CN112677362B - Preforming body for forming grid reinforced foam sandwich composite material and forming method thereof - Google Patents
Preforming body for forming grid reinforced foam sandwich composite material and forming method thereof Download PDFInfo
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- CN112677362B CN112677362B CN202011309934.5A CN202011309934A CN112677362B CN 112677362 B CN112677362 B CN 112677362B CN 202011309934 A CN202011309934 A CN 202011309934A CN 112677362 B CN112677362 B CN 112677362B
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Abstract
A pre-forming body for forming grid reinforced foam sandwich composite material and a forming method thereof. The preformed body can conveniently and quickly complete the staggered alternate and alternate compounding of the discrete foam core material and the dry fiber fabric, and can ensure the dimensional accuracy, the overall stability and the quality consistency of the finished composite material. The forming process is simple in method, convenient to operate and low in cost, and can realize integral forming of the large-size grid reinforced foam sandwich composite material with the size not less than 1m x 1m, the novel composite material sandwich structure can partially replace the existing composite material sandwich structure, and can be widely applied to the fields of rail transit, high-speed trains, aerospace, ships, ocean engineering and the like.
Description
Technical Field
The invention relates to the technical field of sandwich structure composite materials, in particular to a preformed body for forming a grid reinforced foam sandwich composite material and a forming method thereof.
Background
The traditional foam sandwich composite material is formed by compounding upper and lower composite material panels with higher strength and modulus and a low-density foam sandwich material between the upper and lower panels, and has higher specific strength and specific rigidity; meanwhile, the low-density foam sandwich material has the functions of fire prevention, heat insulation, sound insulation, energy absorption and the like. Therefore, the traditional foam sandwich composite material becomes a typical structure and function integrated material and is widely applied to the fields of rail transit, high-speed trains, aerospace, ships, ocean engineering and the like. However, with the ever-increasing requirements of engineering applications on structural properties, the traditional foam sandwich composite materials have been unable to meet the requirements. Thus, attempts have been made in the prior art to incorporate composite grid structures into the foam core material of conventional foam core composites to construct a new sandwich structure composite, grid reinforced foam core composite. The main part of the material is the traditional foam sandwich composite material, and the reinforced part is a composite material grid structure. The grid reinforced foam sandwich composite material integrates the advantages of the traditional foam sandwich composite material and the grid structure of the composite material, not only retains the advantages of the traditional foam sandwich composite material such as lower density, higher strength and higher modulus, but also exerts the excellent mechanical property of the grid structure of the composite material. Namely: on the premise that the integral density is slightly increased, the mechanical properties of the grid reinforced foam sandwich composite material such as flat pressure, side pressure, bending, shearing and the like are obviously improved, and particularly the side pressure property is increased by times.
In such grid reinforced foam sandwich composites, the foam core sheet, originally as a unitary body, is divided into individual discrete foam core strips due to the introduction of the grid structure. When the interlayer preforming body is prepared, dry fiber fabrics (which are a composite material grid structure after resin infiltration molding) and foam core strips are alternately laid, the dry fiber fabrics are inserted among the discrete foam core strips in a wavy manner, and the foam core strips are 'semi-coated' by the dry fiber fabrics. In order to maximize the degree of fit between adjacent foam core strips and between the foam core strips and the dry fibrous web and minimize localized wrinkling of the dry fibrous web, a tension is applied to the dry fibrous web. But because the density of the foam core material is lower (less than or equal to 400 kg/m)3) The wavy dry-state fiber fabric with certain tension can cause the foam core material strip tightly attached to the wavy dry-state fiber fabric to be broken out. In addition, even if the foam core material strips and the dry fiber fabric are alternately laid according to the operation, after the tension applied to the dry fiber fabric is released, the preformed body which is originally well attached can be loosened again, so that the prepared laminated preformed body is irregular in arrangement, uneven in overall thickness, uneven in thickness of the grid structure and the like, and the appearance size and quality consistency of the grid reinforced foam sandwich composite material are influenced.
The grid reinforced foam sandwich composite material is a novel composite material sandwich structure, and no open and complete preparation mold and forming process solution is available at present. From public reports, the foreign University of Kingston (Kingston University), iranbare attoder morale University (tarbian models University) and the like successfully prepare foam sandwich composite materials with reinforced grid structures in different shapes by adopting a VARTM (vacuum assisted resin transfer molding) molding process, but the explanation of the molding process in the public reports is extremely simple, and the technical details of mold design, process schemes and the like are not disclosed; furthermore, composite materials based on VARTM molding processes, especially large-size composite structures, are relatively expensive to manufacture and are not suitable for industrial applications.
