Tensile Mechanical Properties Research Articles

Experimental Study on the Mechanical Properties of Nano-Silicon-Modified Polyurethane Crack Repair Materials

This study aims to solve the problem of dynamic crack repair in concrete. Although conventional polyurethane has good strength, its tensile and shear properties are poor. It was found that nano-silicon had an overall enhancing effect on the mechanical properties of polyurethane; therefore, five sets of tests with different dosages (0%, 2%, 5%, 7.5%, and 10%) were designed. The compressive, tensile, and shear mechanical properties of nano-silicon-modified polyurethanes were tested by compression, tensile, and straight shear tests, and the microscopic appearance of the materials was observed by scanning electron microscopy. The results showed that nano-silicon could enhance the mechanical properties of polyurethane. The best filling effect on polyurethane was achieved at a dosage of 5%, which increased the compressive, tensile, and shear strengths by 29.4%, 257.6%, and 202.1%, respectively, compared with the substrate. The compressive and tensile moduli in the small strain range were enhanced by 268.5% and 511.8%, respectively. After exceeding 5%, the mechanical properties of the materials decreased due to the enhanced nanoparticle agglomeration effect, which led to the appearance of voids inside the materials. The comprehensive analysis shows that nano-silicon can better enhance the mechanical properties of polyurethane with an optimal dosage of 5%, which is stronger relative to other repair materials and does not require time maintenance.

Comparative study of oil palm and nettle fibers reinforced chemically functionalized high‐density polyethylene composites

AbstractThe demand of natural fiber reinforced composites has grown enormously in polymer industries owing to their renewability and sustainability and maintaining their performance and properties. In this investigation, two natural fibers have been considered as a reinforcer to develop chemically functionalized high‐density polyethylene (CF‐HDPE)‐based composites. The total holocellulose content of ~85% and ~65% for nettle fiber (NTF) and oil palm empty fruit bunch fiber (OPF) make them significant for this study. OPF/CF‐HDPE and NTF/CF‐HDPE composites have been developed and characterized to measure their desirable properties. The structural confirmation suggests reinforcement/matrix adhesion through ester and hydrogen bonds between them. NTF/CF‐HDPE and OPF/CF‐HDPE are thermally stable upto 240°C and 250°C, respectively. A significant increment of ~40% and ~64% in tensile strength were observed in addition of OPF and NTF reinforcer in pristine matrix. A similar observation has been shown in flexural strength with improvement of ~58% and ~83% with OPF and NTF as reinforcer. Among all these composite compositions, the 30/70 NTF/CF‐HDPE composite demonstrated the highest tensile and flexural properties values due to higher holocellulose of NTF. This study demonstrates the potential of OPF and NTF reinforcer to develop natural fiber reinforced polymer composites, which helps respective industries to manufactured tailored made products with desirable properties.Highlights OPF/CF‐HDPE and NTF/CF‐HDPE composites are sustainable and low cost. The composite compositions have been developed by extrusion and injection molding. The composite's mechanical (tensile and flexural) properties have been demonstrated. SEM and FTIR characterized the composites for the fiber/matrix adhesion. The composite's thermal stability has been affected by fibers and matrix.

Microstructure, Non-Basal Texture and Strength-Ductility of Extruded Mg-6Bi-3Zn Alloy.

