Molding process influence on pull-off performance of composite stiffened panels

Two types of molding process of composite stiffened panels which are co-curing and secondary-bonding are investigated, and pull-off experiment was designed to obtain the load-carrying capability and failure modes. The results show that the main failure mode of the secondary-bonded composite stiffened panels is adhesive debonding between the skin and stiffener. The failure mode of co-cured stiffened panels is complex, which includes skin-stiffener debonding, fiber damage, delamination and so on. The performances of the co-cured stiffened panels are better than that of secondary-bonded stiffened panels. The debonding initiation and propagation were simulated by using the nonlinear finite element method. Using user subroutine and cohesive interface, Hashin and B-K failure criterion were applied to simulate co-cured stiffened panels and secondary-bonded stiffened panels respectively, and the simulation results agreed well with experimental results.