5. Conclusion
In the present paper we investigated the geometric non-linear behavior of corrugated laminates in six different loading situations. In load case 1, 3, and 4 we found that material strength is exceeded before geometric non-linearities can occur. All the non-linear stiffness curves show a very progressive behavior with a knee where the stiffness changes. For load case 2, tensile loading in ydirection, the stiffness response is highly non-linear due to large deformations. In load case 5, bending about the x-axis, the stiffness remains linear until self-contact between the unit-cells occur. At this point the stiffness increases. In load case 6, the large deformations also resulted in geometric non-linearities. Due to its complexity load case 6 was investigated numerically and experimentally. The experiments are very robust and reproducible and agree very well with the FE simulation. We observed that the qualitative non-linear stiffness response mainly depends on the corrugation amplitude. These results can be used in design processes where large deformations might occur, such as morphing wings, to estimate whether linear modeling is sufficient or geometric non-linearities have to be considered. We can conclude that non-linearities have to be taken into account for structural materials in load case 2 and 6, and in load case 5 if self-contact occurs. To increase the applicability for design purposes, we plan to model combinations of the different load cases and conduct parametric studies in future work.
