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Paper Award for Masoud Sistaninia and Prof. Dr. Otmar Kolednik

The paper by Sistaninia and Kolednik [1] has been highlighted as one of the 4 most interesting papers in 2014 by European Structural Integrity Society (ESIS).

This paper, which is an output of a strategic project in the COMET K2 MPPE Center, introduces a new idea for enhancing the fracture resistance of materials by inserting soft interlayers, i.e. application of the yield stress inhomogeneity effect. For more information about the paper, please see detail below:

Certain highly fracture resistant biological materials, such as deep-sea glass sponges (Fig. 1a), have a microstructure consisting of layers made of hard and brittle bio-glass and thin, compliant protein interlayers. It has been revealed that the multi-layered structure with strong spatial variation of the Young’s modulus between the hard and brittle bio-glass and the thin, compliant protein layers is the dominant mechanism for the high fracture resistance of the glass sponge [2]. The reason is that the crack driving force strongly decreases when the crack enters the compliant interlayer (Fig. 1b). It has been shown that the strength and fracture resistance of a composite becomes much higher than that of the homogenous material, if the composite architecture fulfills certain design criteria [2,3]. A problem is, however, that these criteria can be only used for elastic materials.

In the recent paper [1], it has been shown that the idea of enhancing the fracture resistance by introducing compliant interlayers can be extended to elastic-plastic technical materials, since spatial variations of the yield stress can also greatly improve the fracture resistance. The reason is that, when the crack has crossed a soft interlayer, the crack driving force strongly decreases and the crack is arrested by the interlayer, see Fig. 2. From the results of numerical studies with the configurational force concept, optimum interlayer configurations have been derived, i.e. for a given matrix material and load, the magnitudes of thickness and yield stress of the soft interlayer have been determined so that the interlayers work as effective crack arresters. Such optimum configurations can be used for the design of fracture resistant composite materials.

 

 

[1] M. Sistaninia, O. Kolednik, Eng. Fract. Mech. 130, 2014, 21–41. [Link]

[2] O. Kolednik, J. Predan, F.D. Fischer, P. Fratzl, Adv. Funct. Mater. 21, 2011, 3634–3641. [Link]

[3] O. Kolednik, J. Predan, F.D. Fischer, P. Fratzl, Acta Mater. 68, 2014, 279–94. [Link]