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To further enhance the ablation resistance of C/C composites, solid solution ceramic Ta0·2Zr0·8C was used to replace traditional ultra-high-temperature ceramic carbides for matrix modification of C/C composites. The C/C–Ta0.2Zr0·8C–SiC composite was fabricated by a high-solid-loading slurry impregnation combined with the precursor infiltration and pyrolysis process. The comparative samples of C/C–ZrC–SiC and C/C–TaC–SiC were also prepared using these same technologies. The microstructure, flexural properties, and ablation performance of the composite were investigated. Results showed that the C/C–Ta0.2Zr0·8C–SiC exhibited excellent overall flexural properties. During the ablation test under an oxyacetylene flame with high heat flux, the ablation resistance of C/C–Ta0.2Zr0·8C–SiC improved with prolonged ablation time, reaching mass and linear ablation rates of 0.67 mg/s and 0.18 μm/s after 120 s of ablation. Compared to the C/C–ZrC–SiC and C/C–TaC–SiC, the mass ablation rate of the composite was reduced by 49.24% and 68.70%, and the linear ablation rate was reduced by 97.22% and 97.71%, respectively. The enhanced ablation resistance was primarily attributed to the formation of the Ta–Zr–O oxide layer, composed of TaZr2·75O8, ZrO2, and Ta2O5, on the composites surface. In the oxide layer, the Ta-rich oxides served as a binder, filling gaps in the interface. Meanwhile, the Zr-rich oxides formed the skeleton that pinned the molten liquid oxides. The combined effects of Ta-rich and Zr-rich oxides made the Ta–Zr–O oxide layer more compact and strongly bonded to the matrix.

Abstract The adoption of pultruded glass fibre-reinforced polymer (pGFRP) composites as a substitute for traditional wooden cross-arms in high transmission towers represents a relatively novel approach. These materials were selected for their high strength-to-weight ratio and lightweight properties. Despite various studies focusing on structures improvement, there still have a significant gap in understanding the deformation characteristics of full-scale cross-arms under actual operational loads. Existing study often concentrate on small coupon scale and laboratory condition, leaving a gap in understanding how the cross-arm behavior in full-scale acting on actual weather condition. This study aims to investigate the load-deflection and long-term creep behavior of a pGFRP cross-arm installed in a 132 kV transmission tower. The pGFRP cross-arm was load-tested on a customized rig in an open environment. Using the cantilever beam concept, deflection was analyzed and compared to wood cross-arms. Finite element analysis validated results, and long-term deformation under high-stress loads was assessed. The pGFRP cross-arms showed lower deflection at working loads compared to Balau wood, due to the latter’s higher elastic modulus and flexibility specifically at Point Y3, the critical issues necessitated reinforcement strategies. pGFRP cross-arms withstood higher bending stress, showing 32% less deflection under normal conditions and 15% less under broken wire conditions than Balau wood. Additionally, the creep strength of wood was 34% lower than that of pGFRP cross-arms. Besides that, the pGFRP cross-arm have highest elastic modulus than Balau-wood, shows that the composite cross-arm have better structural strength, resisting deformation and higher flexibility materials. Finite element analysis (FEA) confirmed these results with the relative error between them less than 1%. Consequently, the investigation into pGFRP cross-arm deformation behavior in this paper serves as a foundational framework for future research endeavors specifically for high transmission tower and other structural application.

The Fused Filament Fabrication is an economic 3D printing process to produce lightweight polymers-based structures. Therefore, it is drawing a consistently increasing interest from industry and researchers. Flexural and impact properties are two of the critical performance measures for gauging the integrity of the printed structures. Since 2014, numerous studies have been carried out on this topic, however, their holistic overview with a focus on the flexural and impact properties has been barely presented in the literature. The current article reviews the relationship between the process parameters, both operating and geometrical, and these properties in detail. The cause-effect relationship is thoroughly examined considering material effect. This allows the identification of the complex interactive effects and conducive ranges of the important parameters to effectively control the process for achieving the desired mechanical properties. The review establishes that the crystallinity of post-printed polymers is a crucial factor in controlling the mechanical properties, and filled polymers generally offer better properties than unfilled ones if the right filler given the desired properties is chosen. Topology optimization, recyclability of polymers through FFF, and retention of polymer properties after printing are also discussed as innovative trends. Finally, limitations and research gaps are identified, and the latest ideas are proposed as a way forward for further development of the FFF technology.

Pultruded glass fibre reinforced polymer composite is used as a cross-arm material in high-rise transmission tower application to suspend insulators, conductor cables and vibration dampeners. Due to long-term static loading conditions, they fail due to incompetency in the cross-arm's mechanical properties. This study establishes a feasible method to improve the service life by retrofitting a sleeve reinforcement, sandwiching the composite fastened by bolting, to strengthen the overall structure. This study is focused, at the coupon scale level, to determine the influence of this structural element upon the elastic mechanical properties under instantaneous and creep load conditions. The composite material and the stainless steel sleeve are fabricated using waterjet machining and laser cutting respectively. A comparative study among the virgin and varying lengths of sleeve reinforced composite is established for homogenizing this concept at the actual scale applications. It has been observed that the composite reinforced with the sleeve of 100% length as that of the composite specimen showed enhancement in its flexural elastic moduli by about 178% and 138% under instantaneous and creep load conditions as compared to its virgin counterpart. The Findley numerical model in compliance with creep results was used to generate equations to predict the deterioration of mechanical properties. This data helps to determine the functional service life of the composite in actual application. The sleeve installation has been found to increase the bending strength thereby resulting in reduced strain and promoting localized encapsulation, resilience, toughness, load transfer capability and creep strain resistance of the PGFRP composite.

Extensive research has been performed on the tensile properties of carbon fibre-reinforced polymer (CFRP) material used in both standalone and rehabilitation applications. Limited knowledge and design guidelines exist on the flexural behaviour of CFRP cable strands (herein strand) and reinforcing bars. This knowledge gap hinders the widespread use of strands and CFRP bars in prestressed structures and restricts their market share compared to reinforcing steel members. To address this gap, this study investigates the flexural behaviour of CFRP strands and reinforcing bars using a combination of experimental and numerical methods. A standard three-point bending test is employed to measure the flexural strength and ultimate curvature radius of strands and bars. The experimental study included strands of diameters 10.2 mm and 15.2 mm, and CFRP bars of diameters 9 mm, 12 mm, and 14 mm. Finite element analysis has been conducted to further investigate the flexural performance and failure mechanisms of the specimens. The test results indicate that the ultimate bending radius of the strands is approximately one-half of that of the bar, while their ultimate bending strength surpasses the bars by at least 10 %. Optimal lay lengths for the 10.2 mm and 15.2 mm cable strands are proposed based on the simulation results.

