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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]

The present work studies the positive or negative effect of zeolite mineral on the tensile and flexural mechanical behavior of a wood-plastic composite. Eight different blends were developed, the components used were wood flour (WF), polypropylene (PP), zeolite (Z) and maleic anhydride modified polypropylene (MAPP) as coupling agent. The eight blends were made using a counter-rotating twinscrew extruder, while the specimens were produced on a plastic injection molding machine with a 60ton clamping capacity. The standards used to determine the tensile and flexural mechanical properties were ASTM 638 and ASTM 790, respectively. Ten repetitions of each mixture were carried out. In addition, a reference (100% polypropylene) was used to compare the results obtained to determine whether the effect of using the zeolite mineral generated positive or negative results in the compounds obtained. Both studies showed that as the proportion of zeolite increases in the blend, the tensile and flexural properties are affected. However, the mixture (M7) with proportions in its components of, 34.375% WF, 55.875% PP, 6.75 % Z and 3% MAPP, showed an increase in the tensile and flexural mechanical properties, indicating a strong relationship between the components that integrate the wood-plastic composite (WPC), mainly between wood and mineral. [ABSTRACT FROM AUTHOR]

Polyurethane cement composite is a new organic–inorganic composite material with high strength, corrosion resistance, and fast curing. It is a complement and alternative to traditional cement materials. The flexural properties of polyurethane cement composites are the basic mechanical index of the material. In order to study the flexural properties under different temperature loads, a molecular model was established, the chemical reaction process of polyurethane cement and the temperature response mechanism was analyzed, and the preparation process of polyurethane cement was proposed. Then, bending tests were carried out in strain-controlled mode to obtain the specimens' bending strength and stiffness modulus under different temperature loads. The test results showed that the tensile strength of polyurethane cement decreased first, then increased, and finally decreased with the increase in temperature, while the bending stiffness modulus decreased with the increase in temperature. Combined with the theoretical derivation, the damage mode of the samples under different temperature loads was analyzed, and the "L-type" damage strain curve was obtained. The results showed that the proposed theory could effectively explain the mechanism of action and flexural properties of polyurethane cement composites under temperature loading, which is a significant improvement to the application of polyurethane cement composites in practical engineering. [ABSTRACT FROM AUTHOR]

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 selfcure 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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Graphene quantum dots are zero-dimensional nanoparticles that are used widely in advanced composite materials such as filtration membranes, adsorbent materials, optical devices, biomedical applications (especially biosensors), flame retardancy, and automotive, aerospace, agricultural and environmental applications. In this article, the mechanical properties (flexural strength, flexural strain and elastic modulus) of polymer-based nanocomposites will be investigated. The main novelty of the current work is the green synthesis of graphene quantum dots which were extracted from lemon juice. XRD and FTIR tests have been conducted to determine the composition of the prepared powder. The polyester resin and graphene quantum dots were mixed with different weight percentages (0.25%, 0.5% and 1% wt. graphene) and processed to fabricate nanocomposite samples. The mechanical properties of the prepared samples were measured according to the ASTM D790-17 standard testing method. The experimental results show that the strength increased from 80 MPa to about 112 MPa (40% increase in strength) by adding 0.25% wt. graphene quantum dots. The flexural modulus decreased from 2.70 GPa to 2.06 GPa by adding 1% wt. graphene content (23% decrease). The flexural strain increased considerably (up to 14.2%) by adding 1% wt. graphene quantum dots. Consequently, the ductility of the nanocomposites increased by adding green synthesized graphene quantum dots. The fracture behavior changed from brittle fracture mode to ductile fracture mode by adding the graphene quantum dots. Additionally, a flame retardancy test has been carried out by implementing the UL-94 test. The fabricated nanocomposites showed fire retardancy due to char barrier formation on the surface of the nanocomposites. [ABSTRACT FROM AUTHOR]

In this paper, the three-point bend flexural testing of composites reinforced with woven glass fibers and unidirectional glass fibers are presented. The experimental study was done according the ASTM standard. A finite element simulation was done in order to investigate the mechanical behavior of woven glass fibers and unidirectional glass fibers reinforced polymer composites. The finite element results were compared with experimental data, thus obtaining very close values. The composites plates were obtained through hand layup technology. [ABSTRACT FROM AUTHOR]

