Tensile Bending Research Articles

Optimization of alkali modified breadfruit peel flour-LDPE composite for car mirror casings

Abstract The research was carried out to optimize the properties of alkali modified breadfruit peel flour-low-density polyethylene (BPF-LDPE) composite. The BPF-LDPE composite was produced for both alkalized with NaOH (NS-BPF-LDPE) and unmodified (UN-BPF-LDPE) composite by compounding bread fruit peel fiber (BPF) and low-density polyethylene (LDPE). The BPF was blended at 5–25 wt.% fiber content (A 1) and 20–100 mesh (850–150 µm) particle size (A 2). The variation of A 1 and A 2 on the tensile strength (U TS), stretching modulus (U TM), elongation (U E), flexural strength (U FS), bending modulus (U FM), hardness (U H), Impact strength (U IS) and water absorption resistivity (U WAR) of the BPF-LDPE composite were verified, respectively. Response surface methodology (RSM) was implemented for this process. The scanning electron microscope (SEM) was tested on NS-BPF-LDPE and UN-BPF-LDPE composite, respectively. The results noted that at optimal state, A 1, A 2, U TS, U E, U TM, U FS, U FM, U H, U IS and U WAR, were 150 µm (100 mesh), 25 wt.%, 7.638322 MPa, 8.105433 %, 0.341301 GPa, 23.48253 MPa, 0.331741 GPa, 167.2593 Pa, 45.28871 kJ m−2 and 4.730205 %, respectively. After the modeling process, the error detected from experimental related results and that RSM was <2.9445 %. All the RSM predicted responses attributed significant correlation indicating good prediction of NS-BPF-LDPE composite in production of engineering component.

Shape Memory PLA/TPU Blend Using High-Speed Thermo-Kinetic Mixing.

In this study, a thorough examination of the chemical, thermal, and mechanical characteristics, as well as shape memory behavior at low temperatures, of blends consisting of polylactic acid (PLA) and polyurethane (TPU) is conducted. The research involves the preparation of PLA/TPU mixtures with varying concentrations of TPU using a high-speed thermo-kinetic mixing approach. Chemical, morphological, and thermal analyses were conducted on pure PLA, TPU, and PLA/TPU mixtures by using Fourier Transform Infrared (FTIR), X-ray diffraction pattern spectroscopy (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA). Mechanical properties were assessed through tensile and three-point bending tests. The achievement of a uniform mixture is confirmed through SEM images, reduction in the glass transition temperature according to DSC and DMA, and an improvement in mechanical properties compared to results documented in the literature, implying a more effective mixing method for the compounds. To assess the practical applicability of this blend, an investigation into the shape memory properties of the mixture when deformed at low temperatures, i.e., cold programming) is carried out. Gray relational analysis (GRA) is employed to identify the optimal TPU content for the mixture, considering both mechanical and shape memory properties. The results indicate that a mixture with a 20% volume fraction of TPU exhibits mechanical properties comparable to those of pure PLA, along with sufficient flexibility at room temperature and notable shape recovery properties.

Microfluidic Electrospinning Core-Shell Nanofibers for Anti-Corrosion Coatings With Efficient Self-Healing Properties.

Self-healing materials have been extensively explored in metal anti-corrosion fields. However, improving the self-healing efficiency remains a significant work that severely limits their further development. Here, a strategy to fabricate anti-corrosion coatings with efficient self-healing properties based on microfluidic electrospinning technologies and UV-curable healing agents is reported. The damaged composite coating contains core-shell nanofibers that can be completely healed within only 30min, indicating an outstanding healing efficiency. The corrosion current density (Icorr) of the composite coatings containing core-shell nanofibers (abbreviated as composite coatings) is lower than the coatings without any fibers (abbreviated as pure resin coatings) during the test of repeated damage and healing cycles, showing superior resistance to corrosion and repeated self-healing property. The composite coating has even better mechanical properties such as tensile strength, bending strength, and impact strength than the pure resin coating, which are explained by simulating the deformation process. These excellent properties greatly improve the practicability of self-healing coatings in the application of anti-corrosion, especially in some special fields.

