CN115447172A

CN115447172A - Asynchronous retraction curing forming die, component and forming method for weaving NOL (non-oriented yarn) ring

Info

Publication number: CN115447172A
Application number: CN202211149089.9A
Authority: CN
Inventors: 孙正; 单忠德; 王尧尧; 欧阳林志
Original assignee: Nanjing University of Aeronautics and Astronautics
Current assignee: Nanjing University of Aeronautics and Astronautics
Priority date: 2022-09-21
Filing date: 2022-09-21
Publication date: 2022-12-09

Abstract

The invention provides an asynchronous retraction curing forming die for weaving NOL rings. When the curing molding is carried out, the mold is placed on a hot-pressing molding machine, and the hot-pressing molding machine has the functions of heating and hydraulic compression. The hydraulic device of the hot-press forming machine drives the top cover to move downwards, the inclined conical surface in the top cover corresponds to the inclined conical surface of the outer die, the downward pressing movement of the top cover can be converted into the contraction movement of the outer die, and therefore the annular carbon fiber prepreg sleeved on the core die is compressed and heated and cured. The asynchronous retraction mold is reasonable in design and simple in use method, and solves the problem of curing, molding and weaving the NOL ring by using a hot-press molding machine.

Description

Asynchronous retraction curing forming die, component and forming method for weaving NOL (non-oriented yarn) ring

Technical Field

The invention relates to the technical field of composite material forming, in particular to an asynchronous retraction curing forming die, an asynchronous retraction curing forming assembly and an asynchronous retraction curing forming method for weaving NOL rings.

Background

The continuous fiber reinforced composite material has specific rigidity, specific strength and specific modulus which are far higher than those of steel materials. The fiber reinforced composite material is obtained by curing a carbon fiber preform with resin; the structure of the carbon fiber preform has great influence on the mechanical property of the composite material, the internal fiber of the carbon fiber preform prepared by three-dimensional weaving or three-dimensional weaving has multiple directions, and compared with the carbon fiber preform prepared by adopting a layering or winding technology, the carbon fiber preform has better mechanical property in each direction, and the prepared composite material has better mechanical property.

In order to determine various mechanical properties of the composite material, a standard test sample is required to be prepared. The NOL ring is a standard test specimen used to test the interlaminar shear strength, tensile modulus of elasticity, and the tensile strength of its fibers of the annular test specimen. The NOL ring sample is generally prepared by a filament winding method, the NOL ring prepared by the method only has reinforcing fibers in a single direction, and a ring-shaped carbon fiber preform prepared by a three-dimensional weaving or three-dimensional weaving process has reinforcing fibers in multiple directions, and in order to measure the mechanical properties, resin curing is needed.

For carbon fiber composite materials using high temperature resistant resins, resin curing is mostly performed by a mold pressing process, and a hot press molding machine for molding generally has only an up-down compression function and is mostly used for molding flat members. The annular composite material member is formed by using the hot-press forming machine, a plurality of factors need to be considered in the design of the mold, certain difficulty exists, the curing cost can be increased if one set of curing and forming device is designed independently, and the universality of the curing and forming device is low.

Disclosure of Invention

The invention provides an asynchronous shrinkage curing die for weaving NOL rings, which is used for solving the problem in the prior art that a die pressing process is adopted to prepare an annular sample piece and realizing the preparation of a weaving NOL ring sample at low cost.

In order to realize the purpose, the asynchronous shrinkage curing forming die for weaving the NOL ring adopts the following technical scheme:

