CN114083725B

CN114083725B - Mold for preparing pyramid lattice core and preparation method of pyramid lattice core

Info

Publication number: CN114083725B
Application number: CN202111375902.XA
Authority: CN
Inventors: 熊健; 刘青旭; 高英
Original assignee: Harbin Institute of Technology
Current assignee: Harbin Institute of Technology
Priority date: 2021-11-19
Filing date: 2021-11-19
Publication date: 2023-01-13
Anticipated expiration: 2041-11-19
Also published as: CN114083725A

Abstract

A mold for preparing a pyramid lattice core and a preparation method of the pyramid lattice core belong to the field of mold compression molding. The invention aims to solve the problems of poor molding quality and complex mold operation of the existing pyramid lattice core material. The invention comprises an upper die and a lower die; the upper die is made of a plurality of upper die unit cells which are arranged in an array form, the upper surfaces of the upper die unit cells are inwards concave to form grooves, bulges are arranged in the grooves of the upper die unit cells, and the shapes of the bulges are the same as the shapes of the prefabricated inverted pyramid lattice unit cell structures; the lower die is made by arranging a plurality of lower die unit cells in an array form, the upper surface of each lower die unit cell is protruded outwards to form a boss, a limit groove is formed on the boss of each lower die unit cell, and the structural shape of each limit groove is the same as that of a prefabricated pyramid lattice unit cell; the upper die unit cell in the upper die is matched with the lower die unit cell in the lower die. The method is mainly used for preparing the pyramid lattice core.

Description

Mold for preparing pyramid lattice core and preparation method of pyramid lattice core

Technical Field

The invention belongs to the field of mold compression molding, and particularly relates to a mold for preparing a pyramid lattice core and a preparation method of the mold.

Background

The pyramid lattice sandwich structure prepared by the fiber reinforced material has the advantages of light weight, high specific stiffness, high specific strength, strong designability and the like, and has the potential of realizing the multifunctional characteristic of integrating bearing, heat transfer, heat insulation, energy absorption, energy storage and damping. At present, methods for preparing a fiber reinforced material pyramid lattice sandwich plate include a three-dimensional weaving method, a water cutting-assembling method, a 3D printing method, a hot pressing mold one-step forming method, a hot pressing mold two-step forming method and the like, but pyramid lattice cores prepared by the methods all have certain problems, and the methods are as follows:

1. three-dimensional weaving method: the specific process comprises the steps of preparing a panel and a prepreg fiber bundle, inserting the prepreg fiber bundle between an upper panel and a lower panel back and forth by taking the panel as a reference to form a dot matrix sandwich structure core, and then curing and forming to form the dot matrix sandwich structure. The method realizes the preparation of the composite material three-dimensional lattice sandwich structure for the first time, but the lattice core rod has the defect of irregularity, and can not bear pressure in the radial direction during the forming.

2. Water cutting-assembling method: the method comprises the following steps of firstly preparing a composite material laminated plate by using prepreg, then cutting a composite material lattice structure rod piece with a notch on the laminated plate according to a preset size by using a water cutting technology, finally assembling the cut rod piece into a lattice core body, and gluing the lattice core body with an upper panel and a lower panel to prepare the fiber reinforced lattice sandwich plate. The method is simple and easy to operate, but the composite material is sensitive to a cutting process and is easy to generate layering damage.

3. 3D printing method: the 3D printing technology is additive manufacturing technology, can make various complicated, irregular structures, and is relatively simple and convenient to operate, the structures made of metal materials, resin materials and the like can be printed at present, for the fiber reinforced composite material structure, the 3D printing of the short fiber composite material is mature at present, but the performance is poor, the 3D printing technology of the long fiber reinforced composite material structure is not mature, the structural potential of a lattice structure can not be fully exerted, and the 3D printing technology has a step effect and can seriously influence the performance of the structure.

4. One-step forming method of the hot pressing mold: the process of the hot pressing mold one-step forming method comprises the following steps: the method comprises the steps of firstly manufacturing a prepreg of a fiber reinforced material into a circular rod piece, inserting the circular rod piece into a preset position in a hot-pressing die, respectively laying a part of the prepreg of the fiber reinforced material on an upper panel and a lower panel of the hot-pressing die, then pressing two ends of the prepared circular rod piece onto the laid prepreg, finally laying a part of the fiber reinforced prepreg, and curing and molding to prepare the fiber reinforced composite dot matrix sandwich structure. The surface core performance of the lattice sandwich board prepared by the method is good, but the molding quality of the core bar is not good enough, and the core bar is easy to layer.