Ceramic materials, while strong, often lack flexibility and energy absorption. Inspired by tough natural structures like nacre, toughening strategies have shown significant potential in ceramic materials. This study investigates the static and cyclic flexural properties (i.e., energy absorption, stiffness, and strength) of the bioinspired ceramic-polymer composites, particularly concerning the influence of macro and micro patterns. Using a subtractive manufacturing platform enabled by ultra-short pulsed picosecond lasers, we engrave a range of macro and micro patterns onto alumina tiles, mimicking natural armor designs. The composites are then fabricated by stacking laser-engraved tiles with an interlayer of Surlyn®, a commercial monomer. The results demonstrate that the static/cyclic performance and toughening mechanisms are closely linked to the lasered bioinspired surface patterns and stacking sequence. Specific macro architectures and stacking sequences led to significantly increased energy absorption (up to 85%) through mechanisms like crack deflection and plastic deformation of the soft phase. Micro patterns, on the other hand, improved the ceramic's strength (up to 140%) by influencing how the materials interact at the interface. This research not only advances our understanding of bioinspired armor but also paves the way for a new generation of ceramic composites with superior properties, targeting applications in defense (aerospace and vehicle armor) and personal protective equipment (PPE).

In this study, the thermal and mechanical characteristics of bamboo fiber-reinforced greenpoxy matrix composites were evaluated by varying the fiber loading from 30wt.% to 60wt.% during the compression molding process. The thermal behavior using dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA) and their impact and flexural properties of the composites were studied. The results indicate that thermal characterization, the highest peak E’ was observed: B-40 > B-60 > B-30 > B-50, while the peak E’‘ was found to be B-40 > B-30 > B-60 > B-50. The order for tan delta was B-30 > B-40 > B-50 > B-60. The TGA results indicated improved thermal stability with increasing fiber loading, as evidenced by higher residue % and lower weight loss %. Regarding the mechanical properties the impact strength of the composites increased with increasing fiber loading, with the maximum value of 8435.33 J/m2 at 50wt.%. The composite with a 60wt.% fiber loading showed the highest flexural modulus (4.70GPa), while the flexural strength improved at 40wt.%. The SEM analysis of fractured specimens from flexural tests of composite materials with varying fiber volume fractions revealed that an optimal balance between fiber and matrix resin enhanced mechanical properties.

The study investigated the influence of flexural properties of bamboo spoon raw materials of different ages, parts, and moisture contents on the processing of bamboo spoon. By using the three-point bending test method, the flexural properties and fracture mechanisms of bamboo spoon made from different raw materials under different moisture conditions were analyzed, and the changes in bending performance of raw materials before and after processing into bamboo ladles were compared. The results showed that bamboo spoon had the same bending strength change pattern before and after processing, with better bending after, especially when processed at a moisture content of 10%. In terms of raw materials, bamboo spoon made from bamboo with a age of 7 years in the middle part exhibited the best bending strength. Observation of its fracture mechanism revealed that cracks extended outward when fracture occurred, dissipating energy, thus exhibiting a certain bending toughness during the bending process, while possessing good bending strength and bending toughness at the same time.

Each year, a significant amount of waste is produced from carbon fiber polymer composites at the end of its lifecycle due to extensive use across various applications. Utilizing regenerative carbon fiber as a feedstock material offers a promising and sustainable approach to additive manufacturing based on materials. This study proposes the additive manufacturing of recycled carbon fiber with a polyamide-12 polymer composite. Filaments of recycled carbon fiber-reinforced polyamide-12 (rCF-PA12) with different recycled carbon fiber contents (0%, 10%, and 15% by weight) in the polyamide-12 matrix are developed. These filaments are utilized for 3D printing of specimens by using various infill density parameters (80% and 100%) on a fused deposition modeling 3D printer. The study examined how the fiber content and infill densities influenced the flexural performance of the printed specimens. Notably, the part containing 15 wt% recycled carbon fiber (rCF) composites showed a significant improvement in flexural performance due to enhanced interface bonding and effective fiber alignment. The results indicated that reinforcing the printed part with 10% and 15 wt% recycled carbon fiber (rCF) improved the flexural properties by 49.86% and 91.75%, respectively, compared to the unreinforced printed part under the same infill density and printing parameters. The investigation demonstrates that the additive manufacturing-based technique presents a potential approach to use carbon fiber-reinforced polymers waste and manufacture high-performance engineering, economic, and environmentally friendly industrial applications with the complicated design using different polymer matrices.

Abstract Identifying novel cellulose fiber bio-composites has become a vital initiative in the exploration of sustainable materials due to increased global concern for the environment. This growing focus on eco-friendly materials has gathered significant attention in recent years. The current investigation deals with one such material, Helicteres isora reinforced Polylactic acid composites. Surface chemical treatment of fiber is one of the most effective methods to modify the hydrophilic fiber to increase its compatibility with the polymer matrix. Sodium hydroxide was used as a pre-treatment chemical to remove any impurities from the fiber surface. Pre-treated fibers were treated with Methacryl silane and Potassium permanganate solution to chemically modify the fiber surface. Density, void content and water absorption behavior of the composites were analyzed as per the standard procedure. Tensile and flexural tests were conducted to evaluate the mechanical strength, modulus, and flexibility of the unidirectional composites. Thermogravimetric and differential thermal analyses were performed to investigate the thermal stability, melting behavior and degradation profiles of prepared composites. A study of failure mechanisms and morphology of the fractured surface through photographs and SEM images revealed fiber splitting and delamination as the dominant reasons behind the failure of composites under tensile loading. Silane-treated Helicteres isora fiber-reinforced Polylactic acid composite exhibited lower water absorption and higher tensile strength than its counterparts. Untreated fiber composite showed maximum flexural strength among the tested composites. By collectively evaluating the results of the tests and properties of the composites, silane-treated fiber-reinforced Polylactic acid composites stands out as the most favorable choice.

The objective of this study is to assess the impact of incorporating rubber tire waste and brick fillers as a substitute for sand in cement mortar samples. The evaluation includes measurements of the bending strength, dynamic modulus of elasticity, and displacement. The replacement of sand by rubber waste (RW) and brick waste (BW) at 0%, 10%, 20% and 30% for rubber waste and 0%, 2.5%, 5.0%, 7.5%, and 10% for brick waste by volume was experimentally conducted. According to the findings, the introduction of rubber waste leads to a significant reduction in the flexural strength, dynamic modulus of elasticity, and displacement. The brick waste can be considered a suitable filler, which minimizes the negative effect of rubber tires and tends to result in suitable mixtures. The optimal values (10.10% for the RW and 10% for the BW) showed good agreement with the experimental results, with differences of 1.85%, -4.73%, and -4.48% for the displacement, flexural strength, and dynamic elastic modulus, respectively.

