Shape Memory Polymer Composite Booms with Applications in Reel-Type Solar Arrays

Solar arrays are the primary energy source for spacecraft.Although traditional rigid solar arrays improve power supply,the quality increases proportionally.Hence,it is difficult to satisfy the requirements of high-power and low-cost space applications.In this study,a shape-memory polymer composite(SMPC)boom was designed,fabricated,and characterized for flexible reel-type solar arrays.The SMPC boom was fabricated from a smart material,a shape-memory polymer composite,whose mechanical properties were tested.Additionally,a mathematical model of the bending stiffness of the SMPC boom was developed,and the bending and buckling behaviors of the boom were further analyzed using the ABAQUS software.An SMPC boom was fabricated to demonstrate its shape memory characteristics,and the driving force of the booms with varying geometric parameters was investigated.We also designed and manufactured a reel-type solar array based on an SMPC boom and verified its self-deployment capability.The results indicated that the SMPC boom can be used as a deployable unit to roll out flexible solar arrays.

Theoretical Analysis of the Buckling Behaviors of Inhomogeneous Shape Memory Polymer Composite Laminates Considering Prestrains

The mismatch in thermal expansion coefficients between the fiber-rich and resin-rich regions of a shape memory polymer composite(SMPC)laminate,along with the residual strain during SMPC fabrication,results in buckling deformation of the inhomogeneous laminate.This paper presents a macroscopic model for buckling of an inhomogeneous SMPC laminate under initial biaxial prestrains.Both linear and nonlinear buckling analyses are carried out using the energy method.The influences of prestrain biaxiality,temperature,and ply angle on the buckling wavelength,critical buckling prestrain,and buckling amplitude are calculated.The results demonstrate that the critical buckling wavelength of the SMPC laminate is independent of the prestrain,while the amplitude is almost independent of temperature.In addition,the optimal fiber stacking configuration with the maximum critical buckling prestrains of inhomogeneous SMPC laminates is determined by a genetic algorithm.

World’s first spaceflight on-orbit demonstration of a flexible solar array system based on shape memory polymer composites

With a 10%reversible compressive strain in more than 10 deformation cycles,the shape memory polymer composites(SMPCs)could be used for deployable structure and releasing mechanism.In this paper,without traditional electro-explosive devices or motors/controllers,the deployable SMPC flexible solar array system(SMPC-FSAS)is studied,developed,ground-based tested,and finally on-orbit validated.The epoxy-based SMPC is used for the rolling-out variable-stiffness beams as a structural frame as well as an actuator for the flexible blanket solar array.The releasing mechanism is primarily made of the cyanate-based SMPC,which has a high locking stiffness to withstand 50 g gravitational acceleration and a large unlocking displacement of 10 mm.The systematical mechanical and thermal qualification tests of the SMPC-FSAS flight hardware were performed,including sinusoidal sweeping vibration,shocking,acceleration,thermal equilibrium,thermal vacuum cycling,and thermal cycling test.The locking function of the SMPC releasing mechanisms was in normal when launching aboard the SJ20 Geostationary Satellite on 27 Dec.,2019.The SMPC-FSAS flight hardware successfully unlocked and deployed on 5 Jan.,2020 on geostationary orbit.The triggering signal of limit switches returned to ground at the 139 s upon heating,which indicated the successful unlocking function of SMPC releasing mechanisms.A pair of epoxy-based SMPC rolled variable-stiffness tubes,which clapped the flexible blanket solar array,slowly deployed and finally approached an approximate 100%shape recovery ratio within 60 s upon heating.The study and on-orbit successful validation of the SMPC-FSAS flight hardware could accelerate the related study and associated productions to be used for the next-generation releasing mechanisms as well as space deployable structures,such as new releasing mechanisms with low-shocking,testability and reusability,and ultra-large space deployable solar arrays.

Preliminary design and analysis of a cubic deployable support structure based on shape memory polymer composite

The deployable structures based on shape memory polymer com-posites(SMPCs)have been developed for its unique properties,such as high reliability,low-cost,lightweight,and self-deployment without complex mechanical devices compared with traditional deployable structures.In order to increase the inflatable structure system’s robustness and light the weight of it,a cubic deployable support structure based on SMPC is designed and analyzed pre-liminarily.The cubic deployable support structure based on SMPC consists of four dependent spatial cages,each spatial cage is composed of 12 three-longeron SMPC truss booms and end con-nections.The shape recovery of arc-shaped deployable laminates drive the three-longeron SMPC truss booms to unfold,thus realize the expansion of the deployable support structure.The concept and operation of the cubic deployable support structure are described in detail.A series of experiments are performed on the three-longeron deployable laminates unit and the simplified cubic deployable support structure to investigate the shape recovery behavior in the deployment process.Results indicate that the cubic deployable support structure has a high deployment-tgo-stowage volume ratio and can achieve self-deployment,package,and deploy without complex mechanical devices.

