Paper honeycomb core bonding technology

Abstract : According to the production process of paper honeycomb sandwich material, its production process and the key process control techniques and various process parameters are introduced in detail.
Keywords: Paper Honeycomb Sandwich Adhesives Process Parameters 1 Introduction Composite sandwich materials are widely used in various industries, among which honeycomb sandwich materials are favored by more users because of their unique advantages. In recent years, domestic enterprises have increased the production of honeycomb core materials, especially paper-based honeycomb core materials. The function of the honeycomb structure is to combine the two panels in one piece of media and provide a stable support. Commonly used honeycomb materials include metal aluminum foil, thin plastic sheet, kraft paper (or parchment), and glass fiber cloth. According to the materials used, it can be broadly divided into three types, namely metal honeycombs, paper honeycombs and glass fiber cloth honeycombs. The following only describes the paper honeycomb manufacturing process and related technical parameters.
2 Manufacture of paper honeycomb core material 2.1 Raw material a Paper The commonly used paper material is kraft paper (or parchment paper). The performance indicators are shown in Table 1.
Table 1 Technical performance indicators of kraft paper

b Adhesive Paper Honeycomb core joints have many types of adhesives. Commonly used adhesives are white glue (polyvinyl acetate emulsion adhesive) and acetal drying glue. White glue is low in price, has good adhesion to fibers and porous materials, but its water resistance, acid and alkali resistance are poor; the acetal drying glue liquid has a slightly higher price, has good adhesion to paper, and has Excellent resistance to water, heat, sunlight, and media.
When these two types of adhesives bond the node of the paper honeycomb core, they all have the characteristics of high strength of the node, strong surface adaptability, and good process performance, and can be selected according to actual conditions.
2.2 Manufacturing process The manufacture of paper honeycomb core requires special equipment (not specifically introduced here). Its manufacturing process flow is:
Roll paper rack - online - equipment (oven) warming - plastic injection - adjust the status of the strip - delivery - cutting - hot pressing - curing - trimming and cutting - inspection - the main finished product Process technical requirements:
(1) The device (oven) raises the temperature of the roll paper and the solvent will infiltrate the paper into the paper when the glue is applied. The effect of temperature rise is to actively evaporate the solvent and moisture in the paper inside the film. The temperature is generally controlled at 60-80°C.
(2) Injection glue can generally be used directly. If the viscosity is large, it can be diluted to 50-60s/(coating -4 cups).
(3) There are two types of rubberized coating methods, vertical and horizontal strips. As shown in Figure 1 (slightly omitted).
More commonly used for vertical stripe glue. The coating work of the vertical stripe glue is completed by the rubberizing roller. The rubberizing roller is divided into two roller shafts, A and B, to arrange a set of rollers, and a corresponding storage tank is arranged. When gluing, the roll paper is tensioned and stretched on both sides of the roller and the strip is coated. The strip width should be equivalent to the side length of the honeycomb (with a tolerance of ±0.1 mm). The strip thickness is 10 to 20 μm. The corresponding positions on both sides of the roller are half-spaced (W/2), as shown in Fig. 2 (slightly omitted):
(4) The tape adjusting device is turned on to a low speed of 100 to 200 r.min-1 to observe whether the strip is even and uniform, and the width is suitable, whether there is a lack of glue or over coating. Until the positive and negative sides of the orderly stripes.
(5) After the paper receiving temperature and the state of the rubber strip meet the requirements, the speed of the equipment is increased to 300-400 r·min-1, and the number of paper receiving layers is recorded. According to the drying degree of the strip after passing through the drying tunnel, the running speed can be adjusted at any time. The strips are required to reach a half dry level after they have been dried. After the honeycomb laminated roll reaches a predetermined number of layers, it can be shut down.
There is a relation between the number of delivery layers and the length of the delivery after unfolding:
_
N0=2L/P N=2N0 (1)
_
Where: N0 is the number of delivery layers; N is the number of honeycomb core layers; L is the length of the delivery (unidirectional); P is the circumference of the delivery roller (average).
The relationship between the number of layers of the honeycomb core and the stretched length of the core material is as follows:
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N'=L/(√3 a/2+tH) (2)
Where: N' is the number of honeycomb core layers; L is the honeycomb core tensile length; a is the side length of the honeycomb core grid; tH is the paper thickness.
The following relationship between the number of honeycomb core layers and paper thickness:
N′′=H/tH (3)
In the formula: N′′ is the number of layers of the honeycomb core; H is the thickness when the honeycomb strip is not stretched.
The formulae (1) to (3) above can all calculate the number of honeycomb core layers. The three values ​​of N, N', and N' are approximately the same, and they are considered to be equal if the precision is not high.
(6) Hot press curing The cut pieces of paper are removed to remove scattered parts, and then folded in half, and heated and pressurized in a hot press to solidify. Curing pressure is about 0.6MPa, drying at 120-160 °C, 3-5h, and finally the pressure is reduced to below 80 °C to relieve pressure.
3 Honeycomb core material specifications The length of the honeycomb lattice made of kraft paper is 8mm, and the paper thickness is 0.08mm. The force direction of the honeycomb core is mainly in the direction perpendicular to the panel and the plane direction of the panel. Its technical indicators are shown in Table 2.
Table 2 Paper Honeycomb Core Specifications

4 Conclusion Paper honeycomb core manufactured by the above method has uniform grid, light weight, good flexibility, and low price. After flame retardant treatment and dipping and setting, high fire protection requirements can be achieved, and the compressive strength, shear strength and stiffness can be greatly improved, and can meet higher requirements for use. The composite material produced by using the core material is light in weight, good in strength and rigidity, and has the characteristics of sound insulation, heat insulation, and good shape retention. Is widely used in aviation, aerospace, shipbuilding, vehicles, construction, sports equipment and furniture manufacturing. Therefore, the paper honeycomb core composite has broad prospects for development. (Zhou Minxi Technical Department of Jiangxi Chaoyang Machinery Plant, Pengze County, Jiangxi Province 332727)