The grid reinforced foam sandwich composite material has the structural characteristics that foam core materials are completely discrete and dry fiber fabrics are inserted in the grid reinforced foam sandwich composite material in an antisymmetric manner, so that the biggest difficulty in the forming process is the size accuracy and the integral stability control of a sandwich preformed body and the integral preparation of the sandwich preformed body, and the key for solving the difficulty lies in the accuracy control of the position of the foam core materials, the thickness of a grid structure and the shape.
Therefore, it is actually necessary for practical production to design and manufacture a flat auxiliary mold with convenient operation and low molding difficulty, and design a molding process with relatively low cost to prepare large-size grid reinforced foam sandwich composite material.
Disclosure of Invention
In order to solve the technical problems, the invention provides a preformed body for forming a grid reinforced foam sandwich composite material and a forming method thereof. The preformed body can conveniently and quickly complete the staggered alternate and alternate compounding of the discrete foam core material and the dry fiber fabric, and can ensure the dimensional accuracy, the overall stability and the quality consistency of the finished composite material. The forming process has the advantages of simple method, convenient operation and lower cost, and is particularly suitable for preparing the large-size grid reinforced foam sandwich composite material.
The technical scheme adopted by the invention for solving the technical problems is as follows: the preformed body for forming the grid reinforced foam sandwich composite material comprises a rectangular flat metal base plate which is horizontally arranged, a plurality of limit groups are arranged on the upper surface of the rectangular flat-plate-shaped metal base plate at intervals in the left-right direction and in parallel along the length direction of the rectangular flat-plate-shaped metal base plate, each limit group consists of two positioning blocks which are symmetrically arranged in the left-right direction along the width direction of the rectangular flat-plate-shaped metal base plate, the positioning blocks are vertically arranged in a flat structure, the bottom of each positioning block is provided with a clamping seat in a downward extending manner, the clamping seat can be matched with a clamping groove preset on the metal bottom plate, a vertical through hole is also formed in the center of the top of each positioning block, a locking bolt penetrates through the vertical through hole, the locking bolt is a countersunk bolt, and the locking bolt sequentially penetrates through the positioning block and the clamping seat and then is screwed in the clamping groove of the metal bottom plate, so that the positioning block is clamped, locked and fixed on the upper surface of the metal bottom plate;
a silica gel gasket is laid in a gap between every two adjacent positioning blocks in the length direction of the rectangular flat-plate-shaped metal base plate, the silica gel gasket and the positioning blocks are consistent in width, so that the upper surface of the metal base plate is respectively assembled on the left side and the right side of the length direction of the metal base plate to form a fence-shaped structure which is formed by the positioning blocks and the silica gel gasket in a spaced distribution mode and has a fixed width, a lower panel with the thickness consistent with that of the silica gel gasket is laid at a position, located between the two fence-shaped structures, on the metal base plate, and a foam sandwich structure and a grid structure which are arranged in a staggered mode are arranged above the lower panel;
the foam sandwich structure comprises a foam core material group I and a foam core material group II which are arranged at intervals in an inserting manner, the foam core material group I and the foam core material group II are composed of a plurality of foam core material strips which are arranged in parallel at the left and right, the plurality of foam core material strips have the same height, the number of the foam core material strips in the foam core material group I is consistent with the number of limit groups, the plurality of foam core material strips in the foam core material group I are respectively clamped between two positioning blocks in each limit group, the upper surfaces of the foam core material strips in the foam core material group I and the upper surfaces of the positioning blocks are positioned on the same horizontal plane, the number of the foam core material strips in the foam core material group II is half of the number of silica gel gaskets, the plurality of foam core material strips in the foam core material group II are respectively arranged between every two adjacent limit groups, and the two ends of the foam core material strips in the foam core material group II respectively extend to cover the upper parts of the corresponding silica gel gaskets, the grid structure be the dry state fabric of treating the shaping, this dry state fabric is unsmooth undulation form antisymmetric structure, and its top of hugging closely foam core group I, the bottom of foam core group II and the clearance between every two adjacent foam core strips in the two paves, the foam sandwich structure of crisscross arrangement and grid structure group have constituted the horizontal platform form structure of an upper surface jointly, and the upper portion of this platform form structure has still laid the top panel.
Furthermore, the clamping groove and the clamping seat are of rectangular structures.
Furthermore, the clamping seat and the corresponding positioning block are of an integral structure.
Furthermore, the positioning block is made of metal.
Furthermore, the longitudinal section of the positioning block is any one of a rectangle, a triangle or an isosceles trapezoid.
Furthermore, the upper panel and the lower panel are consistent in thickness and material.
