Search Results (906)

The advancement of polymeric materials for orthopedic applications has enabled the development of lightweight, adaptable structures that support patient-specific solutions. This study focuses on the design, fabrication, and mechanical characterization of additively manufactured (AM) polymeric polylactic acid (PLA) components produced via Material Extrusion (MEX), commonly known as Fused Filament Fabrication (FFF). By optimizing geometric configurations and process parameters, these structures demonstrate enhanced flexibility, energy absorption, and load distribution, making them well-suited for orthopedic products and assistive devices. A comprehensive mechanical testing campaign was conducted to evaluate the elasticity, ductility, and strength of FFF-fabricated samples under tensile and three-point bending loads. Key process parameters, including nozzle diameter, layer thickness, and printing orientation, were systematically varied, and their influence on mechanical performance was recorded. The results reveal that these parameters affect mechanical properties in a complex, interdependent manner. To better understand these relationships, an automated routine was developed to calculate the experimental mechanical response, specifically, stiffness and strength. This methodology enables an automated evaluation of the output, considering parameter ranges for future applications. The outcome of the analysis of variance (ANOVA) of the experimental investigation reveals that the printing orientation has a strong impact on the mechanical anisotropy in FFF, while layer thickness and nozzle diameter demonstrate moderate-to-weak importance. Thereafter, the experimental findings were applied on an innovative orthopedic wrist splint design to be fabricated by means of FFF. The most suitable mechanical properties were selected to test the mechanical response of the designed components under operational bending loading by means of linear elastic finite element (FE) analysis. The computational results indicated the importance of employing the actual mechanical properties derived from the applied printing process parameters compared to data sheet values. Hereby, an additional parameter to adjust the mechanical response is the product’s design topology. Finally, this framework lays the foundation for future training of neural networks to optimize specific mechanical responses, reducing reliance on conventional trial-and-error processes and improving the balance between orthopedic product quality and manufacturing efficiency. Full article

Additive manufacturing is a suitable method for multi-material production, as it offers flexibility in structural design and enables layer-by-layer fabrication of materials. However, the different chemical structures and formulations of the materials used may affect the mechanical integrity of the part. In nature, there are many patterned structures that inspire the design of multi-material additive manufacturing components. Integrating the harmony and advantages of these natural structures into the manufacturing process will significantly contribute to human development. This study presents a novel manufacturing approach for using existing natural or artificially produced pattern forms in the development of composite materials. In this aim, patterned parts composed of multiple materials were produced using a 3D printer with combinations of PLA Plus, PLA CF, and PLA GF. Mechanical tests were conducted on the produced parts, and their fracture surfaces were examined. In patterned specimens, tensile strength decreased compared to reference (non-patterned) specimens. In the PLA Plus–PLA Plus and PLA Plus–PLA CF combinations, tensile strength generally decreased in samples with three patterns, while the greatest reduction in tensile strength occurred in the PLA Plus–PLA GF patterned specimens. The highest bending forces were obtained in single- and five-pattern samples with PLA Plus–PLA Plus and PLA Plus–PLA CF combinations, as well as in five-pattern samples with the PLA Plus–PLA GF combination. The results indicate that the presence and number of patterns are important factors influencing the mechanical properties of the specimens. Full article

In the treatment of soda-residue-stabilized soil with high water content using drainage boards with vacuum preloading, the boards often prone to clogging and bending under lateral pressure, reducing their hydraulic conductivity and affecting the soil reinforcement. In this study, the structure of the standard plastic drainage board (filter membrane + filter core) was improved, and three types of new anti-clogging plastic drainage boards with different structures were developed (Type X: geotextile + filter core, Type Y: geotextile + wire mesh + filter core, Type Z: geotextile + filter membrane + filter core). Permeability tests were subsequently used to determine the optimal structure. In-lab vertical draining tests with vacuum preloading were carried out on the selected model to study the change in water content, vacuum pressure, surface settlement, vane shear strength, and pore water pressure of soil with drainage board insertion depth, providing a reference for the application of new anti-clogging drainage boards in engineering. The results showed that: (1) the type Y anti-clogging plastic drainage board (geotextile + wire mesh + filter core) exhibits the most balanced performance in terms of permeability, anti-clogging ability, tensile strength and bending strength and is suitable for vacuum preloading of soda residue with high water content; (2) the mechanical properties and anti-clogging performance of drainage boards are highly dependent on their structural configuration. Introducing a wire mesh between the filter core and the geotextile significantly enhances the tensile and bending strength of the drainage board without noticeably compromising its drainage performance; (3) the insertion depth of the drainage board significantly affects drainage efficiency, vacuum transmission rate, and strength development of the soda residue. The effective reinforcement range of the drainage board is not limited to the insertion depth but also extends below the bottom of the drainage board. Full article