Copyright of Dokuz Eylul University Muhendislik Faculty of Engineering Journal of Science & Engineering / Dokuz Eylül Üniversitesi Mühendislik Fakültesi Fen ve Mühendislik Dergisi is the property of Dokuz Eylul Universitesi Muhendislik Fakultesi Fen ve Muhendislik Dergisi and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Materials & Technologies / Materiali in Tehnologije is the property of Institute of Metals & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract SiC/SiC composites are promising structural candidate materials for various nuclear applications over the wide temperature range of 300–1000 °C. Accordingly, irradiation tolerance over this wide temperature range needs to be understood to ensure the performance of these composites. In this study, neutron irradiation effects on dimensional stability and mechanical properties to high doses (11–44 dpa) at intermediate irradiation temperatures (˜600 °C) were evaluated for Hi-Nicalon Type-S or Tyranno-SA3 fiber–reinforced SiC matrix composites produced by chemical vapor infiltration. The influence of various fiber/matrix interfaces, such as a 50–120 nm thick pyrolytic carbon (PyC) monolayer interphase and 70–130 nm thick PyC with a subsequent PyC (˜20 nm)/SiC (˜100 nm) multilayer, was evaluated and compared with the previous results for a thin-layer PyC (˜20 nm)/SiC (˜100 nm) multilayer interphase. Four-point flexural tests were conducted to evaluate post-irradiation strength, and SEM and TEM were used to investigate microstructure. Regardless of the fiber type, monolayer composites showed considerable reduction of flexural properties after irradiation to 11–12 dpa at 450–500 °C; and neither type showed the deterioration identified at the same dose level at higher temperatures (>750 °C) in a previous study. After further irradiation to 44 dpa at 590–640 °C, the degradation was enhanced compared with conventional multilayer composites with a PyC thickness of ˜20 nm. Multilayer composites have shown comparatively good strength retention for irradiation to ˜40 dpa, with moderate mechanical property degradation beginning at 70–100 dpa. Irradiation-induced debonding at the F/M interface was found to be the major cause of deterioration of various composites. [ABSTRACT FROM AUTHOR]

This study aims to enhance the flexural properties of sandwich composites made from glass or carbon face and glass and carbon fibre Z-pin inserted extruted-polystyrene (XPS) foam cores. Carbon and glass pins were placed through XPS foams with two different column and row densities (15 and 30 mm). Results indicated that flexural loads, strength and modulus of glass/XPS and carbon/XPS sandwich composites significantly increased after inserting of glass and carbon rods. Core shear strengths and facing stresses of glass/XPS and carbon/XPS increased by increasing of carbon or glass rod densities. The rod type, rod density and face type of the sandwich composites are considered as significant parameters which affect the flexural behaviour of sandwich composites while using carbon rods enhanced flexural properties more than that of using glass rods due to better interfacial bonding. [ABSTRACT FROM AUTHOR]

Highlights • Developing composite materials based on cereals such as corn is beneficial to the industrial application of these crops. • Antibacterial polylactid acid nanocomposites are developed by using Ag@GO as filler via in-situ polymerization. • Two preparation methods of polylactid acid-based nanocomposites were compared. • Ag@GO/polylactid acid composite via in-situ polymerization showed better mechanical and antibacterial properties. • The in-situ polymerization process is environmental friendly due to no need of solvents. Abstract Mechanical and antibacterial properties of polylactid acid have to be improved for advanced applications of medical instruments, artificial tissues and active packaging, etc. In this work, antibacterial polylactid acid nanocomposites are developed by using silver-graphene oxide hybrid (Ag@GO) as filler via in-situ polymerization and direct mechanical blending method, respectively. The effects of Ag@GO content and preparation method on the mechanical and antibacterial properties of the polylactid acid nanocomposites are investigated. It is shown that the flexural strength of the Ag@GO/polylactid acid nanocomposites increases from 326 to 942 K Pa as the Ag@GO content increases from 0 to 2.0 wt.%; the antibacterial rate (to Escherichia coli ATCC 25,922 and Staphylococcus aureus ATCC 6538) increases from 0 to 99% as the Ag@GO content increases to 2.0 wt.%. Further, the flexural strength and antibacterial properties of the composites prepared by the in-situ polymerization method are greatly improved and are consistently higher than those of the composite counterparts prepared by the direct mechanical blending method. [ABSTRACT FROM AUTHOR]

In recent years, researchers and scientists are facing problems in terms of environmental imbalance and global warming owing to numerous use of composite materials prepared by synthetic fibers and petrochemical polymers. Hence, an increasing attention has been devoted to the research and development of polymer composites reinforced with the natural fibers. The natural fibers are the most suitable alternative of synthetic fibers due to their biodegradability, eco-friendliness and acceptable mechanical properties. The natural fibers are attracting the researchers and scientists to exploit their properties by amalgamating them with the polymer. The properties of natural fiber reinforced polymer composites mainly depend upon various factors such as properties of fibers and matrices, fiber loading percentage, size and orientation of fibers, stacking sequences, degree of interfacial bonding, fiber surface treatments, hybridization and incorporation of additives and coupling agents. Tensile and flexural tests are the most important investigations to predict the applications of the materials. A good number of research has been carried out on tensile and flexural properties of natural fiber reinforced polymer composites. In this paper, a review on tensile and flexural properties of natural fiber reinforced polymer composites in terms of effects of fiber weight fraction, geometry, surface treatments, orientations and hybridization is presented. Moreover, recent applications of natural fiber reinforced polymer composites are also presented in this study. [ABSTRACT FROM AUTHOR]

