Tear Properties Research Articles

Tearing behaviors of coated fabric inflatable tube

In this paper, the tearing properties of the inflatable tube with coated fabrics were investigated. Firstly, uniaxial tensile, shear, and single-edge notched tests were conducted to obtain the material properties. Then, considering the modified stress field model and bulge effect, a theoretical calculation formula for the critical tearing pressure was proposed. Next, based on finite element method, the macroscopic orthotropic elastic continuum models of the single-edge notched test and pressurized cylinder test were established. In numerical model, when the average stress in the critical distance at the crack tip reached the tensile strength, the tearing began. Then, the critical distance was determined when the critical tearing load of the numerical model was closest to the single-edge notched tests’ result. Based on the numerical simulation of pressurized cylinder test, the critical tearing pressure of inflatable tube was obtained. Finally, the pressurized cylinder test and puncturing test were designed and conducted. In the pressurized cylinder test, when the first yarn at the crack tip broke, the critical tearing pressure and configuration around the crack were obtained. Moreover, the correctness of the critical tearing pressure in theoretical calculation formula and numerical model was verified through pressurized cylinder test. In puncturing test of inflatable tube, there were obvious crack expansion and explosion. Based on the theoretical calculation formula for the critical tearing pressure, the predicted results were consistent with puncturing test's results.

On the role of water in regulating the mechanics of collagen fibers

The mechanical properties of collagen fiber–based materials have garnered considerable attention owing to their application in various hydration environments. Herein, we conducted a comprehensive investigation on the mediatory role of water in the mechanical properties and structure of collagen fibers. Lower hydration levels are conducive to the mechanical strength, particularly the tensile and tear properties, and reduce the softness of collagen fibers as well as the D-period and the lateral spacing between collagen molecules. Atomic force microscopy measurements indicate that lower hydration levels also enhance the roughness, adhesion force and lateral forces between collagen fibers. Theoretical calculations further reveal that the hydration level regulates weaker components of water-mediated interactions, such as electrostatic and van der Waals forces, which dominate the resistance against mechanical shock. Our findings provide valuable insights into the role of water in regulating the mechanical behaviour of collagen fibers, thereby contributing to the development of novel high-performance collagen fiber materials.

Mode III Tear Resistance of Bombyx mori Silk Cocoons.

This paper concerns the tear properties and behavior of Bombyx mori (B. Mori) silk cocoons. The tear resistance of cocoon layers is found to increase progressively from the innermost layer to the outermost layer. Importantly, the increase in tear strength correlates with increased porosity, which itself affects fiber mobility. We propose a microstructural mechanism for tear failure, which begins with fiber stretching and sliding, leading to fiber piling, and eventuating in fiber fracture. The direction of fracture is then deemed to be a function of the orientation of piled fibers, which is influenced by the presence of junctions where fibers cross at different angles and which may then act as nucleating sites for fiber piling. The interfaces between cocoon wall layers in B. mori cocoon walls account for 38% of the total wall tear strength. When comparing the tear energies and densities of B. mori cocoon walls against other materials, we find that the B. mori cocoon walls exhibit a balanced trade-off between tear resistance and lightweightness.

Preliminary evaluation of properties and performance of natural rubber (NR) latex band for microplastic capturing in seawater

Microplastic particles are emerging water-laden waste that cause a worrying concern towards the environment and humans health. Due to its small size and geometry, and uncertain surface properties, the microplastic waste capturing method in water is still evolving. To date, a number of findings report on the emergence of microplastic surface charging, especially when exposed to water environment. In this study, the natural rubber (NR) latex band was utilized to capture the microplastic waste via a surface capturing mechanism. The NR band was produced using a film casting and curing methods. The surface charging mechanism on the NR band was introduced via the usage of high amount of ZDEC accelerator and, periodic stretching and relaxation procedures. In this work, ZDEC was used as an accelerator for the rubber formulation, and surface charge booster for the NR band. The surface charge of the NR band generates electrostatic interaction with the microplastic waste in water. The polypropylene (PP) microplastic was captured via the surface attraction mechanism using the manufactured NR band. Based on FTIR analysis, the presence of PP microplastic can be quantified on the contaminated NR band surface. The NR band shows the improvement in tensile and tear properties and crosslink density, mainly due to high amount of ZDEC used. At ZDEC loading of 20 phr, the NR band recorded the highest surface potential value, and this is owing to the formation of Zn2+ complex ions on its surface. XRF analysis indicates that the increment of Zn content in the NR band with increasing ZDEC content, that suggests the formation of Zn2+ complex ions.