To investigate the influence of Zn-alloying on the microstructure and tensile mechanical properties of Mg-6Bi alloy after hot extrusion, a new ternary Mg-6Bi-3Zn alloy was prepared by extrusion at 300 °C. The microstructures, texture, dynamic precipitates and tensile mechanical behaviors of the extruded alloy were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), electron backscattered diffraction (EBSD) and a material testing machine at room temperature. After extrusion, the Mg-6Bi-3Zn alloy possesses a bimodal microstructure with elongated large unrecrystallized (unDRXed) grains and fine dynamic recrystallized (DRXed) grains. In addition, non-basal <202_1>//ED, <448_3>//ED and <112_1>//ED textures are observed within DRXed grains due to the Zn addition, leading to texture weakening in the extruded Mg-6Bi-3Zn alloy. Zn addition facilitates the dynamic precipitation behavior, leading to a 12.2% area fraction of Mg3Bi2 precipitates with an average size of 39.2 nm. Furthermore, incorporation of Zn atoms in Mg3Bi2 phases and segregation of Zn at the grain boundary are found. The extruded Mg-6Bi-3Zn alloy exhibits a tensile strength of 336 ± 7.1 MPa and a yield strength of 290 ± 5.5 MPa, as well as an elongation of 11.5%. Therefore, Zn addition is beneficial to enhance strength and keep good ductility for the extruded Mg-6Bi-3Zn alloy.

Comparison of iron aluminide Fe3Al with armour steel in ballistic behaviour

Intermetallic aluminide compounds possess several potential advantages compared to alloyed steels, like enhanced oxidation resistance, lower density and the omittance of critical raw materials. Iron aluminides, compared to other transition metal–aluminides of TM3-Al type, although having a higher density compared to titan-aluminides, have a lower density compared to nickel-aluminides, but also a higher ductility than both alternatives, making this material potentially effective in ballistic protection application. Density–wise, this material may be a worthy alternative to armour steels, which was the aim of this study. Two materials, Fe3Al intermetallic compound (F3A-C) and Armox 500 armour steel were ballistically tested against tungsten-carbide (WC) armour-piercing ammunition, in accordance with STANAG 4569. After ballistic testing, microhardness and metallographic testing were performed, revealing differences in strain hardening, crack propagation mode and exit hole morphology. F3A-C ballistic resistance is similar to that of armour steel, in spite of the lower tensile and impact mechanical properties, relying on a considerably higher strain hardening rate, thermal properties and a lower density.

Effect of alloying element content, temperature, and strain rate on the mechanical behavior of NbTiZrMoV high entropy alloy: A molecular dynamics study

High entropy alloys (HEAs) have drawn attention among researchers due to their excellent mechanical properties at low and high temperatures, which pave the way for their numerous applications in various sectors. In this study, we have investigated the effect of temperature and strain rate on the mechanical properties of single crystal equimolar NbTiZrMoV alloy, a refractory HEA (RHEA), using molecular dynamics simulation with the help of a newly developed modified embedded atom method (MEAM) potential. Uniaxial tensile simulations were conducted along x-direction at temperatures between 77 K and 600 K, with temperature intervals of 100 K, and at strain rates of 0.001 ps−1, 0.005 ps−1, 0.025 ps−1, and 0.125 ps−1. Stress-strain curves were plotted from the simulation data, and different tensile properties of the alloy were calculated from the graph. This study suggests that the tensile strength and the elastic modulus of the HEA decrease with increasing temperature as the materials become soft at higher temperatures. Strain rate improves the tensile mechanical properties with increasing rate due to the lack of required time for atom rearrangement and dislocation entrapment requiring higher stresses to continue deformation. Ultimately, the tensile characteristics of the HEA are shown to be influenced by the content of alloying elements. Specifically, Mo content has a rising effect, and Nb content is having a reducing impact on the tensile properties of NbTiZrMoV HEA. The study provides insights into the mechanical properties of NbTiZrMoV HEA, which could inform its applications in various sectors due to its promising mechanical features at different temperatures and strain rates.

