Low‐Cost Fabrication of Re‐Entrant Carbon‐Fiber Auxetic Composites With Continuous and Discontinuous Fiber Performance

ABSTRACT Structures with negative Poisson's ratio hold significant application potential in aerospace and related fields due to their unique auxetic behavior, yet conventional fabrication methods are often costly and complex. To overcome these limitations, this study employs 3D printing to fabricate PLA molds for producing continuous and discontinuous carbon fiber‐reinforced composites with re‐entrant honeycomb architectures. Through systematic tensile testing, scanning electron microscopy (SEM), and finite element analysis (FEA), the mechanical responses and failure mechanisms of the two composite types were comparatively examined. Tensile results show that the continuous fiber specimens (CFS) have a failure strain of 0.74%, and an energy absorption of 0.17 MJ; the corresponding values for the discontinuous fiber specimens (DFS) are 0.68%, and 0.13 MJ, respectively. Compared with DFS, CFS exhibit an approximately 30.8% increase in energy absorption, along with slight improvements in failure strain. The peak stress of DFS (36.79 MPa) is higher than that of CFS (34.15 MPa). Continuous‐fiber composites display multi‐stage load‐bearing behavior, enhanced toughness, and superior energy absorption capacity, with markedly higher stress levels in both the fibers and the matrix compared to their discontinuous‐fiber counterparts. In contrast, discontinuous‐fiber composites demonstrate typical brittle fracture characteristics. Overall, this study provides an effective and low‐cost strategy for the efficient fabrication of high‐performance negative‐Poisson's‐ratio metamaterial structures.