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Prestressed shells with tailored multistable behavior

Aerodynamic surfacesBistabilityMorphing structuresMultistable shellsParametric-adaptive surfaces

Introduction

The invention concerns shells structures with controlled bistable behaviour. This kind of structures can drastically change their configuration depending on the applied load without the need of actuation. The threshold velocities, along with the stable equilibrium configurations and their shapes, can be designed to fulfil the specific application requirements.

Technical features

We propose a method for fabricating a shell (composite materials, laminated and anti-symmetrical laminate) having more stable equilibrium configurations, the shapes of which are established on the basis of the operational conditions, in correspondence with a specific range of values of the applied load. As the external conditions change, the shell changes its shape autonomously, so as to maximize its aerodynamic performance. This behaviour is obtained by imposing a prestress field, induced by flattening and clamping a part of the shell boundary; for shells of rectangular planform, one of the short sides. The prestress depends on a set of parameters which describe the shell initial shape and the material. The method allows to choose such parameters so as to obtain the prestress that guarantees the desired multi-stable behaviour.

Possible Applications

  • Civil engineering (e.g. in the construction of building envelopes and adaptive ventilation systems);
  • Industrial engineering (e.g. in the realization of aerodynamic and shape control appendages), reliable and economical solution.

Advantages

  • Shell spontaneously adaptable to shape based on the applied load, maximising structural efficiency;
  • Actuation energy provided by the load acting on the shell (no need to use actuators);
  • Once the load has been removed, the shell recovers its initial shape without external intervention;
  • Design of all the parameters that define the equilibrium path.