ASTM D4255 is a test method for testing the in-plane shear properties of high-modulus fiber-reinforced composite materials. The method is divided into two procedures. Procedure A tests laminates clamped between two pairs of loading rails. When loaded in tension the rails introduce shear forces in the specimen. In Procedure B, laminates clamped on opposite edges with a tensile or compressive force applied to a third pair of rails in the center are tested. 

Properties that may be measured by this test method include:

 In-plane shear stress versus engineering shear strain response,

 In-plane shear chord modulus of elasticity,

 Offset shear stress, and Maximum in-plane shear stress. 

In cases in which the engineering shear strain at failure is greater than 5 %, the shear stress corresponding to 5 % engineering shear strain should be reported.