A novel negative stiffness metamaterials: discrete assembly and enhanced design capabilities

Interlocking assemblies have been explored to address large assembly and complex parts and are now integral to additive manufacturing (AM) for creating objects with dissimilar materials and multiple properties. 4D printing technology, which combines smart materials (SMs) with AM, aligns with this approach by enabling the creation of objects that can change shape or properties when exposed to external stimuli. As 4D printing trends towards strategically arranging active and passive materials for improved control and performance, challenges arise due to the limited compatibility of existing 3D printers with the required SM properties. To address this issue, interlocking blocks of dissimilar materials can be printed and then assembled into a desired shape. This work aims to generalize the applicability of the interlocking block assembly approach. This will be achieved by improving the deformation uniformity in a 4D multi-material interlocked assembly. This paper also addresses limitations that can occur due to the interfaces between interlocking blocks, such as lack of deformation and contact continuity. Thus, it will be a question of customizing the shapes of the blocks in the early stages of assembly generation, considering SMs and their potential transformations. Finally, this approach is illustrated with an example, shedding light on the practical implications.

Section: Discussionmentioning

confidence: 99%

Advancing 4D printing through designing interlocking blocks: enhancing deformation uniformity in active composite structures

Benyahia,

Seriket,

Blanquer

et al. 2024

“…The main components of this mechanical metamaterial are beams or shells [52]. The NS behavior is characterized by an increase of compression displacement leading to a load drop, especially usually accompanied by the snap-through behavior caused by the elastic instability [53]. The mechanical metamaterial design of periodic lattices inspired by NS properties achieves desirable dynamic properties [54].…”

Section: Introductionmentioning

confidence: 99%

3D bi-stable negative stiffness mechanical metamaterials for bandgap tuning

Qi,

Zhang,

Hong

et al. 2024

A recent topic of interest in dynamics research is bi-stable negative stiffness (NS) mechanical metamaterials that allow for the efficient control of wave propagation and bandgap (BG) tuning. In this study, a three-dimensional (3D) bi-stable NS mechanical metamaterial based on fan-shaped inclined beams was developed. It has BGs in multiple directions as well as significant bandgap tuning capability in specific direction, and the ability to design for multiple geometrical parameters. First, the requirements for NS mechanical metamaterials to achieve bi-stable properties were theoretically investigated. Subsequently, the deformation process of the unit cell of the metamaterial under uniaxial compression and the band structure and vibrational properties of the metamaterial under different steady states were analyzed through a combination of finite element method (FEM) and experiments. The results showed that the BG range of the bi-stable NS metamaterials in the vertical direction changed with the switching of the steady state, whereas the out-of-plane BG in the horizontal direction remained constant. Therefore, this bi-stable NS mechanical metamaterial could realize modulation of the BG as well as control of wave propagation in multiple directions. In addition, bi-stable NS metamaterials with different angles exhibited different BG ranges. Finally, the vibrational transmittances of the metamaterials were investigated to verify the accuracy of the BG range.

“…demonstrate novel properties not exhibited by most natural and artificial materials. These properties are usually reversal of common senses, such as negative Poisson's ratio [1,2], negative stiffness [3,4], negative swelling behavior [5], and negative refraction [6,7]. Furthermore, some studies demonstrated how to tune or induce the properties of metamaterials after they are manufactured using temperature [8][9][10], magnetic fields [11], air pressure [12], and other methods, thus achieving more diverse applications.…”

Section: Introductionmentioning

confidence: 99%

Reversible negative compressibility metamaterials inspired by Braess’s Paradox

Zha,

Zhang

2024

Negative compressibility metamaterials have attracted significant attention due to their distinctive properties and promising applications. Negative compressibility has been interpreted in two ways. Regarding the negative compressibility induced by a uniaxial load, it can only occur abruptly when the load reaches a certain threshold. Hence, it can be termed as transient negative compressibility. However, fabrication and experiments of such metamaterials have rarely been reported. Herein, we demonstrate them. Inspired by Braess’s paradox, a novel mechanical model is proposed with reversible negative compressibility. It shows multiple types of force responses during a loading-unloading cycle, including transient negative compressibility and hysteresis. Phase diagrams are employed to visualize the relationship between force responses and system parameters. Besides, explicit expressions for the conditions and intensity of negative compressibility are obtained for design and optimization. The model replacement method inspired by compliant mechanism design is then introduced to derive specific unit cell structures, thus avoiding intuition-based approaches. Additive manufacturing technology is utilized to fabricate the prototypes, and negative compressibility is validated via simulations and experiments. Furthermore, it is demonstrated that metamaterials with transient negative compressibility can be activated through electrical heating and can function as actuators, thereby possessing machine-like properties. The proposed mechanical metamaterial and the introduced design methodology have potentials to impact micro-electromechanical systems, force sensors, protective devices, and other applications.