Search Results (293)

This study investigates the torsion characteristics of injection-molded flexural hinges manufactured from common polymers and plastic-based composites. The compliant mechanism provides a nearly constant torque over a specific rotational period. The flexural hinges are created via the injection molding technique, which has the advantage of mass production and low price. The injection plastics are pure polypropylene (PP), acrylonitrile butadiene styrene (ABS), and polyamide 6 (PA6), and the injection composites are PA6 combined with glass fibers. The torsional moment of the ABS flexural hinge ranges from −0.2 to 0.94 N∙m. The torsional moment of the PP polymer typically ranges from −0.6 to 0.8 N∙m. The torsional moment of the PA6 polymer ranges from −0.2 to 1.0 N∙m. Interestingly, the torsional moment diagram for this polymer is comparable to that of ABS, with a stable pattern in both positive and negative ranges. Furthermore, in other words, the PP flexural range is greater than the ABS range. Both ABS and PA6 flexural hinges have a higher level of stability compared to the PP one due to the higher elastic modulus and higher strength of these polymers than the PP polymer. The PP flexural hinge has the lowest negative torsional moment (−0.6 N∙m) compared to ABS and PA hinges. PA6 flexural hinges also have the most stable torsional moment compared to pure polymer varieties. Adding 5% to 10% fiberglass (FG) significantly improves the torsional moment of composite flexural hinges. More flexural hinges from different polymer types should be investigated. Further research should conduct some statistical analysis to clarify the variations between the torques for the various materials. The findings improve our understanding of plastic flexure hinges and expand their applicability. Full article

Nowadays, fiber optic cables are a strategic issue because of their importance in telecommunications. Due to the densification of optic cables and the reduction in polymeric layer thickness, the flammability of the external sheath has to be improved. Three novel flame-retardant compositions using phosphate low-melting glasses (LMGs) as aluminum trihydrate (ATH) synergist were assessed in a polyethylene–ethylene vinyl acetate (PE-EVA) matrix. It was highlighted that LMG at a 10 wt% content reduced the peak and mean value of heat release rate (HRR), respectively, to 142 and 90 kW/m² corresponding to 52% and 42% reduction compared to ATH only. Potassium phosphate LMG was shown to perform better than sodium or zinc phosphate LMG. The improvement was assigned to the formation of an expanded mineral layer at the surface of the material during combustion that acts as a thermal shield slowing down the pyrolysis rate. The structural analysis revealed that the presence of alkaline cations in glasses led to short phosphate chains that resulted in low softening point and low-viscosity liquid. It was evidenced that under heat exposure the melted glass is likely to flow between the dehydrating ATH particles, creating a cohesive layer that expands. Additionally, interactions between ATH and LMG were also evidenced. The new crystalline species may also play a role in the cohesion of the layer. Full article

Internal insulation plasters enable historic building renovation without altering the external appearance of the wall. However, the use of internal insulation must be verified case-by-case through dynamic hygrothermal simulation, and the influence of input parameters on the results is not always clear. This paper aims to (i) characterize a new lime-based insulating plaster with expanded recycled glass and aerogel through laboratory measurements, (ii) assess the damage criteria of the plaster under different boundary conditions through dynamic simulations, and (iii) identify the most impactful design conditions on the relative humidity behind insulation. This innovative plaster combines highly insulating properties (thermal conductivity of 0.0463 W/mK) with good capillary activity while also integrating recycled components without compromising performance. The relative humidity behind insulation remains below 95% in most simulated scenarios, with cases above this threshold found only in cold climates, particularly under high internal moisture loads. The parametric study shows that (i) in the analyzed stones, the thermal conductivity variation of the existing wall has a greater effect on the relative humidity behind insulation than the variation of the vapor resistance factor, (ii) the effect of insulation thickness on the relative humidity behind insulation depends on the difference in thermal resistance of the insulation and existing masonry layers, and (iii) internal moisture load and external climate directly impact the relative humidity behind insulation. Full article

