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Heat treatment is one of the environmentally friendly methods applied to improve the structural properties of wooden materials. While heat treatment improves some properties of wood material, it also negatively affects its mechanical properties depending on the heat treatment conditions applied. The decrease in mechanical properties due to heat treatment limits the use of wood material in various applications requiring mechanical strength. For this purpose, various fiber-reinforced polymers have been used in recent years. In this study, it was aimed to experimentally and numerically examine the flexural properties of unheat-treated and heat-treated black pine (Pinus nigra Arnold.) wood reinforced 1, 2 and 3 times with carbon, glass and aramid. Following the experimental flexural tests, the samples were modeled and analyzed in the finite element software program. The average flexural strength of the heat-treated sample is 11.72% lower, and the elasticity modulus is 1.23% lower than the unheat-treated sample.It has been determined that carbon-based polymer fabrics, among fiber-reinforced polymer fabrics, have the best reinforcement effect. The flexural strength of the UHT-C-3 sample is 6.1% and the elasticity modulus is 3.52% higher than the UHT-C-1 coded sample. Compared to the sample without reinforcement, flexural strength increased by 30% and elasticity modulus increased by 7%. It is seen that as the number of fiber reinforced polymer layers increases, the flexural properties also increase. When the experimental and numerical analysis results were examined, the flexural strength and modulus of elasticity values gave similar results at the R2: 0.88–0.99 level. In addition to technologies using kinds of reinforcement evaluated in conservation applications, it may be utilized for numerical analysis in the field of repairing or reinforcing different grades, patterns, and types of reinforcement in already-existing wooden structures. [ABSTRACT FROM AUTHOR]

Highlights The mechanical properties of carbon‐fiber‐reinforced polymer composites are highly sensitive to temperature and preloading conditions. The behavior of carbon‐fiber/poly(etherketoneketone) (CF/PEKK) under various temperatures and prebending (PB) conditions is not fully understood. This study examines CF/PEKK's interlaminar shear strength, tensile, Mode II, and bending properties at room temperature (RT, 25°C), low temperature (LT, −60°C), and extreme cryogenic temperature (ECT, −196°C). The combined effects of temperature and PB at 30%, 50%, and 70% of ultimate displacement for 24 and 72 h were analyzed. Results indicate that decreasing temperature increases shear strength, improves tensile properties, and reduces fracture toughness. Bending tests show that strain, yield strength, and yield strain rise significantly from RT to ECT, while the modulus remains similar, but the postyield modulus decreases. Higher PB intensity reduces strength, moduli, and strain. Under combined PB and LTs, CF/PEKK shows a coupled mechanism with PB‐induced microcracks mitigated by low‐temperature failure mechanism. Strength increased by ~20% from RT to ECT, and 30%‐prebent samples retained over 80% residual flexural strength even at LT and ECT. These findings highlight CF/PEKK's excellent bending resistance at extreme temperatures, emphasizing its potential for aerospace applications. Temperature significantly impacts CF/PEKK composites' mechanical properties. Decreasing temperature increases shear strength and tensile properties. PB‐induced microcracks and low temperatures influence flexural properties. CF/PEKK composites show excellent bending resistance in extreme conditions. High residual strength persists at low temperatures and after prebending. [ABSTRACT FROM AUTHOR]

Highlights With the rapid development of electric vehicles, a hybrid composite structure has been designed for the battery pack bottom guard to enhance impact resistance and reduce weight. The glass fiber‐reinforced polypropylene (GFPP)/DP980 honeycomb sandwich structure consists of GFPP panels with a polypropylene honeycomb core. DP980 advanced high‐strength steel plate is encapsulated within the structure, inspired by fiber metal laminates. A lightweight and high‐strength sandwich composite lay‐up solution was determined through equivalent bending stiffness theory, finite element simulation and experiment. An asymmetric sandwich structure with the steel plate on the impacted side enhanced flexural strength and ductility, demonstrating different failure sequences and a higher bending strength of 77.64 MPa compared to 50.18 MPa when the steel plate was on the unimpacted side. As impact energy increased from 100 to 200 J, the sandwich structure showed higher peak impact load, deeper craters, and increased bulge height, with significant delamination up to 175 J, while gravel impact tests revealed minimal flexural strength reduction (4.92%) even after repeated impacts. This study confirms that the use of thermoplastic sandwich structures is a viable and promising option for crash safety and the lightweight design of battery pack bottom guards. The thermoplastic honeycomb sandwich structure is polypropylene‐based. The use of advanced high strength steel is inspired by fiber metal laminates. Both thickness and surface density are considered in the structural design. The steel plate placed on the impacted side improves the flexural behavior. The sandwich structure has excellent impact resistance and lightweight level. [ABSTRACT FROM AUTHOR]

