Effect of thickness-to-radius ratio on the impact response of fabric-reinforced composite shells

• The dynamic response of composite shells is significantly influenced by the thickness-to-radius ratio ( t/R ). • Identified a critical t/R ratio marking the transition between thick- and thin-walled shell behaviour. • Intralaminar damage dominates energy dissipation in thick-walled shells, while delamination and friction dominate in thin-walled shells. • Compact and localized damage in thick-walled shells versus extensive, cross-like propagation in thin-walled shells. This study analyses the effect of thickness-to-radius ( t/R ) ratio on the dynamic response of fabric-reinforced composite shells subjected to low-velocity impact loads using 3D finite element models validated by experimental results. Focus is given to the t/R ratio's influence on energy dissipation and damage modes. For thick-walled shells ( t/R > 0.05) the peak force and contact time increases as the curvature decreases (i.e., with a larger radius), while the maximum displacement decreases. On the other hand, thin-walled shells ( t/R < 0.05) exhibit lower peak forces, larger displacements, and longer contact times as the curvature decreases. This transition indicates the existence of a critical point around the radius of 50 mm ( t/R = 0.05). The main mechanism for energy dissipation in thick-walled shells is intralaminar damage, and its contribution decreases with increasing radius, whereas for thin-walled shells, friction and delamination determine the absorption of impact energy. In terms of damage propagation patterns, thick-walled shells show localized intra- and interlaminar damage, while thin-walled shells evidence a cross-like intralaminar pattern with more extensive delamination.