The Super Tough Saddle of Mantis Shrimp Derived from Strain Transformation Between Helical Fibers and Interlaminar Fibrils

Mantis shrimps deliver one of the fastest strikes with their powerful dactyl clubs. The kinematic energy derived by a saddle storing and releasing mechanical energy with large deformation. As an exoskeleton, the toughness of saddles can achieve a remarkable value approximate to 15.28 +/- 2.32 MJ m-3, which exceeds most bulk natural materials. The excellent toughness of saddles is mainly attributed to the synergy of the helical mineralized fiber architectures and interlaminar fibrils. The interlaminar fibrils connect adjacent mineralized fiber layers closely, enhancing the toughness through viscoelastic deformation during sliding and separating of adjacent layers. They further cooperate with rigid interlacing fiber structure induced by helical structure to transform little normal strain to large shear strain utilizing incompressibility of soft fibrils further to enhance strain energy for toughening. Inspired by unique laminated saddles, the laminate composites are designed with basalt fabrics achieving remarkable fracture toughness to solve the problem of delamination in traditional laminate composites with poor interlaminar toughness. The Mode I and Mode II interlaminar fracture toughness of bio-inspired laminate composites respectively increase by 44% and 118% reaching 906.8 and 1394.6 J m-2, which provides an innovative bionic strategy for designing new generation structural engineering materials with excellent mechanical properties. The unique structures in the saddle of mantis shrimp transfer little normal strain into large shear strain, achieving excellent toughness through the synergistic effect of rigid mineralized fiber and viscoelastic Interlaminar fibrils. Corresponding bio-inspired designs can be used in laminate composites for toughening.image