CN113771388A - Forming method of special-shaped composite material reinforced grid rib and special-shaped skin cabin section thereof - Google Patents
Forming method of special-shaped composite material reinforced grid rib and special-shaped skin cabin section thereof Download PDFInfo
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- CN113771388A CN113771388A CN202111332390.9A CN202111332390A CN113771388A CN 113771388 A CN113771388 A CN 113771388A CN 202111332390 A CN202111332390 A CN 202111332390A CN 113771388 A CN113771388 A CN 113771388A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C70/00—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
- B29C70/04—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts comprising reinforcements only, e.g. self-reinforcing plastics
- B29C70/28—Shaping operations therefor
- B29C70/30—Shaping by lay-up, i.e. applying fibres, tape or broadsheet on a mould, former or core; Shaping by spray-up, i.e. spraying of fibres on a mould, former or core
- B29C70/34—Shaping by lay-up, i.e. applying fibres, tape or broadsheet on a mould, former or core; Shaping by spray-up, i.e. spraying of fibres on a mould, former or core and shaping or impregnating by compression, i.e. combined with compressing after the lay-up operation
- B29C70/342—Shaping by lay-up, i.e. applying fibres, tape or broadsheet on a mould, former or core; Shaping by spray-up, i.e. spraying of fibres on a mould, former or core and shaping or impregnating by compression, i.e. combined with compressing after the lay-up operation using isostatic pressure
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C33/00—Moulds or cores; Details thereof or accessories therefor
- B29C33/76—Cores
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C70/00—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
- B29C70/04—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts comprising reinforcements only, e.g. self-reinforcing plastics
- B29C70/28—Shaping operations therefor
- B29C70/30—Shaping by lay-up, i.e. applying fibres, tape or broadsheet on a mould, former or core; Shaping by spray-up, i.e. spraying of fibres on a mould, former or core
- B29C70/32—Shaping by lay-up, i.e. applying fibres, tape or broadsheet on a mould, former or core; Shaping by spray-up, i.e. spraying of fibres on a mould, former or core on a rotating mould, former or core
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C70/00—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
- B29C70/04—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts comprising reinforcements only, e.g. self-reinforcing plastics
- B29C70/28—Shaping operations therefor
- B29C70/30—Shaping by lay-up, i.e. applying fibres, tape or broadsheet on a mould, former or core; Shaping by spray-up, i.e. spraying of fibres on a mould, former or core
- B29C70/38—Automated lay-up, e.g. using robots, laying filaments according to predetermined patterns
- B29C70/382—Automated fiber placement [AFP]
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
- B29L2031/00—Other particular articles
- B29L2031/30—Vehicles, e.g. ships or aircraft, or body parts thereof
- B29L2031/3097—Cosmonautical vehicles; Rockets
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- Chemical & Material Sciences (AREA)
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- Casting Or Compression Moulding Of Plastics Or The Like (AREA)
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Abstract
The invention belongs to the technical field of composite material forming processes, and particularly relates to a forming method of special-shaped composite material reinforced grid ribs and a special-shaped skin cabin section thereof, wherein the forming method comprises the following steps: step 1: taking a core die and a split die of which the outer surface is provided with a circumferential rib groove and a longitudinal rib groove; step 2: paving carbon fiber fabric on the outer surface of the split mold; and step 3: taking one or more layers of ribs which are made of carbon fiber prepreg and have the same width as the rib grooves, performing annular and longitudinal staggered circulating layering on the split mold, and performing glue sucking and pre-compaction treatment once when the thickness of the layering is increased by a preset value; and 4, step 4: repeating the step 3 until the expected thickness is reached; paving a skin on the surface of the grid rib for curing treatment; and 5: and (4) removing the core mold and the split mold to obtain the special-shaped composite material reinforced grid rib. The method replaces metal materials with composite materials, not only exerts the characteristics of light weight, high strength and fatigue resistance of the composite materials, but also reduces the operation cost and improves the service cycle of products.
