Optimal composite structures in the forewings of beetles

In order to develop optimal biomimetic composite structures, research was conducted on the structural characteristics of Allomyrina dichotoma beetle forewings, with these characteristics to be further expounded upon. From this research, the following results were obtained: (1) It is found that the males, in comparison to females have both lighter and thinner forewings with a lower tensile fracture force, with the biological reasons behind these differences to be discussed later in depth. (2) It was found that densely distributed chitin fibers are located around the void lamination in the endocuticle of the forewing. They were found to have a rectangular cross-section with maximum reinforcement of fiber volume fraction; likewise, there exist sparsely distributed ones on the exocuticle in the Epipleuron tip of the forewing. These are of a circular cross-section, with a protein matrix that provides strong reinforcement. (3) Macroscopically the chitin fibers appear to exist independently of each other. However, this research discovered that, microscopically, the fibers have a reticular structure and through this structure, provide two-dimensional reinforcement to the same lamination of fibers. In comparison to a cloth weaving, it has many advantages, such as being unbendable and lacking concentrated stress points by crossing between the fibers, because they are not weaving cross points with those fibers. Lastly, the schematic structural model of the reticular structures of the fibers was proposed.