Elastic Modulus Of Composites Research Articles

Study on fire resistance and mechanical properties of modified recycled waste oyster powder in asphalt binder

AbstractIn this study, an eco‐friendly approach is presented for the innovative use of waste oyster shell (OS) powder modified with zinc stannate, aliphatic alcohols, and silane coupling agents blended with styrene‐butadiene‐styrene (SBS) modified asphalt to make a flame‐retardant binder (modified oyster shell [MOS]/styrene‐butadiene‐styrene [SBS]/MA), which is rendered flame retardant and smoke suppressive. Compared with the original SBS/MA, MOS/SBS/MA with a 2% addition rate showed a 35.44% increase in ultimate oxygen index, a 30.62% reduction in peak exotherm, a 10.87% reduction in smoke density, and a 75% reduction in volatile organic compound (VOC) emissions. It also has excellent mechanical properties, with increases in composite modulus, elastic modulus, and storage modulus of 68.58%, 97.29%, and 59.59%, respectively, at 46°C. The thermal stability of MOS/SBS/MA is also improved, with a decomposition temperature 26°C higher than that of SBS/MA. Pavement performance tests show that the water‐soaked Marshall's split strength has increased by 3.87% and the coefficient of rutting by 3.51%. Increased by 3.51%, this method effectively utilizes the waste OS, improves the fire‐retardant properties of asphalt while retaining the mechanical properties of the modified asphalt binder, and provides a model for developing sustainable fire‐retardant asphalt in coastal areas.

Nonlinear Analysis of Bearing Characteristics of Stiffened Deep Cement Mixing Piles under Vertical Loading

Stiffened deep cement mixing (SDCM) piles are composite piles that combine the advantages of single large-diameter deep cement mixing (DCM) and precast concrete piles. They comprise precast concrete piles as the core and cast-in-place DCM piles as the outer layer. This study evaluates the bearing characteristics of SDCM piles under vertical loading. The composite modulus of elasticity of SDCM piles is first introduced and determined using the area-weighted average method. Then, the reliability of the proposed method is described by comparing the calculated results with the findings of the existing literature. Furthermore, a nonlinear simplified analysis method based on the load transfer method is proposed for vertical bearing characteristics of equal- and short-core SDCM piles under vertical loading. This method is developed by the finite difference method. The accuracy of the simplified method is validated by comparing its results with those from existing tests, theoretical analysis, and finite element simulations. The results of their study indicated that the area-weighted average method calculates the composite modulus of elasticity of the composite pile section of the SDCM piles with an error below 0.5% compared to the analytical method. This finding represents sufficient accuracy. The simplified calculation method established in this study is computationally stable. When the iteration factor is set to 10−6, as the number of discrete nodes n on the pile increases, the calculation results are stable with a good convergence when n > 30. The vertical bearing capacity and pile top stiffness of SDCM piles increased with the length of the core piles. There was a reasonable core-to-length ratio for SDCM piles in specific scenarios. An excessively long DCM pile section made its lower part force-free for a given length of core piles. The appropriate length of core piles should be determined in actual projects to avoid unnecessary material waste. An optimum ratio of core piles for SDCM piles was determined. Beyond this optimal value, an increase in the ratio of core piles controlled the pile settlement in a limited manner.

Effect of stable-structural 3D woven preform on tensile and flexural properties of carbon fiber/epoxy composites

The geometry of yarns effect the structural stability of 3D woven preform, which influence the mechanical properties of carbon fiber/epoxy composites. To investigate the effect of stable-structural preform on the elastic properties of 3D woven composites, the factors that caused the unstable structure of preform were discussed, and comparative study was conducted. The geometric models of yarn cross-section and preform were established to discuss the stability. The results showed that increasing the opening angle of warp yarns and the elongation of yarn outer contour can improve the stability of preform. The tensile and bending tests of 3DLAC and 3DBAC with stable and unstable structural preform were conducted. The results showed that the tensile and flexural elastic moduli were inversely proportional to the curvature of load-bearing yarns, and the elastic modulus of composites with stable-structural preform can increase by 9%–13%. The redistribution of internal stress in composites was macroscopically manifested as stable changes in experimental process. 3D woven composites with stable-structural preform showed the regular fracture cross-section, and fiber fracture and interface adhesion effect were the main failure mode in tensile tests, and fiber fracture on the compression surface and matrix cracking were the main failure modes in bending tests.