Modification of mechanical and microstructural characteristics into Ti‐6Al‐4V alloy by thermal treatment

Purpose The purpose of this study is to analyze the titanium alloy under heat treated condition. Titanium alloy heat treatment, particularly Ti‐6Al‐4V alloy, has been an important field of study due to its wide variety of uses in the aerospace, automotive, and biomedical sectors. The mechanical characteristics of titanium alloys are heavily influenced by their microstructure. Cold‐rolled Ti‐alloys have strong bending and tensile strength due to extensive β‐phase precipitation on the α matrix. However, various heat treatment (HT) methods can affect the mechanical characteristics. The current study seeks to investigate the effects of various heat treatment procedures on the microstructural and mechanical changes of Ti‐6Al‐4V alloy, in order to achieve an optimal balance of strength, hardness, and ductility for a variety of real-world applications. Design/methodology/approach Three plates of Ti‐6Al‐4V alloy were heated above the β‐transus temperature for a certain period and then cooled via furnace, air, and sand. One extra plate was kept in ‘untreated’ condition and given name ‘as received’ plate. The three heat treated plates were evaluated and compared with ‘as received’ plate based on tensile strength, bending strength, hardness, and microstructural changes. Findings A considerable change in orientation of α and β was noted through optical microscopy upon heat treatment. The mechanical testing revealed that all the cooling methods adopted in the study have reduced the UTS and increased the YS of the plates. The ductility of the alloy was primarily enhanced by 'air cooling' and 'sand cooling' methods. Originality/value Notably, the hardness test findings indicated a significant drop in hardness for the ‘sand‐cooled’ sample. Furthermore, the ‘air cooled’ sample showed the maximum hardness due to the production of acicular α regions.

Evaluation of Tensile and Compression Bending Moment of L-Type Joints With 3D Printed Connectors

The paper investigates the bending moments under diagonal tensile and diagonal compression loads of L-type corner joints made of three wooden parts corresponding to the leg and the two stretchers used in chair construction. The wooden parts were jointed together with a 3D printed connector made of polylactic acid (PLA) filaments using Filament Fused Fabrication (FFF) as additive manufacturing technology. Larch (Larix decidua Mill.) wood was used to manufacture the wooden elements. In order to assess how the model orientation on the build platform influences the mechanical performance of the printed connector, two print positions were taken into account during the additive manufacturing (AM) process, namely horizontal and vertical. Mechanical testing under diagonal tensile and compression loads of the L-type corner joints, followed by the microscopic investigation of the fractured connectors with magnifications 50X, 80X, 100X were employed in this study. The results were compared with those of the reference L-type corner joint consisting of common mortise-tenon jointed wooden elements. The results show that the vertical orientation of the model on the build platform of the 3D printer is preferred for a better mechanical performance. The microscopy of the fractured connectors revealed the interlayer delamination of the filaments, especially in the case of the horizontal orientation of the model, which caused the wooden parts to slide out of the connector and record low values of the maximum failure loads.

Investigation of Mechanical Properties and Color Changes of 3D-Printed Parts with Different Infill Ratios and Colors After Aging.

Since their inception, plastics have become indispensable materials. However, plastics used for extended periods in industrial applications are prone to aging, which negatively impacts their material behavior and performance. To ensure the long-term usability of these materials, they must be tested in real-time, in-service environments to assess degradation. In practice, however, accelerated aging techniques are commonly employed to avoid time loss. Over time, various indicators of degradation in plastics emerge, such as changes in molecular weight, cracking, and mechanical properties like strain at break and impact strength. Among these, color deterioration or change is a critical factor that helps evaluate the service life of these materials. Considering the increasing use of plastics in 3D printing today, and the growing focus on strength over aesthetics in these applications, it is particularly useful to evaluate aging in plastics based on the relationship between color and strength. The wide application of 3D printing in various industries necessitates understanding material properties under aging conditions. This study examines the effects of aging on the mechanical behavior of polylactic acid (PLA) with three different colors (yellow, orange, and red) and three different infill ratios (20%, 60%, and 100%). The samples underwent an accelerated aging process of 432 h, which included 8 h of UV radiation, 15 min of water spraying, followed by 3 h and 45 min with the UV lamps turned off. Tensile tests, bending tests, hardness measurements, and color evaluations were conducted on the samples, linking the color changes after aging with the materials' mechanical properties. The results show that after aging, yellow samples with a 100% infill ratio exhibited a 6.9% increase in tensile strength (44.50 MPa to 47.58 MPa). Orange samples with a 100% infill ratio were less affected by aging, while red samples experienced a decrease in tensile strength across all infill ratios. Regarding bending force, increases were observed in the orange, yellow, and red samples by 10.37%, 25.05%, and 8.87%, respectively. This study underscores the importance of color selection when designing 3D-printed materials for long-term applications.