Effects of di- and trifunctional chain extenders on the properties of flexible cold-cure polyurethane foams

In this study, effects of di- and trifunctional chain extenders including ethylene glycol (MEG), ethanolamine (MEA), diethanolamine (DEA), and glycerin (GLY) were investigated. 0.3, 0.6, and 0.9 php (parts per hundred parts of polyol mixture) of the chain extenders were added to the polyol formulation. Then, foam parts were produced by molding. The reaction profile, free rise density (FD), and mechanical properties of the specimens were tested regarding ASTM D7487 test methods. First of all, reaction profiles were affected by the chemical nature of the chain extenders. MEA and DEA which have a primary and secondary amine unit, respectively, accelerated both the polymerization and blow reactions and resulted in faster cream (CT), gel (GT), and end-of-rise time (RT) values. On the other hand, MEG also accelerated GT, but retarded CT. Finally, GLY retarded CT, GT, and RT of foam samples. FD of all samples were almost the same with a slight decrease by increasing the amount of chain extenders. Besides, force-to-crush (FTC) as a measure of closed- or open-cell structure, was investigated. Results showed that incorporating di- and trifunctional chain extenders led to a remarkable increase in FTC values. The influence was more profound with amine-based chain extenders. The effects of chain extenders on the mechanical properties were also studied according to the ASTM D3574. In the compression set test, using difunctional chain extenders up to 0.6 php, improved the performance. But higher amounts reversed the trend. On the other hand, trifunctional chain extenders declined the compression set properties of the foam. The addition of chain extenders dwindled the tensile and tear properties of the foams. However, the reduction was less with difunctional chain extenders.

Enhancement of hydrophobicity in natural rubber vulcanizates using diatomaceous earth

This study discusses an approach that gives the Natural Rubber (NR) vulcanizates an elevated hydrophobic character. The method used a chemically treated filler called diatomaceous earth (DE) to deliver the hydrophobic characteristics to NR. DE has a nanoscale roughness. It was chemically treated with hexadecyltrimethoxy silane to obtain low surface energy. The combination of nanoscale roughness and low surface energy gave superhydrophobic properties to DE. A series of treated-DE was made with varying silane percentages to find an optimum silane to DE ratio to get the maximum possible hydrophobicity. The optimum ratio was recorded as 38% w/w, and the treated DE displayed a superhydrophobic water contact angle (WCA) of 152°. The treated-DE was added to the rubber as a filler during the compounding process. The filler was added in varying amounts of 5 phr, 10 phr, 15 phr, and 20 phr to observe the changes in the hydrophobic property. The wettability and morphology of developed vulcanizates were measured using WCA measurements and scanning electron microscope (SEM) analysis, respectively. NR compounded with 20 phr filler exhibited an enhanced WCA of 136°, compared to the WCA of 92° of the NR vulcanizate with no treated-DE, and displayed improved tensile, and tear properties.

INFLUENCES OF ALKALI PRETREATMENT ON LYOCELL WOVEN FABRIC PROPERTIES AFTER ABRASION

In this study, alkali pretreatment in various concentrations were applied to Lyocell woven fabrics to decrease the fibrillation tendency of fibers and the influences of alkali pretreatment on tensile and tearing properties of Lyocell fabrics after abrasion were investigated. Alkali pretreatment reduced fibrillation of Lyocell fibers. However, fabric shrinkage occurred because of the increased volume and damaged twisted structure of yarns due to the lateral fiber swelling. The warp/weft densities and crimp ratios increased as the alkali concentrations increased. The breaking and tearing loads of untreated Lyocell fabrics were higher than those of alkali pretreated fabrics since the strength loss caused by alkali pretreatment. The abrasive load caused fiber breakages and fiber entanglements on fabrics and decreased the both breaking and tearing loads. The weave types with long floating interlacements on the fabric surface were more severely damaged by exposing to abrasive load and resulted as higher strength reduction.

