Simulation of crack growth in adhesively bonded joints via cohesive zone models

Adhesively bonded joints have shown great advantages in the aerospace industry when compared with traditional mechanical fastening methods. These type of joints allow to reduce the overall structural weight, improve the fatigue life characteristics due to reduction of stress concentrations (uniform stress distribution), smooth external finish, sealed surfaces, and many others. One of the main concerns with these joints is their characterization under fatigue loading, i.e. a comprehensive study of crack growth which will allow the development of standardized tests and certification in the aerospace sector. Thus, the aim of this thesis is the development of user-defined subroutines implemented in finite element analysis commercial software, i.e. Abaqus, via Cohesive Zone Models for the study of crack growth in adhesively bonded joints under quasi-static and fatigue loading. Hence, a material user-defined subroutine (UMAT) was developed using cohesive zone models taken from literature and implemented in Abaqus to study disbonding under quasi-static and fatigue loading in 2D specimens. The studied specimens were a double cantilever beam (DCB), for pure mode I opening; and a crack shear lap (CLS), for mixed mode opening. Results of the simulations were compared with experimental data from work done previously by different authors. The data from the simulations showed the same behavior as the experimental data, thus validating the developed user-defined subroutines. For future work, it is recommended to implement the user-defined subroutine into 3D models, and again compare it with experimental data to validate it.