Crashworthy Design and Analysis of Aircraft Structures

Crashworthiness of an aircraft fuselage and its structural components was investigated experimentally and numerically in this study. A finite element model developed previously for simulating the drop test of a 3m long Boeing 737 fuselage section was used to evaluate the effect of the friction coefficient between the fuselage and the ground, and of the aircraft's angle of impact on the dynamic response of the structure. The 3m section model was subsequently expanded to a full-length fuselage model representing a narrow-body transport aircraft in order to simulate realistic crash-landing scenarios on different terrains (i.e., rigid, soil, and water). The results from these studies highlighted the importance of the subfloor structure and its components in the energy absorption process during a crash landing, as well as the need for energy absorbing devices, integrated with the subfloor structure, to mitigate the impact energy.;A comprehensive experimental study was performed to investigate the energy absorbing capabilities of graphite/epoxy members that could serve as stanchions in the subfloor structure of aircraft or rotorcraft. First, tubes of circular cross sections with chamfered-ends, inward-folding and outward-splaying crush-caps, and combined (chamfered-end and crush-cap) failure trigger mechanisms, were investigated. Next, members with open cross-sections (C-channels, angle-stiffeners, and hat-stiffeners) with chamfered-ends and steeple failure trigger mechanisms were investigated. The optimal configuration that resulted in the lowest initial peak load while providing the highest possible specific energy absorption (SEA) was identified.;Finite element models were developed to simulate the crushing behavior of the graphite/epoxy members observed experimentally using two different modeling methodologies. First, an existing single-layer approach was utilized that required careful calibration of key parameter values used in defining the contact/penetration behavior and material failure. This approach predicted the initial failure peak load and the load-crosshead displacement curve but provided no insight into the failure process. Next, a multi-layer modeling methodology was developed by determining the most effective laminate configuration, element size and formulation, contact definitions, time step control, delamination interface, and material model. This approach captured the failure process and predicted the sustained crush load quite accurately. Such modeling could thus support the future design of aircraft stanchions.