Achieving ultra-tear resistant high-performance natural rubber nanocomposite via bio-inspired lignocellulosic compatibilization

Elastomers which are strong, tough, and resistant to tearing, are highly attractive for engineering applications such as conveyer belts, high-performance seals, tires, and soft robotics. Enhancing these properties for natural rubber materials is possible by utilizing nanoscale fillers, however the nanocomposite approach remains challenging because (a) nanofillers can impede latex molecular crosslinking, and (b) reduce the material’s inherent elasticity and compliance. This study demonstrates an approach to prepare ultra-strong, tear-resistant natural rubber nanocomposites using cellulose nanofibers decorated with nanoscale lignin. The reinforcement of latex with 0.1 wt% cellulose nanofibre compatibilized with 0.5 wt% lignin resulted in a 256% improvement in tear strength, 95% in tensile strength, and 50% in toughness, while retaining the elongation at break. Such a simultaneous improvement in tensile and tear properties has not been previously achieved through the latex casting method with any other fillers, and herein it is attributed to the nanoscale reinforcement efficiency of nanofibre coupled with enhanced interfacial adhesion between nanofibers and NR latex with the introduction of nanoscale lignin. This compatibilization approach has also resulted in improved resilience in the nanocomposites, as evidenced by the cycling loading and unloading analysis.

Tensile and Tearing Properties of a Geocomposite Mechanically Damaged by Repeated Loading and Abrasion

The behaviour of geosynthetics can be affected by many agents, both in the short and long term. Mechanical damage caused by repeated loading or abrasion are examples of agents that may induce undesirable changes in the properties of geosynthetics. The research conducted in this work complemented previous studies and consisted of submitting a geocomposite, isolated and successively, to two degradation tests: mechanical damage under repeated loading and abrasion. The geocomposite (a nonwoven geotextile reinforced with polyethylene terephthalate filaments) was tested on both sides (with or without filaments) and directions (machine and cross-machine). The impact of the degradation tests on the geocomposite was quantified by monitoring changes in its tensile and tearing behaviour. The results showed that, in most cases, the degradation tests caused the deterioration of the tensile and tearing behaviour of the geocomposite, affecting its reinforcement function. The decline in tensile strength correlated reasonably well with the decline in tearing strength. Changing the side and direction tested influenced, in some cases (those involving abrasion), the degradation experienced by the geocomposite. The reduction factors (referring to tensile and tearing strength) for the combined effect of the degradation agents tended to be lower when determined by using the common method (compared to those resulting directly from the successive exposure to both agents).

Circular Economy Insights on the Suitability of New Tri-Layer Compostable Packaging Films after Degradation in Storage Conditions.

The environmental degradation of the films used in packaging is a key factor in their commercial use. Industrial and academic research is aimed at obtaining materials that have degradation features that ensure their eco-sustainability but, at the same time, preserve their use properties during storage and distribution periods. This study analyzes the degradability behavior over time of commercial packaging that meets the requirements of the UNE 13432 standard and the prEN 17427 (2020) home composting certification requirements under standard storage conditions. The study attempts to provide insight into the durability of the films under standard storage conditions, verifying that this type of packaging has a useful life of more than 12 months and that after this storage period it still retains the usability properties for which it was conceived. The analyzed sample has been manufactured using a three-layer technology under some commercial formulations based on PBAT + STARCH + PLA and has been analyzed monthly for 12 consecutive months. The macroscopic monitoring of the degradation of the sample has been carried out through the evolution of the mechanical properties and the quantification of the color changes (very important in films) via colorimetry. The nature of the observed variations has been justified at the microstructural level from the data obtained in calorimetric analysis (DSC) and from the characterization using FTIR. The results indicate a loss of properties in the tensile, elongation and impact tests and a behavior of stability or improvement in the tear properties of the film. Analyzing the microstructural changes, it is observed that the degradation of a hydrolytic and thermo-oxidative type occurs in the amorphous part of the film. The conclusion of this study is that the proposed packaging, focused on domestic composting and stored under standard conditions, has a useful life of more than 12 months. This period should be sufficient to cover the stages of production, storage and final use.

