The honeycomb core material is referred to as the honeycomb core. The honeycomb core material sandwiched between the two panels of the honeycomb sandwich structure. In the sandwich structure, it mainly bears the shear stress, so that the sandwich structure has high bending stiffness. There are two classification methods: according to the honeycomb material, it is divided into aramid paper honeycomb (Nomex honeycomb), glass cloth honeycomb, aluminum honeycomb, graphite honeycomb, ordinary paper honeycomb, kraft paper honeycomb, stainless steel honeycomb, plastic honeycomb, cotton honeycomb, etc., commonly used are Nomex, glass cloth, and aluminum honeycomb; according to the shape of the honeycomb cell, it can be divided into hexagonal, rectangular, square, bell-shaped, sinusoidal, and diamond-shaped. Double bell-shaped, tubular honeycomb, etc., the longest used is hexagonal honeycomb. The honeycomb core is a lightweight material, and its density varies with material type, thickness, cell size, and impregnated resin content. For example, the density of Nomex honeycomb is 24-144kg/m3, that of glass cloth honeycomb is 32-192kg/m3, and that of aluminum honeycomb is 16. ~192kg/m3. The mechanical properties of the honeycomb of the same material increase with the increase of density; within the same density range, the smaller the cells, the thicker the cell walls, the higher the mechanical properties. The compressive strength of Nomex, glass cloth and aluminum honeycomb at the same density is basically the same, but the shear strength of glass cloth and aluminum honeycomb is higher than that of Nomex honeycomb. Among honeycombs with the same density, graphite honeycomb has the highest strength and modulus. The honeycomb core is an anisotropic material, and the shear strength and bending strength of the L direction (perpendicular to the cell expansion direction W direction) are much greater than the W direction. Aluminum honeycomb has good mechanical properties and durability, can conduct heat, and has a simple manufacturing process, but its fatigue resistance and impact resistance are poor. Electrochemical corrosion occurs in contact with composite material panels; glass cloth honeycomb has good strength and rigidity, excellent dielectric properties and corrosion resistance, but is brittle, poor in toughness, and low in processing accuracy; Nomex honeycomb has light bulk density, high specific strength and rigidity, Excellent impact resistance, fatigue resistance, corrosion resistance, high temperature resistance (long-term work at 160°C), high processing precision, but complex manufacturing process, low shear modulus, and high cost; paper honeycomb is easy to manufacture and low in price. But the mechanical properties and water resistance are poor. Various types of honeycombs are widely used in different fields according to their performance and price, such as aviation, shipbuilding, construction, telecommunications, automobiles, trains, sports equipment, etc.