CN112026204B

CN112026204B - Compression molding method and pre-compaction mold for antenna housing

Info

Publication number: CN112026204B
Application number: CN202010832105.9A
Authority: CN
Inventors: 周蜜
Original assignee: Sichuan Jiuzhou Electric Group Co Ltd
Current assignee: Sichuan Jiuzhou Electric Group Co Ltd
Priority date: 2020-08-18
Filing date: 2020-08-18
Publication date: 2022-04-26
Anticipated expiration: 2040-08-18
Also published as: CN112026204A

Abstract

The invention relates to a compression molding method and a pre-compaction mold for an antenna housing, belongs to the technical field of composite material compression molding, and solves the problems that in the existing compression molding process, when a female mold and a male mold are closed, the conditions of fiber extrusion, protrusion or cavity and material shortage are generated at the closed position, so that the fiber fracture is caused, and the mechanical strength of the closed position is influenced. The compression molding method of the radome comprises the following steps: step 1: analyzing the structure of the workpiece to determine the parts which are easy to have problems when the workpiece is subjected to compression molding; step 2: designing a plurality of thickness gradients according to the thickness of the part with larger thickness; and step 3: designing a pre-compaction die; and 4, step 4: laying and performing pre-compaction; and 5: and (5) closing the mold and curing and molding. According to the invention, the pre-compaction die is used for compacting the local part for multiple times, so that the conditions of fiber extrusion, protrusion or cavity and material shortage at the die assembly position are avoided, the fiber fracture is further avoided, and the mechanical strength at the die assembly position is ensured.

Description

Compression molding method and pre-compaction mold for antenna housing

Technical Field

The invention relates to the technical field of composite material compression molding, in particular to a compression molding method and a pre-compaction mold for an antenna housing.

Background

Compression molding is a very widely applied method in composite material molding, which accounts for about 10% of the total consumption distribution of composite material products, and the method is a method for adding a certain amount of prepreg or prepreg into a mold consisting of a female mold and a male mold, and curing the preform into a finished piece at a certain temperature and pressure. The main advantages of the compression molding process are: the product is formed in one step, the dimensional accuracy of the product is high, the repeatability is good, the surface is smooth and clean, and secondary processing is not needed or the secondary processing amount is small; the production efficiency is high, the professional and automatic production is convenient to realize, the manufacturing cost can be effectively reduced, and the method is suitable for preparing small and medium-sized composite parts in batch production.

At present, the raw materials for compression molding are prepreg or plastic balls, and especially the prepreg has excellent structural strength due to continuous fibers and is widely applied. Since radomes are generally exposed to the environment and directly attacked, more and more radomes are manufactured by a compression molding method. However, in the process of compression molding, after a preform made of prepreg is laid, when a female mold and a male mold are closed, the volume of a part of the preform (especially a part with an excessively thick prepreg lay thickness) is larger than that of a mold cavity, so that fiber extrusion and protrusion are caused in the part during closing, and fiber breakage, voids or material shortage is caused. When the die is used subsequently, the die-closing seam is cracked, so that the mechanical strength is reduced, and potential safety hazards are formed.

Disclosure of Invention

In view of the above analysis, the present invention aims to provide a compression molding method and a pre-compaction mold for an antenna cover, in which a pre-compaction mold is used to locally compact, and during the compression molding process, when a female mold and a male mold are closed, the conditions of fiber extrusion, protrusion, cavity or material shortage at the closed position are avoided, so as to avoid fiber fracture and ensure the mechanical strength at the closed position.

The purpose of the invention is mainly realized by the following technical scheme:

a compression molding method of an antenna housing comprises the following steps:

step 1: analyzing the structure of the workpiece to determine the parts which are easy to have problems when the workpiece is subjected to compression molding;

step 2: designing a plurality of thickness gradients according to the thickness of the part with larger thickness;

and step 3: designing a pre-compaction die;

and 4, step 4: laying and performing pre-compaction;

and 5: and (5) closing the mold and curing and molding.

Further, in the step 1, the part to be pre-compacted is a bending part of the radome.

