3D printed bio-inspired self-similar carbon fiber reinforced composite sandwich structures for energy absorption

Fractals widely found in nature possess amazing simple shape cell yet infinitely complex macrostructures. Importantly, all fractals manifest a degree of self-similarity that provides new structural design strategy for composite materials. At present, enhancing energy absorption capacity of lightweight carbon fiber reinforced composite structures is critical for their further engineering applications, and meanwhile biomimetic structures have demonstrated excellent mechanical properties compared to conventional engineering structures. In this work, we constructed bio-inspired fractal structures through three fundamental shape units (curve, circle, and hexagon), and investigated nonlinear mechanical responses of hierarchical self-similar structures inspired by snake-like serpentine, bamboo, and honeycomb, having distinct structure ratios related to cell sizes at different geometry levels. Firstly, such self-similar structures were fabricated into homogenous ones by 3D printing for assessing the energy dissipation contribution of polymer matrix. Moreover, the selected self-similar carbon fiber reinforced composites were additively manufactured and their energy absorption mechanisms of composite sandwich structures were studied via experiment and numerical methods. Additionally, the influences of the self-similar types, structure ratios, and cellular scales on nonlinear compressive behaviors of self-similar composite structures were investigated in detail. The results indicated that the fractal bamboo composite components with the structure ratio of 0.2 exhibit the highest energy absorption rates, with a satisfactory level of energy absorption capacity in potential engineering applications. This study can provide a useful reference in the field of biomimetic fractal design of fiber reinforced composite structures by 3D printing technique.