The exploration of the Moon necessitates sustainable habitat construction. Establishing a permanent base on the Moon requires solutions for challenges such as transportation costs and logistics, driving the emphasis on In-Situ Resource Utilization (ISRU) techniques including Additive Manufacturing. Given the limited availability of regolith on Earth, researchers utilize simulants in laboratory studies to advance technologies essential for future Moon missions. Despite advancements, a comprehensive understanding of the fundamental properties and processing parameters of sintered lunar regolith still needs to be studied, demonstrating the need for further research. Here, we investigated the fundamental properties of lunar regolith simulant material with respect to the stereolithography-based AM process needed for the engineering design of complex items for lunar applications. Material and mechanical characterization of milled and sintered LHS-1 lunar regolith was done. Test specimens, based on ASTM standards, were fabricated from a 70 wt% (48.4 vol %) LHS-1 regolith simulant suspension and sintered up to 1150 degrees C. The compressive, tensile, and flexural strengths were (510.7 +/- 133.8) MPa, (8.0 +/- 0.9) MPa, and (200.3 +/- 49.3) MPa respectively, surpassing values reported in previous studies. These improved mechanical properties are attributed to suspension's powder loading, layer thickness, exposure time, and sintering temperature. A set of regolith physical and mechanical fundamental material properties was built based on laboratory evaluation and prepared for utilization, with the manufacturing of complex-shaped objects demonstrating the technology's capability for engineering design problems.

The solidification and molding of lunar regolith are essential for constructing lunar habitats. This study introduces an innovative lunar regolith molding technique that synergistically combines solar concentration, flexible optical fiber bundle energy transfer, and powder bed fusion. A functional prototype is developed to validate the proposed scheme. Systematic experiments including fixed beam spot melting, line melting, surface melting, and body melting are conducted using simulated basalt lunar regolith. Through in-situ observation of the melt pool's formation, evolution, and expansion dynamics, we identify a sequential transformation mechanism on the powder bed's surface: initial curling evolves into detachment from the bed, subsequent incorporation into a molten droplet, and ultimate solidification. A comprehensive evaluation of density and mechanical properties across multiple parameter combinations reveals that energy flux density of 3.33 MW/m2 with a scan speed of 30 mm/min, inter-track spacing of 3 mm, and layer thickness of 2 mm enables the production of structurally integral samples with continuous morphology. The resulting specimens demonstrate a maximum compressive strength of 4.25 MPa and a density of 2.31 g/cm3. This solar-powered additive manufacturing approach establishes a viable reference framework for large-scale on-site construction of lunar research stations.

This study systematically examines the influence of joints on the mechanical properties of loess, highlighting the impact of joint dip angles on soil deformation and failure mechanisms. By employing an innovative layered compaction method to prepare jointed specimens, and conducting comparative experiments with different simulation materials (wax paper, rice paper, and plastic film), a series of controlled indoor triaxial compression tests were performed. The key findings are as follows: (1) The joint dip angle plays a decisive role in the evolution of failure mode, with five typical failure mechanisms identified based on fracture characteristics: shear failure, sliding failure, conjugate shear failure, sliding-shear failure, and sliding-conjugate shear failure. (2) The weakening effect of joints exhibits confining pressure dependency: Under low confining pressure (50 kPa), jointed specimens demonstrate increased axial displacement and a reduced shear strength attenuation ratio. (3) Mechanical parameters are significantly influenced by the dip angle: When the joint dip angle falls within the critical dip range of 60 degrees-75 degrees, both cohesion and internal friction angle reach their minimum values, forming zones of weakened mechanical properties. (4) A comparative analysis of simulation materials indicates that single-layer rice paper, due to its optimal thickness and tensile strength, effectively replicates the contact behavior of natural joint surfaces. This study establishes the quantitative relationship between joint geometric parameters and mechanical responses, providing an experimental basis for the engineering geological assessment of loess.

