Abstract
CubeSats are becoming an alternative challenge for space exploration. Research in the technology and applicability of these small platforms has received an increasing interest in the last years. They represent an emergent technological market (CAGR growth of 37.91 % in the 2017-2021 period), while a variety of fields like meteorology, climatic research, transportation safety, or navigation is resorting to this technology. As more complex CubeSats missions are defined, a natural increase in the mission power demand occurs. In a scarce-resource environment like the space, this demands the development of new ways of harvesting spacecraft electrical energy. An alternative to traditional energy harvesting systems composed of solar panels and batteries is Wireless Energy Transfer (WET). It originates in the electromagnetic transfer, proven to have two important limitations: high power efficiency decrease at distances bigger than coil size and the need of mobile parts. A new approach is proposed as a solution to these limitations: the possibility of mounting on a 3U CubeSat photo-thermoelectric generator array devices that can convert photon energy to electrical energy via thermal gradient generation. For creating the thermal gradient, a long-range laser source targets cells from each array forming the hybrid photo-thermoelectric plasmonic system (HPTP). Two possible scenarios are presented in terms of mission requirements and analysis: a controlled pulsed large-range laser source located on Earth, in the case of Earth-orbiting missions, or on a hub system, in a deep-space mission. For Earth, Mars and Jupiter, a simulation of the total energy produced by solar panels and the HPTP system is presented to illustrate the potential use of the WiPTherm technology. In each of the scenarios, key measures of effectiveness will be analysed to overcome potential CubeSat and constituent subsystems overheat, by comparison with nominal component and shield temperature profiles in both eclipse and illuminated cases when the HPTP system is not used. Pointing budget accuracy and jitter for targeting the HPTP generator cells and required laser link budget for a planned energy transfer efficiency of up to 10 % of the source power are other challenges covered in the presentation, apart from research topics from a multidisciplinary group covering nanomaterials science, optics, photonics, and CubeSats power systems engineering. Copyright

Abstract
This chapter focuses on new compositions of thermoplastic matrices and reinforcements to process by fused deposition modelling (FDM). The available materials for this additive manufacturing (AM) technique are generally limited to PLA—polylactic acid, ABS—acrylonitrile butadiene styrene and PA—polyamide (NYLON®) with temperature gradients and mechanical behaviours that are not suited for high-performance applications, such as aeronautics and automotive sector. In this work, an intensive research was made in order to evaluate mechanical, thermal and rheological properties considered important for 3D printing of commercial filaments. Results aided in the selection of high-performance reinforced materials for AM. Advanced polymers, such as PEEK—polyether ether ketone and PA66—polyamide 66, were the matrices chosen to produce high service nanocomposite formulations, each with varying amounts of multi-wall carbon nanotubes (MWCNTs). The resulting feedstock materials were characterized using the same techniques as the commercial filaments. Preliminary tests with printed parts of these composites were made in pursuance of their optimal printing parameters to undergo an experimental hybrid system (EHS). © 2020, The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG.

Abstract
Composites are finding increased use in structural high demanding and high added value applications in advanced industries. A wide diversity exists in terms of matrix type, which can be either polymeric or metallic and type of reinforcements (ceramic, polymeric or metallic). Several technologies have been used to produce these composites; among them, additive manufacturing (AM) is currently being applied. In structural applications, the presence of defects due to fabrication is of major concern, since it affects the performance of a component with negative impact, which can affect, ultimately, human lives. Thus, the detection of defects is highly important, not only surface defects but also barely visible defects. This chapter describes the main types of defects expected in composites produced by AM. The fundamentals of different non-destructive testing (NDT) techniques are briefly discussed, as well as the state of the art of numerical simulation for several NDT techniques. A multiparametric and customized inspection system was developed based on the combination of innovative techniques in modelling and testing. Experimental validation with eddy currents, ultrasounds, X-ray and thermography is presented and analysed, as well as integration of distinctive techniques and 3D scanning characterization. © 2020, The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG.

Abstract
This paper focuses on three main issues regarding Material Extrusion (MEX) Additive Manufacturing (AM) of thermoplastic composites reinforced by pre-functionalized continuous Nickel-Titanium (NiTi) wires: (i) Evaluation of the effect of the MEX process on the properties of the pre-functionalized NiTi, (ii) evaluation of the mechanical and thermal behavior of the composite material during usage, (iii) the inspection of the parts by Non-Destructive Testing (NDT). For this purpose, an optical fiber sensing network, based on fiber Bragg grating and a cascaded optical fiber sensor, was successfully embedded during the 3D printing of a polylactic acid (PLA) matrix reinforced by NiTi wires. Thermal and mechanical perturbations were successfully registered as a consequence of thermal and mechanical stimuli. During a heating/cooling cycle, a maximum contraction of approximate to 100 mu m was detected by the cascaded sensor in the PLA material at the end of the heating step (induced by Joule effect) of NiTi wires and a thermal perturbation associated with the structural transformation of austenite to R-phase was observed during the natural cooling step, near 33.0 degrees C. Regarding tensile cycling tests, higher increases in temperature arose when the applied force ranged between 0.7 and 1.1 kN, reaching a maximum temperature variation of 9.5 +/- 0.1 degrees C. During the unload step, a slope change in the temperature behavior was detected, which is associated with the material transformation of the NiTi wire (martensite to austenite). The embedded optical sensing methodology presented here proved to be an effective and precise tool to identify structural transformations regarding the specific application as a Non-Destructive Testing for AM.

Abstract
Bi-core optical fiber structures are studied for applications in sensing. In this paper, an analysis is performed on the spectral characteristics of light propagating in these fibers with central launching core illumination from a standard single mode fiber. Reflective and transmissive configurations are addressed. The characteristics of a reflective bi-core fiber structure for measurement of strain, temperature and absolute value of torsion are investigated and highlights for further research are presented.

Abstract
We present the design, fabrication and optical characterization of functional metamaterials for optical sensing of Hydrogen based on inexpensive self-assembly processes of metallic nanowires integrated in nanoporous alumina templates([37-42]). The optical properties of these materials strongly depend on the environmental concentration or partial pressure of hydrogen and can be used to develop fully optical sensors that reduce the danger of explosion. Optical metamaterials are artificial media, usually combining metallic and dielectric sub-wavelength structures, that exhibit optical properties that cannot be found in naturally occurring materials. Among these, functional metamaterials offer the added possibility of altering or controlling these properties externally after fabrication, in our case by contact with a hydrogen rich atmosphere. This dependency can be used to design([43-45]) and develop optical sensors that respond to this gas or to chemical compounds that contain or release hydrogen. In this paper we present some designs for hydrogen functional metamaterials and discuss the main parameters relevant in the optimization of their response.