Thermoset fibre-reinforced composites are widely used in high-end industries, but a growing demand for more sustainable and recyclable alternatives conveyed the research efforts towards thermoplastics. To expand their usage, new approaches to their manufacture and mechanical performance must be tackled and tailored to each engineering challenge. The present study designed, manufactured and tested advanced multi-layer laminated composites of thermoplastic polypropylene prepreg reinforced with continuous woven fibreglass with interlayer toughening through thermoplastic polyurethane elastomer (TPU) layers manufactured by fused filament fabrication. The manufacturing process was iteratively optimized, resulting in successful adhesion between layers. Three composite configurations were produced: baseline glass fibre polypropylene (GFPP) prepreg and two multi-layer composites, with solid and honeycomb structured TPU layers. Thermal and mechanical analyses were conducted with both the polyurethane elastomer and the manufactured laminates. Tensile testing was conducted on additively manufactured polyurethane elastomer specimens, while laminated composites were tested in three-point bending. The results demonstrated the potential of the developed laminates. TPU multi-layer laminates exhibit higher thermal stability compared to the baseline GFPP prepreg-based composites. The addition of elastomeric layers decreases the flexural modulus but increases the ability to sustain plastic deformation. Multi-layer laminate composites presenting honeycomb TPU layers exhibit improved geometric and mechanical consistency, lower delamination and fibre breakage, and a high elastic recoverability after testing. Full article

The current study presents the development and optimisation of foam glass manufactured from recycled glass shards and expanded ground perlite, targeting enhanced structural and thermal performance for sustainable building applications. By investigating various particle size fractions (“125 μm”, “250 μm”, “500 μm”) and sintering temperatures (800–850 °C), we achieved a foam glass with superior compressive strength and uniform porosity. Notably, samples utilising a homogeneous 500 μm particle fraction sintered at 850 °C exhibited the highest compressive strength of 2.17 MPa, coupled with open porosity uniformity and stable structural matrix formation. Density values in this fraction decreased from 321 to 263 kg/m³, indicating effective foaming and well-developed open porosity that balances mechanical integrity and thermal insulation. The optimised thermal regime minimised crystalline phase formation, preserving low thermal conductivity and mechanical stability. Compared to heterogeneous composites, the homogeneous fractions demonstrated significantly improved strength-to-porosity ratios, ensuring predictable mechanical performance and competitive thermal insulation properties. These findings underline the material’s potential as a cost-effective, environmentally friendly insulation solution that meets or exceeds existing standards, with promising applications in energy-efficient construction. Full article

As the demand for high-quality visual experiences continues to grow, advanced imaging technologies offering higher realism and immersion are being increasingly integrated into various fields. Among them, glasses-free 3D imaging has gained significant attention for enhancing user experience without the need for wearable equipment. Holoscopic 3D imaging systems, known for their capability to reconstruct true volumetric images and provide natural depth perception, have emerged as a promising direction within this domain. Originating from early 20th-century optical theory, holoscopic imaging has evolved in response to diversified application scenarios and rapid advancements in micro-optics and computational imaging. This paper presents a representative historical overview of the development of holoscopic 3D systems, their unique features compared to other glasses-free 3D technologies, and their expanding presence in these applications. By analyzing representative use cases across sectors such as healthcare, education, cultural heritage, and media entertainment, this review offers a broader and more detailed perspective on the deployment of holoscopic 3D systems. Furthermore, this paper discusses current technical challenges and outlines future research directions, with a particular focus on the transformative potential of holoscopic 3D in the creative and entertainment industries. This study aims to provide both theoretical grounding and practical insights to support the next generation of holoscopic 3D imaging technologies. Full article

