Resin fillet formation in honeycomb sandwich structures

© 2015 International Committee on Composite Materials. All rights reserved. In order to meet the challenges of high production rates for composite structures, an understanding of the relationship between the skin-core interface and heating rate during the curing of sandwich structures is required. This study found that heating rate during cure can affect the size and shape of resin fillets between the skin and the honeycomb core cell walls, but not in a practically significant way. A small effect of heating rate on resin fillet size was seen when heating Hexcel HexPly 8552 UD skinned, Kevlar paper honeycomb cored sandwich structures at 1.5, 6 and 8°C/min. The resin fillet sizes were larger when heated at 1.5 and 6°C/min than those heated at 8°C/min, although there was a large variability of resin fillet sizes. This study concluded that while the effect of heating rate on the skin-core bond needs to be considered, faster heating of composite sandwich structures with epoxy resins and isothermal curing required for automotive production will not greatly affect the skin-core bond.