In step 2, each thickness gradient is 2-3mm, and the number of gradients n is equal to the total thickness of the portion to be precompacted/the thickness of a single thickness gradient.

Furthermore, the number of the thickness gradients is 3, a pre-compaction die is used for the first thickness gradient and the second thickness gradient, and a forming die is used for the third thickness gradient.

Further, the step 4 specifically includes: laying prepreg on a male die of a forming die, and when the laying thickness of the prepreg at a bending position is laid to a first thickness gradient, pressing by using a first group of pre-compaction dies; and when the thickness of the prepreg layup at the bending part is laid to a second thickness gradient, pre-pressing by using a second group of pre-pressing dies.

Further, the pressing time in the step 4 is 10-15 minutes.

A pre-compaction die for a radome compression molding method is disclosed, wherein each group of pre-compaction dies comprises two matched dies.

Furthermore, the pre-compaction die is provided with a groove, and the shape of the groove corresponds to the shape of the antenna housing.

Furthermore, the pre-compaction die is provided with a bottom plate, and after the pre-compaction die is closed, the bottom plate is positioned at the bottom of the antenna housing, so that the pre-compaction effect can be prevented from being influenced by the fact that the pre-compaction die moves upwards relative to the prepreg paved on the male die of the forming die after being closed.

Furthermore, fastening mounting holes are formed in two ends of the pre-compaction die.

The invention can realize at least one of the following beneficial effects:

(1) the invention adopts a method of multiple compaction of a plurality of moulds, and solves the problems that local fiber extrusion and protrusion occur at the local part during mould closing, and further fiber fracture or void and material shortage occur due to the fact that the local volume of a pre-formed body (especially at the part with excessively thick prepreg laying thickness) is larger than the cavity of a female mould of the mould.

(2) The invention adopts multiple prepressing to discharge the gas among all layers of the prepreg in advance so as to ensure that the layers are laminated and achieve the effect of improving the interlayer laminating force.

(3) The invention adopts multiple prepressing to ensure that the layers are tightly attached, thereby avoiding the problem that the local volume is larger than the mold cavity when the mold is finally closed.

In the invention, the technical schemes can be combined with each other to realize more preferable combination schemes. Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and drawings.

Drawings

The drawings are only for purposes of illustrating particular embodiments and are not to be construed as limiting the invention, wherein like reference numerals are used to designate like parts throughout.

Fig. 1 is a front view of a radome of an embodiment of the present invention;

FIG. 2 is a cross-sectional view A-A of FIG. 1;

FIG. 3 is a schematic structural view of embodiment 1 of the pre-compaction mold according to the invention;

FIG. 4 is a cross-sectional view B-B of FIG. 3;

FIG. 5 is a schematic structural view of example 2 of a pre-compaction mold according to the present invention;

fig. 6 is a cross-sectional view C-C of fig. 5.

Reference numerals:

1-upper part, 2-lower part, 3-bending part.

Detailed Description

The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form a part hereof, and which together with the embodiments of the invention serve to explain the principles of the invention and not to limit its scope.

In the description of the embodiments of the present invention, it should be noted that, unless otherwise explicitly stated or limited, the term "connected" should be interpreted broadly, and may be, for example, a fixed connection, a detachable connection, an integrated connection, a mechanical connection, an electrical connection, a direct connection, or an indirect connection via an intermediate medium. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

Example 1

One embodiment of the present invention, as shown in fig. 1 to 2, discloses a compression molding method of a radome. The method comprises the following specific steps:

step 1: analyzing the structure of the workpiece to determine the part which is easy to have problems when the workpiece is subjected to compression molding:

the part which is easy to cause problems during compression molding is the part with larger local thickness of the part. When the prepreg is laid, the prepreg is integrally laid, after a plurality of layers are passed, the laying of the part with smaller thickness is suspended, the part with larger thickness is continuously laid, and when the part with larger thickness reaches a certain thickness, the prepreg is integrally laid. Because of the thickness of every layer of preimpregnation material is unanimous, the great position of local thickness can be more than the preimpregnation material number of piles of other positions when the preimpregnation material is spread the layer, and the number of piles is many to make the volume at this position great, and after the laying is accomplished, the size at this position is greater than forming die's die cavity size, and the great position fibre of thickness is extruded, is formed protrudingly when causing the compound die, and then causes the fibre fracture at this position, or the problem that appears cavity, scarce material.

