This article investigates if and at what extent a recycling process based on grinding, melting and re-shaping of recycled carbon fibers reinforced thermoplastic polymers (rCFRPs) can affect their physical, mechanical and thermal properties. The aim is to establish if they can be taken into consideration in the manufacturing of new composite materials in different sectors: automotive, marine, sporting goods, etc. Composites materials were submitted to the measurement of the fibers length they are composed of, and then analyzed by means of tensile and impact tests and a dynamic mechanical analysis (DMA). All the characterizations were performed to both initial and recycled composites and, in some cases, they were replied also after the intermediate accelerated aging. Characterization performed confirmed that, as expected, the recycling process affects the properties of the composites, but in different manners and to a different extent when different polymers are involved. Tensile and impact tests pointed out that the polypropylene based composites showed a less stiff and a more brittle behaviour after the recycling process and the DMA confirmed this evidence, highlighting in addition a more viscous behavior of the polymer after the recycling. Conversely, the polyamide 6 based composites increased their stiffness and ductility after the recycling. For all the composites the tensile strength dropped, confirming the weakening of the materials.

In this work the architectural anisotropy of short fiber reinforced polymers (SFRPs) has been characterized using X-ray computed micro-tomography (micro-CT) with four different morphometric methods: Mean Intercept Length (MIL), Volume Orientation (VO), Star Length Distribution (SLD) and Star Volume Distribution (SVD). The fabric tensor obtained from micro-CT analysis provided information on the fiber orientation, indicating that fibers were partially aligned in the injection direction. The fiber length and orientation obtained from optical microscopy and from the morphometric analysis in 3D, respectively, has been used to determine the mechanical properties of the composite sample, using a model based on micro and macromechanics. This approach leads to the prediction of the elastic constants of the component for any possible composite morphology resulting from injection, representing a key need for the design of SFRP components.

In this reported research activity, a quantitatively 3D characterization at microscale of a CFRP reference composite with controlled porosity was performed by micro X-ray CT (µXCT); the results were compared with the destructive acid digestion analyses, following the procedure reported in the standard test method (ASTM D 3171 15) used to determine the composites’ porosity in General Aviation (GA). The μXCT analyses revealed a pore content of 4.37%v and identified the components, respectively, in 66%w of carbon fibres and 34%w of matrix; all obtained results demonstrated a high correspondence to the theoretical values of porosity (5.0%v) and components (67%w of carbon fibre and 33%w of polymer matrix). Instead, a not complete correspondence of the measures obtained by acid digestion was reported: 4.36%v of porosity, but 57%w of carbon fibre and 43%w of matrix. Therefore, the conformity of the μXCT results to the theoretical values demonstrated the feasibility and distinctiveness of the proposed NDT method for a rapid and reliable inspection of CRFP components used in GA in substitution of the standard DT and time-consuming digestion procedure. The proposed NDT inspection technique permitted not only the individuation and visualization in the reconstruction of the 3D analysed material of different components (e.g. pores, carbon fibres and polymer matrix) but also the 3D evaluation of the material composition with the identification and quantification of each constituent element. E. Dilonardo*, M. Nacucchi, F. De Pascalis, M. Zarrelli, and C. Giannini Inspection of Carbon Fibre Reinforced Polymers: 3D identification and quantification of components by X-ray CT

The anisotropy of a short fiber reinforced composite produced by injection molding of basalt fibers and polypropylene matrix has been studied by X-ray microtomography (or micro-CT). Fiber orientation was analyzed using four stereological methods: Mean Intercept Length (MIL), Volume Orientation (VO), Star Volume Distribution (SVD) and Star Length Distribution (SLD). The fabric tensor obtained from micro-CT analysis provided information on the fiber orientation, indicating that fibers were partially aligned in the injection direction.

