Effect of Stiffener Configuration on Bulkhead Modal Parameters

Optimization of bulkhead stiffener configuration has been an active area of research over the past decade, but no real practical solutions have been generated. This research investigates bulkhead stiffener configuration on a rudimentary level, by analyzing the modal parameters of three different stiffener configurations. Experimental data was used to validate the computational models of two modified bulkhead stiffener configurations. Operational boundary conditions were then applied to the computational models to assess the modal density of the modified bulkheads within the aircraft engine rotational frequency range. Removal of one horizontal stiffener reduced the overall stiffener mass by 12.2% without generating any modes within 4% of the engine rotational frequency. The inconsistencies of natural frequency changes due to stiffener configuration highlights the difficulty with applying generalized optimization approaches without a thorough understanding of the modes of interest. The results of this work suggest that the fundamental analysis performed herein is necessary to generate a complete understanding of the modal parameters of the bulkhead prior to performing in-depth optimization work.