This work investigated the effect of hybridization of flax fabric (FF) with carbon/Kevlar fabric (CK) on the flexural, dynamic mechanical analysis and high velocity impact. Hand lay-up technique was used to fabricated different ratio of flax to carbon/Kevlar hybrid composites, which were hot-pressed and then cured. It was revealed that increase in ratio of CK has improved the flexural properties, storage modulus, loss modulus, energy absorption and ballistic limit of the composites. Interestingly, hybrid composite with ratio 25:75(FF:CK) has highest flexural properties, storage modulus and loss modulus among the other composites. The cole-cole plot and damping factor reveals that hybrid composite with ratio 25:75(FF:CK) has the strongest fibre/matrix adhesion. The hybrid composite with ratio 25:75 (FF:CK) displayed the highest Tg. Based on high velocity impact test, it was shown that there is not much different in energy absorption and ballistic of the hybrid composites compared to plain CK composite. FF/CK hybrid composites have the potential to be used in high performance application such as ballistic helmet.

To investigate the stress state at the joints of two-way reinforced concrete composite slabs, this study conducted static load tests on four two-way concrete composite slabs. The primary focus was on analyzing the effects of lap reinforcement length and cross-sectional height at the joints on the load-bearing capacity, deformation behavior, and crack development of the slabs. The experimental results revealed that increasing the lap reinforcement length and cross-sectional height at the joints significantly enhanced the overall integrity and flexural capacity of the composite slabs, with load-bearing capacity increasing by up to 92.3% and deflection decreasing by as much as 40.2%. Additionally, a finite element model was used to simulate the mechanical behavior of the composite slabs, and the results were compared with experimental data, showing an error margin of within 10%. Based on the validated finite element model, the study further explored key factors influencing the stress performance at the joints of two-way concrete composite slabs and their impact patterns. Finally, the paper proposes a simplified formula for calculating the load-bearing capacity of composite slabs, which enables rapid estimation of slab performance, providing theoretical support and practical guidance for structural engineering and construction practices.

Bamboo fiber was extracted after alkaline treatment, and the mechanical properties of fibers and polymer composites were measured. The results showed that the strength of bamboo fiber was higher when the diameter was smaller. Smaller diameter bamboo fibers were dense, while larger diameter ones were composed of vascular bundles, which contained inside voids and outside parts having insufficient lignification. Tensile tests were conducted on bamboo fibers after heating at constant temperatures, and a significant decrease in mechanical properties was observed at heating temperatures above 250 °C. Bamboo fibers were compounded with PE, PA12, ABS, PA6, and biobased PC (Durabio), and injection-molded to prepare the composite specimens for flexural testing. The composite of polyethylene with 30 wt% bamboo exhibited considerably high flexural modulus compared to pure PE. Nevertheless, a large plastic deformation, which was equivalent to that of pure PE was observed. In other polymer composites, those flexural moduli increased, and degree of plastic deformation decreased dramatically, leading to brittleness. For PA6, which was molded above 250 °C, the increment in flexural modulus by fibers was less than the other composites due to the thermal decomposition of the fibers.

Bamboo fiber was extracted after alkaline treatment, and the mechanical properties of fibers and polymer composites were measured. The results showed that the strength of bamboo fiber was higher when the diameter was smaller. Smaller diameter bamboo fibers were dense, while larger diameter ones were composed of vascular bundles, which contained inside voids and outside parts having insufficient lignification. Tensile tests were conducted on bamboo fibers after heating at constant temperatures, and a significant decrease in mechanical properties was observed at heating temperatures above 250 °C. Bamboo fibers were compounded with PE, PA12, ABS, PA6, and biobased PC (Durabio), and injection-molded to prepare the composite specimens for flexural testing. The composite of polyethylene with 30 wt% bamboo exhibited considerably high flexural modulus compared to pure PE. Nevertheless, a large plastic deformation, which was equivalent to that of pure PE was observed. In other polymer composites, those flexural moduli increased, and degree of plastic deformation decreased dramatically, leading to brittleness. For PA6, which was molded above 250 °C, the increment in flexural modulus by fibers was less than the other composites due to the thermal decomposition of the fibers.

In assessing the bending attributes for geopolymer composites augmented with uni-directional fibers, methodologies aligned with the established American and European standards yield quantifiable values for flexural strength, denoted as σm*, and its corresponding elasticity modulus, E*. Notably, these values exhibit a pronounced dependency on the size of the testing parameters. Specifically, within a judicious range of support span L relative to specimen height H, spanning a ratio of 10 to 40, these metrics can vary by a factor between 2 and 4. By conducting evaluations across an extensive array of H/L ratios and adhering to the protocols set for comparable composites with a plastic matrix, it becomes feasible to determine the definitive flexural elastic modulus E and shear modulus G, both of which can be viewed as size-neutral material traits. A parallel methodology can be employed to deduce size-agnostic values for flexural strength, σm. The established linear relationship between the inverse practical value E* (1/E*) and the squared ratio (H/L)2 is acknowledged. However, a congruent 1/σm* relationship has been recently corroborated experimentally, aligning primarily with Tarnopolsky’s theoretical propositions. The parameter T, defined as the inverse gradient of 1/σm* about (H/L)2, is integral to these findings. Furthermore, the significance of the loading displacement rate is underscored, necessitating a tailored consideration for different scenarios.

Polypropylene (PP) has raised environmental concerns particularly for its depletion of fossil-fuels and contribution to climate change. To lower environmental impacts, PP can be combined with biobased fillers such as calcium carbonate (CaCO3). The mechanical and environmental properties of CaCO3 filled PP have not yet been explored in depth. Therefore, this study examines the aesthetic, tensile, flexural, impact, and environmental (via life cycle assessment) properties of injection moulded CaCO3 filled PP with filler content ranging from 0% to 40% at 5% increments. As filler percentage increased, yield strength decreased (0% CaCO3: 17.68 MPa, 40% CaCO3: 12.73 MPa), but young's modulus, flexural modulus, and impact strength increased (respectively 69%, 51%, and 35% greater than pure PP). Flexural strength increased initially at 5% CaCO3 but then declined as more filler was added. A yellowish hue was observed within all blends which growed stronger with more filler. The addition of CaCO3 reduced the environmental impact for all 11 impact categories. For every 5% of CaCO3 added, the material's global warming potential (GWP) decreased by 100g CO2 eq. per functional unit (1000 cm3) of composite. Abiotic depletion of fossil fuels declined by 32% when 40% CaCO3 was added. In addition to this study, it would be beneficial to explore other factors that affect the properties of CaCO3 filled PP such as particle size, particle distribution, and binding additives.

The objective of this study was to explore the feasibility of employing durian skin fiber (DSF) waste as a reinforcing agent for a composite material composed of glass fiber, carbon fiber and polylactic acid (PLA). We used mixture design methodology and the response surface methodology to determine the optimal proportion of composite material for enhancing flexural strength and flexural modulus. The composite material was prepared using an injection molding process, and the fracture surface was analyzed using scanning electron microscopy (SEM). Using response surface methodology, we established mathematical relationships between composite material parameters and desired responses. Then, we optimized them using multi-objective methods to determine the optimal process parameters. Validation tests show agreement between predicted and actual values. The optimal composite formula has 0.00 wt% glass fiber, 15.66 wt% carbon fiber, 14.34 wt% DSF and 70.00 wt% PLA.