Structural design and mechanical properties of glass fiber weft-knitted biaxial tubular fabrics

In order to design glass fiber weft-knitted biaxial tubular (WKBT) fabric with the excellent dimensional stability and outstanding mechanical properties, six kinds of WKBT fabrics were prepared by four kinds of knitting structures (1 + 1 rib structure, face plating structure, back plating structure and face and back plating structure) and two kinds of stitch yarns (polyester and polytetrafluoroethylene fiber). The tensile properties, tearing properties and bursting tearing properties of WKBT fabrics with different binding tightness were investigated. The results showed that the failure of WKBT fabric was composed of the breakage of insertion yarns and the breakage of knitting structures. The tightness of knitting structures have significant effect on the mechanical properties of WKBT fabric. Compared with 1 + 1 rib structure, the plating structure affects the mechanical properties of WKBT fabrics by improving the weft density, binding tightness and dimensional stability. The kind of stitch yarn is another factor that affects the mechanical properties of WKBT fabrics.

In vivo measurement of the elastic properties of pelvic floor muscles in pregnancy using shear wave elastography.

We aimed to investigate changes in the elastic properties of levator ani muscle (LAM) and external anal sphincter (EAS) during pregnancy using shear wave elastography (SWE). Our secondary objective was to examine the association between the elastic properties of pelvic floor muscles (PFM) and perineal tears at childbirth. This was a prospective monocentric study, including nulliparous women. Three visits were planned (14-18, 24-28, and 34-38weeks) with a SWE assessment of the LAM and EAS at rest and during Valsalva maneuver. Then, we collected data about the delivery's characteristics. Assessments were performed using an Aixplorer V12® device (SL 18-5 linear probe) using a transperineal approach, reporting the shear modulus in kPa. We looked for changes in PFM's elastic properties during pregnancy using one-way ANOVA for repeated measures. We compared the mean shear modulus in late pregnancy for each muscle and condition between women with an intact perineum at delivery and those with a perineal tear using Student's t test. Forty-seven women were considered. Forty-five women had vaginal delivery of which 38 (84.4%) had perineal tears. We did not report any significant changes in the elastic properties of PFM during pregnancy. Women with an intact perineum at delivery had a stiffer EAS at Valsalva maneuver in late pregnancy (27.0kPa vs. 18.2kPa; p < 0.005). There were no significant changes in the elastic properties of the PFM in pregnancy. Stiffer EAS in late pregnancy appears to be associated with a lower incidence of perineal tears.

Characterization of an eco-friendly rubber composite material based on Sansevieria cylindrica fibers

The weak bonding of the natural fiber in its raw state, with easy breakage and extreme moisture absorption, has many flaws, disadvantages, such as low load-bearing capacity. In addition, these factors are at the root of a mixture of fibers that control the performance or properties. In this paper, the surface is alkali-modified on Sansevieria Cylindrica fibers to overcome the above limitations and the treated fibers are introduced in the maximum viable agglomeration-free amount of 30% (assuming natural rubber quantity as equal to 100) to act as the reinforcement for new composites. Tensile, tear properties and Shore A hardness of the obtained composites, indicated as Sansevieria Cylindrica rubber composites (SCRC), with respect to neat rubber and untreated fibers composites are analyzed and the fracture morphology of treated fiber composites is also elucidated.

Shedding light on the viscoelastic behavior of artificial and human tears: A microrheological approach

This study conducts research on the viscoelastic properties of biological fluids, including both hyaluronic acid-containing lubricating eye drops and human tears, by means of passive microrheology. By tracking the Brownian motion of tracer particles of various sizes in the fluids, we were able to probe their viscoelastic properties. The results showed that the viscoelastic properties of artificial tears, such as Newtonian viscosity and relaxation time, scale to the concentration and macromolecular size of hyaluronic acid, resembling unentangled semidiluted solutions. Moreover, human tears were found to have a viscosity that is 50% greater than that of pure water, comparable to artificial tears containing 0.1% hyaluronic acid, but with a relaxation time one order of magnitude longer than ophthalmic solutions. This behavior was attributed to their intricate composition. The distinctive aspect of this study lies in demonstrating the feasibility of measuring the rheological properties of human tears, a biofluid of great interest, using extremely small sample volumes and microrheology, providing comprehensive information across a wide range of frequencies approaching those corresponding to blinking upon the application of the Cox–Merz rule. These findings are of significant value as they pave the way for future research on small volumes of tears from ophthalmic patients.

