Johnson M., Batton B., Osman H., Fuller C.

In aerospace systems there are many potential sources of shock such as rocket ignition, fairing separation, explosions, decompression and turbulence. These shocks propagate through the support structures and can damage delicate instrumentation or payloads. This paper looks specifically at controlling shock propagation through struts. Struts also act as bottlenecks in the transmission path between source and receiver and are therefore good places to place vibration control treatments. This paper presents the results of an experimental investigation into the use of Cylindrical Distributed Vibration Absorbers (or CylinDVAs) for controlling shock propagation through cylindrical struts. CylindDVAs are an extension of an existing technology (DVAs) previously demonstrated to be good at controlling vibration and shocks in large plate type structures. The CylinDVAs consist of a soft distributed cylindrical compliant layer made of foam covered with a cylindrical mass layer. The device can be tuned by varying the mass layer, the foam type and foam thickness. It is shown that one benefit of the CylinDVA is that it orients its reaction force (circumferentially) to the orientation of the vibration propagating down the strut and can therefore control both orthogonal bending waves in the strut simultaneously. For this work the CylinDVAs were demonstrated on a strut separating a source and receiver structure made of steel beams. The acceleration on the receiver structure was measured when the source structure was impacted by a hammer with and without the presence of the CylinDVA treatment. The vibration levels and shock spectrum were calculated using this measured data and large reductions were demonstrated.