Despite ongoing research efforts aimed at understanding the structural response of steel fiber reinforced concrete (SFRC), there is very limited research on the failure characteristics and mesoscopic damage mechanism of SFRC, specifically when under flexure. In this study, a four-point bending test of plain concrete (PC) and SFRC with different fiber contents is carried out to investigate the flexural performance of SFRC. The crack propagation process, cracking load, ultimate load, and load-deflection curves of PC and SFRC beams are obtained. Additionally, the discrete element method (DEM), using PFC2D 6.0 software, is adopted to explore the mesoscopic properties of PC and SFRC. The test and simulation results of PC and SFRC beams are compared and analyzed, and some conclusions are drawn. The results show that steel fiber can efficiently improve the compressive strength of concrete when the fiber content is 30 kg/m3, and significantly improve the deformation resistance, crack resistance, and flexural capacity of concrete. The refined numerical models of PC and SFRC beams are established based on compressive strength and aggregate screening results. Through the numerical four-point bending test, the mesoscopic mechanical behaviors of models reveal the damage mechanism of SFRC. The horizontally distributed steel fibers bridge both sides of the cracks to resist crack development, and the vertically distributed steel fibers guide the cracks to the place with strong contact, thus resisting crack height development. The test results show that, for flexural properties, the optimal steel fiber content of SFRC is 31 kg/m3.

The magnetic field method for preparing aligned steel fiber-reinforced concrete (ASFRC) by solenoid coil has a limitation, which is that the specimen must be placed inside the solenoid coil, limiting its practical engineering application. To overcome this shortcoming, this study proposes a method for preparing ASFRCs using an external magnetic field created by assembled magnets. A theoretical model is proposed to predict the distribution of the external magnetic field and the orientation coefficient of ASFRCs prepared by assembled magnets. The predicted results are compared with the experimental results to verify the proposed model. Finally, flexural tests are used to compare the mechanical characteristics of ASFRCs prepared using assembled magnets and solenoid coil. The results indicate that the assembled magnets can be used to prepare the ASFRC with an orientation coefficient of 0.9 or higher, and the flexural strength is similar to that of the ASFRC prepared by the solenoid coil.

Industrial recycled steel wires extracted from waste tires can be combined with high-performance mortar by weaving them into a mesh to apply this type of strengthening method, which exhibits high tensile strength, high toughness, and excellent cracking resistance in building structures. This paper presents a flexural behavior study of reinforced concrete (RC) beams under different industrial recycled steel wire working conditions. We examined the resultant steel-wire mesh high-performance mortar, investigating the stiffness, ductility, and load carrying capacity of the experimental beams under different anchorage measures using different mesh types and sizes. The results showed that both the weaving of the recycled industrial steel wire into a mesh and the rebar-planting anchorage measures were effective in preventing the stripping of the strengthening layers, allowing the tensile performance of the recycled industrial steel wire to be fully utilized and the ultimate load capacity of the RC beams to be considerably increased. At the same time, the industrial recycled steel-wire mesh also played an important role in the inhibition of crack development, with the width of the cracks in the strengthening beams decreasing and an overall appearance of ''fine and dense'' character. As the volume of steel bars in industrial recycled steel-wire mesh increases, the ultimate bearing capacity and stiffness of the beam increased. To verify the strengthening effect of industrial recycled steel-wire mesh high-performance mortar on the beams from multiple angles, this study used finite element analysis software to conduct numerical simulation analyses on four of the experimental beams. The damage cloud charts of the specimens from the numerical simulations were compared with experimental failure phenomena, the deviations between the simulated and experimental values of the specimens being within 10%—that is, the simulation results were in good agreement with the experimental results. The use of industrial recycled steel-wire mesh high-performance mortar strengthening could be applied in actual projects, its green low-carbon credentials achieving the purpose of solid-waste utilization as well as providing strong support for China's early realization of carbon neutrality and related strategic objectives. At the same time, the recycling of waste tires could provide a new research direction.

Natural fiber-based composites are essential for the environment in this era of depletion of petroleum resources and for new green environmental rules, as they have limited detrimental behavior or response against the environment. In this paper, firstly, the suitability of replacing glass fiber with natural bamboo fiber in a flax/glass/epoxy hybrid composite under a fixed bending load is investigated using Finite Element Analysis (FEA) software ABAQUS with proper model validation. Finally, five different lay-up sequences of flax/bamboo/epoxy hybrid composite laminate for fixed volume fractions of flax and bamboo strips are investigated numerically to develop design strategies for binary hybrid composite. It is found that the bending stiffness and equivalent modulus of elasticity for model FB-1 are increased by 37.53 % and 37.52 % respectively compared to the base model while the energy absorption for model FB-3 is highest which is 105.89 % higher than the base model. Analysis of various lay-up sequences showed that flexural behavior can be improved by fabricating binary hybrid composites using the concept of a sandwich structure. It is shown that all highly stiff laminas should be placed on the outer sides of the composite to achieve the maximum bending stiffness whereas they should be placed at the center to attain the maximum energy absorption.

Abstract Fused Filament Fabrication (FFF) is a 3D‐printing technique that enables the production of complex geometries with a high level of customization at low cost. The poor mechanical properties of FFF‐printed parts often undermine the application of this technology for structural purposes. To overcome this limitation, a two‐step metallization method is performed to deposit a copper layer on the exterior of an Acrylonitrile–Butadiene–Styrene (ABS) substrate, using a non‐toxic and cost‐effective plating solution. Electroplating over the exposed grid infill, at various densities, is exploited to improve the load transfer between copper and ABS. The resulting samples are characterized mechanically and thermally, and finite element modeling simulations are used to better understand the characterization results. It is found that an infill of 50–60% provides the best compromise between mechanical performance and thermal conductivity because the infill density is low enough to allow copper penetration into the material to create a strong mechanical interlocking with ABS, yet high enough to create multiple conductive bridges through the thickness of the sample. This study demonstrates the effectiveness of electroplating as a post‐processing technique to simultaneously enhance the mechanical and thermal properties of FFF‐printed parts and provides insights into the optimal design parameters for achieving this goal.

