Composites are used in lots of field such as a part of aeronautic space, ship, machinery and so on because can make structure wished for necessary condition by control fiber direction and laminated sequence.
Aerospace industries are widely using honeycomb sandwich structures that it has high specific strength and stiffness, chemical material resistance and fatigue resistance. Sandwich structure part uses epoxy resin accompanying curing from chemical reaction during processing and resin quality depends on the extent of thermal exposure during curing process. Curing process means coarsely two processes one is the initial curing process to make parts and the other is repair curing process to fix structural damage or defect. And in repairing process of damaged areas, one of the problems is that delamination can be occurred in the sound areas during and/or after the exposure to the elevated curing temperature in case that the repair process is repeated.
Delamination is a typical defect in aircraft and in other application and is characteristic of honeycomb structure. To minimize these delamination occurrence, cure cycle frequency and cure requirement of resin should be controlled, which may improve limitation of usa. Therefore, this study was conducted Flatwise tensile, Drum peel and Long beam flexural strength tests to evaluate the degree of degradation of mechanical properties of the honeycomb sandwich structures affecting thermal aging.
Consequently, the control of curing cycle times and curing condition is recommended for parts in order to reduce the delamination phenomenon between laminate skin and honeycomb core to the minimum in case that the repair process is repeated. As the results, the decrease of mechanical strength was observed at the specific specimen which is exposed over 50hrs at 127℃.