[of the aircraft] would require different adhesives.” Vargo says his company “hopes to build a facility that produces repair kits.” Looking at the various combinations of tested materials in its research, Cessna will evaluate whether a repair kit can be produced for maintenance in the field, according to Johnson. “We’re looking at both [the skins’] manufacturing ability and at repair ability,” she states. To remove and change the FluoroGrip appliqué, maintenance technicians, working in room temperature, would simply peel the skin off in large pieces, according to Vargo. “The appliqué with adhesive—the whole thing—comes off,” he says. “And the used film is then readily recycled with minimal effect on the environment.” A maintenance benefit is FluoroGrip’s capability of assimilating molecules of pigment that, upon impact, would be released, showing possible structural damage to a composite aircraft. “Currently, composites often won’t reveal impact from the outside,” says Cessna’s Johnson. “Our goal is to make it so you can see any damage that needs to be repaired.” She adds, however, that researchers may determine that pigments are not needed to show damage. Rather they may find that the skins show a scar or dent, like aluminum on older design aircraft.
Health-monitoring sensors embedded in the skin can further damage detection. However, with the capabilities of health- monitoring technology fairly established, Cessna will confine its research to sensor conformity to the STAR-C2 skins. “We’re not looking at the kind of sensors to use, but rather into the smoothing task,” says Johnson. “We’re going to use rivets and wires and cover them with skin materials to see if you can hide those items and keep the aircraft’s surface smooth.”
Test Schedule When AM talked to Cessna late last year, its engineers were engaged in “task three” of an eight-task research program. “We’ve selected the material for the [substrate] panels that will be coated and materials for the skins,” Johnson reports. Initially, Cessna research schedule calls for testing coated substrate panels for impact, direct and indirect effects of lightning, and aesthetics and smoothing. For impact tests, items of varying sizes will be dropped from different heights on the panels, says Johnson. The panels then will be subject to visual inspection and non-destructive testing.
An outside lab will evaluate the direct effects of lightning strikes on STAR-C2
skins, while Cessna determines the indirect effects (the current induced in wire bundles under the panels) at its own facility. An outside lab also will conduct acoustics tests. For smoothness evaluation, Cessna engineers will determine how well the film appliqué will mask rivet heads, splices and wire bundles on panels. “We will take what we learn from the first batch of panels and develop a much smaller second set of hopefully better panels. Each of those will be put through all the same tests,” says Johnson. Might Cessna apply STAR-C2 skins on
its future aircraft designs? “The [NASA] project is to determine if this concept is feasible and to motivate material suppliers to develop more effective materials,” says Johnson. “If we can show that using protective-skin technology is feasible, we would be able to consider applying it in 2025-2030.” Would NASA’s SFW Project sponsor a
third phase of research on aircraft-coating materials? “There are no specific plans for a phase three at this time,” says Siochi. “That being said, our mission is to focus on far-term technologies, and there will be future solicitations for research that will involve competitive bidding.” AM
Aviation Maintenance |
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