In this work, a flexible, stretchable, tough, highly ionic conductive, and anti-freezing hydrogel based on acrylamide/two-dimensional transition metal carbide (MXene)/montmorillonite (MMT) was precisely designed. In the hydrogel, MXene and MMT acted as both cross-linking agents and conductive fillers, delivering high stretchability (1037%) with a strength of up to approximately 67 kPa and high conductivity. As a result, the usual trade-off between conductivity and mechanical properties of hydrogels could be alleviated to some extent. Therefore, the hydrogel could be used as an electrolyte for supercapacitors (SCs) and strain sensors to monitor physical signals. The hydrogel-based SC exhibited outstanding electrochemical performance over a wide temperature range. Moreover, it could easily withstand various deformations, such as bending, twisting, and compression. The hydrogel also exhibited excellent sensing properties, with a short tensile response time and a high-sensitivity factor (GF = 14.8) in the 0–400% range (0 denotes the original state, where both the strain and stretch are zero as there is no deformation at this point). Due to its high conductivity, the prepared hydrogel could be used as a flexible electrode to replace commercial electrodes and record electromyographic (EMG) signals. This work proposes a novel approach for balancing the conductivity and mechanical strength of hydrogels. Full article

Currently, unreinforced steel fiber-reinforced concrete (USFRC) has not been widely adopted in underground engineering within China. However, extensive research has demonstrated that incorporating steel fibers can effectively enhance the mechanical properties of concrete, such as tensile strength, shear strength, residual flexural tensile strength, and also improve its durability. This study, based on the Qiandong experimental section of Dalian Metro Line 4, aims to investigate the failure modes, bearing capacity, and calculation methods for reinforced concrete (RC) and USFRC lining segment joints under compression-bending loading. The objective is to provide a reference for the application of USFRC lining segments in domestic underground engineering. The main conclusions are as follows: (1) The primary failure mode of RC segment joints is large-area crushing of concrete on the outer curved surface, with tensile crack widths on the inner curved surface less than 0.20 mm. The failure mode of USFRC segment joints is characterized by a 2.50 mm wide tensile crack below the loading point. (2) The bolt strain at failure for RC segment joints is approximately twice that of USFRC joints, with both reaching the yield strength and entering the plastic deformation stage. The bolt stress versus bending moment curve exhibits two distinct growth stages. USFRC can effectively control bolt deformation and stress, thereby enhancing bearing capacity. (3) The joint rotation angle versus bending moment curve follows a bilinear model. Under identical bending moments, the rotation angle of RC segment joints is significantly larger than that of USFRC joints. In the two stages, the rotational stiffness of USFRC joints is 367.13% and 763.82% of that of RC joints, respectively. (4) Bolts do not influence the bearing capacity of the segment joints. Existing calculation models in current design codes can accurately predict the ultimate bearing capacity of both RC and USFRC segment joints, demonstrating high prediction accuracy. Full article

