Topology optimization of a pre-stiffened aircraft bulkhead

The bulkhead of an aft-fuselage twin-engine mounted aircraft is a pivotal structural component from a noise and vibrations perspective as it is the main transmission path for the engine-induced vibration to propagate into the passenger cabin. Despite this, there has yet to be a successful implementation of topology optimization (TO) on a pre-stiffened aircraft bulkhead. This work is the first to investigate TO on a pre-stiffened bulkhead with a frequency-based problem statement. The objective function was set to maximize the first eigenfrequency to maximize the stiffness to mass ratio of the bulkhead. Frequency constraints were implemented to eliminate the natural frequencies within range of the engine excitation frequency. A volume fraction constraint was set such that the mass of the solution was less than the mass of similar bulkhead stiffeners reported in the literature. The first successful implementation of topology optimization on a pre-stiffened aircraft bulkhead was obtained. Two designs satisfying the optimality criterion were generated, both of which were able to improve bulkhead structural integrity, reduce mass, and eliminate resonance from ± 10% of the engine excitation frequency. This work demonstrates that TO is a useful tool to help aerospace engineers improve the vibro-acoustic properties of the bulkhead without sacrificing mass or structural integrity. The methodology introduced in this work can be easily integrated into aircraft design, as it uses tools widely available in the aerospace industry.