Highlights In this paper, a mortise‐and‐tenon structural design was introduced into composite maintenance to create a new type of joint between the repair patches and the parent structure, where both the patches and the structure were carbon fiber composites. Effects of different joints, including step‐lap and mortise‐and‐tenon‐lap joints, on the bending failure of the repaired composites were simulated and then verified through experiments. Results showed that compared with the traditional step‐lap method, the mortise‐and‐tenon connection changed the direction of damage extension from a simple single path to complex multiple paths, which effectively inhibited the damage expansion and enhanced the structural damage tolerance. Therefore, the flexural strength of the repair with the new joint was improved by 19.9%. However, the mortise‐and‐tenon‐lap joint resulted in a poor moisture‐heat resistance of the repaired structure. Interestingly, although the flexural strength of the mortise‐and‐tenon repair decreased by 10.45% after the hygrothermal treatment, it was still higher than that of the step‐lap repair without hygrothermal treatment. A novel joint, mortise‐and‐tenon, was introduced into composite maintenance. Damage extended along multiple paths in the new joint and was inhibited. Flexural strength of the repair was higher than that of traditional step‐lap repair. [ABSTRACT FROM AUTHOR]

Highlights An improved approach consisting of a combination of fiber placement and fused filament fabrication is introduced for the additive manufacture (AM) of structural grade sandwich beams. Here, sandwich beams are additively manufactured using in‐situ deposition and consolidation of continuous fiber unidirectional facings made from a commingled yarn system of e‐glass fiber (~50% vol.) and amorphous PET, and a hexagonal honeycomb core structure made from PETG. Both facings and the sandwich core are manufactured on a single machine, in one sequence (skin‐core‐skin), employing the benefit of matrix compatibility to create autohesion at the interfaces. Flexural and transverse shear rigidity are determined experimentally and compared with analytical predictions and show correlation to within 3%. Flexural strength and core shear strength are also measured. Post‐mortem examinations show that core fracture and core facing debond were the dominant failure mode in flexure. Single cantilever beam tests were performed to evaluate core facing debond toughness. Subsequently, surface preheat using infrared heaters was utilized to increase autohesion between core and facing. The results show debond toughness was increased 4 times using infrared heating. This research effort presents a manufacturing approach that has the potential for the AM of stiff, well bonded, structural grade sandwich beams, in an integrated sequence, employing in‐situ consolidation to the facings, without the need for the use of intermediate adhesives for skin‐to‐core bonding. An improved additive manufacturing technique for making sandwich panels is developed. Sandwich panel facings have fiber volume fractions of approximately 50%. Surface preheat improves core‐to‐facing debond toughness by a factor of 4. Top and bottom facings are consolidated during manufacture leading to better properties. Experimental results are compared to analytical predictions and show good correlation. [ABSTRACT FROM AUTHOR]

The Fused Filament Fabrication is an economic 3D printing process to produce lightweight polymersbased 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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Highlights The aim of this work to fabricate bamboo (B)/oil palm (O) fibers based biocomposites to assess mechanical, thermal and morphological properties. Flexural strength and modulus of hybrid biocomposite (7B:3O) exhibited a higher value (71.18 MPa and 5.24GPa) respectively among all biocomposite samples. On the other hand, pure biocomposite (B) showed a higher impact strength value (6977.8 J/m2) compared to other biocomposites. The results of TGA showed that thermal stability was observed significantly for hybrid biocomposites compared to other samples. In addition, the maximum decomposition temperature values were displayed in the hybrid biocomposite (5B5O), which was 377.82°C. Through DMA, it was likely to find the storage modulus curves (E′), loss modulus (E″) and damping factor (tan δ) for the biocomposites. The E′ showed an increase in the (3736.84 MPa) contrasted to other corresponding samples which were 3121.81 MPa, and 3209.67 MPa for 3B7O MPa and 5B5O samples, respectively. Overall, the results of DMA displayed an enhancement in the storage modulus (E′) in terms of the hybrid biocomposites representing greater stiffness and lower damping factor. SEM micrographs were utilized to understand the fiber bonding and fiber adhesion with the epoxy matrix. Furthermore, it confirmed SEM results that hybrid natural fibers enhance the complete characterisations of bio‐epoxy materials. Additionally, SEM images of the tensile fracture surfaces discovered voids and cracks. Finally, it can be concluded that the selection for the developed hybrid biocomposites provides excellent and economical lightweight biomaterials for automotive, aerospace, contractions and building components. Green hybrid biocomposites by oil palm/bamboo fiber/bioepoxy resin. Mechanical, thermal, DMA of hybrid composites carried out. Hybrid biocomposite(7B:3O) exhibited higher flexural strength value (71.18 MPa). TGA showed that the biocomposites are thermally further stable. DMA displayed an enhancement in the storage modulus (E′). [ABSTRACT FROM AUTHOR]