Additive Manufacturing (AM) using Fused Layer Modelling (FLM) often results in polymer components with limited and highly anisotropic mechanical properties, exhibiting structural weaknesses in the layer direction (Z-direction) due to low interlaminar adhesion. The main objective of this work was to investigate and quantify these mechanical limitations and to develop strategies for their mitigation. Specifically, this study aimed to (1) characterize the anisotropic behavior of unreinforced Polycarbonate (PC) components, (2) evaluate the effect of continuous, unidirectional (UD) carbon fiber tape reinforcement on mechanical performance, and (3) validate experimental findings through Finite Element Method (FEM) simulations to support predictive modeling of reinforced FLM structures. Methods involved experimental tensile and 3-point bending tests on specimens printed in all three spatial directions (X, Y, Z), validated against FEM simulations in ANSYS Composite PrepPost (ACP) using an orthotropic material model and the Hashin failure criterion. Results showed unreinforced samples had a pronounced anisotropy, with tensile strength reduced by over 70% in the Z direction. UD tape integration nearly eliminated this orthotropic behavior and led to strength gains of over 400% in tensile and flexural strength in the Z-direction. The FEM simulations showed very good agreement regarding initial stiffness and failure load. Targeted UD tape reinforcement effectively compensates for the weaknesses of FLM structures, although the quality of the tape–matrix bond and process reproducibility remain decisive factors for the reliability of the composite system, underscoring the necessity for targeted process optimization. Full article

This study investigated the preparation of bacterial nanocellulose yarn, a high-strength and high-modulus cellulose-based textile material. Compared with the previously used wet spinning and electrospinning methods, the film-cutting, drawing and twisting treatment method in this paper retains the natural structure of BNC. This can greatly transfer the high performance of BNC nanofibers to BNC yarns, making the mechanical properties of the prepared yarn much higher than those of the BNC yarns prepared by the above two methods. It was produced through a film-cutting and twisting process utilizing bacterial nanocellulose as the primary component. The effects of drafting and twisting on the characteristics and properties of the yarn were systematically examined. Comparative analyses were conducted between the bacterial nanocellulose yarn and conventional cotton yarn of equivalent fineness and twist in terms of appearance, tensile properties, frictional behavior, and bending resistance. Optimal tensile mechanical properties of the bacterial nanocellulose yarn were achieved at 1% elongation and a twist number of 160 r/20 cm, resulting in a breaking strength of 751.56 MPa and an elongation at break of 11.56%, surpassing those of cotton yarn of similar specifications. The spinnability assessment revealed a smooth surface for the bacterial nanocellulose yarn, characterized by low friction coefficient, robust bending resistance with a bending modulus of 718.76 GPa. These findings offer valuable empirical data and theoretical insights to guide the subsequent textile processing and utilization of bacterial nanocellulose yarn. Full article

Paper plays an important role in the packaging industry due to its low cost, light weight, recyclability and biodegradability. However, the use of paper as a packaging material is severely limited due to its hydrophilicity caused by the hydroxyl groups of cellulose. This study reports a simple preparation of highly hydrophobic kraft paper by a one-step dip coating method using [3-(2,2,3,3-tetrafluoropropoxy)propyl]silsesquioxane, {3-[(2,2,3,3,4,4,5,5-octafluoropentyl)oxy]propyl}silsesquioxane or {3-[(2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoroheptyl)oxy]propyl}silsesquioxane as hydrophobic agents. As a result of modification of kraft paper, a stable covalently bonded coating is formed on its surface. The coated kraft paper has demonstrated (1) high water resistance (the water contact angle (WCA) values were 124–141°, and the water absorption and the water vapor permeability (WVP) rates were significantly decreased), (2) excellent resistance to aggressive environments and temperature, (3) enhanced mechanical properties (tensile strength increased from 46.8 to 70.8 MPa), and (4) high wear resistance, as confirmed by sandpaper abrasion, bending, and finger-wipe tests. It was shown that the maximum contact angle values were achieved for kraft paper modified with a 5% polymer solution. The results of this study have great potential, given the simplicity of the modification method, for use in the production of paper-based packaging materials with water-repellent, enhanced mechanical and moisture-protective properties. Full article

In this paper, the effects of 3D printing parameters on the metallurgical and mechanical properties of 3D-printed 25CrMo4 steel are presented. Using laser-based powder bed fusion of metals (PBF-LB/M), samples were fabricated under varying conditions of laser power, scan speed, and layer thickness. The study examined how variations in volumetric energy density (VED) and linear energy density (LED) influence the material’s performance. The results show a strong correlation between the printing parameters and key properties such as hardness, porosity, bending strength, compressive strength, and tensile strength. Appropriate VED and LED improved density, reduced defects, and enhanced mechanical performance, whereas excessive energy inputs introduced brittleness. These findings support the advancement of additive manufacturing technologies for high-strength steels and broaden their potential applications in the aerospace, automotive, and construction sectors. Full article