Study on mechanical properties of deposited metallic objects for different build strategies using semi-automatic welding setup

Gas metal arc welding-based metal printing is an effective tool to fabricate complex prototypes and tangibles products having enormous advantages such as low cost and minimum lead time for widespread engineering applications in the developed industry. Gas metal arc welding-based metal-deposition was implemented to build three dimensional specimens with varying cross-sections through different paths strategies, that is, spiral-in (circular and square) and raster (square, diagonal and circular). The given trajectory was followed by providing programmed inputs to the controller of the setup to deposit metal layer over the layer for producing a positive slope on the lower half and a negative slope on the upper half section of the deposited object. The fabricated setup can be used to produce sloped objects having 20° inclination. The mechanical properties such as tensile strength, bending strength and microhardness of the deposited 3D parts were investigated to observe the effect of different depositing strategies. Amongst the various deposition strategies adopted to build parts, the raster diagonal (square) and raster linear (circular) showed the maximum value of tensile and bending strength. The microstructural characterization of the deposited parts was also carried out using scanning electron microscopy (SEM).

Study of the failure characteristics and mechanical response of railway tunnel under oblique-slip fault displacement

When a tunnel intersects an active fault, the dislocation of the fault often leads to failures such as lining fractures and structural deformations, severely threatening the safe operation of the tunnel. To investigate the fracture characteristics and mechanical responses of tunnels under oblique-slip fault conditions, a large-scale indoor model test with a geometric similarity ratio of 1:35 was conducted. This study was based on a railway tunnel in Western China that crosses an oblique-slip active fault. Additionally, a three-dimensional model of the tunnel-surrounding rock-fault fracture zone interaction was established using ABAQUS finite element analysis software. The purpose of this study is to clarify the structural cracking characteristics, deformation modes, strain trends, changes in bending moment and shear force of tunnels under fault displacement, as well as the contact force between tunnels and surrounding rocks, and further reveal the differences in the impact of oblique-slip faults and other types of faults on tunnels. The results indicate that under oblique-slip fault dislocation, the tunnel experiences shear failure at the fault fracture zone manifested as shear diagonal cracks. Tensile bending failures, characterized by bending circumferential cracks, occur at the hanging wall and footwall. At the fault fracture zone, the strain, contact pressure, bending moment, and shear force of the tunnel undergo drastic changes and peak values appear. The tunnel exhibits distinct three-dimensional failure characteristics, including horizontal bending, axial stretching and twisting, and vertical shearing. The damage zone of the tunnel extends approximately 2D (where D is the tunnel diameter) from both the hanging wall and footwall towards the fault fracture zone, with the severity of damage increasing closer to the fault fracture zone. The damage process of the tunnel under increasing fault dislocation displacement can be divided into three stages: initial intact stage, onset of damage stage, and complete failure stage. When the strike-slip dislocation reaches 20.7 mm (corresponding to an actual displacement of 724.5 mm), structural damage accumulates to its limit, leading to large-scale failure of the tunnel. Compared to purely strike-slip faults, the tunnel is more prone to damage and exhibits a larger range of structural failure under oblique-slip fault dislocation. These findings provide scientific and rational data support and reference for disaster prevention and mitigation design of tunnels.