5. Carrying out secondary forming on a hot-pressing die: the hot-pressing mold secondary forming method refers to a method for forming a sandwich structure by independently forming a panel and a core body and then gluing the panel and the core body together, and the specific process comprises the following steps: the method comprises the steps of firstly cutting a prepreg into preset prepreg bundles, then paving the cut bundle-shaped prepreg on a special mould, then closing the mould, fixing, putting the mould into a hot press or a hot pressing tank for curing to finish the preparation of the dot matrix core, and simultaneously preparing an upper panel and a lower panel, and gluing the upper panel and the lower panel with the core to prepare the dot matrix sandwich panel.

The pyramid lattice cores prepared by the five methods have the problems of poor molding quality, complex mold operation and low efficiency.

Disclosure of Invention

In order to solve the technical problems, the invention provides a mold for preparing a pyramid lattice core and a preparation method of the mold.

The technical scheme adopted by the invention for solving the technical problems is as follows:

the mold for preparing the pyramid lattice core comprises an upper mold and a lower mold; the upper die is integrally formed by arranging a plurality of upper die unit cells in an array form, the upper surfaces of the upper die unit cells are inwards sunken to form grooves, bulges are arranged in the grooves of the upper die unit cells, and the shapes of the bulges are the same as those of a prefabricated inverted pyramid lattice unit cell structure; the lower die is formed by integrally arranging a plurality of lower die unit cells in an array form, the upper surfaces of the lower die unit cells protrude outwards to form bosses, limiting grooves are formed in the bosses of the lower die unit cells, and the structural shapes of the limiting grooves are the same as those of a prefabricated pyramid lattice unit cell; the upper die unit cell in the upper die is matched with the lower die unit cell in the lower die.

The preparation method of the pyramid lattice core comprises the following specific preparation processes:

step 1: cleaning the upper die and the lower die by using acetone, and uniformly coating a release agent on the bulges of the upper die and the limiting grooves of the lower die, or uniformly sticking release paper on the bulges of the upper die and the limiting grooves of the lower die;

step 2: pre-laying carbon fiber prepreg along a limiting groove of a lower die;

and step 3: buckling an upper mould on a lower mould paved with carbon fiber prepreg, compacting, sealing the whole mould in a vacuum bag, vacuumizing, checking whether the sealing bag leaks air, putting the sealed bag into an autoclave or directly putting the sealed bag into a hot press for curing and forming, setting the hot pressing temperature to be 130 ℃, setting the pressure to be 0.3MPa, and keeping the temperature for 90 minutes;

and 4, step 4: and taking the cured pyramid lattice core out of the autoclave or the hot press, and removing the upper die and the lower die when the temperature is reduced to normal temperature to obtain the fiber reinforced composite pyramid lattice core.

Compared with the prior art, the invention has the following beneficial effects:

1. the mold has few components, does not need secondary assembly and is easy to carry and store;

2. the prepreg is convenient to lay, and the die can be closed without secondary fixation;

3. in the process of manufacturing a pyramid core in the past, the side is not restrained, pressure can not be applied to the side, the molding quality of the top surface and the bottom surface can only be guaranteed, the position of the prepreg is limited by the limiting groove edge on the die in the application, the side of the prepreg can also receive pressure in the curing process, the whole part of the core rod is uniformly pressed, the molding quality is good, the condition that the side of the core is uneven due to the fact that the pressure of the traditional hot-pressing die only in the vertical direction can not occur, and the problem that the molding quality of the side of the core is not good due to the fact that the prepreg is extruded from the side can not occur.

Drawings

FIG. 1 is a top view of a lower mold;

FIG. 2 is an isometric view of the lower mold;

FIG. 3 is a side view of the lower mold;

FIG. 4 is a front view of the lower mold;

FIG. 5 is a top view of a lower mold unit cell;

FIG. 6 is a side view of a bottom die unit cell;

FIG. 7 is an isometric view of a bottom die unit cell;

FIG. 8 is an isometric view of the upper mold;

FIG. 9 is a side view of the upper mold;

FIG. 10 is a front view of the upper mold;

FIG. 11 shows two forms of carbon fiber prepreg, 11a carbon fiber prepreg cloth, 11b prepreg tape, and 11c prepreg web;

FIG. 12 is a schematic view showing a process of manufacturing a pyramid-lattice core using a mold, in which 12a is a schematic view showing a state where a prepreg web is interposed between an upper mold and a lower mold, 12b is a schematic view showing a hot-pressing process of the pyramid-lattice core, and 12c is a pyramid-lattice core formed by curing;

FIG. 13 is a schematic structural diagram of a pyramid lattice core unit cell;

FIG. 14 is a schematic structural diagram of model one;

FIG. 15 is a schematic structural diagram of model two;

FIG. 16 is a schematic diagram of the arrangement of pyramid lattice core unit cells;

FIG. 17 is a schematic structural diagram of model III;

FIG. 18 is a schematic structural diagram of model four;

fig. 19 is an isometric view of a mold cell.