Further, the upper panel and the lower panel are mixed fabrics of at least one of glass fiber, carbon/glass hybrid fiber, quartz fiber, Kevler fiber, ultra-high molecular weight polyethylene fiber and PB0 fiber, and the surface density of the mixed fabrics is not less than 100g/m2。
Further, the dry fiber fabric is a mixed fabric of at least one of glass fiber, carbon/glass hybrid fiber, quartz fiber, Kevler fiber, ultra-high molecular weight polyethylene fiber and PB0 fiber, and the surface density of the mixed fabric is more than or equal to 100g/m2。
Furthermore, the material of the foam core material strip is any one of polyvinyl chloride, polymethacrylimide, polyethylene glycol terephthalate and polyurethane, and the density of the foam core material strip is less than or equal to 400kg/m3。
A method for forming a grid reinforced foam sandwich composite material comprises the following steps:
(1) preparation of Metal sole plates
The method comprises the following steps of (1) flatly placing a metal bottom plate on a horizontal operation table, cleaning the upper surface of the metal bottom plate and a clamping groove by using alcohol or acetone, cleaning and airing, uniformly coating demolding wax on the upper surface of the metal bottom plate and the clamping groove for 3 times, and enabling the demolding wax to be separated for 10-20min each time;
(2) cleaning and mounting of positioning blocks
Cleaning the outer surfaces of the positioning block and the clamping seat by using alcohol or acetone, cleaning and drying, uniformly coating demolding wax on the outer surfaces of the positioning block and the clamping seat for 3 times at intervals of 10-20min, inserting the clamping seat of the positioning block into the clamping groove on the metal bottom plate in the step (1), locking and fixing the positioning block in the clamping groove of the metal bottom plate by using a locking bolt through a preset vertical through hole on the positioning block, and ensuring that the positioning block cannot shake;
(3) placement of silica gel gasket
A silica gel gasket is adopted to fully cover the gap between every two adjacent positioning blocks between the limiting groups;
(4) laying of lower panel
Paving a lower panel with the thickness consistent with that of the silica gel gasket selected in the step (3) in an area surrounded by the positioning block and the silica gel gasket on the upper surface of the metal bottom plate;
(5) laying of foam core strips in foam core group I
A plurality of foam core material strips are sequentially laid between two positioning blocks in each limiting group from left to right, so that the foam core material strips form a foam core material group I, and the longitudinal section of each foam core material strip in the foam core material group I is consistent with that of each positioning block;
(6) laying of dry fibre fabrics
Paving dry fiber fabrics on the upper surface of the foam core material group I;
(7) laying of foam core strips in foam core group II
Laying a plurality of foam core strips on the upper surface of the dry fiber fabric at left and right intervals, enabling the foam core strip groups to form a foam core group II, respectively prepressing the foam core strips in the foam core group II downwards to extrude the foam core strips into a gap between every two adjacent limit groups, and then placing strip-shaped weights for compaction and fixation on the upper surface of a platform-shaped structure formed by the dry fiber fabric and the foam core group II;
(8) laying of upper panel
Removing the strip-shaped heavy object in the step (7), and paving an upper panel on the upper surface of the platform-shaped structure to form a preformed body;
(9) encapsulation of preforms
According to a VARI forming process, laying demolding cloth and a flow guide net and arranging a glue injection pipeline on the preformed body prepared in the step (8), and then integrally packaging the preformed body by using a vacuum bag film;
(10) glue injection and demolding
And (4) injecting glue into the preformed body packaged in the step (9) according to a VARI molding process, disassembling a positioning block in the preformed body after the resin is completely cured, and demolding to obtain the finished grid reinforced foam sandwich composite material.
Has the advantages that:
1. the preformed body for forming the grid reinforced foam sandwich composite material can accurately control the position of the foam core material and the thickness of the grid structure by setting the limiting group in the device, and effectively realizes the accurate control of the size of the preformed body, the control of the overall thickness, the overall stability and the quality consistency of a formed product in the forming process of the grid reinforced foam sandwich composite material. Simultaneously, use combined material's upper and lower panel thickness as the benchmark, through the cooperation setting of draw-in groove on locating piece bottom cassette and the metal soleplate, both promoted the loading and unloading convenience of whole preforming body, can control the uniformity of panel and top panel thickness down betterly again, the practical function is better.
2. After the preparation of the composite material is completed, the related mold units (including the metal bottom plate, the positioning block and the like) can be repeatedly used after being disassembled and demoulded. And the whole manufacturing cost of the die unit is lower, the die unit is easy to demould, disassemble and assemble, the utilization rate is high, the maintenance is easy, and the practical effect is good.
3. The preformed body can accurately regulate and control the shape of the grid structure through the design of the shape of the positioning block and the space between the adjacent positioning blocks, and complete the accurate control of the thickness of the grid structure so as to realize the preparation of different types of grid reinforced foam sandwich composite materials.
