Stress wave propagation and force transmission in polymeric closed cell foams subjected to air shock loading

Polymeric foams are widely used in sandwich structures to withstand blast loadings, serving as energy dissipators and force attenuators. This study explores the mechanics involved when an air shock interacts with closed-cell polymeric foam. The authors provide a comprehensive analysis of stress wave propagation and its evolution across the foam specimen by employing ultra-high-speed imaging and digital image correlation (DIC). Measurement of elastic, plastic, and shock wave velocities inside the impacted foam was conducted. A methodology to predict elastic precursor wave velocity is proposed, that considers the foam material's behavior at higher strain rates. The predicted values were found to be in excellent agreement with the experimentally obtained values. Furthermore, the authors investigate the force transmission through foams as a function of bulk foam density under unconfined conditions. The results reveal that under shock loading intensities where foam specimens remained in their elastic regime, a transmitted force amplification was observed relative to the input load. However, when subjected to higher-intensity shock loading, substantial foam deformation occurs during the initial propagation of the shock wave. In these cases, the transmitted force measured was found to rely on the plastic and shock waves generated within the material. Additionally, as the loading persists, the force transmissibility ratio decreases beyond the initial stress wave propagation phase, thus demonstrating the material's suitability for blast mitigation applications. & COPY; 2023 Elsevier Ltd. All rights reserved.

Automated summary

This study investigates the mechanics of air shock interacting with closed-cell polymeric foam. The authors use ultra-high-speed imaging and digital image correlation to analyze stress wave propagation. The results show that polymeric foam has good force transmission capability under shock loading, making it suitable for blast mitigation applications.