Prediction and measurement of modal damping factors for viscoelasticspace structures

The procedure outlined in this paper extends the finite element method to viscoelastic space structures; predictions of mode shapes, frequencies, and damping factors can be made based on a new modeling approach that uses specific measured material data. Briefly, the procedure is as follows: 1) the modulus function of the material is measured from free-decay tests of a uniform cantilever beam of the subject material, and 2) these material data are then inserted into the new damped-structure modeling technique. These two steps are illustrated and validated using a strawman space structure fabricated entirely from a single epoxy material. Predicted damping characteristics based on material data and the new modeling technique are compared with modal data obtained for the test structure. Using commercially available software, the modal test data are processed to obtain mode shapes, frequencies, and damping factors. A comparison between predicted eigenvalues and experimentally determined modal frequencies and damping factors indicates that the proposed new technique is a valuable tool in structural analysis.