A deep hole machining method for composite honeycomb sandwich panels

Abstract

The application discloses a kind of composite honeycomb sandwich panel deep hole processing methods, comprising the following steps: step S10: when manufacturing sandwich panel, the honeycomb core to be processed hole area is pre-filled with potting adhesive and solidified;Step S20: from the surface of one side panel of sandwich panel, with parallel to the thickness direction of sandwich panel, to honeycomb core milling groove, one end of groove is penetrated with the circumferential side of sandwich panel;Step S30: precast pipe is placed in groove, and the hole in precast pipe is consistent with the hole to be processed;Step S40: fill potting adhesive in groove, to flush with the surface of panel, precast pipe is fixed;Step S50: dry glass cloth is laid on the surface of panel to cover groove area, and dry glass cloth is bonded by brushing resin adhesive;Step S60: after resin adhesive solidification, the edge of dry glass cloth is polished smooth.Deep hole processing is not limited by processing tool and processing equipment, avoid the tolerance generated by drill length swing of prior art drilling and the limitation of drill length to processing.

Description

Technical Field

[0001] This invention relates to a method for machining holes in sheet materials, and particularly to a method for machining deep holes in composite honeycomb sandwich panels. Background Technology

[0002] Composite honeycomb sandwich panels are commonly used sandwich structure materials in aerospace interior components. They consist of two layers of composite material panels bonded together with a honeycomb core, which is the central component of the sandwich structure. The honeycomb core is usually made of paper. They not only have high load-bearing capacity and low weight, but also possess advantages such as a smooth aerodynamic surface, sound absorption, heat insulation, and fatigue resistance, thus enjoying widespread application.

[0003] Combined with appendix Figure 1 As shown, the holes processed on the composite honeycomb sandwich panel are formed on the honeycomb core parallel to the panel direction (i.e. perpendicular to the thickness direction of the sandwich panel). The holes traverse the core cells of the honeycomb core. It is inevitable that the paper honeycomb core will be damaged and form burrs after the hole-making machine. Furthermore, such hole orientation makes positioning difficult during processing, and the accuracy of the processed holes cannot be guaranteed.

[0004] The common method currently used is to fill the areas of the honeycomb core that need to be drilled with potting compound, let it cure and solidify before drilling to solve the burr problem. However, for deep holes (generally referring to depths exceeding 0.5 meters), excessively long drill bits will wobble during processing, causing the potting compound to break. The drilled holes cannot meet the requirements for positional accuracy, inner wall roughness, and dimensions, which also makes composite honeycomb sandwich panels unsuitable for high-precision mating scenarios. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to provide a method for processing deep holes in composite honeycomb sandwich panels, thereby improving the problems of burrs and poor hole quality in paper honeycomb cores caused by drilling methods.

[0006] Technical solution: A method for deep hole processing of composite honeycomb sandwich panels, comprising the following steps:

[0007] Step S10: When manufacturing sandwich panels, pre-fill the areas of the honeycomb core to be processed with potting compound and allow it to cure;

[0008] Step S20: Starting from one side panel surface of the sandwich panel, mill a groove into the honeycomb core parallel to the thickness direction of the sandwich panel, with one end of the groove penetrating the circumferential side of the sandwich panel;

[0009] Step S30: Place the precast tube into the settling tank, with the inner hole of the precast tube matching the hole to be processed;

[0010] Step S40: Fill the settling tank with potting compound until it is flush with the panel surface, and fix the precast tube;

[0011] Step S50: Cover the recessed area with dry glass cloth on the panel surface and bond the dry glass cloth by applying resin adhesive.

[0012] Step S60: After the resin has cured, smooth the edges of the dry glass cloth.

[0013] Furthermore, in step S50: when covering the recessed area with dry glass cloth on the panel surface, the edge of the dry glass cloth overlaps with the panel surface, and the applied resin adhesive impregnates the dry glass cloth, removing air bubbles and wrinkles during installation.

[0014] Furthermore, two layers of dry glass cloth are laid.

[0015] Furthermore, the upper layer of dry glass cloth covers the edge of the lower layer of dry glass cloth.

[0016] Furthermore, the overlap width between the edge of the dry glass cloth and the panel surface shall not be less than 10mm.

[0017] Furthermore, the position of the milled groove is combined with the prefabricated pipe and the hole to be machined.

[0018] Furthermore, the bottom of the settling tank matches and fits the shape of the bottom of the precast pipe.

[0019] Beneficial effects: The advantages of this invention are: the shape and size of the deep hole to be processed are guaranteed by the prefabricated tube, the position of the groove ensures that the prefabricated tube meets the requirements of the deep hole, it is not limited by the processing tools and processing equipment, the milling of the honeycomb core avoids the burrs of the honeycomb core after processing and does not affect the deep hole, and it can process holes of various depths, improve processing accuracy, expand the application scenarios of composite materials, and make them applicable to high-precision mating scenarios, avoiding the tolerance caused by the wobble of the drill bit length and the limitation of the drill bit length on processing in the existing drilling technology. Attached Figure Description

[0020] Figure 1 A schematic diagram showing the location of holes machined in a composite honeycomb sandwich panel;

[0021] Figure 2 This is the main view of the milled groove;

[0022] Figure 3 A schematic diagram showing the placement of prefabricated pipes in the settling tank;

[0023] Figure 4 This is a schematic diagram of laying dry glass cloth. Detailed Implementation

[0024] The present invention will be further explained below with reference to the accompanying drawings and specific embodiments.

[0025] A method for deep hole processing of composite honeycomb sandwich panels specifically includes the following steps:

[0026] Step S10: When manufacturing the sandwich panel of composite material panel-paper honeycomb core-composite material panel, pre-fill the area of ​​the honeycomb core to be processed with potting compound, and then lay the composite material panel and wait for the potting compound to cure.