The thickness of the antenna housing of a certain model at the upper part 1 is 2mm, the thickness of the lower part 2 is 1.5mm, and the thickness of the bending part 3 is the thickest and is 6.82 mm. Great thickness difference for when the preimpregnation material was spread the layer, the department of bending 3 can be more than the preimpregnation material number of piles of other positions, and multilayer preimpregnation material can make the volume of department of bending 3 great, and be greater than the size of forming die cavity, the extrusion and the arch of this department fibre when causing the compound die.

Step 2: according to the thickness of the workpiece, designing a plurality of thickness gradients:

in the embodiment, 2-3mm is adopted as a thickness gradient, and if the thickness of the set gradient is too small, the number of pre-compaction dies is increased, the production cost is increased, the operation times are increased, and the production efficiency is reduced; if the set gradient thickness is too large, the fiber extrusion and protrusion are still easy to occur in the pre-compaction operation process, and the pre-compaction purpose cannot be achieved. The number of gradients n is (total thickness of the site to be precompacted/single gradient thickness).

Aiming at the antenna housing in the step 1, the part needing to be pre-compacted is positioned at a bending part 3, the thickness of the bending part 3 is 6.82mm, 3 thickness gradients are designed according to the principle that the number n of the gradients is equal to (total thickness/gradient thickness), and the number n of the gradients is equal to 3.41 (6.82mm/2mm), wherein a pre-compacting mold is used for the first thickness gradient and the second thickness gradient, and a forming mold is used for the third thickness gradient, so that two groups of pre-compacting molds need to be designed.

And step 3: designing a pre-compaction die:

the molding die for compression molding is divided into a male die and a female die, when the molding die is used, prepreg is laid on the surface of the male die, and after the prepreg is laid, the prepreg is compacted by the female die. The pre-compaction die is matched with a male die of a forming die for use, so that the pre-compaction die has the function of a female die. The pre-compaction tool is part of the negative of the forming tool in view of its shape. Since the pre-compaction is performed only for the portions having a large thickness, only the portions having a large thickness need to be considered when manufacturing the pre-compaction mold, and the portions having a small thickness are ignored. In the process of laying and pasting the prepreg, only a pre-compaction mould and a male mould are used, and a forming mould is not used until the laying and pasting are finished finally.

The shape of the pre-compaction die can be designed according to the shape of a female die of the forming die, and the pre-compaction die is regular, simple and convenient to design and process. The mold closing mode of the pre-compaction mold is the same as that of a female mold of the forming mold, and a fastening device convenient to lock is designed, so that the effects of convenient pre-compaction and pre-compaction are achieved. After the pre-compaction die and the forming die are matched, the shape of the formed internal cavity is similar to the shape of the cavity of the corresponding part formed after the forming die is matched. For the antenna housing in the step 1, the ratio of the size of a cavity formed after the first group of pre-compaction molds and the male molds are closed to the size of a cavity formed after the forming molds are closed is 2: 6.82, the ratio of the size of the cavity formed by the second group of precompacted dies and the male die after die assembly to the size of the cavity formed by the forming die after die assembly is 4: 6.82.

and 4, step 4: laying and pre-compacting:

and (3) starting to lay the prepreg layer by layer on a male die of a forming die, and when the thickness of the prepreg layup at the bending part 3 is laid to a first thickness gradient (such as 2mm), using a first group of pre-compaction dies and installing the pre-compaction dies on the male die of the forming die paved with the preformed body in a left-right die closing mode. And after the die assembly is finished, fastening the pre-compaction die by using a screw, and keeping the pre-compaction die in a fastened state for 10-15 minutes to ensure that the prepreg is tightly attached. After the completion, the fastening screws are loosened, the pre-compaction die is taken down, the prepreg is continuously used for paving on the forming die male die until the thickness of the bending part reaches a second thickness gradient (such as 4mm), and then the pre-compaction is carried out by using a second group of pre-compaction dies, wherein the method is the same as the above method. After all the layups are completed, the preform is compacted using the negative of the forming die. Because the local over-thick part is pre-compacted in advance, the bent part 3 can not extrude the fiber because of the local over-thickness when the die is closed, and the fiber fracture at the die closing part is avoided.

