“…The higher strength at 30 T/m can be attributed to the better interfacial adhesion of twisted filament and epoxy, which provide better lateral cohesion between filaments and the bonding shear strength between the filaments and epoxy, respectively. Similar behaviour has been reported in the literature [8,52]. The decrease in the strength of composites with higher twist levels may be attributed to the obliquity of the filaments and inability of resin infiltration in highly twisted yarn due to decrease in the cross-sectional area of twisted tows resulting in low inter-filament gaps [51].…”
“…In addition the results of investigation of Cheung et al [54] showed that the strain to failure for Kevlar 49 twisted tubular braided composites was increase with increasing level of twist. Similar behaviour has been reported in the literature [51,52] In addition, the experimental tensile strength of composite laminates values are compared with theoretical tensile strength values and shown in Figure 11 [51].…”
High modulus/high strength continuous fibres are used extensively for manufacturing textile preforms, as a reinforcement, for composites due to their excellent specific properties. However, their brittle behaviour and tendency to separate easily into individual filaments or bundles can lead to damages during manufacturing processes such as weaving and braiding. Thus, the critical step in the development of an optimal yarn for textile-reinforced composites is to find an optimum twist, which results in a minimum loss of properties of the composite laminates, while maintaining good processability and sufficient strength for textile and/or composite manufacturing. In this study, twist level has been varied to improve the handling and tensile properties of S-glass yarns (i.e. tensile strength). Varying levels of yarn twist (15–40 twists metre−1) were employed to study its impact on the tensile properties (i.e. tensile strength, modulus, elongation at break etc.). Furthermore, the effect of twist on the tensile properties of non-crimp cross-ply composites produced via vacuum infusion process was studied. It was observed that mechanical performance (i.e. tensile strength properties) of twisted yarns is improved up to 30 twists metre−1 while it is deteriorated at 40 twists metre−1. At yarn level, the experimental results were compared with theoretical estimations utilizing existing models for twisted yarns properties. Discrepancies were observed between experimental and theoretical results especially for high level of twist. The tensile strength and elongation of S-glass cross-ply composites at all levels of twist were higher compared to the composite laminates manufactured by using non-twisted yarns. At composite level, the experimental results were also computed employing rule of mixture and good agreement was observed between experimental and predicted results.
“…The higher strength at 30 T/m can be attributed to the better interfacial adhesion of twisted filament and epoxy, which provide better lateral cohesion between filaments and the bonding shear strength between the filaments and epoxy, respectively. Similar behaviour has been reported in the literature [8,52]. The decrease in the strength of composites with higher twist levels may be attributed to the obliquity of the filaments and inability of resin infiltration in highly twisted yarn due to decrease in the cross-sectional area of twisted tows resulting in low inter-filament gaps [51].…”
“…In addition the results of investigation of Cheung et al [54] showed that the strain to failure for Kevlar 49 twisted tubular braided composites was increase with increasing level of twist. Similar behaviour has been reported in the literature [51,52] In addition, the experimental tensile strength of composite laminates values are compared with theoretical tensile strength values and shown in Figure 11 [51].…”
High modulus/high strength continuous fibres are used extensively for manufacturing textile preforms, as a reinforcement, for composites due to their excellent specific properties. However, their brittle behaviour and tendency to separate easily into individual filaments or bundles can lead to damages during manufacturing processes such as weaving and braiding. Thus, the critical step in the development of an optimal yarn for textile-reinforced composites is to find an optimum twist, which results in a minimum loss of properties of the composite laminates, while maintaining good processability and sufficient strength for textile and/or composite manufacturing. In this study, twist level has been varied to improve the handling and tensile properties of S-glass yarns (i.e. tensile strength). Varying levels of yarn twist (15–40 twists metre−1) were employed to study its impact on the tensile properties (i.e. tensile strength, modulus, elongation at break etc.). Furthermore, the effect of twist on the tensile properties of non-crimp cross-ply composites produced via vacuum infusion process was studied. It was observed that mechanical performance (i.e. tensile strength properties) of twisted yarns is improved up to 30 twists metre−1 while it is deteriorated at 40 twists metre−1. At yarn level, the experimental results were compared with theoretical estimations utilizing existing models for twisted yarns properties. Discrepancies were observed between experimental and theoretical results especially for high level of twist. The tensile strength and elongation of S-glass cross-ply composites at all levels of twist were higher compared to the composite laminates manufactured by using non-twisted yarns. At composite level, the experimental results were also computed employing rule of mixture and good agreement was observed between experimental and predicted results.
