Stiff morphing composite beams inspired from fish fins.

Area of Science:

• Materials Science
• Bioinspired Engineering
• Mechanical Engineering

Background:

• Traditional morphing materials are either highly compliant with large shape changes or stiff with limited shape changes requiring significant force.
• Fish fins achieve precise, rapid shape changes and generate large hydrodynamic forces without collapsing, despite lacking muscles.

Purpose of the Study:

• To develop a stiff morphing beam inspired by fish fin rays.
• To investigate the nonlinear mechanical behavior and design principles of these bioinspired structures.

Main Methods:

• Fabrication of synthetic rays using acrylic (PMMA) outer beams and compliant rubber ligaments.
• Experimental testing and computational modeling to analyze geometric nonlinearities and stability.
• Exploration of variable ligament densities to optimize morphing capabilities.

Main Results:

• Demonstrated that rubber ligaments are mechanically "invisible" at small deformations but delay buckling and enhance stability at large deformations.
• Identified strong nonlinear geometrical effects governing the morphing behavior.
• Generated design guidelines for optimal morphing shape, balancing compliance and flexural stiffness.

Conclusions:

• The developed synthetic rays exhibit enhanced stability and controlled morphing, inspired by natural fish fins.
• The design guidelines facilitate the creation of stiff, bioinspired morphing structures.
• Potential applications include aerospace, biomedicine, and robotics.