What kind of crack are you working? surface crack or through thickness crack ? In my old day using abaqus, I modelled the quarter of geometry to model the central crack. Be careful about the singularity of the crack tip. I moved the nodes around the crack tip by 1/4 from the crack tip. I need to re-define the coordinate of these nodes. I am not sure CAE can do something more easlier now. For 2-D plate, you can use 2-D shell plane stress or plane strain elements.