A Shape-Memory Deployable Subsystem with a Large Folding Ratio in China’s Tianwen-1 Mars Exploration Mission

Once China’s Tianwen-1 Mars probe arrived in a Mars orbit after a seven-month flight in the deep cold space environment,it would be urgently necessary to monitor its state and the surrounding environment.To address this issue,we developed a flexible deployable subsystem based on shape memory polymer composites(SMPC-FDS)with a large folding ratio,which incorporates a camera and two temperature telemetry points for monitoring the local state of the Mars orbiter and the deep space environment.Here,we report on the development,testing,and successful application of the SMPC-FDS.Before reaching its Mars remote-sensing orbit,the SMPC-FDS is designed to be in a folded state with high stiffness;after reaching orbit,it is in a deployed state with a large envelope.The transition from the folded state to the deployed state is achieved by electrically heating the shape memory polymer composites(SMPCs);during this process,the camera on the SMPC-FDS can capture the local state of the orbiter from multiple angles.Moreover,temperature telemetry points on the SMPC-FDS provide feedback on the environment temperature and the temperature change of the SMPCs during the energization process.By simulating a Mars on-orbit space environment,the engineering reliability of the SMPC-FDS was comprehensively verified in terms of the material properties,structural dynamic performance,and thermal vacuum deployment feasibility.Since the launch of Tianwen-1 on 23 July 2020,scientific data on the temperature environment around Tianwen-1 has been successfully acquired from the telemetry points on the SMPCFDS,and the local state of the orbiter has been photographed in orbit,showing the national flag of China fixed on the orbiter.

Application of interpolated double network model for carbon nanotube composites in electrothermal shape memory behaviors

Multi-wall carbon nanotube filled shape memory polymer composite(MWCNT/SMC)possessed enhanced modulus,strength,and electric conductivity,as well as excellent electrothermal shape memory properties,showing wide design scenarios and engineering application prospects.The thermoelectrically triggered shape memory process contains complex multi-physical mechanisms,especially when coupled with finite deformation rooted on micro-mechanisms.A multi-physical finite deformation model is necessary to get a deep understanding on the coupled electro-thermomechanical properties of electrothermal shape memory composites(ESMCs),beneficial to its design and wide application.Taking into consideration of micro-physical mechanisms of the MWCNTs interacting with double-chain networks,a finite deformation theoretical model is developed in this work based on two superimposed network chains of physically crosslinked network formed among MWCNTs and the chemically crosslinked network.An intact crosslinked chemical network is considered featuring with entropic-hyperelastic properties,superimposed with a physically crosslinked network where percolation theory is based on electric conductivity and electric-heating mechanisms.The model is calibrated by experiments and used for shape recoveries triggered by heating and electric fields.It captures the coupled electro-thermomechanical behavior of ESMCs and provides design guidelines for MWCNTs filled shape memory polymers.

Advances in 4D printed shape memory composites and structures:Actuation and application

Shape memory polymer composites(SMPCs)are a type of smart material that can change shapes under the stimulation of the external environment,and they have great potential in aerospace,biomedical,robotics,and electronic devices due to their advantages of high strength and toughness,lightweight,impact resistance,corrosion resistance,and aging resistance.4D printing technology has provided new opportunities for the further development of smart materials.The addition of various fillers enriches the variety of printable materials and provides composites with different properties and functions.The combination of SMPCs and printing technologies realizes the structure-function integration.This paper introduces the emergence and development of 4D printing technologies,the preparation methods and properties of SMPCs for 4D printing;as well as the research progress and potential application of 4D printable SMPCs in recent years in terms of thermal,electrical,magnetic,and optical driving.Finally,the existing problems and future development of 4D printable SMPCs are discussed.

A hygro-thermo-mechanical constitutive model for shape memory polymers filled with nano-carbon powder

The nano-carbon powders are often used as fillers to endow the shape memory polymers(SMPs)with electroconductivity.It has been found that the shape memory effects(SMEs)of SMPs filled with nano-carbon powder can be triggered both by temperature and by water.To reveal the driving mechanism of SMEs,a constitutive model for describing the thermally activated and moisture activated SMEs of these shape memory polymer composite(SMPCs)is developed here.Because both of the SMEs share the same driving mechanism,the variable moisture is incorporated into the framework of a thermo-mechanical modeling approach to disclose the effect of moisture on the thermoviscoelastic properties.The SMPCs are regarded as isotropic materials and the effect of carbon powder on the mechanical properties of the matrix is also considered in the paper.Because the complete recovery may not be reached even they are exposed to the stimulus environment long enough,the blocking mechanism is also considered here.This is the mainly new contribution compared to the early work.Using the method of parameter determination presented here,the effectiveness of the proposed hygro-thermo-mechanical constitutive model is confirmed by comparing the model results with the test data of uniaxial deformation from the literature.

Design of 4D printed shape-changing tracheal stent and remote controlling actuation

has a good application prospect.The biodegradable stent can effectively reduce the damage to patients and improve the therapeutic performance of stents.In this work,a series of shape memory polylactic acid(Fe_(3)O_(4))composite tracheal stents were manufactured by 4D printing.The composite tracheal stents with different structures were designed.Moreover,with the addition of magnetic particles Fe3 O4,the shape memory PLA/Fe_(3)O_(4)composite tracheal stent has a magnetic driving effect.Under the magnetic field,the shape recovery process is completed within 40 s,and the shape recovery rate is more than 99%.Moreover,the 4D printed tracheal stent was also triggered by the irradiation of infrared lamp to realize the remote controlling recovery.The research on the structure design and driving method of 4D printing tracheal stent expands the application scope of shape memory polymer composites in biomedical field,provides a new way for personalized implantable medical devices and minimally invasive surgery.It is of great significance for better precision medical treatment.