Hazardous waste from metal processing industries increases heavy metal contamination in ecosystems, threatening environmental health and regional sustainability. This study suggests a resilient and human-centered environmental monitoring approach that incorporates machine learning and decision analytics to address these challenges in line with Industry 5.0's goals. By utilising a PRINCIPAL COMPONENT REGRESSION (PCR)-based predictive model, the approach addresses variability in environmental data, predicting levels of heavy metals like lead, zinc, nickel, arsenic, and cadmium, frequently beyond regulatory thresholds. The suggested PCR-based model outperforms conventional models by lowering mean absolute error (MAE) to 2.9339, mean absolute percentage error (MAPE) to 0.0358, and nearly the same mean square error (MSE). This study introduces a more interpretable and computationally efficient alternative to existing predictive models by introducing a novel integration of PCR with machine learning for environmental monitoring. By predicting and optimising environmental outcomes, validation against test datasets confirmed its ability to optimise impurity control. After process adjustments, the average concentrations of lead, nickel, and cadmium were reduced from 13.23 to 11.26 mg/L, 2.83 to 2.70 mg/L, and 2.15 to 1.88 mg/L, respectively. This research supports sustainability, resilience, and decisionmaking aligned with Industry 5.0, offering scalable solutions and insights for global industries.HighlightsChemical plants' environmental risk is evaluated using a machine learning algorithmFor better monitoring, the PCR method forecasts process variables and interactionsIt identifies the key factors that affect the environmental risks in soil and waterAs a result, the local ecosystem's levels of toxic metals have notably decreasedInsights for managing environmental risks aligned with Industry 5.0 principles

Poly(butylene adipate-co-terephthalate) (PBAT) is a biodegradable polymer derived from fossil-based raw materials. Combined with poly(lactic acid) (PLA), a major material used in 3D printing, PBAT provides mechanical properties that are particularly attractive for applications requiring flexible 3D-printed objects. However, blends with high PBAT content in fused filament fabrication (FFF) are currently not well-documented, and optimal printing parameters remain unclear for advancing this field. This study aims to address this gap by first exploring the extrusion of filaments at different temperatures, followed by analyzing the printing conditions for PBAT/PLA blends to enhance their spectrum of applications. Using a commercial blend, Ecovio (R) (86 mol% PBAT), this paper demonstrates the feasibility of employing high PBAT content in the additive manufacturing process. Printing parameters such as nozzle temperature and speed were assessed based on the visual quality and mechanical properties of the specimens. The results indicate that extruding at 120 degrees C yields smoother filaments with adequate diameter for FFF applications. Regarding 3D-printing analysis, variations in parameters did not significantly impact elongation at break. However, increasing the nozzle temperature from 180 to 210 degrees C and the printing speed from 50 to 80 mm/s resulted in a 29% increase in tensile strength and a 77% increase in the modulus of elasticity of the 3D-printed specimens which is attributed to better interlayer adhesion. Therefore, high PBAT content blends can improve the performance of 3D-printed materials, and parameters must be optimized to exploit their effectiveness fully across various industrial uses.Highlights Extrusion temperature variations minimally affect PLA/PBAT thermal properties. Higher nozzle temperature and speed significantly improve mechanical properties. Optimal printing conditions for high PBAT blends enable flexible materials. PBAT blends show potential for enhanced 3D printing performance in all sectors.

Excavated soil from widescale tunneling and excavation can be used in 3D-printed constructions. This research investigates the feasibility of 3D printing using geopolymer stabilized excavated soil (GP-E) containing 42% clay rich in kaolinite minerals. At dosages 0.50-1.5 wt%, sucrose is added to control the hydration and timedependent rheological properties, enabling adequate open printing time (OPT) for large-scale printing. Experimental findings show that 1% and 1.5% sucrose addition to GP-E offers OPT of 130 min and 170 min respectively compared to 32 min for GP-E. By enabling better dispersion, the addition of sucrose allows smooth extrusion with shape retention of 90 - 92% at a lower NaOH solution-to-binder ratio (0.68) than GP-E (0.75). Sucrose and clay (in the soil) act synergistically to reduce the time-dependent static yield stress but maintain it at an adequate level of 5-8 kPa required for stacking up the layers without collapse. Flow retention and thixotropy are maintained at 100% during the printing window, which balances extrusion and buildability. As a result, the sucroseGP-E mix could be built up to a height of 1.05 m compared to 0.19 m for GP-E. 1 % sucrose-added GP-E possesses 28 - 40% and 70% higher wet compressive strength and inter-layer bonding respectively compared to GP-E depending on the loading direction. These are linked to the refinement of capillary porosity and a 13-15% reduction in shrinkage. In summary, the findings present a potential route for controlling the printing time of geopolymer-stabilized earthen materials while reducing the embodied carbon and enhancing the mechanical performance.

