Investigation into honeycomb durability through an in-flight service evaluation

Abstract

Thirteen commercial wing panels were fabricated and flown on a commercial aircraft to investigate the mechanisms of water migration through various honeycomb cores. A 12.2 J impact damage was not observed to cause damage propagation in aluminum and Korex® honeycomb materials. This was attributed to the ability of the cores to localize the impact damage. In Nomex® and fiberglass cores, a different damage propagation mechanism was observed. In these cores, the damage was not confined to the localized area around the impact. Instead, core damage was seen as far as 2.0 cm from the point of impact. This increased core damage allowed the core to retain water. The retained water helped propagate the impact damage through a freeze-thaw mechanism. Speed-tape repairs were only found to be statistically significant when water migrated through the core. Ultimately, this work provided the tools a methodology for understanding and developing damage and water tolerant honeycomb structures.