Martina Panico

Composite structures are increasingly being used across a wide range of industries for applications that require optimised mechanical performance and reduced weight. As the demand for innovative materials grows, research into composite structures manufactured through additive manufacturing is gaining increasing attention, especially with the fused filament fabrication (FFF) technique. In this context, PLA+flax composites printed by FFF are gaining attention for their enhanced mechanical properties and sustainability under specific circumstances. A critical factor affecting the mechanical performance of PLA+flax composites is part thickness, particularly in terms of low-velocity impact resistance. Thicker parts generally offer higher impact resistance and structural integrity, but the challenge for FFF parts lies in optimizing thickness alongside other variables, such as infill strategy. Although several studies have investigated the influence of infill topology or mechanical behaviour of FFF biocomposites, fewer works have simultaneously examined the combined effects of thickness, infill architecture and printing energy consumption for PLA/flax systems. This study demonstrates that increasing thickness does not necessarily improve mass-normalised mechanical performance nor energy-normalized efficiency in FFF PLA+flax composites unless coupled with infill architectures capable of efficient shear transfer. Among the investigated configurations, the 6 mm gyroid structure exhibited the highest penetration energy (16.07 J), slightly outperforming the fully solid configuration despite a lower material fraction. Furthermore, the volumetric specific energy consumption decreased from approximately 66.9 kJ/cm ³ for 2 mm specimens to 25.9 kJ/cm ³ for 6 mm specimens, indicating a substantial improvement in manufacturing efficiency with increasing thickness. Overall, gyroid and hexagonal architectures provided the most favourable balance between impact resistance, lightweight efficiency and energy consumption.

The increasing adoption of polymer additive manufacturing (AM) in functional applications has intensified the need for reliable hole-making strategies, particularly when printed components require mechanical fastening or post-processing. However, the layered architecture of fused-filament fabrication (FFF) parts typically leads to dimensional inaccuracy and thermally induced defects during drilling. This study examines the quality of holes made directly with FFF technology and those obtained through traditional drilling on PLA components produced with two different layer heights (0.20 and 0.28 mm). Additively manufactured holes were analysed via least-squares circle fitting and roundness evaluation, revealing high repeatability but substantial undersizing (>1 mm deviation from the 6.35 mm nominal diameter). CNC drilling tests were then performed under a full-factorial combination of spindle speed and feed rate, assessing thrust force, torque, infrared-based cutting temperature, and burr formation for both top and bottom sample side. Results show that CNC drilling can restore near-nominal dimensional accuracy, but only within a restricted process parameters window. Low feed rates promote severe thermal-viscoplastic deformation, while specific combinations of spindle speed and entry surface strongly influence burr formation.

This study analysed the mechanical performances and the environmental sustainability of hybrid hemp/carbon fibre reinforced polymer composites produced adopting different stacking sequences. In this context, three carbon layers were replaced with hemp ones and were positioned either at the mid-plane of the laminate in a symmetric configuration (S sample) and near to the external side of the composite material in an asymmetric configuration (A-HC sample). Additional full carbon sample (CFRP) and hemp sample (HFRP) were manufactured and used as reference materials. The mechanical behaviour of these materials was investigated through flexural, interlaminar shear and low-velocity impact (LVI) tests, and a cradle-to-grave Life Cycle Assessment (LCA) analysis was performed to quantify their environmental impacts in terms of Global Warming Potential (GWP). The experimental results revealed that hemp/carbon hybridisation in composite systems makes it possible to achieve a trade-off between mechanical performances and sustainability. Some of the investigated hybrid configurations exhibited mechanical properties comparable to conventional CFRPs thanks to strength, stiffness and enhanced energy absorption capability which depend on the stacking strategy and the presence of natural fibres that contribute to the damage mitigation. From an environmental perspective, thanks to numerous advantages in the use of hemp fibres, hybrid solutions significantly reduce the global warming potential compared to CFRPs, confirming that hemp/carbon hybridisation represents a promising strategy to balance structural performance and environmental.

Incremental sheet forming, born as a versatile and cost-effective alternative to traditional procedures to deform incrementally and without dedicated dies flat metal sheets into complex three-dimensional shapes, has recently been gaining attention as a forming technique for polymers and composites. Among these, natural fiber-reinforced thermoplastics have been climbing in popularity because natural fibers are widely available, act as effective polymer reinforcement, and make the composite semi-biodegradable. Through compression molding and using natural woven fabrics, it is also possible to achieve good fiber/matrix coupling without compromising the environmental benefits with chemical coupling agents and/or treatments. This experimental study compares cold incremental and stretch forming processes of flax woven fabric-reinforced polypropylene composites for the manufacture of spherical caps. By considering formability, geometrical accuracy, forming forces, power, and energy consumption, the study highlights the effectiveness of incremental forming applied to these biobased composites, without resorting to full counter dies and heating stages, to manufacture components with increased mechanical performance.

