DEFLECTION-TIME CHARACTERIZATION ON HIGH- PRESSURE IMPACTED THERMOPLASTIC-METAL HYBRID PANELS

Abstract

High strain rate events pose high levels of complexity when analyzing a materials deformation characteristics. In high strain rate events like blast and impact, understanding the damage progression within the tested material is crucial when optimizing material design to give a desired performance. Under extreme loading cases inertial effects play a large role on how a material system performs. When a structure is blast loaded and begins deformation, inertial effects cause the structure to continue to deform past its stressed equilibrium point even after the main front of the shock wave has passed until it stabilizes its inertial effects with the material’s strength. At the point of momentary rest, the inertial effects are zero, and the structure begins to rebound causing the structure to elastically “snap back”. This behavior may repeat and oscillate to release the energy that was transferred into it until remaining at rest at its plastically deformed state. In this work, high-pressure impact loading was implemented on a thermoplastic-metal hybrid panel via free piston shock tube. Finite element models, and pressure-time and deflection-time histories, were used to correlate the deformation characteristics to an applied blast loading. Deformation characteristics are obtained in real time during the blast test using fringe projection methods. To correlate and better describe experimental observations, finite element models were developed in LS Dyna for the blast apparatus and hybrid composite panel, and the results are compared to the experimental blast tests. The results show a lag in the deformation response within the material structure from peak loading to peak deflection of 0.5ms in both the model and fringe projection analysis. Furthermore, the deflection-time history between the model and fringe projection data show similar correlations behaviorally for the duration of valid testing.