A non-linear stiffness composite twisting I-beam

A classic structural component of mechanical engineering, the I-beam, is re-designed by adding a morphing twist functionality to the high bending stiffness inherent to the geometry of the component. The beam, as with its conventional counterpart, is made of two flanges separated by a web. Here, bi-stability is introduced from a combination of flange pre-stress, web geometry and material properties, yielding a highly non-linear twist morphing structure while keeping the low weight and the high bending stiffness of the beam. The present case study offers two twisted stable shapes and can be morphed from one stable configuration to the other by applying a snap-through twist moment to the ends of the structure. Correlation is found between tests results, finite element model data and analytical predictions, validating the modelling assumptions. A sensitivity study is also performed to understand the influence of the design parameters of the beam and loading condition on the stability of the structure. As a result, the three conflicting requirements of adaptive structures are met in a single structural entity: low mass, load-carrying capability and compliance.