[0027] When making holes in the honeycomb core, one end of the hole should be on the circumferential side of the honeycomb core. The potting compound also needs to be filled to the edge of the circumferential side. In the thickness direction of the honeycomb core, the potting compound should be filled to the surface of the honeycomb core that contacts one side panel to ensure the structural strength of the area to be processed.

[0028] Step S20: Combine with the appendix Figure 2 As shown, in the area 4 to be processed, starting from the surface of the panel 1 on the side of the sandwich panel that is in contact with the potting compound, a groove 3 is milled downwards in the direction parallel to the thickness d of the sandwich panel and into the honeycomb core. The length L of the groove is within the sandwich panel, and one end 31 of the groove penetrates the circumferential side 2 of the sandwich panel.

[0029] Step S30: Combine with the attached Figure 3 As shown, a precast tube 5 is placed in the settling tank. The inner hole 51 of the precast tube is consistent with the hole to be processed. The outer edge of the precast tube 5 is flush with the circumferential side of the honeycomb core. The depth of the settling tank should be sufficient to ensure that the precast tube is completely inside after being placed. A height gap is left between the top of the precast tube and the surface of the panel 1.

[0030] Ideally, the bottom of the sink should match the shape of the bottom of the precast tube. It is not limited to a curved surface fit. This can provide good support and positioning for the precast tube. When the sink is milled, the positional accuracy of the precast tube and the hole to be processed can be guaranteed to meet the positional requirements of the hole to be processed.

[0031] The shape of the inner hole of the precast tube is not limited to a round hole; the inner hole of the precast tube is the deep hole to be processed in the composite honeycomb sandwich panel.

[0032] Step S40: Combine with the appendix Figure 4 As shown, fill the sink with potting compound 6 to fill the gap between the precast tube and the sink until it is flush with the surface of panel 1. The potting compound can cure at room temperature to fix the precast tube.

[0033] Step S50: Cover the sink area with dry glass cloth on the panel surface.

[0034] Combined with appendix Figure 4As shown, it is best to apply two layers of dry glass cloth. First, apply resin adhesive to the recessed area and its surroundings. Then, lay dry glass cloth 71 to cover the recessed area, ensuring the edges of the dry glass cloth overlap with the panel surface with an overlap width of at least 10mm. Next, apply resin adhesive to dry glass cloth 71 to completely saturate it. Then, lay another layer of dry glass cloth 72 on top of dry glass cloth 71, covering the edges of dry glass cloth 71. The edges of dry glass cloth 72 overlap with the panel surface with an overlap width of at least 10mm. Finally, apply resin adhesive to dry glass cloth 72 to completely saturate it. When laying dry glass cloth after saturating it with resin adhesive, air bubbles and wrinkles should be removed to improve surface quality.

[0035] Step S60: After the resin adhesive has cured, the dry glass cloth can be bonded and fixed. Use 120-grit sandpaper to sand the edges of the dry glass cloth until smooth and free of protrusions or burrs.

[0036] Once the above steps are completed, deep hole machining is finished on the composite honeycomb sandwich panel.

[0037] The processing method of this invention ensures the shape and size of the deep hole to be processed by using a pre-made tube, and the position of the countersink ensures that the pre-made tube meets the requirements of the deep hole. It is not limited by processing tools and processing equipment. The milling of the honeycomb core avoids burrs on the honeycomb core after processing and does not affect the deep hole. Moreover, it can process holes of various depths, improve processing accuracy, expand the application scenarios of composite materials, and make them applicable to high-precision mating scenarios. It avoids the tolerance caused by drill bit length wobble and the limitation of drill bit length on processing in existing drilling technology.

Claims

1. A method for deep hole machining of a composite honeycomb sandwich panel, characterized by The method comprises the following steps: Step S10: When manufacturing the sandwich panel, prefill the potting adhesive in the area of the honeycomb core to be machined and solidify; Step S20: From the surface of one side panel of the sandwich panel, mill the groove into the honeycomb core in parallel to the thickness direction of the sandwich panel, one end of the groove penetrates the circumferential side of the sandwich panel; Step S30: Place the prefabricated tube into the groove, the hole in the prefabricated tube is consistent with the hole to be machined; the outer edge of the prefabricated tube is flush with the circumferential side of the honeycomb core, the depth of the groove satisfies that the prefabricated tube is placed into the groove completely, the hole in the prefabricated tube is the deep hole to be machined on the composite honeycomb sandwich panel; Step S40: Fill the potting adhesive into the groove until it is flush with the surface of the panel to fix the prefabricated tube; Step S50: Lay the dry glass cloth on the surface of the panel to cover the groove area, and bond the dry glass cloth by brushing the resin adhesive; Step S60: After the resin adhesive is solidified, polish the edge of the dry glass cloth to be smooth.

2. The method of claim 1, wherein: In step S50, when laying the dry glass cloth on the surface of the panel to cover the groove area, the edge of the dry glass cloth overlaps the surface of the panel, the resin adhesive is brushed to soak the dry glass cloth, and the laying removes bubbles and wrinkles.

3. The method according to claim 1 or 2, wherein: The dry glass cloth is laid in two layers.

4. The method of claim 3, wherein the method further comprises: The upper layer of dry glass cloth covers the edge of the lower layer of dry glass cloth.

5. The method of claim 2, wherein the method further comprises: The width of the overlap between the edge of the dry glass cloth and the surface of the panel is not less than 10 mm.

6. The method of claim 1, wherein: The position of the milled groove is combined with the prefabricated tube and the hole to be machined.

7. The method of claim 1, wherein: The shape of the bottom of the groove matches the bottom of the prefabricated tube.

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