4. After the preparation of the whole preformed body is finished, the forming process can lay the demolding cloth, the flow guide net, the glue injection port, the glue outlet, the glue injection pipeline and the like according to the conventional steps of the VARI forming process, and then the integral packaging can be realized, so that the integral forming of the upper panel and the lower panel, the foam sandwich structure and the grid structure can be realized, the preparation of the whole composite product can be finished in one-step forming operation, the preparation efficiency is higher, the preparation cost is low, and the appearance consistency and the quality stability of a finished product can be well ensured. The forming process has the advantages of stable technology, simple flow, convenient operation and convenient implementation.
Drawings
FIG. 1 is a schematic view of a longitudinal cut-away structure of a preform (including a positioning block) in the present invention;
FIG. 2 is a schematic diagram of a longitudinally cut-away structure of a preform (not including a positioning block) in the present invention;
FIG. 3 is a schematic view of a cross-sectional configuration of a preform in the present invention;
FIG. 4 is a front view of a positioning block and a clamping base of the present invention;
FIG. 5 is a top view of FIG. 4;
FIG. 6 is a bottom view of FIG. 4;
FIG. 7 is a schematic structural view of a flat plate type auxiliary mold used in example 1;
FIG. 8 is a top view of FIG. 7;
FIG. 9 is a schematic structural view of a flat plate type auxiliary mold used in example 2;
FIG. 10 is a top view of FIG. 9;
reference numerals: 1. the novel dry-state fiber fabric comprises a metal bottom plate, 2 parts of a positioning block, 201 parts of a vertical through hole, 202 parts of a clamping seat, 3 parts of a locking bolt, 4 parts of a silica gel gasket, 5 parts of an upper panel, 6 parts of a lower panel, 7 parts of a foam core material strip, and 8 parts of a dry-state fiber fabric.
Detailed Description
The technical solution of the present invention will be further explained and explained in detail with reference to the drawings and the specific embodiments.
As shown in the figure, the method for molding the grid reinforced foam sandwich composite material based on the VARI molding process and the flat plate type mold comprises the design of the flat plate type auxiliary mold, the preparation of a preformed body and the integrated integral molding method of the grid reinforced foam sandwich composite material based on the VARI molding process.
The main components of the flat plate type auxiliary die comprise a metal base plate 1, positioning blocks 2, locking bolts 3 and a silica gel gasket 4, wherein the metal base plate 1 is in a rectangular flat plate shape and is horizontally arranged, a plurality of limiting groups are arranged on the upper surface of the rectangular flat plate type metal base plate 1 at intervals along the length direction of the metal base plate, each limiting group is composed of two positioning blocks 2 symmetrically arranged along the width direction of the rectangular flat plate type metal base plate 1, a plurality of rectangular blind hole-shaped clamping grooves are processed on the upper surface of the metal base plate 1, the positioning blocks 2 are in a vertically arranged flat plate-shaped structure, circular vertical through holes 201 are processed on the positioning blocks 2 in the height direction of the positioning blocks, the locking bolts 3 are inserted in the vertical through holes 201, the locking bolts 3 are countersunk head bolts, and rectangular clamping seats 202 matched with the clamping grooves on the upper surface of the metal base plate 1 in size are processed on the bottom surface of the positioning blocks 2, the positioning block 2 integrates positioning and limiting functions. The locking bolt 3 sequentially penetrates through the positioning block 2 and the clamping seat 202 and then is screwed in the clamping groove of the metal base plate 1, so that the positioning block 2 is clamped, locked and fixed on the upper surface of the metal base plate 3; the silica gel gasket 4 is laid in the gap between every two adjacent positioning blocks 2, the widths of the silica gel gasket 4 and the positioning blocks 2 are consistent, so that the upper surface of the metal bottom plate 1 is respectively assembled at the left side and the right side along the length direction of the metal bottom plate to form a fence-shaped structure which is formed by the positioning blocks 2 and the silica gel gasket 4 in a spaced distribution mode and has a fixed width.
The preparation of the preformed body depends on a flat auxiliary die and comprises the steps of paving an upper panel 5 and a lower panel 6, paving a foam core material strip 7, paving a dry fiber fabric 8 (namely a composite material grid structure after resin infiltration molding) and the like. Wherein, the thickness of the lower panel 6 is consistent with the thickness of the silica gel gasket 4, the lower panel is paved on the metal bottom plate 1 and positioned between the two fence-shaped structures, and foam core material strips 7 and dry fiber fabrics 8 which are arranged in a staggered way are arranged above the lower panel 6.
