Research on 3D printing and mechanical behavior of continuous-fiber reinforced C/SiC composites with negative Poisson’s ratio

Auxetic structures exhibit exceptional fatigue resistance and energy absorption capabilities, demonstrating significant application potential in aerospace engineering. This study proposes an innovative strategy combining continuous fiber 3D printing with polystyrene cross-linking, which effectively improves the shape stabilization of continuous carbon fiber preforms with complex geometries. This approach achieved an 82 % enhancement in the mechanical performance of C/SiC composites (increasing from 172.6 ± 11.2 MPa to 314.1 ± 13.7 MPa). Additionally, the compressive properties of auxetic C/SiC composites were investigated, with particular focus on the effect of compression-compression fatigue cycles on their performance. Intriguingly, the compressive strength of auxetic structures demonstrated a paradoxical increase with accumulating fatigue cycles, accompanied by a pronounced yielding during loading. This anomalous behavior primarily stems from the formation of concentric micro-defects in the pyrolytic carbon interphase surrounding fibers during cyclic loading. These microstructural features facilitate hierarchical fiber pull-out mechanisms, thereby promoting pseudo-ductile fracture behavior and the observed yield phenomenon. The above findings provide new insights for the design of fatigue-resistant ceramic composite structures for aerospace applications.