Changes In Tensile Properties Research Articles

Study on the UV aging resistance of ZnO‐modified epoxy resin by experiments and MD simulation

AbstractThis study investigates the impact of zinc oxide nanoparticles on epoxy resin systems and the ultraviolet (UV) aging resistance of modified epoxy resin composites using molecular dynamics (MD) simulations and experimental methods. Initially, various epoxy resin cross‐linking models are established through MD simulations to understand the influence of different nano ZnO contents on resin modification, further validated by experiments. Subsequently, the UV radiation resistance of nano ZnO–epoxy resin composites is assessed by subjecting them to high‐intensity UV radiation equivalent to 3 years of natural environmental conditions, analyzing changes in tensile properties, impact performance, hardness, and glass transition temperature of epoxy resin before and after UV radiation exposure. The findings suggest that the addition of nano zinc oxide reduces the impact of UV radiation on epoxy resin, with optimal UV radiation resistance observed at a nano zinc oxide mass fraction of 0.3 wt%.

The microhardness, morphology and tribological property of TC4 subjected to machine hammer peening

Ti alloy has become an indispensable material in harsh working environments due to its excellent wear resistance, corrosion resistance and impact resistance. These environments place stringent requirements on the fatigue life, friction and wear, and surface strength of materials. Therefore, this study aims to deeply explore the surface mechanical properties of Ti-6Al-4V (TC4) alloy after machine hammer peening (MHP) treatment. By conducting experiments on TC4 alloys treated with different hammering energies, the changes in surface hardness, morphology, roughness, tensile properties, and friction properties were analyzed, and the strengthening mechanism of MHP was discussed. Experimental results show that MHP treatment can effectively improve the surface properties of TC4. With the increase of hammer energy, due to the double-sided hammering of the plate, the microhardness first increases, then decreases, and then rises again. The tensile strength and yield strength of the sample increase slightly, but the elongation at break decreases. The surface roughness of the sample increases first and then decreases. Similarly, after MHP treatment, the wear resistance of the samples increased, the friction coefficient decreased, and the wear amount and surface height difference showed a trend of first increasing and then decreasing. The wear mechanism mainly included adhesive wear, abrasive wear and fatigue wear.

Numerical Study of Melt-Spinning Dynamic Parameters and Microstructure Development with Ongoing Crystallization.

In response to an investigation on the paths of changes in the crystallization and radial differences during the forming process of nascent fibers, in this study, we conducted numerical simulation and analyzed the changes in crystallization mechanical parameters and tensile properties through a fluid dynamics two-phase model. The model was based on the melt-spinning method focusing on melt spinning, the environment of POLYFLOW, and the method of joint simulation, coupled with Nakamura crystallization kinetics, including the development of process collaborative parameters, stretch-induced crystallization, viscoelasticity, filament cooling, gravity term, inertia, and air resistance. Finally, for nylon 6 BHS and CN9987 resin spinning, the model successfully predicted the distribution changes in temperature, velocity, strain rate tensor, birefringence, and stress tensor along the axial and radial fibers and obtained the variation pattern of fibers' crystallinity along the entire spinning process under different stretching rates. Furthermore, we also explored the effects of spinning conditions, including inlet flow rate, winding speeds, and the extrusion temperature, on the fibers' crystallization process and obtained the influence rules of different spinning conditions on fiber crystallization. Knowing the paths of changes in mechanical performance can provide important guidance and optimization strategies for the future industrial preparation of high-performance fibers.

Sensitivity Differences in Testing of Polyurethane Condoms’ Lubricant Compatibility