Copyright of FME Transactions is the property of University of Belgrade, Faculty of Mechanical Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Objective Synthesize a new BPA-free monomer for use in methacrylate-based materials and evaluate critical properties of resin and composite materials based on the monomer. Methods Bis-EFMA was synthesized through reaction between 9,9-bis[4-(2-hydroxyethoxy)-phenyl]fluorene and 2-(methacryloyloxy)ethyl isocyanate. Experimental Bis-EFMA-based resin (Bis-EFMA/TEGDMA = 50/50, wt./wt.) and composite were prepared. Critical properties were investigated according to standard or referenced methods Bis-GMA/TEGDMA (50/50, wt./wt.) resin system, Bis-GMA-based composite and 3 M ESPE Filtek™ Z250 were used as controls. Results FT-IR and 1 H NMR spectra confirmed the structure of Bis-EFMA monomer. Cured resin materials: Bis-EFMA-based and Bis-GMA-based resins had nearly the same degree of conversion ( p > 0.05); Bis-EFMA-based resin had significantly lower shrinkage, water sorption and solubility, and cytotoxicity than Bis-GMA-based resin (p < 0.05); flexural properties of Bis-EFMA-based resin were all higher than those of Bis-GMA-based resin (p < 0.05). Cured composite materials: There was no significant difference in conversion ( p > 0.05); Bis-EFMA-based composite had significantly lower shrinkage and solubility ( p < 0.05); water sorption of Bis-EFMA-based composite and Z250 were similar ( p > 0.05), but lower compared to Bis-GMA-based composite ( p < 0.05); Bis-EFMA-based composite had the deepest curing depth ( p < 0.05); Before water immersion, there was no significant difference in flexural strength between Bis-EFMA-based composite and each control composite ( p > 0.05), while FS became lower than that of Z250 ( p < 0.05), but higher than that of Bis-GMA-based composite ( p < 0.05) after water immersion; Flexural modulus of Bis-EFMA-based composite and Z250 were nearly the same ( p > 0.05), higher than that of Bis-GMA-based composite ( p < 0.05); Bis-EFMA-based composite showed less cytotoxicity than Bis-GMA-based composite and Z250 ( p < 0.05). Significance Bis-EFMA has potential as a substitute for Bis-GMA to prepare Bis-GMA-free dental composites. [ABSTRACT FROM AUTHOR]

Outdoor durability of wood plastic composites is a major focus of research and development efforts toward development of more robust building materials. Exterior exposure of wood plastic composites can result in weathering, moisture absorption, fungal and termite attack to various levels of severity depending on the composite formulation. Long-term (> 6 years) field exposure studies of wood plastic composites are lacking in the scientific literature. It is the overall goal of this paper to report on a ten-year field study of wood plastic composites performed in Santiago, Chile. The wood plastic composite formulations were comprised of polypropylene, wood flour, and various additives. Qualitative measurements were made on the stakes each year including the determination of decay and termite ratings on a scale of 1 to 10 as specified in American Wood Preservers' Association Standards. Surface weathering or discoloration, surface fungi colonization, presence of mold, and/or lichen was noted. The amount of dimensional change (swelling) of the samples in ground contact was determined. Determination of flexural properties of the control and 10-year exposed wood plastic composite stakes were conducted. All the wood plastic composite stake formulations maintained excellent performance ratings after the 10-year field exposure with ratings of 10 for decay and 10 for termites. The wood plastic composites stakes experienced swelling in contact with the soil with the majority of swelling occurring during the first year of exposure. Although the wood plastic composite stakes did well regarding decay and termite performance, the portion of the stakes exposed above ground exhibited various amounts of weathering, surface fungal colonization, and mold and mildew depending on the formulation. Flexural properties of the wood plastic composite stakes decreased or were maintained for the 10-year exposure depending on the composite formulation. [ABSTRACT FROM AUTHOR]

Numerical simulation with progressive damage criterion is implemented to investigate the effect of porosity on the bending properties of 2D cross-ply carbon/carbon (C/C) composites. The mechanical properties of Pyrocarbon matrix regarding the change of porosity are calculated by using Mori-Tanaka approach. Combining with the stiffness degradation scheme, the ultimate bending strengths are calculated in Abaqus though a user-defined subroutine (USDFLD). Delamination is modelled by inserting cohesive elements between two adjacent plies. A good agreement is obtained when the FEM results are compared to three-point bending experiments. The FEM results show that the bending strength decreases greatly with the increase of porosity. When the porosity reaches up to 18%, the bending strength is decreased by 57%. The major fracture behaviors are interlamination delamination and continuous crack damage in 90° plies. With the increase of porosity, more severe interlamination delamination will be slightly aggravated. In addition, the increase of porosity will also accelerate the damage in 90° plies. [ABSTRACT FROM AUTHOR]

