A Comparison of the Prediction of Lightning Indirect Effects Using 2-D Analytical Tools with Measured Data from Two Composite Test Fixtures 2001-01-2904

A comparison was done of the prediction capabilities for lightning indirect effects of two two-dimensional (2-D) computer codes using two graphite structural test fixtures. The two codes evaluated were an internal Boeing Method-of-Moments code and a commercially available Boundary Element method code. The codes were compared against each other and against test data. The purpose was to evaluate the prediction capabilities of both codes for use in predicting lightning indirect effects on internal components of graphite structure. Since 2-D codes are much easier to use than 3-D codes, they could be widely used in trade studies and design evaluations for lightning indirect effects protection of composite aircraft.

The first code, REDIST, is a Method-of-Moments code developed in the 1980’s for use on the B-2. The REDIST code has short run times and is somewhat easier to use than the second code that was investigated. The second code examined, Oersted, is a Boundary Element method code and is commercially available. It has a modern GUI interface and post processing capabilities but is more difficult to implement and has longer run times. These two codes were compared with each other and with test data for a variety of geometries that simulated two graphite test fixtures with internal metal components.

The test data taken was on two structural graphite composite test fixtures. The first was a graphite skin panel segment with 3 blade stiffeners. Low Level Continuous Wave (LLCW) measurements were made of the current on an aluminum tube placed in several locations near the skin and blades to understand the lightning current redistribution in areas such as wing leading edges. The second test fixture was an outboard section of a graphite composite wing box built by Boeing and NASA. Several aluminum tubes were installed to simulate hydraulic and fuel lines or electrical conduits and shields. Again CW measurements of the tube currents were made. These test results are compared with the two code results for various tube locations and modifications to the wingbox.