Bioinspired multifunctional lightweight engineering solutions for noise control applications

Mostafa Ranjbar explains how learning from the naturally architectural cellular structures of woodpeckers’ beaks, dragonfly wings, bones and trees help to develop lightweight materials for noise and vibration mitigation applications in aerospace and automotive applications.

By Mostafa Ranjbar, Lecturer in Mechanical Engineering, Faculty of Engineering and Natural Sciences, Cranfield University

The geometry of cellular structures can be engineeringed to provide extraordinary mechanical properties and multifunctional features in materials, which can filter and reduce the harmful travelling mechanical/acoustic waves over wide frequency ranges.

The cellular structures of the woodpecker beak, dragonfly wings, bones and trees have common lightweight characteristics with significant tuneable mechanical properties and by learning from these natural structures, we could develop practical solutions for noise and vibration mitigation applications. The internal geometry of the cellular structures can be designed to provide a tuned mechanical stiffness distribution and mitigate the travelling vibration and acoustic waves while their total mass and original materials remain unchanged. Furthermore, fast 3D printing of such structures provides an extra advantage.

Above: Adjusting the internal geometry of a honeycomb cell can reduce its noise radiation

Back to nature
In one of our projects at Cranfield University, we developed lightweight sandwich panels with architecturally designed cellular cores, which helps to emit less noise from trains, aircraft and cars into the surrounding medium.

The lightweight cellular structure of a woodpecker’s beak is naturally designed to filter the imposed impact waves generated while the bird is drilling into trees by preventing the harmful vibration transmission into its brain. We used this mechanism to develop lightweight vibration dampers.

Above: Bioinspired phononic vibration dampers

In another work, we learned from the structure of the dragonfly wing to develop multifunctional lightweight cellular structures, which could manipulate the emitted noise while enhancing the flyability and energy consumption features of aircraft wings.

Above: Bioinspired lightweight structure for multifunctional noise control applications