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Composite tape springs are curved shells with the ability to assume two energetically stable states. By carefully selecting layup and mold during manufacturing, these structures can store significant strain energy, making them ideal for deployable systems. Yet, their potential as reversible reconfigurable structures, particularly as adaptive hinges, remains largely unexplored. In structural applications, both stable states of these hinges must exhibit high stiffness to support loads while retaining the capacity for reversible reconfiguration. This paper introduces kinematics-based stacking concepts aimed at enhancing the stiffness of bistable hinges in both states, allowing for specific fold angles without compromising compliance. These designs leverage snap-through kinematics, resulting in unique architectures with customizable stiffness and stability. Additionally, the paper presents a novel energy-based semi-analytical approach for analyzing the stacking concepts. This approach involves constrained exploration of the energy landscape to assess the design space in terms of stiffness and energy barriers. Through comprehensive parametric studies, the research demonstrates significantly increased stiffness and reduced peak stresses compared to single tape spring designs. This research highlights the potential of employing tape springs as reconfigurable load-bearing structures in diverse applications, including precise adjustments of low-mass payloads like solar panels or antennas on space structures.

Abstract Multi‐stable elements are commonly employed to design reconfigurable and adaptive structures, because they enable large and reversible shape changes in response to changing loads, while simultaneously allowing self‐locking capabilities. However, existing multi‐stable structures have properties that depend on their initial design and cannot be tailored post‐fabrication. Here, a novel design approach is presented that combines multi‐stable structures with two‐way shape memory polymers. By leveraging both the one‐way and two‐way shape memory effect under bi‐axial strain conditions, the structures can re‐program their 3D shape, bear loads, and self‐actuate. Results demonstrate that the structures' shape and stiffness can be tuned post‐fabrication at the user's need and the multi‐stability can be suppressed or activated on command. The control of multi‐stability prevents undesired snapping of the structures and enables higher load‐bearing capability, compared to conventional multi‐stable systems. The proposed approach offers the possibility to augment the functionality of existing multi‐stable concepts, showing potential for the realization of highly adaptable mechanical structures that can reversibly switch between being mono and multi‐stable and that can undergo shape changes in response to a change in temperature.

Continuous lattice fabrication is a newly introduced method for additive manufacturing of fiber-reinforced thermoplastic composites that allows to deposit material where it is needed. The success of this technology lies in a printing head in which unconsolidated continuous fiber-reinforced composite is pulled through a pultrusion die before the material is extruded and deposited out of plane without the use of supporting structures. However, state-of-the-art composite feedstock like commingled yarns shows limits in achievable material quality and part dimensions due to the underlying fiber architecture where thermoplastic fibers are mingled with reinforcement filaments. Hybrid bicomponent fibers overcome these constraints because each individual reinforcement filament is clad in a thermoplastic sheath. This results in absence of time-consuming fiber impregnation steps that would negatively effect void content and material quality.This study compares the material quality of pultrudates made from hybrid bicomponent fibers to that of commercially available commingled yarns at various processing conditions. Experiments are reported in which polycarbonate composite profiles with a diameter of 5 mm containing 50 vol% to 60 vol% E-glass fibers are pultruded at different die filling degrees, mold temperatures and pultrusion speeds. The results show that the pultrudates obtained from hybrid bicomponent fibers have lower void content than those manufactured under the same conditions from commingled yarns. We assess this to be caused by the difference in consolidation mechanism which in the case of the hybrid bicomponent fibers is dominated by coalescing of the thermoplastic sheaths compared to the Darcian flow-dominated consolidation of commingled yarns.

Abstract 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.

Combining additive manufacturing (AM) with carbon fiber reinforced polymer patched composites unlocks potentials in the design of individualized, lightweight biomedical structures. Arising design opportunities are geometrical individualization of structures using the design freedom of AM and the patient-individual design of the load-bearing components employing carbon fiber patch placement. To date, however, full exploitation of these opportunities is a complex recurring task, which requires a high amount of knowledge and engineering effort for design, optimization, and manufacturing. The goal of this study is to make this complexity manageable by introducing a suitable manufacturing strategy for individualized lightweight structures and by developing a digitized end-to-end design process chain, which provides a high degree of task automation. The approach to achieve full individualization uses a parametric model of the structure which is adapted to patients’ 3D scans. Moreover, patient data is used to define individual load cases and perform structural optimization. The potentials of the approach are demonstrated on an exoskeleton hip structure. A significant reduction of weight compared to a standard design suggests that the design and manufacturing chain is promising for the realization of individualized high-performance structures.