The forming method of the grid reinforced foam sandwich composite material comprises the following steps:
(1) preparation of Metal soleplate 1
Horizontally placing the metal bottom plate 1 on a horizontal operation table, cleaning the upper surface and the clamping grooves of the metal bottom plate 1 by using alcohol or acetone, cleaning and drying, and uniformly coating demolding wax on the upper surface and the clamping grooves of the metal bottom plate 1 for 3 times at an interval of 10-20 min;
(2) cleaning and mounting of positioning block 2
Cleaning the outer surfaces of the positioning block 2 and the clamping seat 202 by using alcohol or acetone, cleaning and drying, uniformly coating stripping wax on the outer surfaces of the positioning block 2 and the clamping seat 202 for 3 times at an interval of 10-20min, slowly inserting the clamping seat 202 of the positioning block 2 into the clamping groove on the metal bottom plate 1 in the step (1) to ensure that the clamping seat 202 is well engaged with the clamping groove, locking and fixing the positioning block 2 in the clamping groove of the metal bottom plate 1 by using a locking bolt 3 through a preset vertical through hole 201 on the positioning block 2, and not twisting during operation, wherein the positioning block 2 does not shake;
(3) placement of silica gel gasket
A silica gel gasket 3 is adopted to fully cover the gap between every two adjacent positioning blocks between the limiting groups; the length of silica gel gasket 4 is for controlling interval between two adjacent locating pieces 2, and the width is the same with locating piece 2 width, and silica gel gasket 4 places between two adjacent locating pieces 2, and all need place silica gel gasket 4 between two adjacent locating pieces 2.
(4) Laying of lower panel
Determining the number of layers, laying modes and the like of the fiber fabrics to be laid according to the target thickness of the lower panel 6 and the type of the selected reinforced fiber fabrics, and laying the lower panel 6 with the thickness consistent with the thickness of the silica gel gasket 3 selected in the step (3) in the area surrounded by the positioning block 2 and the silica gel gasket 3 on the upper surface of the metal bottom plate 1;
(5) laying of foam core strips in foam core group I
A plurality of foam core strips 7 are sequentially laid between the two positioning blocks 2 in each limiting group from left to right, and are laid at intervals from one side to the other side during laying, so that the foam core strips 7 form a foam core group I, and the longitudinal section of each foam core strip 7 in the foam core group I is consistent with that of each positioning block 2; the two ends of the foam core material strip 7 are aligned with the pair of positioning blocks 2 in each limiting group, so that the foam core material strip 7 is clamped between the limiting groups;
(6) laying of dry fibre fabric
Spreading dry fiber fabric 8 (which is a composite material grid structure after resin infiltration molding) on the upper surface of the foam core material group I horizontally;
(7) laying of foam core strips in foam core group II
A plurality of foam core material strips 7 are laid on the upper surface of a dry-state fiber fabric 8 at left and right intervals, so that the foam core material strips 7 form a foam core material group II, then, each foam core material strip 7 in the foam core material group II is respectively pre-pressed downwards to be extruded into a gap between every two adjacent limit groups, and then, a strip-shaped heavy object for compaction and fixation is placed on the upper surface of a platform-shaped structure formed by the dry-state fiber fabric 8 and the foam core material group II in time;
(8) laying of upper panel
Removing the strip-shaped heavy object in the step (7), and paving an upper panel 5 on the upper surface of the platform-shaped structure, wherein the paving requirement is the same as that of a lower panel 6, so as to form a preformed body;
(9) encapsulation of preforms
According to a VARI forming process, laying demolding cloth and a flow guide net and arranging a glue injection pipeline on the preformed body prepared in the step (8), and then integrally packaging the preformed body by using a vacuum bag film;
(10) glue injection and demolding
And (3) injecting glue into the preformed body packaged in the step (9) according to a VARI (vacuum assist molding) forming process, after the resin is completely cured, detaching the positioning block 2 in the preformed body, and demolding to obtain the finished product of the grid reinforced foam sandwich composite material.
In the technical scheme, the metal base plate 1 is made of 45# steel and metals such as higher-grade steel, aluminum alloy, titanium alloy and the like, the planeness of the upper surface is less than or equal to 0.2mm, the size of the upper surface is at least 100mm larger than the target size of the grid reinforced foam sandwich composite material, the thickness is related to the modulus of the selected materials, and the out-of-plane deformation of the metal base plate 1 is less than or equal to 5mm and is generally not less than 15 mm. The metal bottom plate 1 is equivalent to the target size of the grid reinforced foam sandwich composite material, and the length is less than or equal to 5m and the width is less than or equal to 5 m.