Mechanical properties of fibres reinforced composite materials depend on the type of fibres used, their percentage as well as their arrangement and orientation. As computer technology continues to improve, high-resolution computed tomography has proven to be an ideal instrument to analyse the structure of this kind of materials. In this context, various approaches have been proposed to detect the fibre orientation distribution and the relative degree of anisotropy of these composite materials. Some of these approaches are based on 'individual' measurements that isolate and reconstruct each single fibre and measure its properties. On the other hand, other approaches capture the characteristics of the fibre distribution by means of 'global' measurements computed on the entire set of tomographic data. The first methods are more precise but also more complex because they demand a procedure able to segment and separate each single fibre in the polymer, whereas the latter are easier to implement and can be applied even if fibre segmentation and separation is not effective or practicable. In this paper, a global method based on the technique called volume orientation - originally proposed several years ago to study the anisotropy of bone structures - is applied to fibre reinforced composite materials. This new approach does not require data acquired at very high resolution nor very complex procedures for individual segmentation of the fibres, but only binarised data through common thresholding procedures. The effectiveness of the proposed new approach is demonstrated by comparing it to the results obtained from a method based on individual measurements: when resolution and images quality are good enough, the volume orientation method gives results quite similar to the other approach. The analysis of three different case studies demonstrates its flexibility and its validity as an alternative to methods based on the separation of individual fibres, which are not always usable. The samples have been carefully selected in order to range between different attenuation contrast levels and also include a specimen subjected to mechanical testing which can be of great practical interest. LAY DESCRIPTION: Mechanical properties of fibres reinforced composite materials depend on the type of fibres used, their percentage as well as their arrangement and orientation. Today, both destructive and nondestructive techniques can be used in order to assess the fibre orientation. As computer technology continues to improve, high-resolution computed tomography has proven to be an ideal instrument to analyse the structure of this kind of materials, and then the fibre orientation distribution inside the material. In this context, various strategies have been proposed. Some of them require measurements that isolate and reconstruct each single fibre and measure its properties. On the other hand, other approaches capture the characteristics of the fibre distribution by means of 'global' measurements computed on the entire set of tomographic data. The first methods are more precise but also more complex because they demand a procedure able to detect and separate each single fibre in the polymer, whereas the latter are easier to implement and can be applied even if fibre segmentation and separation is not effective or practicable. In this paper, a global method based on the technique called volume orientation - originally proposed several years ago to study the microstructure of bone tissues - is applied to fibre reinforced composite materials. The aim of this work is to demonstrate that this new approach is easier to use. As a matter of fact, it does not require data acquired at very high resolution nor very complex procedures for individual segmentation of the fibres, but only binarised data through common thresholding procedures. The effectiveness of the proposed new approach is shown by comparing it to the results obtained from a method based on individual measurements: when spatial resolution and images quality are good enough, the volume orientation method gives results quite similar to the other already used approach. The analysis of three different case studies demonstrates its flexibility and its validity as an alternative to methods based on the separation of individual fibres, which are not always usable. The samples have been carefully selected in order to range between different attenuation contrast levels and different nature of the fibres (mineral, vegetable or synthetic). A specimen subjected to mechanical testing is also included, because of its great practical interest.

Structural anisotropy of two-phase materials can be evaluated through global measurements, as volume orientation or mean-intercept length methods do, or through statistics performed on a set of individual measurements. This last procedure is encouraged by recent improvements in the spatial resolution of conventional X-ray tomography. In this paper, the above-described approaches were compared in three case studies: a foam subjected to an in situ compression test, a second foam with a completely different cell morphology and a plastic material reinforced with short fibres. The approach based on the subdivision into distinguishable objects of the considered material phase has proved to be more sensitive in highlighting small deformations in the structure or small irregularities in an otherwise isotropic structure. On the other hand, the other approach is more general and is always usable. The two methods for calculating the fabric tensor tend to converge as the average anisotropy of individual objects in the statistical population increases. The use of Lambert's cylindrical equal-area projection of cell/fibre directions or local volume orientations is suggested, because the density of points is preserved from the sphere to the plane surface. Finally, a quick vector method to evaluate the anisotropy of the directions distribution has been presented, by defining a coherence index of the average direction.

Heat management in hydrogen storage tanks is a mandatory issue in order to ensure high level performances both in terms of hydrogen release/uptake kinetics and storage capacity. Previous research has ascertained that powders tend to pack and sinter during charge/discharge cycling giving rise to non-reacting material. Moreover powders, with intrinsically low thermal conductivity, can show problems related to hydrogen permeability, and suffer from hydraulic losses and particle entrainment by gas flow. To overtake these problems and to keep high performances, hydride powders mixed with high thermal conductivity additives are compacted in pellets. Some materials, like Expanded Natural Graphite (ENG), besides improving the pellet mechanical stability during cycling, can impart a thermal conductivity higher by order of magnitudes with respect to a simple powdered bed. On the basis of these considerations, pelleting can be very effective in improving tank performances. However pellets tend to swell and lose compactness during long term operation, returning back to the powder form with a detrimental effect on tank performances. In this work the swelling process caused by cycling of pellets simulating tank exercise has been studied. The pellets, which are constituted by ball milled magnesium hydride (MgH2) with the addition of niobium oxide (Nb2O5) and ENG, have been deeply studied by different microscopic methods including Scanning Electron Microscopy (SEM), Helium Ion Microscopy (HeIM) and high resolution Computed Tomography (CT) with the purpose of ascertaining microstructural modification and degradation mechanism in order to define strategies for material preparation able to reduce the entity of the swelling process.

