Fatigue properties of multifunctional metal- and carbon-fibre-reinforced polymers and intrinsic capabilities for damage monitoring

Carbon-fibre-reinforced polymers (CFRP) structures offer enhanced lightweight potential in comparison with monolithic metallic concepts. Brittle failure behaviour and the insufficient level of electrical conductivity limit the lightweight potential of composites. One promising new approach to solve these issues is the additional integration of metal fibres. Structural components are subjected to cyclic loads during their lifetime. Therefore, the present study focuses on the influence of additional steel fibre reinforcement on the fatigue behaviour of CFRP laminates. Magnetic properties are determined because of the deformation-induced phase transformation of the chosen austenitic steel fibres, which are also applied as intrinsic damage sensors. Interrupted fatigue tests are carried out accompanied by scanning electron microscopy to obtain differences in failure mechanisms. Beside a detailed overview of the steel fibre influence on the fatigue properties of conventional CFRP structures, the functional evidence of a new method for nondestructive testing by a magnet inductive measuring device is shown.