Introduction: This study presents a new design of multilayered PMMA dental composite material combining electrospun continuous composite polyvinylpyrrolidone (PVP) nanofibers filled with zirconia (ZrO2) nanoparticles and two-component self-cure PMMA dental resin. The aim is to improve the mechanical properties of dental PMMA material via the large surface area of electrospun nanofibers, the toughening effect of PVP and ZrO2 nanofillers. Methods: First, PVP/ZrO2 composite nanofibers with different ZrO2 contents of 5%, 10% and 20% (wt. % of PVP) were prepared by electrospinning. Then, multilayered samples containing alternating PMMA resin and electrospun composite nanofiber mats with different ZrO2 contents were manufactured by lay-up process. Samples containing single and double layers of nanofiber mats were prepared and cured in a water bath dental acrylic curing device in order to prepare composites without any void. Results: FTIR and SEM results reveal that PVP enables good interfacial interactions and compatibility between the nanofibers and PMMA matrix. The mechanical properties are improved as an increase of the flexural strength up to 83% and 67% is observed for PMMA/PVP/ZrO2-10s and PMMA/PVP/ZrO2-20d samples, respectively. The presence of PVP nanofiber layers significantly improves the flexural toughness, especially for samples reinforced with a single layer of nanofibers where improvements up to 169% and 153% are observed for PMMA/PVP/ZrO2-5s and PMMA/PVP/ZrO2-10s composite samples respectively. The micro-hardness is also higher for composite samples compared to neat PMMA dental material. Conclusion: The overall results clearly depict a noticeable enhancement of the mechanical properties, especially the flexural toughness of PMMA dental material

The properties of single shear specimens connected by wooden nail frictional welding and twist nails were studied. The single shear properties of the specimens connected by wooden nail welding were lower than that of the twist nail specimens. The single shear capacity of the wooden nail welding specimen was determined by calculating the method of design value of the bearing capacity of the pin connection. Furthermore, the flexural properties of the wooden nail welding laminated timber were analyzed. Due to the larger diameter of the wooden nails compared with the twist nails, the wooden nail welding laminated timber in the elastic phase had higher stiffness. The elastic modulus of the wooden nail welding laminated timber exceeded the average elastic modulus of the constituent lumber pieces by 9.46%. The number of wood lumbers in wooden nail welding laminated timber had little effect on the elastic modulus of laminated timber, but the nail spacing had a certain effect. Therefore, in future research, it is recommended to use the construction method of twist nail connection to design the wooden nail welding laminated timber. In addition, the nail spacing should refer to the GB 50005 (2003) standard and the wood structure design manual.

Bamboo fiber-reinforced polymers have been widely studied as natural fiber composites. This study fabricated a continuous bamboo-textile-reinforced polymer (BTRP) composite by using woven bamboo strips and epoxy through vacuum-assisted resin transfer molding (VA-RTM). The physical properties, including bulk density and equilibrium moisture content, of various BTRP specimens with different textile architectures, stacking sequences, loading axes, and numbers of layers were preliminarily evaluated. The specimens’ flexural properties, including strength, modulus, integral load – deflection relationship, damage parameters, and fractography characteristics, were also examined. As the number of layers increased, the flexural strength decreased but modulus values increased. When the number of layers was constant, the plain-woven BTRP specimens had slightly higher strength and modulus values than did the twill-woven specimens. The BTRP specimens exhibited remarkable mechanical properties and staged failure behaviors unique to laminated materials. Moreover, the stiffness of the specimens was attenuated before reaching the ultimate load, which was attributed to microscopic interphase damage, and the various architectures affected the specimens’ fracture modes. The gradual multistage failure modes of the specimens imply that the fabricated composite is relatively safe for use. According to these results, the fabricated composite incorporates the advantages of VA-RTM and continuous nontwisted bamboo strips, indicating that it has substantial commercial potential.

One of the most common load modes is flexure. The paper measures and models the flexural strength and modulus of a bio-polyethylene reinforced with thermos-mechanical fibers from corn stover. Moreover, the authors use modified rules of mixtures to evaluate the contribution of the reinforcements to the properties of the composite. It was found a high impact of coupling agent content on the strength of the composites, and materials with a 6% of such agent and 50% of reinforcement increased 181% the strength of the matrix, and 464% its modulus. The obtained values are noticeable higher than polypropylene and some of its composites. Micromechanics analysis shows that the effect of natural fiber reinforcement on the flexural properties of a bio-based PE is similar to the effects on a polyolefin. Thus, the use of fully bio-based composites can be proposed as a substitute for some oil-based polymers, partially bio-based materials, and their composites.

The properties of single shear specimens connected by wooden nail frictional welding and twist nails were studied. The single shear properties of the specimens connected by wooden nail welding were lower than that of the twist nail specimens. The single shear capacity of the wooden nail welding specimen was determined by calculating the method of design value of the bearing capacity of the pin connection. Furthermore, the flexural properties of the wooden nail welding laminated timber were analyzed. Due to the larger diameter of the wooden nails compared with the twist nails, the wooden nail welding laminated timber in the elastic phase had higher stiffness. The elastic modulus of the wooden nail welding laminated timber exceeded the average elastic modulus of the constituent lumber pieces by 9.46%. The number of wood lumbers in wooden nail welding laminated timber had little effect on the elastic modulus of laminated timber, but the nail spacing had a certain effect. Therefore, in future research, it is recommended to use the construction method of twist nail connection to design the wooden nail welding laminated timber. In addition, the nail spacing should refer to the GB 50005 (2003) standard and the wood structure design manual.

The variability in natural fiber composite properties has always been problematic due to the dispersion in their mechanical properties resulting from fiber misalignment, irregular crosssection, fiber length, and geometry, which impacts their reliability. This issue of reliability has greatly affected the selection process of natural fiber composites as opposed to the synthetic fiber counterparts when it comes to strength, stiffness, failure strains, and energy absorption criteria. Stiffness is one property which greatly depends on the span length and load-bearing capacity of the material, which makes it an important criterion during product design. In this study, flexural properties of the jute fabric composite were studied through experiment and uncertainty analysis using various distribution functions. Jute epoxy composite at 38% fiber volume fraction was fabricated, and samples were machined using abrasive water jet machining as per ASTM D7264 standard for bend test. The samples were experimentally tested for bending strength, modulus, and failure strains, and uncertainty analysis was done to further analyze their failure behavior. Experimentally tested samples showed multimode bending failure such as M(CAT) and M(TAB) as per ASTM D7264.

The aim of this study is to investigate the effect of fiber loading on mechanical and water absorption characteristics of composites made from sisal fiber and polypropylene matrix targeted for use in bathroom wall tile applications. The amount of fiber content in the composites was varied from 10%, 20%, 30%, and 40% to 50% by weight. The composites were manufactured by melt-mixing method. The effects of fiber loading on various composite characteristics were investigated using tensile strength, tensile modulus, flexural strength, flexural modulus, impact strength, compressive strength, and water absorption. With the increase of fiber content, properties, such as tensile strength, tensile modulus, flexural strength, flexural modulus, impact strength, and compressive strength increases up to optimum level, whilst decrement in these properties were observed after the optimal level. The maximum tensile strength of 52.69 MPa, tensile modulus of 1.1 GPa, flexural strength of 127.8 MPa, flexural modulus of 6.22 GPa, impact strength of 10.195 KJ/m2 and compressive strength 137.7 MPa were obtained. Water absorption rate increased with increase in the fiber weight proportion due to the hydrophilic character of the sisal fiber. From the result of this study, it can be concluded that the optimal mechanical and water absorption properties were achieved at 30% fiber content.

