Wyniki wyszukiwania - Biblioteka Nauki

1

Technological Development of a Yarn Grip System for High-Speed Tensile Testing of High-Performance Fibers

100%

Unger R. , Schegner P. , Nocke A. , Cherif C.

Autex Research Journal

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2019

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tom Vol. 19, no. 4

347--354

EN

Particularly in terms of carbon fiber (CF) rovings and further high performance fibers, it is a highly demanding task to clamp technical yarns with low elongations at break during high-speed tensile tests due to their sensitivity to shear stress. For fibers to be tested, a low elongation at break results in short testing times and requires high acceleration. In this paper, four different yarn grips that can be applied with various test machines will be introduced and compared to a wedge screw grip. By using most sensitive CF rovings, advantages and disadvantages of these gripping devices will be qualitatively evaluated by means of testing machines with test speeds of up to 20 m/s and strain rates of up to 200 s-1, respectively. Hence, the reproducibility and precision of test results were considerably enhanced by optimizing the geometry and mass of yarn grips. Moreover, theoretical approaches and calculations for the design of yarn grips suitable for test speeds of up to 100 m/s will be presented.

2

Effect of the Position of Defined Local Defect on the Mechanical Performance of Carbon-Fiber-Reinforced Plastics

100%

Ashir M. , Nocke A. , Cherif C.

Autex Research Journal

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2019

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tom Vol. 19, no. 1

74--79

EN

Considering their energy and resource efficiency, fiber-reinforced plastics (FRPs) have been displacing metals and metal alloys for lightweight constructions. During the semiautomated manufacturing process of FRPs, and in particular during the laying of reinforced fabric layers, foreign bodies are enclosed within them, which in turn reduce the mechanical performance of FRPs. The research project presented in this article investigated if the loss in mechanical properties, such as tensile, flexural, and impact strengths, depends on the position of defined local defects, polytetrafluorethylene (PTFE) in this case, in the thickness direction of FRPs. In order to achieve this aim, PTFE was placed in different layers of reinforcing fabric before infusion. Subsequently, the mechanical performance of the fabricated FRPs was tested and evaluated. On the basis of the experiment, it can be concluded that the loss in mechanical properties was maximal if PTFE was laid in the middle position of FRPs in the thickness direction.

3

Development of Methods to Improve the Mechanical Performance of Coated Grid-Like Non-Crimp Fabrics for Construction Applications

88%

Hahn L. , Rittner S. , Nuss D. , Ashir M. , Cherif C.

Fibres & Textiles in Eastern Europe

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2019

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tom Vol. 27, no. 1 (133)

51--58

EN

This paper presents investigations aiming to improve the impregnation of a coating agent and thus increase the mechanical performance of geogrids, especially grid-like non-crimp fabrics (NCF) consisting of carbon fiber heavy tows (CFHT). The squeezing process is industry standard, but the relationship between the machine setting parameters (squeezing pressure and hardness of squeeze roll surface) and the impact on the tensile strength of grid-like NCF is still unexplored. The setting parameters evaluated lead to an increase in tensile strength of up to 10% compared to grid-like NCF coated without the squeezing process. Additionally the first insights into the coating process supported by ultrasonic vibrations based on CFHT single yarns are provided. It is shown that the tensile strength of treated CFHT can be increased by up to 12%, in comparison to CFHT coated without ultrasonic vibrations.

PL

W pracy przedstawiono badania mające na celu poprawę impregnacji środka powlekającego, a tym samym poprawę właściwości mechanicznych georusztów, w szczególności tkanin niekarbikowanych typu siatkowego (NCF) składających się z ciężkich kabli włókien węglowych (CFHT). Proces zgniatania jest standardem branżowym, ale wciąż nie zbadano związku między parametrami nastawczymi maszyny (nacisk ściskania i twardość ściśniętej powierzchni walca) a wytrzymałością na rozciąganie tkanin NCF. Odpowiednio dobrane parametry nastawcze procesu zgniatania skutkują do zwiększeniem wytrzymałości na rozciąganie do 10% w porównaniu z georusztem, który nie został poddany temu procesowi. Ponadto oceniono wpływ procesu powlekania z użyciem ultradźwięków. Stwierdzono, że wytrzymałość na rozciąganie obrobionych kabli (CFHT) można zwiększyć nawet o 12%, w porównaniu z CFHT bez zastosowania obróbki ultradźwiękami.