Mechanical properties and failure mechanisms of 3D layer‐to‐layer interlock woven composites

AbstractThree‐dimensional layer‐to‐layer interlock woven composites (3D LTLIWCs) have been widely used in various aero‐engine blade models because of their excellent near‐net forming capabilities for complex components, as well as significant advantages in structural design flexibility and high damage tolerance. In this paper, a typical and two new 3D LTLIWCs, specifically including 1/3 twill (S‐I), modified satin (S‐II), and stuffer twill (S‐III), were manufactured by two design methods: varying interweaving frequency and introducing stuffer yarns. Three‐point bending and uniaxial tensile tests were conducted along the 0° (warp) and 90° (weft) directions. The damage morphology and failure mechanism of the specimens were revealed by nondestructive testing technology and topological structure analysis. The results showed that the fabric structure significantly influenced the mechanical properties and failure mechanisms of the 3D LTLIWCs. Compared with S‐I and S‐II, S‐III demonstrated a 17.9%–80.2% increase in bending strength and a 35.3%–162.8% increase in tensile strength in the 0° direction, while the bending strength and tensile strength in the 90° direction increased by 1.1%–73.3% and 9.3%–50.4%, respectively. Notably, S‐III exhibited lower bending and tensile damage in the 0° direction than S‐I and S‐II, with a smaller propagation range of resin and interface cracks and less severe shear fracture of the load‐bearing yarns. This study can provide a useful reference for the optimal design of fabric structure for 3D woven composite blades.Highlights Two design schemes for optimizing 3D LTLI fabric structure were compared. Introducing stuffer yarns improved the mechanical properties of 3D LTLIWCs. S‐III composites exhibited the highest failure strength in all test directions. Full‐field strain distribution was closely related to the interlocking patterns. Fabric structures had a great influence on the failure modes of 3D LTLIWCs.

Study on the mechanical properties of layered gradient structure PBT-based flame retardant composite materials

Abstract To enhance the flame retardancy of Polybutylene Terephthalate (PBT) based composite materials and overcome the decrease in mechanical properties due to the high content of nano-antimony trioxide (nano-Sb2O3), this study initially applies a composite modification method to treat the surface of nano-Sb2O3. Subsequently, composite materials with a gradient distribution of nano-Sb2O3 are prepared through lamination hot-pressing technology, and their mechanical and flame retardant properties are investigated. The results show that the modifiers CTAB and KH560 are successfully grafted onto the surface of nano-Sb2O3, altering its surface properties. Through lamination hot-pressing technology, a gradient distribution from the surface to the core is achieved. Compared to the homogeneous distribution P666, G828 exhibits a 6% increase in Limiting Oxygen Index (LOI), improving the flame retardancy of the composite material. As nano-Sb2O3 enriches on the composite material's surface, the amount of char residue increases. The tensile strength, bending strength, and impact strength of G828 composite material increase by 19.7%, 37.1%, and 103%, respectively, compared to the homogeneous composite material P666, proving the significant effect of G828's gradient distribution in enhancing the mechanical properties of the composite material.

WASTE EGGSHELL AND SAWDUST AS REINFORCEMENTS FOR SUSTAINABLE POLYESTER COMPOSITES: MECHANICAL CHARACTERIZATION AND ENVIRONMENTAL DURABILITY ASSESSMENT

This research endeavor undertakes an experimental investigation into the bending and tensile properties of polyester composites reinforced with waste eggshell powder and sawdust particles at 35 wt.%. Valorizing these waste materials as reinforcements contributes to sustainable practices, waste minimization, and environmental pollution mitigation. Composite samples were fabricated using hand lay-up and compression molding techniques. The effects of environmental exposure to water, acidic, and basic media immersion on the mechanical performance were evaluated to assess durability. Experimental characterization through tensile and three-point bending tests determined mechanical properties, stress-strain behavior, and failure mechanisms. Additionally, finite element analysis (FEA) simulations complemented the experiments by providing insights into stress distributions, deformations, and potential failure initiation sites within the composites under flexural loading. The computational models accurately captured the reinforcing effects of the waste materials and the degradation induced by environmental exposure, validating the experimental trends. Incorporating waste natural fibers significantly enhanced polyester's bending strength by 140% (sawdust) and 75% (eggshell), and tensile strength by 13% (sawdust) and 10% (eggshell). However, environmental exposure degraded properties to varying extents, with water immersion reducing tensile strength by 63% (sawdust) and 3% (eggshell), and flexural strength by 63% (sawdust) and 3% (eggshell). The acidic medium caused 58% (sawdust) and 23% (eggshell) reductions in tensile strength, and similar flexural strength degradations. Strikingly, the basic medium decreased eggshell composite tensile strength by 170% and flexural strength by 6%, while sawdust composite strengths declined by 44%.

