Effects of Lightning and Nuclear Electromagnetic Pulse on an Advanced Composites Aircraft

Abstract

Design of future high performance aircraft systems will show more emphasis being placed on advanced composite materials and sophisticated avionics in order to meet the mission requirements. The low electrical conductivity of advanced composites relative to metals presents the design engineer with potential problems when utilizing composites in the construction of primary aircraft components. This conductivity is a key parameter in determining the vulnerability of an aircraft to lightning and nuclear electromagnetic pulse. The intent of this paper is to investigate the behavior of graphite/epoxy structures when exposed to both of these threats and to present suggestions to improve their performance.

The investigation begins with the design and fabrication of 1/12 scale model of the Advanced Design Composite Aircraft (ADCA) which is employed as the baseline vehicle. The model, built in part of graphite/epoxy, is used for lightning strike tests to determine the attachment points, **their distribution and frequency of occurrence on the aircraft. These tests assess the differences between composite and metal aircraft. Then, the indirect effects of the direct lightning strikes on the composite structure are determined.

The study continues with the analysis of a mathematical model of the ADCA to estimate the external and internal coupling for nuclear and lightning electromagnetic pulses. The numerical results for induced surface currents and charges (external coupling), and for skin-diffusion-induced currents and voltages on typical cable runs inside the aircraft (internal coupling) are presented. Finally, basic electrical conductivity and shielding effectiveness data of graphite/epoxy generated in this study is also presented.

This paper presents the results of task work performed by Grumman Aerospace Corporation, under contract F336l5-TT-C-5l69, sponsored by the U.S.A.F. Flight Dynamics Laboratory.