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 FROM AUTHOR]

Three dimensional (3D) textiles are preferable reinforcing materials for composites with lightweight and higher mechanical properties. In this study, a 3D woven flax fiber reinforced PLA composite with better flexural and tensile properties was developed. Four hybrid yarns with varied PLA contents were prepared as warp, weft and z‐yarns to weave the 3D preform and then changed to composites through compression molding technology without additional fillers and matrixes. The composite's flexural and tensile properties were studied and an optimum value of 78.0 and 140.0 MPa respectively were found. Stress strain properties were also discussed which implies the flexural elongation is higher than those of tensile values. The microstructure was analyzed using optical microscope and SEM equipment's showed composites with higher PLA content were more brittle due to the PLA inimitable behavior. The thermal properties of the 3D composites made with different Flax/PLA combinations have closer and comparable values. One way ANOVA statistical analysis was done to show the significancy of PLA /Flax mass ratio, which has a significant effect on composite's properties. This study could bring a novel procedural approach for an advanced 3D woven composites for load bearing applications. Highlights: 3D woven flax /PLA composite was developed using Flax/PLA hybrid yarnsTensile and flexural properties were studiedFlexural strength increases with PLA, but, slightly lower in its strainPLA/Flax mass ratio has a significant effect on composite's propertiesThe mechanical strengths were improved compared to the related findings [ABSTRACT FROM AUTHOR]

Lime stabilization is a sustainable technique due to its use of local materials, increased durability, reduced maintenance, and improved resistance to water action. This paper examines the impact of lime stabilization on the mechanical, microscopic, and mineralogical properties of a tropical soil. Two types of lime, calcitic and dolomitic, were tested at 3% and 5% by weight. Compressive, indirect tensile and flexural test results and statistical analysis revealed that calcitic lime mixtures had higher strength and stiffness, whereas dolomitic lime mixtures exhibited greater deformability with higher tensile strain at break. Scanning electron microscopy indicated that the soil's porous matrix closed within 7 days for both lime types due to flocculation, with increased matrix interlocking over time. The calcitic lime mixture developed a more closed matrix compared to the dolomitic lime, which showed weaker cementing. X-ray diffraction analysis indicated higher consumption of clay minerals and a notable reduction in calcium hydroxide peaks in the lime-treated soils. The study concludes that calcitic lime provides better pavement performance for stabilizing the soil, enhancing its engineering properties while also being sustainable by reducing the need for raw material extraction and improving resilience to climate-related issues such as floods. [ABSTRACT FROM AUTHOR]

The solid-state processing and utilization of light-metal-based composites align with green policies by reducing the weight of components and employing lower processing temperatures compared to traditional metallurgical methods. This study explores the incorporation of SiC particles at concentrations of 5 and 10 wt.% into an Al4Cu matrix through powder mixing, compaction at 235 MPa, hot extrusion, and sintering at 600 °C in a nitrogen atmosphere. The resulting microstructure, hardness, compressive strength, and flexural strength of the composites were evaluated. During extrusion, the composite underwent plastic deformation, leading to cracking and fragmentation of the SiC particles within the matrix. Therefore, evenly distributed reinforcing particles with a diameter much smaller than the originally introduced ceramic particles were observed. Recrystallization also occurred, with Al2Cu precipitates forming on grain boundaries and nanosized Al2O3 oxides observed in porous areas and at matrix-reinforcement interphase boundaries. The composite containing 5 wt.% SiC exhibited the highest compressive strength of 305 MPa, while the composite with 10 wt.% SiC achieved the highest flexural strength of 889 MPa. However, non-deformable SiC particles crack before reaching maximum strength due to stress concentration at their sharp edges, initiating microcracks in the matrix. Microstructural analysis further revealed that SiC particles tend to crack during hot extrusion, reducing their effectiveness in stress transfer. The hardness remained constant at 78 HV1, irrespective of SiC content. These findings demonstrate that the addition of SiC particles significantly enhances the mechanical properties of Al4Cu composites, making them promising materials for lightweight and high-strength applications. [ABSTRACT FROM AUTHOR]

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.

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).

