ABSTRACT
The Iosipescu shear test is one of the methods used most to obtain the shear stress–strain response and shear strength of fibre reinforced composites [1,2]. Technically, in order to determine shear strength, the entire test section of the specimen is required to be in a state of pure and uniform shear stress. This is not possible with flat coupons, such as the Iosipescu specimen, because the shear stress at the free edges must be zero. Therefore, the shear stress cannot be uniform and high shear stress gradients are present. With such shear stress gradients, equilibrium can only exist if normal stress gradients are also present. Hence, the state of stress throughout the entire test section can be neither pure nor uniform. Although it is not possible to create the ideal state of stress in flat coupons, one can create an optimal state of stress that is predominantly uniform shear throughout most of the test section. This can be accomplished by adjusting the notch geometry (angle, notch radius and depth) [3] and the method of load introduction. Since the stress distribution is also strongly dependent on material orthotropy, optimization is required for each material tested.
