Blast resistance and energy evolution characteristics of high-strength steel/AFRP composite plates under close-in blast loading

The dynamic response, damage characteristics, and energy evolution of high-strength steel/aramid fiber-reinforced polymer (AFRP) composite target plates under close-in blast loading are important for understanding blast-resistance enhancement mechanisms and improving structural protective performance. In this study, close-in blast tests were conducted on Q460 high-strength steel/AFRP composite plates with different AFRP backing thicknesses. A single-camera stereo three-dimensional digital image correlation system was used to measure the full-field transient out-of-plane deformation of the rear surface, while three-dimensional scanning was employed to quantify the residual deformation and final damage morphology. Based on the experiments, an ALE fluid–structure interaction model was established in LS-DYNA and validated against the measured displacement fields, residual deflections, and AFRP tearing characteristics. Parametric analyses were further performed to investigate the effects of the front steel layer (FSL) yield strength and aramid backing layer (ABL) thickness on the blast response. The results showed that the unbacked high-strength steel plate underwent central petalling perforation, whereas the introduction of AFRP backing effectively suppressed perforation and changed the failure mode to non-perforated localized bulging. Increasing the AFRP backing thickness reduced both the residual deformation and damage extent of the composite target. Energy evolution analysis indicated that the structural energy was mainly concentrated in the FSL, while the ABL accounted for only a relatively small proportion of the total energy. Thus, the blast-resistance enhancement provided by the AFRP backing was mainly associated with constraining the localized large deformation and tearing development of the steel plate. For multilayer AFRP-backed configurations, the inner aramid layers adjacent to the steel plate accounted for a larger proportion of the total ABL energy than the outer layers. In addition, increasing the FSL yield strength and ABL thickness improved the blast resistance of the composite plates, whereas the incremental benefit of further increasing the backing thickness gradually diminished. These findings provide a reference for material selection and optimization of high-strength steel/AFRP composite blast-resistant structures.