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.

Challenges and Future Recommendations for Lightning Strike Damage Assessments of Composites: Laboratory Testing and Predictive Modeling

“…On the other hand, the destructive method includes fractography using scanning electron microscopy (SEM), optical microscopy, destructive sectioning, and residual strength tests using three-point or four-point flexural tests or compression-after-impact (CAI) tests. One recent study systematically pointed out the modifications necessary to standard CAI specimen geometry and test setup design to inflict specimen failure at the lightning damage site [93]. The ultrasonic inspection technique provides a projected area and position of the delamination in the CFRP composites.…”

On the Importance of Fibre Direction Mesh Alignment for Artificial Lightning Strike Simulations

“…A sizeable amount of experimental research has been conducted on lightning strike damage in a laboratory environment and has typically focussed on the high peak current Waveforms A or D [13][14][15][16][17][18][19][20]. Authors have studied the influence of novel protection systems [13,[15][16][17][18], paint layers [20], specimen fasteners [21,22] or sequential strikes using multiple waveforms [23][24][25].…”

The Influence of Carbon Fiber Composite Specimen Design Parameters on Artificial Lightning Strike Current Dissipation and Material Thermal Damage

“…An increasing amount of experimental and simulation research has been conducted on the impact of lightning strikes on composite materials [1][2][3][4][5][6][7][8][9][10][11]. The majority of experimental works have studied simple rectangular or square plate material specimens to understand the damage resulting from a specific artificial lightning strike waveform and the potential for a Lightning Strike Protection (LSP) layer to reduce or eliminate damage [9,[12][13][14][15].…”