Numerical and Experimental Studies of Free-Fall Drop Impact Tests Using Strain Gauge, Piezoceramic, and Fiber Optic Sensors

The present work is framed inside a broader activity aimed at improving the accuracy
of numerical models in predicting the crashworthiness behavior of flexible fuel tanks. This paper
describes a comprehensive experimental and numerical study aimed at estimating the impact force
of a test article, consisting of a soft nylon bag filled with water, subjected to crash impact tests. In
order to understand and improve response predictions, the test article drops freely from different
heights, and then strikes onto a rigid plate which is instrumented with different types of sensors.
Strain gauges, piezoceramic sensors, and fiber optics are used to measure the strain induced by the
impact force during the experiments. To tune the test matrix and the measurement chain parameters,
numerical computations are carried out to predict the dynamics of drop impact through FE explicit
analyses. Through analysis and comparison with experimental results, a relationship between strain
and impact energy correlated with the drop height is established, and the overall accuracy of the
entire measurement chain is assessed to determine the effectiveness of such a methodology in a
full-scale test on a flexible fuel tank structure.