Array-phase controlled thermal wave diffraction tomography: quantitative delamination assessment in carbon fiber/bismaleimide composites

Carbon fiber/bismaleimide (CF/BMI) composites have emerged as important lightweight structural materials, yet their susceptibility to internal defects such as delamination degrades mechanical properties. Existing non-destructive methods lack quantitative defect morphology characterization capabilities for CF/BMI composites. To address these limitations, an array-phase controlled thermal wave tomography approach is presented, which enables reliable detection and three-dimensional visualization of hidden damage. First, by conceptualizing thermal diffusion as a pseudo-wave phenomenon derived from point-source excitation theory, a thermal wave diffraction tomography (TWDT) model was developed. Subsequently, the optimal Tikhonov regularization parameters were determined through numerical simulations to ensure solution stability in model inversion process. Next, a laser-array thermal wave imaging system was developed to experimentally validate the methodology using CF/BMI composite laminates containing simulated delamination. Results demonstrate exceptional performance, including 0.1 mm depth resolution, 4.38 % lateral size average relative errors for diameter 0.5 ∼ 5.5 mm defects, and 90 % probability of detection at diameter-to-depth ratios exceeding 1.73, Furthermore, compared with traditional lock-in thermography and pulse thermography, TWDT improves the signal-to-noise ratio of defect detection by 23 % and 74 %, respectively, demonstrating superior quantitative characterization capability for composite health monitoring.