Search Results (1,300)

The goal of the present paper is to apply a novel biomimetic design strategy for the analysis, emulation, and technical evaluation of design solutions inspired by the morphogenetic logic of the walnut shell microstructure. The shell consists of specialized cells, called sclereids, which develop protrusions and mechanically interlock with neighboring cells, providing exceptional toughness through increased surface contact. To extract and transfer this biological principle, a generative algorithm was developed using the evolutionary solver Galapagos within the Grasshopper visual programming environment. The algorithm generates protrusions on the interfaces of structural blocks and optimizes their contact surface area while maintaining constant block volume. Additional design constraints, including symmetry and manufacturability considerations, were introduced to improve structural performance and computational efficiency. A series of physical specimens with variations in key geometric parameters, such as protrusion number and height, were fabricated using fused filament fabrication (FFF) with PLA material and evaluated through in-plane and out-of-plane three-point bending tests. The results show that increasing the number of protrusions significantly enhances mechanical performance, while increasing their height improves stiffness and interlocking up to a certain threshold, beyond which structural performance decreases due to stress concentration effects. This behavior can be attributed to improved load transfer and stress distribution across the enlarged interfacial area, as well as progressive mechanical engagement between complementary protrusions. The computational model is in good agreement with the experimental results, confirming the validity of the proposed approach. The study demonstrates that biomimetic optimization of interfacial geometry can enhance the mechanical behavior of interlocking systems and provides a framework for translating biological morphogenetic principles into engineering design applications. Full article

Background: The combination of pharmacological therapy and exercise is frequently recommended for osteoporosis management; however, whether antiresorptive agents may interfere with exercise-induced bone adaptation remains unclear. This study aimed to investigate the independent and combined effects of zoledronate and treadmill exercise on bone microarchitecture and mechanical strength in an ovariectomized rat model. Methods: Twenty-four female Sprague Dawley rats underwent ovariectomy and were assigned to four groups: Control, zoledronate (ZA), treadmill exercise (T), and combined zoledronate and exercise (ZA + T). An additional sham-operated group was included. Zoledronate was administered as a single subcutaneous injection, and a 6-week treadmill exercise routine was implemented. Bone microarchitecture was assessed using micro-computed tomography, and a three-point bending test was employed for evaluation of mechanical properties. Results: The combined ZA + T group demonstrated significant improvements in trabecular bone parameters, including bone volume/tissue volume and trabecular number, compared with the Control group. Mechanical strength parameters, including maximum load and stiffness, were also significantly enhanced in the ZA + T group. Cortical bone parameters exhibited no significant changes. Conclusions: Treadmill exercise did not attenuate the effects of zoledronate, and may offer additive benefits in enhancing trabecular bone microarchitecture and mechanical strength. These findings suggest that exercise therapy can complement bisphosphonate treatment and contribute to optimizing therapeutic strategies for osteoporosis, supporting the potential utility of combined pharmacological and exercise-based interventions for improving bone health. Full article

Barley lodging—specifically stem lodging—occurs when the bending moments from wind and ear weight exceed the culm’s load-bearing capacity. Lodging risk decreases as plant height decreases and culm strength increases. Geometry (stem diameter, culm wall thickness) and material strength determine culm bending strength. By studying changes in stem mechanical properties (at three positions along the culm) in two genotypes (grown in a greenhouse), we found that culm strength (assessed with a three-point bending test) slightly diminished through ripening owing to a decline in both area moment of inertia (i.e., strength due to geometry alone) and apparent material strength, presumably due to turgor loss. When the stem segments collected from fully ripe plants were dried to a moisture content typical of harvest maturity, however, strength rose to a maximum. Thus, minimum stem bending resistance occurs during a window in which plants are fully ripe but have not yet reached harvest-dry moisture content. Hence, in the absence of rain—which would severely reduce the mechanical strength of dry, ripe plants—the physiological risk of stem lodging is highest when the crop is fully ripe but not yet harvest-dry. However, the actual lodging risk increases as harvest approaches, because summer storms are frequent at this time of year and dry straw loses rigidity when wetted. Full article

