Prior implementing prototypes on the original scale, preliminary tests on a test specimen scale often prove to be worthwhile. For directly comparable loading conditions and for the resulting increased significance of the scaled tests, they should be carried out with FEA-designed test specimens. In addition, unexpected and undesired types of failure can be detected and prevented in advance.
In this example, the laminate strength under torsional load is to be verified. Due to the high material strength of fibre reinforced composites, only comparatively small wall thicknesses in the cylinder area are usually feasible. The generic diagram (see figure) shows the ensuing insufficient buckling stability in the wall thickness range relevant for the strength verification. The obvious approach to remedy this situation by increasing the wall thickness, for example by circumferential winding, would lead to a distortion of the desired strength value.
Using the materials and components knowhow available at LZS GmbH, a tailored solution could be found. Inspired by bionic approaches, a design with local ring bandages (90° winding) was developed, which enables a considerable increase in buckling stability, even without negative influences on the desired test outcome.
This is just one example of how intelligent test specimen design offers the possibility to ensure correct results in complex, often multi-stage validation tests, thus minimizing time and costs.