16 June 1998 Analysis, design, and testing of two cocured damped composite torsion shafts
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Abstract
Cocuring layers of viscoelastic damping materials with composite material systems offers the possibility of manufacturing light-weight, stiff, highly damped structural components. The objective of this work was to design two cocured damped composite torsion shafts. The first shaft uses the extension-twist coupling mechanism of off-angle composite materials to enhance the damping performance of a damping material. The inner shell contains plies oriented at a positive ply angle in the first half of the shaft length and plies oriented at a negative ply angle in the second half. Due to the extension-twist coupling, the shell center section moves axially when the shaft undergoes torsion deformation. The outer shell plies are oriented in the opposite manner so that the outer shell center moves in the opposite direction. The relative axial deformation between the two shells places the damping material into shear, providing damping. The second shaft uses a constraining layer embedded inside the shaft that floats between two layers of damping material. The constraining layer resists torsion deformations applied to the shaft. Load transferred to the constraining layer through the damping material places the damping material into shear, again providing damping. Finite element analysis was used to determine optimal damping material shear modulus and ply orientation to maximize shaft imaginary stiffness. Four shafts total (two of each type) were built and modal tests were performed. Torsion damping increased by factors from 5.8 to 20.0 and 6.1 to 10.9 over the undamped case for the extension- twist and floating constraining layer dampers, respectively. While both damping concepts provide significant levels of damping, the performance of each was hindered due to the increase in shear modulus of the damping material as it was cocured with the composite material.
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Kevin L. Napolitano, Wilder Grippo, John B. Kosmatka, Conor D. Johnson, "Analysis, design, and testing of two cocured damped composite torsion shafts", Proc. SPIE 3327, Smart Structures and Materials 1998: Passive Damping and Isolation, (16 June 1998); doi: 10.1117/12.310716; https://doi.org/10.1117/12.310716
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