Launch Vibration of Pre-Tensioned Coiled Structures

Relative movement between slipping layers in a coil due to vibration can cause defects in the structure or damage functional elements, such as photovoltaic cells, attached to the structure. Radial contact pressure between successive layers due to coiling pre-tension provides a frictional force that can be used to resist inter-layer slip. In this study, we propose a stress-field based, analytical friction model to use as a criterion for estimating the frictional shear capacity of a wound roll prior to the onset of slip. Because the radial pressure varies with radial position in the coil, the shear capacity against slippage also varies with position. This analytical shear capacity can then be compared against the shear resultants obtained in finite-element simulations of coiled structures undergoing vibration load. Rather than modeling discrete windings of wound rolls, the starting coiled-stiff assumption is the coil is tensioned sufficiently to behave as a solid. Thus, a finite-element vibration study of a homogenized solid is used to find the loads and locations where shear resultant is larger than the estimated shear capacity, indicating slip. The validity of the coiled-stiff assumption is experimentally verified using a vibration experiment that measures the variation in apparent stiffness of a coiled membrane wound under varying tensions.