A programmable origami-inspired space deployable structure with curved surfaces

Shape memory polymers (SMPs) are a new type of smart material, they perform large reversible deformation with a certain external stimulus (e.g., heat and electricity). The properties (e.g., stiffness, strength and other mechanically static or quasi-static load-bearing capacity) are primarily considered for conventional resin-based composite materials which are mainly used for structural materials. By contrast, the mechanical actuating performance with finite deformation is considered for the shape memory polymers and their composites which can be used for both structural materials and functional materials. For shape memory polymers and their composites, the performance of active deformation is expected to further promote the development in smart active deformation structures, such as deployable space structures and morphing wing aircraft. The shape memory polymer composites (SMPCs) are also one type of High Strain Composite (HSC). The space deployable structures based on carbon fiber reinforced shape memory polymer composites (SMPCs) show great prospects. Considering the problems that SMPCs are difficult to meet the practical applications in space deployable structures in the recent ten years, this paper aims to research the mechanics of deformation, and failure of SMPCs. In the overall view of the shape memory polymer material’s nonlinearity (nonlinearity and stress softening in the process of pre-deformation and recovery, relaxation in storage process, irreversible deformation), by the multiple verifications among theory, finite element and experiments, one obtains the deformation and mechanism for the process of “pre-deformation, energy storage and actuation and its non-fracture constraint domain. Then, the parameters of SMPCs will be optimized. Theoretical analysis is realized by the strain energy function, additionally considering the interaction strain energy between the fiber and the matrix. For the common resin-based or soft-material-based composites under pure bending deformation, we expect to uniformly explain the whole process of buckling occurrence, evolution and finally failure, especially for the early evolution characteristics of fiber microbuckling inside the microstructures. The research results are meaningful for the practical applications for SMPC deployable structures in space. Considering the deformation mechanisms of SMPCs, the local post-microbuckling is required for the unidirectional fiber reinforced composite materials, at the conditions of its large geometrical deflection. The cross section of SMPC is divided into three areas: non-buckling stretching area, non-buckling compressive area, and buckling compressive area. Three variables are considered: critical buckling position, and neutral plane, the fiber buckling half-wavelength. Considering the condition of the small strain and large displacement, the strain energy expression of the SMP/fiber system was derived, which contains two types, e.g., strain energy of SMP and fiber. According to the minimum energy principle, the expression for all key parameters were derived, including the critical buckling curvature, neutral plane position, the buckling half-wavelength, fiber buckling amplitude, and strain.

Elastic Memory Composite (EMC) materials exhibit many favorable qualities for deployable space structures and have piqued a broad interest within America's deployable space structures industry. EMC materials are similar to traditional fiber-reinforced composites except for the use of a thermoset shape memory resin that enables EMC materials to achieve much higher failure strains than traditional composites when exercised through a very specific thermomechanical load cycle. This unique behavior is exploited in the development of EMC structural components that exhibit very high packaging-strain capability while guaranteeing predictable postdeployment structural performance. This paper presents a review of the current state of development of EMC technologies and EMC deployable space structure components. The paper is intended primarily to help potential users of EMC materials develop a better understanding of the special capabilities of EMC materials and considerations that must be applied while engineering with EMC materials.

Thin-walled structures utilizing the release of stored strain energy for self-deployment have gained popularity in deployable space structures. However, the integration of traditional rigid or bulky sensors to monitor their mechanical behavior presents challenges due to large local deformations and strains involved in folding and deployment. Here we introduce a concept of structural electronic skin (e-skin) that is soft, lightweight, and designed for sensing the folding and deployment of tape-spring hinges. The e-skin demonstrates the capability to accommodate significant hinge deformation and enables multimodal sensing, including strain measurements, motion sensing, and dynamics monitoring. The research showcases a promising approach that leverages the design and manufacturing of soft electronics to fulfill the requirements of thin, lightweight, and soft functional devices for multifunctionality in deployable space structures.

Deployable space structure control using adaptive predictive controller with notch filter

Shape-memory polymers have attracted great interest in recent years for application in reconfigurable structures (for instance morphing aircraft, micro air vehicles, and deployable space structures). However, before such applications can be attempted, the mechanical behavior of the shape-memory polymers must be thoroughly understood. The present study represents an assessment of viscous effects during multiple shape-memory cycles of Veriflex-E, an epoxy-based, thermally triggered shape-memory polymer resin. The experimental program is designed to explore the influence of multiple thermomechanical cycles on the shape-memory performance of Veriflex-E. The effects of the deformation rate and hold times at elevated temperature on the shape-memory behavior are also investigated.

