Non-destructive testing of protective components after contact detonation

Abstract

At the University of German Armed Forces steel fiber concrete for use in protective structures has been investigated as a central part of a research project. A steel fiber concrete with a low strength (C25/30) was produced in style of a concrete made of local material which is available in the mission region has been investigated under contact detonation loadings. Plates with varying fiber geometries, different thicknesses and reinforcement systems were produced in the laboratory of the Institute of Structural Engineering at the site of the University of German Armed Forces in Munich. The plates were loaded with 850 g PETN explosive at the test facility of the German Armed Forces Technical Center for Protective and Special Technologies. The contact detonation generates a pressure wave which runs through the plate and which is reflected as a tensile wave at the unloaded surface opposite to the loaded surface. On the unloaded surface of the plate the tensile wave generates a damage crater due to the weak tensile strength of concrete. The aim of this part of the investigation was to measure the damage crater with a non-destructive testing method. For this matter the impact-echo method was used. The results of the measurements were verified by cutting the plates in the middle of the crater and by taking drill cores in the damage zone. With these measurements the volume, the surface and the geometry of the damage crater have been determined in order to get input parameters to develop a semi empirical formula for the determination of the crater volume and its surface.