Passive spanwise bending shape-adaption has the potential to increase the efficiency and manoeuvrability of vehicles with wing-like structures. By utilisation of compression flange buckling, the in-plane stiffness can be tuned to design beams with contrasting pre-buckling and post-buckling bending stiffness. The investigated concept is experimentally validated using a thin-ply laminated composite four-point bending beam, which is designed to experience compression flange buckling in the span with constant moment. The bending stiffness was reduced by more than 41% after the onset of buckling which shows the effectiveness of compression flange buckling for non-linear bending compliance.

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Passive spanwise bending shape-adaption has the potential to increase the efficiency and manoeuvrability of vehicles with wing-like structures. This paper presents a passive spanwise bending shape-adaption concept for highly loaded wing-like structures based on local buckling of the compression flange at a prescribed external bending moment. Buckling reduces the in-plane stiffness of the compression flange and thus yields a beam design with a high prebuckling and a low postbuckling bending stiffness. The investigated concept is experimentally validated using a composite four-point bending beam, which is designed to experience compression flange buckling between the load introductions. The point of buckling is at 374.80 Nm, and ultimate failure occurred in the experiment at 524 Nm, which results in a postbuckling range of 149.2 Nm. The bending stiffness was reduced by more than 41% after the point of buckling which shows the effectiveness of compression flange buckling for nonlinear bending compliance. This proof of concept has demonstrated for the first time, that compression flange buckling is a viable structural concept for highly loaded composite beam structures to achieve nonlinear bending compliance.

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The damping behaviour of continuous carbon fibre and flax fibre reinforced polymer (CFRP and FFRP) composites was studied by comparing angle-ply laminates. Using logarithmic decrement measurements, dynamic mechanical analysis and vibration beam measurements, the damping was described as the specific damping capacity ψ in order to compare data using the different methods. Our results show approximately 2–3 times better damping of FFRP compared to CFRP at low frequency and low strain. We show that the damping of both materials increases with increasing angle-ply orientation below 300Hz. While the matrix and interface seems to contribute mainly to damping at lower frequencies, the fibre shows an increasing contribution with ψ = 64.4% for unidirectional FFRP at 1259Hz in the 5th mode of vibration, without a notable change in the elastic modulus. This work demonstrates that the FFRP may be simultaneously stiff and efficient at damping.

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The objective of this paper was to understand the damping of carbon- and flax-fibre reinforce polymers. We analysed carbon and flax symmetric angle ply laminates for a series of layup angles of 0°, ±10°, ±20°, ±30°, ±60°, 90°. We measured both series using dynamic mechanical analysis (DMA) and vibration beam measurements (VBM). Our results showed that the VBM and DMA elastic results can be converted from one into the other, and we found a mathematical formulation to relate the damping results of both. We discussed the underlining mathematical models of each measurement method and the physical interpretation. For both methods, we relate the elastic properties to the elastic modulus and the damping properties to the specific damping capacity (SDC), ψ. We concluded that within a certain frequency range micro-mechanical (DMA) and macro-mechanical (VBM) damping may be compared and even converted into one another.@en