The effects of fiber structure and curing period on the flexural properties of basalt fibers reinforced fine-grained concrete were investigated in this paper. The damage and fracture processes of composites were monitored using acoustic emission technology. The flexural behavior of composites in terms of load-displacement curves, ultimate flexural load, and toughness was studied. The damage and fracture patterns of composites were described using acoustic emission parameters such as ringing count, amplitude, and accumulative energy. In the middle and late periods, basalt textiles outperformed basalt fibers in terms of improving the flexural load of fine-grained concrete. The flexural load improved at first and then decreased as the amount of basalt fibers increased, while the flexural load continued to improve as the amount of basalt textiles increased. Compared with basalt fibers reinforced fine-grained concrete, the flexural load of basalt textiles reinforced fine-grained concrete with 28 days curing period increased by 13.40%, −2.13%, and 75.96%, respectively. In terms of acoustic emission, the basalt textiles reinforced fine-grained concrete released more energy, the intensity and frequency of the acoustic emission signal were higher, and the cumulative ringing count was also greater. The basalt textiles reinforced fine-grained concrete exhibited greater flexural deflection and ductility.

The present study is a continuation of a previously published by the authors. In Part I, mechanical data of Alkaline-treated natural fibers-reinforced plaster was examined using response surface methodology (RSM) statistics, while in this work (Part II), the data are analyzed using Artificial neural network (ANN) statistics. Many studies have focused on substituting synthetic fibers by natural fibers in plaster matrix. The present study reports ANN statistics data analysis on the mechanical properties of plaster and natural fibers. ANN and RSM methods are employed and their findings discussed. During this study, flexural properties of sodium hydroxide solution (NaOH)-treated natural fibers in plaster mortars were investigated. Experimental data effects were established by analysis of variance (ANOVA) method. Fiber length optimization and NaOH percentage treatment of fibers were also performed utilizing desirability function DF to obtain maximum flexural properties. Experimental results showed good agreement with those obtained statistically. The ANN and RSM models also have correlated highly to the experimental data. However, the ANN model proves more to be accurate.

This study presents a detailed investigation on the three-point and four-point bending behaviour of asymmetric sandwich beams composed of polyvinyl chloride (PVC) foam core and E-glass fibre reinforced polymer face sheets. The effects of mid-plane asymmetry on the bending load-displacement behaviour and failure mechanism of the sandwich beams were examined. Simple analytical expressions accounting for flexural and shear rigidities of the sandwich beams were proposed to predict the failure load, mid-span deflection and equivalent bending stiffness of the specimens and validated against experimental results. By shifting the loading direction, the flexural behaviour of asymmetric beams may be controlled. On the loading side, the use of face sheet with thick or high in-plane mechanical characteristics resulted in a delay in compressive failure of the top face sheet. The effective bending stiffness was overestimated since the applied formula did not account for shear deformations. First-order shear deformation theory was used to estimate the mid-span displacement values of sandwich beams in elastic regime and showed good agreement with the experimental results.

Introduction: Bulk Fill (BF) resins and Ormocers are recently introduced composite restorative materials in order to overcome the disadvantage of polymerisation shrinkage exhibited by most of the conventional resin-based composites. Aim: To evaluate the physical and mechanical properties of Organically Modified Ceramics (Ormocers) in comparison with BF composite resin restorative material. Materials and Methods: In this in-vitro study, 20 human extracted premolars were allocated into two groups of 10 each. ORM (Group-1 Admira fusion, n=10) and BF (Group-2 Filtek BF, n=10) composite materials were used to prepare and restore Class-V cavities. The teeth were subjected to thermocycling and immersed in 1% methylene blue dye solution. Along the lateral walls of each sectioned specimen, depth of dye penetration was measured under the stereo microscope. A total of 20 rectangular (25x2x2 mm) and 20 disc (10x2 mm) shaped specimens of the above-mentioned materials were fabricated. Specimens of Flexural Strength (FS) were tested with the universal testing machine and Vickers hardness tester used for Surface Hardness (SH) evaluation. The data was statistically analysed using an unpaired t-test. Results: Total of 20 extracted premolars were analysed. On inter-group comparison, it was observed that mean dye penetration was lowest for Group-1 (0.6±0.69) compared to Group-2 (2±0.81) and the difference observed was statistically significant (p=0.001). BF exhibited a lower FS of 211.69±43.9 compared to Ormocer 326.19±90.3, the difference is statistically significant (p=0.001). However, BF exhibited a higher SH of 38.3±0.15 compared to Ormocer 33.70±0.86, and the difference is statistically significant (p-value

Parts made with Fused Deposition Modeling (FDM) are anisotropic, meaning that their proper- ties are dependent on their orientation and the direction of forces. This study aimed to investigate how the infill orientation in FDM parts influences their flexural properties. Samples were created with either a 0° or 45° infill orientation and evaluated using a 3-Point Bending test. Samples with a 0° infill orientation had a brittle failure mode, lower coefficient of variation, higher yield strength, and higher flexural modulus, while samples with a 45° infill orientation had a ductile failure mode and a higher maximum force value. Samples with a 45° infill orientation had a higher flexural strain at failure, but samples of both infill orientations had similar flexural strength. This suggests that while both orientations result in similar flexural strengths, the 0° infill orientation is largely superior to the 45° infill orientation in terms of flexural properties.

Porous yttriastabilized zirconia (YSZ), in a composite with NiO, is widely used as a cermet electrode in solid oxide fuel cells (SOFCs) and solid oxide electrolysis cells (SOECs). Given cycles of high temperature in these energy devices, mechanical integrity of the porous YSZ is critical. Pore morphology, as well as properties of the ceramic, ultimately affect the mechanical properties of the cermet electrode. Here, we fabricated porous YSZ sheets via freezing of an aqueous slurry on a cold thermoelectric plate and quantified their flexural properties, both for as-fabricated samples and samples subjected to thermal shock at 200 °C to 500 °C. Results of this work have implications for the hydrogen economy and global decarbonization efforts, in particular for the manufacturing of SOFCs and SOECs.

Silicon carbide fibers have superior flexural properties and chemical stability compared to glass fibers. We investigated the flexural strength and modulus of an experimental, short silicon carbide fiber-reinforced resin. Short silicon carbide fibers with lengths of ~0.5, 1, 2, and 3 mm were prepared and silanized. Urethane dimethacrylate and triethylene glycol dimethacrylate were mixed at a 70:30 wt% ratio and used as the matrix resins. Each length of short silicon carbide fibers and the matrix resin were combined using a mixing machine and then used for specimen preparation. The three-point bending test conditions were in accordance with ISO 4049:2009. The fracture surfaces of the specimens after the three-point bending test were observed using secondary electron images. The data were statistically analyzed with a one-way analysis of variance and Tukey’s HSD test (α = 0.05). The flexural strength and modulus of the specimens containing 2 mm or 3 mm silicon carbide fibers were significantly higher than the other specimens. The river pattern was observed more clearly in specimens containing shorter silicon carbide fibers, although this pattern was observed in all specimens.