In contrast to conventional structures, deployable structures do not have a fixed geometry and can be transformed between fully expanded and contracted. When folded, they are smaller than traditional fixed structures and can be easily stored and transported. Due to its changeable dimension, the deployable structure has been widely studied in many fields. This research lists the representative applications of deployable structures in three major fields, including aerospace, medical and construction, and analyses the characteristics of each. It is argued that deployable structures are used in several fields currently, however, the various types are not closely related so far, and some of them have not been studied in depth. It leads to the fact that most of the current designs for deployable structures are limited to focusing on specific types. Based on the usage requirements of different industries, the deployable structures often need to be redesigned, thus limiting the promotion of deployable structures in the future. It is believed that categorizing deployable structures according to the scope of application of each type and designing several generalized structural templates for conventional structural shapes will greatly facilitate the utility of deployable structures in various fields.

Elastic memory composite (EMC) materials exhibit many favorable qualities for deployable structures and have piqued a broad interest within America's deployable space structures industry. EMC materials are similar to traditional fiber-reinforced composites except for the use of a thermoset shape memory resin that enables much higher packaging strains than traditional composites without damage to the fibers or the resin. This unique capability is being exploited in the development of very efficient EMC structural components for deployable spacecraft systems. The present paper is intended primarily to help deployable system designers develop a better understanding of the special capabilities of EMC materials, and the unique considerations that must be applied when engineering structural components with these materials. Specifically, the paper discusses: 1) the impacts of incorporating EMC materials on deployable system design, 2) analyses for packaging strain, deployment time, and deployment energy; and 3) requirements and concepts for heating systems.

Various test methods have previously been adopted to test large deployable space structures. However, traditional methods are not applicable to a precise evaluation of three-dimensional deployment characteristics with quasistatic deployment motions. This paper describes the design and performance of a deployment test system using magnetically suspended sliders. The sliders support the deployable structure vertically, and each of them moves freely with negligible friction under the horizontal surface of a ceiling plate. All the sliders control the tension of their vertical cables independently using the feedback signals of the tension sensor to compensate for the gravity of the deployable structure. The test system using magnetically suspended sliders enables maximum drag with a horizontal motion of less than 0.25N and tension control precision from a suspension cable of within 0.25N. The adequacy of this test system is confirmed by a deployment test using a 7m test model.

Finite element modeling of flexible articulated systems has been one of the major development axes at the Aerospace Laboratory of the University of Liege (Belgium) since 1985. The resulting MECANO software [16] (integrated in the larger finite element package SAMCEF) has already demonstrated its powerfulness to simulate motion and dynamics of complex mechanical systems of various natures such as landing gears, energy release springs, gear box transmissions, missile ejection systems, vehicle suspensions, ski bindings, deployable space structures, etc ...

This thesis presents a new approach to modeling in finite element analysis (FEA) creased thin-film sheets such as those used for drag sails, as well as modeling the packaging behavior of coilable deployable booms. This is highly advantageous because these deployable space structures are challenging to test on the ground due to their lightweight nature and the effects of gravity and air resistance. Such structures are utilized in the space industry due to their low mass and ability to be packaged into a small volume during their launch into space. It is shown that removing the crease bending stiffness in creased sheets still allows the deployment behavior of a benchmark problem to be captured, including deployment forces and equilibrium configurations. In addition, folding creased sheets from a flat state into a packaged configuration can result in crease crumpling and excessive wrinkling. To avoid this the Momentless Crease Force Folding (MCFF) technique is developed. Further presented is the behavior of tape springs and Tubular Rollable and Coilable (TRAC) booms when coiled to radii greater than their natural bend radius. Under these conditions the booms can form multiple localized folds which may jam during boom deployment. Understanding this behavior is important for extending the use of these booms to large scale space structures such as orbital solar power stations. A useful analytical model is developed determining when the localized folds in a tape spring will bifurcate and is verified against simulation results. Additionally, a numerical model of the wrapping an isotropic tape spring around a hub with a radius greater than the localized fold radii is validated against physical experiments. This model is used to predict trends in the force required to fully wrap a tape spring around a given hub radii. Finally, when examining the coiling and uncoiling behavior of TRAC booms it was found that the tension force required to keep a TRAC boom tightly coiled is significantly less than the force required to initially coil the boom.