Modeling and Optimizing the Alkaline Treatment Process to Enhance the Date Palm Fibers’ Tensile Mechanical Properties Using RSM

ABSTRACT This study aims to enhance the mechanical properties of date palm fibers (DPFs) by implementing a targeted treatment technique. The response surface methodology (RSM) is utilized for modeling and optimizing. The study seeks to identify the optimal Alkaline treatment settings for improving the mechanical properties of DPFs by carefully analyzing parameters such as average diameter, time, and NaOH concentration. The analytical results offer valuable insights into the possible use of DPFs in many engineering applications, contributing to the industrial advancement of sustainable and eco-friendly materials. The experimental findings are analyzed using a full-factorial design (43), incorporating analysis of variance and RSM. Combining RSM and desirability function is used to get the best mechanical properties, including stress, strain, and Young’s modulus. The model appropriateness is evaluated by analyzing residual values. The findings suggest that the sodium hydroxide concentration (%NaOH) has the most significant impact on strain (11.63%), stress (12%), and Young’s modulus (11.72%) besides the time t (h) also significantly influences 6.01%, 6.26%, and 5.79% strain, stress, and Young’s modulus, respectively.

Study on the Aging Precipitation Behavior and Kinetics of Al-10.0Zn-3.0Mg-2.8Cu Alloy by Pre-Deformation Treatment.

In this paper, the effect of thermomechanical treatment process on the hardening behavior, grain microstructure, precipitated phase, and tensile mechanical properties of the new high-strength and high-ductility Al-10.0Zn-3.0Mg-2.8Cu alloy was studied, and the optimal thermomechanical treatment process was established. The strengthening and toughening mechanisms were revealed, which provided technical and theoretical guidance for the engineering application of this kind of high strength-ductility aluminum alloy. Al-10.0Zn-3.0Mg-2.8Cu alloy cylindrical parts with external longitudinal reinforcement were prepared by a composite extrusion deformation process (reciprocal upsetting + counter-extrusion) with a true strain up to 2.56, and the organizational evolution of the alloys during the extrusion deformation process and the influence of pre-stretching treatments on the subsequent aging precipitation behaviors and mechanical properties were investigated. The results show that firstly, the large plastic deformation promotes the fragmentation of coarse insoluble phases and the occurrence of dynamic recrystallization, which results in the elongation of the grains along the extrusion direction, and the volume fraction of recrystallization reaches 42.4%. Secondly, the kinetic study showed that the decrease in the activation energy of precipitation increased the nucleation sites, which further promoted the diffuse distribution of the second phase in the alloy and a higher number of nucleation sites, while limiting the coarsening of the precipitated phase. When the amount of pre-deformation was increased from 0% to 2%, the size of the matrix precipitated phase decreased from 5.11 μm to 4.1 μm, and when the amount of pre-deformation was increased from 2% to 7%, the coarsening of the matrix precipitated phase took place, and the size of the phase increased from 4.1 μm to 7.24 μm. The finalized heat treatment process for the deformation of the aluminum alloy tailframe was as follows: solution (475 °C/3 h) + 2% pre-stretching + aging (120 °C/24 h), at which the comprehensive performance of the alloy was optimized, with a tensile strength of 634.2 MPa, a yield strength of 571.0 MPa, and an elongation of 15.2%. The alloy was strengthened by both precipitation strengthening and dislocation strengthening. After 2% pre-stretching, the fracture surface starts to be dominated by dense tough nest structure, and most of them are small tough nests, and small and dense tough nests are the main reason for the increase in alloy toughness after 2% pre-stretching deformation.

Study on the Mechanical Properties of Roots and Friction Characteristics of the Root–Soil Interface of Two Tree Species in the Coastal Region of Southeastern China

The tensile strength of roots and the friction characteristics of the root–soil interface of tree species are the indicators that play a crucial role in understanding the mechanism of soil reinforcement by roots. To calculate the effectiveness of the reinforcement of soil by tree roots based on essential influencing parameters, typical trees in the coastal region of southeastern China selected for this study were subjected to tests of the tensile mechanical properties of their roots, as well as studies on the friction characteristics of the root–soil interface and the microscopic interfaces. The results indicated that in the 1–7 diameter classes, the root tensile strength of both Pinus massoniana and Cunninghamia lanceolata was negatively correlated with the root diameter in accordance with the power function. The root tensile strength of these two trees, however, was positively correlated with the lignin content but negatively correlated with cellulose and hemicellulose contents. The shear strength at the root–soil interface and the vertical load exhibited a constitutive relationship, which followed the Mohr–Coulomb criterion. As the root diameter increased, both the cohesion and the friction coefficients at the root–soil interface gradually increased, but the growth rate stood at around 15%. The cohesion value of the root–soil interface of the two trees decreased linearly with the increase in soil moisture content within the range of 25 to 45%. At the microinterface, the root surface of C. lanceolata exhibited concave grooves and convex ridges that extended along the axial direction of roots, with their height differences increasing with the enlargement of the root diameter. The rough surface of P. massoniana roots had areas composed of polygonal meshes, with an increase observed in the mesh density with increasing root diameter.

