Morphing composite cylindrical lattices with enhanced bending stiffness

Abstract

A key aspect in the design of deployable space structures comprising slender elements such as booms is their deployed bending stiffness. In space, due to zero gravitational loading, a high level of bending stiffness is not required to support neighbouring structures, but instead is desirable to resist vibrations generated by the attitude control system. The morphing composite cylindrical lattice that is under development is a structure with significant potential for deployable applications in space, however, concepts developed so far may lack sufficient bending stiffness. Therefore, current work focuses on developing a method of increasing the lattice bending stiffness, while minimising any increase in both mass and stowed volume. These goals are achieved by using additional composite strips mounted adjacent and concentric to pre-existing strips. These strips are attached using pre-existing fasteners, thus, only increasing the weight of the structure by the mass of the composite strips. A finite element model of the new lattice configuration is developed and validated by comparison to experimental results. For this comparison, three different lattice configurations were manufactured, two lattices with a conventional strip configuration, an eight-strip lattice and a four-strip lattice, and a third using a new lattice configuration developed in this work. In comparison with the eight-strip lattice, the new lattice configuration is 32% less stiff, however it weights 33% less and stows to approximately half the stowed height. Compared to the four-strip lattice, the new configuration weighs 75% more, but it is 281% stiffer while stowing to the same volume. By increasing the deployed bending stiffness, this work makes the morphing cylindrical lattice a more viable candidate for deployable space structures.