Description
Technical Field
The invention belongs to the technical field of composite material forming processes, and particularly relates to a forming method of special-shaped composite material reinforced grid ribs and a special-shaped skin cabin section thereof.
Background
With the vigorous development of the aviation industry in China, products with the characteristics of large size and special-shaped structure, such as carrier rocket fairings, strategic missile hoods, transition sections and cabin sections of various aircrafts and the like, meet the overall structural strength and achieve the purpose of light weight in order to further cope with the complex load working conditions of outer space, and the method is the main direction of development in the current stage of China. According to the load distribution condition under the working condition of the aircraft, the aircraft cabin section and the transition section made of metal materials are optimally designed into a grid rib structure which is lighter in weight and has better bearing advantages, but the processing complexity and the processing cost of the whole structure are correspondingly multiplied. The metal material has the characteristic of being sensitive to internal defects and processing defects of the material, and if various tiny defects appearing in the production and preparation processes are not found in time, the overall structure is easily damaged in a catastrophic way; the material also forces people to favor the advanced resin matrix composite material with the characteristics of light weight, high strength, corrosion resistance and easy forming.
Chinese patent CN108162430A discloses a method for forming a special-shaped composite material grid skin cabin section, and specifically discloses the following steps: manufacturing a special-shaped composite material grid carbon fiber prepreg cabin section forming die; step two, paving carbon cloth prepreg in the annular rib deep groove area; winding carbon fiber prepreg filaments, and filling the annular rib deep groove area; winding carbon fiber prepreg filaments and laying carbon fiber prepreg; step five, vacuumizing and sucking glue for the first time; step six, laying carbon fiber prepreg, and performing secondary vacuum pumping and glue suction treatment; winding carbon fiber prepreg filaments, and vacuumizing and curing the carbon fiber prepreg paving layer; and (eighthly), removing the die to obtain the special-shaped grid carbon fiber prepreg cabin section.
However, the above method has the following problems: 1) the preparation process mainly comprises winding forming, the winding forming method has certain advantages for controlling the winding tension and further for products with positive curvature on the outer side surface of the structure, and the whole cabin section structure comprises 40-50% of negative curvature area, so that the process cannot control the product quality. 2) The adopted vacuumizing glue sucking process cannot form an effective compaction effect on the composite material in the rib groove, and further loses effective control on the forming quality of the grid ribs.
Therefore, in order to overcome the defects, the invention urgently needs to provide a forming method of the special-shaped composite material reinforced grid rib and a special-shaped skin cabin section thereof.
Disclosure of Invention
The invention aims to provide a forming method of a special-shaped composite material reinforced grid rib and a special-shaped skin cabin section thereof, and aims to solve the problem that the processing method in the prior art cannot ensure the stable quality of the composite material reinforced grid rib.
The invention provides a molding method of a special-shaped composite material reinforced grid rib, which comprises the following steps: step 1: taking a forming die of the special-shaped composite material reinforced grid rib, wherein the forming die comprises a core die and a split die; the split mold is fixed on the outer side of the core mold, the outer surface of the split mold is provided with an annular rib groove along the horizontal direction, and a longitudinal rib groove is arranged along the vertical direction; step 2: taking a block-shaped carbon fiber fabric, paving the block-shaped carbon fiber fabric on the outer surface of the split mold in a shape, and turning the upper side and the lower side of the carbon fiber fabric to the outer side of the thinning mold; and step 3: taking one or more layers of ribs which are made of carbon fiber prepreg and have the same width as the rib grooves of the split mold, performing annular and longitudinal staggered circulation layering on the split mold, and performing one-time glue suction and pre-compaction treatment on the layering when the thickness of the layering is increased by a preset value; and 4, step 4: repeating the step 3 until the thickness of the total paving layer reaches the expected thickness; paving a skin on the surface of the grid rib and curing by adopting an autoclave process; and 5: and (4) sequentially removing the core mold and the split mold from the cured mold obtained in the step (4) to obtain the special-shaped composite material reinforced grid rib.