Effect of nanofibril cellulose empty fruit bunch‐reinforced thermoplastic polyurethane nanocomposites on tensile and dynamic mechanical properties for flexible substrates

Effect of nanofibril cellulose empty fruit bunch‐reinforced thermoplastic polyurethane nanocomposites on tensile and dynamic mechanical properties for flexible substrates

Interatomic potential of the MgAl2O4/Al interface and its application in strengthening mechanisms

MgAl2O4 ceramics possess outstanding mechanical properties, making them promising for use as reinforcing or interfacial modulating phase in Al-based metal composites. The challenge lies in the insufficient interatomic potential parameters to accurately characterize the MgAl2O4/Al interfacial interactions, which hampers a detailed understanding of the interfacial strengthening mechanisms at the atomic level. Since the pair potential satisfies the requirements for computational efficiency and accuracy, it has been widely used for investigating the interfacial properties of composite materials. In this study, the interatomic potential parameters for Al–Mg and Al–Al bonds were derived from Buckingham potential, while those for Al–O bonds were obtained from Morse potential via first principles calculations. The uniaxial tensile mechanical properties and interface-dislocation strengthening mechanisms of MgAl2O4/Al interface configuration were explored through molecular dynamics simulations. The analyses reveal that the strength enhancement of the MgAl2O4/Al interface is due to the generation of a large number of immovable 1/6<110> stair-rod dislocations therein. The thickness of MgAl2O4 layer significantly influences the mechanical properties. Below a thickness of 20 Å, the presence of movable dislocations reduces the strengthening effect. Conversely, increasing the thickness of MgAl2O4 encourages the emergence of immovable dislocations and increases the flow stress, while the corresponding yield strain decreases. These insights open up new prospects in the development of aluminum metal matrix composites with enhanced performance.

Preparation of an Antibacterial Branched Polyamide 6 via Hydrolytic Ring-Opening Co-Polymerization of ε-Caprolactam and Lysine Derivative.

In this study, we successfully realized the hydrolytic ring-opening co-polymerization of ε-caprolactam (CPL) and lysine derivative. A novel antibacterial modified polyamide 6 with a branched structure was obtained after the quaternization of the co-polymers. The co-polymers exhibited a significant increase in zero shear viscosity, melt index and storage modulus at the low frequency region. The quaternized co-polymers displayed thermal properties different from pure PA6 and good mechanical (tensile) properties. The antibacterial activity of the quaternized co-polymers depends on the quaternary ammonium groups' incorporated content. At 6.2 mol% incorporation of quaternary ammonium groups, the strong antibacterial activity has been introduced to the co-polymers. As the quaternary ammonium groups approached 10.1 mol%, the antibacterial polymers demonstrated nearly complete killing of Staphylococcus aureus (Gram positive) and Escherichia coli (Gram negative). The above research results provided a new approach for the study of high-performance nylon.