Indentation of sandwich beams: Comparison of Vlasov, Winkler, and shear theories with composite surfaces reinforced by CNTs and ANN model

The use of sandwich structures has spread to a wide range of fields today. As a result of their thin top and low stiffness, sandwich beams are very susceptible to local loads. One practical solution to increase the sandwich structure's indentation resistance is to add bending strength to the top. The structural properties of carbon nanotubes make them well-suited for use in polymer matrixes; their addition improves the attributes of polymers. Experimental and theoretical investigations of the sandwich structure's indentation behavior are presented in this article. As well, simulations of sandwich structures are conducted using Abaqus software. A tensile test of composite samples and Mori Tanaka's theory were used to determine the elastic modulus of epoxy resin reinforced with carbon nanotubes at different mass percentages. The elastic modulus of composites can be improved by adding carbon nanotubes up to 0.3 % by mass while the mechanical properties are reduced when more than 0.3 % of carbon nanotubes were added. Finally, the analytical solution and Abaqus modeling results for the indentation of the sandwich structure were compared with the results obtained from the experimental tests. A machine learning model is proposed for prediction of sandwich beams deflection. The results of the predictions were phenomenal, with MAE of less than 2 %. The computational costs have been compared with the experimental results, and the machine learning method is very efficient.

Effect of silanization of poly (urea-formaldehyde) microcapsules on the flexural strength and self-healing efficiency of an experimental self-healing dental resin composite (An in-vitro study)

ObjectivesThis study investigated the impact of using γ-methacryloxypropyl trimethoxy silane (MPS) for surface silanization of poly (urea-formaldehyde) (PUF) microcapsules which enclose a healing liquid of “triethylene glycol dimethacrylate (TEGDMA) and N,N dihydroxyethyl-p-toluidine (DHEPT)” on some mechanical properties of an experimental dental composite as well as its self-healing efficiency. MethodsSynthesis of PUF microcapsules was done via in situ polymerization, followed by silanization with MPS silane. Silanized and non-silanized microcapsules were incorporated into a composite containing 30% polymer matrix and 70% fillers at different weight percentages (0%, 5%, 7.5% and 10%). The composite strength and elastic modulus were evaluated by Flexural testing. Fracture toughness KIc and self-healing efficiency were assessed by utilizing the “single edge notched beam” method. ResultsFlexural strength of all groups containing silanized microcapsules was non-significantly different from control group without microcapsules. However, in contrast to control group, all groups containing non-silanized microcapsules displayed considerably decreased flexural strength. Adding silanized and non-silanized microcapsules didn't show a significant change in the KIc-virgin. The silanized microcapsules' groups achieved a self-healing efficiency of about 49–77% recovery in KIc-virgin compared to 38–69% for their non-silanized counterparts. SignificanceIn order to increase the interfacial adhesion with the polymer matrix, improve the mechanical properties, and increase the efficiency of self-healing of dental resin composite, PUF microcapsules were silanized for the first time in the dental field using MPS silane. This innovative silanized microcapsule-containing self-healing composite may hold promise for repairing the damage caused by restorative cracks and extending their service life.

Assessment of Hydrothermal Treatment Effects on Coir Fibers for Incorporation into Polyurethane Matrix Biocomposites Derived from Castor Oil.

The incorporation of natural lignocellulosic fibers as reinforcements in polymer composites has witnessed significant growth due to their biodegradability, cost-effectiveness, and mechanical properties. This study aims to evaluate castor-oil-based polyurethane (COPU), incorporating different contents of coconut coir fibers, 5, 10, and 15 wt%. The investigation includes analysis of the physical, mechanical, and microstructural properties of these composites. Additionally, this study evaluates the influence of hydrothermal treatment on the fibers, conducted at 120 °C and 98 kPa for 30 min, on the biocomposites' properties. Both coir fibers (CFs) and hydrothermal-treated coir fibers (HTCFs) were subjected to comprehensive characterization, including lignocellulosic composition analysis, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The biocomposites were subjected to water absorption analysis, bending tests, XRD, SEM, FTIR, and TGA. The results indicate that the 30 min hydrothermal treatment reduces the extractive content, enhancing the interfacial adhesion between the fiber and the matrix, as evidenced by SEM. Notably, the composite containing 5 wt% CF exhibits a reduced water absorption, approaching the level observed in pure COPU. The inclusion of 15 wt% HTCF results in a remarkable improvement in the composite's flexural strength (100%), elastic modulus (98%), and toughness (280%) compared to neat COPU. TGA highlights that incorporating CFs into the COPU matrix enhances the material's thermal stability, allowing it to withstand temperatures of up to 500 °C. These findings underscore the potential of CFs as a ductile, lightweight, and cost-effective reinforcement in COPU matrix biocomposites, particularly for engineering applications.