This study addresses several key limitations identified in previous research on additively manufactured PLA composites. Unlike most earlier studies that focused primarily on the characterization of as-printed materials, the present work systematically investigates both mechanical and surface behavior before, during, and after artificial aging. In addition, six different printing configurations and reinforcement types (PVC and fiberglass mesh) were analyzed under controlled conditions, enabling a more reliable assessment of their combined influence on composite performance. Printed specimens were artificially aged for 45 and 90 days. The aging protocol combined cyclic changes in moisture, temperature, UV, and IR agents, trying to mimic real exploitation conditions as realistically as possible. The chemical and surface changes during aging were tracked using FTIR spectroscopy, colorimetry, contact angle, and surface free energy measurements. Mechanical performance at 0, 45, and 90 days was evaluated through tensile, three-point bending, and Charpy impact tests, as well as full-scale cantilever loading tests of real printed drone arms. Results show that artificial aging causes measurable chemical and surface modifications, as indicated by changes in the FTIR degradation index and surface wettability. However, these changes do not result in severe mechanical degradation within the investigated aging period. Reinforcement in the form of incorporated PVC and fiberglass mesh significantly affected failure behavior. Specimens printed with higher infill density and thicker infill lines generally exhibit improved mechanical properties. Specimens stiffness and impact resistance were also altered. Results demonstrate that reinforced PLA structures are suitable for lightweight drone applications. Full article

In this study, commercial Ospray-2507 super-duplex stainless steel powder was investigated for the first time as a potential metal support material for solid oxide cells. Initially, metal supports were fabricated and processed in air using various sintering profiles, followed by comprehensive mechanical, structural and electrochemical characterization. The optimal sintering condition was identified as 900 °C for 5 h. Subsequently, sintering under a H₂ atmosphere was explored, and its effects on the microstructural and functional properties of the metal supports were systematically to assessed to evaluate the influence of the sintering atmosphere on material performance. Although X-ray diffraction patterns showed no phase changes between the two sintering atmospheres, notable improvements were observed in mechanical, electrochemical, and microstructural properties under H₂ sintering. XPS spectra reveal that both air- and hydrogen-treated surfaces remain rich in chromium (Cr) and Manganese (Mn), which together dominate the surface and consequently attenuate the signal from the underlying iron. The thickness of the Cr- and Mn-based oxide layer decreases when sintering MS in H₂ atmosphere. Specifically, mechanical strength, as measured by three-point bending tests, increased by a factor of 12.5, and hardness rose from 500.3 to 523.5 HV. Furthermore, electrical conductivity also improved significantly, exhibiting an approximately 2.3–2.4 fold increase under H₂-sintered conditions. Full article

This study investigates the shear behavior of glass fiber-reinforced polymer (GFRP)-reinforced concrete (RC) beams to address challenges associated with their low elastic modulus, absence of yielding, and reduced stirrup efficiency in bending regions. GFRP bars are increasingly adopted as an alternative to steel due to their superior corrosion resistance, durability, and cost-effectiveness. This study focuses on the effects of stirrup type, stirrup spacing, and shear span-to-effective depth ratio on the structural performance of GFRP RC beams. Twelve full-scale beams were tested under four-point bending, incorporating three GFRP shear reinforcement configurations: fabricated closed stirrups, integrated straight bar systems, and discrete vertical bars. Experimental observations were analyzed in terms of failure modes, load-carrying capacity, energy absorption, and deformation characteristics. Results indicate that fabricated F-type stirrups provide the highest shear performance, though their effectiveness is limited by premature rupture at bending points. Site-integrated S- and T-type configurations offer practical alternatives, maintaining structural integrity while mitigating bend-related stress concentrations, but with slightly lower energy absorption and load capacity. Increasing stirrup spacing significantly reduces shear resistance and shifts failure from flexural to shear-dominated modes. Comparisons with widely used design codes and analytical models show that CSA S806-12 provisions offer the most reliable predictions, while other guidelines tend to over- or underestimate shear capacity depending on configuration and a/d ratio. The study highlights the importance of optimizing stirrup type and spacing to enhance the shear performance of GFRP RC beams. Findings provide valuable insights for improving current design methodologies, offering guidance for engineers seeking durable, corrosion-resistant alternatives to steel reinforcement in aggressive environments. This research demonstrates that innovative site-integrated stirrup configurations can bridge practical fabrication constraints without compromising overall shear performance, promoting more efficient and resilient GFRP RC structures. Full article

