Damage prediction of CFRP materials subjected to lightning strike

Abstract

This paper presents a coupled thermal-electric model to predict the thermal damage of a Carbon Fiber Reinforced Polymer (CFRP) material when subjected to a lightning strike. A Finite Element Model (FEM) is used to predict the heat response of the CFRP material by solving the Joule heating governing equations. Joule heating, also known as resistive heating, is the heating of the material when subjected to an electrical current. Solutions to the Joule heating model are developed using a time dependent simulation with the 10/350μs standard waveform used to test wind turbine blades in accordance to IEC61400 section 24 Ed 1.0. The time dependent model implements damage criteria and is able to identify damaged elements. The damage criteria are based on a combination of material decomposition by pyrolysis described by the Arrhenius equation. The COMSOL software engine was used to derive the results from the Joule heating model. An integrated MATLAB script was run during the simulation to determine the amount of damage that each element is subjected to during a lightning strike event. The final result is a damage map of the CFRP panel subjected to a lightning discharge. The damage model is validated through lightning discharge experiments. Two samples with unidirectional fibers were made by vacuum assisted liquid resin infusion to mimic the sparcaps of a wind turbine blade located near the wind blade tip region. The samples were tested using the arc entry test of IEC 61400-24 Ed 1.0 with simulated first return stroke electric current components (10/350μs) with magnitudes of 30 kA and 60 kA unipolar waveforms. The resulting damages were inspected by use of X-ray Computed Tomography (CT) to determine the total damaged volume. The CT scans used an imaging segmentation algorithm to systematically determine the location and type of the damage done to the CFRP. The resulting CT scans are compared to the damage model.

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Identifiers

ORCID for Timothy, Michael Harrell: orcid.org/0000-0002-0783-533X

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