In the method for forming the special-shaped composite material reinforced grid rib, it is further preferable that in step 1, the core mold is in a triangular frustum shape, and a first boss and a second boss are arranged on the core mold along the height direction, the first boss is positioned above the first boss, a groove is arranged on the upper surface of the first boss, and the upper surface of the second boss is a plane; the split mold is longitudinally split, a positioning pin and a contact platform are arranged on the back face of each split mold, the positioning pin is matched with the groove, and the contact platform is matched with the second boss.
Preferably, in the step 1, the section of the rib groove is a trapezoid with a narrow inside and a wide outside, and the inclination angle between the two waist lengths and the bottom edge of the trapezoid is 3-6 °.
Preferably, four corners of the staggered joint of the circumferential rib groove and the longitudinal rib groove of the split mold are provided with chamfers, and the radius of each chamfer is calculated by adopting the following formula:
wherein x is the width of the circumferential rib groove; y is the width of the longitudinal rib groove; r is a fillet radius.
In the above molding method of the profiled composite material reinforced grid rib, it is further preferable that, in step 3, when the layers are laid in a staggered and cyclic manner, the breakage rate of the longitudinal rib laying is 10-20% lower than that of the circumferential rib laying at the crossing position of the rib grooves; the continuous fiber layering rate of the inner surface and the outer surface of the integral layering is 8-12%.
Preferably, in step 3, when the thickness of the layer is increased by 2-4mm, the layer is subjected to glue-absorbing pre-compaction treatment for one time, and the glue-absorbing pre-compaction treatment specifically includes: filling the rib grooves of the split dies with the silicon rubber strips with trapezoidal sections, and applying precompaction force to the silicon rubber strips; the gradient and the width of the trapezoid cross section in the silicon rubber strip are the same as those of the rib groove, and after the rib groove is filled, the silicon rubber strip is 2-4mm higher than the upper surface of the split mold.
In the method for forming the reinforced grid rib of the special-shaped composite material, it is further preferable that the pre-compaction acting force is calculated by the following formula:
wherein P is pre-compaction pressure in Pa; delta L is the deformation of the rubber strip in the thickness direction in the pre-compaction process, and is unit m; l is the thickness of the rubber strip and the unit m; e is the rubber elastic modulus.
The forming method of the special-shaped composite material reinforced grid rib further preferably includes, in the step 4, in the autoclave process, the curing temperature is 150-180 ℃, the pressure is 0.6-1 MPa, and the curing time is 6-12 h.
In the method for molding the profiled composite material reinforced grid rib, it is further preferable that in step 3, in the longitudinal laying, the end of the carbon fiber prepreg extends to the cabin section end frame, and the extending length is not less than 80 mm.
The invention also discloses a special-shaped skin cabin section which comprises the special-shaped composite material reinforced grid rib manufactured by the molding method of the special-shaped composite material reinforced grid rib.
Compared with the prior art, the invention has the following advantages:
the invention discloses a molding method of a special-shaped composite material reinforced grid rib, which comprises the following steps: step 1: taking a forming die of the special-shaped composite material reinforced grid rib, wherein the forming die comprises a core die and a split die; the split mold is fixed on the outer side of the core mold, the outer surface of the split mold is provided with an annular rib groove along the horizontal direction, and a longitudinal rib groove is arranged along the vertical direction; step 2: taking a block-shaped carbon fiber fabric, paving the block-shaped carbon fiber fabric on the outer surface of the split mold in a shape, and turning the upper side and the lower side of the carbon fiber fabric to the outer side of the thinning mold; and step 3: taking one or more layers of ribs which are made of carbon fiber prepreg and have the same width as the rib grooves of the split mold, performing annular and longitudinal staggered circulation layering on the split mold, and performing one-time glue suction and pre-compaction treatment on the layering when the thickness of the layering is increased by a preset value; and 4, step 4: repeating the step 3 until the thickness of the total paving layer reaches the expected thickness; paving a skin on the surface of the grid rib and curing by adopting an autoclave process; and 5: and (4) sequentially removing the core mold and the split mold from the cured mold obtained in the step (4) to obtain the special-shaped composite material reinforced grid rib. By the method, the cabin section can be perfectly replaced by the composite material to the metal material, the characteristics of light weight, high strength and fatigue resistance of the composite material are fully exerted, the operation cost is reduced, and the service cycle of the product is prolonged; in addition, the method also solves the problem that the composite material is only used on products with regular structural shapes, and promotes the development and application of the composite material industry.