Detailed Description

The technical solution of the present invention is further described by the specific embodiments with reference to fig. 1 to 19 below:

as shown in fig. 11, the mold for preparing the pyramid-shaped lattice core comprises an upper mold 1 and a lower mold 2;

as shown in fig. 8, 9, 10 and 19, the upper mold 1 is integrally formed by arranging a plurality of upper mold unit cells 1-1 in an array form, the upper surface of the upper mold unit cell 1-1 is recessed inwards to form a groove, a protrusion is arranged in the groove of the upper mold unit cell 1-1, and the shape of the protrusion is the same as that of a pre-prepared inverted pyramid lattice unit cell structure;

as shown in fig. 1 and fig. 2, the lower mold 2 is integrally formed by arranging a plurality of lower mold unit cells 2-1 in an array form, the upper surface of the lower mold unit cell 2-1 protrudes outwards to form a boss, a limiting groove 2-1-1 is formed on the boss of the lower mold unit cell 2-1, and the structural shape of the limiting groove 2-1-1 is the same as that of a pre-prepared pyramid lattice unit cell;

the number of the upper mould unit cells 1-1 in the upper mould 1 is the same as that of the lower mould unit cells 2-1 in the lower mould 2, and the upper mould unit cells and the lower mould unit cells are matched; the width of laying preimpregnation material prepreg in the spacing groove is the same with the width of spacing groove and is compressed tightly by the arch on the last mould unit cell, all produce the restriction to the higher authority, below, left side and the right side of preimpregnation material for prepreg all-round all receives pressure at the in-process of solidification, and the side shaping of core is of high quality, and traditional heated press mold can not appear and only have the pressure of upper and lower direction and lead to the uneven condition of core side, also can not appear prepreg and extrude from the side and lead to the not good problem of core side shaping quality.

The cross section of the lower die unit cell 2-1 is square; the boss on the lower die unit cell 2-1 comprises an upper plane 2-1-3 and four identical slope surfaces 2-1-2, a cross-shaped groove 2-1-1-2 is formed in the upper plane 2-1-3, a convex rib is formed between every two adjacent slope surfaces, a core rod groove 2-1-1-1 is formed in each slope surface, the inclination of the core rod groove 2-1-1-1 is identical to that of the slope surfaces, prepreg is convenient to lay, the top ends of the four core rod grooves 2-1-1-1 are respectively connected with a supporting groove of the cross-shaped groove 2-1-2, and the four core rod grooves 2-1-1-1 and the cross-shaped groove 2-1-2 jointly form a limiting groove 2-1-1.

As shown in fig. 5, 6 and 7, the bottom ends of the core bar grooves 2-1-1-1 are isosceles right triangle groove bodies, a groove is formed between the four lower mold unit cells 2-1 which are circumferentially arranged, and the isosceles right triangle groove bodies at the bottom ends of the four core bar grooves 2-1-1-1 in the groove jointly form a cross flower-shaped groove body.

In the embodiment, the upper die 1 and the lower die 2 are made of silicon rubber, and when the pyramid lattice core is prepared by using the silicon rubber die, the prepreg is extruded and formed by using the expansion pressure of the silicon rubber die, so that the pressure applied to the prepreg tape is uniform, and the quality of the formed pyramid lattice core is more excellent;

if the high-temperature silicon rubber is adopted to manufacture the mould, the mould needs to be subjected to shell extraction treatment in mould software, the mould needed for manufacturing the mould is designed, then PVC resin is printed out in a 3D printing mode, the needed liquid high-temperature silicon rubber is blended and poured into the printed mould, the mixture is cured for about 48 hours at room temperature, and then the mould manufactured by the high-temperature silicon rubber can be obtained after demoulding; the high-temperature silica gel mold is light in weight, easy to manufacture and low in cost, but the reuse rate is low, the use loss is large, the limit tolerance temperature of the commonly used silica gel is only about 300 ℃, and the high-temperature silica gel mold is difficult to apply to some materials which can be solidified only at high temperature, such as a thermoplastic composite material of which the base body is PEEK.

