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J. Compos. Sci. 2018, 2(1), 12;

Cruciform Specimen Design for Biaxial Tensile Testing of SMC

Institute of Engineering Mechanics, Chair for Continuum Mechanics, Karlsruhe Insititute of Technology (KIT), Kaiserstr. 10, 76131 Karlsruhe, Germany
Institute of Production Science, Manufacturing and Materials Technology, Karlsruhe Insititute of Technology (KIT), Kaiserstr. 12, 76131 Karlsruhe, Germany
Institute of Mechanics, Karlsruhe Institute of Technology (KIT), Otto-Ammann-Platz 9, 76131 Karlsruhe, Germany
Author to whom correspondence should be addressed.
Received: 30 December 2017 / Revised: 5 February 2018 / Accepted: 19 February 2018 / Published: 1 March 2018
(This article belongs to the Special Issue Discontinuous Fiber Composites)
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This paper presents an investigation of different cruciform specimen designs for the characterization of sheet molding compound (SMC) under biaxial loading. The considered material is a discontinuous glass fiber reinforced thermoset. We define various (material-specific) requirements for an optimal specimen design. One key challenge represents the achievement of a high strain level in the center region of the cruciform specimen in order to observe damage, at the same time prevention of premature failure in the clamped specimen arms. Starting from the ISO norm for sheet metals, we introduce design variations, including two concepts to reinforce the specimens’ arms. An experimental evaluation includes two different loading scenarios, uniaxial tension and equi-biaxial tension. The best fit in terms of the defined optimality criteria, is a specimen manufactured in a layup with unidirectional reinforcing outer layers where a gentle milling process exposed the pure SMC in the center region of the specimen. This specimen performed superior for all considered loading conditions, for instance, in the uniaxial loading scenario, the average strain in the center region reached 87 % of the failure strain in a uniaxial tensile bone specimen. View Full-Text
Keywords: discontinuous fibers; sheet molding compound (SMC); biaxial tensile testing; cruciform specimen design; unidirectional reinforcements discontinuous fibers; sheet molding compound (SMC); biaxial tensile testing; cruciform specimen design; unidirectional reinforcements

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Schemmann, M.; Lang, J.; Helfrich, A.; Seelig, T.; Böhlke, T. Cruciform Specimen Design for Biaxial Tensile Testing of SMC. J. Compos. Sci. 2018, 2, 12.

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