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1

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

Ashir Moniruddoza, Nocke Andreas, Cherif Chokri

Autex Research Journal

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2019

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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.

2

Parametric characterization of a mesomechanic kinematic in plain and twill weave 2/2 reinforced composites by FE-calculations

Romano M., Ehrlich I., Gebbeken N.

Archives of Materials Science and Engineering

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2019

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Vol. 97, nr 1/2

20--38

EN

Purpose: A parametric characterization of a mesomechanic kinematic caused by ondulation in fabric reinforced composites is investigated by numerical investigations. Design/methodology/approach: Due to the definition of plain representative sequences of balanced plain-weave and twill-weave 2/2 fabric reinforced single layers based on sines the variable geometric parameters are the amplitude and the length of the ondulation. Findings: The mesomechanic kinematic can be observed in the FE analyses for both kinds of fabric constructions. Research limitations/implications: The FE analyses consider elasticity and contraction due to Poisson effects, respectively, of the model under selected longitudinal strains. Practical implications: The results are evaluated at relevant positions on the centre-line of the ondulated warp-yarn of the plain representative model. A direct and linear coupling in case of the transversal kinematic behaviour, and thereby a corresponding definite reduction of the evaluated longitudinal strains in terms of the difference of the applied and determined longitudinal strains is identified. Originality/value: Both characteristic purely kinematic reactions due to geometric constraints directly depend on the introduced degree of ondulation. This non-dimensional parameter relates amplitude and length of one complete ondulation, and thus represents the intensity of the ondulation of the respective fabric construction.

3

Experimental investigation of energy dissipation properties of fibre reinforced plastics with hybrid layups under high-velocity impact loads

Romano M., Hoinkes C., Ehrlich I., Höcherl J., Gebbeken N.

Journal of Achievements in Materials and Manufacturing Engineering

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2014

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Vol. 64, nr 1

5--19

EN

Purpose: The present work deals with the experimental investigation concerning the energy dissipation capacity of different kinds of reinforcement fibres in monolithic and hybrid layups under high velocity impact loads. The investigated kinds of fibres are carbon, glass and basalt. Design/methodology/approach: The test panels have been impregnated with thermoset resin. Curing was done by autoclave processing. In order to obtain comparable fibre volume contents of approx. 60 % in the different layups (monolithic and hybrid without and with separating layer), curing cycles adapted to the type of layup have been identified. The resulting fibre volume content of the test panels has been determined both by weighing and experimentally by chemical extraction and calcination. The impact load was applied by an instrumented experimental setup. Thereby both commercially available bullets and bearing balls accelerated with weighted propellant in a sabot have been used as impactors. The measured values are the velocities of the bearing balls as the impactor before and after penetration of the test panels. Findings: In both cases the results show the energy dissipation capacity of each single kind of fibre in case of the monolithic layups as well as the enhanced properties of the hybrid stacked layups without and with the separating layer as a core material. Typical failure modes on the impact surface and on the outlet areas are identified. Research limitations/implications: The influence of the respective kind of impactors, namely bullets and bearing balls, on the evaluated results is identified. Thereby the bearing balls exhibited a higher degree of reproducibility due to several reasons. Originality/value: Fibre reinforced plastics with hybrid stacking sequences can be used as load-bearing structures and at the same time as safety structures for passengers in automotive or aerospace applications. Moreover, with the hybrid stacked composites lightweight concepts can efficiently be realized regarding energy saving issues.

4

Tworzywa wzmocnione włóknami (TWW) – zadanie dla mechaników

Krywult B.

Mechanik

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2013

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R. 86, nr 4

309--311

PL

Przedstawiono pozycję, jaką powinny zająć tworzywa wzmocnione włóknami (TWW) w aktualnie stosowanych procesach wytwarzania wyrobów. TWW powinny być efektywnym substytutem blach metalowych. Omówiono kwestię „granicznych kosztów” wytwarzania dla typowych dziedzin zastosowań. Podkreślono rolę, jaką pełnią inżynierowie mechanicy w opracowywaniu korzystnych ekonomicznie metod technologicznych i maszyn do przetwórstwa TWW. Zestawiono podstawowe problemy związane z kształtowaniem wyrobów z TWW.

EN

Position of Fibre Reinforced Plastics (FRP) in aktual manufacturing processes is discussed. Possybilities of FRP to act as a substitute for sheet metal are analysed. The „border costs” of FRP manufacturing for indywidual applications are presented. Opportunities for mechanical engineers in discovering an economical profitable technological methods and machinery is very significant. Fundamental problems with FRP manufacturing are compared.

5

Tailoring - metoda kształtowania właściwości tworzyw wzmocnionych włóknami (TWW)

Krywult B.

Przegląd Mechaniczny

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2005

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nr 6

44-46

PL

Celem artykułu jest przedstawienie podstaw teoretycznych tailoringu oraz możliwości obliczeniowych makrostruktur TWW.

6

Źródła uszkodzeń i zniekształceń wytworów z tworzyw wzmocnionych włóknami

Krywult B.

Polimery

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2002

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T. 47, nr 1

48-53

PL

Naprężenia powstające w procesach kształtowania wytworów z tworzyw wzmocnionych włóknami (TWW) i stanowiące skutek zjawisk termomechanicznych towarzyszących takim procesom są główną przyczyną uszkodzeń strukturalnych oraz zniekształceń otrzymanych wytworów. Znajomość tych zjawisk termomechanicznych stanowi więc czynnik konieczny do analizy konstrukcji i obliczeń technologicznych. Przedstawiono podstawy teoretyczne zjawisk termomechanicznych, analizę możliwych przyczyn powstawania naprężeń technologicznych oraz przykłady obliczeń konstrukcyjnych z wykorzystaniem programów komputerowych.

EN

Process-induced thermomechanical stresses give rise to crack initiation, crack growth, and final failure. Fundamentals of thermomechanical phenomena are presented (eqns. 1-8); possible reasons for stresses are outlined and illustrative CAD calculations are presented (Figs. 3-6).

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Pultruzja - efektywna metoda wytwarzania półwytworów z tworzyw wzmocnionych włóknami

Krywult B.

Polimery

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2001

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T. 46, nr 10

673-677

PL

W artykule przeglądowym poświęconym charakterystyce pultruzji ciągłego procesu technologicznego wytwarzania prętów, rur i kształtowników z TWW - przedstawiono technologiczny opis tego procesu oraz wymagania materiałowe dotyczące zarówno włókien, i przesycającej je żywicy (żywicznej osnowy). Szczegółowo omówiono wpływ zawartości włókien wzmacniających oraz elastyczności żywicznej osnowy na naprężenia styczne występujące w strukturze otrzymywanych półwytworów z TWW. Podkreślono przy tym trudności związane z wyborem żywicy o odpowiedniej elastyczności i właściwościach cieplnych.

EN

A review with 9 refs. covering a continuous pultrusion process for making GRP rod, pipe, and other shaped sections, specifying the requirements on glass fiber and impregnating (matrix) resin. Tangential stresses occurring in the product are discussed in relation to fiber content and resin elasticity.