Delamination Analysis of CFRP Laminates Exposed to Simulated Lightning Current Considering Pyrolysis Reaction

摘要

Carbon fiber reinforced plastic (CFRP) composites have been applied to theprimary aircraft structures to improve fuel efficiency because they have superiorspecific strength and stiffness. Lightning that occasionally strikes flying aircraftproduces structural damage. Once the CFRP structures are damaged, inspection andrepair are required. To improve the robustness and damage resistance against lightningstrike, it is important to elucidate the damage mechanism of CFRP laminates exposedto lightning strike.In this study, simulated lighting current (impulse current) testing was conducted toelucidate the damage behavior of CFRP laminates. Carbon fiber / toughed epoxyprepreg (IMS60/133; Toho Tenax Co. Ltd., Japan) laminates, which had a quasiisotropicstacking sequence ([45/0/-45/90]4s), were evaluated. Simulated lightningcurrent testing were conducted using an impulse current generator (Otowa Electric Co.Ltd., Japan) in National Composite Center, Nagoya University, Japan. After theimpulse current testing, ply lifting caused by the thermal decomposition of matrixresin and carbon fiber breaks were observed on the surface of the specimen. Inaddition, delamination within approximately 1.5 mm (10 plies) from the surface wasdetected using ultrasonic scanning.Coupled thermal-electrical analysis, heat transfer analysis, and stress analysisusing cohesive elements were carried out using a commercial finite element analysissoftware (ABAQUS ver.6.14, Simulia; Dassault Systemes, France). A thermaldecomposition model, which was estimated experimentally using thermogravimetricanalysis results, was incorporated into ABAQUS with user-subroutine. Thedelamination of CFRP laminates exposed to impulse current was simulatedsuccessfully. As a result, it was revealed that the reduction of interlaminer strength(fracture toughness) due to the progress of thermal decomposition accompanying heat generation is dominate for lightning strike damage, however other phenomenaincluding mechanical load also affect the damage mechanism.