Composite Tube Hinges

This paper is concerned with self-powered, self-latching tube hinges, made by cutting three parallel slots in a thin-walled carbon fiber reinforced plastic tube with a circular cross section. Thus, a hinge consists of two short tubes connected by three transversally curved strips of material (known as tape springs). A particular tube hinge design is considered, with a diameter of about one-third that of the hinges used previously; this requires the tape springs to reach strains close to failure when the hinge is folded. Three analyses of the peak strains in a tube hinge are presented. The first analysis obtains general analytical expressions for the longitudinal fold radius of a tape spring and the associated peak fiber strains. The second analysis is a finite-element simulation of the folding of a single tape spring and the third analysis is a simulation of a complete tube hinge. It is found that the largest fiber strains in one- and two-ply hinges can be predicted analytically with very good accuracy. It is also found that the contact and interaction between the three tape springs that form a tube hinge, modeled in the third analysis, do not affect the peak strains significantly.