An experimental investigation on mechanical properties of 3D-printed bio-inspired sandwich panels based on silk cocoon geometry

The silkworm cocoon is a hierarchical structure with multiple functions that have evolved over millions of years to create optimal metamorphosis conditions and preserve insect life against predators. In this paper, inspired by the structure of a silkworm cocoon, the cores of two types of lattice sandwich structures were redesigned. For this purpose, the straight struts in the body centered cubic structure and the kagome structure were replaced by curved struts. Due to the complexity of geometry and high dimensional accuracy, three-dimensional printing (digital light processing) was used to construct the designed lattice structures. In this method, the part is made directly from its surfaces' geometric data, which has been designed with the help of a computer, layer by layer, using optical curing resins. After the fabrication of the parts, a quasi-static pressure test was performed on the samples. The results showed that the modified structures are capable of larger deformation without failure, and their energy absorption is uniform. Although modified structures have a lower modulus of elasticity and energy absorption, larger elastic strain and gradual failure of these structures are important advantages that can be considered in various applications such as energy absorbers or nonstructural medical implants.