Abstract Over-the-counter (OTC) personal lubricants (PLs) generally have less potent effects on condoms’ mechanical properties than do appropriate positive controls. Therefore, to assess the compatibility of OTC PLs with condoms, a test method must be more sensitive than those employed to capture the effect of a strong positive control. Using various percent compositions of selected common ingredients in commercial PLs, we attempted to differentiate between the sensitivities of different methods for testing lubricant effects on polyurethane (PU) condoms. After discrete applications of each composition, we studied induced stresses and stress-to-strain ratios at various strain rates, and stress reduction at a constant stretch, in PU condom coupons at 37°C. Swelling was studied at room temperature (RmT). Changes in the induced stress and stress-to-strain ratio because of low percent composition of a potent surrogate component were detectable only at low strain rates. A few low percent compositions of potent ingredients – though they induced insignificant changes in the material as detected by tensile testing and did not swell the PU material – noticeably reduced the percent stress at a constant stretch. Slower strain rates in tensile testing were necessary to detect the effects of low potency combinations, whereas stress reduction was the most efficient detector of change at a constant physiologically relevant strain. Absence of swelling and insignificant changes in tensile properties at high strain rates did not guarantee an absence of interactions. Manufacturers now have a more sensitive method for capturing the interactions of PU condoms with OTC PLs, which are generally less potent than appropriate positive controls.

Effects of CuCr1Zr contamination on the tensile properties and microstructure of stainless steel 316L produced via laser powder bed fusion

AbstractCopper contamination has a negative effect on the tensile properties of certain stainless steel grades due to a weakening of grain boundaries via liquid metal embrittlement. This is especially problematic given current trends in laser powder bed fusion (L-PBF) that elevate contamination risks, such as multi-material processing or the use of recycled materials. As such, it is critical to establish composition limits for use in standard specifications. This study investigates the changes in tensile properties and cracking behavior in stainless steel alloy 316L contaminated with copper alloy CuCr1Zr at concentrations of 0–10 particle percent (pt.%) in horizontal, diagonal, and vertical build orientations. It is found that microcracks are already present at 1 pt.% Cu alloy and increase in density with contamination. The cracks are generally vertically oriented along columnar grain boundaries and are associated with high local Cu content, thus exacerbating the anisotropy of the as-built material. The contamination decreases the elastic modulus, yield strength (YS), ultimate tensile strength (UTS), and uniform elongation, eventually transitioning from ductile to brittle fracture modes. The build orientation relative to the tensile loading axis is shown to be a critical design parameter due to the preferential crack initiation and growth direction. The fracture surfaces at 10 pt.% contamination show regularly spaced, smooth brick-like cleavage patterns that correspond to the columnar grain dimensions. Even so, the measured YS and UTS exceeded the ASTM F3184-16 standard for CuCr1Zr contaminations up to 5 pt.%. As a conservative limit, it is proposed that a maximum content of 1 wt% Cu be specified for L-PBF SS316L.

Investigation on the blooming behavior of additives in nitrile butadiene rubber at elevated temperature

AbstractThe degradation of rubber performance in service environments is closely associated with the blooming behavior of additives in the rubber. This study investigates surface precipitates and changes in tensile properties of nitrile butadiene rubber (NBR) after storage at 85°C in air. The morphology, elemental composition, phase composition, and functional groups of the precipitates were analyzed by scanning electron microscopy, energy dispersion spectroscopy, X‐ray diffraction, and fourier transform infrared spectroscopy. Based on the morphology of internal rubber particles and precipitates and variations in the Zn/C mass ratio (ERZn), the reaction between zinc oxide and stearic acid in rubber under long‐term thermal environment was determined. Four stages of blooming for the mixture of zinc oxide and zinc stearate were inferred, and the impact of the blooming on the degradation of tensile properties of NBR was established. A dramatic decrease in the elongation at break (δk) of NBR was correlated with the blooming of zinc stearate and its correspondingly weakened plasticizing effect.Highlights The core‐shell structured mixture of ZnO and Zn(St)2 bloomed onto the surface of nitrile butadiene rubber. The ratio of mass percentages of Zn to C evaluated the blooming process of additives. The migration and blooming process of precipitates were divided into four stages. The decrease in elongation of the rubber was attributed to the blooming of Zn(St)2.