Abstract Employment of natural fiber for the filament of fused deposition modeling (FDM) can be found in numerous studies from different areas. However, the presence of fiber such as kenaf in polymer filament could cause mechanical properties degradation with regard to the fiber loading owing to low compatibility between natural fiber and polymer matrix. Therefore, this study aims to study the mechanical properties of three-dimensional (3D)-printed structures of composites specimens with varying volume percentages of kenaf fiber. From the tensile and flexural testings, the findings revealed decrements in the tensile strength and modulus of kenaf fiber-reinforced ABS (KRABS) composites from 0 to 5% contents of kenaf fiber which were 23.20 to 11.48 MPa and 328.17 to 184.48 MPa, respectively. The raising amount of kenaf fiber at 5 to 10% raised the tensile strength and modulus from 11.48 to 18.59 MPa and 184.48 to 275.58 MPa, respectively. Flexural strength and modulus of KRABS composites were decreased at to 5% from 40.56 to 26.48 MPa and 113.05 to 60 MPa, respectively. With further kenaf fiber addition from 5 to 10%, the flexural strength and modulus were increased from 26.48 to 32.64 MPa and 60 to 88.46 MPa, respectively. These results were supported by the finding from the morphological analysis, where the presence of porosity and fiber pull out implied the poor interfacial bonding between kenaf fiber and ABS matrix. This study has successfully demonstrated the tensile and flexural performances of different volume percentages of KRABS composites filament for FDM through experimental research.

Developing high-performance composite materials from biobased resources is paving the path toward sustainability. This paper reports cellulose long filaments (CLFs)-reinforced Vanillin Epoxy (VE) green composite developed through vacuum-assisted resin transfer and compression molding techniques. The proposed green composite combines the strong and tough cellulose long filaments with the thermally stable and hydrophobic biobased VE resin. The reinforcement with CLFs improved the flexural strength and flexural modulus of neat biobased VE resin remarkably by 135.1% and 542.8%. The green composite possessed a Tg of 144 °C and a water contact angle (WCA) of 96.4o, demonstrating good thermal stability and hydrophobic properties. SEM and FTIR results showed a strong interaction between CLFs and biobased VE epoxy resin. The above characteristics make the proposed green composite a robust material for environmentally friendly and high-performance structural applications.

The nozzle of a 3D printer extrudes molten filament onto the print surface. The detachable and adjustable nozzle of a 3D printer allows for the printing of lines of varying thickness. This study intends to investigate the effect of nozzle diameter on the tensile and flexural properties of printed specimens. The tensile and flexural specimens were prepared according to ASTM D638 Type 1 and ISO 178, respectively. After specimens were printed with nozzles having diameters of 0.3, 0.4, 0.5, 0.6, and 0.8 mm, tensile and flexural tests were conducted using an Instron 5585 machine. Each specimen was printed with 0.2 mm layer thickness, a line pattern, and 100 percent infill. Tensile and flexural behaviors of PLA specimens were comparable, according to the findings. Tensile and flexural strengths increase as nozzle diameter increases, but they are only effective up to a certain diameter. At a nozzle diameter of 0.6 mm, the maximum tensile strength was 33.32 MPa, and at a nozzle diameter of 0.5 mm, the maximum flexural strength was 76.76 MPa. The flexural strength decreases when using nozzles with diameters of 0.6 and 0.8 mm, and the tensile strength decreases when using a nozzle with a larger diameter (0.8 mm). Because the diameter of the nozzle has a significant impact on the mechanical properties of a part, it is crucial to choose the correct nozzle diameter for optimal mechanical properties.

In recent years, serious reduction in petroleum resources and concerns about the usage of synthetic plastics have prompted global communities to accept the use of natural fibres and biopolymers in many products. Lignocellulosic fibre polymer biocomposites have attracted the attention of scientists and engineers because of their wide availability, low carbon emission and biodegradability. Currently, oil palm is one of the main crops cultivated in Malaysia and Indonesia and is regarded as a potential source of lignocellulosic fibres for biocomposites. The cellulosic content of oil palm fibres (OPFs) enhances the mechanical properties of composites. Ensuring the compatibility of OPFs as main constituents with other materials in composites for a specific applications is essential. Mechanical performance in terms of tensile, flexural and impact strength determines an OPF's compatibility. However, no comprehensive reviews focusing on the mechanical properties of OPF biocomposites have been published, and factors influencing mechanical performance, such as interfacial adhesion, stacking sequence, additive, type of polymer and fibre size have not been explored. Some studies have identified the research gaps and deduced that the potential applications of OPFs as reinforcement materials in composites have not been explored.

Epoxy composites were prepared by doping nano Zirconia Toughened Alumina (ZTA) which were synthesized by solution combustion method into epoxy resin and hardener. Initially ZTA nanopowder was characterized to check its purity, morphology and to confirm its metal-oxide bonding using XRD, SEM and FTIR respectively. The thermal properties such as TGA and DTG were also analysed. The polymer composites were obtained by uniformly dispersing ZTA nanopowder into epoxy using an ultrasonicator. Polymer composites of various concentrations viz, 0.5, 1, 1.5, 2 and 2.5 wt% were synthesized, all concentrations were prepared on weight basis. All the polymer composites were tested for compression properties, flexural properties and tensile properties. Best results for all the mechanical properties were obtained for epoxy with 1.5 wt% ZTA composites. Electrical properties such as breakdown voltage and breakdown strength were analysed and outstanding results were observed for epoxy with 2.5 wt% ZTA composite.

This article presents the effects of thermal annealing at elevated temperatures (> glass transition temperature Tg) on the performance of polymer parts via material extrusion 3D printing. Both semi-crystalline and amorphous filaments were used. As-printed parts were designed to be amorphous and then annealed at 60, 110 and 150 °C for different durations ranging from 50 to 6400 s. The flexural strength and Young’s modulus increased by a maximum of approximately 10%. The increase was ascribed to crystallisation development during annealing, as confirmed by thermal and morphology characterisations. Hence, this effect was only observed with semi-crystalline materials. On the other hand, all the annealed parts expanded in the thickness direction and shrank in the perpendicular plane. The maximum linear strain reached 20%, while the volume strain was negligible. These morphology changes after annealing reversed the strain-hardening of the strand and led to inferior strand performance against local tensile deformation. The degradation can outweigh the benefits of crystallinity development. For amorphous parts, the degradation reached approximately 25% in both the flexural strength and the modulus.

In the last decades, eco-friendly materials are playing an interesting role. Particularly, many studies deal with the use of natural fibers as a replacement to synthetic fibers in the plaster matrix. This study has examined the flexural properties of treated natural sisal, flax and jute fibers with different concentrations of NaOH (1.5%, 2% and 4%) and fiber length (5, 10 and 20 mm) reinforced plaster mortars. In this study, the effect of experimental parameters was determined by using analysis of variance ANOVA test. In addition, the response surface methodology (RSM) and desirability function (DF) are also used to optimize the output responses with maximizing the flexural properties. Finally, the experimental results are in good agreement with those obtained statistically.

