Team 37: Titanium firewall repair Sponsored by Sikorsky Sponsor Advisor: Mike Urban Faculty Advisor Prof. Kazem Kazerounian, Kevin Bombero, Michael Gwara and Mateusz Zyla
In Sikorsky helicopters, Titanium firewalls act as thermal barriers. They shield the aircraft from the heat generated by the engine components and also buy time for a pilot to land in the event of a catastrophic engine failure. Currently, firewalls are constructed from sheets of titanium that are riveted together into the desired arrangement, however, each rivet hole can be a potential crack propagation site. To repair damage to the firewall from either cracks or foreign object damage, the affected area must be removed and reinforced. Sheets of thicker titanium are riveted over the damaged section, but the added rivets create additional sites for possible crack formation. Each time a riveted repair is performed, the strength of the firewall decreases and the weight of the aircraft increases. Therefore it would be advantageous if that the repair process could be improved. Laser beam welding is one solution with promising results. In a 2010-2011 MSE capstone project students proved the feasibility of laser welding commercially pure titanium. This year the project focuses on proving the mechanics of laser beam welding as well as devising a possible patch solution that could be used on Sikorsky rotorcraft. Since testing entire firewalls is not feasible, it was decided to use small coupons of uniform size to compare welds to rivets. The project focuses on testing on the static strength of riveted and welded titanium lap joint specimens. Many tests have been performed and compared to specimens of similar sized titanium. As validation to all tests, a limited number of tests of fatigue strength as well as a number of finite element analyses were performed. The results were fairly uniform showing that the laser weld repair exceeds the strength of riveting. Senior Design Project Program 2011-2012
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