Microstructural Evolution and Tensile Properties of Al-Si Piston Alloys during Long-Term Thermal Exposure

The present study investigated microstructural evolution and changes in tensile properties of an Al-Si piston alloy subjected to thermal exposures at 250 and 350 °C for 150, 300, and 500 h. Microstructural and nanoscale precipitates were characterized using a combination of high-angle annular dark field-scanning transmission electron microscopy (HAADF-STEM) images and scanning electron microscopy (SEM). The tensile testing was performed. The results demonstrated that the thermal exposure induced granulation of the δ-Al3CuNi particles, alongside precipitation of the θ-Al2Cu phase particles and AlCu clusters within the matrix. Specifically, an increase in the size and number density of the θ-Al2Cu phase particles was observed with exposure time at 250 °C. Conversely, at 350 °C, the θ-Al2Cu particles exhibited a gradual increase in size with prolonged thermal exposure, coupled with a decrease in their number density. AlCu clusters precipitated solely at a thermal exposure temperature of 350 °C, with precipitation intensifying over time. Moreover, a decrease in the alloy’s tensile strength and an increase in elongation were noted after thermal exposure. Finally, the present study discussed the precipitation mechanisms of θ-Al2Cu particles and AlCu clusters within the grains, suggesting that the AlCu clusters exerted a more effective strengthening effect compared to the θ-Al2Cu particles.

Enhancing Mechanical Properties of Corn Bran Arabinoxylan Films for Sustainable Food Packaging.

Arabinoxylan (AX)-based films can improve the mechanical characteristics of biodegradable materials when utilized for food packaging. However, the mechanical properties of AX films for food packaging applications require thorough investigation to establish their viability. In this study, AX was extracted from corn bran coproducts of dry-milling (DCB), wet-milling (WCB), and dried distiller's grains with solubles (DDGS) using an acid-alkali method. Packaging materials were produced using these AX extracts, each combined with laccase and sorbitol, forming the basis for three different films. These films were then modified by immersing the surface in a lipase-acetate solution. We evaluated their mechanical characteristics, including thickness, tensile properties, tear resistance, and puncture resistance. The thickness and tensile properties of the modified AX films derived from DCB and DDGS showed significant improvements (p < 0.05) compared to the unmodified AX films. In contrast, the modified AX films from WCB showed no significant changes (p > 0.05) in thickness and tensile properties compared to the unmodified WCB AX films. A significant increase in tear resistance (p < 0.05) was observed in all modified AX films after immersion in the lipase-acetate mixture. While puncture resistance was enhanced in the modified AX films, the improvement was not statistically significant (p > 0.05) compared to the unmodified films. The presence of hydroxyl (OH) and carbonyl (CO) groups on the surfaces of AX films from DCB and DDGS, modified by the lipase-acetate solution, suggests excellent biodegradability properties. The modification process positively affected the AX films, rendering them more bendable, flexible, and resistant to deformation when stretched, compared to the unmodified AX films.

Effect of the ratio of carbon nanotubes and carbon black on the properties of natural rubber

In this experiment, the effect of carbon nanotubes (CNTs) replacing some carbon black (CB) on the properties of natural rubber composites was investigated. 5 phr of CNTs were used to replace part of CB in the ratio of m(CNTs) : m(CB reduction) = 1 : X (X from 1 to 4.5). The properties of the vulcanized rubber such as vulcanization, thermal conductivity, tensile, heat generation and processing were investigated experimentally. The results showed that when the ratio of CNTs/CB(reduction) was 1:1, it could substantially improve the crosslink density of the sample and reduce the vulcanization time, while having better processing safety and having the best thermal conductivity. At this time, 5 phr of CNTs and 40 phr of CB were added to the sample, and the dispersion of CB and CNTs in the sample was studied by CB dispersion tester and rubber processing analyzer. The tensile property change regularity tested by rubber tensile tester matched with the experimental results of CB dispersion tester and rubber processing analyzer. When the ratio of CNTs/CB(reduction) was 1:1, it increased the heat generation of the sample significantly. When the ratio of CNTs/CB(reduction) was 1:3.5, all the properties of the sample were better than those of the 1# sample.

