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

Abstract

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.

Adaptive structures for noise and vibration guidance, monitoring, and control

“…Another topic of research addressed in the Adaptive Structures Laboratory is the structural monitoring via strain gauges, piezoceramic sensors, and fiber optics. In the framework of Clean Sky 2 (CS2) DEFENDER project [2]- [3], aiming at investigating the impact behaviour of crashworthy fuel tanks for the next-generation civil tiltrotor aircraft, the team was involved in the experimental assessment of impact responses experienced during drop tests in order to validate highfidelity models prior to the experiments.…”

“…The second topic of research is the structural monitoring via strain gauges, piezoceramic sensors, and fiber optics. In the framework of Clean Sky 2 (CS2) DEFENDER project [2]- [3], aiming at investigating the impact behavior of crashworthy bladder fuel tanks for the nextgeneration civil tiltrotor aircraft, the team was involved in the experimental assessment of impact responses experienced during drop tests in order to validate high-fidelity numerical models prior to the experiments. Finally, the paper focuses on ice protection systems by means of guided elastic waves generated by piezoelectric transducers (patches), bonded on the interior face of skin elements of the wing exposed to the ice accretion.…”