Damage response of ECC plates under different loading sequences of blast and fragment

This study numerically investigated the damage response of ECC plates with different thicknesses subjected to blast and fragment loading under different sequential loading conditions. Particular attention was given to the effects of loading sequence and plate thickness on structural response and damage evolution. The results showed that increasing ECC thickness significantly improved resistance against combined loading. The 10 mm ECC plate maintained integrity only under single fragment loading, while fragmentation failure occurred in all loading conditions involving blast. Under single blast loading, the 20 mm ECC plate mainly exhibited global bending deformation without perforation, with limited local damage on the rear surface. The 40 mm ECC plate maintained good overall integrity under all loading conditions. Different loading conditions produced distinct failure characteristics. Single blast loading mainly caused global deformation, whereas single fragment loading induced pronounced localized damage. Under sequential combined loading, the initial loading condition significantly affected the subsequent damage response. For the ”blast–fragment” condition, initial blast loading caused central bending deformation in the 20 mm ECC plate, and subsequent fragment impact led to perforation. The front and rear surface damage areas increased to 829.2 mm2 and 2560.4 mm2, respectively, compared with 669.7 mm2 and 1392.1 mm2 under single fragment loading. Under the ”fragment–blast” condition, initial perforation by fragment impact was followed by further enlargement of the damaged region under blast loading, resulting in damage areas of 1778.6 mm2 and 3367.8 mm2. Overall, the ”fragment followed by blast” condition produced more severe damage than the ”blast followed by fragment” condition.