1.1 This International Standard specifies a procedure for determining the in-plane shear stress/shear strain response, including the in-plane shear modulus and shear strength, of fibre-reinforced plastic composites by the ± 45° tension test method. 1.2 The method is suitable for use with thermoset and thermoplastic matrix laminates made from unidirectional layers and/or fabrics including unidirectional fabrics, with the fibres oriented at ± 45° to the specimen axis, where the lay-up is symmetrical and balanced about the specimen mid-plane. NOTE — The method is not suitable for coarse fabrics. 1.3 As the test has been shown to be sensitive to the number and distribution of layers, comparisons should be undertaken using the same number of layers, which must be well distributed.