Material testing under high strain rates

Material testing under high strain rates

© Fraunhofer EMI
Comprehensive view of a split Hopkinson compression bar (SHCB).
© Fraunhofer EMI
Tensile sample in a split Hopkinson tension bar (SHTB).
© Fraunhofer EMI
Temperature development of a CFRP sample shortly after failure, measured with an infrared camera.

To examine the material behavior of, e.g., fiber-reinforced composites or metals, Fraunhofer EMI not only operates servo-hydraulic testing machines for the range of medium-dynamic velocities, but also uses test setups for the characterization under higher strain rates. When employing split Hopkinson bars, long rods create a mechanical wave within the specimens. We dispose of experiment setups for testing pressure loadings (split Hopkinson pressure bars SHPB) and for testing tensile loadings (split Hopkinson tension bars SHTB). As an advantage of these procedures, no big masses have to be accelerated. Depending of the specimen geometry, strain rates between 200 s-1und 3000 s-1 can be reached. For pressure loadings, we utilize, among others, a specifically modified SHPB for the testing of low-impedance materials (e.g., rubber, adhesives). The strain measurement is conducted with optical measurement procedures. By means of specific temperature chambers, experiments can also be performed at increased temperatures.