4

Development of Loop-Shaped Textile Anchoring Reinforcements Based on Multiaxial Warp Knitting Technology

75%

Rittner S. , Speck K. , Seidel A. , Ewertowski M. , Curbach M. , Cherif C.

Fibres & Textiles in Eastern Europe

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2020

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tom Vol. 28, no. 6 (144)

64--71

EN

Due to the General Building Approval granted for the strengthening of steel reinforced concrete structures by means of textile reinforced concrete, the foundation for its introduction into practice was successfully established. It approves textile reinforcements in the form of non-crimp fabrics made of carbon fibre heavy tows with high yarn fineness. Thus, it is aimed at increasing the amount of filaments per roving in order to minimise the number of reinforcing layers required. However, the relation between the surface and cross-sectional area is compromised once fineness is increased, leading to an unfavourable enlargement of anchoring and overlapping lengths. Therefore, a recently concluded research project evaluated if this challenge can be overcome by means of a loop-shaped selvedge. This paper presents the results generated within these investigations, proving the potential of the textile-based solution. Moreover, required machine modifications based on multiaxial warp knitting technology for the integral and continuous manufacturing of anchoring textile reinforcements as well as significant results derived from bonding tests will be introduced.

PL

W pracy zaproponowano wzmocnienie konstrukcji żelbetowych za pomocą betonu zbrojonego materiałem tekstylnym w postaci tkanin wykonanych z włókien węglowych. Celem pracy było zwiększenie ilości włókien przypadających na niedoprzęd, tak aby zminimalizować liczbę wymaganych warstw wzmacniających. Jednak kompromisowa zależność między powierzchnią a polem przekroju jest zagrożona po zwiększeniu grubości, co prowadzi do niekorzystnego zwiększenia zakotwienia i zachodzenia na siebie długości. Dlatego niedawno zakończony projekt badawczy miał na celu ocenę, czy to wyzwanie można pokonać za pomocą krajki w kształcie pętli. W artykule przedstawiono wyniki uzyskane w ramach tych badań, które potwierdziły potencjał rozwiązania tekstylnego. Ponadto w wyniku przeprowadzonych badań wprowadzono wymagane modyfikacje maszyn w oparciu o technologię wieloosiowego dziania osnowowego do integralnego i ciągłego wytwarzania tekstylnych wzmocnień kotwiących.

5

Development of a method and technology for the production of 3D knitted reinforcement grids

75%

Zierold K. , Steinberg J. , Hahn L. , Rittner S. , Friese D. , Cherif C.

Fibres & Textiles in Eastern Europe

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2022

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tom Vol. 30, no. 3

18--26

EN

The use of fibre-reinforced plastic composites (FRP) for lightweight construction solutions is becoming increasingly important. The processing of 2D scrims into complete 3D FRP components has been carried out with the help of complex manual assembly steps. The disadvantages of this procedure are distortions in the textile and, thus, deviations in the fibre alignments from the calculated load path. This paper presents a newly developed basic technology for the production of 3D reinforcing grids with variable warp and weft yarn section lengths based on multiaxial warp knitting technology. For this purpose, a new type of machine module and associated control technology for the production of weft yarn reserves on a multiaxial warp knitting machine was developed. In combination with technology from previous research work on the production of warp yarn lengths suitable for component contours, a basis was created for the production of 3D reinforcing grids.

6

Experimental Investigation on the Bending Behavior of Weft Interlaced Multilayered Woven Fabrics for Composite Applications

75%

Schegner P. , Vorhof M. , Weise D. , Sennewald C. , Pilgrim J. , Hoffmann G. , Cherif C.

Fibres & Textiles in Eastern Europe

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2023

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tom Vol. 31, no. 5

24--33

EN

Direct preforming processes have potential for fiber-reinforced semi-finished products, creating 3D structures with strong delamination resistance using double-flat-steel-healds. However, the shedding method limits pattern variety, necessitating alternative options for interlacing diversity. One approach is using weft yarn instead of warp yarn for interlacing. This study explores its impact on mechanical properties, focusing on bending behavior, fiber volume content, and micrograph analysis of infiltrated warp and weft interlaced structures. The result shows interesting differences in mechanical behavior regarding different weave types and test direction as well as communalities within the individual structures.