Developing Test Methods for Compression after Lightning Strikes

Abstract

Research into residual strength after lightning strike is increasing within the literature. However, standard test methods for measuring residual compressive strength after lightning strikes do not exist. For the first time, a systematic experimental study is undertaken to evaluate modifications necessary to standard Compression After Impact (CAI) specimen geometry and test jig design to induce specimen failure at the lightning damage region. Four laboratory generated lightning strike currents with peak amplitudes ranging from 25 to 100 kA have been studied. Test set-up modifications were made considering the scale of the lightning damage and its potential proximity to specimen edges. Specimen geometry and anti-buckling guides were adjusted for each peak current to induce specimen failure at the lightning damage. The Compression After Lightning (CAL) strength was 28% lower than the pristine CAI strength even at a relatively low peak current of 25 kA. This study shows that the standard CAI test setup has the potential for CAL application, however, careful modifications are required depending on the peak amplitude of the applied lightning current waveform.