an asynchronous retraction curing forming die for weaving NOL rings comprises a chassis, a circular core die arranged in the middle of the chassis, an outer die assembly arranged around the core die and arranged on the chassis, and a top cover covering and accommodating the outer die assembly; the outer die assembly comprises a plurality of first outer dies and a plurality of second outer dies, the first outer dies and the second outer dies are alternately arranged on a circumference around the core die, two sides of each first outer die are provided with transversely protruding buckle sliding blocks, and two sides of each second outer die are provided with clamping grooves matched with the adjacent buckle sliding blocks; the bottoms of each first external mold and each second external mold are respectively provided with a centripetal sliding block, and the upper surface of the chassis is provided with a sliding chute correspondingly matched with the centripetal sliding block; the surface of the joint of the two sides of the first outer die and the second outer die is a first chamfer surface inclined from outside to inside to two sides, and the surface of the joint of the two sides of the second outer die and the first outer die is a second chamfer surface inclined from inside to outside to two sides; the first oblique cutting surface and the second oblique cutting surface are attached to each other and move mutually; the inner surface of the first outer die is a first inner surface extending in a transverse arc shape, and the inner surface of the second outer die is a second inner surface extending in a transverse arc shape; the outer surface of the first outer die is a first outer oblique conical surface which gradually expands from top to bottom, and the outer surface of the second outer die is a second outer oblique conical surface which gradually expands from top to bottom; the bottom of the top cover is a hollow cavity, and the inner surface of the cavity is provided with a first inner oblique conical surface matched with the first outer oblique conical surface and a second inner oblique conical surface matched with the second outer oblique conical surface; the first inner oblique conical surface and the second inner oblique conical surface are both inclined surfaces which gradually contract inwards from top to bottom; the outer die assembly has an expansion state and a contraction state, when the outer die assembly is in the expansion state, the first outer die and the plurality of second outer dies are far away from the core die, the first chamfer surfaces and the second chamfer surfaces are staggered, and the second chamfer surfaces are exposed between the first inner surface and the second inner surface; when the top cover moves downwards, the first inner oblique conical surface presses the first outer oblique conical surface, the second inner oblique conical surface presses the second outer oblique conical surface of the outer die assembly to enable the first outer die and the second outer die to move inwards to a contraction state along the sliding groove, and when the outer die assembly is in the contraction state, all the first inner surfaces and the second inner surfaces form a continuous cylindrical surface together.

Furthermore, the extending direction of the clamping groove is parallel to the first oblique plane and the second oblique plane.

Furthermore, all the first outer dies move synchronously when contracting or expanding, and all the second outer dies also move synchronously when contracting or expanding; the ratio of the displacement of the first outer die and the second outer die when the first outer die and the second outer die move inwards along the sliding groove is in direct proportion; the ratio of the slopes of the first and second inner tapered surfaces is equal to the ratio of the displacements.

Furthermore, the cross section of the buckle sliding block and the cross section of the centripetal sliding block are both trapezoidal, and the cross section of the clamping groove and the cross section of the sliding groove are also trapezoidal.

Furthermore, each sliding groove extends in the centripetal direction with the central axis of the core mold as the center of a circle.

Furthermore, a plurality of first lifting rings are connected to the side surface of the chassis; the side surface of the top cover is connected with a plurality of second hanging rings; the core mold is arranged on the chassis and is fixed through a plurality of threaded holes in the bottom of the core mold and a plurality of threaded through holes in corresponding positions of the chassis.

The invention provides an assembly of an asynchronous retraction curing forming die comprising the braided NOL ring, which adopts the following technical scheme:

still include the thermoforming machine, the thermoforming machine includes: the device comprises a hydraulic device, an upper cross beam, an upper pressure plate, an upper heating block, a lower heating block and a base; the asynchronous retraction curing forming die for weaving the NOL ring is placed between an upper heating plate and a lower heating plate, the upper heating plate is fixed below an upper cross beam, the lower heating plate is fixed above a base, and a top cover is positioned below an upper heating block; the hydraulic device drives the upper cross beam to move up and down, so that the upper heating block presses the top cover to move down to drive the first outer die and the second outer die to contract inwards.

The forming method using the assembly provided by the invention adopts the following technical scheme:

when the annular carbon fiber prepreg is cured and molded, the annular carbon fiber prepreg is sleeved on the core mold, is driven by a hydraulic device of a hot-press molding machine, drives the first outer mold and the second outer mold to contract inwards through motion conversion and compresses the annular carbon fiber prepreg, so that the annular carbon fiber prepreg is compressed; and heating the asynchronous shrinkage curing forming die by the upper heating block and the lower heating block, and keeping the temperature for a certain time to finish curing the annular carbon fiber prepreg.