Three-dimensional concrete printing (3DCP) is advancing rapidly, yet its sustainable adoption requires alignment with circular-economy principles. This study evaluates the substitution of natural aggregates with recycled constituents, 3DCP waste, brick debris, glass cullet, mixed rubble, fly ash, and slag, and the use of lightweight fillers (expanded perlite, lightweight expanded clay aggregate (LECA), and expanded polystyrene (EPS)) to reduce density and improve insulation. Key properties, such as particle-size distribution, printability, mechanical performance, thermal conductivity, and water absorption, were determined. Results indicate that grading strongly affected mixture behavior. Narrow distributions (fly ash, milled 3DCP waste) enhanced extrudability, while broader gradings (glass, rubble, slag) increased water demand and extrusion risks. Despite these differences, all systems remained within the printable window: flow spread decreased with most recycled additions (lowest for brick) and increased with glass. Mechanical responses were composition-dependent. Flexural strength typically decreased. Compressive strength benefited from broader gradings, with replacement levels up to ~6% enhancing strength due to improved packing. Loading anisotropy typical of 3DCP was observed, with perpendicular compressive strength reaching up to 13% higher values than parallel loading. Lightweight fillers significantly reduced thermal conductivity. LECA provided the best compromise between strength and insulation, perlite showed intermediate behavior, and EPS achieved the lowest thermal conductivity but induced significant strength penalties due to weak matrix-EPS interfaces. Water absorption decreased in recycled-aggregate mixes, whereas lightweight systems, particularly with perlite, retained higher uptake. The results demonstrate that non-reactive recycled aggregates and lightweight insulating fillers can be successfully integrated into extrusion-based 3DCP without compromising printability. Full article

Standardized pharmaceutical-grade cultivation of Cannabis sativa L. increasingly relies on soilless systems for precision, reproducibility, and regulatory compliance. This review examines the role of inert and semi-inert growing media in indoor cannabis production, focusing on their physical properties, agronomic performance, and sustainability. A systematic literature search was conducted using databases such as Scopus, Web of Science, and Google Scholar, emphasizing peer-reviewed original research, experimental trials, and relevant review articles. Evaluated substrates include rockwool, coconut coir, peat-based blends, perlite, vermiculite, expanded clay, foamed glass, phenolic foam, and biochar. Findings show that substrate selection strongly affects vegetative growth, rooting, and flower yield, while cannabinoid concentrations remain primarily genotype-driven under stable environmental and nutritional conditions. Substrate-specific traits such as aeration, water-holding capacity, and nutrient buffering significantly influence biomass production and resource-use efficiency. Rockwool remains the industry standard due to its uniformity and compatibility with fertigation systems, but renewable alternatives like coconut coir and biochar are gaining traction. This review underscores the importance of substrate selection in cannabis cultivation and identifies research gaps in genotype-specific responses and the development of sustainable growing media. Full article

As infrastructure construction expands, the massive consumption of traditional concrete materials has led to resource shortages and environmental pollution. Utilizing industrial wastes such as coal gangue and fly ash to produce high-performance concrete is an important pathway toward a greener construction industry. However, concrete incorporating high volumes of fly ash and coal gangue (i.e., high-volume fly-ash coal-gangue self-compacting concrete, CGSC) suffers from low strength and high brittleness due to the inherent deficiencies of its constituents. This study proposes using glass fiber-reinforced polymer (GFRP) tubes for external confinement to improve the axial compressive capacity and deformability of CGSC. A total of 27 concrete cylinders were prepared and tested under axial compression, with real-time acoustic emission (AE) monitoring. The variables examined include the coarse aggregate type (coal-gangue and natural gravel), GFRP tube thickness (5 mm and 8 mm), and fly-ash content (80%, 85%, 90%). The stress–strain response of each specimen and the failure evolution of internal cracks were recorded throughout the loading process. The results show that GFRP tube confinement markedly increases the axial strength and ductility of CGSC. AE features exhibited staged behavior that closely mirrored the stress–strain curves. This correspondence reveals the progression of internal cracks under confinement and indicates that AE is an effective tool for damage monitoring in such composites. The findings provide a new technical approach for the efficient reuse of solid waste in concrete and offer a theoretical and practical basis for applying FRP composite structures in underground support engineering. Full article