As a high-performance composite material in construction, textile-reinforced concrete has been of interest in recent years. This study significantly contributes to the characterization of textile-reinforced concrete through an extensive experimental and analytical investigation, focusing on impregnated textile-reinforced concrete under flexural loading. For this purpose, two sets of experiments were conducted. The first set involved model input parameters tests, including the tensile test of epoxy resin and E-glass yarn, as well as the compression and flexural tests of concrete. The second set is related to validation tests, specifically focused on the flexural behavior of textile-reinforced concrete. Micromechanical frameworks were employed to model the flexural behavior of textile-reinforced concrete and a multiscale micromechanical model based on the classical lamination theory was developed to predict the load-deflection diagram of textile-reinforced concrete in the three-point bending test setup. The modeling results demonstrated a remarkable agreement between predictions and experimental data. Key performance indicators, including the first crack force, ultimate force, flexural modulus, and maximum deflection, were accurately predicted with errors of 2.4%, 6.1%, 11.1%, and 6.3%, respectively. Furthermore, from a parametric study, it is perceived that the flexural modulus of elasticity in textile-reinforced concrete is predominantly influenced by concrete properties, while the ultimate strength of textile-reinforced concrete is significantly affected by the properties of the impregnated fabric. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the effect of incorporating nanocrystalline cellulose (NCC) sourced from rice husk on the mechanical properties of a commercial glass ionomer cement (GIC). NCC was isolated through acid hydrolysis, and its crystallinity, chemical structure, and morphology were characterized through x‐ray diffractometry, Fourier‐transform infrared spectroscopy, and transmission electron microscopy, respectively. Various concentrations of NCC (0%, 0.5%, 1%, and 1.5%) were added to reinforce the GIC matrix. Mechanical tests including compressive strength, flexural strength, hardness, and shear bond strength were conducted on the modified GIC samples. The addition of NCC resulted in increased hardness and shear bond strength values, with 1% NCC showing the highest values compared to other concentrations. However, there was no significant improvement observed in the compressive and flexural strength of the modified GIC. Failure mode test revealed a reduction in adhesive failure with the addition of NCC. Incorporating small amounts of NCC (0.5%–1%) suggests a promising and affordable modification of GIC restorative material using biomass residue, resulting in improved mechanical properties. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In an era of technological advancements, the quest for sustainable products has taken a center stage. The utilization of natural fiber reinforced polymer composites has become crucial in the manufacturing of eco‐friendly products due to their low cost, renewability, biodegradability, and comparable properties to synthetic composites. Coir‐based composites have been utilized in roofing, composite panels, furniture, and bio‐based insulation applications, providing enhanced strength and sustainability. In the current investigation, an exploratory data analysis (EDA) was conducted to understand the relationship between the various input variables and the flexural properties of short coir polymer composites (SCPCs). The data analysis revealed that manufacturing process had a significant impact on the flexural properties of SCPCs. Based on the insights gained from the EDA, an optimized Random Forest prediction model was developed to predict the flexural properties. Genetic algorithm approach for hyperparameter optimization led to lower objective loss in contrast to Bayesian optimized Random Forest model. The model's performance was subsequently evaluated through holdout validation, and the outcome demonstrated the model's proficiency in accurately predicting the properties. The developed model can be used as a tool for optimizing the design of SCPCs for specific applications, by predicting the flexural properties of the composites. Highlights: Flexural behavior of short coir polymer composites was analyzed and modeled.Manufacturing process has the highest impact on the flexural properties.Random forest model predicted the flexural properties with high accuracy.Genetic algorithm optimized model further enhanced the model performance.The developed framework provides insights into designing biocomposites. [ABSTRACT FROM AUTHOR]

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.

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.

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.

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.

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.

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.

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. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the micro-mechanical and macro-mechanical properties of self-cured and light-cured alkasite and to investigate how accelerated degradation in acidic, alkaline, and ethanol solutions affects the macro-mechanical properties of self-cured and light-cured alkasite. The specimens of the alkasite material (Cention Forte, Ivoclar Vivadent) were prepared according to the following three curing modes: (1) light-cured immediately, (2) light-cured after a 5-min delay, and (3) self-cured. Microhardness was tested before and after immersion in absolute ethanol to indirectly determine crosslink density, while flexural strength and flexural modulus were measured using a three-point bending test after accelerated aging in the following solutions: (1) lactic acid solution (pH = 4.0), (2) NaOH solution (pH = 13.0), (3) phosphate-buffered saline solution (pH = 7.4), and (4) 75% ethanol solution. The data were statistically analyzed using a two-way ANOVA and Tukey post hoc test. The results showed that the microhardness, flexural strength, and flexural modulus were significantly lower in self-cured specimens compared to light-cured specimens. A 5-min delay between the extrusion of the material from the capsule and light curing had no significant effect on any of the measured properties. A significant effect of the accelerated aging solutions on macro-mechanical properties was observed, with ethanol and alkaline solutions having a particularly detrimental effect. In conclusion, light curing was preferable to self-curing, as it resulted in significantly better micro- and macro-mechanical properties, while a 5-min delay between mixing the capsule and light curing had no negative effects. [ABSTRACT FROM AUTHOR]

