An Experimental Approach to Determine Load-functions for the Impact of Fluid Filled Projectiles

Dr. Ing. Nico Hermann, Institute for Reinforced Concrete Structures

Klaus Kreuser, Prof. Dr Ing. Lothar Stempniewski, University of Karlsruhe (TH)

Abstract:

We report on a series of tests that has been performed at our institute with the goal of evaluating the load-time-history of fluid-filled projectiles on a target that can be regarded as almost rigid. An air-pressure gun has been used that is capable of accelerating a projectile of 2.5 kg to a velocity of about 220 m/s. The air-pressure-level can be adjusted up to 100 bars.

In order to gain first results on the shape and the peak-loads of load-functions for projectiles with stiffness and mass distribution similar to the proportions of a commercial aircraft we performed impact tests with velocities in the range of 130 m/s to 190 m/s and a projectile mass of about 700 g. As material we used an aluminum alloy which is common in the aircraft industry. The fluid-filling was realized by using tanks either half-filled or full with water or in some cases filled with a substitution mass of expanded clay beads.

The whole test set-up will be presented and its capabilities will be described. The measurement technique for the load and the velocity registration will be shown. Some showcase results from first and still ongoing data interpretations will be given as well as a discussion on the difficulties of evaluating the load-time-signal out of the raw data that is always overlaid by vibrations due to the eigenfrequencies of the target and the measurement device itself.

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