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In this paper the AM-induced evolution of the design process for small satellites is investigated, leading to the identification of optimal design strategies and the definition of a new MAIT concept. A review of the open literature is presented and some introductory concepts are exposed to highlight the effect of the introduction of AM technologies in the development of new satellites systems. In particular, an innovative structural configuration for the CubeSat class of satellites is proposed, with the ultimate goal of minimizing system complexity via parts reduction and the integration of subsystems through an innovative assembly configuration, as an example to be considered for larger satellites. [ABSTRACT FROM AUTHOR]

A geometrically exact approach is employed to formulate the equations of motion of thin multi-layered composite shells subject to excitations that cause large strains, displacements, and rotations. Ad hoc truncated kinematic approximations of the obtained semi-intrinsic theory delivers, as a by-product, the kinematics of the Koiter and the Naghdi theories of shells, respectively. Numerical simulations are carried out both for cylindrical and spherical shells: nonlinear equilibrium paths are constructed considering a quasi-static load increase. The comparisons between the results furnished by the geometrically exact theory and those obtained by Koiter and Naghdi theories show the high accuracy of the proposed nonlinear approach. Classical theories become increasingly inaccurate at deflection amplitudes of the order of the shell thickness, evidencing that significant misrepresentations of the system behavior are possible if reduced-order kinematics are taken into account. [ABSTRACT FROM AUTHOR]

The dynamic behavior of composite laminates is very complex as there are many concurrent phenomena during composite laminate failure under impact load. Fiber breakage, delaminations, matrix cracking, plastic deformations due to contact and large displacements are some effects which should be considered when a structure made from composite material is impacted by a foreign object. Thus, an investigation of the low velocity impact on laminated composite plate of epoxy resin reinforced by carbon fiber is presented. The influence of stacking sequence and impact energy is investigated. The impact testing is conducted with a vertical drop-weight testing machine. Non-destructive testing is performed and the amount of damage is quantified in terms of area. The performances of ultrasonic testing, optical thermography and sonic infrared for the inspection of composite laminates with barely visible impact damage are evaluated. Finally, a comparison amongst their capabilities for such application is carried out. [ABSTRACT FROM AUTHOR]

Abstract: A numerical procedure, based on the finite element method, capable to simulate the interaction of active structures with an incompressible fluid flow is discussed. In particular the active functionality of such structures is demanded to piezoelectric type actuators. The development of this interaction is connected to the study of problems that involve an active flow control for different potential applications such as drag reduction, noise reduction, separation control, mixing enhancement, etc. Two kinds of finite element models, one for the electromechanical field and the other for the fluid-dynamic field, are set up. The analyses are performed with a coupled iterative solver, based on the arbitrarian Lagrangian–Eulerian (ALE) description. A Reynolds-averaged Navier–Stokes Equations (RANS) formulation for the model of turbulent fluid is adopted. The results of some numerical analyses are correlated to an experimental benchmark case founded in literature with the aim to validate the procedure. A sample application to modify the features of separated flow from a backward facing step is described, in which a piezoelectric unimorph actuator is patched on a Euler–Bernoulli beam installed at the upper corner of the step. The numerical model describes the displacement of the incoming shear layer and the velocity perturbation produced by the periodic oscillations of the actuator and how these parameters are related to each other. In order to produce sensible amplitude for the oscillations, the actuator is driven near its natural frequency. A preliminary response analysis to examine the effects of the fluid on the resonant behaviour of the structure is illustrated. [Copyright &y& Elsevier]

In recent years the so-called New Space Economy or Space 4.0 paradigm has seen a number of new commercial players entering the satellite industry and creating completely new business models, most of which based on very large constellations consisting of several hundreds or even thousands of satellites. The production of the high number of satellites involved in modern mega-constellations is bringing in the space industry the necessity of improved and optimized manufacturing approaches suitable for serial production , i.e., standard environment/high number of platforms. In this framework, the adoption of Industry 4.0 methodologies within the space industry will lead to a significant improvement and optimization of the whole Manufacturing Assembly Integration and Testing (MAIT) cycle. The main aim of Industry 4.0 is the creation of intelligent factories where manufacturing technologies are upgraded and transformed by Cyber-Physical Systems (CPSs), the Internet of Things (IoT), Cloud Computing and Big Data Analytics with predictive monitoring features. Main element of the Industry 4.0 approach is the synergic use of embedded sensing technologies in the frame of intelligent production processes, fostering a radical evolution of the industrial values chains, production value chains, and business models. In the present work, a possible application of the Industry 4.0 concepts to space industry is presented and discussed in terms of applicability and obtainable advantages. As a case study, the composite sandwich panel manufacturing line of RUAG Space is considered. Particular focus will be given to the development of a CPS, by establishing a control network of sensors (e.g. temperature, location, load) over a targeted MAIT process. • The implementation of Industry 4.0 logics to satellite industry is considered. • The composite panel manufacturing MAIT process is considered as case-study. • A CPS of the composite panel manufacturing MAIT process is built. • AI logics are considered in order to improve the monitoring and control of the selected process. • The benefit of Smart Manufacturing for satellite industry are discussed. [ABSTRACT FROM AUTHOR]

