Dimensional Repeatability of an Elastically Folded Composite Hinge for Deployed Spacecraft Optics

Abstract

A new type of folded composite hinge is investigated for its use in precision deployable spacecraft structures. The hinge is an integral feature of a composite tube intended for use as a structural truss member. The design of the hinge allows the tube to be elastically folded for stowage even with tube wall thicknesses from 0.4 to 1.7 mm. Whether the large but primarily elastic folding stresses impart permanent deformations to the tube after it is deployed is experimentally assessed. The data show that any such permanent strain induces tip deformations, identi ed as microscopic plastic behavior, of no more than 2.5 ¹ axially and 9 ¹ laterally, depending on the composite layup. This deployment repeatability is comparable to prior measurements of mechanical deployables. Moreover, stow duration and number of stows have no measurable effect, once the initial stow-deploy cycle has been completed. There is always a signi cant viscoelastic creep recovery following deployment that increases with stowage time. However, this viscoelastic creep is recovered. An exponential curve t of the creep time response shows that the time constants of the viscoelastic recovery are independent of stow duration. Nomenclature fag = vector of coef cients, ¹m b = intercept, ¹m k = spring stiffness constant, N/m M = model order m = thermal correlation coef cient, ¹m/ ± C N = number of measurements P = probability S x = sample standard deviation, ¹m t = time, s t º; P = Student's t distribution u x = precision interval, ¹m y = tip displacement, ¹m O y = tip displacement estimate, ¹m 1T = change in temperature, ± C º = degrees of freedom ¾ 2 i = sample variance, ¹m 2 ¿ = time constant, s f¿ g = vector of time constants, s  2 = chi-squared distribution

Overview of the Innovative Space-Based Radar Antenna Technology Program

“…The phased-array feed panels are attached to and deploy along with the main support truss. Each section of phased-array panels is connected by a composite hinge [33]. These composite hinges, also called strain-energy hinges, were also used in the main truss's folding longeron elements.…”

Folding, Stowage, and Deployment of Viscoelastic Tape Springs

“…For example, the initial deployment anomaly of the composite booms forming the antennas of the Mars Express Spacecraft was attributed to the loss of deployment moment after long term stowage [5,6]. Related experimental studies found that the deployed shape precision and vibration characteristics are also aected by time and temperature eects [7,8]. As deployable space structures are stowed for extended periods and subjected to varying temperature environments, viscoelastic eects need to be considered for designing deployable structures with predictable deployment behavior and nal shape precision.…”

Large Strain Four-Point Bending of Thin Unidirectional Composites

“…A number of deployable space structure architectures have been or are currently under development, which employ thin composite laminates [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26], two of which are shown in Fig. 1 [18,19].…”