And 5: and (3) die assembly and curing molding:

after the final lay-up is complete, the female and male moulds are closed. When the die is closed, the die is closed quickly, and when the female die is in contact with the prepreg quickly, the closing speed is reduced. The mold is quickly closed, so that the non-production time is shortened, the production efficiency is improved, the mold closing speed is reduced when the female mold is in quick contact with prepreg, the raw materials in the mold cavity can be prevented from being brought out by air due to too fast mold closing, the gas in the mold can be fully removed, and the defects of bubbles, sand holes and the like are reduced.

And increasing the pressure to heat and pressurize the raw materials when the die is closed. According to the compression molding process, putting the molded mold into an oil press, heating at a heating rate of not more than 1.5 +/-0.5 ℃/min, and keeping the temperature for 0.5-1 hour when the temperature is raised to 60-80 ℃ so as to fully preheat the blank; and then continuously heating to the curing temperature of the prepreg resin, specifically 120-150 ℃, and carrying out heat curing molding after heat preservation for 1-3 hours. And after the heat preservation is finished, cooling at a cooling rate of not more than 1.5 +/-0.5 ℃/min, and when the temperature is reduced to be below 60 ℃, demolding the radome by using a detachable mold to obtain the radome with the required model.

Example 2

As shown in fig. 3 and 4, the embodiment of the present invention provides the pre-compaction molds of example 1, each set of pre-compaction molds includes two paired left and right molds. In this embodiment, the radome has a bilateral symmetry structure, so that the left and right matched-mode structures are symmetrical. The pre-compaction die is designed according to the shape of the antenna housing, and can also be designed into an upper die and a lower die or an asymmetric die and the like.

The embodiment includes two sets of pre-compaction molds, and according to the shape of the radome, the pre-compaction molds are cuboids provided with grooves, the shapes of the grooves correspond to the shape of the radome, and the pre-compaction molds are a part of a female mold of a forming mold. The pre-compaction die can also be designed into other shapes, and the whole body can meet the requirements of regularity, simplicity and convenience in design and processing. The height of the pre-compaction die needs to ensure that the pre-compaction die can completely wrap the bending part 3 of the antenna housing after die assembly. The first group of pre-compaction dies and the second group of pre-compaction dies have the same shape, and the depth of the grooves is different. After the first group of pre-compaction dies and the forming die male die are assembled, the thickness of the formed cavity at the bending part 3 is 2mm, and after the second group of pre-compaction dies and the forming die male die are assembled, the thickness of the formed cavity at the bending part 3 is 4 mm. And fastening mounting holes are formed in two ends of the precompaction die and used for fixing the left matched die and the right matched die after die assembly.

Further, as shown in fig. 5 and 6, the pre-compaction mold is provided with a bottom plate, and when the left and right matched molds of the pre-compaction mold are closed, the bottom plate is located at the bottom of the radome, so that the pre-compaction effect is prevented from being influenced by upward movement of the pre-compaction mold relative to the prepreg laid on the male mold of the forming mold after the pre-compaction mold is closed.

Comparative example

The invention discloses a compression molding method of an antenna housing, which comprises the following specific steps:

s1, laying prepreg on the forming die male die:

and (2) using prepreg to lay on a male die of a forming die layer by layer, wherein the prepreg is integrally laid firstly when being laid, after a plurality of layers are passed, the part with smaller thickness is suspended to be laid, the part with larger thickness is continuously laid, and when the part with larger thickness reaches a certain thickness, the whole layer is laid again until the whole layer is completely laid.