Microstructure evolution and mechanical properties of TiB2/18Ni300 composite material produced by laser additive manufacturing

As a reinforcing phase, TiB2 exhibits exceptional wettability and stability when mixed with steel matrices, making it an ideal reinforcement for steel matrix composites. In this paper, we add TiB2 for additive manufacturing of 18Ni300 steel for weight reduction and reinforcement. TiB2 reinforced 18Ni300 matrix composites were prepared by laser cladding. SEM, EDS, and XRD were used to observe the joints' interface and fracture characteristics and analyse the substance composition. Tissue analysis was then performed using EBSD and TEM. According to the TEM and XRD results, there is a martensite structure within the cell, and the cell boundary is an austenite structure. After adding TiB2, a reinforcing phase ((Mo, Fe)3B2) is distributed at the boundary of the cell structure. The high hardness of boride increases the microhardness of the composite material. The yield strength, modulus, and elongation of the samples prepared with 18Ni300 powder are lower than that of forged 18Ni300, but the tensile strength reaches 1134 MPa. The addition of TiB2 increases the composite material's yield strength and elastic modulus significantly. This strengthening technique, which employs the addition of ceramic particles to martensitic steel, is currently not widely used. This experiment provides a theoretical basis and process reference for preparing high-stiffness and lightweight ceramic particle reinforced metal matrix composites.

Experimental assessment on the size effects of square concrete-filled steel tubular columns under axial compression

In this study, eight specimens with the sectional widths (B) of 200–1000 mm and the width-to-steel tube thickness ratios (B/t) of 40 and 50 were tested to failure under axial compression to investigate the size effects of square concrete-filled steel tubular (CFST) short columns, specifically those on the failure mode, composite elastic modulus, peak axial strain, peak axial stress, ductility index, strength index, and stress development. The test results indicate that the peak axial stress, ductility index, and strength index decrease with the increasing specimen size, while the failure mode and composite elastic modulus maintain relatively steady. Under the peak axial load, the longitudinal to yield stress ratio of steel tubes increases with the increasing specimen size, while the trend of transverse to yield stress ratio is opposite. The size effect on the transverse stress in the steel tube reduces the tube confinement effect, thus degrades the compressive strength of the core concrete. Compared to the test results, both the EC4 and the GB50936 codes are unconservative in predicting the strength of large square CFST columns. Therefore, a model considering the ratio of width to thickness (B/t) and specimen size is proposed to evaluate the axial bearing capacity of square CFST short columns.

Effect of okra bast fillers on biodegradation properties of poly(vinyl alcohol) composites.

This paper focuses on the effect of okra bast fillers on biodegradation of poly(vinyl alcohol) composites. Fibers were obtained from okra plant stems via biological degumming and subjected to different chemical treatments such as scouring, alkalizing, maleic anhydride treatment, and vinyl acetate grafting. The fibers were ground and PVA-okra bast filler composites were produced at 20 wt% fiber load via the solution casting method. The obtained composites were tested in terms of mechanical properties and exposed to biodegradation in soil. Effects of okra bast filler addition and chemical treatments on changes in mass, breaking strength, elasticity modulus, and breaking elongation of composites upon soil biodegradation were determined. The composites can be considered for utilization in packaging and agricultural applications.