A carbon/carbon (C/C)–Cu composite reinforced by novel carbon fiber 2.5D-braided preforms was fabricated through pressureless infiltration technique (PLI). The microstructure of the developed composite was characterized by scanning electron microscopy, X-ray diffraction, and energy dispersive spectroscopy. The mechanical, tribological, and electrical properties of the C/C–Cu composite were compared with those of a C/C composite and a carbon/copper (C/Cu) contact strip material. Results showed that the proposed composite formed an excellent network conduction structure. Moreover, the composite exhibited a high flexural strength of 215 MPa, excellent compression strength of 324 MPa, and a particularly low electrical resistivity of 0.63 μΩm, validating its advantages over the C/Cu composite strip in terms of mechanical and electrical properties. The component phases (TiC) of the C/C–Cu composite formed an excellent interconnected structure, which stiffened the interface between the Cu alloy and the pyrocarbon matrix and resulted in excellent mechanical and electrical properties. The friction coefficients of the C/C, C/C–Cu, and C/Cu composites were 0.152, 0.169, and 0.062, respectively. The C/Cu composite exhibited the worst mechanical and electrical performance despite achieving the lowest friction coefficient. Thus, the C/C–Cu composite is a promising new type of sliding electrical contact material. [ABSTRACT FROM AUTHOR]

Hybrid composites were prepared with jute fabric and un-shredded newspaper in polyester resin matrix. The experiment was designed 1:2 weights ratio jute and unshredded newspaper to have 42 (w/w)% fibre content hybrid composites and two different sequences jute/paper/jute and paper/jute/paper of waste newspaper and jute fabric arrangement. Reinforcing material is characterized by chemically, X-ray diffraction methods, Fourier transform infrared spectroscopy and tensile testing. The tensile, flexural and interlaminar shear strength and fracture surface morphology of composites were evaluated and compared. It was found that tensile and flexural properties of the hybrid composite are higher than that of pure paper-based composite but less than pure woven jute composite. The hybridization effect of woven jute fabric and layering pattern effect on mechanical properties of newspaper/woven jute fabric hybrid composites were studied. The test results of composites were analyzed by one-way ANOVA (α = 0.05), it showed significant differences among the groups. [ABSTRACT FROM AUTHOR]

In this work, the effect of moisture absorption on the mechanical properties of particulate composite materials is studied. Moisture absorption constitutes a main parameter affecting the thermomechanical behaviour of composites, since it causes plasticization of the polymer matrix with a concurrent swelling. In the present work, the influence of water absorption on the flexural properties of particle-reinforced composites was thoroughly investigated. It was found that during the process of moisture absorption there exists a variation of the flexural properties closely related to the degradation of the mechanical behaviour of the composite, as well as the percentage amount of moisture absorbed. Experiments were carried out with composite made of epoxy resin reinforced with low-content iron particles. The variation of ultimate stress, breaking strain, deflection, elastic modulus and Poisson ratio due to water absorption was examined. [ABSTRACT FROM AUTHOR]

The study of mechanical properties of carbon nanotube reinforced polymeric materials under different environmental conditions are very much essential as this material possesses potential for using it in structural parts, automobiles, marine field and so on. This study deals with the effect of moisture absorption on the mechanical and thermal properties of carbon nanotube/epoxy composites by immersing it in sea and distilled water at 30℃ temperature and at 75% Relative Humidity (RH) humidity. Composite specimens containing different wt.% of carbon nanotubes were prepared, tested and subjected to water immersion test. The flexural properties, hardness and glass transition temperature (Tg) of water-immersed specimens were evaluated and compared with unexposed specimens as per the American Society for Testing and Material (ASTM) standard. It is concluded that the water absorption brought certain loss in the mechanical properties and reduction in Tg of the composites. It was also found that moisture uptake affected both sea and distilled water samples in different ways. [ABSTRACT FROM AUTHOR]

Three-dimensional spacer fabrics due to their specific structural features have achieved significant importance to be used as highly effective technical textiles especially in composite manufacturing. Increasing applications of three-dimensional fabrics in technical fields as well as the high ability of knitting process in production of highly structured-knitted preforms made the researchers to be focused on finding novel structures with high potential application as the composite reinforcements in order to achieve some desired properties. Along with others researches, in this paper an especially structured three-dimensional spacer weft-knitted fabrics was produced on an electronic flat knitting machine, using 1680 denier high-tenacity polyester yarn. The fabrics samples were employed in thermoset composite manufacturing process using the epoxy resin. In order to investigate the mechanical behavior of the composite samples in term of their flexural performance, a three-point bending test was performed. For precise investigation, numerical simulation based on finite element method was also applied. Good correlation between the experimental and theoretical results showed such reasonable validity of the proposed model for simulating the mechanical behavior of the spacer-knitted reinforced composite under external bending loads. [ABSTRACT FROM AUTHOR]

