A widespread problem of manufacturing processes is represented by the occurrence of tool wear that can lead to both poor surface finish and poor mechanical properties in the workpiece. This issue affects also additive manufacturing technologies such as the material extrusion technique. In this process, the wear mechanisms of the extrusion nozzle can be severe, in particular when materials with a high abrasive capacity, such as carbon fiber-reinforced polymers, are 3D printed. Despite the significance of this problem, scientific literature lacks systematic evaluations of nozzle wear and its correlation with parts mechanical properties. In this framework, the present paper aims at investigating the effect of the nozzle wear evolution on the mechanical properties of additively manufactured parts in short carbon fiber-reinforced polyamide. To this purpose, 3D printing processes were performed. The time dependence of the nozzle wear was analyzed by interrupting the additive manufacturing process at fixed time intervals. To analyze the effect of nozzle wear on the mechanical performances of printed parts, tensile specimens were 3D printed and tested at room temperature. A reduction in mechanical performances of the printed samples and a worsening in the surface quality were observed with increasing the nozzle wear. Optical microscopy investigation and X-ray computed tomography were used to monitor the external and internal nozzle wear evolution. The surface roughness measurements were performed to evaluate the surface quality of the 3D printed parts. Furthermore, the scanning electron microscopy was used to observe the three-dimensional topography of the longitudinal sections of filament in Carbon PA, at different printing time values, and fractured surfaces of tensile samples. This study can help to better understand nozzle wear and to predict tool service life for industrial applications. In addition, it can prompt future studies focused on the reduction of tool wear.

This study compares the environmental and economic impacts of three manufacturing methods for continuous fiber-reinforced composites: traditional autoclave molding (Scenario 1) and two 3D printing technologies, one using thermosetting resin (Scenario 2) and the other using thermoplastic resin (Scenario 3). Life cycle assessment (LCA) and life cycle cost (LCC) analyses were performed for components with the same geometry, stiffness, and load capacity. Results show that Scenario 1 has the highest environmental impacts, of about 1.87 kg CO₂ eq, primarily due to material waste and energy-intensive curing processes. In contrast, 3D printing minimizes material waste, reducing overall impacts to 1.39 kg CO₂ eq, with the thermoplastic-based composites in Scenario 3 offering additional benefits through recyclability. However, due to their lower mechanical properties, thicker and heavier parts are required in Scenario 3, leading to higher impacts in structural applications. Scenario 2 presents a balanced solution with similar mechanical properties to traditional composites and lower environmental impacts (1.30 kg CO₂ eq). From what concerns the total costs, Scenario 1 resulted as the most costly solution (€ 105.27), while Scenario 3 represents the cheapest alternative (about € 37.89) if high mechanical performances are not necessary. If high mechanical properties are required, the most sustainable alternative both economically and environmentally is represented by Scenario 2. The findings suggest that 3D printing is a promising, cost-effective alternative to traditional methods, particularly for non-structural applications, and point to future improvements in composite manufacturing through material optimization and recycling.

The present work aims to study the effect of printing orientation angle and heat treatment on the mechanical properties and microstructure of 17-4 PH stainless steel 3D-printed parts obtained by the binder jetting process to assess the suitability of the process and material for rapid tooling applications. To this purpose, tensile specimens were printed at different printing orientation angles (0°, 45°, and 90°). Half of the specimens were left in the as-sintered condition after the 3D-printing operation, while the other half of the specimens was subjected to H900 heat treatment. Then, tensile and hardness tests were performed to investigate the macro-mechanical properties as a function of the printing orientation angles and postprocessing thermal treatment. Scanning electron microscopy with energy dispersive X-ray spectroscopy was used to observe the fracture surfaces and microscopical defects on the binder jetting printed parts to evaluate the fracture mechanisms. It was demonstrated that printing orientation angles do not affect the mechanical properties of 3D-printed parts, while a significant improvement in the microstructure and mechanical properties is observed after the H900 heat treatment.

Carbon Fiber Reinforced Polymers (CFRPs) are widely used in aerospace, automotive, and other sectors for their high strength-to-weight ratio and adaptability. In order to reach high mechanical performance and quality for CFRP components in which a thermosetting resin is used, the curing process plays a key role, and the optimal conditions have to be identified. In this context, the present study aims to study the effect of heat-shrinkable tape application on the mechanical performance of CFRP tubular components obtained by a filament winding process. To this purpose, CFRP hoop-wound components were realized with a laboratorial filament winding machine. Half of them were directly cured in a muffle oven, while the other half were cured after the application of heat-shrinkable tape around the external surface of the component. To evaluate the effect of the heat-shrinkable tape use on the mechanical properties of the CFRP wound parts, ring specimens, obtained by the tubular components according to the ASTM D2290 standard, were subjected to ring tensile tests. The thickness uniformity and void content of the components were evaluated by means of X-ray computed tomography, whilst the fracture surfaces were observed using scanning electron microscopy. It was demonstrated that the heat-shrinkable tape application around the external surface of the CFRP tubular components allows for improved mechanical performance of the wound parts due to the enhanced material compaction, resulting in stronger and more cohesive structures characterized by a uniform thickness and reduced void content.

Reducing the weight of aircraft components is a key strategy to improve fuel efficiency and reduce greenhouse gas emissions. Innovative materials such as carbon fiber reinforced polymers (CFRPs) and manufacturing techniques represent a possible solution for improved sustainability in the aerospace sector. In this context, this paper presents the design and the evaluation of the environmental and economic impacts of a CFRP tubular structural component, employed for supporting passenger seats of commercial aircraft, realized with the innovative FW process. At first, a simulation of the winding process was conducted to define the component layers, and then a FEM analysis was performed to identify the optimal layering of the tubular structure to support the defined loads. Subsequently, environmental and economic impacts were evaluated by means of life cycle assessment and life cycle costing methodologies. The comparison between the CFRP tubular structure and traditional aluminum alternative was conducted to identify the most sustainable solution. The analysis showed that the CFRP tubular component resulted in lower environmental impacts than the traditional alternative (i.e., about 70% lower considering the whole life cycle) mainly due to the reduced weight. However, the cost evaluation identified the CFRP alternative as the most expensive solution, with production cost 40% higher than the aluminum alternative.