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One of the common challenges of spaceflight and e-mobility is the energy storage. The operational ranges of spacecraft or electric cars as well as operational usability is strongly dependent on the capacity of the energy storage, which is usually constrained by the mass and volume of the vehicle. For example, the battery mass of large communication satellites ranges from 6% to 9% of the dry mass. This amount increases for smaller satellites like CubeSats up to 13% without accounting wiring harnesses and subsystem volume. Thus, a system can benefit from a reduction in mass and volume by combining multifunctional use of the components and materials. In the presented research, energy storage is integrated into lightweight carbon fiber materials. Carbon fibers have a distinct mass advantage compared to metal structures. In addition, they have very low thermal expansions that can reduce thermal stresses during the operation of a satellite. Fiber composites or laminates consist of two components, the fibers and the matrix material. In laminates, the typically resin based matrix content is 30–40% of the component volume and could be substituted with novel solid state battery materials. Latter have the advantage that they have nearly similar physical properties as usually used resins and are also able to store energy electrochemically. Thus, about 25% of the volume can be used for electrochemical energy storage without compromising structure integrity. To reach such electrochemical functions the host structures have to be infiltrated with anode, cathode, and separator materials. Using the developed recipes and a component thickness of 5 mm, an energy amount per component area of 1130 Wh/m2 can be reached depending on the applied battery active material. This article will give an overview of how fiber composite materials, which are increasingly being used in lightweight construction processes, can be combined with energy storage materials to be used in spacecraft structures. The goal of the research on this topic at the Technische Universtat Braunschweig is a structure battery for a spacecraft. However the article addresses as a first step the characterization and manufacturing of structural battery composite negative half-cells from carbon fiber reinforced PEO/LiTFSI. An estimation of the expected performance is carried out. The initial material evaluation and the manufacturing process as well as mechanical and electrical result will be discussed.

Multifunctionalization of fiber-reinforced composites, especially by adding energy storage capabilities, is a promising approach to realize lightweight structural energy storages for future transport vehicles. Compared to conventional energy storage systems, energy density can be increased by reducing parasitic masses of non-energy-storing components and by benefitting from the composite meso- and microarchitectures. In this paper, the most relevant existing approaches towards multifunctional energy storages are reviewed and subdivided into five groups by distinguishing their degree of integration and their scale of multifunctionalization. By introducing a modified range equation for battery-powered electric aircrafts, possible range extensions enabled by multifunctionalization are estimated. Furthermore, general and aerospace specific potentials of multifunctional energy storages are discussed. Representing an intermediate degree of structural integration, experimental results for a multifunctional energy-storing glass fiber-reinforced composite based on the ceramic electrolyte Li1.4Al0.4Ti1.6(PO4)3 are presented. Cyclic voltammetry tests are used to characterize the double-layer behavior combined with galvanostatic charge–discharge measurements for capacitance calculation. The capacitance is observed to be unchanged after 1500 charge–discharge cycles revealing a promising potential for future applications. Furthermore, the mechanical properties are assessed by means of four-point bending and tensile tests. Additionally, the influence of mechanical loads on the electrical properties is also investigated, demonstrating the storage stability of the composites.

Lithium aluminum titanium phosphate (LATP), a NASICON-type (structure of Na1 + xZr2SixP3 − xO12, 0

In the present work, we report on structural supercapacitors which are based on NASICON-type solid electrolyte Li1.4Al0.4Ti1.6(PO4)3 (LATP). The nanostructured electrodes incorporate single-wall carbon nanotubes (SWCNTs) mixed with the LATP electrolyte. The complete energy storage devices are manufactured in a sandwich structure consisting of two nanostructured electrode layers which are separated by a pure LATP layer. The as-prepared specimens are embedded in composite materials with Airstone 880/886H epoxy resin as matrix. Their electrical properties are characterized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). At ambient temperature, the addition of 6.5 wt. % SWCNTs results in a distinct improvement by reducing the total resistance of the embedded devices and enhances the capacitance from 0.025 mF g−1 to 3.160 mF g−1 at a scan rate of 5 mV s−1. Electrical measurements of two types of specimens are then applied under different temperatures from ambient temperature to 80 °C. It is observed that the equivalent series resistance (ESR) of device with SWCNTs decreases greatly and capacitance increases comparing with the device without SWCNTs. As a conclusion, the structural supercapacitors acquire excellent performance through high efficient double layer effects realized by nanostructured electrode/electrolyte interphase (large surface electrode areas).