Study on the influence of carbon nanotube modification on the mechanical and magnetic properties of chloroprene rubber‐based magnetorheological elastomers

AbstractThis study explores the mechanical and magnetic properties of magnetorheological elastomers (MREs) based on chloroprene rubber, enhanced with carbonyl iron powder (CIP) as the primary filler. Carbon black serves as the primary reinforcing filler, with multi‐walled carbon nanotubes (CNTs) used as a secondary filler to strengthen the rubber matrix. The primary objective of this research is to examine the effects of the mixture of iron powder with reinforcing fillers and the interaction of these fillers with the rubber matrix on the mechanical and magnetomechanical performance of MREs. CNTs, tubular nanoscale carbon molecules, significantly enhance the tensile strength and fatigue resistance when combined with the MRE matrix. During mixing, CNTs form a network structure within the MRE matrix, promoting the dissipation of accumulated heat and reducing thermal fatigue loss. The addition of 20 parts of CNTs to the CR matrix significantly improved the tensile mechanical properties, with the 100% set elongation stress increasing by up to 260% and the magnetic responsiveness increasing by 30.6%. The addition of 10 parts of carboxylated CNTs most notably enhanced the magnetorheological effect, increasing the magnetic stress relaxation rate by 78%. These enhanced properties enable MREs to provide better vibration control and comfort in automotive suspension systems, improve energy absorption and damping effects in industrial damping systems, and enhance durability and sealing performance in sealant applications.Highlights Carbonyl iron powder, carbon black, and carbon nanotubes (CNTs) were used as fillers to strengthen the chloroprene (CR) matrix magnetorheological elastomers (MREs). CNTs formed a network structure, promoting the dissipation of accumulated heat and reducing thermal fatigue loss. The tensile mechanical property of MRE with 20 parts of CNTs has been significantly improved, with an increasing magnetic responsiveness of 30.6%. Magnetorheological effect of MRE with 10 parts of CNTs has notably enhanced, with the magnetic stress relaxation rate of 78%.

Nanocomposites of polyhydroxyurethane with Fe3O4 nanoparticles: Synthesis, shape memory and photothermal properties

AbstractThe nanocomposites of ferroferric oxide (Fe3O4) with polyhydroxyurethane (PHU) were fabricated via a physical mixing approach. This process involved grafting poly(N‐vinyl pyrrolidone) (PVPy) chains onto the surfaces of Fe3O4 nanoparticles via surface‐initiated living radical polymerization. The PVPy‐grafted Fe3O4 nanoparticles were directly incorporated into the precursors of PHUs [i.e., bis(cyclic carbonate) and a trifunctional amine] and the mixtures were cured at high temperatures to form organic–inorganic composites. This method ensured that Fe3O4 nanoparticles were finely dispersed within the PHU matrix through the strong intermolecular hydrogen bonding between PVPy and PHU. Compared to plain PHU network, the nanocomposites had enhanced thermomechanical properties, including higher glass transition temperatures (Tg's) and improved tensile mechanical properties. The inclusion of Fe3O4 nanoparticles also enhanced the shape memory properties of the PHU networks, improving shape recovery rates, fixity of transient shapes, and recovery of the original shapes. In addition, the nanocomposites demonstrated paramagnetic and photothermal properties and the photothermal behavior enabled a non‐contact control of shape recovery.Highlights Poly(N‐vinyl pyrrolidone)‐grafted Fe3O4 nanoparticles were synthesized. Nanocomposites of PHU with Fe3O4 were prepared via a physical blending approach. Incorporation of Fe3O4 resulted in improved thermomechanical properties. The nanocomposites had the photothermal properties.

Advancing sintering and matrix-reinforcement interaction in Al/AlN metal matrix composites through use of novel AlN reinforcement

Demand for energy-efficient transportation has led to increased use of lightweight aluminium alloys due to their exceptional strength-to-weight. Meanwhile, aluminium-based metal matrix composites (MMCs) are being developed to enhance wear resistance and strength. However, traditional ceramic reinforcements often have poor bonding with the matrix, compromising performance. Here, we demonstrate the use of a novel ex-situ AlN reinforcement powder to enhance sintering and interfacial bonding for powder metallurgy preparation of Al/AlN MMCs. We compared two series of Al/AlN MMCs featuring 10 vol.% ex-situ AlN reinforcement, one prepared using commercial AlN powder, and the other using our novel AlN reinforcement prepared by low temperature direct nitridation of Al powder. Metallic Al contained in the synthesized reinforcement significantly improved interfacial adhesion between matrix and reinforcement and enhanced densification during sintering. This resulted in a substantial improvement in tensile mechanical properties, with an 11.5% increase in ultimate tensile strength and almost five-fold improvement in ductility compared to composites prepared using the conventional ceramic AlN reinforcement. This study provides a strategy for powder metallurgy production of advanced Al/AlN MMCs with superior physical and mechanical properties.

