Compression resistance of CFRP/mater fractal nested structures based on self-similar fractal strategy

The plastic deformation of metallic structures is promising to improving the load-bearing instability of carbon fiber-reinforced polymer (CFRP) thin-walled structures. Therefore, this study proposes a novel self-similar fractal strategy of CFRP/stainless steel nested structure to fully exploit the mechanical advantages of distinct materials. The structure consists of an outer quadrilateral CFRP tube nested with an internal stainless-steel fractal substructure, named the Quadrilateral Fractal Nested Structure (QFNS). Through the compression test, it is found that the CFRP/stainless steel nested structure has more stable mechanical loading behavior compared with the pure metal structure. Numerical simulations further explored the energy contribution mechanism, which reveals that the load-bearing capacity of QFNS surpasses the combined performance of its individual components, emphasizing the significant interaction effect between internal and external structures. In addition, the fractal order, the number of paving layers and the fractal wall thickness significantly affect its crashworthiness. In particular, when the fractal order increases from 0 to 2, the specific absorption energy increases (SEA) by 122.97 %. Moreover, compared to typical CFRP/metal structures, the self-similar fractal design elevates SEA by 110.39 %. This study provides a cost-effective, lightweight solution with simplified assembly for designing high-performance protective structures.