Assessment of failure mechanism of double-strap 3D-FML adhesively bonded joints under tensile and compressive loadings using cohesive zone modelling approach

Despite the widespread applications of Fiber Metal Laminates (FMLs), there is a clear lack of information regarding the performance of bonded joints mating 2D-FMLs and the recently-developed 3D-FMLs, particularly when considering their performances under compressive loading. Therefore, as a follow-up to the authors' recent investigations, an extensive series of numerical analyses are conducted in the present study to simulate the tensile and compressive (i.e., buckling, and post-buckling) responses of double-strap adhesively bonded joints mating 3D-FMLs. The 3D-FMLs are joined using carbon fiber-reinforced plastic (CFRP) straps and structural epoxy resin. The damage initiation and evolution in the bonded regions are modelled by seven different FE models, which incorporated the mixed-mode trapezoidal Cohesive Zone Modelling (CZM) approach in conjunction with continuum elements. Firstly, the effects of different numbers of CZM layers and thicknesses on simulating the damage mechanism are investigated. Subsequently, the influence of CFRP straps' thickness and length on the performance of the adhesive joints is parametrically studied. The distributions of peel and shear stresses along the length of the bonded regions are also systematically explored. Based on the results, the optimal joint configuration is established, and the most effective modelling framework is highlighted by comparing numerically predicted results against experimental results.