This paper investigates the flexural properties of Arenga Pinnata fibre reinforced epoxy composite (APREC) in relation to its fibre arrangement. The composites were produced using Arenga Pinnata fibre as the reinforcement material and epoxy resin as the matrix. In this work, two types of Arenga Pinnata fibre arrangement were under-studied, randomly distributed and unidirectional distributed (UD). Samples were prepared at 10vol%, 15vol%, 20vol%, and 25vol% of fibres reinforcement to matrix ratio for both types. Three-point bending configuration flexural tests were performed for both randomly distributed APREC and UD APREC at 10vol%, 15vol%, 20vol%, and 25vol% respectively. Results indicated that UD APREC have better flexure modulus and flexure strength for all the fibre loading percentages (vol%) as compared against the randomly distributed APREC. The 25vol% UD APREC showed the highest modulus (3.783 GPa) with an increment of 31.0% as compared against the pure epoxy (2.888 GPa). It was also observed that there was no significant increment on flexure strength for both random and unidirectional APREC as compared to pure epoxy (61.125 MPa), but the flexure strength value decreased for randomly distributed fibre orientation for all fibre volume percentages (vol%). [ABSTRACT FROM AUTHOR]

Carbon nanotubes (CNTs) reinforced carbon/carbon-copper (C/C-Cu-CNTs) composites were fabricated by thermal gradient chemical vapor infiltration (TGCVI). The effect of copper and CNTs on the microstructure and flexural properties of carbon/carbon (C/C) composites were investigated. Results showed that the flexural strength of C/C-Cu-CNTs composites was larger than that of pure C/C composites and C/C-Cu composites. Copper particles coated on carbon fibers reduced the contact area between pyrolytic carbon matrix and carbon fibers, leading to the decrease of flexural strength by 17.34% in direction Z and 22.44% in direction X, respectively. However, CNTs catalyzed by copper particles linked adjacent pyrolytic carbon layers together as a bridge and made propagation resistance of cracks increased, which strengthened the matrix. The flexural strength of C/C composites was improved by 33.61% in direction Z and 23.94% in direction X, respectively. [ABSTRACT FROM AUTHOR]

Purpose The purpose of this paper is to investigate the preparation and the flexural property of hollow glass microspheres (HGMs) filled resin-matrix composites, which have been widely applied in deep-sea fields.Design/methodology/approach The composites with different contents of HGMs from 47 to 57 Wt.% were studied. The voids in syntactic foams and their flexural properties were investigated.Findings The results showed that the voids quantity increased because of the increment of HGM content, whereas the exural strength and the exural modulus decreased. The fracture mechanism of the composites was also investigated by scanning electron microscope, which indicated that the composites failed by the crack extending through the microspheres.Research limitations/implications The advantages of HGMs with similar hollow spheres will be further investigated in a future research.Practical implications Results demonstrated that the properties of the composite might be tailored for specific application conditions by changing the HGM volume fraction.Originality/value The HGM filled resin-matrix composite materials have their unique properties and significant application potential. In this work, the resin-HGM composites were synthesized by mechanically mixing defined quantities of HGMs into epoxy resin, by which a kind of syntactic foams with good flexural properties could be obtained. [ABSTRACT FROM AUTHOR]

To improve the flexural properties of materials for structural applications, composite materials from paper pulp can be bonded with natural rubber. Paper pulp exhibits some bonding potentials which can further be enhanced for some tailored applications by mixing it with another bonding agent. This study describes the influence of natural rubber on the flexural and water absorption properties of paper-pulp-filled natural rubber composites for structural applications. This research was done using pulverised brown paper pulp as the filler and natural rubber was used as the bonding agent. A measured volume of natural rubber was mixed with a known quantity of paper pulp and the mixture was poured into a detachable mould and compacted for about 10 minutes to produce the composite. The developed composites were detached from the mould and allowed to cure in air at room temperature for 27 days. Flexural and water absorption tests were done on the samples. The composite developed from the mixture of 70 wt % brown paper pulp and 30 wt % natural rubber gave the best result for flexural properties, while the sample with 60-40 wt % emerged the best composition for the water absorption property. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the flexural behaviours of syntactic foam reinforced by warp knitted spacer fabric (SF-WKSF). Seven kinds of SF-WKSF samples were fabricated by warp knitted spacer fabric (WKSF) with structural parameters including surface layer structures, inclination-angle and fineness of spacer yarns, different microballoons types and contents. The flexural tests were carried out and the bending properties of SF-WKSF were analysed based on the strength and modulus values obtained from the test results. It is indicated that the SF-WKSF shows higher flexural strength and modulus compared to neat syntactic foam with almost no impact on the density of composites. The results also demonstrate that the surface layer structure, inclination-angle of spacer yarns, microballons content and type have significant effects on the flexural responses of SF-WKSF. The composites exhibit better antibending capacities by selecting larger inclination-angle, closer surface layer structure, higher density and relatively higher content of S60HS microballoons. [ABSTRACT FROM AUTHOR]

