A novel versatile axisymmetric specimen for mixed-mode I/II characterization of adhesively bonded joints

The characterization of the fracture toughness of adhesive joints under mixed-mode I/II loading conditions is crucial for many real-world applications. Specifically, understanding the behaviour of joints under mixed loads is essential for the development of reliable numerical models. This study presents a novel specimen testing methodology for characterizing mode mixity. Unlike existing methods in the literature, the proposed procedure relies on easily manufacturable axisymmetric specimens and simple testing techniques. Comparisons with existing studies demonstrate that the method can be effectively applied for the characterization of both pure mode I and mode II fracture toughness. These data can then be used to inform a Cohesive Zone Model (CZM) of the joint. Experimental validation shows that the model can accurately predict the joint's behaviour under mixed-mode I/II loading conditions. Thus, this methodology significantly simplifies the testing procedures required to fully characterize an adhesive under generic loading conditions. Moreover, the proposed specimen design can be used on different testing machines for the characterization at different strain rates.