Temperature effects on the fracture resistance of scales from Cyprinus carpio

In this investigation the fracture resistance of scales from Cyprinus carpio was evaluated as a function of environmental temperature. Tear specimens were prepared from scales obtained from three characteristic regions (i.e. head, mid-length and tail) of multiple fish. The fracture resistance was characterized in Mode III loading and over temperatures ranging from -150°C to 21°C. Results showed that there was a significant reduction in tear resistance with decreasing temperature and the lowest resistance to fracture was obtained at -150°C. There was a significant difference in the relative tear toughness between scales from the three locations at ambient conditions (21°C), but not below freezing. Scales obtained near the head exhibited the largest resistance to fracture (energy ≈ 150 ± 25 kJm(-2)) overall. The fracture resistance was found to be primarily dependent on the thickness of the external mineralized layer and the number of external elasmodine plies, indicating that both the anatomical position and the corresponding microstructure are important to the mechanical behavior of elasmoid fish scales. These variables may be exploited in the design of bioinspired armors and should be considered in future studies concerning the mechanical behavior of these interesting natural materials.