Underwater nearfield blast performance of hydrothermally degraded carbon–epoxy composite structures

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An experimental and computational study was conducted to evaluate the dynamic response of weathered biaxial composite plates subjected to near-field explosive/blast loadings. Naval structures are subjected to aggressive marine environments during their service life that can significantly degrade their performance over time. The composite materials in this study are carbon–epoxy composite plates with [0, 90]s and [45, − 45]s layups. The composites were aged rapidly through submersion in 65 ∘C seawater for 35 and 70 days, which through Arrhenius’ methodology, simulates approximately 10 and 20 years of operating conditions, respectively. Experiments were performed by clamping the composite plates to an air-backed enclosure inside an underwater blast facility. During the experiments, an RP-503 explosive was submerged, behind the composite specimen, and detonated. Meanwhile, transducers measured the pressure emitted by the explosive, and three high-speed cameras captured the event. Two of the cameras were placed facing the specimen to measure full field displacement, velocities, and strains through a 3D digital image correlation analysis. The third high-speed camera was used to record the explosive’s behavior and bubble-to-specimen interaction. Additional experiments were performed to obtain the non-weathered and weathered material properties as well as the residual strength post the blast experiments. Additionally, a coupled Eulerian–Lagrangian finite element simulation was conducted to complement the experimental findings. Results show that the diffusion of water into the composite material leads to a more prominent blast response as well as the degradation of mechanical properties, especially shear properties which are dominated by the epoxy matrix. Residual strength experiments also show a substantial decrease in the structural integrity post-blast loading for the weathered composites. Lastly, the numerical simulations showed substantial increase in maximum strains with relatively small decreases in mechanical stiffness. Hence, even past the saturation point, incremental changes in material properties can have a significant impact on mechanical performance.

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Multiscale and Multidisciplinary Modeling, Experiments and Design