This review summarizes recent research advancements in thermoplastic composites used in Fused Deposition Modeling (FDM) processes. Since its development in 1988, FDM has emerged as one of the primary emerging technologies of Industry 4.0, receiving attention in fields such as industrial manufacturing, automotive, aerospace, and others, particularly for rapid prototyping and customization. The intention is to make available a guideline for 3D printing researchers, analyzing the properties and performance characteristics of different polymers and polymeric composites. The review analysis covers various reinforcing agents, including particles/nanoparticles, short fibers, and long fibers, identifying critical parameters of the FDM process which affect printed part quality, integrity and final geometry. Major attention is devoted to the different techniques employed for composite filament fabrication, mostly for structural elements and parts. An extensive overview of various FDM composites and fiber-reinforced composites by polymer matrices such as PLA, ABS, and PEEK is presented, with their mechanical and thermal properties reported for specific applications. Current challenges and prospective future research directions are also outlined, mainly focusing on the enhancement of material performance and sustainability.

Green composites have gained increasing attention in recent years as a sustainable alternative to traditional materials used in marine structures. These composites are made from biodegradable and renewable materials, making them environmentally friendly and reducing the subsequent carbon footprint. This review aims to provide a comprehensive overview of green composites materials and their applications in marine structures. This review includes a classification of the potential fibres and matrixes for green composites which are suitable for marine applications. The properties of green composites, such as their strength and Young’s modulus, are analysed and compared with those of traditional composites. An overview concerning current rules and regulations is presented. The applications of green composites in marine structures are reviewed, focusing on both shipbuilding and offshore applications. The main challenges in a wider application of green composites are also highlighted, as well as the benefits and future challenges.

Dry turning of Ti6Al4V alloy is a hard process due to the low thermal conductivity and flexibility of this difficult-to-machine material, generating very high temperatures in both workpiece and tool cutting edge, rapid tool wear and high vibrations during machining. The use of coolants offers the advantage to reduce the high process temperatures, but is not suitable in a green technology perspective due to its high environmental impact. With the aim to allow for dry turning of Ti6Al4V alloy, monitoring of tool wear during the process is required. To achieve this goal, a cognitive sensor monitoring procedure based on the acquisition and processing of force, acoustic emission and vibration sensor signals is implemented, allowing for an accurate tool wear curve reconstruction