Pedro Villanueva

CO₂ emissions continue to rise, along with the associated environmental risks. In response, the United Nations has been promoting the adoption of sustainable practices among businesses worldwide. In parallel, an innovative technology known as additive manufacturing (AM) has emerged over the past four decades. This technology has the potential to be more sustainable than conventional manufacturing (CM) technologies. When metals are used as the material, the process is referred to as metal additive manufacturing (mAM). AM technologies have seven process categories, which include metal mAM processes, most notably powder bed fusion (PBF), directed energy deposition (DED), binder jetting (BJT), material extrusion of metal-filled feedstock, and sheet lamination. Among these, PBF and DED are by far the most widely applied metal AM technologies in both industrial practice and academic research. The use of mAM is increasing; however, is it truly more sustainable than CM? Motivated by this question, a systematic literature review (SLR) was conducted to compare the sustainability impacts of mAM and CM across the three dimensions of sustainability: environmental, economic, and social. The evidence shows mixed sustainability outcomes, which are synthesized later in the conclusions. The sustainability comparison is influenced by factors like part redesign with topological optimization (TO), the material and energy mix used, geometric complexity, production volume per batch, and the boundaries adopted. Economic viability remains critical; companies are unlikely to adopt mAM if it proves more expensive than CM as this could threaten its competitiveness. Social impacts are the least studied dimension, and it is difficult to anticipate the changes that might occur because of such a transition.

In this investigation, different natural by-products were used to modify the Particle Size Distribution (PSD) of a soil to evaluate their potential in Stabilized Rammed Earth (SRE) building. Three different mixes were manufactured: (i) a mix composed entirely of a clayey soil, (ii) a mix consisting of mining by-products and clayey soil and (iii) a mix entirely based on mining by-products. Unstabilized and stabilized samples of the mixes were manufactured using two cement dosages (2.5% and 5%), and the samples were tested for Unconfined Compressive Strength (UCS), soaked UCS, and wetting and drying tests. Mining by-products demonstrated significant potential in SRE building, as their addition to the clayey soil resulted in higher UCS values compared to the UCS obtained from clayey soil alone. Unstabilized samples lost their integrity during exposure to water. The inclusion of mining by-products also showed potential as, although the mixes did not fully meet the requirements for soaked UCS and the wetting and drying tests, the mix containing both mining by-products and clayey soil retained its integrity in water, unlike the samples composed solely of clayey soil. M3C5 successfully met the requirements for soaked UCS and the wetting and drying tests, further highlighting the great potential of mining by-products in SRE building.

In this investigation, different natural by-products were used to modify the Particle Size Distribution (PSD) of a soil to evaluate their potential in Stabilized Rammed Earth (SRE) building. Three different mixes were manufactured; (i) a mix composed entirely of a clayey soil, (ii) a mix consisted of mining by-products and clayey soil and (iii) a mix entirely based on mining by-products. Unstabilized and stabilized samples of the mixes were manufactured, using two cement dosages (2.5% and 5%) and the samples were tested to Unconfined Compressive Strength (UCS), soaked UCS and wetting and drying tests. Mining by-products demonstrated significant potential in SRE building, as their addition to the clayey soil resulted in higher UCS values compared to the UCS obtained from clayey soil alone. Unstabilized samples lost their integrity during exposure to water. The inclusion of mining by-products also showed its potential, as although the mixes did not fully meet the requirements of the soaked UCS and the wetting and drying tests, the mix containing both mining by-products and clayey soil retained its integrity in water, unlike the samples composed solely of clayey soil. M3C5 successfully met the requirements of the soaked UCS and the wetting and drying tests, further highlighting the great potential of mining by-products in SRE building.

The use of foam materials in environments where they come into contact with individuals often results in deterioration, necessitating periodic replacements to maintain safety and hygiene standards. Foam, a lightweight, porous plastic formed by aggregated bubbles, possesses excellent impact-absorbing properties; however, its inherent porosity and susceptibility to wear present challenges. This project aims to develop a technological application for repurposing spent polyurethane (PU) foam from leisure facilities into effective impact absorption systems. By focusing on the reuse of deteriorated foam materials, this initiative seeks to minimize environmental impact while leveraging their beneficial technical characteristics. Addressing issues related to foam degradation, this project endeavors to create sustainable solutions by reintegrating spent foam into new systems. This innovative approach promotes sustainability while enhancing safety through the provision of high-quality, impact-resistant elements. Ultimately, this work aims to contribute to environmental conservation and the advancement of effective impact protection measures in leisure facilities.

