Abstract: Based on the user subroutine USDFLD and Hashin's criteria, this paper presented a finite element composite stiffened laminates damage model by using ABAQUS software. Six basic damage models such as delamination, matrix crack and matrix compression, fiber fracture and fiber crush may happen when composite stiffened laminates are under static indentation force, the damage evolution of composite stiffened laminates can be simulated by this finite element damage model. Load-displacement curve and dent depth-load curve of composite laminates were predicted by the finite element composite stiffened laminates model. The computed results are in agreement with the corresponding experiment result, which proves the validity of the presented damage model. The pit depth of the composite stiffened laminates at the knee of curve increased obviously. Compared with unstiffened plate, the dent depth of the composite stiffened laminates came to 0.84mm,which was considered as a visible impact damage. The method and results concluded in the paper can be useful for the performance analysis of grid-stiffened composite structure such as the rear pressure bulkhead used in aircraft.

Key words: composite stiffened laminates, static indentation force, dent depth, Hashin's criteria, damage