Dynamic micro-testing over a large range of strain rates for homogenous and heterogeneous local material characterization

The dynamic material characterization shows different macroscopic strain rate effects. The causal mechanisms cannot be identified at this level in most cases. Micro-tests allow a local transient analysis, which is illustrated in this article using the example of a long-fibre reinforced thermoplastic (LFRT). After a general introduction, the development and validation of a micro-test for a large strain rate range is presented. The validation explained for steel shows the advantage of the small sample for the dynamic characterization, if a homogenous material behaviour of this magnitude still exists, especially in the case of low-vibration force measurement. For a heterogeneous LFRT material, the micro-test shows strongly scattering test results that are no longer representative of the homogenized mechanical material behaviour, but reflect the local characteristics. These local properties are directly caused by the injection moulding process. Further SEM analyses of the samples indicate different macromolecular deformation mechanisms of the matrix at the different strain rates.