Characterization of the Dimensional Precision, Physical Bonding, and Tensile Performance of 3D-Printed PLA Parts with Different Printing Temperature

In this study, tensile test specimens were fabricated using a material extrusion 3D-printer at various printing temperatures to evaluate the development of physical bonds within the same layer as well as in between previous layers. The tensile test specimens were fabricated using PLA material, with printing temperatures ranging from 180 °C to 260 °C. Experimental investigations were conducted to investigate the dimensional accuracy and physical appearance of the parts across printing temperatures. Uniaxial tensile tests were conducted at a strain rate of 1 mm/min and repeated five times for each variable in accordance with the ASTM D638-14 standard. Results showed that increasing the printing temperatures yielded parts with better tensile properties. An approximate difference of 40% in tensile strength was observed between specimens fabricated under the two most extreme conditions (180 °C and 260 °C). The changes in tensile properties were attributed to bonding mechanisms related to interlayer bonding strength and a reduction in voids within the internal geometry. Analysis of the fracture surface using scanning electron microscopy (SEM) revealed fewer and smaller voids within the internal geometry for parts printed at higher temperature. The percentage area of voids reduced significantly when the printing temperature was increased from 180 °C to 220 °C. The tensile properties continuously improved with the printing temperature, with parts printed at 220 °C exhibiting the highest dimensional accuracy. The findings offer insight into the impact of the printing temperature on both the external physical bonds between printed roads, affecting the physical appearance and dimensional accuracy, and the internal bonds, affecting the tensile properties of the fabricated parts.

Tensile Property Changes in Polyvinyl Alcohol Fiber-Reinforced Engineered Cementitious Composites at Sub-Elevated Temperatures

Tensile Property Changes in Polyvinyl Alcohol Fiber-Reinforced Engineered Cementitious Composites at Sub-Elevated Temperatures

Microstructure and Mechanical Property Stability of Wire Arc Directed Energy Deposition Austenitic Stainless Steels During Thermal Aging at 650°C

Austenitic stainless steels are used in power generation components subjected to elevated temperatures over long service lives. Replacing these components can involve lengthy lead times and deteriorate the robustness of the energy infrastructure. Wire arc directed energy deposition (WA-DED) has the potential to enable rapid manufacturing of replacement parts, but the long-term stability of microstructures and mechanical properties produced by WA-DED is not well understood. In this work, we explore the influence of aging at 650°C for 1000 h on the formation of embrittling phases, such as sigma (σ), in the commercially available austenitic stainless steel wire feedstocks 316L, 316LSi, 316H and 16-8-2. All WA-DED samples formed secondary phases at grain boundaries (likely σ, possibly other phases as well), but these phases caused negligible changes in tensile properties in 316L, 316LSi and 316H. Samples of 16-8-2 formed significant amounts of ferrite and/or martensite after aging, which increased tensile strength but reduced ductility when tested at room temperature. This work demonstrates the need to design feedstock compositions that are stable with respect to ferrite and/or martensite formation, in addition to phases typically associated with embrittlement, to ensure microstructure and mechanical property stability for high-temperature applications with long service lives.

Influence of moisture absorption on tensile and compressive properties of natural fiber-reinforced thermoplastic composites

ABSTRACT The present research is aimed at examining the changes in tensile and compressive properties of natural fiber-reinforced composites (NFRC) exposed to various humidity conditions; this is due to the fact that moisture content (MC) in fibers is generally assumed to be detrimental to composite performance. It was found that once moisture is exposed, compressive strength and strain of specimens would be higher than those of tensile, whereas modulus of elasticity would be lower. Due to increasing moisture content, although elongation in all tests was enhanced, tensile and compressive strength declined by 15% and modulus of elasticity decreased by 20%. In addition, Poisson’s ratio for both compressive and tensile properties was nearly identical (0.33) in distinct moisture content. A new understanding of moisture’s effects on mechanical behavior is presented in this study by finding an optimum point for exposing moisture to increase compressive and tensile strength.

Study on the influence of oxygen content evolution on the mechanical properties of tantalum powder fabricated by laser powder bed fusion

In this work, the influence of reuse times on the properties of tantalum powder and its laser powder bed fusion (LPBF) product was investigated. For this purpose, a batch of tantalum powder was reused up to 16 times, and the particle size distribution, flowability, surface topography, and other characteristics of the powder were studied after different reuse times. The mechanical properties of the finished product samples were also tested. Results from the powder reuse showed that the particle size distribution of tantalum powder changed from 30.1 μm to 33.8 μm, and the oxygen content increased from 310 ppm to 450 ppm. The density and fracture strain of tensile specimens decreased from 16.57 g/cm3 to 16.48 g/cm3 and from 37.9% to 11.6%, respectively. The ultimate tensile strength and microhardness decreased after reaching a peak, ranging from 504 MPa to 614 MPa, and 227 HV to 245 HV, respectively. In addition, it was found that the oxides were mainly tantalum pentoxide, along with monovalent and bivalent oxides. The change in tensile properties was likely related to the interstitial solution of oxygen atoms. This study provides a reference for the reusability of LPBF tantalum powder.