The layering mode of the grid ribs adopted by the invention is manual layering, so that the carbon fiber prepreg can be tightly attached to the positive curvature part in the split mold, can be attached to the negative curvature part in the split mold, and can ensure the molding quality of the product.
According to the invention, the rib grooves of the silicon rubber strip split mold with the trapezoidal section and the same gradient and width as the rib grooves and the height 2-4mm higher than the rib grooves are filled, and the prepressing acting force is applied to the silicon rubber strips to enable the outer surface of the silicon rubber strips to be flush with the outer surface of the split mold, namely, the expansion of the silicon rubber strips is utilized to prepress the laid layer, so that the accurate control of the thickness of the laid layer is realized, and the problems that the size is too large, namely the size is too much higher than the surface of the mold, the silicon rubber is easily pressed to be biased in vacuum pressurization and the pressurizing pressure cannot be accurately transmitted can be avoided; when the size is too small, the silicon rubber is trapped in the grid rib grooves, and the whole pressure cannot be applied to the silicon rubber in vacuum pressurization. The invention also ensures the stress direction of the grid rib and the strength on the action surface by controlling the ply breaking rate and the continuous ply rate.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
FIG. 1 is a three-dimensional structure of a grid rib cabin section in the invention;
FIG. 2 is a front view of a core mold in the forming mold of the present invention;
FIG. 3 is a schematic view showing the assembly of the core mold and the split mold in the forming mold according to the present invention;
FIG. 4 is an enlarged view of the structure of portion A in FIG. 3;
FIG. 5 is a schematic diagram of prepressing of the silicone rubber strip in the separating film of the present invention.
Description of reference numerals:
1-grid rib, 2-special-shaped skin cabin section, 3-core mold, 4-first boss, 5-second boss, 6-groove, 7-positioning hole, 8-split mold, 9-positioning pin, 10-upper pressure equalizing plate, 11-lower pressure equalizing plate, 12-silicon rubber strip and 13-rib groove.
Detailed Description
As shown in fig. 1 to 5, the method for forming the reinforced grid rib of the special-shaped composite material disclosed in this embodiment includes the following steps:
step 1: taking a forming die of the special-shaped composite material reinforced grid rib 1, wherein the forming die comprises a core die 3 and a split die 8; the split mold 8 is fixed on the outer side of the core mold 3, an annular rib groove 13 is formed in the outer surface of the split mold along the horizontal direction, and a longitudinal rib groove 13 is formed in the outer surface of the split mold along the vertical direction;
step 2: taking a block-shaped carbon fiber fabric, and paving the block-shaped carbon fiber fabric on the outer surface of the split mold in the step 1 along with the shape, wherein the upper side and the lower side of the carbon fiber fabric both extend to the upper end frame and the lower end frame of the thinning mold;
and step 3: taking one or more layers of ribs made of carbon fiber prepreg and having the same width as the rib grooves 13 of the split mold 8 to perform annular and longitudinal staggered circulation layering on the split mold 8, and performing one-time glue suction pre-compaction treatment on the layering when the thickness of the layering is increased by a preset value;
and 4, step 4: repeating the step 3 until the thickness of the total paving layer reaches the expected thickness; paving a skin on the surface of the grid rib 1 and carrying out curing treatment by adopting an autoclave process;
and 5: and (4) sequentially removing the core mold 3 and the split mold 8 from the cured mold obtained in the step (4) to obtain the special-shaped composite material reinforced grid rib 1.
