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Characterisation of outgassing from carbon fibre composite aircraft joints subjected to lightning current

Evans, Simon 2018. Characterisation of outgassing from carbon fibre composite aircraft joints subjected to lightning current. PhD Thesis, Cardiff University.
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Abstract

Outgassing is a lightning direct effect that may occur at structural joints in the fuel laden volume of an aircraft. If uncontrolled, the event is extremely hazardous due to its potential to cause fuel vapour ignition. The aerospace industry has been aware of the threat for many years and lightning strike protection is well established. However, there is a lack of understanding particularly concerning the fundamental mechanisms for the creation of the event. Modern aircraft designs that utilise materials such as carbon fibre reinforced plastic (CFRP), are more dependent on manufacturing process control. Knowledge of the fundamental mechanisms responsible for outgassing can enable relaxation of specifications concerning manufacturing variables that exist, specifically, for the lightning protection of CFRP structures. Evidence from previous studies has revealed the significance of parameters relating to the interface between the fastener and the surrounding structure. However, the electrical parameter that drives the creation of the phenomenon remains unclear. The principle aim of this thesis was to determine a single measurable electrical parameter related to outgassing intensity in CFRP structures which can be used as a performance metric for the optimisation of lightning strike protection. Following the execution of three controlled experiments, it was found that outgassing intensity is a direct consequence of the magnitude of electrical energy absorbed, specifically, at the interface between the fastener shank and the surrounding CFRP structure. Characterisation techniques for robust voltage measurement and the distribution of current to the critical interface were developed to deduce the magnitude of energy absorption. This critical parameter can be now used as a control parameter in future aircraft development for the optimisation of lightning strike protection.

Item Type: Thesis (PhD)
Status: Unpublished
Schools: Engineering
Uncontrolled Keywords: Lightening, outgassing, aircraft, sparks, composite, CFRP
Date of First Compliant Deposit: 2 January 2019
Last Modified: 02 Jan 2019 10:58
URI: http://orca.cf.ac.uk/id/eprint/117887

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