Wood decay fungi show enhanced biodeterioration of low-density polyethylene in the absence of wood in culture media.

The involvement of microorganisms in low-density polyethylene (LDPE) degradation is widely studied across the globe. Even though soil, landfills, and garbage dumps are reported to be promising niches for such organisms, recently the involvement of wood decay fungi in polyethylene degradation is highlighted. In light of this, 50 fungal samples isolated from decaying hardwoods were assessed for their wood degradation ability and for their depolymerization enzymatic activities. For the LDPE deterioration assay, 22 fungal isolates having wood decay ability and de-polymerization enzymatic activities were selected. Fungal cultures with LDPE sheets (2 cm x 10 cm x 37.5 μm) were incubated in the presence and in the absence of wood as the carbon source (C) for 45 days. Degradation was measured by weight loss, changes in tensile properties, reduction in contact angle, changes of functional groups in Fourier-transform infrared spectroscopy, Scanning electron microscopic imaging, and CO2 evolution by strum test. Among the isolates incubated in the absence of wood, Phlebiopsis flavidoalba out-performed the other fungal species showing the highest percentage of weight reduction (23.68 ± 0.34%), and the lowest contact angle (64.28° ± 5.01). Biodegradation of LDPE by P. flavidoalba was further supported by 46.79 ± 0.67% of the mass loss, and 3.07 ± 0.13% of CO2 emission (mg/L) in the strum test. The most striking feature of the experiment was that all the isolates showed elevated degradation of LDPE in the absence of wood than that in the presence of wood. It is clear that in the absence of a preferred C source, wood decay fungi thrive to utilize any available C source (LDPE in this case) showing the metabolic adaptability of fungi to survive under stressful conditions. A potential mechanism for LDPE degradation is also proposed.

Effect of thermal ageing on electrical, mechanical properties of glass fiber reinforced polymer and its impact on service life

The mechanical and electrical properties of polymer composites often degrade due to environmental factors and shorten their service life. This article presents the effect of high temperatures on the mechanical and electrical characteristics of glass fiber reinforced composites and from the measurements, an attempt is made to predict the service life. Electrical conductivity, impedance and resistance are studied with a short-term temperature effect at 30, 60, 120, and 180 °C. The effect of temperature exposure at 120 and 160 °C for 1000, 2000, and 3000 h has been investigated to assess the changes in flexural, compressive, and tensile properties and for prediction of service life. Morphological studies are carried out to support some of the experimental results. The mechanical properties of composites are observed to deteriorate with the duration of aging. Flexural, tensile, and compressive strengths reveal a reduction of 8, 10, and 9%, after aging at 3000 h at 160 °C. The tensile strength and tensile modulus at 120 °C aged for 3000 h exhibit minimal changes as compared to unaged composites. However, with an increase in temperature to 160 °C, there is a reduction in tensile strength and modulus of composites by less than 10%, and 6% compared to composites with nanofillers. The variations in compression strength at 120 and 160 °C is not significant. Based on the reduction of tensile strength with temperature, the service life of composites has been estimated. For a predicted service life of 20 years, composites with nanofillers would be able to retain tensile strength of 90% of tensile strength.

Effect of Sewing Thread Properties on Seam Performance of Woven Fabrics

This paper aims to investigate the influence of sewing thread properties, sewing process and repeated washing cycles on the strength reduction of sewing threads and seam strength of sewn samples. For this purpose, twenty-four commercial sewing threads with different types and linear densities were selected for the present study. The samples were sewn with specific sewing parameters. Half of the fabric samples were then subjected to 10 washing cycles. After sample preparation, the change in tensile properties after sewing and washing was calculated and the seam strength of the sewn and washed-sewn samples was measured. It was observed that the breaking strength of each parent thread was significantly higher than its corresponding sewn and washed-sewn thread strength. Considering the strength loss after sewing and after washing, it was found that, among the different types of sewing threads, the samples sewn with core-spun threads showed lower strength loss, while the samples sewn with cotton threads showed the highest loss. Moreover, the values of seam strength after washing are higher for PES-Co core-spun thread and mercerized cotton thread than before washing. However, an opposite trend was observed for the samples sewn with polyester spun and PES-PES core-spun thread. High correlations were observed between the parent thread and the strength of the sewn thread, the strength of the washed-sewn thread and the seam strength before washing.

