Drop Test into Water and Wave Impact Simulations of a Novel 7-Meter Plastic Boat with LS-DYNA

The US Congress, in its desire for a safer boat for the US Navy, contracted Stanley Widmer Associates Inc. to design and build a novel rotationally molded 7-meter boat using a patented "kiss-off" design. A first ever made prototype will be ready for trial in 2010. The material used for most of the boat, high density cross linked polyethylene, and the double hull with “kiss-off” design should, among other advantages, increase the boat's impact resistance compared to fiberglass and aluminum boats. This paper presents numerical fluid structure interaction simulations done on the 7-meter boat, utilizing LS-DYNA, in order to investigate its structural integrity under water impact. Drop test into water simulations were done in the first phase of this numerical investigation. The boat was dropped at different heights and angles. A modal analysis was also done in Phase 1. A procedure to generate realistic waves was developed in the second phase. Explicit simulations with the boat going through waves at different velocities were done. A similar fiberglass boat was finally compared to the plastic design. Results from the drop test simulations and the modal analysis in Phase 1 clearly showed a critical flexural area. A modified design was run in Phase 2. LS-DYNA analysis results from Phase 2 predict that the plastic boat can go through 3-foot waves at 40 knots without damage while the fiberglass one has predicted damage at 30 knots. Overall, the numerical simulations show that high density cross linked polyethylene could be the new age of boating material.