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Thermal Response to Simulated Lightning Currents on Stitched Composite Aircraft Structures

JUHYEONG LEE, THOMAS LACY, CHARLES PITTMAN, JR. and MICHAEL MAZZOLA

Abstract


Integrally stitched composite structures have attracted significant interest for enhancing the structural integrity of aircraft. One recently developed stitched composite technology is the Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) concept. While PRSEUS structures offer a high structural performanceto- weight ratio over traditional stiffened panels and sandwich panels, their thermal response is not well understood. The through-thickness stitching of PRSEUS panels provides a barrier to delamination initiation and growth. Therefore, the thermal and mechanical damage in the PRSEUS panel may be profoundly different than for traditional (unstitched) laminated structures. In this study, nonlinear transient coupled thermal-electrical finite element (FE) analyses and subsequent heat transfer analyses were performed to characterize the thermal response of a PRSEUS panel subjected to a simulated transient high electrical current waveform consistent with lightning strikes. Temperature dependent-material properties of each structural sub-component (i.e., foam core, rod, stringer, frames, and exterior skin) were employed to predict the electrical current and temperature distributions in the PRSEUS panel. Several special-purpose user subroutines were developed i) to simulate the standard lightning current waveform, ii) to predict the temperature distribution associated with high electrical currents, and iii) to update material properties based on temperature-time history. The objective of this study is to characterize the potential thermal damage in a PRSEUS panel exposed to simulated high current waveforms as well as to probe the effect of stitching on the through-the-thickness electrical and heat conduction.

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