Comparison of the Morphology,Structures and Mechanical Properties of Teleost Fish Scales Collected from New Zealand

The mechanical properties and structures of fish scales have generated considerable research interest,however,comparative studies for different fish scales from difl^rent water regions have not been reported.In this paper,the surface morphologies,hierarchical structures and mechanical properties of four kinds of fish scales collected from freshwater,shallow sea,and deep sea in New Zealand are investigated.The results indicate that the surface morphologies of those fish scales are similar at ventro-lateral,dorso-lateral and anterior locations,and the hierarchical structures of those fish scales all consist of two layers:a bone layer and a collagen layer composed of collagen fibrils.However,the spiral angles of the collagen lamellaes of different scales are different.The largest are Mugil cephalus scales,while the smallest are Cyprinus carpio scales.Comparing the mechanical behaviors of those fish scales,the tensile strength of Carassius auratus scales is the largest,but the ductility is the lowest.Pristipomoides sieboldii scales have the best ductility.Further,the relationship between hierarchical structures and mechanical properties of fish scales is discussed.It is found that the spiral angles of the collagen lamellaes and bond/collagen thickness ratio both have a great influence on the mechanical properties of fish scales.

Structure, Mechanical Behavior and Puncture Resistance of Grass Carp Scales

This work is conducted to investigate the hierarchical structure, mechanical behavior and fracture resistance of grass carp scales with different water contents （hydrated and dehydrated） and load conditions （uniaxial, biaxial and punch tests）. The whole cross-section of scales is investigated, and it is found that the bony layer displays discontinuity and partly embeds in collagen layer. Four different locations are considered under both tensile and punch tests. The results of the uniaxial tensile test show a correlation between the failure mode and the distribution of surface morphology on scales. The biaxial test results show that there are minor differences in the tensile strength and the Young＇ modulus compared with those of the uniaxial tests, but the ultimate strain is about 20% - 50%. Puncture tests are also conducted with different size of needles and different hardness silicon rubbers as substrate. The results show that the puncture force and deformation are dependent on the size of needle and the hardness of substrate. The failure pattern of scales is related to the water content. Radial cracks occur in the bony layer of hydrated scale, and the collagen fibers twist around the puncture site. However, the shear failure occurs in the bony layer of dehydrated scale.