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BULLETIN OF APPLIED MECHANICS 7(27), 46-49 (2011)

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Comparison of the Young's Modulus of Lamina and Textile Composite
Petr Janda, Tomáš Kroupa, Václava Lašová
undulation (with straight fibres). Figure 1 demonstrates composite structure formed by one layer of textile composite with plain weave. Figure 2 shows a composite structure with two layers formed by unidirectional laminae withoutfibre undulation.

Abstract - The usage of composite material is not common in machine tool design, because of conservatism in this branch and insufficient knowledge of such materials. In the near future, there might be a growth of composite materials application, thanks to their inherently low weight and high tensile strength (in longitudinal direction) in comparison with classical constructionmaterial like cast iron or steel. There is a difference in mechanical properties of textile composites and lamina, caused by the fibre undulation. For designers, the valid mechanical properties with desirable accuracy are very important. This paper deals with comparison of Young’s modulus of lamina and textile composite. The finite element method is used for the prediction of Young’s modulus ofboth composite structures. The finite element mesoscale models are created in commercial software packages Siemens NX 7.5 and MSC Marc 2008r1.
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Index Terms – composite, mechanical properties, numerical analyses
Fig. 1 – Composite structure with fibres undulation

INTRODUCTION Application of composite materials in machine tools design is not as usual as in automotive, airplane or sportinggoods design. This is caused by conservative approach of machine tools designers to selection of material and lack of knowledge. One of the most important information about material is the mechanical properties of material. Mechanical properties are usually determined using experimental approach, but the experiments are expensive and time-consuming. Other approaches of mechanical propertiesdetermination are analytical and numerical approaches (Janda, 2009). These approaches offer lower costs and sufficient agreement with experimental data. In this paper, the numerical approach is used for Young’s modulus determination. PROBLEM FORMULATION There is a wide variety of composite structures applicable in technical practice. The composite structures are classified into structures with fibreundulation and structures without fibre
Manuscript received October 9, 2011. This work was supported in part by the Research Project 1M6840770003 and GA P101/11/0288. P. Janda is with the University of West Bohemia, Faculty of Mechanical Engineering, Department of Machine Design, Univerzitní 22, 306 14 Pilsen, Czech Republic, phone: +420 377 638 272, email: jandap@kks.zcu.cz T. Kroupa is with theUniversity of West Bohemia, Faculty of Applied Sciences, Department of Mechanics, Univerzitní 22, 306 14 Pilsen, Czech Republic, phone: +420 377 632 367, email: kroupa@kme.zcu.cz V. Lašová is with University of West Bohemia, Faculty of Mechanical Engineering, Department of Machine Design, Univerzitní 22, 306 14 Pilsen, Czech Republic, phone: +420 377 638 200, email: lasova@kks.zcu.cz
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Fig. 2 –Composite structure with straight fibres

It is clear that mechanical properties of composite with fibre undulation will be different than mechanical properties of composite without fibre undulation. The fibre undulation is present at composite structures in many applications. The main goal of this paper is to analyze the influence of fibre undulation on mechanical properties of composites, namelythe Young’s modulus. The modulus of textile composite and of composite with two layers of straight fibres will be compared. The classical laminate theory (Laš, 2008) is usable for the evaluation of mechanical properties without fibre undulation. The prediction of mechanical properties of textile composites (with fibre undulation) requires modified laminate theory (Ishikawa, a další, 1982). This...