There are needs and challenges in using natural resources to produce advanced materials with sustainability. So, in this modern time, natural fibres are used as reinforcement in composites because of their excellent properties, such as lower costs, biodegradability, lightweight, high corrosion resistance, high wear resistance, fewer health hazards and availability. However, greenhouse gases are released by the open burning of crop residues, such as wheat straw, rice straw, barley and many others, which increases global warming and declines air quality. So, in this experimental work, wheat straw fibres (WSFs) were used as natural fibres because of several factors, such as abundant availability, promoting of green composites and keeping rural areas clean (i.e. pollution-free) by reducing open burning. The same weight percentage of WSFs of different uniform mesh sizes was used with epoxy resin to fabricate the specimens for measuring the tensile and flexural properties as per the ASTM D 638 and D 790 standards. The results show that different behaviour of all specimens was observed under tensile and flexural loading. However, a specimen devoid of WSFs has the highest ultimate tensile and flexural strength, which were 25.064 MPa and 70.25 MPa, respectively. [ABSTRACT FROM AUTHOR]

This study investigates the combined influence of temperature and pre-bending (PB) on the flexural properties of Carbon Fiber/Epoxy (CF/Epoxy) composites. The study demonstrated the influence of temperature on CF/Epoxy's flexural characteristics, noting a marginal reduction in stiffness at higher temperatures (HT = 1 0 0 ° C) compared to room temperature (RT = 2 5 ° C). Notably, even under HT, the composite exhibited a commendable load-bearing capacity, with a 29% reduction in strength. Additionally, the investigation focused on the impact of PB on CF/Epoxy's flexural properties. The PB resulted in very small reductions in flexural strength (10%). It was observed that when subjected to both PB and HT, the material exhibited a collective response, with temperature exerting a more dominant influence than PB. Significantly reduced the flexural properties, resulting in a substantial 35% decrease in strength, surpassing the individual effects of temperature or PB. The findings emphasize the significant impact of the combined influence of temperature and PB on CF/Epoxy, shedding light on the material's behavior under varying environmental conditions. [ABSTRACT FROM AUTHOR]

In the present work, a combination of virgin polypropylene and E-glass fiber was subjected to ten (10) reprocessing cycles via extrusion and compression molding techniques to mimic recycling and its impacts on the bending properties of the composites. The samples were characterized using Fourier transform infrared (FTIR) spectroscopy, x-ray diffraction (XRD), scanning electron microscopy (SEM), and melt flow index (MFI). The results revealed a gradual depreciation in flexural properties after each reprocessing cycle. The XRD analysis indicated a substantial reduction of peak intensities, degrees of crystallinities, and average crystallite sizes, explaining the lowered flexural properties in addition to a possible reduction in glass fiber lengths (fiber attrition). Melt-processing behavior shows a progressive increase of MFI from 7 to 19.16 g/10 min, confirming the probable damage in molecular weight and loss of complex viscosity. Chemical and structural analysis showed no alteration in the polypropylene major functional groups. It is concluded that the reductions in molecular weight and composites' properties occurred due to chain scission from recycling effects; hence, glass fiber-reinforced polypropylene composites can be recycled only three (3) times unless it is refreshed by the addition of virgin parts to compensate for the lost property. [ABSTRACT FROM AUTHOR]

The notch effects on the mechanical behavior of Liquid Silicon Infiltration (LSI) based continuous carbon fiber reinforced silicon carbide (C/C-SiC) was studied. The in-plane (IP) and out-of-plane (OP) flexural properties of notched and unnotched samples with fiber orientations (0°, 45° and 60°) were determined through 3-point-bending (3PB) and single notched beam (SENB) tests. Despite the significant difference in bending modulus, the strength depends only slightly on the fiber orientation and loading direction, which could be explained through the uneven distribution of SiC-matrix within the block-like structure of C/C-SiC. This unique micro-structure also leads to a relatively constant value of notch sensitivity in the IP direction, and the sensitivity to the notch is relatively low for all tested C/C-SiC specimen configurations. Furthermore, due to the large differences of fracture mechanism, the work of fracture (WOF) in the IP direction is significantly smaller than in the OP direction for all fiber orientations. [ABSTRACT FROM AUTHOR]

