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1

A comparative study on the damage initiation mechanism of elastomeric composites

Da Silva Botelho T., Isac N., Bayraktar E.

Archives of Computational Materials Science and Surface Engineering

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2009

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Vol. 1, nr 2

112-119

EN

Purpose: Modelling - Finite Element Analysis (FEA) of the damage initiation mechanisms in thin rubber sheet composites were carried out under static solicitation at room temperature. Natural rubber vulcanised and reinforced by carbon, NR is used in this study. Design/methodology/approach: Experimental results were compared with that of the Finite Element Analysis (FEA). Damage mechanism has been described with a threshold criterion to identify the tearing resistance, characteristic energy for tearing (T) and damage in the specimens was evaluated just at the beginning of the tearing by assuming large strain. A typical type of specimen geometry of thin sheet rubber composite materials was considered under static tensile tests conducted on the smooth and notched specimens with variable depths. In this way, the effects of the plane stress on the damage mechanism are characterized depending on the rubber materials. Findings: In this stage of this research, a finite element analysis (FEA) has been applied under the same conditions of this part in order to obtain the agreement between experimental and FEA results. The numerical modelling is a representation of a previous experimental study. The specimen is stretched more than once its initial size, so that large strains occur. A hyper elastic Mooney-Rivlin law and a Griffith criterion are chosen. The finite elements analysis was performed with ABAQUS code (V.6.4.4). The tearing energy is evaluated with contour integrals. The Griffith criterion states that a notch with an initial length will elongate of a differential length for a given strain state only if the variation of elastic energy is higher than the variation of the surface energy related to the newly created surface. Practical implications: A tearing criterion was suggested in the case of simple tension conditions by assuming large strain. In the next step of this study, a finite element analysis (FEA) will be applied under the same conditions of this part in order to obtain the agreement between experimental and FEA results. Originality/value: This study proposes a threshold criterion for the damage just at the beginning of the tearing for thin sheet rubber composites and gives a detail discussion for explaining the damage mechanisms. Comparison of FEA results with those of experimental studies gives many facilities for the sake of simplicity in industrial application.

2

On the localization of the failure at the boundary of a hole in the orthotropic stretched disc

Wieromiej-Ostrowska A.

Technical Sciences / University of Warmia and Mazury in Olsztyn

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2006

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nr 9

55-64

EN

The localization of failure initiation in a simple tension test applied to the infinite orthotropic disc with a circular hole is considered. The considerations are based on the Tsai and Wu model. According to the author's supposition, the angular coordinate of the failure at the hole boundary should depend on the form of the polynomial failure criterion. The computations based on accessible handbook data for the elastic and strength properties of chosen typical composite material have not confirmed the above supposition, giving evidence of surprising insensitivity of to changes in both elastic and strength characteristics of the material.

PL

Rozważania nad zniszczeniem kompozytów oparto na kryterium Tsai i Wu. Zbadano przydatność testu prostego rozciągania dla nieskończonej tarczy z otworem kołowym. Miejsce zniszczenia na obwodzie tarczy wyznacza kąt φ[0], który mógłby zależeć od postaci funkcji wytężenia F. Analizę przeprowadzono na podstawie danych literaturowych dla wybranego typowego kompozytu zbrojonego jedną rodziną włókien. Otrzymane wyniki pozwalają wnioskować, że kąt φ[0] zależy od właściwości badanego kompozytu dla pewnej klasy materiałów.

3

Analiza statyczna tarczy włóknistej ze szczelinami

Olejniczak M., Delyavskyy M., Onyshko L.

Zeszyty Naukowe. Mechanika / Akademia Techniczno-Rolnicza w Bydgoszczy

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2004

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Z. 54(243)

231-240

PL

Zaproponowano metodę określania lokalnego stanu naprężeń i przemieszczeń w tarczy ortotropowej ze szczelinami. Wyprowadzono wzory asymptotyczne rozkładu przemieszczeń i naprężeń w pobliżu szczeliny o małym niezerowym promieniu krzywizny konturu w wierzchołku. Otrzymano wyrażenia uogólnionych współczynników intensywności naprężeń i odpowiednich parametrów ich rozkładu. Przeprowadzono analizy parametryczne dla przypadku dwuosiowego rozciągania tarczy z jedną szczeliną oraz z szeregiem kolinearnych szczelin.

EN

An approach for determining the local strain-stress state of an orthotropic sheet with thin cut of a small nonzero curvature radius at the tip is developed. The asymptotic formulae of distribution of stresses and displacements near the cut tip are obtained. Expressions of generalized stress intensity factors and following terms of asymptotic expansions are obtained. As examples the biaxial tensile of a sheet having one cut or collinear array of cuts are considered.