In the present embodiment, the upper mold 1 and the lower mold 2 are made of an alloy material; if the alloy material is adopted for manufacturing, a cutting processing mode is adopted, a mold unit cell is designed after a pyramid structure unit cell is selected, and an upper mold and a lower mold are respectively processed after the detailed size is determined; the die made of the alloy material has the advantages of high temperature resistance, high pressure resistance, small use loss and long-time repeated use, but has the problems of heavy weight, high material cost, difficult manufacture and the like.

In the embodiment, the upper die 1 and the lower die 2 are made of high-temperature nylon; if the high-temperature nylon is adopted to prepare the mold, the mold can be directly printed out in a 3D mode by adopting a high-performance nylon material with high temperature resistance and pressure resistance; the high-performance nylon mold is most easy to manufacture, has weight far lower than that of the former two molds, but has extremely high material cost and low tolerance temperature of only 175 ℃ and the tolerance pressure of only 0.45MPa, and is suitable for forming and curing some thermosetting composite materials with low modulus.

Therefore, the corresponding mold is prepared according to the requirement.

The model of the lower die unit cell is obtained in the following way, and the specific obtaining process is as follows:

step 1: determining the unit cell size of a pre-prepared pyramid lattice sandwich structure, such as a pyramid lattice core unit cell shown in FIG. 13;

step 2: in order to design a limiting groove on the lower mold unit cell to facilitate laying of prepreg, filling a space below the pyramid dot matrix core unit cell to obtain a first model, so that the pyramid dot matrix core unit cell becomes a convex part, as shown in the following fig. 14;

and 3, step 3: removing the model I obtained in the step 2 from a cube with the same bottom surface by adopting Boolean operation to obtain a model II containing a groove with the same shape as the pyramid lattice core unit cell structure, as shown in FIG. 15;

and 4, step 4: because the core bar of the single cell of the pyramid lattice core is respectively parallel to the x axis and the z axis, but the arrangement direction of the single cell is not along the core bar, but is arranged in the direction of 45 degrees with the core bar, as shown in fig. 16, in order to ensure that no gap is generated after the single cell of the pyramid lattice core forms the pyramid lattice core, the bottom platform of the single cell of the original pyramid lattice core can generate an overlapping phenomenon when being combined with the adjacent single cell of the original pyramid lattice core, therefore, the bottom platform of the core bar of the single cell of the pyramid lattice core is designed to be a polygon taking an isosceles right triangle as a sharp angle;

and 5: according to the geometric relationship, the vertex of the isosceles right triangle is the middle point of the edge of the platform at the bottom of the original pyramid lattice core unit cell structure, in order to ensure that the limit grooves of the lower mold unit cell can be arranged and combined to form the pyramid lattice core, the middle points of the top edges of the four core bar grooves of the second model obtained in the step 3 are sequentially connected, the formed square is used as the bottom surface, other redundant parts are cut off, and the required third model is finally obtained, as shown in fig. 17;

and 6: arranging the model III in an array form to obtain a model IV, as shown in fig. 18, cutting off the concave parts at the four edges of the model because the overall structure of the model IV is concave and the deep concave grooves are inconvenient for laying prepreg, and using the convex parts as a lower die of the pyramid lattice core;

and 7: and performing Boolean operation on the lower die and a cube with the same bottom surface to obtain the upper die for buckling.

The preparation method of the pyramid lattice core comprises the following specific preparation processes (as shown in figure 11):

step 1: cleaning an upper die 1 and a lower die 2 by using acetone, and uniformly coating a release agent on the convex part of the upper die 1 and the limiting groove 2-1-1 part of the lower die 2, or uniformly sticking release paper on the convex part of the upper die 1 and the limiting groove 2-1-1 part of the lower die 2;

step 2: pre-laying carbon fiber prepreg along a limiting groove 2-1-1 of a lower die 2;

and step 3: buckling an upper die 1 on a lower die 2 paved with carbon fiber prepreg 3 and compacting, sealing the whole die in a vacuum bag for sealing and vacuumizing, checking whether the sealing bag leaks air, putting the sealing bag into an autoclave or directly putting the sealing bag into a hot press for curing and forming, setting the hot pressing temperature to be 130 ℃ and the pressure to be 0.3MPa, and keeping the temperature for 90 minutes;

The pyramid lattice core is prepared by adopting the mold in the invention, the process is convenient, and the material utilization rate is high.