Calculation method of elastic modulus for carbon fiber-reinforced plastics considering inhomogeneous interphase

Abstract The characteristic of interphase has a significant influence on the macroscopic performance of carbon fiber-reinforced plastics (CFRP). To investigate the effect of interphase on composite elastic modulus, a representative volume element (RVE) of unidirectional CFRP with inhomogeneous interphase was established. Based on the bridging model, a theoretical calculation method of composite elastic modulus was given. The elastic modulus of T300/BSL914C composites was obtained by the theoretical method. Results are in good agreement with the finite element method and experimental data. Four types of interphase models were given including inhomogeneous transversely isotropic, inhomogeneous isotropic, homogeneous transversely isotropic, and homogeneous isotropic. The results demonstrate that interphase type has an influence on the prediction of CFRP composites’ elastic modulus. With the increase of thickness, the prediction error of elastic modulus caused by interphase type increases rapidly. Furthermore, the relationship between composite elastic modulus and interphase thickness and stiffness is analyzed. With the increase in thickness, the changes in shear modulus G 12 and Poisson’s ratio ν23 are more evident than in other elastic properties, and with the enhancement of interphase stiffness, the increase of G 12 is the most significant.

Effect of Fiber Length and Orientation Distribution on the Elastic Modulus in Needle Punched Carbon Epoxy Composites

This paper presents the application of Eshelby-Mori-Tanaka-based micromechanical models for the properties prediction of misoriented carbon fiber composites. Fiber orientation and length distribution are used in property prediction. Empirical models, which capture the distribution of fiber orientation and fiber length in each direction are used in this study. Carbon epoxy composites, made from needle-punched carbon felt, are used in the paper. Fiber orientation and length distributions are determined for this composite. The empirical model was calibrated with the data obtained from needle-punched carbon epoxy composites. The effect of orientation and aspect ratio on the elastic modulus of composites is studied in this study. The prediction has been validated through the experimental results.

Size effect of circular concrete‐filled stainless steel tubular short columns under axial compression

SummaryConcrete‐filled stainless steel tube (CFSST) members combine the advantages of stainless steel materials and concrete‐filled steel tube (CFST) members. Therefore, it has a broad range of applications than CFST members in the marine environment and other scenarios requiring great durability and corrosion resistance. However, there are limited researches on the large‐sized CFSST members. In this paper, 30 circular CFSST members with varying steel ratios (3.7% ≤ α ≤ 10.3%), diameters (500 mm ≤ D ≤ 900 mm), and strength of concrete ( = 40 MPa, 50 MPa) are studied on the size effect under axial compression. For peak axial stress, peak axial strain, and composite elastic modulus, size effects are investigated. According to the results, the peak axial stress and peak axial strain of the members increase with the increase in diameter. The modulus of composite elasticity essentially stays constant as the diameter increases, showing that there is no obvious size effect on the composite elastic modulus. The size effect of peak axial stress and peak axial strain is influenced by the steel ratio. Increasing the steel ratio tended to decrease the size effect. According to the generated data, it was found that the current codes of Chinese and European underestimate the ultimate bearing capacity of CFSST short columns significantly. To this end, the resistances of the large‐sized austenitic CFSST columns with a low steel ratio are well predicted by the proposed design model after being modified, based on GB 50936‐2014 and EN 1994‐1‐1 design codes.

Behaviour of axially compressed CTHST stub columns with inner spiral stirrup

In this paper, a new type of concrete-filled thin-walled high-strength steel tube (CTHST) columns with inner spiral stirrup is proposed. This new type of columns provides dual constraints to the concrete core by both outer steel tube and inner spiral stirrup. To explore the structural performance of this new type of composite members, a pilot study into stub columns under axial compression was carried out. A total of 16 axially compressed specimens, 8 in circular section and 8 in square section, were tested with the various volumetric stirrup ratio (ρ, from 0 to 2.4 %) and yield strength of steel tube (fyt, 571.2 MPa and 648.9 MPa). The experimental results show that, the inner spiral stirrup has little impact on the overall failure pattern of each component of the specimens, but controls the horizontal angle of the failure plane, and the capacity, composite elastic modulus and ductility coefficient of the specimens increase as ρ and fyt increase. In addition, a nonlinear finite element (FE) model was established, and the representative mechanism of axially compressed CTHST stub columns with inner spiral stirrup under different ρ was further studied by the verified FE model. Finally, a calculation method to predict the capacity of the new composite members was developed, which considers the strength improvement of stirrup confined concrete. This method provided an accurate prediction of the capacity of axially compressed CTHST stub columns with inner spiral stirrup.

