Among the several additive manufacturing techniques, fused filament fabrication (FFF) is a 3D printing technique that is fast, handy, and low cost, used to produce complex-shaped parts easily and quickly. FFF adds material layer by layer, saving energy, costs, raw material costs, and waste. Nevertheless, the mechanical properties of the thermoplastic materials involved are low compared to traditional engineering materials. This paper deals with the manufacturing of composite material laminates obtained by the Markforged continuous filament fabrication (CFF) technique, using an innovative matrix infilled by carbon nanofibre (Onyx), a high-strength thermoplastic material with an excellent surface finish and high resistance to chemical agents. Three macro-categories of samples were manufactured using Onyx and continuous carbon fibre to evaluate the effect of the fibre on mechanical features of the novel composites and their influence on surface finishes. SEM (Scanning Electron Microscopy) analysis and acquisition of roughness profile by a confocal lens were conducted. Tensile and compression tests, thermogravimetric analysis and calorimetric analysis using a DSC (differential scanning calorimeter) were carried out on all specimen types to evaluate the influence of the process parameters and layup configurations on the quality and mechanical behaviour of the 3D-printed samples.

Hydrophobic surfaces are highly desired for several applications due to their exceptional properties such as self-cleaning, anti-icing, anti-friction and others. Such surfaces can be prepared via numerous methods including plasma technology, a dry technique with low environmental impact. In this paper, the effect of a one-step sulfur hexafluoride (SF₆) plasma treatment upon the low velocity impact behavior of basalt/epoxy composites has been investigated by using several characterization techniques. A capacitive coupled radiofrequency plasma system was used for the plasma surface treatment of basalt/epoxy composites, and suitable surface treatment conditions were experimentally investigated with respect to gas flow rate, chamber pressure, power intensity, and surface treatment time by measuring the water droplet contact angle of treated specimens. The contact angle measurements showed that treating with SF₆ plasma would increase the hydrophobicity of basalt/epoxy composites; moreover, the impact results obtained on reinforced epoxy basalt fiber showed damage in a confined area and higher impact resistance for plasma-treated basalt systems.

Additive Manufacturing (AM) techniques have recently attracted the attention of scientists for the development of prototypes with complex or particular geometry in a fast and cheap way. Among the different AM processes, the Fused Deposition Modelling process (FDM) offers several advantages in terms of costs, implementation features and design freedom. Recently, it has been adopted to realise auxetic structures, which are characterised by negative Poisson ratio, enhanced mechanical properties, and a higher compression resistance than conventional structures. This review outlines the use of AM processes, in particular FDM, to design and obtain auxetic structures, with the final aim to exploit their applications in different fields. The first part of this work presents a brief classification of auxetic structures and materials. Subsequently, a summary of additive manufacturing processes is presented, focusing on the use of FDM and its limitations. Finally, the studies on the use of additive manufacturing to produce auxetic structures are shown, evidencing the potential of the concurrent combination of a fast prototyping technique such as FDM and the characteristics of polymer- and/or composite-based auxetic structures. Indeed, this new technological field opens the possibility of realising novel structures with integrated smart behaviour, multifunctional properties, compression resistance, and a tailored microstructure and shape.

In recent decades, composite materials have been widely used in several fields. The challenge in recent years has been to find an effective and automatable repair technique for these materials. Low-speed impact tests were carried out on panels made from prepregs in carbon fibre and epoxy resin. An innovative repair technique has been tested by injecting resin into the delamination due to the impact event. After the first impact, some panels were repaired and re-impacted, while others were impacted twice consecutively. The data analysis and damage detection by an ultrasound technique demonstrate that the absorbed energy of the twice-impacted panels is lower than that of the repaired ones, demonstrating a configuration similar to that of the panels impacted only once. The results of this research have demonstrated the effectiveness of the repairs.

Wood has been employed for millennia as a versatile structural material in various applications, from furnishings and household items to components in the automotive, aerospace, and energy sectors. However, its limited strength and toughness often constrain its use in highperformance applications. To address these limitations, numerous densification methods—often relying on aggressive chemical or thermal modifications—have been developed to improve wood’s mechanical properties and dimensional stability under moisture variation. In this study, a sustainable, low-cost hydrothermal densification method using a Teflon-lined system is proposed as a green alternative to conventional alkali-based processes. The investigation compares the effects of traditional alkali treatment and the proposed hydrothermal method on the structural integrity of oak wood cell walls. Various analytical techniques, including Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), and Dynamic Mechanical Analysis (DMA), were employed to evaluate surface color changes, microstructural alterations, and chemical composition of both as received and treated wood samples. Results reveal that the degree of cell wall degradation varies significantly depending on the treatment and temperature. Alkali-treated samples exhibited the most pronounced structural damage, while the hydrothermally treated wood retained a porous microstructure with finer pore distribution. FTIR analysis confirmed hemicellulose degradation in both treatments, indicated by the reduction or disappearance of the C=O absorption peak. Importantly, the hydrothermal method achieved up to a 19.6% increase in storage modulus compared to alkali-treated samples, suggesting improved mechanical performance with lower environmental impact. These findings underscore the potential of the hydrothermal densification process as an environmentally friendly and effective pre-treatment for enhancing wood properties, making it a promising strategy for future integration into composite material manufacturing.

Wood is an attractive renewable material, yet its mechanical performance, dimensional stability, and moisture sensitivity limit its use in structural applications. Conventional densification methods often rely on aggressive alkali solutions or resin impregnation, generating environmental concerns and causing excessive cell-wall degradation. In this study a sustainable hydrothermal densification process for oak wood using only a water–ethanol solution in a sealed Teflon-lined autoclave has been investigated and implemented. Treatment at 195 °C for 80 min selectively degraded hemicelluloses and partially reorganized lignin without compromising the cellulose network, followed by hot-pressing at 100 °C under 5 MPa. The hydrothermally densified oak exhibited a significant improvement in stiffness, with a 125% increase in storage modulus relative to untreated wood and a 19.6% enhancement compared to alkali-treated samples. The findings demonstrated that hydrothermal processing is an efficient, low-impact alternative for producing high-performance densified wood suitable for sustainable construction and composite applications.