickness. Three specimen types are described in this document. These are: —    Type I - fixed rectangular cross-section along length of specimen. It is the preferred specimen for determining elastic properties. —    Type II - waisted rectangular cross-section, variable cross-section along length of specimen. It is only suitable for determining tensile strength values and is the preferred specimen for highly anisotropic and thermoplastic materials. —    Type III - waisted rectangular cross-section, fixed cross-section along the gauge-length of specimen. It is used to provide both elastic and strength property data and is the preferred specimen for generating a full stress-strain response. Specimen types I and II are also suitable for use with unreinforced plastics but are unsuitable for use with rigid cellular materials and sandwich structures containing cellular materials. Two testing modes are covered: —    Method A – Tension —    Method B – Compression