In the method, the forming die is used for forming a shell structure with a cavity, specifically, in the forming stage, the core die 3 provides support for the split die 8 to form the structure on the outer surface of the split die 8, and in the splitting stage, the core die 3 is detached from the inner part of the split die 8 to enable the split die 8 to move inwards and further separate from the formed structure.
Specifically, in the forming die in step 1, the core die 3 is mainly made of a metal steel material, and the split dies 8 are mainly made of an aluminum alloy material, so that the characteristics of high rigidity and low thermal expansion of the metal steel material are utilized to control the connection precision of the outer split dies 8 and the dimensional precision in the product preparation process.
Further, as shown in fig. 2 to 5, in order to support and separate the core mold 3 and the split mold 8, the core mold 3 is in a triangular frustum shape, and a first boss 4 and a second boss 5 are provided on the core mold 3 along the height direction, the first boss 4 is located above, a groove 6 is provided on the upper surface, and the upper surface of the second boss 5 is a plane; the split mold 8 is split longitudinally, a positioning pin 9 and a contact platform are arranged on the back face of each split mold, the positioning pin 9 is matched with the groove 6, and the contact platform is matched with the second boss 5. In the molding stage, the core mold 3 is fixedly mounted, the split molds 8 are sequentially arranged on the outer side of the core mold 3 in a surrounding manner and are completely spliced, specifically, the split molds 8 are placed on the core mold 3 through the matching of the contact table and the second boss 5, so that the axial support is realized, and meanwhile, the split molds are fixed on the core mold 3 through the matching of the positioning pins 9 and the grooves 6, so that the axial and circumferential positioning is realized. Preferably, in order to improve the connection strength, a plurality of positioning holes 7 are uniformly distributed on the peripheries of the upper end and the lower end of the core mold 3, and are suitable for being connected with the split molds 8 in a positioning manner.
Further, the cross section of the rib groove 13 in the split mold 8 is in a trapezoid shape with a narrow inside and a wide outside, and the inclination angle between the length of the two sides of the trapezoid and the bottom side is 3-6 °.
Furthermore, four corners of the staggered joint of the circumferential rib groove 13 and the longitudinal rib groove 13 of the split mold 8 are provided with chamfers, and the radiuses of the chamfers are calculated by adopting the following formula:
wherein x is the width of the circumferential rib groove 13; y is the width of the longitudinal rib groove 13; r is a fillet radius.
In addition, the forming die further comprises an upper pressure equalizing plate 10 and a lower pressure equalizing plate 11, wherein the upper end surface and the lower end surface of the upper pressure equalizing plate 10 and the lower pressure equalizing plate 11 after the split dies are closed are the same in shape and are used for contact pressure equalization of the upper end surface and the lower end surface. In addition, the upper pressure equalizing plate 10 and the lower pressure equalizing plate 11 are provided with a plurality of sets, the thicknesses of the pressure equalizing parts of the upper pressure equalizing plate 10 and the lower pressure equalizing plate 11 are different, the upper pressure equalizing plate 10 and the lower pressure equalizing plate 11 are synchronously increased along with the increase of the thickness of the laid layer in the process of glue absorption and pre-compaction, and specifically, the width of the pressure equalizing plate is increased by 3-5mm when the thickness of the laid layer is increased by 3-5 mm.
The forming die is arranged through the structure, so that the thickness of the grid rib 1 can be controlled through repeated glue suction and pre-compaction in the preparation process, the product size is ensured, and the design and processing of the vulva die are reduced; the core mold 3 is designed into a triangular frustum structure, so that demolding work after curing and molding is facilitated, and the upper layer and the lower layer of bosses are designed, so that the positioning and mounting work of the split mold 8 is facilitated; the upper and lower pressure equalizing plates 11 are adjusted according to the thickness of the laying layer, so that the overall dimension control of the position of the end frame of the product is facilitated.