Structural, physicochemical and biodegradable properties of composite plastics prepared with polyvinyl alcohol (PVA), OSA potato starch and gliadin

Biodegradable plastics have become a good substitute for traditional plastics. In this study, the ternary plastics were prepared by the solvent casting method using different proportions of octenyl succinic anhydride (OSA) esterified potato starch, gliadin and polyvinyl alcohol (PVA), and their structural, physicochemical and degradable properties were characterized. The results showed that composite plastic's elastic modulus (EM), water resistance, and degradability were higher than pure PVA. When the ratio of OSA potato starch to gliadin was 1:1 and replaced PVA was 25%, the compatibility of composite plastic was the best. When PVA accounts for 75% of the total plastic composition, Tm, ΔHc and ΔHm of composite plastics were larger than pure PVA plastics. Therefore, the biodegradability of PVA plastics can be improved by adding OSA potato starch and gliadin, thus providing effective plastic properties as food packaging materials.

Size effect of square concrete-filled stainless steel tubular short columns under axial compression

Concrete-filled stainless steel tube (CFSST) members combine the advantages of stainless steel materials and concrete-filled steel tube (CFST) members. Therefore, it has a broad range of applications than CFST members in the marine environment and other scenarios requiring great durability and corrosion resistance. However, there are limited researches on the large-size CFSST members. In this paper, 40 square CFSST members with varying steel ratios (4 % ≤α≤ 10 %), widths (500 mm ≤B≤ 900 mm) and strength of concrete (fcu = 40 MPa, 50 MPa) are studied on the size effect under axial compression. The size effect on the peak axial stress, peak axial strain, composite elastic modulus and ductility coefficient are investigated. Then this paper adopted the two-way analysis of variance test (ANOVA) to analyze the data. According to the results, the peak axial strain, composite elastic modulus and ductility coefficient have size effect, but the size effect in peak axial stress does not significant. It was found that the steel ratio will also affect the size effect of CFSST members, and the size effect decreases with the increase of steel ratio. Compared with the current CFST codes, the size effect coefficient included steel ratio is introduced can better predict the ultimate bearing capacity of square CFSST short columns with low steel ratio of range of 4–10 %.

The influence of SAP particle size and extra water on the dynamic mechanical behavior of SAP-modified cement-based composites

Superabsorbent polymers (SAP)-modified cement-based composites (abbreviated as composites) have excellent frost resistance, internal curing efficiency, self-sealing and self-healing capacity. However, the effects of SAP particle size and extra water on the dynamic mechanical behavior of composites are still unclear. In this study, the total porosity and macropore (>100 μm) porosity of composites were studied with a mercury intrusion porosimetry test and an image analysis. The influence of SAP particle size and extra water on the quasi-static and dynamic mechanical properties of composites was analyzed. The fracture behavior of composites was investigated based on the fractal dimension and crack morphology. The results reveal that adding extra water can respectively raise the total porosity and macropore porosity by 33 %–39 % and 36 %–50 %, thereby declining the compressive strength and elastic modulus of composites under quasi-static and dynamic compression. The rise of strain rate from 63 s−1 to 102 s−1 elevates the dynamic compressive strength, elastic modulus, and fracture degree of composites by 39 %–44 %, 4.9 %–6.0 %, and 5.2 %–7.4 %, respectively. Raising particle size of SAP and adding extra water can raise the dynamic increase factor of compressive strength and elastic modulus. Which originates from the change of crack path, the increase of fracture degree, and the delayed response of strain induced by the rise of total and macropore porosity.

Rheological properties of crosslinked unentangled and entangled Poly(methyl acrylate) nanocomposite networks

This work is designed to explore the effect of entanglements and particle loading on viscoelastic properties of crosslinked polymer nanocomposites. The entangled and unentangled poly(methyl acrylate) composite networks were synthesized and characterized in linear rheology. We found that the elastic moduli and crosslinking degree of entangled composite networks were unaffected with particle loading. For the unentangled composite networks, both elastic moduli and crosslinking degree enhanced with particle loading. The reinforcement factor analyzed with the recovery of modulus after large deformation indicated that entangled composite networks fully recovered their initial moduli, suggesting the high entanglements can sustain large deformation and maintain their initial chain conformation even at high particle loadings. The unentangled networks did not recover their initial storage moduli after large deformation, posing the non-deformability of the highly crosslinked networks.

