Effect of Curvature Height on the Low-Velocity Impact Behaviour of Unidirectional T300/5208 CFRP Laminated Shell Panels: A Comparative Numerical Parametric Analysis of Intralaminar + Interlaminar and Intralaminar-Only Models

In this study, the 33.5 J low-velocity impact (LVI) behaviour of unidirectional T300/5208 CFRP cylindrical shell panels with a 40-ply [45/0/−45/90]5s layup was investigated using Abaqus/Explicit under the effect of the curvature-height parameter (f = 0–62.5 mm; a1–a6). To address the limitation of the previous single-block approach in not being able to represent delamination, the study was carried out on two models: an intralaminar-only (SC8R single-block) model and an intralaminar + interlaminar model containing nine cohesive interfaces. Quantitative results: In the intralaminar-only model, the maximum contact force peaks at a3 (f = 25 mm), with 13,192 N, representing a 13.7% increase relative to the flat panel; whereas in the intralaminar + interlaminar model, the force is highest at a2 (f = 12.5 mm), with 14663 N, and decreases monotonically with curvature (10,765 N at a6). Failure mechanism: In the intralaminar-only model, the dominant intralaminar mode is matrix tensile damage (DAMAGEMT); in the intralaminar + interlaminar model, interlaminar separation (CSDMG) governs the total damage, and the initiated delamination area reaches its minimum at a4 (f = 37.5 mm), with 7282 mm2, and its maximum at a5, with 9821 mm2. Thus, a curvature-dependent delamination-minimum regime arises that differs from the a3 optimum of the intralaminar-only model. An impact performance index (DPI) and its surface-area-corrected derivative, DPI* = DPI/ζ, were applied separately for both models. It was shown that delamination systematically lowers the performance level and shifts the optimum curvature window. All findings are comparative trends within a single numerical framework.