The escalating global crisis of plastic waste necessitates innovative and sustainable approaches to its management. This study explores a novel method; the transformation of discarded plastic materials into high quality 3D printing filaments, offering a promising solution to this pervasive environmental challenge. This review paper delves into the prospects of leveraging plastic waste recycling for the production of 3D printing filaments, thereby advancing the cause of sustainable additive manufacturing. The investigation encompasses a comprehensive examination of the recycling process, encompassing waste collection, sorting, and filament extrusion. The outcomes of this study underscore the substantial potential of recycling plastic waste for 3D printing filaments as a sustainable alternative to conventional manufacturing. This review also delves into the polymer degradation phenomenon, assessment of properties of recycled polymers, and environmental impact assessment, conducting a comparative analysis with traditional filament production methods. This paper advances the application of recycling plastic waste for 3D printing filaments, offering a tangible and immediate response to the global plastic waste crisis.

In-Situ Resource Utilisation (ISRU) is increasingly being seen as a viable and essential approach to constructing infrastructure for human habitation on the moon. Transporting materials and resources, from Earth to the Moon, is prohibitively expensive and not sustainable for long-term, large-scale development. Various fabrication technologies have been investigated in recent years, designed for extra-terrestrial exploration and settlement. This review presents a comprehensive study on the development of several sintering techniques of lunar regolith simulant to demonstrate its feasibility for ISRU on the moon. Various critical processing parameters are evaluated in pursuit of creating a structural material that can withstand the extreme lunar environment. Key outcomes are summarised and assessed to provide insight into their viability. Finally, current challenges are addressed and potential improvements, and avenues for further research, suggested.

Human space exploration missions in the near future will inevitably demand beyond-Earth manufacturing capacity to develop critical subsystems utilising in situ resources. Therefore, to find an alternative solution to the logistics challenges of long-duration space missions, an on-site component fabrication process utilising indigenous resources on the Moon and Mars will be economical and play a crucial role in ensuring the expansion of succeeding missions to deep space. Additive manufacturing (AM) exhibits excellent potential to develop intricate components with functional and tailorable properties at various scales. To assess the potential of AM, an artificial Mars soil has been processed to formulate stable aqueous paste containing less organics (1.5% versus typically 30-40%) amenable to resource-efficient 3D printing. The formulated paste was utilised to fabricate a range of solid and porous designs of various shapes and sizes using a layer-wise material extrusion method for the first time. The additively manufactured components sintered at 1100 degrees C for 2 h exhibited an average relative permittivity (epsilon r) = 4.43, dielectric loss (tan delta) = 0.0014, quality factor (Q x f) = 7710 GHz and TCf = - 9. This work not only demonstrates progress in paste additive manufacturing but also illustrates the potential to formulate eco-friendly ink that can deliver components with functional properties to support long-term space exploration utilising local resources available on Mars.

There is an increasing demand for sustainable construction materials to address the challenges posed by the environmental impact of the built environment (BE), which is driven by climate change, population growth, and urbanization. Conventional construction materials like cement contribute significantly to carbon emissions during production, transport, use, and disposal phases, and their poor thermal conductivity hinders efforts to maintain comfortable indoor environments. To address these challenges, there is an urgent need for innovative, locally sourced thermal insulation materials specifically designed for regions with extreme climates and high energy demands to maintain building comfort. This research explores synthesizing novel, environmentally friendly building materials using locally sourced date palm fiber waste and clay. The study also investigates the developed material's 3D printing (3DP) capabilities and optimizes its printing parameters with lab-scale prototypes. Additionally, thermo-mechanical characterization is conducted to assess its suitability for built environment applications. Different concentrations, from 1 to 5 wt% of date palm fiber to clay ratio (Dpf/C), were studied regarding microstructural, thermal, and mechanical properties, dimensional accuracy, and feasibility for 3DP of BE structures. Results demonstrated a significant reduction in thermal conductivity by 73%, achieving 0.244 W/mK, and an increase in compressive strength by 106%, reaching 10.9 MPa at 5 wt% Dpf/C. The promising thermomechanical properties of these composites and their suitability for 3DP support their use in real-world applications in the future's sustainable built environment. This scalable methodology can be adapted to regions with similar sustainable local and waste resources, advancing the circular economy.