Effect of Hydraulic Oil Aging at Different Temperatures on the Mechanical Behavior of Nomex and Aluminum Honeycomb Sandwich Composites

The mechanical behavior of carbon fiber–faced sandwich composites with Nomex and aluminum honeycomb cores was investigated after exposure to hydraulic oil at different temperatures. The sandwich composites were fabricated using a hand lay-up process followed by hot pressing. The specimens were immersed in ISO VG 37 hydraulic oil at 50, 70, and 90 °C for 8 h prior to mechanical testing. The specimens were subsequently subjected to three-point bending and edgewise compression tests. Although the Nomex core specimens exhibited a certain strength reduction at 50 °C, their performance was not significantly affected at higher temperatures of 70 °C and 90 °C. On the other hand, aluminum core carbon fiber sandwich composites were influenced by aging at all temperatures, with more severe degradation observed at 70 °C and 90 °C, where delamination occurred between the aluminum core and the carbon fiber face sheets. In conclusion, Nomex/carbon sandwich composites demonstrated higher resistance to short-term hydraulic oil and temperature exposure, whereas Al/carbon sandwich composites lost their structural integrity more rapidly at elevated temperatures.