Stiffened structures honeycomb core

As shown in O Fig. 42.9a, and not the apparently more economical but weaker joint shown in O Fig. 42.9b. Some years ago, the author tried to stiffen an aluminum alloy honeycomb core by filling with a polyurethane foam. This was then scraped down to the level of the honeycomb and the bond made. Unfortunately, the foam prevented the formation of the fillet and the joint failed at a low load. With bonded honeycomb structure, the major defects consist of a lack of attachment between the core and the skin. This may be due to several causes such as locally crushed honeycomb O Fig. 42.10a), skin defects O Fig. 42.10b), or lack of adhesive (O Fig. 42.10c). In themselves, none of these defects may reduce the short-term joint strength. However, as for the lap joint, they may show poor preparation and may provide sites for fatigue crack propagation. 

Door panels have a sandwich structure consisting of aluminum or stainless steel surface plates and aluminum or paper honeycomb core bonded with two-part epoxy adhesives. On inspection lids, switchboard covers, and seat side panels, decorated aluminum sheets with melamine resin are bonded with second generation acrylic adhesives (SGAs) to aluminum frames or stiffeners. O Figure 47.9 shows the cross section of a railcar with adhesively bonded parts (Suzuki 2007). 

The main structural component of the SR.N4 (British Hovercraft Corporation) according to Powis (1973) is a large sandwich panel 40 m long, 23 m wide and about 1 m thick. The top and bottom skins of this sandwich panel are made of 2 5 mx 1 25 mx 37 mm sandwich panels which are bolted to an egg-box structure made from aluminium shear web with bonded stiffeners. The skin panels are of 6 4 mm and 3 2 mm cell aluminium honeycomb made from foil 0-05-0-076 mm thick. The higher density core is used in the more highly stressed areas. The superstructure of the craft is composed of two vertical beams running fore and aft, which are fabricated from this aluminium sheet with bonded stiffeners. The roof is one unsupported span between... 

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