Mechanical characterization and low-velocity impact behavior of flax woven fabric-reinforced polymer composites

Man–made fibers like carbon or glass are main components for fiber-reinforced polymer composites thanks to their high strength and stiffness values. However, man-made fibers are not eco-friendly and can hardly be recycled in the nature. Using a high amount of man-made fibers threatens our nature and poses a significant risk for the future of world. Natural fiber reinforced composite (NFRC) is considered as a good alternative for traditional composites. Therefore, NFRC has been examined to develop materials, which have comparable mechanical properties with the man-made fiber reinforced composites, for last decades. Although lots of studies were carried out on the mechanics of NFRC, a few of them focused on the structural design of reinforcement and their effects on composites performance. In this study, the number of weft densities of reinforcements were differentiated and their effects on the mechanical properties of composites were investigated. Fabrics were produced from flax yarns and composites were manufactured by vacuum assisted resin infusion molding method. The tensile, compression, shear and impact tests were carried out to characterize the manufactured composites. Results show that while increasing number of weft density of reinforcement improves the tensile and compressive strength of NFRC in the weft direction, the tensile strength and elastic modulus of composites in the warp direction were characterized by the crimp percentage values of warp yarns. Moreover, it was determined that the number of weft density in the reinforcement affect the contact force and energy absorption capacity of NFRC.

Using micro-indentation to determine the elastic modulus of shale laminae and its implication: Cross-scale correlation of elastic modulus of mineral and rock

Lamina is the smallest megascopic layer in a sedimentary sequence. Different laminae are usually distinguished by various mineral compositions and different thicknesses ranging from tens of micrometers to several millimeters, which significantly affects shale deformation and fracture extension during shale gas/oil exploitation. Nevertheless, due to the minute thickness of laminae, it is hardly possible to determine their elastic moduli by traditional standard mechanical methods and detailed mechanical properties of laminae have been rarely reported. In this work, we studied the elastic modulus differences of laminae in continental shale using micro-indentation technique and scanned electronic microscope (SEM) equipped with automatic mineral identification and characterization system (AMICS). The results demonstrate that the elastic moduli of laminae are highly heterogeneous and can be classified into three types: the stiffer layer, the intermediate layer, and the soft layer, corresponding to the pyritic lamina, the sandy lamina, and the organic-rich lamina, respectively. Additionally, the elastic modulus of lamina excellently correlates with mineral compositions, with the weight coefficients of different minerals on the composite elastic modulus of lamina differing greatly. With the combination of the thickness and the elastic modulus of every single lamina within the shale, it is accessible to obtain the elastic modulus of shale by analytical solutions. Therefore, an efficient method is proposed to characterize the cross-scale elastic modulus from nano/submicron mineral to macro rock based on the mineral components and geometric analysis of laminae, which is rapid and economically feasible, particularly helpful when neither sufficient samples nor logging data are available.

Durability of a Glass Fabric-Reinforced Cementitious Matrix Composite under Different Environmental Conditions

The use of fabric-reinforced cementitious matrix (FRCM) composites for strengthening and retrofitting of existing masonry structures is nowadays a well-established practice, due to the speed and ease of application, low invasiveness, and high performance-to-cost ratio. Among different FRCMs, those comprising glass fiber textiles (GFRCM) represent an excellent choice due to the good mechanical properties and low cost of the raw material. However, limited information is available on the effect of environmental conditions on the performance of GFRCM composites and on their long-term behavior. This paper investigates the effect of different environmental conditions on the tensile performance of a GFRCM composite comprised of a cement-based matrix reinforced with an open-mesh alkali-resistant glass textile. Namely, the effect of hygrothermal conditioning, saline environment, alkali environment, freeze-thaw cycles, and dry heat conditioning were considered. After conditioning, specimens were tested using a clamping-grip tensile test configuration and the effect of the various exposure was analyzed comparing the composite tensile strength, ultimate strain, and elastic modulus of conditioned and control specimens. The experimental results show a good performance of the tested GFRCM composite with respect to the conditions considered.