C/C-ZrC-SiC composites were fabricated by precursor infiltration and pyrolysis (PIP) process. A mixture solution of organic zirconium-containing polymer and polycarbosilane was chosen as the precursor. The porous carbon/carbon (C/C) preforms were first infiltrated in the precursor under vacuum, dried under 80 °C and then pyrolyzed at 1500 °C. After 20 cycles of PIP process, C/C-ZrC-SiC composites were obtained. The composites were further treated at 1650 °C and 1800 °C at an argon atmosphere for 2 h, respectively. The effects of high-temperature annealing on the microstructures and mechanical properties of C/C-ZrC-SiC composites were investigated. Results show that the density decreases and the different ceramic phases of the matrix get separated gradually as the annealing temperature increases. The mechanical strength decreases slightly after annealed at 1650 °C, and the downward trend is more obvious under 1800 °C in comparison to the unannealed composites. The fracture behavior of the composites changes after heat treatment. The decline of the strength and the change of the mechanical behaviors are attributed to the microstructural changes which include pores, cracks, fiber damage, weak interfacial bonding and ceramic phase separation caused by the annealing. [ABSTRACT FROM AUTHOR]

Eco-friendly textile biocomposites with PLA matrix reinforced with flax and flax/PLA weft knitted fabrics without any additional chemical treatment were prepared in this study. Five different kinds of samples were manufactured and investigated: (i) pure PLA sheet and (ii-v) PLA matrix reinforced with weft knits (ii) single jersey flax knit, (iii) single jersey flax/PLA knit, (iv) double single jersey flax knit, (v) double single jersey flax/PLA knit. Tensile and flexural properties of PLA biocomposites with weft knitted fabrics were higher than pure PLA sheet. The highest properties exhibit PLA biocomposites reinforced with single jersey flax knitted fabric. Differential scanning calorimetry (DSC) showed that crystallization rate of PLA matrix is enhanced with the presence of reinforced material - flax knit. It is possible to do an assumption that flax fibre can act as nucleating agents during the crystallization process. [ABSTRACT FROM AUTHOR]

Self-reinforced polylactic acid (SR PLA) composites incorporating cellulose nanowhiskers (CNWs) were produced by coating orientated PLA fibres with a polyvinyl acetate (PVAc)–CNW mixture as a binder prior to hot compaction at 95 °C. PLA fibres were produced with an average diameter of 11 (±0.9) μm via a melt-drawing process at 180 °C. Scanning electron microscopy (SEM) images revealed that the CNWs imparted roughness to the PLA fibre surface. Cross-sectional examination of the SR PLA composites after hot-pressing confirmed that the PLA fibres had maintained their morphology. Incorporation of 8 wt% CNWs within the SR-PLA composites revealed an increase in their flexural strength (48%) and modulus (39%) compared to the control composite (flexural strength ∼82 MPa and modulus ∼3.9 GPa). In addition, whilst the control SR-PLA composite revealed quite brittle characteristics, the addition of CNWs and PVAc gave the self-reinforced composite a more ductile behaviour. [ABSTRACT FROM AUTHOR]

The objective of this work is to enhance the mechanical properties of unidirectional [0] 8 and quasi-isotropic [0/±45/90] s glass-fiber-reinforced composites by ultrasonically dispersing alumina-nanoparticles in epoxy matrix. The well dispersed alumina-nanoparticles in epoxy resin significantly improved the mechanical properties of alumina-nanocomposites. Results from fracture characterizations of the nano-hybridized unidirectional laminates with different off-axis angles showed high improvements in the interfacial bond strength between nanophased epoxy and glass fiber. Therefore, the flexural strength, modulus, and fracture toughness of quasi-isotropic laminate are significantly improved. Results from free vibration tests showed that the beam free length has high effects on the natural frequencies and the both have insignificant effect on the storage moduli of the composite laminates. For the investigated materials, the storage moduli correlated well ( R 2 = 0.99962) with the flexural moduli. The damping ratios of the nano-hybridized quasi-isotropic and unidirectional laminates are improved by 62% and 60%, respectively. These improvements, which were achieved through conventional processing, are essentially for developing the structural components of automotive and aerospace industry. [ABSTRACT FROM AUTHOR]

A new type of 3D composite sandwich structure with foam core reinforced by composite columns, which can be called an integrated 3D composite sandwich structure, was designed, fabricated, and studied. The integrated 3D composite sandwich structure inherited the advantages and improved the shortcomings of the traditional foam core composite sandwich structures. All types of the samples with different consisting materials and structural parameters were tested and analyzed under bending load. The results show that the flexural properties of the integrated 3D composite sandwich structures are obviously better than those of the traditional foam core composite sandwich structures and due to the fact that the composite columns strengthen and stiffen the foam core. Moreover, this effect is more obvious for the better mechanical properties foam. And the structural parameters have significant influence on the flexural properties, especially the thicknesses of face sheet and foam core. However, the variety of these parameters results in a corresponding change of the mass and then effect the specific flexural properties. Consequently, it is necessary to find a balance among these parameters in order to get the optimal properties. [ABSTRACT FROM PUBLISHER]