Objective: To determine the most suitable core build-up materials based on their mechanical and physical properties, different resin based materials were evaluated for flexural strength (FS), flexural modulus (E), modulus of resilience (R), water sorption (WS), and solubility (SO). Materials and Methods: Three dual-cure resins (CosmeCore DC Automix, CCC; Clearfil DC Core Plus, CCP; MultiCore Flow, CMC) and two bulk fill composites (Filtek One Bulk Fill Restorative, BFO; Filtek Bulk Fill Flowable, BFF) were tested, with Filtek Supreme Ultra (FSU) as the control. All tests followed ISO 4049. Beam specimens (25 × 2 × 2 mm, n = 12) were used to determine FS and E after 24 h storage in 37 °C deionized water, using a three-point bending test. Disc specimens (15 × 1 mm, n = 5) were used for WS and SO by measuring mass changes before and after water storage. Data were analysed using one way ANOVA and Tukey post hoc tests (p < 0.05). Results: CCC exhibited the highest FS and lowest WS. BFF showed the lowest E, while BFO exhibited the highest R. FSU demonstrated the lowest FS and R, along with the highest WS. No significant differences in SO were observed among groups. Conclusions: The evaluated materials showed considerable variation in mechanical and physical properties. CCC and BFO demonstrated the most favourable performance, suggesting they are the most suitable candidates for core build up procedures among the materials tested. Full article

Rock fracture behavior is strongly influenced by grain size and boundary effects, which complicate the determination of fracture parameters and the interpretation of size-dependent failure. This study investigates the fracture behavior of sandstone and diorite within the framework of the boundary effect model (BEM) using three-point bending tests, acoustic emission (AE), and digital image correlation (DIC). By varying the prefabricated crack length, different values of the structural geometric parameters a_e were obtained, and the fracture toughness K_IC and tensile strength f_t were identified by regression analysis. The results show that K_IC = 0.6841 MPa·m^0.5 and f_t = 4.5625 MPa for sandstone, whereas K_IC = 2.7233 MPa·m^0.5 and f_t = 21.8218 MPa for diorite. Increasing the prefabricated crack length reduces the peak load and prolongs the pre-peak damage evolution stage. Diorite, with a larger average grain size, exhibits higher AE energy release, a higher proportion of high-energy AE events, and a larger fracture process zone (FPZ) than sandstone. Moreover, the AE energy distribution along the crack propagation direction shows a distinct “three-stage” characteristic, consistent with the non-uniform distribution of local fracture energy g_f predicted by boundary effect theory. The results indicate that BEM can reasonably characterize the fracture behavior of rocks with different grain sizes, and the identified material parameters can be used to construct a BEM-based structural failure curve for estimating nominal failure stress over a wider range of structural geometric parameters. Full article

The upscaling of turbines in the offshore wind industry has been unprecedented, as compared to 5–6 MW rated turbines 10 years ago. A typical 20–26 MW rated turbine in modern commercial applications (MingYang MySE 18.X-20 MW installed in 2025 and 26 MW prototype by Dongfang Electric tested in 2025) has been demonstrated. This scaling has been made possible by increasing rotor diameters (>250 m) and hub heights (>150–180 m) to achieve capacity factors of up to 55–65%, annual energy generation of more than 80 GWh/turbine, and significant decreases in levelised cost of energy (LCOE) to current values of up to 63–65 USD 2023/MWh globally averaged in 2023 (with minor variability in 2024 due to market changes and new regional areas). The paper analyses turbine upscaling over three levels of hierarchy, including turbine scale—rated capacity and physical aspect, project scale—multi-gigawatts of farms, and market scale—the global pipeline > 1500 GW level, and combines techno-economic evaluation, structural evaluation of loads, and infrastructure needs assessment. The upscaling has the advantage of reducing the number of turbines dramatically (e.g., 500 to 67 turbines in a 1 GW farm, as turbine size is increased to 15 MW) and balancing-of-plant (BoP) CAPEX (turbine-to-turbine foundations and cables) by some 20 to 30 percent per unit of capacity, and serial production learning rates of between 15 and 18% per doubling of capacity. But the problems that come with the increase in ultra-large designs are nonlinear increments in mass and load (i.e., blade-root and tower-bending moments), logistical constraints (blades > 120 m, nacelle up to 800–1000 tonnes demanding special vessels and ports), supply-chain issues (rare-earth materials, vessel shortages increase day rates by 30–50%), and technology limitations (aeroelastic compounded by numerical differences between reference 5 MW, 10 MW, and 15 MW models), it becomes evident that there is a significant increase in deflections of the tower and blades and platform surge/pitch responses with continued increases in power levels, but without a correspondingly mature infrastructure. The regional differences (mature ports of Europe vs. U.S. Jones Act restrictions vs. scale-up of vessels/manufacturing in China) lead to the necessity of optimisation depending on the context. The analysis concludes that, to the extent of mature markets with adapted logistics, continuous upscaling is an effective business strategy and can result in 5 to 12 percent further reductions in LCOE, but beyond that point, gains become marginal or even negative, as risks and costs increase. The competitiveness of the future depends on multi-scale/multi-market-based approaches—modular-based families of turbines, programmatic standardisation, vibration control innovations, and industry coordination towards supply-chain alignment and standards. Its major strength is that it transcends mere size–cost relationships and shows how nonlinear structural processes, aero-hydro-servo-elastic interactions, and bottlenecks in logistical systems are becoming more determinant of the efficiency of ultra-large turbines. The study demonstrates that upscaling turbines has LCOE benefits through the support of associated improvements in installation facility, supply-chain preparedness, and structural vibration control potential, based on the comparisons of quantitative loads, techno-economic scaling trends, and regional market differentiation. Full article

