Damage is inflicted on carbon fiber/epoxy composite plates using both simulated lightning strikeand mechanical impact in the effort to understand the relative effect of the two damagemechanisms. A methodology is proposed to characterize the damage resistance and tolerance ofunconfigured composite plates subjected to lightning strike in a fashion that is consistent with theextensive work previously done on low velocity impact. Lightning strike damage is inflicted onlyon unpainted, unprotected specimens containing a stainless steel Hi-Lok fastener. In a previousstudy, the authors showed that the presence of the fastener leads to greater damage thanunnotched specimens, and hence would represent the worst-case situation for residual strength.Damage resistance is characterized by means of ultrasonic C-scans and microscopy, whileresidual strength is measured by means of Compression After Impact (CAI) testing. For bothloading mechanisms, it has been shown in the literature as well as by the authors that the mostcritical condition for residual strength is compression loading. Results show that the energydissipated in a specimen during the lightning strike is much greater than the strain energyintroduced by mechanical impact, and hence a comparison based on energy is not recommended.However, based on the relative threat levels associated with both impact and lightning strikedamage, the comparison yields insightful observations on both damage state and residualperformance. In general, for the configurations tested, the lightning strike threat seems to be lessdetrimental than the mechanical impact in terms of both damage area and residual strength.
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