Phase field to fracture analysis on engineered cementitious composites under complex stress states

By developing multiple fine cracks before fracture failure, engineered cementitious composites (ECC) exhibit "metal-like" tensile behaviour, overcoming the inherent brittleness of concrete materials. For promoting the applications of ECC in enhancing structural resilience, it calls for a comprehensive understanding on its performance under complex stress states. To this end, a numerical method, based on phase field to ductile fracture, is developed to study the unique failure mechanism of ECC. A novel concept of pseudo plastic strain is proposed to account for the multi-cracking guided ductility of ECC, circumventing the numerical difficulty in describing multiple fine cracks. In addition, the influence of stress state history on the failure process of ECC members is included by degrading the material fracture toughness with a stress-weighted ductile fracture model. The robustness of proposed method is first verified against three laboratory benchmarks under designated stress conditions. ECC beam members of different test setups, to achieve mixed-mode fracture under complex stress states, are then investigated to fully demonstrate the capability of the developed model. This study is poised to pave way for better analysis and design of ECC members for versatile structural uses.