A new deployable mast for realization of large, deployable space structures such as antennas of high arperture, long instrument booms, large solar arrays or solar sails has been developed at the DLR. The triangular truss is based on the use of longerons of composite tapes and shows a signicant increase in mass eciency compared to existing deployable mast concepts. The longerons of thin carbon bre tapes enable realization of large cross-sectional dimensions which leads to a strong insensitivity of critical compression load towards element length. Thereby, in comparison to trusses with longerons of solid rods - the most commonly used type of longerons - higher truss bay length and radius can be achieved for a lower amount of structural mass. This directly contributes to bending stiness and strength. The folding mechanism makes use of the high deformation capability of longerons of tapes in attened state. It is based on a two path folding pattern where the truss is attened rst in cross-direction and reeled up afterwards. This is enabled by the combined use of exible longerons and hinges added to one batten row and ensures high volume eciency. This is especially true for very long masts as the stowage volume mainly depends on the intial reeling radius.

This chapter provides a general description of a variational graph-theoretic formulation for simulation of flexible multibody systems (FMS) which includes a brief review of linear graph principles required to formulate this algorithm. The system is represented by a linear graph, in which nodes represent reference frames on flexible bodies, and edges represent components that connect these frames. To generate the equations of motion with elastic deformations, the flexible bodies are discretized using two types of finite elements. The first is a 2 node 3-D beam element based on Mindlin kinematics with quadratic rotation. This element is used to discretize unidirectional bodies such as links of flexible systems. The second, consists of a triangular thin shell element based on the discrete Kirchhoff criterion and can be used to discretize bidirectional bodies such as high speed lightweight manipulators, deployable space structures and micro-nano electro-mechanical systems (MEMS).

Mechanically bendable and flexible functionalities are urgently required for next‐generation battery systems that will be included in soft and wearable electronics, active sportswear, and origami‐based deployable space structures. However, it is very difficult to synthesize anode and cathode electrodes that have high energy density and structural reliability under large bending deformation. Here, vanadium oxide (V2O5) and nickel cobalt oxide (NiCo2O4) nanowire‐carbon fabric electrodes for highly flexible and bendable lithium ion batteries are reported. The vanadium oxide and nickel cobalt oxide nanowires were directly grown on plasma‐treated carbon fabric and were used as cathode and anode electrodes in a full cell lithium ion battery. Most importantly, a pre‐lithiation process was added to the nickel cobalt oxide nanowire anode to facilitate the construction of a full cell using symmetrically‐architectured nanowire‐carbon fabric electrodes. The highly bendable full cell based on poly(ethylene oxide) polymer electrolyte and room temperature ionic liquid shows high energy density of 364.2 Wh kg−1 at power density of 240 W kg−1, without significant performance degradation even under large bending deformations. These results show that vanadium oxide and lithiated nickel cobalt oxide nanowire‐carbon fabrics are a good combination for binder‐free electrodes in highly flexible lithium‐ion batteries.

This paper describes a computer-aided method for detecting and characterizing unforced, small amplitude, motion in deployable space structures. Because these motions occur infrequently and may involve high frequencies, large data sets must be collected. Manual data analysis methods become impractical because of the amount of data involved, so automation is necessary. An automated technique for detecting signal characteristics representative of micro-dynamic events is developed in this paper. Correlation of responses from various sensors determines if external disturbances are associated with identified event signal characteristics. The structure from which data were collected and analyzed is the Precision Deployable Optical Structure (PDOS). Two types of events, microlurches and micro-dips were identified. Some correlation was observed between micro-dips and the acoustic environment, but none between micro-lurches and the acoustic environment. The observed micro-dips probably are artifacts of the PDOS gravity off-load system. The automated techniques will be modified to work as part of a real-time monitoring system in future experiments.

The article describes the local deformation method to determine the tension of cord and thin membrane elements in space deployable structure as antenna reflector. Possible measuring instrument model, analytical and numerical solutions and experimental results are presented. The boundary effects on measurement results of metallic mesh reflector surface tension are estimated. The study case depicting non-uniform reflector surface tension is considered.