Has the advantages that: the asynchronous internal shrinkage curing forming die for weaving the NOL ring, provided by the invention, can finish curing forming of the annular carbon fiber prepreg on a hot-press forming machine, effectively reduces curing cost and is simple in use method. The mold is unique and precise in structure, the outer molds are formed by splicing a first outer mold and a second outer mold in two shapes, so that a gap is not left at the joint of the two adjacent outer molds during contraction, and resin is prevented from permeating into the gap; the oblique conical surface of the outer die in contact with the top cover effectively converts the hydraulic pressure of the hot-press forming machine into the force for shrinking the die, and is favorable for compressing the annular carbon fiber prepreg to the specified size.

Drawings

FIG. 1 is a schematic structural view of an asynchronous retraction curing forming die for weaving NOL rings provided by the present invention;

FIG. 2 is a schematic diagram of a centripetal slider and a sliding groove of the asynchronous retraction curing molding die for knitting NOL rings, which is provided by the invention, in a partially enlarged structure;

FIG. 3 is a schematic structural view of an asynchronous retraction curing mold for knitting NOL rings according to the present invention when retracted;

FIG. 4 is a schematic structural view of the outer mold of the asynchronous retraction curing molding die for knitting NOL rings provided by the present invention when expanded;

FIG. 5 is a schematic structural view of an asynchronous retraction curing mold for knitting NOL rings according to the present invention when an outer mold is retracted;

FIG. 6 is a schematic structural view of the second trapezoidal sliding block and the second trapezoidal sliding groove of the asynchronous retraction curing molding die for knitting NOL rings provided by the invention;

FIG. 7 is a schematic structural view of the bottom viewing direction of the asynchronous retraction curing mold for knitting NOL rings provided by the present invention when the outer mold is expanded;

FIG. 8 is a structural schematic diagram of the bottom view direction of the asynchronous retraction curing mold for knitting NOL rings provided by the present invention when the outer mold is retracted;

FIG. 9 is a schematic diagram of the top cover structure of an asynchronous retraction curing forming die for weaving NOL rings provided by the present invention;

FIG. 10 is a schematic view of the core mold and base of the asynchronous retraction curing mold for knitting NOL rings in accordance with the present invention;

FIG. 11 is a schematic view of a partially enlarged structure of a threaded connection part where a core mold of the asynchronous retraction curing molding mold for knitting the NOL ring is matched with a base;

fig. 12 is a schematic structural diagram of the asynchronous retraction curing molding die for knitting the NOL ring provided by the invention for curing resin on a hot press molding machine.

Detailed Description

The technical scheme provided by the invention is explained in detail in the following with reference to the attached drawings.

As shown in fig. 1 to 3, the asynchronous retraction curing forming mold for weaving the NOL ring disclosed by the invention comprises a base plate 13, a circular ring-shaped core mold 15 mounted in the middle of the base plate 13, an outer mold assembly arranged around the core mold 15 and mounted on the base plate 13, and a top cover 11 covering and accommodating the outer mold assembly. The chassis 13 side is connected with a plurality of first rings 171, conveniently carries, and is same, and the top cap 11 side is connected with a plurality of second rings 172, conveniently carries.

The outer mold assembly includes four first outer molds 121 and four second outer molds 122 alternately arranged to form a ring shape, and the first outer molds 121 and the second outer molds 122 are alternately arranged around the core mold 15 on a circumference. Two sides of each first external mold 121 are provided with laterally protruding buckle sliders 162, and two sides of each second external mold are provided with clamping grooves 1224 matched with the adjacent buckle sliders 162. The bottoms of each first outer die 121 and each second outer die 122 are respectively provided with a centripetal slider 161, and the upper surface of the chassis 13 is provided with a sliding chute 131 which is correspondingly matched with the centripetal slider 161. The cross section of the snap slider 162 and the cross section of the centripetal slider 161 are both trapezoidal, and the cross section of the clamping groove 1224 and the cross section of the sliding groove 131 are also trapezoidal.

