Comparison of FEM and SPH for Modeling a Crushable Foam Aircraft Arrestor Bed

Passenger aircraft can overrun the available runway area during takeoff and landing, creating accidents involving aircraft damage and loss of life. Crushable foam arrestor bed systems are often placed at runway ends to mitigate such overruns. As the aircraft tires roll through the bed, the material compaction dissipates energy, bringing the aircraft to a controlled stop. A detailed two-year analysis was conducted for the TRB Airport Cooperative Research Program to develop improved arresting systems (Barsotti, et al., 2009). A major thrust of the effort was the development of validated numerical models for crushable arrestor bed materials and deformable aircraft tires. Finite element models for the crushable material manifested several problems due to the unusual mode of deformation experienced, which included significant element skewing, heavy compaction (~90%), and high hourglass energies (~19%). Many meshing and hourglass mitigation strategies were attempted, but they produced only marginal improvement. The Smoothed Particle Hydrodynamics (SPH) method was adopted as a replacement, and detailed performance comparisons of the FEM and SPH versions were made. Error convergence studies using mesh refinement were performed for 1-D, 2-D, and 3-D cases, culminating in the comparison of full tire & arrestor models for each formulation.