New polyethylene composites with α-Al2O3whiskers are produced using four fibers (unpurified, cleaned, ribbon-shaped and silica-coated) differing in their purification level or surface. The influence of different fibers on the morphological, thermal and rheological properties of composites is analyzed. The composites with the ribbon-shaped and the silica-coated whiskers show the most suitable morphology and the best rheological properties together with a lower cost. The nucleating action of these fibers increases the crystallization temperature and the crystallinity of polyethylene. The enhancement in degradation temperature and flexural parameters prove that both types of alumina whiskers produce a clear reinforcement in polyethylene matrix. [ABSTRACT FROM AUTHOR]

Highlights: [•] Flexural properties of reinforced syntactic foams were investigated. [•] Syntactic foams with relatively high flexural strength and low density were obtained. [•] The fiberglass mesh can significantly enhance the flexure strength and modulus. [•] The location of fiberglass mesh changed the failure mechanisms from brittle to step-failure. [ABSTRACT FROM AUTHOR]

Highlights: [•] The PBO fiber reinforced composites were heated at high temperature. [•] After heating at 300°C, the composites had irreversible damage due to the resin. [•] Above 550°C, PBO fiber pyrolyzed and affected the composite much. [•] After heating at 550°C, the resin matrix pyrolyzed mostly and broke the interface. [•] After heating at 700°C, mechanical properties of the composites decreased much. [ABSTRACT FROM AUTHOR]

Abstract: Objectives: Short ramie fibers were selected to investigate the effect of fiber length and volume fraction on the flexural properties of ramie fiber reinforced denture base PMMA. With the aid of measured interfacial shear strength and theoretical prediction values, experimental results were well interpreted. Methods: Interfacial properties between denture base PMMA and ramie fibers were evaluated by single fiber pull-out test. Then, chopped ramie fibers were pre-stirred with PMMA powder by a mechanical blender and then mixed with MMA liquid to fabricate composites. Two crucial influencing factors, fiber volume fraction and fiber length, were studied to clarify their effects on flexural properties of composites. Results: With 1.5mm fibers addition, flexural modulus of denture base PMMA rose from 2.50 to 3.46GPa with 10vol.% fibers, while flexural strength declined steadily with increment of fiber content. If fiber length was 3.0mm, the modulus showed a growth to 3.5GPa at 4vol.% fiber content followed by a drop to 3.00GPa at 10vol.%, whereas fluctuation in strength was experienced. Experimental results were discussed by comparison with two theoretical models. Significance: Short ramie fiber reinforced denture base PMMA had higher flexural modulus than neat resin, while strength was lowered due to the weak interfacial adhesion. The potential of vegetable fibers as reinforcing agents for denture base should be further investigated by strengthening the interface between cellulose and denture base PMMA. [Copyright &y& Elsevier]

The popularity and demand for wood plastic composites (WPC) has focused research on fiber properties associated with performance. In this study, maple wood fibers (WF) were ball milled and classified into discrete size fractions. Fiber analyses showed only three distinct WF size classes (80-100, 100-200 and <200 mesh). High density polyethylene (HDPE) based WPC were made from classified WF (10 to 50%). The effect of WF size, loading, and maleated polyethylene (MAPE) coupling agent on WPC rheological behavior (torque rheometry and melt flow rate (MFR)) and flexural properties were examined. The WPC MFR decreased with wood loading, increased with a reduction in WF size. The modulus of rupture (MOR) was shown to increase with a reduction in WF size and increase with the addition of MAPE. The increase in MOR is likely due to an increase in the interfacial interaction between the polymer and WF. Modulus of elasticity (MOE) was shown to increase with an increase in wood loading and decrease with a decrease in WF size. The toughness of the WPC was shown to increase with a decrease in WF size and increase upon addition of MAPE. [ABSTRACT FROM AUTHOR]

This paper presents the results of a current study on the mechanical properties of a polypropylene matrix resin, enhanced using nanoclay filler with a special silane treatment. The study was centred on the effect of adding nanoclay and of water immersion on static and fatigue behaviour. Specimens filled up to 3% in weight were produced by an injection moulding process. The filler improved significantly bending quasi static and dynamic stiffness, and also marginally the bending strength. Surprisingly, the immersion in water for 40 days increases the bending stiffness and the bending strength. The addition of 3% w/w nanoclay promoted a negative effect in Gc. All material configurations exhibited a faster and intense stress release from the first cycles of fatigue. The 3% nano-enhanced composites exhibited higher fatigue strength than unfilled materials. [ABSTRACT FROM PUBLISHER]

Abstract: In this paper, the effect of hygrothermal ageing on the flexural properties of glass/epoxy, glass/linseed oil and glass/castor oil composites is reported. Plant oil based resins offer renewable and potentially less toxic alternatives to conventional largely petroleum based marine composites. The long-term performance of these novel composites needs to be investigated and understood before using them in structural applications. In this research it was found that in the unaged condition, the flexural properties of glass/epoxy were significantly higher than both glass/castor oil and glass/linseed oil composites. After ageing in water at 40°C for 46weeks, the properties of glass/castor oil were comparable to glass/epoxy while the properties of glass/linseed oil were remarkably lower. The decrease in glass/linseed oil performance was explained in terms of the changes in the failure modes caused by moisture uptake. [Copyright &y& Elsevier]

