Constitutive behaviour of paddlefish (Polyodon spathula) cartilage

This study explored the constitutive behaviour of the midline cartilage of the paddlefish (Polyodon spathula) rostrum and examined the properties of the cartilage as a function of stress state and strain rate. The cartilage structure of the paddlefish contributes to the physical characteristics of the unique rostrum, and is of much interest as an inspiration for engineered structures. Low-strain rate testing (∼0·01/s) results indicated an average compressive yield stress of 11·34 ± 3·10 MPa and an average tensile yield stress of 3·62 ± 0·62 MPa. High-strain rate testing (∼100/s) results showed an average compressive yield stress of 25·07 ± 10·86 MPa. A histological study showed that the material is a type of hyaline cartilage. An Ogden hyperelastic model was used for finite-element analysis and fit very well with experimental data. This paper contributes to an overall study examining the electrosensory capabilities, hydrodynamics and structure–property relationships of the rostrum.