What effect have weathering, fatigue, climate, etc. on long term durability of a composite airframe?
Composites do not suffer from corrosion or fatigue like metals, and therefore a composite airframe has no life limit. However, epoxies slowly deteriorate when exposed to UV rays. Therefore it is essential that a UV blocker is applied during the finishing process. Usually, a primer with UV blocking capability is used. This will avoid long term deterioration. Since composites are poor thermal conductors, a dark painted surface will heat up quickly in direct sunlight. Mechanical properties of the composites and adhesives will start dropping significantly above their HDT (Heat Distortion Temperature). Structures built using the wet lay-up method have the lowest HDT, which can be as low as 50C if not postcured. All structural components in the Mission M212 are premoulded from prepreg materials. Curing is achieved under vacuum at 85C, so the HDT is in the order of 90-100C. Nevertheless, we do not recommend the use of a dark topcoat for any composite airframe.
