Passively Damped Joints for Advanced Space Structures.

Abstract : In the past, damping treatments have been added to structures rather than designed in. This work-progress paper describes the benefits to be gained by designing damping into the joints of large space structures. Also, an analysis of a typical joint is developed and two new non-resonant test techniques are outlined. The joints, as envisioned, are double-lap shear joints that dissipate energy when worked in an axial direction. To better understand the relationship between structural stiffness and structural damping as a function of important physical parameters, a one-dimensional analysis of a typical joint was developed. Two new non-resonant forced vibration test methods (steady state and transient) have been developed that are particularly well suited for obtaining the damping characteristics of joints in large space structure. The advantage of the steady state method is that it does not require measurement of relative displacement. The transient sine-pulse approach frees the specimen from fixture/joint interaction effects. Preliminary damping and stiffness results obtained from the sine-pulse technique are provided for several aluminum test specimens. (Author)