The surfaces of the two sides of the first outer die 121, which are connected with the second outer die 122, are first chamfered surfaces 101 inclined from outside to inside, and the surfaces of the two sides of the second outer die 122, which are connected with the first outer die 121, are second chamfered surfaces 102 inclined from inside to outside; the first chamfer 101 and the second chamfer 102 are attached to each other and move relative to each other. The engaging groove 1224 extends parallel to the first inclined plane 101 and the second inclined plane 102. The inner surface of the first outer die 121 is a first inner surface 1212 extending in a transverse arc shape, and the inner surface of the second outer die 122 is a second inner surface 1222 extending in a transverse arc shape.

As shown in fig. 4 to 8, the outer surface of the first outer mold 121 is a first outer tapered surface 1211 gradually expanding from top to bottom, and the outer surface of the second outer mold 122 is a second outer tapered surface 1221 gradually expanding from top to bottom; the bottom of the top cap 11 is a hollow cavity, and the inner surface of the hollow cavity is provided with a first inner tapered surface 111 matched with the first outer tapered surface 1211 and a second inner tapered surface 112 matched with the second outer tapered surface 1221; the first inner tapered surface 111 and the second inner tapered surface 112 are both inclined surfaces which gradually contract inwards from top to bottom.

The outer die assembly has an expanded state and a contracted state, when the outer die assembly is in the expanded state, the first outer die 121 and the plurality of second outer dies 122 are away from the core die 15, the first chamfer 101 is staggered from the second chamfer 102, and the second chamfer 102 is exposed between the first inner surface 1212 and the second inner surface 1222; when the top cap 11 moves downward, the first inner tapered surface 111 presses down the first outer tapered surface 1211, the second inner tapered surface 112 presses down the outer die assembly second outer tapered surface 1221, so that the first outer die 121 and the second outer die 122 move inward along the slide slot 131 to a contracted state, and when the outer die assemblies are in the contracted state, all of the first inner surface 1212 and the second inner surface 1222 form a continuous cylindrical surface together. The diameter of the cylindrical surface is related to the degree of compression of the annular carbon fiber prepreg 14, and is obtained through calculation and analysis. When the first outer die 121 and the second outer die 122 contract or expand, the contact surfaces of the first outer die 121 and the second outer die 122 are always attached without gaps, so that the resin of the annular carbon fiber prepreg 14 is prevented from permeating between the contact surfaces of the first outer die 121 and the second outer die 122 during compression curing, and the outer dies can be contracted to the minimum and are not clamped in the curing process. The first outer die 121 is provided with a first threaded hole 1213, the second outer die 122 is provided with a second threaded hole 1223, and the handles are conveniently mounted on the first threaded hole 1213 and the second threaded hole 1223 for demoulding after curing and forming. When the first outer dies 121 and the second outer dies 122 move, all the first outer dies 121 move synchronously when contracting or expanding, and all the second outer dies 122 also move synchronously when contracting or expanding; the ratio of the displacements of the first outer mold 121 and the second outer mold 122 when they move inward along the slide grooves 131 is proportional; the ratio of the slopes of the first and second inner

tapered surfaces

1211 and 1221 is equal to the ratio of the displacements. Thanks to the above relationship, when the downward movement of the top cover 11 is converted into the contraction movement of the first and

second molds

121 and 122, the outer tapered surfaces of the first and

second molds

121 and 122 are tightly attached to the inner tapered surface of the top cover, so that the contraction force is uniformly distributed on the two tapered surfaces to the maximum extent, which is beneficial to the transmission of pressure and reduces stress concentration.