Effect of Glycerol and Sisal Nanofiber Content on the Tensile Properties of Corn Starch/Sisal Nanofiber Films.

Currently, petroleum-derived plastics are widely used despite the disadvantage of their long degradation time. Natural polymers, however, can be used as alternatives to overcome this obstacle, particularly cornstarch. The tensile properties of cornstarch films can be improved by adding plant-derived nanofibers. Sisal (Agave sisalana), a very common low-cost species in Brazil, can be used to obtain plant nanofibers. The goal of this study was to obtain sisal nanofibers using low concentrations of sulfuric acid to produce thermoplastic starch nanocomposite films. The films were produced by a casting technique using commercial corn starch, glycerol, and sisal nanofibers, accomplished by acid hydrolysis. The effects of glycerol and sisal nanofiber content on the tensile mechanical properties of the nanocomposites were investigated. Transmission electron microscopy findings demonstrated that the lowest concentration of sulfuric acid produced fibers with nanometric dimensions related to the concentrations used. X-ray diffraction revealed that the untreated fibers and fibers subjected to acid hydrolysis exhibited a crystallinity index of 61.06 and 84.44%, respectively. When the glycerol and nanofiber contents were 28 and 1%, respectively, the tensile stress and elongation were 8.02 MPa and 3.4%. In general, nanocomposites reinforced with sisal nanofibers showed lower tensile stress and higher elongation than matrices without nanofibers did. These results were attributed to the inefficient dispersion of the nanofibers in the polymer matrix. Our findings demonstrate the potential of corn starch nanocomposite films in the packaging industry.

A methodology to evaluate seawater corrosion on quasi-static tensile properties of a structural steel

With the wind turbine industry growing and increasingly turning its focus to the offshore sector, it is important to grasp the challenges that come with it: the logistic challenges related to transport and maintenance, the exposure to wave and wind action and also the vulnerability to corrosion. The marine environment is a complex and aggressively corrosive environment. The S690 steel, as a structural steel of high mechanical strength, offers weight reduction advantages that are of interest to the sector. However, its behaviour in a corrosive medium is still not well known. As such, this work is part of an effort to characterize S690 steel under marine environment conditions. A methodology for inducing accelerated pre-corrosion on quasi-static tensile specimens of S690 steel, while simulating the environment, has been developed and applied. The effect of this pre-corrosion on the tensile mechanical properties is evaluated through testing in accordance with the ASTM E8 standard. It was found that the induced surface pre-corrosion, equivalent to six months of exposure, did not have a significant effect on the investigated mechanical behaviour.

Investigation on the biaxial tensile testing method for metal foil using cruciform specimen

The assessment of mechanical properties of metal foil under complicated stress states poses a considerable challenge, requiring the development of new testing methods and the optimization of new specimen geometry. In this research, the biaxial tensile method and specimen shape were designed and optimized by using simulation and experiment. It is determined that the strain measurement area can be suggested as the central area of 0.6 to 0.8 times the arm width. The influence of different parameters on the tensile results of cruciform specimens was comprehensively evaluated by finite element method and multi-factor analysis. The results indicate that the number of slits markedly impacts the stress–strain uniformity and shear stress in the central region, followed by the slit length. The effect of the arm width and the slit width is comparable, more influential than the corner radius. According to the analyzed results and application requirements, a four-axis independently driven biaxial tensile test machine for small scale samples was fabricated. During the biaxial tension, the center point offset of the specimen remains within ±0.01 mm. The displacement and load synchronization errors do not exceed 0.01 mm and 50 N, respectively, facilitating the precise control of four-axis synchronization. Conclusively, cruciform specimens featuring diverse geometric characteristics were designed for industrial pure titanium, 304 stainless steel, and Inconel 718 superalloy with thickness of less than 0.3 mm. The biaxial tensile tests were performed to delineate the yield loci, revealing notable anisotropy and size effect. The validation confirms the suitability of the testing method and optimized cruciform specimens for conducting biaxial tensile mechanical properties testing on metal foils characterized by diverse types and thicknesses.

