Spallation of alumina ceramic plates under high-energy pulsed laser impact loading

The failure behavior of alumina ceramic plates subjected to high-energy nanosecond pulsed laser irradiation with peak power densities ranging from 10.61 to 31.83 GW/cm² was investigated through combined experiments and numerical simulations. Experimental results show that pulsed laser loading induces two distinct damage modes: the formation of a localized heat-affected zone on the laser-irradiated front surface and spallation damage on the rear surface. Among these, rear-surface spallation caused by the reflection of laser-generated shock waves is identified as the dominant failure mechanism governing the macroscopic structural integrity of the ceramic plates. Three-dimensional surface characterization of the spallation regions reveals that both the spallation depth and lateral extent increase moderately with increasing laser pulse energy. However, when normalized by laser energy, lower pulse energies produce a greater spallation depth per unit energy, indicating higher damage efficiency and highlighting the potential risk associated with repeated low-energy pulsed laser loading on ceramic protective structures. To further elucidate the spallation mechanism, a finite element model was developed to simulate laser-induced stress wave propagation and rear-surface spallation behavior. The numerical predictions show good agreement with experimental observations, with deviations within 15% for spallation depth and 10% for spallation radius. This study clarifies the dominant failure mode of alumina ceramics under high-energy pulsed laser shock loading and provides a quantitative basis for the evaluation and design of ceramic protective structures against pulsed laser threats.