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Shape transformation offers the possibility of realizing devices whose 3D shape can be altered to adapt to different environments. Many applications would profit from reversible and actively controllable shape transformation together with a self-locking capability. Solutions that combine such properties are rare. Here, a novel class of meta-structures that can tackle this challenge is presented thanks to multi-stability. Results demonstrate that the multi-stability of the meta-structure is strictly tied to the use of highly anisotropic materials. The design rules that enable large-shape transformation, programmability, and self-locking are derived, and it is proven that the shapes can be actively controlled and harnessed to realize inchworm-inspired locomotion by strategically actuating the meta-structure. This study provides routes toward novel shape adaptive lightweight structures where a metamaterial-inspired assembly of anisotropic components leads to an unforeseen combination of properties, with potential applications in reconfigurable space structures, building facades, antennas, lenses, and soft robots., Advanced Science, 9 (26), ISSN:2198-3844

Airbus is working on various technologies to make future A/C more sustainable. One of them are disruptive, more efficient, wing designs comprising i.a. adaptive structures inducing the need for new materials & processing technologies. Together with ETH Zurich thin ply CFRTPs are investigated for damage tolerant mechanical hinges. Investigations include interaction of processing and mechanical performance. Novel, highly controlled processing method for the TP-CFRTP are presented.

Fibre-matrix interface performance is essential in fibre reinforced polymer composites, leading to important efforts in quantification and optimization. This is even more relevant for thermoplastics, since interfacial bonding happens only via physical interactions. Standardised mechanical tests provide homogenized composite properties, but fail to isolate the contribution of the interface. Micromechanical ones are designed for this exact purpose, but need complex set-ups and sample preparation. This study adopts a novel multiscale approach to measure mechanical properties of polycarbonate-glass fibre composites, manufactured under different interfacial conditions (sized & desized). This is enabled by use of focused ion beam in precise manufacturing and post-mortem analysis of specimens. The results show an evident difference between tested conditions at the macroscale (mode I), where sized specimens outperform desized ones. At the microscale (mode II), these differences are less pronounced due to the high ductility of the matrix resulting in a cohesive failure of the composite., Proceedings of the 20th European Conference on Composite Materials: Composites Meet Sustainability, ISBN:978-2-9701614-0-0

The concept of shape-morphing is to embed control in a design to broaden its band of functionality. Whether it is for cars, planes, buildings, or personal medicine, the goal is to achieve more with less. That is more efficiency, more functions, more force, and more range with less energy, and less weight. The design of these new types of structures is however complex, as all the variables of a system are intertwined. Existing designs are either simple or small to reduce the number of design variables, although this affects the achievable deformation range of a structure. There is a need for a design method that can handle the complexity of the search space of shape-morphing structures without compromising the breadth of their design space or the accuracy of their deformation. This thesis proposes four design methods, one for compliance-controlled shape-morphing and three for actuator-controlled shape-morphing. First, compliance-control is achieved through optimization of the distribution of materials with varying stiffness in a 2D lattice structure. The method is implemented for geometric and material linearity and nonlinearity to observe how the choice of model affects the accuracy of the deformations. The method is verified by optimizing the material distribution for a 2.5D NACA target shape and replicating the results experimentally using multimaterial 3D printing. Then, the modeling and four fabrication methods for soft pneumatic actuators are compared, as they are necessary to experimentally verify the actuator-controlled shape-morphing methods. The final actuator design is adapted to the constraints of soft lithography, the fabrication method that delivers the most robust and predictable actuators of the four. Actuator-control is achieved by optimizing the actuator layout within a lattice structure with the aim of achieving a target deformation. The three methods show how reducing the search and design space of a structure improves the computational efficiency and accuracy for 2D, 2.5D, and 3D deformation. The first method assumes static and kinematic determinacy and small displacements; the second assumes small displacements in overdeterminate structures; the third can achieve large shape changes in overdeterminate structures. All three methods are verified through finite element analysis and experimentally. Finally the implications of the findings related to the four shape-morphing design methods are discussed. The achievable search and design space of each method are compared. The designer is free to chose the method best adapted to their needs, as each one is a compromise of accuracy, range, and computational efficiency. The methods can be employed for different types of actuation, but their application to industrial fields is hindered by the mechanical properties of the material that can currently be 3D printed. The advent of several new manufacturers of compliant and multimaterial 3D printers promises further industrial developments for the field of shape-morphing.