Low damage tolerance and residual strength are the main drawbacks of carbon fiber composite laminates that limit their application in many lightweight structures. This study demonstrates the exceptional damage tolerance and high fracture toughness of carbon-Kevlar hybrid laminate, where Kevlar plies are placed between two carbon fiber face sheets. Flexural strength after damage and mode I translaminar fracture toughness of carbon and Kevlar and the hybrid laminates were evaluated using three-point bending and single-edge notched bending tests, respectively. The damage mechanisms in the three configurations were investigated using micro-computed tomography and correlated with their mechanical responses. The results showed that the hybrid laminate could sustain 70% of the laminate strength after fiber damage occurs and can sustain the same strength for large strains, unlike carbon and Kevlar fiber laminates, where they both lose their mechanical integrity after fiber breakage. Moreover, this laminate showed 200% and 170% larger specific absorbed energy than carbon and Kevlar laminates, respectively. The improvement can be justified by the propagation of fiber breakage at three different positions in the Kevlar core and the delamination at the carbon-Kevlar interface that allowed larger energy dissipation during fracture. Additionally, it showed 21% and 42.7% larger absolute and specific fracture toughness, respectively, than the carbon fiber laminate. [ABSTRACT FROM AUTHOR]

The existence of a notch in a composite structure is inevitable. However, its presence automatically changes the stress distribution pattern in the component. The present work analyses the flexural performance of glass/epoxy composite with single and pair holes in different locations and sizes. In paired holes (2 mm diameter), stress concentrations were placed at a distance of 10, 20 and 30 mm. In single hole specimens, the notch locations were at 4, 8 and 12 mm distance with hole diameter of 2, 4 and 6 mm. The work suggests a significant drop (30.21%) of flexural strength with a hole placed at 10 mm, which eventually reduced up to 14 ± 1% with the hole moving further away in a paired configuration. Although, the optimum performance was at 20 mm location with improvement in flexural modulus by 12.27%. The single hole arrangement reiterates the significance of hole location and reports that flexural strength decreases significantly as it moves away from the support end (42.44%). However, this drop is never linear, suggesting a fall between mid-location. The notch size appears as an important element in flexural performance for it changes the stress distribution around the hole and the associated damage propagation. The above analysis supported Weibull statistics and found good agreement with experimental results. [ABSTRACT FROM AUTHOR]

Kenaf fibres are one of the natural fibres that have been widely explored since the fibres are low in cost, have excellent mechanical properties and biodegradability features. Recently, there have been numerous efforts to employ kenaf fibres reinforced composites in a wide range of applications. One of the concerns is that these composites may be exposed to several ranges of corrosive conditions during their in-service life and their durability performance is extremely necessary. Therefore, the aim of this work is to study the mechanical response subjected to flexural and low velocity impact tests of kenaf/epoxy composites with a variety of corrosive solutions, after being exposed to hydrochloric acid (HCl) and sodium hydroxide (NaOH) solutions for durations of 12, 24 and 36 days. The experiment result demonstrated that the corrosive solutions have a detrimental effect on the flexural properties and impact response of composites. The degradation effect on composites is also found to be dependent on the exposure period in the corrosive solutions. On the other hand, acidic environments have been shown to have a more aggressive effect on the performance of composites than an alkaline environment. [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) techniques, such as fused filament fabrication (FFF), play nowadays an important role for processing polymeric materials, owing to their considerable advantages such as its cost-effectiveness and wide range of usable materials. In particular, techniques such as FFF involve multiple parameters that critically influence printing quality, including the choice of filament material. Although, existing literature extensively investigates how these parameters affect print quality and overall process efficiency, the relative influence of specimen weight apart from process parameters is rarely discussed. In this study, we focus on the flexural properties of PETG processed via FFF. Using an orthogonal Taguchi design of experiment, we analyzed the influence of four control factors: infill density, infill pattern, layer height, and printing speed. Flexural properties were evaluated based on the flexural modulus of elasticity, flexural yield strength, and flexural absorbed energy, both in absolute terms and normalized to weight. Following the Taguchi analysis, grey relational analysis (GRA) was used to identify the optimal set of parameters for both absolute and reduced values. This study yields valuable insights into each parameter impact, the efficient fabrication capabilities, while it also provides guidelines for future research. By employing a combination of Taguchi DOE and GRA, the obtained flexural properties of the printed parts were significantly improved and optimized based on different criteria, taking into account the weight of specimens and printing time, and finally, it was deduced that the consideration of reduced values can reveal promising alternative strategies for obtaining optimized parts. [ABSTRACT FROM AUTHOR]

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.

