CTH shock physics simulation of non-linear material effects within an aerospace CFRP fastener assembly due to direct lightning attachment

Abstract

This study examines detailed CTH simulation results of a carbon fiber composite panel assembly where the binding titanium fastener joint is the attachment point of a direct lightning strike. A refined COMSOL Multiphysics electromagnetics calculation is performed on the undeformed installed fastener geometry to obtain current and electric field solutions in time using SAE ARP5412B lightning test waveforms. Electro-mechanical coupling is achieved through the use of Joule heating resulting from J·E, the power per unit volume dispersed throughout the structure due to the lightning energy transport. The shock physics code CTH is used to model the fluid-structure calculations which involve highly non-linear and high temperature effects. Experimental data, in the form of material effects images, are used for validation of material and equation of state selections. Discussion of the effects created by the lightning energy depositions focuses primarily on gas conditions in the inner spaces surrounding the fastener and the associated local geometrical changes. The spatiotemporal pressure evolution within the fastener assembly cavities are compared with experimental results and the importance of modeling chemistry changes in future work are discussed within the conclusion.