Behavior of laminated bamboo columns under low cyclic reversed loading

Laminated bamboo, a type of eco-friendly engineered bamboo product, is increasingly gaining attention in the field of civil engineering. Although there has been considerable research on the material properties of laminated bamboo, studies focusing on the seismic performance of laminated bamboo columns are still relatively scarce. This paper discusses in detail the behavior of laminated bamboo columns and BFRP (Basalt fiber reinforced polymer) reinforced laminated bamboo columns under low cyclic reversed loading. In particular, the effects of slenderness ratio and axial compression ratio on laminated bamboo columns and BFRP reinforced laminated bamboo columns are studied. The hysteresis behavior of the column specimens is first tested through experiments. The results show that under low cyclic reverse loading, the failure of laminated bamboo columns is due to the tensile fracture and compressive bending of bamboo strips, as well as the tensile fracture of BFRP. To quantify the mechanical performance of laminated bamboo columns, parameters of interest are defined and discussed, including load-bearing capacity, stiffness, energy dissipation, and equivalent viscous damping. The load-bearing capacity and stiffness of laminated bamboo columns and BFRP reinforced laminated bamboo columns are significantly affected by the slenderness ratio and axial compression ratio. The yield loads for the column specimens with slenderness ratios of 37.0, 63.4, and 77.5 are within the ranges of 2.08–7.64 kN, 1.63–5.15 kN, and 1.82–7.51 kN, respectively. Laminated bamboo columns exhibit a satisfactory energy dissipation, with the maximum observed equivalent viscous damping exceeding 50 %. Furthermore, combining theoretical calculations and fitting analysis, bilinear skeleton curve models for both laminated bamboo columns and BFRP reinforced laminated bamboo columns are presented, showing a good agreement with experimental results. This research aims to provide some references for the design of laminated bamboo structures in future practical engineering.

A feasibility study on improving the crack resistance of thin-walled UHPC members by reinforcement with Fe-SMA wires

To investigate the potential for further enhancing the cracking resistance of thin-walled UHPC by prestressing, the uniaxial tensile and three-point bending experiments for UHPC specimens reinforced with iron-based shape memory alloy (Fe-SMA) wires were conducted. The specimens were placed in an oven and heated to 150 °C, 200 °C, and 250 °C, which was intended to activate the Fe-SMA wires to produce self-prestress. The characteristics of different reinforced methods and heating temperatures were systematically compared. The cracking load and the crack development were recorded using Digital Image Correlation (DIC) techniques. The result shows that at the temperature of 150 ºC, compared to the dog-bone shaped specimens without reinforcement and the specimens with steel wires, the mean cracking load of specimens with Fe-SMA wires was enhanced by 13.4% and 9.8%, respectively. The study preliminary verified that this method can activate Fe-SMA inside UHPC.

Anti-interference flexible temperature-sensitive/strain-sensing aerogel fiber for cooperative monitoring of human body temperature and movement information

In recent years, multi-functional flexible sensing fibers capable of detecting various physical and chemical stimuli capabilities have made significant advancements. However, the cross-sensitivity of the sensing materials to other stimuli can considerably reduce their sensitivity and accuracy of these multifunctional fibers. In this study, we initially fabricated a blending type (BAF) and a core-sheath type (CAF) strain-sensing aerogel fiber using an optimized one-step wet spinning process. Then, we coated the aerogel fiber with cholesteric liquid crystal as the middle layer and waterborne polyurethane as the outer layer to obtain a temperature-sensitive/strain-sensing aerogel fiber (TSAF). TSAF demonstrates distinct multi-model strain sensing performance, enabling the detection of tensile strains (0.1–111.5 %), bending strains (40°–160°), and compression strains. Moreover, within the ultra-narrow temperature range of 34 °C–38 °C, TSAF undergoes reversible color transformations from yellow-green-blue-purple, against both bright and dark backgrounds. This unique feature offered high sensitivity, rapid response time, and diverse color variations. By integrating fibers into clothing, a collaborative sensing system can be established to simultaneously monitor human physiology and movement information. These advancements hold significant potential for applications in smart clothing, medical care, and other fields.