Rotator cuff repair with an interposition polypropylene mesh: A biomechanical ovine study.

Chronic large to massive rotator cuff tears are difficult to treat and re-tears are common even after surgical repair. We propose using a synthetic polypropylene mesh to increase the tensile strength of rotator cuff repairs. We hypothesize that using a polypropylene mesh to bridge the repair of large rotator cuff tears will increase the ultimate failure load of the repair. To investigate the mechanical properties of rotator cuff tears repaired with a polypropylene interposition graft in an ovine ex-vivo model. A 20 mm length of infraspinatus tendon was resected from fifteen fresh sheep shoulders to simulate a large tear. We used a polypropylene mesh as an interposition graft between the ends of the tendon for repair. In seven specimens, the mesh was secured to remnant tendon by continuous stitching while mattress stitches were used for eight specimens. Five specimens with an intact tendon were tested. The specimens underwent cyclic loading to determine the ultimate failure load and gap formation. The mean gap formation after 3000 cycles was 1.67 mm in the continuous group, and 4.16 mm in the mattress group (P = 0.001). The mean ultimate failure load was significantly higher at 549.2 N in the continuous group, 426.4 N in the mattress group and 370 N in the intact group (P = 0.003). The use of a polypropylene mesh is biomechanically suitable as an interposition graft for large irreparable rotator cuff tears.

Tear-film evaporation flux and its relationship to tear properties in symptomatic and asymptomatic soft-contact-lens wearers

PurposeWith soft-contact-lens wear, evaporation of the pre-lens tear film affects the osmolarity of the post-lens tear film and this can introduce a hyperosmotic environment at the corneal epithelium, leading to discomfort. The purposes of the study are to ascertain whether there are differences in evaporation flux (i.e., the evaporation rate per unit area) between symptomatic and asymptomatic soft-contact-lens wearers, to assess the repeatability of a flow evaporimeter, and to assess the relationship between evaporation fluxes, tear properties, and environmental conditions. MethodsClosed-chamber evaporimeters commonly used in ocular-surface research do not control relative humidity and airflow, and, therefore, misestimate the actual tear-evaporation flux. A recently developed flow evaporimeter overcomes these limitations and was used to measure accurate in-vivo tear-evaporation fluxes with and without soft-contact-lens wear for symptomatic and asymptomatic habitual contact-lens wearers. Concomitantly, lipid-layer thickness, ocular-surface-temperature decline rate (i.e., °C/s), non-invasive tear break-up time, tear-meniscus height, Schirmer tear test, and environmental conditions were measured in a 5 visit study. ResultsTwenty-one symptomatic and 21 asymptomatic soft-contact-lens wearers completed the study. A thicker lipid layer was associated with slower evaporation flux (p < 0.001); higher evaporation flux was associated with faster tear breakup irrespective of lens wear (p = 0.006). Higher evaporation flux was also associated with faster ocular-surface-temperature decline rate (p < 0.001). Symptomatic lens wearers exhibited higher evaporation flux than did asymptomatic lens wearers, however, the results did not reach statistical significance (p = 0.053). Evaporation flux with lens wear was higher than without lens wear but was also not statistically significant (p = 0.110). ConclusionsThe repeatability of the Berkeley flow evaporimeter, associations between tear characteristics and evaporation flux, sample-size estimates, and near statistical significance in tear-evaporation flux between symptomatic and asymptomatic lens wearers all suggest that with sufficient sample sizes, the flow evaporimeter is a viable research tool to understand soft-contact-lens wear comfort.

Mechanical Properties of Metallocene Linear Low-Density Polyethylene Mulch Films Correlate with Ultraviolet Irradiation and Film Thickness

Mulching technology has created a major problem of agricultural plastic pollution. This is because the mulch is severely degraded by UV (ultraviolet) irradiation and the mechanical properties deteriorate, which makes mechanical recycling or manual recycling difficult. This study was conducted on m-LLDPE (metallocene linear low-density polyethylene) mulch films. The difference in mechanical properties of specimens in the TD (transverse direction) and PD (parallel direction) was investigated, and the changes in the mechanical properties after UV irradiation were compared. Finally, an initial mulch mechanical property evaluation model was developed to adapt to different recovery machines and crop agronomic requirements. The results suggest that the mechanical properties of m-LLDPE mulch films were strongly influenced by the film thickness, and also showed directional differences in tensile and tear properties. After UV irradiation, the mechanical properties of the specimens were enhanced after a short period of time, but the overall trend was a non-linear decay which gradually slowed down with time.