The objective of this research is to investigate the performances of the carbon-basalt/epoxy hybrid composites under flexural loading. In this work, the hybrid composites were manufactured by the vacuum assisted resin transfer molding (VARTM) process. The variations of flexural strength and modulus of the hybrid composite according to the number of basalt fabric were investigated, and we obtained the expression to calculate their mechanical properties. In the study of flexural properties for the hybrid composites with different stacking sequence of the reinforcements, we knew that their properties strongly depend on the reinforcing position of carbon and basalt fabric. [ABSTRACT FROM AUTHOR]

Abstract: The incorporation of natural fibres such as sisal/jute with glass fiber composites has gained increasing applications both in many areas of Engineering and Technology. The aim of this study is to evaluate mechanical properties such as tensile and flexural properties of hybrid glass fiber-sisal/jute reinforced epoxy composites. Microscopic examinations are carried out to analyze the interfacial characteristics of materials, internal structure of the fractured surfaces and material failure morphology by using Scanning Electron Microscope (SEM). The results indicated that the incorporation of sisal fiber with GFRP exhibited superior properties than the jute fiber reinforced GFRP composites in tensile properties and jute fiber reinforced GFRP composites performed better in flexural properties. [Copyright &y& Elsevier]

Abstract: In the current work, flexural properties of unidirectional long kenaf fibre reinforced epoxy (KFRE) composites are studied. The kenaf fibres were prepared into two types as untreated and treated (with 6% NaOH). The failure mechanism and damage features of the materials were categorized with the surface observation by scanning electron microscope (SEM). The results revealed that reinforcement of epoxy with treated kenaf fibres increased the flexural strength of the composite by about 36%, while, untreated fibres introduced 20% improvement. This was mainly due to the high improvement of the chemical treatment (NaOH) on the interfacial adhesion of the fibres and the porosity of the composites which prevented the debonding, detachments or pull out of fibres. For untreated KFRE, the fracture mechanisms were debonding, tearing, detachments and pull out of fibres. The developed composite exhibited superior properties compared to the previous composites based on natural and synthetic fibres. [Copyright &y& Elsevier]

The effect of lanthanum (La) salt on surface treatment of poly-p-phenylenebenzobisoxazole (PBO) fiber on flexural and tribological properties of PBO fibers reinforced polyimide (PI) composites was investigated. Experimental results revealed that flexural strength and modulus were largely improved by La salt treatment. The La salt treated composite had lower friction coefficient and specific wear rate than that of untreated one under the same testing condition. The principle of improvement in interfacial adhesion between PBO fiber and PI matrix after La salt treatment was discussed. The surface characteristics of PBO fibers were characterized by X-ray photoelectron spectroscopy. It was found that the content of polar groups on the surface of PBO fiber treated by La salt increased compared with the untreated fiber. The increase in the amount of polar groups strengthened the interfacial adhesion between PBO fibers and PI matrix, and accordingly enhanced the flexural and tribological properties. [ABSTRACT FROM AUTHOR]

Abstract: Three dimensional (3D), seven-directional braided (SiO2)f/SiO2 composites were prepared by silica sol-infiltration-sintering (SIS) method. The flexural properties were evaluated by three-point bending test. The flexural strength and flexural elastic modulus were found to be about 107MPa and 17.5GPa, respectively. The results of stress vs. deflection curve and SEM examination revealed that the fracture mechanism of the (SiO2)f/SiO2 composite was a mixed mode of brittle and ductile. The bond strength of fiber/matrix was weak at low temperature, causing the extensive fiber pull-out. On the other hand, the brittle fracture of some fibers maybe caused by the propagation of micro defect or crack, which existed in the as-prepared composites for the ten-cycle process. [Copyright &y& Elsevier]

Abstract: In this work, we report a new strategy of introducing thorns-like fiber into composites, so that the resultant composites substantially benefit from strong fiber–matrix interface adhesion. Specifically, the “thorns” could increase in interlocking molecules chains and entangle with the surrounding matrix resin, which could impede the mobility of polymer chains, as like the roots with uplift capacity. Strong interfacial adhesion between fibers and matrices is suggested by the SEM images and the DMA studies. After the thorns-like fibers are embedded into epoxy resin, the glass transition temperature (T g) and the storage modulus (E′) are higher than these of neat epoxy and untreated fibers-reinforced epoxy, respectively, and the flexural properties of the composites reinforced with thorns-like fibers are significantly increased. Therefore these novel three dimensional thorns-like fibers will be applicable for composite materials based upon its unique architecture, making it an attractive alternative to increase the performance of any matrix resin. [Copyright &y& Elsevier]