This chapter explores the latest advancements and methodologies in directed energy deposition (DED-arc) manufacturing. The introduction sets the stage for understanding the significance of these developments in the context of modern manufacturing needs. The discussion includes design strategies for DED-arc, emphasizing topological optimization, functional design, and generative design, alongside the application of artificial intelligence (AI) in enhancing design processes. Innovative approaches to material hybridization are detailed, focusing on both multilayer and in situ techniques for combining different materials to optimize component performance. The paper also covers slicing and pathing, examining slicing strategies, the use of lattice structures, and the implementation of 2D and 3D patterns to improve manufacturing efficiency and product quality. The conclusion summarizes key findings, discusses their implications for the additive manufacturing industry, and suggests potential future research directions in DED-arc technology, highlighting the emerging trends and innovations that are shaping the field.

The utilization of foam in contact with individuals often leads to its deterioration, necessitating periodic material changes to prevent degradation and maintain sanitary conditions. Foam, a porous plastic material formed by an aggregation of bubbles, offers lightweight and impact-absorbing properties, yet its porosity and susceptibility to wear pose challenges. The project's overarching goal is to develop a technological application for repurposing spent foam materials and textile elements from leisure facilities into impact absorption systems. This initiative aims to minimize environmental impact by reusing materials and leveraging their technical characteristics, including those of polyurethanes and textiles. By addressing the challenge of foam deterioration, the project seeks to create sustainable solutions. The development of impact absorption systems will involve the utilization of spent foam, either by reintegrating it into the system after its initial use or combining it with waste textiles. This innovative approach not only promotes sustainability but also enhances safety by ensuring the availability of high-quality impact-resistant elements. Through this endeavor, the project aims to contribute to both environmental conservation and the advancement of effective anti-impact measures in leisure facilities.

The combination of safety belts and rollover protective structures (ROPSs) is key in improving the safety of agricultural tractors in the event of rollover. However, we also have the opportunity to enhance the security provided by each ROPS; one such example is the combination of this safety device with adequate mechanical energy absorbers (MEAs). Inexpensive disc-shaped MEAs can be included in the anchoring points of a ROPS onto the chassis of a tractor. Three configurations of ROPS combined with MEAs were tested during the application of loads that simulated the effects of side rollover in the vehicle. The tested configurations included a blank MEA as a reference case alongside a single MEA and a stack assembly containing both elements. The results of the tests show that both the deformation of the ROPS itself and the strain energy are larger in the case of blank MEAs; thus, there is also a risk that the clearance zone will be infringed upon and that the protective structure will collapse. We can conclude that the implementation of an appropriate MEA in ROPS reduces the deformation of the ROPS itself and its strain energy in cases of vehicle rollover; hence, the safety provided by such protection systems may be improved at a low cost.

The paper introduces an innovative aerospace component production approach employing Wire Arc Additive Manufacturing (WAAM) technology to fabricate near-finished preforms from Ti₆Al₄V titanium. Tensile tests on WAAM Ti₆Al₄V workpieces demonstrated reliable mechanical properties, albeit with identified anisotropic behavior in horizontal samples, underscoring the need for optimization. This alternative manufacturing strategy addresses the challenges associated with machining forged preforms, marked by a high Buy To Fly (BTF) ratio (>10), leading to material wastage, prolonged machining durations, elevated tool expenses, and heightened waste and energy consumption. Additionally, logistical and storage costs are increased due to extended delivery timelines, exacerbated by supply issues related to the current unstable situation. The utilization of WAAM significantly mitigates initial BTF, preform costs, waste production, machining durations, and associated expenditures, while notably reducing lead times from months to mere hours. The novelty in this study lies in the application of Wire Arc Additive Manufacturing (WAAM) technology for the fabrication of titanium aircraft components. This approach includes a unique height compensation strategy and the implementation of various deposition strategies, such as single-seam, overlapping, and oscillating.