Specifically, in step 2, the carbon fiber fabric can be in a strip shape, the whole outer surface of the split mold is covered by adopting a circumferential covering and longitudinal covering mode through the filling tool, and in the covering process, the circumferential carbon fiber fabric is in lap joint with the longitudinal carbon fiber fabric so as to improve the connection strength of the carbon fiber fabric.
Further, in the step 3, when the layers are laid in a staggered and circulating mode, the breaking rate of the longitudinal rib laying layer is 10-20% lower than that of the circumferential rib laying layer at the crossing position of the rib grooves 13; the continuous fiber layering rate of the inner surface and the outer surface of the integral layering is 8-12%.
The layering is divided into longitudinal layering and circumferential layering, and the crossed layering is carried out, in order to prevent fiber stacking at the crossed position, a mode that the ring and the longitudinal are broken at the crossed position according to a certain proportion is adopted, the total layering layer number is set as a, the circumferential layering layer number is set as a/2, the circumferential layering layer number broken at the crossed position is set as b, and the annular layering breaking rate is set as
(ii) a And secondly, in order to ensure the axial load bearing performance of the structure, fiber continuous layering is adopted on the inner surface and the outer surface of the product, the continuous layering rate of the ring and the longitudinal at the position of a cross point is 8-12%, namely the total number of the continuous layering layers on the inner surface and the longitudinal surface of the ring is (8-12%) a.
In the molding stage, firstly, surface cleaning and release agent coating are carried out on the split mold 8, and the pre-treatment work of laying is finished; then, carbon fiber fabric is adopted to carry out one-layer bottoming laying on the groove of the grid rib 1 and the surface of the mold so as to improve the integral bearing performance of the grid rib 1. Laying layers at the positions of grid ribs 1, and performing annular and longitudinal staggered circulation laying on one or more layers of unidirectional carbon fiber prepregs with the same rib groove 13 width; and (3) performing glue absorption and pre-compaction once every 2-4mm of the thickness of the layer to control the internal defects of the product and improve the structural performance. And determining the times of glue suction and pre-compaction according to the total depth of the rib grooves 13, and controlling the glue suction temperature according to the temperature-viscosity curve of the carbon fiber prepreg cloth.
Further, according to the load and stress condition of the structural cabin section in the using process, the layer of the composite material grid rib 1 is optimally designed; because the whole cabin section mainly bears axial compression load, the compression strength of the composite material structure is lower than the tension strength, and therefore, the compressed part has better fiber continuity; the outer side of the structural cabin section (the outer side refers to the inner surface and the outer surface of the integral structure) bears larger load than the inner side (the inner side refers to the position of the rib and groove laying middle layer), so that the continuity of the fiber on the outer side of the structural cabin section is preferentially ensured. Secondly, considering the smoothness of the cross position of the grid rib 1, the cross position of the grid rib 1 is subjected to ply design according to a certain ply breakage rate; considering the bearing performance of the structural cabin section, preferentially considering the continuity of the longitudinal grid ribs 1, wherein the breaking rate of the integral longitudinal rib laying is 10-20% lower than that of the circumferential rib laying; the integral laying layer at the position of the grid rib 1 ensures that 8% -12% of the fiber on the inner side surface and the outer side surface is continuously laid.
Further, in order to ensure effective bearing and transmission of load at the position of grid ribs 1 of the structural cabin section, in the process of layering the carbon fiber reinforced composite material ribs, the ribs extend to the positions of upper and lower end frames of the structural cabin section according to a certain proportion, a lapped layering mode is adopted for layering the ribs, the length of lapping with the cabin section end frame is not less than 80mm, and the open hole area of the upper cabin section is avoided; to avoid fiber accumulation, the fibers at the overlap position can be in a bulk form; the lapping rule follows the principle of fiber continuity of circumferential and longitudinal ribs, namely, 1 lapping and laying layer of the grid ribs is carried out once when the continuous fibers are adopted to carry out laying layer of the grid ribs 1.