The formulation and flexural properties of thin fly ash geopolymers with thickness of merely 10 mm and replacement of ladle furnace slag to fly ash in thin geopolymer were presented. The formulation was discussed in terms of NaOH molarity, solid aluminosilicates-to-liquid alkali activator (S/L) mass ratio, and alkali activator (Na2SiO3/NaOH) mass ratio. Thin fly ash geopolymers with flexural strength and Young's modulus of 6.2 MPa and 0.14 GPa, respectively, were obtained by using 12 M NaOH, S/L ratio of 2.5 and Na2SiO3/NaOH ratio of 4.0. A high Na2SiO3/NaOH ratio was implemented for thin geopolymer synthesis to produce a more viscous slurry which helped to retain the shape of a thin geopolymer. The incorporation of ladle furnace slag up to 40 wt.% reported an increment of 26% in flexural strength up to 7.8 MPa as compared to pure fly ash geopolymers and the stiffness was increased to 0.19 GPa. Denser microstructure with improved compactness was observed as the ladle furnace slag acted as the filler. New crystalline phases of calcium silicate hydrate (C–S–H) were formed and coexisted with the geopolymer matrix, which consequently enhanced the flexural strength of thin fly ash geopolymer. This proved that the ladle furnace slag has the potential to be utilised in geopolymer synthesis and will enhance the flexural properties of thin geopolymers. The flexural performance of thin geopolymers in this study was considerably good as the thin geopolymers exhibited comparatively similar flexural strengths, but a higher strength/thickness ratio as compared to geopolymers with thickness greater than 40 mm.

Mechanical properties of composite board made from waste paper, wood dust, and sisal fibers with various weight proportions were investigated in this work. The composite board was produced by hand lay-up technique with polyvinyl alcohol (PVA) binder. The result shows that the bending strength ranged between 3.5 N/mm2 and 7.5 N/mm2; water absorption values between 6.65% and 10.5%; as well as density between 280 kg/mm3 and 360 kg/mm3. A better combination of results has been found for sisal fiber (35%), wood dust (30%), PVA (10%) and waste paper (25%). The obtained result is compared with those of the conventional ceiling board results and it is observed that these composite materials can be used for internal low-cost construction work for separation, and acoustic & thermal insulation purposes.

The combination of experimental programs and finite element numerical methods is adopted to explore the durability of WBC (waste brick concrete). Rapid freeze-thaw and flexural tests are performed with the content of WBCA (waste brick coarse aggregate) and the number of freeze-thaw cycles as variables. Freeze-thaw damage mechanisms at the microscopic interfaces of recycled concrete are revealed by scanning electron microscopy. The evolution laws of relative dynamic elastic modulus, mass loss rate, and flexural and tensile strength loss rate are analyzed. Combined with numerical simulations, the temperature stress distribution and three-point bending damage law of concrete with 100 % WBCA content at different freeze-thaw times are shown, and practical examples are verified. Results showed that WBC with high WBCA content has poor freeze-thaw resistance. Furthermore, WBC's freezing resistance and bending properties deteriorate as the number of freeze-thaw cycles increases. Possible damaged locations in the concrete are determined by stress analysis. The finite element model can predict the flexural performance of WBC better with an error of 4.5 % for the peak load and 3.5 % for the peak displacement of the beam. Therefore, the presented model can also be used to predict the performance of concrete after freezing and thawing under any WBCA replacement rate.

The natural fine aggregate was totally replaced by recycled fine aggregate (RFA) containing crush dust to prepare recycled high ductility cementitious composites (R-HDCC) for making full use of waste concrete and obtaining better properties. A total of 45 slab specimens in 15 groups were manufactured to systematically investigate the effects of RFA particle size distribution, RFA-binder ratio (R/B), water-binder ratio (W/B), fiber volume fraction (Vf), fly ash content (FA/B) and fiber length (Lf) on the flexural properties of R-HDCC through the third-point test. The results showed that the specimens with the RFA containing crush dust and smaller particles performed best due to the denser matrix. The specimens with a moderate R/B of 0.4 had the highest peak flexural stress whereas the specimens with a smaller R/B of 0.2 had a higher ductility and energy absorption ability. The peak flexural stress and ductility decreased with the increase in W/B, but the fiber strengthen effect was greatest for specimen with a moderate W/B of 0.35. The peak flexural stress of specimen increased continuously as Vf increased from 0 to 2.0% whereas the ductility and energy absorption ability reached maximum when Vf increased to 1.5%. Small amount of fly ash could slightly improve the peak flexural stress of specimen while the achievement of higher ductility and energy absorption ability needed a higher FA/B. Finally, the prediction models of peak flexural stress and ductility ratio of R-HDCC were proposed, which showed good agreements with test results.

Al-Zn-Mg-Cu alloy, recognized for its heat-treatable and super-high strength, is a pivotal material for critical structural components in aviation. Consequently, grasping the intricate relationship between heat treatment processes and the microstructural characteristics and properties of the Al-Zn-Mg-Cu alloy is of paramount practical significance. This study encompasses a spectrum of heat treatment methodologies, delving into the diverse effects of distinct aging treatments on the microstructure and performance of thin Al-Zn-Mg-Cu alloy sheets. The findings illuminate that short natural aging treatments bestow heightened strength and hardness upon the alloy, albeit at the expense of ductility. Nevertheless, the alloy retains commendable malleability, enabling significant cold deformation. In contrast, artificial aging markedly elevates the alloy’s strength and hardness, albeit concurrently inducing a precipitous decline in ductility, thereby attenuating the alloy’s cold formability.

In this paper, a functionally graded polymer nanocomposite (FGPNC) was arranged via mixing the Alumina (Al2O3) nanoparticles (50 – 100 nm) with an epoxy matrix through five layers of 1.2 mm thickness for each layer using hand lay–up technique. Different volume fractions were taken (0, 1, 2, 3 and 4) % of the used nanoparticles and were cast in molds made from acrylic for creating the graded composite sheet in the thickness direction. The prepared isotropic specimen was tested by tensile and compressive test. The results showed that the (4% Vf of Al2O3) has the best enhancement of the ultimate tensile strength (85.25% from neat epoxy) and decreased thereafter. Flexural properties of three different types of functionally graded materials (FGMs), including FGM1, FGM2 and FGM3, isotropic nanocomposite (2% Al2O3) and pristine epoxy were obtained. Flexural strength and flexural modulus of the functionally graded polymer nanocomposite for each type of FGMs enhanced by (51.7%) and (67%), respectively for the FGM1 loaded from the neat epoxy side, whereas for the FGM1 loaded from the (4%) side, the improvement in these properties was (17.8%) and (29.4%), correspondingly over those for the neat epoxy. For FGM2, the improvement in the flexural strength was (27%) and (71.8%) for the flexural modulus as compared with pristine epoxy. The enhancement in the flexural strength of FGM3 was (27%) and flexural modulus (57.7%). Design Modeler (ANSYS Workbench) was used to verify the experimental flexural test results. A very good agreement was found between the experimental and numerical results with a maximum error of (3.92%) in the flexural modulus for FGM1 loaded from the composite side.