DESIGN AND NUMERICAL VALIDATION OF A LATTICE FUSELAGE STRUCTURE CONCEPT
This paper reports on results of a conceptual design phase of a collaborative research programme (EU-ALaSCA) aimed at the development of manufacture-optimized lattice fuselage structures satisfying fundamental requirements of airworthiness.
An alternative fuselage structure design concept was developed for a single aisle, short and mid-range aircraft. The primary structure consists of inner and outer helical stringers with small angle to the axial direction, forming a grid arrangement, and a load bearing skin. The sizing was performed on the two cross-sections at the end frames of the barrel section. The main design drivers were identified, using loads and load distributions from global aircraft configuration analysis, and the structural members were optimized with analytical methods to meet stiffness, strength, and global and local stability requirements.
The resulting design was numerically validated using FE analysis. The transition between the two cross-sections was achieved with a so-called stringer run-out concept that prescribes how the stringer number changes when progressing from one end of the fuselage to the other. The presence of the sharp angled skin bays and stringer profile shapes motivated the comparison of several FE methodologies w.r.t. robustness and accuracy. A highly detailed, shell-only methodogy was chosen, refined, and applied to buckling analyses of the aircraft fuselage and to post-buckling analyses of fuselage panels.
The predicted buckling strengths and stress levels of the global analyses were consistent with the results of the analytical sizing process. The local analyses gave an insight into the stability behavior of such anisogrid panels and the design improvement.