“…In contrast, a twist level over 2000 turns per m −1 damaged the PdO@ZnO-5%/PAN NF and reduced the tensile strength of PdO@ZnO-5%/PAN NFs. 57 Therefore, the optimal twisting level of PdO@ZnO-5%/PAN NF for improving the mechanical strength was 2000 turns per m −1 . Figure 6.(a) Photograph of flexible colorimetric hydrogen-sensing yarn (electrospinning + twist).…”
Section: Resultsmentioning
confidence: 99%
“…In contrast, a twist level over 2000 turns per m À1 damaged the PdO@ZnO-5%/ PAN NF and reduced the tensile strength of PdO@ZnO-5%/PAN NFs. 57 Therefore, the optimal twisting level of PdO@ZnO-5%/PAN NF for improving the mechanical strength was 2000 turns per m À1 . To maintain both the twisted morphology and sensing materials in the PdO@ZnO-5%/PAN NF and improve the mechanical strength, PdO@ZnO-5%/ PAN NF with a twisting level of 2000 turns per m À1 was coated with PDMS 20, PDMS 30, and PDMS 40 and the feasible concentration was identified as the final step ( Figure S3(b)).…”
Section: Application Of the Flexible Colorimetric Hydrogen Sensormentioning
A colorimetric hydrogen sensor has great potential for accurately detecting and monitoring the leakage of hydrogen gas on account of its fast color change in contact with hydrogen gas. However, for the practical application of the sensor, such as in gas detection systems in clothing, the flexibility and stability of the sensor need to be improved. Here, we present a novel method to fabricate a flexible colorimetric hydrogen sensor with the stable embedment of sensing material. To improve the flexibility and stability of the sensor, polyacrylonitrile nanofiber containing palladium oxide and zinc oxide hybrid nanoparticles was prepared by electrospinning. The flexible colorimetric hydrogen sensor can detect 1000 ppm hydrogen gas with excellent selectivity within 2 min. We also suggest film and yarn-type flexible colorimetric hydrogen sensors for industrial and wearable applications. A laminating process was used to prepare the film. In contrast, twisting and polydimethylsiloxane coating were used to prepare the yarn-type flexible colorimetric hydrogen sensor. Compared with a flexible colorimetric hydrogen-sensing nanofiber, the film and yarn show identical sensitivity for detecting a hydrogen leakage. These applications of hydrogen sensors could be a new insight into the design of a flexible sensor for detecting hydrogen leakage with the naked eye.
“…The results showed that the composites reinforced by fabrics with different stitching yarns had respective advantages in tensile strength, bending strength or three-point bending impact properties. And the research reveals the different performance characteristics and application advantages of aramid, glass and nylon stitching yarns [17]. Oudet and Bunsell [18] analyzed the behavior of two types of polyester fibers on the basis of tensile, creep, and fatigue properties.…”
The carbon weft-knitted biaxial fabrics stitched by polyester fibers and preoxidized polyacrylonitrile fibers were prepared respectively. Tensile and tearing tests of two types of carbon biaxial weft-knitted fabrics stitched by different fibers were carried out. Stressstrain and load-displacement curves were obtained according to the testing data. The highspeed camera was employed to observe the whole testing process and series of still images were picked up according to the time nodes to analyze the meso-scale mechanism of the extension and displacement of tows on oriented layers and stitching yarns. The properties of the two fabrics were compared based on the research of the stitching yarns mechanical performance. The researching results indicated that preoxidized polyacrylonitrile fiber exhibit higher mechanical behaviors, and its fabric bond displays excellent performance.
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