With Aligned Formable Fibre Technology (AFFT^™), fibers are reformatted into highly oriented epoxy prepreg tapes, enabling the structural reuse of recycled composite waste. The present study investigates whether discontinuous fiber laminates produced with AFFT^™ can be characterized and optimized with the same finite-element workflows long established for continuous fiber composites and whether the resulting structures meet demanding stiffness targets. Initially, various manufacturing methods were adopted, including vacuum bagging, compression molding at 7 bar to simulate autoclave conditions, and compression molding at 90 bar, comprising the three most reasonable manufacturing processes for AFFT^™ laminates. Experimentally measured orthotropic properties were introduced into a finite-element model representing an idealized bicycle top tube, which was chosen as a case study. A genetic algorithm screened candidate stacking sequences, minimizing the combined bending-and-torsion deflection. The best lay-ups reduced deformation by more than 30% compared to a quasi-isotropic baseline, showing that well-oriented short fibers can significantly contribute to the stiffness of composites. Tubes produced with the optimized lay-up were tested in three-point bending tests, and the measured stiffness matched simulations within 5%. These results confirm a key point for sustainable engineering: despite the absence of continuous fibers, conventional simulation strategies accurately predict the performance of AFFT^™ laminates and can be used as the basis for effective genetic optimization. This validation is significant: it enables the design of stiff, high-performance structures from recycled materials using established, cost-effective methods. By proving that optimization strategies developed for traditional continuous fiber composites apply to AFFT^™, this study offers a trusted and accessible pathway to scale circular economy solutions in next-generation composite products. Full article

Ultra-high-performance concrete (UHPC) has been widely investigated for its superior strength and durability; however, despite extensive research on fibre reinforcement, limited attention has been given to validating fibre surface modification strategies at the structural scale. Improvements in fibre–matrix bonding are commonly demonstrated through single-fibre tests, with limited evidence of their translation into the mechanical performance of UHPC elements. This study investigates the influence of bioinspired surface-modified steel fibres on the mechanical behaviour of UHPC, focusing on whether interfacial enhancements lead to measurable structural-scale performance gains. Steel fibres were coated under mild aqueous conditions and incorporated into UHPC at a volume fraction of 1%. Compressive strength was evaluated at 7, 14, 28, 56, and 90 days, while flexural behaviour was assessed at 7 and 28 days using three-point bending tests on notched beams and four-point bending tests on prisms. The incorporation of surface-modified fibres resulted in consistent strength enhancement at all curing ages. Compared with mixes containing uncoated fibres, compressive strength increased by approximately 15% at 7 days and remained 5–7% higher at later ages up to 90 days. More pronounced improvements were observed in flexural performance, with coated specimens exhibiting up to 51% higher peak load at 7 days and 29–32% higher peak load at 28 days in both bending configurations. These results demonstrate that fibre surface modification effectively enhances both early-age and long-term mechanical performance of UHPC, confirming that interfacial bond improvements are directly translated into structural-scale response. The findings highlight fibre surface engineering as a practical approach for improving the mechanical efficiency of UHPC without altering mix composition or fibre dosage. Full article

