Additive manufacturing (AM) comes in various types of technologies and comparing it with traditional fabrication methods provides the possibility of producing complex geometric parts directly from Computer-Aided Designs (CAD). Despite answering challenges such as poor workability and the need for tooling, the anisotropy of AM constructions is the most serious issue encountered by their application in industry. In order to enhance the microstructure and functional behavior of additively fabricated samples, post-processing treatments have gained extensive attention. The aim of this research is to provide critical, comprehensive, and objective methods, parameters and results’ synthesis for post-processing treatments applied to AM builds obtained by 3D printing technologies. Different conditions for post-processing treatments adapted to AM processes were explored in this review, and demonstrated efficiency and quality enhancement of parts. Therefore, the collected results show that mechanical characteristics (stress state, bending stress, impact strength, hardness, fatigue) have undergone significant improvements for 3D composite polymers, copper-enhanced and aluminum-enhanced polymers, shape memory alloys, high-entropy alloys, and stainless steels. However, for obtaining a better mechanical performance, the research papers analyzed revealed the crucial role of related physical characteristics: crystallinity, viscosity, processability, dynamic stability, reactivity, heat deflection temperature, and microstructural structure.

Composites made from fiber-reinforced polymers (FRPs) are a crucial and highly adaptable category of materials widely utilized in numerous fields. Their flexibility and the range of criteria for classification enable the creation of tailored solutions to address distinct requirements in sectors such as civil engineering, aerospace, automotive, and marine, among others. The distinguishing characteristics of FRP composites include the type of reinforcing fiber used, the composition of the matrix material, the employed manufacturing process, the orientation of the fibers, and the specific end-use application. These classification variables offer engineers a versatile structure to determine and select the most appropriate materials and production techniques for their specific needs. Furthermore, the present study aims to reunite the criteria of classification for FRPs and specific manufacturing technologies of FRPs, such as conventional ones (matched die molding, contact molding), automated ones (filament winding, tape lay-up, and fiber placement), and advanced ones (electrospinning and additive manufacturing),with the chronological development of FRPs, insights on material characteristics, and comprehensive design guidelines based on their behavior in different environments of use.

In recent years, there has been a growing interest in the field of 3D printing technology. Among the various technologies available, fused deposition modeling (FDM) has emerged as the most popular and widely used method. However, achieving optimal results with FDM presents a significant challenge due to the selection of appropriate process parameters. Therefore, the objective of this research was to investigate the impact of process parameters on the tribological and frictional behavior of acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA) 3D-printed parts. The design of experiments (DOE) technique was used considering the input design parameters (infill percentage and layer thickness) as variables. The friction coefficient values and the wear were determined by experimental testing of the polymers on a universal tribometer employing plane friction coupling. Multi-response optimization methodology and analysis of variance (ANOVA) were used to highlight the dependency between the coefficient of friction, surface roughness parameters, and wear on the process parameters. The optimization analysis revealed that the optimal 3D printing input parameters for achieving the minimum coefficient of friction and linear wear were found to be an infill percentage of 50% and layer thickness of 0.1 mm (for ABS material), and an infill percentage of 50%, layer thickness of 0.15 mm (for PLA material). The suggested optimization methodology (which involves minimizing the coefficient of friction and cumulative linear wear) through the optimized parameter obtained provides the opportunity to select the most favorable design conditions contributing to a more sustainable approach to manufacturing by reducing overall material consumption.

The increasing demand for sustainable packaging materials has driven the exploration of biodegradable alternatives to synthetic plastics. This study investigates the thermal and mechanical properties of starch-based films plasticized with varying concentrations of glycerol and sorbitol. Cornstarch films were prepared with glycerol and sorbitol plasticizers in different ratios, and their physical characteristics, including swelling index, water solubility, and thermal stability, were assessed using Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and tensile testing. The results indicate that the incorporation of plasticizers significantly influenced the films’ properties. Films with higher glycerol content exhibited greater flexibility and solubility, while sorbitol-plasticized films showed enhanced thermal stability. The combination of both plasticizers yielded films with balanced properties suitable for food packaging applications. This study demonstrates the potential of glycerol and sorbitol as effective plasticizers in developing biodegradable starch-based films, offering a promising alternative to conventional plastic packaging.

Increasing environmental concerns and the need for sustainable materials have driven a focus towards the utilization of recycled polylactic acid (PLA) in additive manufacturing as PLA offers advantages over other thermoplastics, including biodegradability, ease of processing, and a lower environmental impact during production. This study explores the optimization of the mechanical properties of recycled PLA parts through a combination of experimental and machine learning approaches. A series of experiments were conducted to investigate the impact of various processing parameters, such as layer thickness and infill density, as well as annealing conditions, on the mechanical properties of recycled PLA parts. Machine learning algorithms have proven the possibility to predict tensile behavior with an average error of 6.059%. The results demonstrate that specific combinations of processing parameters and post-treatment annealing differently improve the mechanical properties (with 7.31% in ultimate tensile strength (UTS), 0.28% in Young’s modulus, and 3.68% in elongation) and crystallinity (with 22.33%) of recycled PLA according to XRD analysis, making it a viable alternative to virgin PLA in various applications such as sustainable packaging solutions, including biodegradable containers, clamshell packaging, and protective inserts. The optimized recycled PLA parts exhibited mechanical properties and crystallinity levels comparable to those of their virgin counterparts, highlighting their potential for reducing environmental impact and saving costs. For both as-built and annealed samples, the optimal settings for achieving high composite desirability involved a 0.2 mm layer thickness, with 75% infill for the as-built samples and 100% infill for the annealed samples. This study provides a comprehensive framework for optimizing recycled PLA in additive manufacturing, contributing to the advancement of sustainable material engineering and the circular economy.

The energy transition is a subject of significant interest in the countries of the European Union, and the involvement of public authorities is remarkable. Unlike previous energy transitions, this process is politically driven, the efforts of public authorities being secondary to the actions of companies whose guidelines are based on stability at the European level through strategies and directives. This paper aims to provide an overview of the current evolution of energy security status in the European Union and in Romania, with reference to global efforts to achieve climate neutrality through the energy transition. The historical method was used in the elaboration of the material, in order to outline the current energy security policies in terms of sustainability, both environmental and social. The logical method was used in order to emphasize the cause–effect relationship between economic processes in the energy sector. The use of bibliometric analysis demonstrated the importance of the topic of energy transition in scientific literature, but it also demonstrated the increasing interest of researchers in subjects related to energy security and energy poverty in the context of this new transition. By using the graphical method, statistic data and their evolution were highlighted in detail for the present study. The results of the articles are embodied in an approach that aims to focus on economic and social factors that determine the capacity of states to support the EU’s independence from a single supplier in the current context of conflict. The authors conclude by anticipating massive challenges in achieving the environmental objectives of the European Green Deal, as well as by highlighting the issue of energy poverty as a social factor influencing global strategic decisions.