The number of the positioning blocks 2 is required to be 2N (N is more than or equal to 2 and less than or equal to 100, N is an integer), the length range is 10mm-100mm, the width range is 8mm-50mm, the height range is 10mm-70mm, and the distance between every two adjacent positioning blocks 2 is +/-1 mm of the length of the positioning block 2; in addition, all the positioning blocks 2 are completely the same in appearance size and material, the material is 45# steel and metals such as higher grade steel, aluminum alloy, titanium alloy and the like, and the machining tolerance is +/-0.1 mm. The position of a vertical through hole 201, used for the through connection of the locking bolt 3, of the positioning block 2 is the geometric center of the positioning block 2 in the height direction, the diameter of the vertical through hole 201 is one fourth to one half of the width of the positioning block 2, the machining tolerance is +/-0.1 mm, the machining tolerance with a clamping groove of the metal base plate 1 is +/-0.1 mm, and the size of the clamping groove of the metal base plate 1 is 0.1-0.2mm larger than that of a clamping seat 202 of the positioning block 2. The geometric shape of the longitudinal section of the positioning block 2 can be determined according to the structural design requirement of the composite material, and simple geometric shapes such as rectangle, trapezoid, triangle and the like can be selected, and other shapes can also be selected.
The lockbolt 3 is a standard part or a non-standard part, has the specification of M6-M12, is made of high-strength metals such as 40# chromium steel, 42# chromium manganese steel, 12.9-grade high-strength steel, titanium alloy and the like, and can also be made of low-strength steel such as 45# steel and the like, but needs to be annealed.
The length of the silica gel gasket 4 is +/-1 mm of the length of the positioning block 2, the width of the silica gel gasket is +/-1 mm of the width of the positioning block 2, and the thickness of the silica gel gasket ranges from 1mm to 8 mm.
The upper panel 5 and the lower panel 6 are made of fiber fabrics such as glass fiber, carbon/glass hybrid fiber, quartz fiber, Kevler fiber, ultra-high molecular weight polyethylene fiber, PB0 fiber and the like and mixed fabrics thereof, and the surface density is not less than 100g/m2。
The dry fiber fabric 8 for the grating is a fiber fabric such as glass fiber, carbon/glass hybrid fiber, quartz fiber, Kevler fiber, ultra-high molecular weight polyethylene fiber, PB0 fiber and the likeThe surface density of the fabric and the mixed fabric thereof is more than or equal to 100g/m2。
The dry fiber fabric 8 for the grid (which is a composite grid structure after being soaked and molded by resin) can be the same as or different from the fiber fabric for the upper panel 5 and the lower panel 6.
The foam core material strip 7 is made of foaming materials such as polyvinyl chloride (PVC), Polymethacrylimide (PMI), polyethylene terephthalate (PET), Polyurethane (PU) and the like, and has the density of less than or equal to 400kg/m3The geometric shape of the longitudinal section is the same as that of the positioning block 2, can be determined according to the structural design requirements of the composite material, and can be rectangular, trapezoidal, triangular and other simple geometric shapes, and other shapes can also be selected.
Example 1:
with reference to fig. 7 and 8, the positioning block of the grid reinforced foam sandwich composite material of the present embodiment has a rectangular longitudinal section. The number of the positioning blocks with rectangular longitudinal sections is 12 to 24, the length is 40mm, the width is 15mm, the height is 28.5mm, the adjacent distance of the positioning blocks is 40.8mm, the length of the silica gel gasket is 40.8mm, the width is 15mm, the thickness is 3.5mm, the type of the locking bolt is M8, and the length of the metal bottom plate is 1150mm, the width is 1150mm, and the thickness is 20 mm.
The length of the upper panel and the lower panel is 929mm, the width is 920mm, the thickness is 3.5mm, the width of the dry fiber fabric in the grid structure is 950mm, the thickness is 0.4mm, the number of the foam core material strips with rectangular longitudinal sections is 23, the length is 950mm (11) and 920mm (12), the width is 40mm, and the height is 25 mm.
The metal bottom plate and the positioning block are both made of 6061 aluminum alloy, and the locking bolt is made of 12.9-grade high-strength steel.
The surface density of the fiber fabric for the upper panel and the lower panel is 400g/m2The E glass fiber checked cloth has 10 layers; the dry fiber fabric for the grid (the composite grid structure is obtained after resin infiltration molding) has the surface density of 220g/m2The satin high-strength glass fiber cloth has 2 layers.
The molding process is the same as the above steps.
Example 2:
with reference to fig. 9 and 10, the positioning blocks of the grid reinforced foam sandwich composite material of the present embodiment have isosceles trapezoid longitudinal sections. The number of the positioning blocks with isosceles trapezoid longitudinal sections is 15 to 30, the upper bottom is 20mm, the lower bottom is 66.2mm, the width is 20mm, and the height is 42.6mm, the adjacent distance of the positioning blocks is 20.42, the length of the silica gel gasket is 20.42mm, the width is 20mm, the thickness is 2.6mm, the type of the locking bolt is M10, and the length of the metal base plate is 1500mm, the width is 1300mm, and the thickness is 25 mm.
