Investigating the effects of fluid intrusion on Nomex® honeycomb sandwich structures with carbon fiber facesheets

Honeycomb sandwich construction is commonly used in aircraft structures to make parts with a superior strength to weight ratio. Nomex® honeycomb core is used extensively for flooring, skin panels, fairings, engine cowlings, and flight controls. Honeycomb sandwich structures are prone to fluid ingression due to their thin facesheets which get damaged easily by impact or erosion. The purpose of this research was to determine how the mechanical properties of honeycomb sandwich structures were affected if the structure was saturated by a fluid such as water, fuel, hydraulic fluid, or engine oil. The authors focused on the lasting effect on the sandwich structure when aircraft fluids ingress into the structure. The test panels were made of carbon fiber prepreg, and they were bonded to a 12.7 mm thick Nomex® honeycomb core material. The specimens were soaked in water, fuel, hydraulic fluid, or engine oil for 45 days. After the soak period, the specimens were removed from the fluids and left to drain for 30 days. The specimens including the control group were tested with a four-point loading test and impact test in accordance with ASTM standards.