Injection molding is a high-volume manufacturing process widely used for producing polymer components; however, its process parameters strongly influence residual stress, warpage, and the resulting mechanical performance. This work presents a comprehensive factorial design and ANOVA to evaluate the simultaneous effects of the injection temperature, packing pressure, packing time, and specimen orientation on the warpage, hardness, tensile, and flexural properties of polypropylene plates. The results demonstrate that the injection temperature and packing pressure are the dominant factors affecting the hardness and ultimate tensile strength, whereas warpage is mainly governed by the injection temperature and orientation. Under the tested conditions, certain combinations of injection temperature and packing pressure led to an improved mechanical performance; however, these adjustments also produced reductions in other properties, indicating that the balance among parameters depends on the targeted application rather than a single optimal set. Conversely, the parameter combination that produced the lowest warpage still yielded a significant increase in $E_{sec}$, indicating that reducing the warpage does not necessarily compromise the tensile stiffness. Interestingly, variations in the stress distribution between the tensile and bending tests suggest that the solidification-induced structure of the material influences its mechanical response, with specimens that showed a lower tensile strength exhibiting a comparatively higher resistance under bending. These findings provide new insights into the trade-offs between dimensional accuracy and mechanical performance and offer practical guidelines for optimizing polypropylene injection molding processes. Full article

The stress–strain–strength behavior of hydraulic asphalt concrete is critical to the safety of the high asphalt concrete core. To study the effect of bitumen grade on the stress–strain–strength behavior of hydraulic asphalt concrete, uniaxial compression tests, direct tension tests, bending tests, and triaxial compression tests were conducted. The variation patterns of mechanical performance indicators and stress–strain curves of hydraulic asphalt concrete with bitumen grades A70, A90, and A110 were analyzed. The elastic modulus expression of asphalt concrete based on nonlinear failure criteria were proposed. Considering potential issues associated with asphalt concrete core, the selection of bitumen grades was discussed. The results indicate that increasing the bitumen grade enhances the tensile, compressive, bending, and shear deformation properties of hydraulic asphalt concrete, and makes it exhibit more pronounced ductile behavior. However, the strength and modulus decrease. The use of higher-grade bitumen reduces the dilatancy of hydraulic asphalt concrete. As the bitumen grade increases, the nonlinear property of the shear strength of hydraulic asphalt concrete becomes more significant. An elastic modulus expression based on nonlinear failure criterion accurately describes the deviatoric stress–axial strain relationship for hydraulic asphalt concrete of different bitumen grades. When the strength of hydraulic asphalt concrete meets these requirements, it is advisable to select higher-grade bitumen to enhance the safety of the core. Full article

The future of reinforcing steel bars (rebar) is being shaped by technological advancements, sustainability initiatives, and evolving construction practices. Welding of rebar has a significant and evolving influence on construction practices, particularly with trends emphasizing speed, precision, and prefabrication. On the other hand, the variability in mechanical response depends not only on the chemical composition but also on the manufacturing and welding process. This study analyzed five commercial brands of ASTM A706 reinforcing steel rods available in the Ecuadorian market with different diameters (12, 14, 16, and 18 mm) subjected to tensile and bending tests. A total of 228 specimens were analyzed, and 114 samples were welded by shielded metal arc welding process using an E8018-C3 electrode, preparing the joint with a simple V-bevel at 45°. The tensile tests results allow for a comparison between the welded and unwelded steel bars, where it is identified that the welding process generates a slight decrease in the mechanical properties and increases the variability in the results, although it is emphasized that these variations do not affect compliance with the standards, since all the samples meet the mechanical strength requirements by being within the limits established by the ASTM A706/A706M standard. Full article