The length of the upper panel is 1233mm, the length of the lower panel is 1279mm, the widths of the upper panel and the lower panel are 1030mm, the thicknesses of the upper panel and the lower panel are 2.6mm, the width of the grid structure is 1070mm, the thickness of the grid structure is 0.21mm, the number of the foam core material strips with isosceles trapezoid longitudinal sections is 29, the lengths of the foam core material strips are 1070mm (14) and 1030mm (15), and the upper bottom of the foam core material strip is 20mm, the lower bottom of the foam core material strip is 66.2mm, and the height of the foam core material strip is 40 mm.
The metal bottom plate and the positioning block are both made of No. 45 steel, and the locking bolt is made of No. 42 chromium manganese steel.
The surface density of the fiber fabric for the upper panel and the lower panel is 350g/m2The number of the biaxial high-strength glass fiber cloth is 8; the dry fiber fabric for the grid (the composite grid structure is obtained after resin infiltration molding) has the surface density of 200g/m2The number of the unidirectional carbon fiber cloth is 1 layer.
The molding process is the same as the above steps.
The particular embodiments disclosed above are illustrative only, as various modifications and changes may be made by those skilled in the art without departing from the scope of the invention.
Claims (10)
1. The preformed body for forming the grid reinforced foam sandwich composite material comprises a rectangular flat-plate-shaped metal base plate which is horizontally arranged, and is characterized in that: the upper surface of the rectangular flat-plate-shaped metal base plate is provided with a plurality of limiting groups at intervals in the left-right direction and in parallel along the length direction, each limiting group consists of two positioning blocks which are arranged symmetrically in the left-right direction along the width direction of the rectangular flat-plate-shaped metal base plate, each positioning block is of a vertically arranged flat-plate-shaped structure, the bottom of each positioning block is provided with a clamping seat in a downward extending manner, the clamping seat can be matched with a clamping groove preset on the metal base plate, a vertical through hole is further formed in the center of the top of each positioning block, a locking bolt penetrates through the vertical through hole, is a countersunk bolt, and is screwed in the clamping groove of the metal base plate after sequentially penetrating through the positioning blocks and the clamping seats, so that the clamping, locking and fixing of the positioning blocks on the upper surface of the metal base plate are realized;
a silica gel gasket is laid in a gap between every two adjacent positioning blocks in the length direction of the rectangular flat-plate-shaped metal base plate, the silica gel gasket and the positioning blocks are consistent in width, so that the upper surface of the metal base plate is respectively assembled on the left side and the right side of the length direction of the metal base plate to form a fence-shaped structure which is formed by the positioning blocks and the silica gel gasket in a spaced distribution mode and has a fixed width, a lower panel with the thickness consistent with that of the silica gel gasket is laid at a position, located between the two fence-shaped structures, on the metal base plate, and a foam sandwich structure and a grid structure which are arranged in a staggered mode are arranged above the lower panel;
the foam sandwich structure comprises a foam core material group I and a foam core material group II which are arranged at intervals in an inserting manner, the foam core material group I and the foam core material group II are composed of a plurality of foam core material strips which are arranged in parallel at the left and right, the plurality of foam core material strips have the same height, the number of the foam core material strips in the foam core material group I is consistent with the number of limit groups, the plurality of foam core material strips in the foam core material group I are respectively clamped between two positioning blocks in each limit group, the upper surfaces of the foam core material strips in the foam core material group I and the upper surfaces of the positioning blocks are positioned on the same horizontal plane, the number of the foam core material strips in the foam core material group II is half of the number of silica gel gaskets, the plurality of foam core material strips in the foam core material group II are respectively arranged between every two adjacent limit groups, and the two ends of the foam core material strips in the foam core material group II respectively extend to cover the upper parts of the corresponding silica gel gaskets, the grid structure be the dry state fabric of treating the shaping, this dry state fabric is unsmooth undulation form antisymmetric structure, and its top of hugging closely foam core group I, the bottom of foam core group II and the clearance between every two adjacent foam core strips in the two paves, the foam sandwich structure of crisscross arrangement and grid structure group have constituted the horizontal platform form structure of an upper surface jointly, and the upper portion of this platform form structure has still laid the top panel.
2. The preform for molding the grid reinforced foam sandwich composite material according to claim 1, characterized in that: the clamping groove and the clamping seat are of rectangular structures.