Drilling is fundamental to the assembly of aerospace structures, where millions of fastening holes must meet stringent structural and geometric requirements. Despite significant technological advances, hole quality remains sensitive to nonlinear and stochastic interactions between mechanics, thermal effects, tribology, and structural configuration. This review consolidates recent advances in intelligent drilling, focusing on how sensors and artificial intelligence (AI) are integrated to enable process understanding, prediction, and control. In-process monitoring modalities (e.g., cutting forces/torque, vibration, acoustic emission, motor current/active power, infrared thermography, and vision) are examined with respect to signal characteristics, feature design, and modelling choices for real-time anomaly detection, tool condition monitoring, and phase/interface recognition. Predictive quality modelling of burr, delamination, roughness, and roundness is discussed across statistical learning, kernel methods, and neural and hybrid models. Offline parameter optimisation via surrogate-assisted and evolutionary algorithms is considered alongside adaptive control strategies. Practical aspects of robotic drilling and multifunctional end-effectors are highlighted as enablers of embedded sensing and feedback. Finally, cross-cutting challenges (e.g., limited, heterogeneous datasets and model generalisability across materials, tools, and geometries) are outlined, together with research directions including curated multi-sensor benchmarks, multi-source transfer learning, physics-informed machine learning, and explainable AI to support trustworthy deployment in aerospace manufacturing.

Additive Manufacturing (AM) has revolutionized industrial production, particularly in the aerospace, biomedical, and automotive sectors. Among AM technologies, Laser-Powder Bed Fusion (L-PBF) is a widely adopted process for fabricating metallic components due to its ability to produce near-net-shape parts with tailored mechanical properties. However, optimizing SLM process parameters remains a challenge, as factors such as layer thickness, scanning strategy, build orientation, position on the build plate, and laser beam overlap conditions significantly influence the mechanical performance of printed components. This study investigates the combined effects of these key parameters on the tensile and microhardness properties of SLM-fabricated AlSi10Mg components. Results show that reducing layer thickness from 60 to 30 µm increases both tensile strength and elongation at break, owing to finer microstructures and reduced internal defects. Samples built with 0° orientation exhibit a higher Young’s modulus but lower ductility compared to 90°-oriented ones, while the build plate position affects microhardness, with samples in the Z1 zone showing the highest values. Overlapping scan strategies lead to increased residual stresses and microstructural heterogeneity, particularly reducing ultimate tensile strength (UTS) and elongation in 0°-oriented samples. In contrast, 90°-oriented samples demonstrate a finer microstructure that mitigates overlap-induced embrittlement. Furthermore, the UTS/microhardness (HK) ratio decreases under overlapping conditions, indicating a decline in mechanical reliability. These findings provide quantitative insights into how process-induced microstructural inhomogeneities affect mechanical performance, offering clear guidelines for balancing production speed and structural integrity in the industrial-scale manufacturing of AlSi10Mg components.

Polylactic acid (PLA) is a biodegradable polymer with growing industrial appeal, but its inherent brittleness, limited thermal stability, and poor impact resistance hinder its use in demanding applications. This study explores the development of PLA-based biocomposites incorporating a range of functional additives and reinforcements — including polyethene glycol (PEG), polyamide 11 (PA11), lauryl peroxide, Dellite 67G nanoclay, hemp chips, and basalt short fibres — to enhance thermal and mechanical performance. The formulations were prepared through melt blending using a twin-screw extruder and subsequently processed via compression molding into test specimens. Thermal analysis revealed that Dellite nanoclay significantly enhanced crystallinity (up to 75%), while PA11 and hemp disrupted the crystalline structure, reducing thermal stability. Mechanical testing showed that 5 wt.% Basalt fibers increased tensile and flexural modulus by over 36%, and lauryl peroxide promoted remarkable ductility, increasing elongation at break by 381%. Conversely, PA11 caused severe embrittlement, reducing tensile strength by 67%. Impact tests highlighted the effectiveness of peroxide modification, which more than doubled the absorbed impact energy, while moderate basalt fiber content offered a balanced improvement in stiffness and toughness. These findings confirm that targeted combinations of fillers and additives, along with careful processing, can tailor PLA performance for advanced applications, although compatibility and filler dispersion remain critical factors.