Recently, short-fiber-reinforced thermoplastic composites (SFRTPCs) have been playing a more and more crucial role in the application of automotive interior materials due to their advantages of low density and environmental resistance properties. However, their relevant mechanical properties need to be optimized. Previous investigations revealed that the surface modification of fibers is useful to improve their mechanical properties. In this work, carbon fiber (CF)-reinforced polylactic acid (PLA) composites modified with MXene and graphene oxide (GO) were prepared by twin-screw extrusion and injection molding methods. Short CF was firstly modified with polyetherimide (PEI), then different weight ratios of MXene-GO (1:1) were subsequently modified on PEI-CF. Finally, the flexural properties and failure mechanisms were analyzed. The results showed that MXene-GO was successfully coated on CF surface, and the flexural strength and modulus of CF-PEI-MXene-GO-reinforced PLA (CF-PEI-MG/PLA) composite were improved compared to that of CF/PLA composite. In addition, the fracture sections of the composites were flat and white, and the fibers bonded well with PLA for CF-PEI-0.1MG/PLA composite compared to CF/PLA composite. The present study could provide a reference for further improving the mechanical performance of PLA-related composites. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

This study aims to investigate the influence of post-polymerization (post-curing) conditions on surface characteristics, flexural properties, water sorption and solubility, and cytotoxicity of additively manufactured denture base materials. The tested specimens were additively manufactured using digital light processing and classified into different post-curing condition groups: submerged in water (WAT), submerged in glycerin (GLY), and air exposure (AIR). An uncured specimen (UNC) was used as a control. The surface topography and roughness were observed. The flexural strength and modulus were determined via a three-point bending test. The water sorption and solubility were subsequently tested. Finally, an extract test was performed to assess cytotoxicity. Different post-curing conditions had no significant effects on the surface topography and roughness (Sa value). Various post-curing conditions also had no significant effects on the flexural strength. Notably, the flexural modulus of the WAT group (2671.80 ± 139.42 MPa) was significantly higher than the AIR group (2197.47 ± 197.93 MPa, p = 0.0103). After different post-curing conditions, the water sorption and solubility of the specimens met the ISO standards. Finally, all post-curing conditions effectively reduced cytotoxic effects. Post-curing with different oxygen levels improved flexural properties, and flexural modulus significantly increased after the specimens were submerged in water. In addition, water sorption and solubility, and cytocompatibility were optimized by post-curing, irrespective of the post-curing conditions. Therefore, the water-submerged conditions optimized the flexural modulus of the 3D-printed denture base materials. • The underwater method of post-curing resulted in the highest flexural modulus. • Flexural strength was not significantly affected by different oxygen content. • Different post-curing conditions did not induce cytotoxicity. • The underwater method is a promising post-processing procedure. [ABSTRACT FROM AUTHOR]

Traditional steel-based reinforcements face corrosion issues that compromise the durability of concrete structures. Large concrete covers are recommended to mitigate corrosion of steel reinforcements, resulting in thicker, heavier structures with increased material consumption and costs, making them less sustainable. Textile reinforced concrete (TRC), with its corrosion resistance, high tensile strength, drapeability, formability, and lightweight nature, offers a sustainable alternative. It necessitates less concrete cover, thereby reducing costs and material consumption, making it suitable for lightweight and durable structural components. Various combinations of textile structures achieved through selective adjustments to fibre, yarn, and fabric geometry present significant potential for developing customized TRC elements. This issue of Textile Progress delves into the environmental impact of construction materials, TRC composition and manufacturing, mechanical testing techniques, and the influence of textile (yarn, braided fabric, woven fabric, knitted fabric, 3-D spacer fabric, nonwoven fabric) structural parameters on TRC behaviour. Additionally, the effects of textile coatings, filler incorporation, and discrete fibre integration on TRC properties are also explored. Overall, textile reinforcement in concrete enhances properties such as tensile strength, ductility, strain hardening behaviour, flexural strength, impact resistance, toughness, multiple cracking behaviour, and reduced crack width and spacing, whilst also bolstering resistance to environmental factors. [ABSTRACT FROM AUTHOR]

Nonwoven webs can be used as interleaves to improve the delamination resistance of fiber-reinforced composites. This paper addresses the flexural and interlaminar fracture behavior of glass fiber/epoxy composites with Spunbond polypropylene nonwoven interlayers. For this purpose, 7-layer hybrid composites were fabricated in intraply configuration using four layers of glass fabric and three interlayers of polypropylene spunbond nonwoven fabric. The effect of nonwoven fabric parameters, including areal weight densities [40, 50, 60, 70, and 90 GSM (g/m2)], and fabric orientation (longitudinal and cross direction) was investigated. The results of the three-point bending test showed that the nonwoven interlayer had a positive effect on the maximum flexural load and work of fracture. It caused an increase of approximately 163% in the maximum load of the sample, which had a nonwoven interlayer weight of 70 GSM compared with the non-hybrid glass sample. The glass fiber/epoxy composite was delaminated at lower strains than composites with polypropylene interlayer. The results showed that in hybrid samples, the presence of nonwoven interlayer led to increased Mode-II fracture toughness of composite (GIIC) by 44% and 56% in the samples which has the nonwoven interlayer weight of 90 and 50 GSM, respectively, compared to the non-hybrid glass fabric sample. [ABSTRACT FROM AUTHOR]