An abnormal phenomenon was investigated in Ti44Ni51Nb5 alloy which exhibits an absence of martensite transformation and a negative temperature dependence of electrical resistivity with the temperature decreasing. X-ray diffraction (XRD) analysis shows the matrix phase keeps a B2 structure during cooling without a martensite transformation, and dynamic mechanical analysis displays a frequency-dependent AC modulus/loss anomaly at T g according to Vogel-Fulcher relation. Simultaneously, transmission electronic microscope (TEM) analysis manifests the superlattice spots at near 1/3 commensurate position, implying an existence of strain nanodomains with an R-like structure. And above experiment results provide evidence for the “strain glass” transition in defect-containing ferroelastic Ti44Ni51Nb5 alloy.

This paper presents a systematic study of newly developed metastable β-type Ti–25Nb–2Mo–4Sn (wt%) alloy with high strength and low elastic modulus, with focus on the microstructural evolution and mechanical behavior associated with aging. The pre-treatment (solution treatment or cold rolling) prior to aging exerts substantial influence on the subsequent aging response including microstructural evolution and mechanical behavior. Even under the same aging treatment, the aging products could be (β+ω), or alternatively (β+α), depending on the pre-treatments. This interesting aging response was discussed on the basis of the mechanism for ω formation. High-density dislocation tangles and grain boundaries induced by severe cold rolling play a key role in hindering the transition from β to isothermal ω, favoring the precipitation of α phase on aging. By aging cold-rolled specimen for short time, superior mechanical properties, i.e. high ultimate strength of ∼1113 MPa and low elastic modulus of ∼65 GPa, achieved in Ti–25Nb–2Mo–4Sn alloy. The characterization of microstructural evolution and compositional change indicated that the precipitation of fine α does not cause the enrichment of β-stabilizers in β matrix upon a short-time aging, guaranteeing low elastic modulus of the short-time aged specimen. Meanwhile, fine α precipitates as well as dislocations play a crucial part in strengthening, giving rise to its high yield strength and high ultimate tensile strength.

Aging response of metastable β-type Ti–25Nb–2Mo–4Sn alloys with different pre-treatments was experimentally investigated. Experimental results showed that the precipitation of isothermal ω phase can be suppressed by cold rolling prior to aging. It is considered that the dislocation tangles as well as grain boundaries play a key role in hindering the movements of dislocations necessary for the transition of β to ω. In such a case, suppressing isothermal ω and promoting fine α were achieved simultaneously during aging.

On the basis of thermoelastic martensitic transformation involved, the mechanical behaviors of NiTiNb shape memory alloys were experimentally studied and their wide hysteresis effect was theoretically discussed. It was found that even at the same temperature NiTiNb shape memory alloys perform different mechanical behaviors when under different states. In addition, the yielding behavior for the reorientation of martensite is dependent on the martensitic transformation temperature of NiTiNb alloys. The alloy with lower MS temperature exhibits lower yield stress for the reorientation of martensite. According to kinetic and thermodynamic analysis of thermoelastic martensitic transformations, a relationship between the relaxation of elastic energy and the hysteresis expansion was established. It is suggested that the mechanism for wide hysteresis of NiTiNb shape memory alloys is predominantly attributed to the Nb element dissolved in the matrix of NiTi(Nb) phase, rather than the precipitated β-Nb phase. This mechanism gains support from the present experimental study that the NiTiNb alloys with low Nb content exhibit wide transformation hysteresis upon a proper pre-deformation.

Structural supercapacitors are very interesting multifunctional devices combining the properties of an electrical energy storage device and a structural component simultaneously. These types of supercapacitors are mostly equipped with solid state electrolytes, instead of traditional liquid electrolytes, avoiding leakage and safety problems and supporting the mechanical performance of the composite materials. In the present study, the Lithium-ion based solid ceramic electrolyte Li1.4Al0.4Ti1.6(PO4)3 was successfully synthesized by sol-gel method. Its electrical properties were characterized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). Results show that Li1.4Al0.4Ti1.6(PO4)3 possesses a conductivity of 2.94×10−4 S/cm at room temperature and a specific capacity of 55.57 μF/g. The as-prepared samples were embedded into fiber composite material using the aviation approved resin RTM6 with an injection process making the composite structure flexible. Subsequently, the specific capacity and conductivity were tested getting values of 53.44μF/g and 2.00×10−4 S/cm respectively. The reason for electrical properties loss was investigated by computerized tomography (CT) and EIS tests and the results provide reference for the future research.Copyright © 2015 by ASME