High-performance concrete for 3D printing has recently attracted significant attention due to its potential to create structural elements without the need for traditional reinforcement. While various formulations have been proposed by researchers, evaluations are often limited to mechanical performance and printability, while cost and environmental impact are generally overlooked. This study expands the analysis by also considering cost and environmental impact, aiming to identify the optimal mix using a multi-criteria decision-making analysis (MCDMA). In the first phase, several high-strength mortar formulations were developed and assessed based on mechanical strength, printability, environmental impact, and cost. In the second phase, the most promising mix from the initial evaluation was further modified by incorporating different types of fibers, including aramid, carbon, glass, cellulose, and polypropylene. Comprehensive testing—covering mechanical properties and printability—together with cost and a life cycle assessment were conducted to determine the most effective mortar formulations. One of the main findings is that adding 0.05% of 20 mm length cellulose fibers in weight to a mortar containing Cem I 42.5R can increase the compressive strength by more than 9% without affecting the cost or environmental impact, also allowing the obtainment of a mortar apt for 3D printing. This increase in the compression strength is presumably related to a lateral restriction in movements of the mortar, which makes it increase the maximal principal stresses, and thus, its strength. Full article

Laser cladding with ultrafast cooling rates enables effective fabrication of metallic glass matrix composite (MGMC) coatings, significantly enhancing the hardness, corrosion resistance, and mechanical properties of metallic substrates. In this study, a multi-layer Zr₆₅Al_7.5Ni₁₀Cu_17.5 (at. %) MGMC coating was successfully fabricated by laser cladding technology. The effects of the region-dependent microstructural evolution on micro-mechanical properties and corrosion resistance were systematically investigated. The results indicated that the high impurity content of the powder feedstock promoted the crystallization of the coating during laser cladding. Moreover, coarse columnar crystals in the bottom region of the coating nucleated epitaxially at the coating/substrate interface and propagated along the thermal gradient parallel to the building direction, while dendritic crystals dominated the middle region under moderate thermal gradients. In the top region, fine dendritic and equiaxed crystals deposited in the amorphous matrix, due to the lowest thermal gradient and the highest cooling rate. Correspondingly, nanoindentation results revealed that the top region exhibited peak hardness (H), maximum elastic modulus (E), and optimal H/E ratio, exceeding values in both the bottom region and substrate. Simultaneously, the metallic glass matrix composite coating demonstrated significantly better corrosion resistance than the substrate due to its amorphous phase and protective passive film formation. This work advances amorphous solidification theory while expanding applications of metallic glasses in surface engineering. Full article

Drilling fluid losses into formation voids are among the major issues that lead to increases in the costs and nonproductive time of operations. Lost circulation materials have been widely used to stop or mitigate losses. In most cases, the size of the loss zone is not known, making conventional lost circulation materials unsuitable for plugging the loss zone. In this study, novel temperature-sensitive LCM (TS-LCM) particles composed of diglycidyl ether of bisphenol A (DGEBA) and 4,4′-diaminodiphenyl methane were prepared. It is a thermal-response shape-memory polymer. The molecular structure was analyzed by Fourier transform infrared spectroscopy. The glass transition temperature (T_g) was tested by Different scanning calorimetry (DSC). The shape-memory properties were evaluated by a bend-recovery test instrument. The expansion and mechanical properties of particles were investigated under high temperature and high pressure. Fracture sealing testing apparatus was used to evaluate sealing performance. The mechanism of sealing fracture was discussed. Research results indicated that the T_g of the TS-LCM was 70.24 °C. The shape fixation ratio was more than 99% at room temperature, and the shape recovery ratio was 100% above the T_g. The particle was flaky before activation. It expanded to a cube shape, and the thickness increased when activated. The rate of particle size increase for D90 was more than 60% under 120 °C and 20 MPa. The activated TS-LCM particles had high crush strength. The expansion of the TS-LCM particles could self-adaptively bridge and seal the fracture without knowing the width. The addition of TS-LCM particles could seal the tapered slot with entrance widths of 2 mm, 3 mm and 4 mm without changing the lost circulation material formulation. The developed TS-LCM has good compatibility with local saltwater-based drilling fluid. In field tests in the Yan’an area of the Ordos Basin, 15 shale oil horizontal wells were plugged with excellent results. The equivalent circulating density of drilling fluid leakage increased by an average of 0.35 g/cm³, and the success rate of plugging malignant leakage increased from 32% to 82.5%. The drilling cycle was shortened by an average of 14.3%, and the effect of enhancing the pressure-bearing capacity of the well wall was significant. The prepared TS-LCM could cure fluid loss in a fractured formation efficiently. It has good prospects for promotion. Full article

