When designing, the main factors considered for the panel ...
When designing, the main factors considered for the panel are the strength and stiffness of the material, while for the core material foam, the main factor considered is the magnitude of the weight reduction. Aluminum honeycomb, foam or NOMEX® honeycomb are often used as core materials in aircraft structures. Aluminum honeycombs or NOMEX® honeycombs have the advantages of high compressive modulus and light weight, they are widely used sandwich materials for aircraft structures, usually with carbon/glass fiber prepreg.
Common structures include wing leading edge, rudder, landing gear hatch, wing body and wingtip fairing, etc. Although the honeycomb sandwich structure has outstanding advantages over the sheet metal structure in terms of performance, airlines are still actively looking for alternative materials, because the honeycomb sandwich material requires high maintenance and repair costs during use.
In some cases water and moisture can easily enter the honeycomb if there are cracks and pores in the panel. Under low temperature conditions, the water entering the honeycomb cells will expand after being frozen, which will destroy the bonding of adjacent honeycomb cells, which reduces the performance of the sandwich structure and must be repaired. The maintenance cost of the honeycomb sandwich components makes the original advantages of lightness no longer exist compared with the foam sandwich structure.
Since the rigid foam sandwich is closed-cell, water and water vapor cannot enter the interior of the sandwich, which reduces the cost of maintenance and inspection, so the life-time cost of the foam sandwich structure is more economical, although the weight of the foam is lower when the same shear capacity is achieved. Slightly heavier than honeycomb. With a series of problems in the use of composite honeycomb sandwich structures, researchers in the aerospace industry at home and abroad have turned their attention to high-performance polymer foam core materials, mainly PMI foam materials.
In sandwich structural members, foam cores are used both to reduce manufacturing costs and as a structural material. If it is only considered as a structural material, the core material foam structure is mainly at a disadvantage in terms of weight compared with the design of the honeycomb core sandwich structure.