Design of Compliant Structures with Tunable Mechanical Properties

Compliant mechanisms have long been embraced by nature to achieve the remarkable adaptability and efficiency inherent in biological systems. Instead of relying on rigid joints between bodies in conventional mechanisms, compliant mechanisms transfer motions and forces through the flexible members. Recent advancements in manufacturing technologies have made it possible to produce intricate geometries with exceptional precision across various length scales. This confluence of highly precise manufacturing capabilities and the demonstrated effectiveness of compliant mechanisms has provided a compelling impetus for researchers to pursue the development of biomimetic designs tailored for engineering applications. Nonetheless, the excellent flexibility of compliant structures presents a noteworthy concern in civil engineering given that a requisite level of strength and resilience are required in the construction industry. This research investigates the capability of a promising construction material, carbon fibre reinforced polymer, in designing compliant structures. From nature-inspired fractal patterns to simple beam elements, the compliant mechanisms are achieved in a controllable manner, i.e., reversibility and multi-stability. Snap-through behaviour, which characterises the compliant mechanisms in this study, is thoroughly investigated and accurately predicted. Considering that compliant structures in nature predominantly have a multi-material composition, preliminary investigations into the utilization of multiple materials in compliant structures are also conducted to explore their potentially enhanced performance. This work highlights the effectiveness of the inclined beam element in achieving compliant behaviours, with contour maps provided for design guidance. It is also emphasized that the transition between controlled compliant mechanisms (reversibility and bi-stability) could be realised by tuning the beam geometry, beam arrangement, and boundary conditions of the curved beams. This work also demonstrates the resilience and robustness of compliant structures fabricated with carbon fibre reinforced polymer, regardless of manufacturing defects, misaligned loading conditions, and undesired boundary conditions. This research contributes to an addition to the existing body of knowledge regarding compliant mechanisms and offers insights into prospective applications of compliant structures in the civil engineering field.