Wood is a versatile material; however, it is susceptible to changes when exposed to extreme temperatures. This study investigated the physical, chemical, and mechanical properties of raulí (Nothofagus alpina) under different thermal stress conditions. The results showed that the moisture content at temperatures below 5 °C exhibited a significant reduction from 9.7% to 7.5% within the first 20 days. Conversely, under extreme cold (−20 °C), significant changes only occurred after 60 days, with an increase from 9.7% to 11%. At higher temperatures (50 °C, 95 °C, and 120 °C), moisture content dropped sharply after 40 days, nearing 0%. Additionally, analysis showed minor color changes in samples at low temperatures: RW2 (20 d; 5 °C, ΔE* = 3.46) and RW7 (40 d; 5 °C, ΔE* = 0.61); however, color changes were observed at higher temperatures (95–120 °C). RW15 (60 d; 120 °C, ΔE* = 37.16), indicating the degradation of cell wall polymers. Mechanical testing using three-point bending demonstrated that controlled heat treatments can improve the modulus of elasticity (MOE), modulus of rupture (MOR), and fracture energy. The most significant improvements were obtained at 120 °C for 60 days, with increases in MOE, MOR, and fracture energy of 22%, 60%, and 118%, respectively, compared to untreated wood. Full article

This study develops a multi-scale fiber-reinforced cementitious composite (MFRC) by hybridizing calcium carbonate whisker (CW), polyvinyl alcohol (PVA) fiber, and steel fiber. The interfacial micromechanical properties between steel fiber/matrix and PVA fiber/matrix under the influence of CW were systematically examined through single-fiber pull-out tests. The two-dimensional and three-dimensional distribution characteristics of fibers in the MFRC were analyzed using backscattered electron imaging (BSE) and X-ray computed tomography (X-CT), respectively. Based on the fiber distribution characteristics, flexural strength prediction models were developed with R² values of 0.79 (2D) and 0.82 (3D). Experimental validation via splitting tensile tests and three-point bending tests confirmed the model’s effectiveness in simultaneously predicting splitting tensile strength (R² = 0.89) and flexural strength (R² = 0.93). These findings demonstrate the reliability and universality of the proposed model for predicting flexural–tensile strength in an MFRC. Full article

Bending-dominated lattice structures offer superior stability but suffer from low stiffness and natural frequencies, posing resonance risks in aerospace applications. To address this, a novel Membrane-Wrapped Lattice (MWL) encapsulated by a micrometer-scale metallic film is proposed. A theoretical framework based on the tension-compression asymmetry of the membrane is established to analyze the influence of membrane thickness on the neutral axis shift, ultimately deriving analytical formulations for flexural stiffness and natural frequencies. MWL specimens with varying membrane thicknesses (0–50 μm) were fabricated via selective laser melting and adhesive bonding, then subjected to three-point bending and vibration tests. Results demonstrate that wrapping with a 50 μm 316 L stainless steel membrane increases the flexural stiffness by 128% and the fundamental natural frequency by 85%. The experimental measurements align well with theoretical and numerical predictions, validating this lightweight, high-stiffness design strategy. Full article

This paper presents an experimental and numerical study on the effect of steel fiber distribution on the flexural behavior of self-compacting mortars (FRSCMs). Six FRSCM mixtures were modeled in ABAQUS as prismatic specimens (40 × 40 × 160 mm³) subjected to static three-point bending. The methodology involved two steps: (i) preparation of six mortar variants composed of three layers with different hooked steel fiber dosages (20, 30, and 40 kg/m³ for M20, M30, and M40) assembled in various configurations to study fiber distribution effects; (ii) numerical modeling of prismatic specimens in ABAQUS, using structured meshing with C3D8R hexahedral elements. Each layer was meshed separately with aligned nodes to ensure proper assembly. Our results highlight the strong influence of fiber distribution: despite identical fiber content (90 kg/m³ of hooked steel fibers), flexural strength varied across beam configurations. Layered casting led to an increase in flexural strength of up to 71.83% compared to the reference. The numerical predictions closely matched the experimental results, with relative errors ranging from 1% to 8.13% for most variants, demonstrating the reliability of the model. The larger discrepancies observed for specimens M324 and M342 are attributed to the limitation of the study to the elastic domain, as damage and plasticity effects were not included in the simulations. The distribution and orientation of fibers (particularly steel fibers) in a cementitious matrix, namely concrete or cement mortar, has been the subject of several studies aimed at determining the best mechanical performance of fiber-reinforced concrete. The proposed modeling approach of bending mechanical behavior allows us to predict the effects of fiber distribution in fluid mortars and reinforced self-compacting mortars, thereby reducing the need for extensive experimental testing. It also represents a significant improvement over existing approaches reported in the literature. Full article