Optimization and actuation of truss structures

Truss structures have been used for many years in a variety of applications. Recently, work has begun to apply truss structures to multi-functional applications. Here an attempt is made to characterize the structural behavior of truss structures for use in these multi-functional designs.; The mechanics of truss core sandwich panels is examined here. Sandwich plates comprised of truss cores faced with either planar trusses or solid sheets are optimally designed for minimum weight, subject to a crushing stress and prescribed combinations of bending and transverse shear loads. Motivated by recent advances in manufacturing possibilities, attention is focused on plates with truss elements and faces made from the same material. The optimized plates are compared with similarly optimized honeycomb core sandwich plates fashioned from the same material. Sandwich plates with solid face sheets and truss cores are highly efficient from a weight standpoint. They are also studied for their performance as compression panels. Optimized compression panels of this construction compare favorably with the most efficient string stiffened plates.; A class of planar, pin jointed truss structures based on the ancient Kagome basket weave pattern with exceptional characteristics for actuation has been identified. Its in-plane stiffness is isotropic and has optimal weight among planar trusses for specified stiffness or strength. The version with welded joints resists plastic yielding and buckling. Numerical results are presented for the energy required to actuate a single member in large two-dimensional lattices. The behavior of the Kagome lattice is shown to be controlled by a combination of stretching and bending through the use of simple models. A plate structure is considered which employs the planar Kagome truss as both actuation plane and structural support. Key aspects of the actuation behavior of this Kagome structures are investigated. The strain energy induced in such structures is shown to be quite small, while the strains induced are moderately large. The actuation behavior is predicted quite well by a long wavelength actuation theory.