Improvement of mechanical and dynamic properties of high silica filled epoxide functionalized natural rubber

In this research, 3 different low degrees (4, 8, and 14 mol%) of epoxide functionalized natural rubber were prepared via chemical modification of natural rubber, which was then vulcanized. Each of them was mixed with silica (50 parts per hundred of rubber) without a silane coupling agent and investigated their properties. It was found that the tensile and tear properties, as well as abrasion resistance of the silica filled epoxide functionalized natural rubber vulcanizates were higher than the silica filled natural rubber vulcanizate. These properties improvements could be attributed to the interaction of the silanol groups of the silica with the epoxide groups of the modified rubber chains via chemical and physical interactions. This could be supported by the occurrence of tear parts from the morphology investigation of the tensile fractured surface of the modified rubber vulcanizates using a scanning electron microscope. The presence of silicon elements in the rubber matrix was evidenced by scanning electron microscopy and energy dispersive X-Ray spectrometer. Moreover, the silica filled epoxide functionalized natural rubber having 14 mol% epoxide content without a silane coupling agent exhibited low abrasion loss, low heat build-up and enhancement in loss tangent at 0 °C, hence improved wet skid resistance, compared to the silica filled natural rubber without a silane coupling agent. This work demonstrated that the prepared low degree of epoxide functionalized natural rubber could be potentially applied to the tire tread rubber application without the use of a silane coupling agent.

Auxetic behavior of 3D woven warp, weft, and bidirectional interlock structures

ABSTRACT Natural fibers are gaining importance due to environmental concerns and sustainability issues. However, their mechanical performance is not up to the mark. To overcome this problem, natural fiber-based 3D woven structures are used in structural applications. The mechanical performance of 3D woven structures can be further enhanced by adding auxetic mechanisms to the structures. Auxetic structures have exceptional mechanical properties due to a negative Poisson’s ratio. In the present study, 3D woven orthogonal warp, weft, and bidirectional interlock structures were developed with jute yarn, and the effect of interlocking pattern on the auxeticity and different mechanical properties (tensile, stiffness, tear) of the structures was investigated. The results revealed that the 3D warp interlock structure showed the highest auxeticity, while the bidirectional interlock depicted the least auxeticity. Due to higher auxeticity, the thickness of the warp interlock structure was increased after applying force to it. The change in the thickness of the woven structure also increases its energy dissipation capability. Furthermore, structures having higher auxeticity also manifest higher tensile, stiffness, and tear properties as compared to other structures. The results are also statistically analyzed using one-way ANOVA (Tukey).

INVESTIGATION OF THE USAGE OF ALTERNATIVE NEW GENERATION ECO-FRIENDLY FIBER BLENDS IN SYNTHETIC BASED DENIM FABRICS

Polyester yarn is made from post-consumer waste such as bottles, fabrics, etc., in the composition of polyester ethylene terephthalate (PET). Polyester (mainly polyethylene terephthalate, PET) is the most commonly employed textile fibre with over 50% share in total production of textile fibres. Pla is a biobased and biodegradable polymer produced from renewable resources. PLA is also a thermoplastic aliphatic compostable polyester. In this study, 75% Cotton - 25% PLA, 75% Lyocell - 25% PLA and 75% Cotton - 25% PET blended yarns were produced as rigid, corespun and dualcore in the ring spinning system .The fabrics were weaved with produced yarn. In the finishing processes, some of the fabrics were treated with caustic and some of the fabrics were only washed. Fabrics containing PLA and PET were compared with each other. Fabrics containing PLA and PET fiber were evaluated in terms of strength, elasticity, abrasion and pilling performances. Although the weft tensile and tear properties of Cotton-PLA blended fabrics are lower than Lyocell-PLA and Cotton-PET blends, it has been indicated that PLA blended yarns can be used as an alternative to PET based yarns and fabrics.