Tommaso Verdini

Masked Stereolithography is an additive manufacturing technology widely adopted for industrial and biomedical applications due to its high accuracy and surface quality. Nevertheless, the combined effects of process parameters on mechanical performance and environmental sustainability remain insufficiently explored. This study presents an integrated assessment of the mechanical properties and environmental impacts of printed components, aiming to identify optimal printing conditions. Specimens were produced using a commercial photocurable resin by varying exposure time (4–12 s), layer thickness (0.01–0.09 mm), and LED light intensity (50–100%), following a Box–Behnken Design of Experiments with 15 printing conditions. Tensile and flexural properties were evaluated according to ASTM D638 and ASTM D790 standards, while energy consumption during printing and post-processing was experimentally measured. Non-linear multiple regression models were developed to predict mechanical properties and energy consumption, and a cradle-to-gate Life Cycle Assessment was performed in compliance with ISO 14040–44 standards using Global Warming Potential as the impact category. Results indicate that longer exposure times and higher LED intensities improve tensile and flexural strength and stiffness by enhancing polymer cross-linking, although diminishing returns occur at higher levels. Reduced layer thickness increases mechanical performance but leads to higher energy consumption and environmental impacts due to extended printing times. The regression models showed high predictive accuracy (R ² > 96%, MAPE < 8%). Life Cycle Assessment results reveal that the material phase contributes up to 90% of total environmental impacts, while intermediate layer thicknesses (~ 0.05 mm) provide the best trade-off between mechanical performance and sustainability. This work provides practical guidelines for optimizing Masked Stereolithography process parameters toward sustainable additive manufacturing.

Fiber-reinforced polymer composites are widely used in industrial applications due to their high specific mechanical performance. In particular, carbon fiber-reinforced polymers (CFRPs) are most commonly used for automotive and aerospace sectors, but their production is energy-intensive and associated with relevant environmental impacts. Therefore, the interest in natural fibers is growing. Among them, basalt fibers are used as reinforcement of polymer matrix composites since the basalt fiber-reinforced polymers (BFRPs) exhibit good mechanical properties combined with a low ecological footprint. In this context, the present study provides a comparative experimental evaluation of CFRP and BFRP tubular components realized by means of a hoop filament winding process (winding angle equal to 88°). Radial and axial compression tests were performed according to ASTM D2412 and ASTM D695 standards to assess pipe stiffness, maximum compressive stress, and failure mechanisms. It was demonstrated that the fiber type strongly influences compressive behavior and damage mechanisms. Furthermore, the main results show that CFRP components are characterized by the highest pipe stiffness, approximately equal to 8.9 MPa with respect to 6.0 MPa of BFRP ones, while BFRP samples demonstrate a more elastic and progressive deformation behavior under radial loading. Both materials exhibit similar peak stress values under axial compression tests, equal to about 60 MPa, due to the load direction, which is perpendicular to the fiber orientation; thus, the mechanical properties are assimilable to those of the matrix.

The use of composite materials and specifically of Fiber Reinforced Polymers (FRP) is continuously increasing in structural applications due to their high strength-to-weight ratio. From an environmental perspective, composites still face relevant challenges due to impactful petroleum-based matrices and large amounts of waste generated during manufacturing processes. This study proposes the reuse of FRP machining waste as filler in Masked Stereolithography (M-SLA) 3D printing. Scraps from FRP laminates, obtained during drilling operations, were incorporated into a photocurable resin and used to print tensile and flexural specimens with increasing filler contents (0–5 wt%) and mechanical characterization tests were carried out. A cradle-to-grave Life Cycle Assessment (LCA) was performed to quantify the potential environmental benefits associated with the reduced use of virgin resin. Results show that the use of recycled FRP waste leads to a loss of tensile strength and stiffness (up to 61% and 21% respectively) but it also provides a reduction in Global Warming Potential (about 2% at 5 wt% filler). This demonstrates that the proposed strategy can improve the sustainability of 3D-printed components, especially for non-structural applications.

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.

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.

The present paper aims at studying the environmental and economic impacts of an innovative Filament Winding (FW) process used to realize a tubular shape structural component in Carbon Fiber Reinforced Polymer (CFRP). To this purpose, the Life Cycle Assessment (LCA) and Life Cycle Costing (LCC) methodologies were applied using a “from cradle to grave” approach. Specifically, a towbar used for aircraft pushback was considered as case study. All phases of the life cycle of the analyzed component were included (from the raw materials extraction to the disposal phase). The comparison between the CFRP towbar investigated and a traditional one in aluminum alloy was performed. The LCC analysis was conducted by considering all costs associated with the automated filament winding process, from the initial investment costs. For all the considered impact categories, the CFRP towbar showed the lowest environmental impacts, mainly due to both the reduced weight and service life fuel consumption. The cost and carbon footprint of the innovative component were associated with raw materials use.