This study quantifies the mechanical behavior of 10–15 mm thick WPC boards compression-molded from post-consumer bottle-cap polyolefins (PP/HDPE, 70/30 wt%) and pine sawdust (0, 10, 20 wt%). Flexural and tensile strength/modulus are determined and application-oriented acceptability assessed for non-structural temporary concrete formwork under ASTM bending and tension protocols. Mechanical performance was evaluated using three-point and four-point bending tests, as well as axial tension. Flexural strengths averaged 17.31, 16.38, and 8.71 MPa for 0, 10, and 20 wt% sawdust (three-points), and 15.23, 13.18, and 9.20 MPa (four-points), with flexural moduli as high as 1.60 GPa (four-points). Tensile strengths averaged 3.60, 3.79, and 3.44 MPa, with tensile elastic moduli of 0.10, 0.33, and 0.36 GPa, respectively. Stress–strain curves showed a nonlinear elastic-brittle response without a defined yield point, followed by fracture, consistent with porous, non-compatibilized WPCs. Variability increased with the sawdust content, reflecting the distribution of filler and matrix-fiber adhesion. Although the properties are inferior to those of conventional building materials, the results are within the application-oriented ranges for non-structural temporary formwork (as established by the reported ASTM tests). UV durability associated with carbon black-pigmented caps is presented as a literature-supported hypothesis for future accelerated aging, rather than as a measured outcome. Overall, the findings demonstrate a circular-economy pathway that converts post-consumer plastics and sawmill waste into WPC panels for sustainable construction. Full article

This research addresses the inherent limitations of low mechanical strength in FDM-printed materials by studying Carbon Fibre-reinforced Polylactic Acid (PLA-CF) composites. The low strength limitation of PLA-CF in FDM requires identifying the most suitable print angle and layer height parameters. This study maximises its structural robustness, filling a knowledge gap regarding its combined effect on tensile and flexural strength. The main objective was to find the best printing angle and layer height to improve mechanical performance, an important requirement for advancing additive manufacturing applications. A total of 210 FDM-printed specimens of the PLA-CF material were subjected to uniaxial tensile (ASTM D3039) and three-point bending (ASTM D790) tests, systematically varying the printing angles (0–90°) and layer heights of 0.1, 0.2, and 0.3 mm, following a full experimental design matrix. The ANOVA method has been used to determine the significant effect of factors on the established parameters. The findings indicated that both factors had a pronounced effect on the mechanical strength. Printing at lower angles (0° and 15°) provided, on average, greater resistance under tension (up to ~3920 N for a layer height of 0.1 mm), as well as under bending (up to 88.54 N for the same layer height), attributed to favourable fibre alignment and better load distribution. Conversely, higher angles (60° to 90°) drastically reduced strength (tensile failures due to delamination; bending forces as low as 30.02 N for a layer height of 0.3 mm, highlighting the weakness of perpendicular layer interfaces. Furthermore, lower layer height could result in better overall mechanical properties. In conclusion, FDM parameters with low print angles and reduced layer heights are essential for maximising the mechanical robustness and structural integrity of PLA-CF parts, enabling the identification of improved production processes for industrial applications and educational prototypes, among others. Full article

To achieve lightweight objectives in the aerospace sector, this paper systematically investigates the influence of unit cell topology on the quasi-static mechanical properties of Al-Mg-Sc-Zr alloy lattice structures fabricated by Selective Laser Melting (SLM). A comparative analysis of the mechanical response and failure mechanisms of eight distinct unit cell topologies was conducted through a combination of quasi-static compression and tensile experiments, finite element (FE) simulation, and fractography via Scanning Electron Microscopy (SEM). The results demonstrate that the mechanical performance is highly dependent on the unit cell topology. Under compression, the structures exhibited a layer-by-layer collapse, whereas under tension, they failed through sequential fracture of multiple struts initiated by stress concentration. Finite element simulations effectively predicted the general trends of the mechanical behavior; however, the actual strength and ductility of the SLM-fabricated specimens were lower than the simulated values due to intrinsic process-induced defects such as pores and lack of fusion. Analysis using the Maxwell index revealed that stretching-dominated structures possess superior specific modulus and specific strength compared to bending-dominated ones. Furthermore, among structures with similar Maxwell indices, those incorporating vertical struts demonstrated higher load-bearing efficiency. This study provides significant experimental and theoretical foundations for the design and application of high-performance lattice materials in lightweight structures. Full article