Analysis of Impact Damage by Lightning Strikes on Aircraft CFC Structures

Abstract

The direct effects of lightning take the form of burning, heating, magnetic force, sparking and arcing. The direct effects result in local physical damage to the aircraft surface and structures which must be designed to be safe against these effects. The intensity of the electrical charge profiles depend on whether the structure is in initial direct strike zone attachment, a swept zone of repeated attachment or in an area through which the current is being conducted. In the case of direct attachment on carbon fiber composite (CFC) parts, one of the most classical methods of protection is the incorporation of metal or metallic mesh on the outer skin of the laminate. In order to evaluate the development of the laboratory built to investigate direct effects of lightning damages in CFC structures, some test specimens were designed and manufactured based on typical assemblies found in the aircraft composite parts. The specimens basically consisted of composite panels protected with different lightning surface protection fastened together. The specimens were subjected to tests with the application of 100kA or 200kA oscillatory discharges according to the parameters defined for the lightning Components D and A in the SAE ARP5412 [1] and RTCA DO160 [3] which are the key standards for descriptive characteristics of lightning strikes to aircraft. Although the protective materials are able to assure that the overall mechanical characteristics of the specimen are maintained, damages to the protecting materials are always present. For this reason and for precise assessment of the protection each test specimen was only subjected to the lightning pulse once. This article presents the development of the laboratory and the results of work done in it in performing the tests with such lightning waveform component in CFC panels, as described.