Preparation of phosphorous ionic liquids and its effect on the properties of ABS

AbstractTo improve the thermal conductivity and mechanical properties of graphene‐acrylonitrile butadiene‐styrene plastic (ABS) composite, sub‐phosphite‐based ionic liquid (IL) was synthesized, and its structure was characterized by FTIR, NMR, and mass spectrometry. IL was as a modifier, and graphite powder (G powder) was modified by the ball milling method to obtain functional graphene thermal conductive filler (G‐IL). The structure and morphology of G‐IL were characterized by FTIR, X‐ray photoelectron spectroscopy (XPS), XRD, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results of the Molau test showed that the presence of IL improved the interfacial interaction of G‐IL and ABS, enhanced the dispersion of G‐IL in the ABS matrix, made G‐IL contact with each other, and it was easier to establish a thermal conduction network and promote phonon transfer. The thermal conductivity of 9 wt% G‐IL/ABS composite was 0.392 W·m−1·k−1, which was 96% and 14% higher than that of pure ABS and G/ABS composite, respectively. The tensile strength and bending modulus of 9 wt% G‐IL/ABS composite were 44.89 and 2124.37 MPa, which were 13% and 11% higher than those of pure ABS, respectively. The impact strength of 9 wt% G‐IL/ABS composite was 34.17 kJ/m2. It was 18% and 7% higher than that of pure ABS and 9 wt% G‐IL/ABS, respectively.Highlights Phosphorus imidazole ionic liquids were prepared. Graphene was modified by ionic liquids through non‐covalent. Enhanced mechanical properties and thermal conductivity of G‐IL/ABS composites.

Correlating FDM printing parameters with mechanical properties and surface quality of PLA printouts

Abstract This study explores the correlation between four critical Fused Deposition Modeling (FDM) parameters—extrusion temperature, layer height, print speed, and infill density—and the mechanical properties and surface quality of PLA (Polylactic Acid) printouts. The mechanical properties, including Young’s modulus, tensile strength, and bending strength, were evaluated alongside surface roughness and dimensional accuracy. The results indicate that extrusion temperatures between 200°C and 220°C optimize mechanical performance, enhancing tensile strength and bending strength, while smaller layer heights (0.1 mm) improve surface smoothness but increase print time. Moderate print speeds (around 60 mm/s) offer the best balance between strength and efficiency, while higher infill densities (above 80%) enhance mechanical properties, increasing both tensile and bending strength by up to 25%. These findings provide key insights into optimizing FDM printing parameters to achieve improved structural integrity and aesthetic quality in PLA prints.

2D heterostructures of graphene oxide and MoS2 to improve sensitivity performance of flexible pressure sensor with shell biological structure

Inspired by the multilayer structure of the shellfish, a novel two-dimensional (2D) composite structure consisting of graphene oxide, MoS2 and graphene oxide (G/M/G) was integrated to the flexible pressure sensing. The composite structure was prepared by the vacuum suction filtration in order to imitate the high toughness of shellfish. Based on the strategy of strain engineering, a comprehensive experimental bench capable of meeting different strain conditions was connected to a push–pull meter and an LCR digital bridge, and then a computer was used to record the changes in transducer capacitance when an external load was applied to the meter. Graphene oxide (GO) and G/M/G supercells were constructed, and density functional theory (DFT) simulations of the initial energy band structure under strain-free conditions were carried out to determine the relationship between the band gap, conductivity, capacitance, and sensitivity of the G/M/G structure based on band gap theory, and to easily understand the mechanism of the shellfish heterostructure leading to enhanced sensitivity of the sensors. Using two-point bending and axial tensile tests, a flexible pressure sensing device was designed to realize positive strains in the ranges of 0%–5 % and 5%–50 %. The results show that the sensitivity of both GO and G/M/G capacitive pressure sensors decreased with increased strain, and the sensitivity of the G/M/G sensors was significantly improved by 75%–102 % compared to the GO sensors at the same strain. The parallel-plate capacitor model and crack growth theory well explain the experimental results at small and large strains. Our results provide new concepts for the design of novel flexible sonar with high sensitivity and large strain operating range by a simple vacuum filtration method, which can be extended to the design of other high-performance 2D flexible electronic devices.