Further, in the step 3, when the thickness of the paving layer is increased by 2-4mm, the paving layer is subjected to glue absorption and pre-compaction treatment once. The pre-compaction treatment specifically comprises: filling the rib groove 13 of the split mold 8 with a silicon rubber strip 12 with a trapezoidal section, and applying a pre-compaction acting force to the silicon rubber strip 12; the gradient and the width of the trapezoid cross section in the silicon rubber strip 12 are the same as those of the rib groove 13, and after the rib groove is filled, the silicon rubber strip 12 is 2-4mm higher than the upper surface of the split mold 8.
Specifically, the adhesive suction pre-compaction treatment includes adhesive suction treatment and pre-compaction treatment, specifically, the silicone rubber strips 12 are filled in the rib grooves 13, then the adhesive suction material and the sealing bag are integrally wrapped on the outer sides of the silicone rubber strips 12, namely the outer surfaces of the split male molds, and then the sealing bag is vacuumized while applying a pre-compaction acting force to the silicone rubber strips 12 on the outer sides of the sealing bag until the outer surfaces of the silicone rubber strips 12 are flush with the outer surfaces of the split molds 8.
In the process, the grid ribs 1 are pre-compacted by mainly utilizing the thermal expansion amount of the silicon rubber strips 12, and in order to ensure the pre-compaction effect and the glue absorption effect, the thermal expansion rate alpha of the silicon rubber strips 12 is more than or equal to 2.0E-5/DEG C; the glue absorption material is nylon demoulding cloth with the saturated glue absorption amount less than or equal to 15 percent.
Furthermore, the strength of the structural bearing performance of the composite material product is determined by the fiber volume ratio in the structure, and the fiber volume ratio of the composite material is preferably considered under the condition that the product is ensured not to have poor glue. The pre-compaction pressure during the glue sucking and pre-compaction processes influences the flow rate of the resin, and the discharge rate of the resin is ensured within the specified glue sucking temperature and time. And ensuring that the gel content of the product after the gel absorbing and binding is 28-32%, wherein the pre-compaction acting force is calculated by the following formula:
wherein P is pre-compaction pressure in Pa; delta L is the deformation of the rubber strip in the thickness direction in the pre-compaction process, and is unit m; l is the thickness of the rubber strip and the unit m; e is the rubber elastic modulus.
Further, in the step 4, in the autoclave process, the curing temperature is 150-180 ℃, the pressure is 0.6-1 MPa, and the curing time is 6-12 h.
Further, the embodiment also discloses a special-shaped skin cabin section 2, which comprises the special-shaped composite material reinforced grid rib 1 manufactured by the molding method of the special-shaped composite material reinforced grid rib 1.
The layering process method can perfectly realize the structural production and preparation of the large-scale and special-shaped structure composite material grid rib 1, and the composite material grid rib can be applied to structural products such as a transition section, a cabin section and the like of a spacecraft, so that the advantages of light weight, high strength, fatigue resistance, corrosion resistance and the like of the composite material can be fully exerted, the problem of high processing cost caused by processing a grid rib structure by using a traditional metal material with high sensitivity to tiny defects is solved, and the whole operation cost is reduced.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (10)
1. A molding method of a special-shaped composite material reinforced grid rib is characterized by comprising the following steps:
step 1: taking a forming die of the special-shaped composite material reinforced grid rib, wherein the forming die comprises a core die and a split die; the split mold is fixed on the outer side of the core mold, the outer surface of the split mold is provided with circumferential rib grooves along the horizontal direction, and longitudinal rib grooves are arranged along the vertical direction;
step 2: taking a massive carbon fiber fabric, and paving the massive carbon fiber fabric on the outer surface of the split mold in a shape, wherein the upper end and the lower end of the carbon fiber fabric extend to the upper end frame and the lower end frame of the thinning mold;
and step 3: taking one or more layers of ribs which are made of carbon fiber prepreg and have the same width as the rib grooves of the split mold, performing annular and longitudinal staggered circulation layering on the split mold, and performing one-time glue suction and pre-compaction treatment on the layering when the thickness of the layering is increased by a preset value;
and 4, step 4: repeating the step 3 until the thickness of the total paving layer reaches the expected thickness; paving a skin on the surface of the grid rib and curing by adopting an autoclave process;
and 5: and (4) sequentially removing the core mold and the split mold from the cured mold obtained in the step (4) to obtain the special-shaped composite material reinforced grid rib.