Development and mechanical characterization of horse hair with titanium dioxide nanoparticles reinforced polyester composite

This study aims to examine the effects of waste material more especially horse hair as fiber on mechanical and physical properties. Tensile, flexural, impact, and hardness properties of horse hair fiber and titanium dioxide nanoparticles (TiO2 NPs) polyester composite were investigated to determine whether the latter might be used as a new material in various engineering applications for a longer life. To improve the impact resistance of the composite, horse hair fiber is mixed in different ratios with titanium dioxide and polyester as filler. Tensile, flexural, and impact mechanical properties were assessed using the Universal Testing Machine, the Rockwell Hardness Testing Machine, and the Izod Impact Test. Specimens were hand-put up using various fiber weight ratios. The results of this study showed that Specimen 5 showed a tremendous increase in flexural strength (98.87 MPa), tensile strength (91.46 MPa), hardness (115 HV), impact strength (15.98 J m−1), and water uptake (10.18%) as compared to the neat and also with the other Specimens. Scanning electron microscopy (SEM) was used to investigate the fracture surface in more detail in order to search for failure mechanisms and the dispersion of nanoparticles. SEM micrographs verified the uniform dispersion of the nanoparticles. Results suggest that these composites can be used as a material for a variety of applications, including biological claims that they are a practical, durable, and environmentally friendly choice.

Analysis of fracture damage mechanical properties of particle reinforced polymer composite film based on micro-macro finite element method

The particle reinforcement and related effect on fracture damage mechanical properties of polymers have been studied in this paper. Based on the uniaxial tensile test result of SiO2 particle reinforced polyvinylidene fluoride (PVDF) composites, the parameters of macro elastic-plastic finite element model and micro particle reinforced model are obtained. The effects of boundary conditions, shape and size of damage notch on fracture damage mechanical properties of PVDF composites are studied from macroscopic view. The uniaxial tensile mechanical properties and elastic modulus are increased with notch angle (0°, 30°, 60°, 120°). The damage analysis of the micro model shows that the mechanical properties of SiO2/PVDF composites are best when the content of SiO2 is 6%. Debonding between particles and matrix indicates have great effect on crack propagation. The micro-macro finite element model is effective tool to study the damage mechanical properties of particle reinforced polymers.

Tensile properties of helical carbon fiber tows

The carbon fiber used in the load-bearing structural components often exhibits a relatively low toughness and a limited elongation at the point of failure within its carbon fiber tows. To address this challenge, we introduced a bionic helical structure as an innovative alternative to the conventional straight carbon fiber tows, resulting in a novel material characterized by enhanced strength and toughness. Pioneering a theoretical model, we delved into the effects of the helical angle on the tensile mechanical properties of helical carbon fiber tows for the first time. Subsequently, we conducted experimental trials to validate our theoretical findings and identified an optimal range for the helical angle. The optimized helical angle enhances additional lateral interactions, improving the bonding between the fibers and the resin. The characteristics of the helical structure increase the overall fracture elongation of the fiber tows. Tensile tests revealed a remarkable 10.8 % increase in maximum tensile strength and a significant 46 % enhancement in toughness when the tows were fully impregnated with epoxy resin using this optimal helical angle. Incorporating the helical structures at this optimized angle represents a breakthrough in improving the mechanical properties of carbon fiber tows, offering a unique solution to strike a balance between strength and toughness in carbon fiber composites.