Auxetic Composite Sandwich for Vibration Damping Through Axisymmetric Deformation

External undesirable vibrations from the environment can affect the performance of vibration-sensitive equipment. Passive isolators are simpler, lighter, and cheaper, and constrained layer damping is a low-cost yet effective method of vibration dampening. Traditional methods of improving constrained layer damping include increasing the number of layers or directly connecting one end of the constraining layers to the base structure. The drawback of these methods is the requirement to increase the overall thickness. Also, like most passive isolators, it has a limitation on stability, which is usually solved by external mechanical limiters. The novel concept of an auxetic composite sandwich addresses both issues of having an external limiter by using the constraining layer for load bearing and enhancing damping performance without increasing the overall thickness, achieved through an auxetic interlayer and deforming axis-symmetrically. The rotating triangle auxetic interlayer is selected based on biomimicry of animals that endure impact and pressure, such as cranial sutures, beaks, ammonoid and turtle shells. Finite element analysis shows significantly higher damping ratio at the beginning of free vibration, and experiment results show an eightfold increase in damping ratio (from 0.04 to 0.29). Additionally, settling time to 0.25 g is reduced from 70.7 ms to 60.9 ms as acceleration is increased from 0.5 g to 4 g. Power spectrum density shows better attenuation, three to four times better than the plain model. The successful demonstration of the concept motivates further study to understand the performance of auxetic patterns in enhancing constrained layer damping.