Testing 3D Printed Carbon Fiber Durability for Next‐Gen Fusion Reactors via Proton Irradiation

ABSTRACT Carbon fiber‐reinforced composites are promising candidates for plasma‐facing components (PFCs) in next‐generation fusion reactors due to their high strength‐to‐weight ratio, thermal stability, and radiation resistance. However, the effect of high‐energy proton irradiation on the mechanical and structural integrity of 3D‐printed carbon fiber composites remains underexplored. This study investigates the nanomechanical behavior and microstructural evolution of 3D‐printed continuous carbon fiber (CF) composites exposed to proton irradiation at fluences of 5 × 10 ¹⁵ , 1 × 10 ¹⁶ , and 5 × 10 ¹⁶ ions/cm ² using a Pelletron tandem accelerator. Nanoindentation experiments were conducted at varying loading rates (0.1–0.6 mN/s) to evaluate changes in hardness, elastic modulus, shear stress, and contact pressure. Raman spectroscopy was used to analyze defect evolution via shifts in the D, G, and 2D bands. Results show an initial softening at lower irradiation doses followed by hardening at higher fluences, attributed to defect accumulation, localized amorphization, and structural densification. A strong correlation was established between the I _D / I _G ratio, crystallinity proportion, and nanomechanical properties. Numerical modeling and regression analyses supported the experimental findings. This work provides new insights into the irradiation response of 3D‐printed CF composites and demonstrates the viability of Raman spectroscopy as a non‐destructive diagnostic tool for monitoring radiation‐induced damage in fusion‐relevant materials.