To mitigate the issue of accumulating glass waste, an advanced process has been developed for the production of glass foams via alkaline activation, employing industrial glass cullet as the primary raw material. This method contributes to circular economy strategies by enabling high-value upcycling of secondary raw materials. The aim of the study is to conduct an environmental assessment of this recycling process using the Life Cycle Assessment (LCA). The analysis is performed with SimaPro software, adopting the ReCiPe impact assessment method, which allows for the quantification of 18 impact categories. Four distinct foaming processes were compared to determine the most environmentally preferable option and a sensitivity analysis was conducted to assess how variations in energy sources influence the environmental performance. The findings indicate that the scenario involving hardening at 40 °C for seven days results in the highest environmental burdens. Specifically, in the Human Carcinogenic Toxicity category, the normalized impacts for this process are approximately an order of magnitude greater. Electricity consumption is identified as the primary contributor to the overall impact. The sensitivity analysis underscores that utilizing photovoltaic panels reduces impacts. Future developments will focus on expanding the system boundaries to provide a more comprehensive understanding and supporting informed decision-making. Full article

In recent decades, replacing clinker in cement with mineral additives has become increasingly common, and the range of such additives continues to expand. An example is the growing number of cement types defined in European standards. Some of these standards allow the use of fine recycled concrete waste as an active additive in amounts up to 35%.. Finely ground waste glass, whose quantity steadily increases worldwide, can also be classified as an active additive. Due to its relatively high silica content, finely ground waste glass is a potential supplementary cementitious material. However, the high alkali content in glass limits its use in cementitious products to 5–10% of the binder mass. Considering that silicate binders (water glass) with high alkali activity are also used in construction and influence the hydration process of cement, it can be assumed that waste glass likewise has a significant impact on the properties of cement composites, particularly on hardening parameters and the development of mechanical strength. However, scientific literature lacks data on the synergistic effect of alkaline components of finely ground waste glass and water glass on the cement hydration process, its hardening, and the strength of cement products. Therefore, this study aimed to analyze the mechanism of the influence of a glass-based composite, consisting of waste glass additives and water glass, on the physicochemical and mechanical properties of cement composites. Full article

Cobalt-based bulk metallic glasses (Co-based BMGs) offer a combination of high strength, corrosion resistance, and soft magnetic properties, yet their limited glass-forming ability (GFA) and poor room-temperature ductility restrict broader application. In this study, a microalloying strategy was applied to the Co₆₁Nb₈B₃₁ base composition to develop Co-Nb-B-Si and Co-Fe-Nb-B-Si systems. The effects of Si addition and Fe substitution on GFA, thermal stability, and mechanical properties were systematically investigated. Si doping combined with Co/B ratio tuning broadened the supercooled liquid region and increased the critical glass-forming diameter from 1 mm to 3 mm. Further addition of 5 at.% Fe expanded the supercooled liquid region and enabled the fabrication of a fully amorphous plate with 1 mm thickness. The optimized Co₆₃Nb₈B₂₇Si₂ alloy exhibited a compressive strength of 5.18 GPa and a plastic strain of 3.81%. Fracture surface analysis revealed ductile fracture features in the Si-containing alloy and brittle characteristics in Fe-rich compositions. These results demonstrate that microalloying is effective in optimizing the balance between GFA and mechanical performance of Co-based BMGs, offering guidance for composition and processing design. Full article