08/04/2014

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Source: BAM

This year's DIN Innovation Award has been granted to Dr.-Ing. Fabian Grasse and Dipl.-Ing. Malte Zur. The two engineers are founders of Grasse Zur Consultants (GZI), a young start-up company, founded with the help of BAM Federal Institute for Materials Research and Testing. The DIN innovation prize is awarded annually by DIN at the Hanover Fair to honour projects on standards in innovative topics that promise success in the future.

This prize has been awarded to the young entrepreneurs because they have implemented their innovative shear test method for fibre composite materials in practice. Their shear test system GZ S-80 enables the shear characteristics of fibre composites to be determined much more accurately and for a wider range of materials than is possible using previous standardised methods.
"I am very happy for the two colleagues who have further developed our method which is now used in industry. It is a fine example of successful technology transfer," says Dr.-Ing. Volker Trappe of BAM’s Division of Mechanics of Polymers.

Fibre composites have very high specific stiffness and strength. They have a huge potential in lightweight structures, which is an advantage to car manufacture and the aircraft industry for instance. To use the lightweight potential while maintaining a high level of safety, careful coordination is needed between loads (forces acting from outside) and stresses (forces inside the material resulting from the loads). For this purpose, accurate and reliable parameters are required, which are not always sufficiently available for this fledgling class of materials.

"Test methods used to determine parameters of metallic materials cannot be applied directly to fibre composites because these materials have so-called anisotropic properties. This means that strength and stiffness in different fibre directions may differ up to several orders of magnitude. It is therefore necessary for the material parameters of each new combination of fibres and resin matrices to be determined," says Dr.-Ing. Fabian Grasse.

In GZI’s advanced development of the shear test method, a planar specimen is clamped in a frame. The frame is exposed to shear deformation by a rhombus-shaped movement and transfers the deformation to the specimen. This results in a pure shear stress state in the specimen which is not obscured by other stresses such as strain, compression or bending.

"Our shear frame enables specimens several centimetres thick and sandwiched samples with cover layers of fibre composites and a core to be thoroughly checked. One person can operate the experimental setup and the test specimens can be changed in serial tests in just a few minutes. Our test methods have already convinced major clients such as BMW, BASF and REHAU," says Dipl.-Ing. Malte Zur.

The process has been independently verified at BAM. In his doctoral thesis prepared at BAM, Ricardo Basan compared the standardised international (and German national DIN EN ISO 14129) and American (ASTM D 4255, D 7078, D 5379) methods with regard to the effect of shear forces with the shear frame. Dr.-Ing. Basan has shown that the shear frame provides the best and most reasonable results. Shear frame tests have a relatively low scatter of parameters and are applicable for large shear strains. In addition, no complex algorithms are required.

The method was published in January 2014 as a standard DIN SPEC 4885 where DIN SPEC stands for DIN specification. Such standards are developed within a small circle of interested people, making it much faster than the traditional standardisation process. Thus, a faster standardisation process can promote and accelerate the exchange of knowledge and technology transfer where there is a high degree of innovation.