A short-beam shear fracture approach to measure the mode II fracture toughness of materials with preferred interfaces

A short-beam shear fracture approach is developed to characterize the mode II fracture toughness, (K _IIC) of materials with preferred interfaces such as wood, fiber composite materials and bonded materials. This approach is easy to implement using the Iosipescu shear fixture and is free of friction between the cracked faces thereby offering a more reasonable value of K _IIC than previous methods. Another feature of our new approach is the measurement of accurate crack initiation load due to a clear load drop. Additionally, calibration charts for bonded polymers and composite materials are generated. Finite element analysis along with cohesive elements is used to validate experimental load-displacement curves which are obtained by testing bonded polymers. This new approach is compared with the four-point bending fracture experiment, and the measured fracture toughnessess of the same bonded materials of two kinds of approaches are shown to be close (15–25% difference).