In the embodiment, the type of the carbon fiber prepreg is T300 prepreg and long fiber prepreg, and the preparation process is continuous, so that the prepared pyramid lattice core is good in quality, high in rigidity, strong in bearing capacity and high in strength.

In the embodiment, the carbon fiber prepreg is a strip-shaped prepreg tape 3-1, and the width of the prepreg tape 3-1 is the same as that of the limiting groove.

In the embodiment, in order to increase the load capacity of the pyramid lattice core, the carbon fiber prepreg is a latticed prepreg net 3-2, the grid of the prepreg net 3-2 is square, and the width of each prepreg tape on the prepreg net is the same as that of the limiting groove; the structure of the pyramid lattice core obtained by the latticed pre-dipping net is an integrated component, has no internal stress, good use effect and strong bearing capacity.

Claims

1. A mould for preparing pyramid lattice cores is characterized in that: comprises an upper die (1) and a lower die (2);

the upper die (1) is integrally formed by arranging a plurality of upper die unit cells (1-1) in an array form, the upper surface of each upper die unit cell (1-1) is inwards sunken to form a groove, a bulge is arranged in each groove of each upper die unit cell (1-1), and the shape of each bulge is the same as that of a prefabricated inverted pyramid lattice unit cell structure;

the lower die (2) is integrally formed by arranging a plurality of lower die unit cells (2-1) in an array form, the upper surface of each lower die unit cell (2-1) is protruded outwards to form a boss, a limiting groove (2-1-1) is formed in the boss of each lower die unit cell (2-1), and the structural shape of each limiting groove (2-1-1) is the same as that of a pre-prepared pyramid lattice unit cell;

an upper die unit cell (1-1) in the upper die (1) is matched with a lower die unit cell (2-1) in the lower die (2); the upper die (1) and the lower die (2) are made of silicon rubber;

the cross section of the lower die unit cell (2-1) is square; the boss on the lower die unit cell (2-1) comprises an upper plane (2-1-3) and four same slope surfaces (2-1-2), a cross flower-shaped groove (2-1-1-2) is formed in the upper plane (2-1-3), a convex edge is formed between every two adjacent slope surfaces, a core rod groove (2-1-1-1) is formed in each slope surface, the top ends of the four core rod grooves (2-1-1-1) are respectively connected with one branch groove of the cross flower-shaped groove (2-1-1-2), and the four core rod grooves (2-1-1-1) and the cross flower-shaped groove (2-1-1-2) jointly form a limiting groove (2-1-1).

2. The mold for manufacturing the pyramid lattice core according to claim 1, wherein: the bottom end of the core bar groove (2-1-1-1) is a polygonal groove body taking an isosceles right triangle as a sharp angle, a groove is formed among four lower mold unit cells (2-1) which are circumferentially arranged, and the polygonal groove bodies taking the isosceles right triangle as the sharp angle are arranged at the bottom ends of the four core bar grooves (2-1-1-1) in the groove to form a cross flower-shaped groove body.

3. A method for preparing a pyramid lattice core by using the mold of claim 2, wherein: the preparation process comprises the following steps:

step 1: cleaning an upper die (1) and a lower die (2) by using acetone, and uniformly coating a release agent on the convex part of the upper die (1) and the limiting groove (2-1-1) of the lower die (2), or uniformly sticking release paper on the convex part of the upper die (1) and the limiting groove (2-1-1) of the lower die (2);

step 2: pre-laying carbon fiber prepreg along a limiting groove (2-1-1) of a lower die (2);

and 3, step 3: buckling an upper die (1) on a lower die (2) paved with carbon fiber prepreg (3) and compacting, sealing the whole die in a vacuum bag for sealing and vacuumizing, checking whether the sealing bag leaks air, putting the sealing bag in an autoclave for curing and forming if the sealing bag is intact, setting the hot-pressing temperature to be 130 ℃, setting the pressure to be 0.3MPa, and keeping the temperature for 90 minutes;

and 4, step 4: and taking out the cured pyramid lattice core from the autoclave, and removing the upper die and the lower die after the temperature is reduced to normal temperature to obtain the fiber reinforced composite pyramid lattice core.

4. The method of claim 3, wherein the pyramidal dot matrix core is prepared by: the type of the carbon fiber prepreg is T300 prepreg.

5. The method of claim 4, wherein: the carbon fiber prepreg is a slender strip-shaped prepreg tape (3-1).

6. The method of claim 5, wherein: the carbon fiber prepreg is a latticed prepreg net (3-2), and the grid of the prepreg net (3-2) is square.