As shown in fig. 10 and 11, core 15 is placed on tray 13 and is positioned by an annular projection on the bottom of core 15 and an annular groove on tray 13. The bottom of the core mold 15 is provided with a plurality of threaded holes 151, the bottom plate 13 is provided with a plurality of threaded through holes 132 at corresponding positions, and the core mold 15 and the bottom plate 13 are fixed by threaded connection.

As shown in fig. 12, the asynchronous shrink-in curing mold of the braided NOL ring is placed on a thermoforming machine to form an assembly. This hot briquetting machine includes: a hydraulic device 21, an upper cross beam 22, an upper press plate 23, an upper heating block 241, a lower heating block 242, and a base 25. The upper heating plate 241 is fixed below the upper beam 22, the lower heating plate 242 is fixed above the base 25, and the asynchronous shrink-in curing mold for weaving the NOL ring is placed between the upper heating plate 241 and the lower heating plate 242. The upper beam 22 is driven by the hydraulic device 21 to move up and down, and the upper beam 22 presses the upper heating block 241 and the top cover 11 to move down, so that the movement is converted into the contraction movement of the first outer die 121 and the second outer die 122 through the oblique conical surfaces.

The method for curing and molding the annular carbon fiber prepreg 14 by using the assembly comprises the following steps: first, the ring-shaped carbon fiber preform is fitted over the core mold 15 and impregnated in resin. And taking out after the impregnation is finished, and removing the resin on the surface of the core mold 15 to finish the preparation of the annular carbon fiber prepreg 14. The core mold 15 is fixed on the chassis 13, the annular carbon fiber prepreg 14 is arranged between the core mold 15 and the outer mold, the top cover 11 is placed on the outer mold along the corresponding direction, the whole mold is placed on the lower heating block 242, the upper heating block and the lower heating block are heated to a certain temperature, the upper cross beam 22 is driven to be pressed downwards by the hydraulic device 21, and the outer mold is contracted through motion conversion, so that the annular carbon fiber prepreg 14 is compressed. When the bottom of the top cover 11 contacts the upper surface of the chassis 13, the compression is completed, and the upper and lower heating blocks keep the mould in a specific temperature range for a specific time, so that the curing of the annular carbon fiber prepreg 14 is completed. And (4) demolding after curing is finished, taking out the prepared annular composite material sample piece, and performing subsequent processing treatment to finally finish the preparation of the woven NOL ring sample.

The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above-mentioned embodiments, and all technical solutions belonging to the idea of the present invention belong to the protection scope of the present invention. It should be noted that modifications and adaptations to those skilled in the art without departing from the principles of the present invention may be apparent to those skilled in the relevant art and are intended to be within the scope of the present invention.

Claims

1. An asynchronous retraction curing forming die for weaving NOL rings is characterized by comprising a base plate (13), a circular ring-shaped core die (15) arranged in the middle of the base plate (13), an outer die assembly arranged around the core die (15) and arranged on the base plate (13), and a top cover (11) covering and accommodating the outer die assembly;

the outer die assembly comprises a plurality of first outer dies (121) and a plurality of second outer dies (122), the first outer dies (121) and the second outer dies (122) are alternately arranged around the core die (15) on one circumference, two sides of each first outer die (121) are provided with laterally protruding buckle sliding blocks (162), and two sides of each second outer die are provided with clamping grooves (1224) matched with the adjacent buckle sliding blocks (162); centripetal sliding blocks (161) are arranged at the bottoms of each first outer die (121) and each second outer die (122), and sliding grooves (131) which are correspondingly matched with the centripetal sliding blocks (161) are formed in the upper surface of the base plate (13); the surface of the joint of two sides of the first outer die (121) and the second outer die (122) is a first chamfer surface (101) inclined from outside to inside to two sides, and the surface of the joint of two sides of the second outer die (122) and the first outer die (121) is a second chamfer surface (102) inclined from inside to outside to two sides; the first inclined cutting surface (101) and the second inclined cutting surface (102) are attached to each other and move mutually; the inner surface of the first outer die (121) is a first inner surface (1212) extending in a transverse arc shape, and the inner surface of the second outer die (122) is a second inner surface (1222) extending in a transverse arc shape;