Advanced polymeric foams with enhanced thermal insulation and mechanical properties are used in a wide range of industrial applications. The properties of a foam strongly depend upon its cell structure. Traditionally, their microstructure has been studied using 2D imaging systems based on optical or electron microscopy, with the obvious disadvantage that only the surface of the sample can be analysed. To overcome this shortcoming, the adoption of X-ray micro-tomography imaging is here suggested to allow for a complete 3D, non-destructive analysis of advanced polymeric foams. Unlike metallic foams, the resolution of the reconstructed structural features is hampered by the low contrast in the images due to weak X-ray absorption in the polymer. In this work an advanced methodology based on high-resolution and low-contrast techniques is used to perform quantitative analyses on both closed and open cells foams. Local structural features of individual cells such as equivalent diameter, sphericity, anisotropy and orientation are statistically evaluated. In addition, thickness and length of the struts are determined, underlining the key role played by the achieved resolution. In perspective, the quantitative description of these structural features will be used to evaluate the results of in situ mechanical and thermal test on foam samples.

Advanced polymeric foams are used in a wide range of industrial and R&D applications. Their properties strongly depend upon the cell structure. Traditionally, their microstructure has been studied using optical or electron microscopy, limiting the investigations to sample’s surface only. To overcome this shortcoming, the use of X-ray micro-tomography imaging is here adopted to allow for a complete 3D, non-destructive analysis of advanced polymeric foams. This work brings to fruition high resolution and low-contrast imaging techniques to perform quantitative analyses onto polymeric foams, where the low contrast of reconstructed structural features might hamper accurate quantitative analyses. Local structural features of individual cells are statistically evaluated, showing the key role of the achieved resolution.

To preserve the state of maintenance of good of historical interest - artistic involves investigations on the appearance, on the actual state and on the alteration and deterioration processes of artistic object. The project SIDART (Integrated System for the Diagnostic one of the ARTistic goods) allows to collect different kind of information in systematic and scientific way for an accurate diagnosis of the mechanisms that the deterioration and to operate with the most effective and appropriate remedies to the situation. The objective is to create an integrated system for the diagnostic of the cultural heritages that allows acquisition, elaboration and aggregation of different kind of measure with the purpose to study interventions with maximum effectiveness, minimum cost and minimum risk for the integrity of the object. Such system includes the search and the debugging of new portable technologies, the online integration of classical methods, the export of the data toward vertical informative systems for the operators in the sector. Particularly, the project is divided in different parts : The first consists to build a portable system for the preliminary diagnosis in place, for instance the creation of a new laser scanner system for high resolution 3D scanning. Then was developed some application techniques of complexes systems of diagnostic (tools of physical and chemistry analysis for the molecular knowledge of the work of art) and for reverse - engineering and virtual geometric modelling, that is visualization of three-dimensional images for virtual models and tools for the assistance to the diagnosis. Other parts of the project consists in the development of invadingless methods of analysis of the structures and the realization of simulation models of deterioration process of inquiry object. At least the project provide for the realization of an integrated informative system, that collects and organizes all the information coming from the precedents parts allowing a diffusion of final results.

Various technologies have been developed to conduct preliminary investigation prior to restoration interventions, thus resolving studies and problems regarding intervention strategy choose. Each of this technologies give to the end-user different kind of information that are useful to understand the health condition of the artwork. This paper illustrates the development of a software that allows to integrate the set of data retrieved by the different instruments. The aim is to obtain a better knowledge and perception of damages and decline process. In particular the software allows to elaborate laser scanner Point Clouds, it can load ply format data, and have all basic functions of zoom, pan and rotate. The main function of the program is the possibility to create and save 3D orthofoto from not georeferenced photos that come from different kind of investigation instruments like calibrated photogrammetrik camera, common digital camera, multi-spectral camera and also termography. This allows to study the inquiry object, matching metric 3D informations with radiometric data that could be an important way to better understand the decay phenomenon and to chose the more adapt restoration intervention. Other possible application implemented in the software are rangemaps registration, filtering, sections extraction, shaving light simulation. To demonstrate the functionality of the implemented software are presented some case of studies where we use the new laser scanner prototype SIDART 100 (build from CETMA with knowledge of Enea Frascati Group) for points clouds acquisition.