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



Carbon fiber reinforced plastic (CFRP) composites have been applied to the primary aircraft structures to improve fuel efficiency because they have superior specific strength and stiffness. Lightning that occasionally strikes flying aircraft produces structural damage. Once the CFRP structures are damaged, inspection and repair are required. To improve the robustness and damage resistance against lightning strike, it is important to elucidate the damage mechanism of CFRP laminates exposed to lightning strike. In this study, simulated lighting current (impulse current) testing was conducted to elucidate the damage behavior of CFRP laminates. Carbon fiber / toughed epoxy prepreg (IMS60/133; Toho Tenax Co. Ltd., Japan) laminates, which had a quasiisotropic stacking sequence ([45/0/-45/90]4s), were evaluated. Simulated lightning current testing were conducted using an impulse current generator (Otowa Electric Co. Ltd., Japan) in National Composite Center, Nagoya University, Japan. After the impulse current testing, ply lifting caused by the thermal decomposition of matrix resin and carbon fiber breaks were observed on the surface of the specimen. In addition, delamination within approximately 1.5 mm (10 plies) from the surface was detected using ultrasonic scanning. Coupled thermal-electrical analysis, heat transfer analysis, and stress analysis using cohesive elements were carried out using a commercial finite element analysis software (ABAQUS ver.6.14, Simulia; Dassault Systemes, France). A thermal decomposition model, which was estimated experimentally using thermogravimetric analysis results, was incorporated into ABAQUS with user-subroutine. The delamination of CFRP laminates exposed to impulse current was simulated successfully. As a result, it was revealed that the reduction of interlaminer strength (fracture toughness) due to the progress of thermal decomposition accompanying heat

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