Final Report Summary - LIGHTNING (Lightning protection for structures and systems on aircraft utilising lightweight composites)
The LIGHTNING project focussed on areas were lightning protection was difficult to design or certify on general aviation aircraft because of the lack of available test data and guidelines. Its consortium formulated and helped to develop designs for lightning protection which were tested with high currents and voltages.
More specifically, the project targets were to:
1. identify, through testing supported by modelling, lighting protection solutions for lightweight composite structures;
2. determine how effective dielectric materials such as plexiglass and fibreglass could resist lightning swept stroke puncture or initial arc attachments;
3. identify installation methods to protect avionics systems and power bus, demonstrating them by testing of mock up systems.
The programme outputs included test reports which incorporated guidelines on implementing lighting protection. These guidelines were also composed in a standalone report which aimed to assist European aircraft manufacturers in the design of lightning protecting aircraft. Moreover, many of the involved partners developed and manufactured test samples which were not submitted as itemised deliverables.
Firstly, the available lighting protection methodologies and manufacture methods for both glass and carbon composite structures were reviewed, so that those to participate in comparison tests were selected. Samples were then manufactured and initially characterised to compare their mechanical properties. The findings necessitated more rigorous stress-strain characterisations of the panels, so as to determine the correlation of observed non-linearities.
Moreover, lighting testing and measurements of the produced panels were performed. The results showed that the impulse imparted to the panel during lightning tests was not strongly dependent on the lightning protection used, but could be strongly affected by external layers such as thick paint. Larger samples were also analysed to examine the failure mechanisms of full scale items. Surface damage proved to be consistent in all cases.
Additional LIGHTING tasks included modelling of the impulse effects in an attempt to better understand the nature of the lighting shock effect. The panel response eigenmodes were well represented, but the predicted deflections were too high. Static deflections' simulations also produced satisfactory results. It appeared as if the acoustic shock dominated the effects on the panel. However, the more damaging effect for puncture was very local, faster, linked to surface explosion and strengthened by thicker paint layers. Furthermore, lightning effects on insulating surfaces, such as windscreens and fibreglass unprotected structures were analysed and a series of interesting outcomes were obtained.
Two test beds were proposed in order to improve lightning protection for avionic systems and the electrical power bus. Nevertheless, relevant work ran slowly, mainly due to shortage of skilled personnel, and this programme component was not as detailed or instructive as it had been initially hoped. Finally, it was not possible to source thermoplastic panels for comparison or to carry out non-destructive testing on thick monolithic samples. Thus, relevant funding allocations were not used.
More specifically, the project targets were to:
1. identify, through testing supported by modelling, lighting protection solutions for lightweight composite structures;
2. determine how effective dielectric materials such as plexiglass and fibreglass could resist lightning swept stroke puncture or initial arc attachments;
3. identify installation methods to protect avionics systems and power bus, demonstrating them by testing of mock up systems.
The programme outputs included test reports which incorporated guidelines on implementing lighting protection. These guidelines were also composed in a standalone report which aimed to assist European aircraft manufacturers in the design of lightning protecting aircraft. Moreover, many of the involved partners developed and manufactured test samples which were not submitted as itemised deliverables.
Firstly, the available lighting protection methodologies and manufacture methods for both glass and carbon composite structures were reviewed, so that those to participate in comparison tests were selected. Samples were then manufactured and initially characterised to compare their mechanical properties. The findings necessitated more rigorous stress-strain characterisations of the panels, so as to determine the correlation of observed non-linearities.
Moreover, lighting testing and measurements of the produced panels were performed. The results showed that the impulse imparted to the panel during lightning tests was not strongly dependent on the lightning protection used, but could be strongly affected by external layers such as thick paint. Larger samples were also analysed to examine the failure mechanisms of full scale items. Surface damage proved to be consistent in all cases.
Additional LIGHTING tasks included modelling of the impulse effects in an attempt to better understand the nature of the lighting shock effect. The panel response eigenmodes were well represented, but the predicted deflections were too high. Static deflections' simulations also produced satisfactory results. It appeared as if the acoustic shock dominated the effects on the panel. However, the more damaging effect for puncture was very local, faster, linked to surface explosion and strengthened by thicker paint layers. Furthermore, lightning effects on insulating surfaces, such as windscreens and fibreglass unprotected structures were analysed and a series of interesting outcomes were obtained.
Two test beds were proposed in order to improve lightning protection for avionic systems and the electrical power bus. Nevertheless, relevant work ran slowly, mainly due to shortage of skilled personnel, and this programme component was not as detailed or instructive as it had been initially hoped. Finally, it was not possible to source thermoplastic panels for comparison or to carry out non-destructive testing on thick monolithic samples. Thus, relevant funding allocations were not used.