Enhancing microwave absorption of bio-inspired structure through 3D printed concentric infill pattern

Despite numerous reports on microwave absorbing materials and structures with excellent performance, research on the impact of the carrier of microwave absorbers and their preparation processes on microwave absorption performance still faces challenges. To address this issue, this study combines theoretical analysis, simulation, and experimental validation to compare the differences in microwave absorption performance between 3D printed ABS/CF/MWCNTs materials and traditionally cast paraffin/CF/MWCNTs materials. Furthermore, the study explores the impact of linear and concentric filling patterns in 3D printing processes on the performance of tree-shaped microwave absorbing meta-structures. From a material level perspective, the 3D printed ABS/CF/MWCNTs composite plate with a thickness of 3 mm has an effective absorption bandwidth of 5.16 GHz. Additionally, the bio-inspired tree-shaped structure optimized by the ant colony algorithm achieves an effective absorption bandwidth of up to 11.5 GHz at a thickness of 10.8 mm, with a minimum reflection loss of less than −9 dB across the entire frequency range (2–18 GHz). Moreover, the microwave absorbing meta-structure reinforced with carbon fiber-reinforced plastic laminates exhibits outstanding tensile and bending strength, with an average tensile strength and bending strength reaching 197.7 MPa and 188.6 MPa, respectively. In summary, this study provides valuable insights into the optimization of preparation processes for microwave absorbing materials or structures and offers a scientific basis for the design and application of high-performance microwave absorbing materials.

Istraživanje utjecaja zelenih hibridnih vlakana na žilavost i mehanička svojstva betona od pijeska željezne jalovine

To improve the brittleness and susceptibility to cracking of iron tailings sand concrete, fibre blending was employed to toughen and resist cracking in the material. In this study, two inexpensive and environmentally friendly fibre materials were used: recycled tire steel fibre (RTSF) and coconut fibre (CF). The two fibre materials were blended and the resulting mixture was subjected to a series of performance tests, including compressive, tensile, flexural, impact, and bending tests. The effects of the fibre doping method and amount on the toughness and mechanical properties of iron tailings sand concrete were investigated in terms of the law of effect of the blended fibre admixture on the toughness and mechanical properties of iron tailings sand concrete. The results show that adding two types of fibres can effectively improve the toughness and mechanical properties of the specimen, and the hybrid fibre has a more obvious effect. Compared with the blank control group (Non), the compressive strength, splitting tensile strength, bending strength, impact strength, and bending peak load of the concrete with 0.75 % RTSF and 0.2 % CF increased by 20.8 %, 42.9 %, 40.4 %, 92.4 %, and 37.5 %, respectively. Combined with the theory and fracture surface morphology analysis, it was shown that recycled tire steel fibres play a major role in cracking resistance, while coconut fibres play a toughening role.

Experiments and Modeling of Three-Dimensionally Printed Sandwich Composite Based on ULTEM 9085.

This article presents the concept, research, and modeling of a sandwich composite made from ULTEM 9085 and polycarbonate (PC). ULTEM 9085 is relatively expensive compared to polycarbonate, and the composite structure made of these two materials allows for maintaining the physical properties of ULTEM while reducing the overall costs. The composite consisted of outer layers made of ULTEM 9085 and a core made of polycarbonate. Each layer was 3D-printed using the fused filament fabrication (FFF) technology, which enables nearly unlimited design flexibility. The geometry of the test specimens corresponds to the ISO 527-4 standard. Tensile and three-point bending tests were conducted. The structure was modeled in a simplified manner using averaged stiffness values, and with the classical laminate theory (CLT). The models were calibrated through tensile and bending tests on ULTEM and polycarbonate prints. The simulation results were compared with experimental data, demonstrating good accuracy. The 3D-printed ULTEM-PC-ULTEM composite exhibits favorable mechanical properties, making it a promising material for cost-effective engineering applications.