S2, mold closing and curing molding:

after the final lay-up is complete, the female and male moulds are closed. The method of closing the mold is the same as in step 5 of example 1. And (3) increasing the pressure to heat and pressurize the raw materials for curing and forming after the mold is closed, wherein the curing and forming method and parameters are the same as those in the step 5 of the embodiment 1.

The mold clamping gap of the radome obtained by using the methods of example 1 and this comparative example was measured, respectively, and the mold clamping gap section was observed under a microscope, and the obtained results are shown in table 1. It can be seen from table 1 that, for the radome obtained by the method of embodiment 1 of the present application, the mold closing gaps are uniform and consistent, and are all 0.1mm, and the dimensional stability is good, while for the radome obtained by the method of the comparative example, the mold closing gaps are all larger than 0.35mm, the maximum gap reaches more than 0.5mm, and the mechanical property of the radome is affected by the excessively large mold closing gap, so that the service life of the radome is reduced. The mold closing seam section of the radome obtained by the method of example 1 is observed under a microscope, the section fiber is flat and continuous, and is free of extrusion bulge, while the mold closing seam section of the radome obtained by the method of comparative example is in a crater shape, the fiber is broken, an excessively large mold closing gap and poor mold closing seam section conditions are caused, and a large number of radomes are scrapped. Therefore, the antenna housing obtained by the method in the embodiment 1 of the application has the advantages of small die assembly gap, good dimensional stability, smooth and continuous die assembly seam section fibers of the antenna housing, effective improvement of mechanical strength at the die assembly position and improvement of the service life of the antenna housing.

Table 1 radome parameters for example 1 and comparative examples

In summary, according to the method for improving the local strength of the compression molding composite material provided by the embodiment of the invention, in the compression molding process, when the female mold and the male mold are closed, the conditions of fiber extrusion, protrusion or cavity and material shortage at the closed position are avoided, so that the fiber fracture is avoided, and the mechanical strength at the closed position is ensured.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention.

Claims

1. A compression molding method of an antenna housing is characterized by comprising the following steps:

step 2: designing a plurality of thickness gradients according to the thickness of the workpiece;

and step 3: designing a pre-compaction die;

and 4, step 4: laying and performing pre-compaction;

and 5: closing the mold and curing and molding;

in the step 2, each thickness gradient is 2-3mm, and the number n of the thickness gradients is = the total thickness of the part needing pre-compaction/the thickness of a single thickness gradient;

the first n-1 thickness gradients use a pre-compaction die, and the nth thickness gradient uses a forming die;

the molding die formed by compression molding is divided into a male die and a female die, when the molding die is used, prepreg is laid on the surface of the male die, and after the laying is finished, the prepreg is compacted by the female die; the pre-compaction die is matched with a male die of a forming die for use;

the step 4 specifically comprises the following steps: laying prepreg on a male die of a forming die, and pressing the prepreg by using a group of corresponding pre-compaction dies when n-1 thickness gradients are laid before laying;

each group of pre-compaction dies comprises two matched dies, each pre-compaction die is provided with a groove, and the shape of each groove corresponds to the shape of the antenna housing;

in appearance, the pre-compaction die is a part of a female die of the forming die; the pre-compaction is only performed on the part with larger thickness, so that the part with larger thickness is only needed to be considered when the pre-compaction die is manufactured, and the part with thinner thickness is ignored;

the pre-compaction die is provided with the bottom plate, and after the pre-compaction die is closed, the bottom plate is positioned at the bottom of the antenna housing, so that the pre-compaction effect can be prevented from being influenced by the fact that the pre-compaction die moves upwards relative to prepreg paved on a male die of a forming die after being closed;

and fastening mounting holes are formed at two ends of the pre-compaction die.

2. A compression molding method for a radome according to claim 1, wherein in the step 1, the portion to be pre-compacted is a bending portion (3) of the radome.

3. A compression molding method for a radome according to claim 1, wherein the pressing time in step 4 is 10 to 15 minutes.