XCT-Visible Marker Tapes for Tape-Level Flow Tracing in Sheet Moulding Compounds

Carbon fiber reinforced thermoplastic sheet molding compounds (CFRTP-SMCs) consist of short, thin tapes that undergo complex rearrangement during compression molding, forming dense, randomly distributed architectures that critically influence the final mechanical performance. However, once consolidated, it becomes extremely difficult to distinguish and trace individual tapes using conventional X-ray computed tomography (XCT), which relies on indirect inference from local fiber orientation differences. To address this limitation, this study introduces a direct visualization strategy based on marker tapes, comparing three candidates—conductive paint (silver-copper-based), copper foil tape, and aluminum foil tape—in terms of X-ray attenuation, adhesion, and visualization performance. The three markers exhibited distinct attenuation characteristics: copper foil showed the highest absorption, conductive paint moderate, and aluminum foil the lowest. Despite its moderate attenuation, conductive paint adhered firmly to the tape surface, preserved flexibility during molding, and provided continuous, deformation-responsive markings, enabling reliable visualization of tape flow and distortion. Among the tested options, conductive paint proved the most practical and effective marker for tape-level tracing. The proposed multi-marker approach opens a pathway to analyze macroscopic tape rearrangement and deformation, bridging process parameters with tape distribution in SMCs.