The unremitting quest of natural and renewable materials able to replace their synthetic counterparts in high-performance applications has involved also sandwich structures. In this regard, the aim of this work is to characterize the impact response, in both high- and low-velocity conditions, of green sandwich structures made of agglomerated cork as core and flax/epoxy laminates as face sheets. Both bare cork, flax skins, and complete sandwich structures were subjected to impacts at three different energy levels representing the 25%, 50%, and 75% of the respective perforation thresholds. A gas gun was instead used to assess the high-velocity impact behavior of these green sandwich structures and evaluate their ballistic limit. This study shows that the buckling of cell walls of agglomerated cork enables to tailor the damage extension through-the-thickness in low-velocity impacts compared to traditional synthetic foams coupled with a considerable amount of energy absorption. [ABSTRACT FROM AUTHOR]

Abstract Smart materials offer the possibility of the integration of active functions into a composite primary structure. This work aim to investigate the impact of the incorporation of smart materials in a conventional composite laminate. Fiberglass specimens with and without PZT piezo elements embedded in the lamination stack are manufactured and then subjected to a four-point bending test. Together with the classical mechanical parameters, the operational behaviour of the piezo as sensor is monitored in terms of electrical capacity during test. Benefits and disadvantages of the embedment of a piezo element in a laminate are evidenced from a comparison of the experimental results. In parallel, numerical models of the experimental setup and test, with a finite element approach, allows to explore the mechanisms of damage of such kind of sensorized specimens. [ABSTRACT FROM AUTHOR]

The aim of this work is to investigate the effect of basalt fibre hybridization on carbon/epoxy laminates when subjected to high velocity impacts. In this regard, interply hybrid specimens with four different stacking sequences (sandwich-like and intercalated structures) are tested and compared to non-hybrid reference laminates made of either only carbon or only basalt layers. The response to high velocity impact tests is assessed through the evaluation of the impact and residual velocities of the projectile and the ballistic limit, calculated using experimental data, is compared with the results given by an analytical model, showing a good agreement. The damage in composite laminates is investigated by destructive (optical microscopy) and non-destructive (ultrasonic phased array) techniques. As a result of basalt hybridization, the ballistic limits of all sandwich configurations are enhanced if compared to those of carbon laminates. Therefore the observed decrease of static mechanical properties of hybrid composites is largely compensated by improved response to impact. Advantages also come in terms of cost saving, since the basalt fibre is far less expensive than the carbon one. [ABSTRACT FROM AUTHOR]

This work reports on a preliminary study to assess the response of fibre metal laminates (FMLs) made of stacked layers of basalt fabric epoxy prepreg and aluminium sheets to low velocity impact and, through comparison with published results for Glare materials, benchmark their impact performance. Comparison is also made with results from plates of monolithic aluminium with comparable thickness. The effect of impactor size is also investigated whilst the impact energies were selected with the aim of inducing first crack (FC) and through the thickness crack (TTT) on the FML samples. Optical microscopy and profilometry were used to elucidate fracture mechanisms and the dent depth. The response of basalt fibre metal laminates was found to be both significantly influenced by the impactor size and fairly positive, proving to be competitive with monolithic aluminium plates although some issues about the aluminium/basalt interface have been raised. [ABSTRACT FROM AUTHOR]

Abstract: This study addresses the effects of basalt fibre hybridization on quasi-static mechanical properties and low velocity impact behaviour of carbon/epoxy laminates. Interply hybrid specimens with two different stacking sequences (sandwich-like and intercalated) are tested at three different energies, namely 5, 12.5 and 25J. Residual post-impact properties of the different configurations of carbon/basalt hybrid laminates are characterized by quasi static four point bending tests. Post-impact flexural tests and interlaminar shear tests are used for the mechanical characterization along with two non-destructive methods, namely acoustic emission and ultrasonic phased array, in order to get further information on both the extent of damage and failure mechanisms. Results indicate that hybrid laminates with intercalated configuration (alternating sequence of basalt and carbon fabrics) have better impact energy absorption capability and enhanced damage tolerance with respect to the all-carbon laminates, while hybrid laminates with sandwich-like configuration (seven carbon fabric layers at the centre of the laminate as core and three basalt fabric layers for each side of the composite as skins) present the most favourable flexural behaviour. [Copyright &y& Elsevier]

The present article is a summary of the activities done by a research group of the University of Rome “La Sapienza” on the subject of fluid–structure interaction (FSI). Implementation and numerical simulations have been conducted by means of a technique known in the literature as the partition treatment technique. A procedure to transfer the interaction effects between the individual components (fluid and structure) has been developed. As example of the methodology implemented, a numerical study of a hot flow through a pipe with a flexible structure inside, is presented. Results show that the heat flux distribution along the structure is highly influenced by the structure deformation. [ABSTRACT FROM AUTHOR]

Double ‘free-hybrids’ (DH) in alfalfa were obtained by crossing in a diallelic scheme, six multiplied simple hybrids (SH) derived from four partly inbred (S2) lines. Analysis of the specific combining ability demonstrated that the main source of variation was for dry matter yield (DMY) in DHs and supported heterosis values of DHs versus the best parent of an average +45% (ranging from +5 to +76%). Investigation at the molecular level was carried out by analysis of simple sequence repeat markers on the six parental SHs and 15 DH progenies and by comparison of gene expression profiles using microarrays of a single DH line to its parental lines. The variation of heterozygosity estimates of the DHs explained a small part (about 20%) of their variation in DMY, while the number of alleles was significantly related to DM performance (r = 0.61; P < 0.05). The microarray analysis identified genes with both significant additive and non-additive levels of expression in the hybrid compared with the parents. The majority of the variation in gene expression was additive (87%), but among the genes with a non-additive pattern of expression, the greater proportion of probe sets (86%) fell outside the parental range. Gene ontology analysis of these genes revealed the presence of a number of terms related to metabolism and genetic information processing. [ABSTRACT FROM AUTHOR]