Analytical/experimental studies of integral passive damping in composite isogrid structures

Abstract

Composite isogrid structures are currently in use in a number of aerospace applications where the control of structural vibration response is an important design consideration. In this presentation, a recent investigation of the modal vibration characteristics of composite isogrid structures with embedded viscoelastic damping layers will be summarized. Analysis was done by means of a finite element method implementation of the modal strain energy method, while experiments were done by using an impulse-frequency response technique. Composite isogrid test panels were fabricated by a fast and inexpensive thermoplastic stamping process using two different co-mingled materials: glass/polypropylene and carbon/nylon. The damping materials were embedded at the interface between the ribs and the skin where the shear deformations are greatest in order to significantly improve the damping properties of the structures. It is found that the required amount of damping material can be reduced significantly if it is optimally placed. The modal vibration characteristics of composite isogrid structures are also compared with those of other composite structures such as laminates and sandwich panels. The authors gratefully acknowledge the support of the WSU Institute for Manufacturing Research, as well as donations of materials by Vetrotex America, Cytec Fiberite, and 3M Company.