3. The preform for molding the grid reinforced foam sandwich composite material according to claim 1, characterized in that: the clamping seat and the corresponding positioning block are of an integral structure.
4. The preform for molding the grid reinforced foam sandwich composite material according to claim 1, characterized in that: the positioning block is made of metal.
5. The preform for molding the grid reinforced foam sandwich composite material according to claim 1, characterized in that: the longitudinal section of the positioning block is any one of a rectangle, a triangle or an isosceles trapezoid.
6. The preform for molding the grid reinforced foam sandwich composite material according to claim 1, characterized in that: the upper panel and the lower panel are both consistent in thickness and material.
7. The method for forming a grid reinforced foam sandwich composite material according to claim 1, wherein the method comprises the following steps: the upper panel and the lower panel are mixed fabrics of at least one of glass fiber, carbon/glass hybrid fiber, quartz fiber, Kevler fiber, ultra-high molecular weight polyethylene fiber and PB0 fiber, and the surface density of the mixed fabrics is more than or equal to 100g/m2。
8. The preform for molding the grid reinforced foam sandwich composite material according to claim 1, characterized in that: the dry fiber fabric is glass fiber, carbon/glass hybrid fiber, quartz fiber, Kevler fiber, and ultra-high molecular weight polyethyleneAt least one of the olefin fiber and the PB0 fiber, and the area density of the mixed fabric is more than or equal to 100g/m2。
9. The preform for molding the grid-reinforced foam sandwich composite material according to claim 1, characterized in that: the material of the foam core material strip is any one of polyvinyl chloride, polymethacrylimide, polyethylene glycol terephthalate and polyurethane, and the density of the foam core material strip is less than or equal to 400kg/m3。
10. The method of claim 1, wherein the method comprises the steps of:
(1) preparation of Metal sole plates
Placing the metal bottom plate on a horizontal operation table, cleaning the upper surface of the metal bottom plate and the clamping grooves by using alcohol or acetone, cleaning and drying, and uniformly coating demolding wax on the upper surface of the metal bottom plate and the clamping grooves for 3 times at an interval of 10-20 min;
(2) cleaning and mounting of positioning blocks
Cleaning the outer surfaces of the positioning block and the clamping seat by using alcohol or acetone, after the cleaning and the drying, uniformly coating stripping wax on the outer surfaces of the positioning block and the clamping seat for 3 times at an interval of 10-20min each time, then inserting the clamping seat of the positioning block into the clamping groove on the metal bottom plate in the step (1), locking and fixing the positioning block in the clamping groove of the metal bottom plate by using a locking bolt through a preset vertical through hole on the positioning block, and ensuring that the positioning block cannot shake;
(3) placement of silica gel gasket
A silica gel gasket is adopted to fully cover the gap between every two adjacent positioning blocks between the limiting groups;
(4) laying of lower panel
Paving a lower panel with the thickness consistent with that of the silica gel gasket selected in the step (3) in an area surrounded by the positioning block and the silica gel gasket on the upper surface of the metal bottom plate;
(5) laying of foam core strips in foam core group I
A plurality of foam core material strips are sequentially laid between two positioning blocks in each limiting group from left to right, so that the foam core material strip groups form a foam core material group I, and the longitudinal section of each foam core material strip in the foam core material group I is consistent with the longitudinal section of each positioning block;
(6) laying of dry fibre fabric
Paving dry fiber fabrics on the upper surface of the foam core material group I;
(7) laying of foam core strips in foam core group II
Laying a plurality of foam core strips on the upper surface of the dry fiber fabric at left and right intervals, enabling the foam core strip groups to form a foam core group II, respectively prepressing the foam core strips in the foam core group II downwards to extrude the foam core strips into a gap between every two adjacent limit groups, and then placing strip-shaped weights for compaction and fixation on the upper surface of a platform-shaped structure formed by the dry fiber fabric and the foam core group II;
(8) laying of upper panel
Removing the strip-shaped heavy object in the step (7), and paving an upper panel on the upper surface of the platform-shaped structure to form a preformed body;
(9) encapsulation of preforms
According to a VARI forming process, laying demolding cloth and a flow guide net and arranging a glue injection pipeline on the preformed body prepared in the step (8), and then integrally packaging the preformed body by using a vacuum bag film;
(10) glue injection and demolding
And (3) injecting glue into the preformed body packaged in the step (9) according to a VARI (vacuum assist molding) forming process, after the resin is completely cured, detaching a positioning block in the preformed body, and demolding to obtain the finished product of the grid reinforced foam sandwich composite material.
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| CN114801258A (en) * | 2022-03-09 | 2022-07-29 | 中国船舶重工集团公司第七二五研究所 | Preparation method of bidirectional grid structure reinforced foam sandwich composite material |
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