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 FROM AUTHOR]

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 injectionmolded 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. [ABSTRACT FROM AUTHOR]

This work deals with the development and investigation of self-reinforced polylactic acid (SRPLA) composites manufactured from two different nonwoven preforms with two different bicomponent filament architectures. The SRPLA nonwovens prepared via spun bonding technology have two different bicomponent filament architectures, that is, core-sheath, and islands in the sea. For the core-sheath filaments, spunbound nonwovens are compared with the dry-laid SRPLA nonwovens. The SRPLA nonwoven preforms are compression molded at three different mold temperatures to fabricate composite plates. The optimum mold temperature is identified based on the flexural properties and residual void volume fraction of composites. The flexural modulus and strength are about 38% and 50% higher than those of the pure PolyLactic Acid (PLA) matrix, respectively. The influence of bicomponent filament architecture on the mechanical performance of composites is negligible, whereas the nonwoven architecture leads to significant differences both in the residual void volume fraction and in the mechanical properties of composites. Finally, the mechanical properties of the SRPLA composites are compared with those of the conventional composites to prove their applicability to semi-structural parts. [ABSTRACT FROM AUTHOR]

This study prepares composite panels with three Polylactic acid (PLA)-based materials via the multi-material fused filament fabrication method. The influences of four processing parameters on the mechanical properties of 3D-printed samples are investigated employing the Taguchi method. These parameters include the relative volume ratio, material printing order, filling pattern, and filling density. A "larger is better" signal-to-noise analysis is performed to identify the optimal combination of printing parameters that yield maximum bending strength and bending modulus of elasticity. The results reveal that the optimal combination of printing parameters that maximizes the bending strength involves a volume ratio of 1:1:2, a material sequence of PLA/foam-agent-modified eco-friendly PLA (ePLA-LW)/glass fiber-reinforced eco-friendly PLA (ePLA-GF), a Gyroid filling pattern, and a filling density of 80%, and the optimal combination of printing parameters for maximum bending modulus involves a volume ratio of 1:2:1 with a material sequence of PLA/ePLA-LW/ePLA-GF, a Grid filling pattern, and 80% filling density. The Taguchi prediction method is utilized to determine an optimal combination of processing parameters for achieving optimal flexural performances, and predicted outcomes are validated through related experiments. The experimental values of strength and modulus are 43.91 MPa and 1.23 GPa, respectively, both very close to the predicted values of 46.87 MPa and 1.2 GPa for strength and modulus. The Taguchi experiments indicate that the material sequence is the most crucial factor influencing the flexural strength of the composite panels. The experiment result demonstrates that the flexural strength and modulus of the first material sequence are 67.72 MPa and 1.53 GPa, while the flexural strength and modulus of the third material sequence are reduced to 27.09 MPa and 0.72 GPa, respectively, only 42% and 47% of the first material sequence. The above findings provide an important reference for improving the performance of multi-material 3D-printed products. [ABSTRACT FROM AUTHOR]

In this study, the influences of the aging period and temperature on the flexural properties of CFRP laminates were investigated experimentally and numerically. Samples with cross-ply (CP) and angle-ply (AP) layups were prepared and immersed in water tanks with different temperatures (30 ℃ and 50 ℃). Three-point bending tests were performed for unaged, 15, and 35 days-aged composite laminates. SEM, optical, and Fourier transform infrared spectroscopy were employed to investigate the morphology, chemical structures, and failure mechanisms. It was found that the water molecule uptake mainly existed among the matrix and fiber–matrix interface. As a result, the CP laminates showed a buckling-driven delamination failure at the compressive surface, while debonding and kinking failure appeared for AP laminates. A higher temperature or longer immersion period worsens the laminate performance. For CP samples aging for 35 days, the flexural strength showed a 32.8% reduction at 30 ℃ and a 40.6% reduction at 50 ℃. However, the reduction of flexural strength of AP samples was 29.7–31.1% at both temperatures, which was insensitive to the temperature. A finite element model was also developed, and the numerical results showed that the differences in flexural properties reduction were due to the distinct load-carrying mechanisms. [ABSTRACT FROM AUTHOR]

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.

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.