Effects of stabilising overfeed on the properties of draw textured polyester yarns

This article deals with the effects of stabilising overfeed (SOF) on the physical properties and structure of draw-texturised polyester yarn. Partially oriented (POY) polyester filament yarn is taken as the starting material for the experiment which is undergone texturing treatment with the various levels of SOF percentage (4% to 14%) keeping other texturing parameters constant. Various characteristics and properties of the texturised yarn samples are measured and analysed to find out the effect of the SOF% on the physical properties and structural changes of the resultant yarns. Bulk and physical structure of all textured yarns are measured by taking optical microscopy images. Change in tensile properties are evaluated by using a universal tensile tester. Change in thermal behaviour of the texturized yarns is evaluated by using differential scanning calorimeter. Thermal degradation and stability of the yarns are measured by using a thermo-gravimetric analyser. Change in the crystallinity of the yarn samples is measured by a wide-angle X-ray diffraction instrument.

Solvent transport dynamics and its effect on evolution of mechanical properties of nitrocellulose (NC)-based propellants under hot-air drying process

Appropriate drying process with optimized controlling of drying parameters plays a vital role in the improvement of the quality and performance of propellant products. However, few research on solvent transport dynamics within NC-based propellants was reported, and its effect on the evolution of mechanical properties was not interpreted yet. This study is conducted to gain a comprehensive understanding of hot-air drying for NC-based propellants and clarify the effect of temperature on solvent transport behavior and further the change of mechanical properties during drying. The drying kinetic curves show the drying time required is decreased but the steady solvent content is increased and the drying rate is obviously increased with the increase of hot-air temperatures, indicating hot-air temperatures have a significant effect on drying kinetics. A modified drying model was established, and results show it is more appropriate to describe solvent transport behavior within NC-based propellants. Moreover, two linear equations were established to exhibit the relationship between solvent content and its effect on the change of tensile properties, and the decrease of residual solvent content causes an obvious increase of tensile strength and tensile modulus of propellant products, indicating its mechanical properties can be partly improved by adjustment of residual solvent content. The outcomes can be used to clarify solvent transport mechanisms and optimize drying process parameters of double-based gun propellants.

Positive Control(s) in Polyurethane Condom-Lubricant Compatibility Testing

Abstract Despite the proliferation of over-the-counter (OTC) personal lubricants (PLs) in the last two decades, to date, no known positive control has been identified to assess the compatibility of these PLs with polyurethane (PU) condoms. In the absence of suitable positive controls, PU condom compatibility with OTC PLs is assessed using a method built for testing compatibility of latex condoms with PLs. Herein, we attempt to identify a safe-to-handle positive control(s) for determining PU condom-lubricant compatibility. At room temperature (RmT), swelling of and induced stress in PU condom sample coupons were studied at various strain rates after discrete applications of a few ingredients common in commercial PLs. Additionally, stress reduction at a constant stretch was measured at 37°C. At low strain rates, changes in the induced stress and stress-to-strain ratio were detectable because of ingredients, e.g., hydroxy-terminated poly(dimethyl siloxane) of viscosity 25 cSt that caused substantial swelling of the condom materials at RmT, indicating prospective positive controls. At 37 °C, the percent stress reduction in PU samples under constant stretch was significant, with a few PL ingredients that did not significantly swell the PU material at RmT. Ingredients that enable significant stress reduction can serve as positive controls in PU condom-lubricant compatibility testing using the tensile method, provided the strain rate is comparable to the rate of condom-lubricant interaction, as evidenced by swelling study. At RmT, absence of swelling and insignificant changes in tensile properties at high strain rates do not guarantee the absence of interactions. Instead of testing mineral oil on latex condoms, manufacturers may now use a PU condom-specific positive control, when testing compatibility of PU condoms with OTC PLs.