2. The method for forming a profiled composite reinforcing grid rib according to claim 1, wherein in step 1, the core mold is in a triangular frustum shape, and a first boss and a second boss are arranged on the core mold along the height direction, the first boss is positioned above the second boss, a groove is arranged on the upper surface of the first boss, and the upper surface of the second boss is a plane; the split mold is longitudinally split, a positioning pin and a contact platform are arranged on the back face of each split mold, the positioning pin is matched with the groove, and the contact platform is matched with the second boss.
3. The method for forming the special-shaped composite material reinforced grid rib as claimed in claim 2, wherein in the step 1, the section of the rib groove is in a trapezoid shape with a narrow inner part and a wide outer part, and the inclination angle between the waist length and the bottom edge of the trapezoid is 3-6 degrees.
4. The molding method of the special-shaped composite material reinforced grid rib as claimed in claim 3, wherein chamfers are arranged at four corners of the staggered nodes of the circumferential rib grooves and the longitudinal rib grooves of the split molds, and the radiuses of the chamfers are calculated by adopting the following formula:
wherein x is the width of the circumferential rib groove; y is the width of the longitudinal rib groove; r is a fillet radius.
5. The molding method of the special-shaped composite material reinforced grid rib as claimed in any one of claims 1 to 4, wherein in the step 3, when the circular layering is staggered, the breakage rate of the longitudinal rib layering is 10-20% lower than that of the circumferential rib layering at the positions of the rib groove intersections; the continuous fiber layering rate of the inner surface and the outer surface of the integral layering is 8-12%.
6. The forming method of the special-shaped composite material reinforced grid rib as claimed in claim 5, wherein in the step 3, when the thickness of the layer is increased by 2-4mm, the layer is subjected to one-time glue absorption pre-compaction treatment; the pre-compaction treatment specifically comprises: filling the rib grooves of the split dies with the silicon rubber strips with trapezoidal sections, and applying precompaction force to the silicon rubber strips; the gradient and the width of the trapezoid cross section in the silicon rubber strip are the same as those of the rib groove, and after the rib groove is filled, the silicon rubber strip is 2-4mm higher than the upper surface of the split mold.
7. The method of claim 6, wherein the pre-compaction force is calculated by the following formula:
wherein P is pre-compaction pressure in Pa; delta L is the deformation of the rubber strip in the thickness direction in the pre-compaction process, and is unit m; l is the thickness of the rubber strip and the unit m; e is the rubber elastic modulus.
8. The method for forming the special-shaped composite material reinforced grid rib as claimed in claim 7, wherein in the step 4, in the autoclave process, the curing temperature is 150-180 ℃, the pressure is 0.6-1 MPa, and the curing time is 6-12 h.
9. The method for forming the special-shaped composite material reinforced grid rib as claimed in claim 8, wherein in the step 3, in the longitudinal laying, the end parts of the rib strips extend to the upper end frame and the lower end frame of the split mold, and the extending length is not less than 80 mm.
10. A profiled skin cabin section, comprising a profiled composite reinforced grid rib produced by the method of forming a profiled composite reinforced grid rib according to any one of claims 1 to 9.
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