A Method of Selecting and Configuring Optimal energy Absorbing Cargo Restraint Systems to Improve Crashworthiness

Open Access
Kong, William
Graduate Program:
Aerospace Engineering
Master of Science
Document Type:
Master Thesis
Date of Defense:
Committee Members:
  • Edward C Smith, Thesis Advisor
  • Edward Smith, Thesis Advisor
  • Michael Andrew Yukish, Thesis Advisor
  • multi-objective optimization
  • cargo restraints
  • crashworthiness
  • cargo dynamics
  • crash simulation
  • energy absorbers
This thesis describes the development of methods and tools to design optimal energy absorbing cargo restraint systems to improve crashworthiness, and demonstrates them in a sample design study. The energy absorbing cargo restraint systems considered have two components: load limiter and lanyard. The load limiter acts as the energy absorbing device of the restraint system. A closed-form solution does not exist due to the changing geometry of the configuration during a crash and the nonlinear behavior of the restraints. Therefore, a cargo dynamics simulation (CDS) was developed to analyze the interaction between the cabin floor, cargo, and restraint system in a crash event. The simulation solves a system of state-variable equation for six degree-of-freedom rigid body dynamics. An optimization method was developed in which the cargo dynamics simulation is coupled with Applied Research Laboratory Trade Space Visualizer (ATSV) — a multi-dimensional data exploration and visualization software — to exercise the simulation over the design space and visualize the results. A comparative study was conducted to compare restraint system components and the results from static and dynamic analysis. A parametric study was conducted to provide a rule-of-thumb for tie-down angles that would optimize the design of simple restraint configurations. Design studies are presented as exercises of the optimization method for a generic cargo handling scenario. The crash loads and parameters for the analytical studies were obtained from U.S. Department of Defense specifications as provided in the Aircraft Crash Survival Design Guide and MIL-STD-1290. The results of the comparative and optimization studies revealed the importance of lanyard characteristics in restraint system performance. The ideal lanyard was found to exhibit high stiffness, high strength, low weight, and low elongation. The allowable cargo displacement constraint proved to be the most influential factor in optimal restraint system design. Within the confined space of the aircraft, centimeters of displacement can be the difference between a survivable and fatal crash. Finally, a new set of requirements and design criteria are proposed to address normal flight maneuvering conditions, crash conditions, and usability. The requirements were created to provide guidance to cargo handlers for using energy absorbing cargo restraint systems.