Hybrid Structural/Energy Absorbing Sandwich Panel

Pepin Associates, Inc. developed this hybrid panel for turbine engine fragment containment applications. It can also be tailored for use as armor. The panel or ring design is a sandwich panel with a dry, unimpregnated ballistic fabric core penetrated by rigid rods which connect structural facesheets. We have fabricated the panel with titanium, aluminum, or graphite/epoxy facesheets with a dry ballistic fabric core of Kevlar® or Zylon®. It is a lightweight, low volume sandwich structure which is also a shield to high velocity fragments. The sandwich structure tends to be very damage tolerant since each rod-to-facesheet joint is autonomous. It is also very stiff in bending to reduce large deformations during fragment impact. This concept is patented and was developed with funding from the FAA Tech Center.

Pepin Associates, Inc. has performed blade impact tests, 20 spin tests, and a full scale engine test on the hybrid panel. Blade impact tests show that the through thickness rods in the sandwich panel core enhance the ballistic performance of the fabric alone. Also, as sharp fragments impact the facesheet, the facesheet material tends to envelop the sharp fragments and protect the fabric from being cut by the fragment edges.

Spin testing used a T-53 second stage power turbine whose disk was modified to fail in a tri-hub disk burst mode. The rotational speed at burst was 20,000 rpm and the energy at burst was 113,000 joules (1,000,000 in-lbs). The hybrid ring design contained the T-53 tri-hub disk burst with a ring weighing 5 kg (11 lbs). This ring was a Kevlar fabric core design with carbon rods through its thickness. A high speed video of one of the spin tests is shown in this area of our web site.

In addition, a full scale test was performed on a T-53 engine. Again, the rotor was modified to fail at 20,000 rpm and the engine was run up until the rotor failed in the tri-hub disk burst mode. A hybrid titanium/Kevlar containment ring was installed on the engine and this ring successfully contained the failure and trapped the disk fragments inside the engine.

(references : FAA report at www.tc.faa.gov/its/worldpac/techrpt/ar99-6.pdf -- also AIAA 93-1816)

Hybrid Titanium/Kevlar Containment Ring Mounted

On A T-53 Engine

Before Rotor Burst Test

Hybrid Titanium/Kevlar Containment Ring Shown After Containing A Tri-Hub Burst Of The Second Stage Power Turbine Of The T-53 Engine.