<title>Deployable structures using bistable reeled composites</title>

Abstract

This paper describes an innovative, patented use of composite materials developed by RolaTube Technology Ltd. to make smart deployable structures. Bi-stable reeled composites (BRCs) can alternate between two stable forms; that of a strong, rigid structure and that of a compact coil of flat-wound material. Bi-stability arises as a result of the manipulation of Poisson's ratio and isotropy in the various layers of the material. BRCs are made of fiber-reinforced composite materials, most often with a thermoplastic matrix. A range of fibers and polymer matrices can be used according to the requirements of the operating environment.Samples of a BRC structure were constructed using layers of unidirectional, fiber-reinforced thermoplastic sheet with the layers at different angles. The whole assembly was then consolidated under conditions of elevated temperature and pressure. The properties of the BRC are described and the results of a series of experiments performed on the samples to determine the tensile strength of the BRC structure are reported.A full analysis using finite element methods is being undertaken in collaboration with the University of Cambridge, England. The first commercial use has been to fabricate boom and drive mechanisms for the remote inspection of industrial plant.

Natural frequency optimization of braided bistable carbon/epoxy tubes: Analysis of braid angles and stacking sequences

“…High tensile elastic (ρ = 1000 kg/m 3 , E = 20 GPa, ν = 0.3) cord links with a radius of 1 mm connect the strips to the BRCs. These are used to prevent rotation of the BRCs with respect to the strips in the deployed solar array FE model [5]. The blanket is not included in this FE analysis because it would obscure the modes of interest by introducing many extremely low frequency modes generated by the soft flexible blanket substrate material.…”

“…A deployable "roll-up" solar array with no PV membrane is also modeled in ABAQUS for the purpose of validating the feasibility of analyzing one single BRC tube instead of the whole solar array structure. The natural frequencies of several BRC tubes with various dimensions, constraints and stacking sequences are optimized with respect to (a) Deployable "roll-up" PV solar array developed for DeployTech [5] BRC tube Cross-link strip Cord linkage …”

Modeling the Bistability of Laminated Composite Toroidal Slit Tubes

“…BRCs are open-section tubular structures that can be rolled up and extended, analogous to tape measures, but are stable in both configurations without the need of support structures. Bistability arises due to the arrangement of fibers in each ply 2 through an antisymmetric lay-up scheme with respect to the mid-plane which results in a preferential direction for bending to occur 3 and theoretically may be exhibited using any material of high Poisson ratio and sufficient stiffness 4 .…”

“…Progressing to a shell model 10 enabled the study of edge effects and an inextensional bending model 11 utilized a property of developable surfaces -the Gaussian curvature 12 remains zero everywhere -to predict coiled radius by modeling deformation of a plate superimposed upon the surface of a great cylinder. In this paper, we begin investigating the doubly curved torus-BRC as illustrated in Figure 1 which until now has only been briefly discussed 4 .…”

Curved Bistable Composite Slit Tubes with Positive Gaussian Curvature

“…Bistability in neatly coiling slit tubes may be engineered by the arrangement of fibers in each ply with respect to the deployment direction through an antisymmetric lay-up scheme. Theoretically, bistability may be achieved using any material of sufficiently high Poisson ratio and stiffness [1].…”