the outer surface of the first outer die (121) is a first outer oblique conical surface (1211) which gradually expands outwards from top to bottom, and the outer surface of the second outer die (122) is a second outer oblique conical surface (1221) which gradually expands outwards from top to bottom; the bottom of the top cover (11) is a hollow cavity, and the inner surface of the cavity is provided with a first inner oblique conical surface (111) matched with the first outer oblique conical surface (1211) and a second inner oblique conical surface (112) matched with the second outer oblique conical surface (1221); the first inner oblique conical surface (111) and the second inner oblique conical surface (112) are both inclined surfaces which gradually contract inwards from top to bottom;

the outer die assembly has an expanded state and a contracted state, when the outer die assembly is in the expanded state, the first outer die (121) and the plurality of second outer dies (122) are far away from the core die (15), the first chamfer (101) and the second chamfer (102) are staggered, and the second chamfer (102) is exposed between the first inner surface (1212) and the second inner surface (1222); when the top cover (11) moves downwards, the first inner oblique conical surface (111) presses the first outer oblique conical surface (1211) downwards, the second inner oblique conical surface (112) presses the outer die assembly and the second outer oblique conical surface (1221) downwards, so that the first outer die (121) and the second outer die (122) move inwards to a contraction state along the sliding chute (131), and when the outer die assembly is in the contraction state, all the first inner surface (1212) and the second inner surface (1222) form a continuous cylindrical surface together.

2. Asynchronous shrink-in setting mould for weaving NOL rings according to claim 1, characterized in that the draw groove (1224) extends in parallel to the first chamfer (101) and the second chamfer (102).

3. Asynchronous retraction curing mould for weaving NOL rings according to claim 1 or 2 characterized in that all first outer moulds (121) are moving synchronously when retracted or expanded and all second outer moulds (122) are moving synchronously when retracted or expanded; the ratio of the displacement of the first outer die (121) and the second outer die (122) when moving inwards along the sliding groove (131) is proportional; a ratio of slopes of the first and second inner slanted conical surfaces (1211, 1221) is equal to the ratio of the displacements.

4. Asynchronous retraction curing mould for braiding NOL rings according to claim 1 or 2 characterized in that the cross section of the snap slider (162) and the cross section of the centripetal slider (161) are both trapezoidal, and the cross section of the clamping groove (1224) is trapezoidal as the cross section of the sliding groove (131).

5. Asynchronous shrink-in and cure-forming mould for weaving NOL rings according to claim 5, characterized in that each runner (131) extends in a centripetal direction with the central axis of the mandrel (15) as the centre.

6. Asynchronous shrink-in mould for the weaving of NOL rings according to claim 1, characterised in that the side of the base plate (13) is connected with a number of first lifting rings (171); the side surface of the top cover (11) is connected with a plurality of second hanging rings (172); the core mould (15) is arranged on the chassis (13) and is fixed through a plurality of threaded holes (151) at the bottom of the core mould (15) and a plurality of threaded through holes (132) at corresponding positions of the chassis (13).

7. An assembly of asynchronous shrink-in setting moulds comprising braided NOL rings according to any of claims 1 to 6, further comprising a thermo-forming machine (2), the thermo-forming machine (2) comprising: the device comprises a hydraulic device (21), an upper cross beam (22), an upper pressure plate (23), an upper heating block (241), a lower heating block (242) and a base (25); the asynchronous inward shrinkage curing forming die for weaving the NOL rings is placed between an upper heating plate (241) and a lower heating plate (242), the upper heating plate (241) is fixed below an upper cross beam (22), the lower heating plate (242) is fixed above a base (25), and a top cover (11) is positioned below an upper heating block (241); the hydraulic device (21) drives the upper cross beam (22) to move up and down, so that the upper heating block (241) presses the top cover (11) to move downwards to drive the first outer die (121) and the second outer die (122) to contract inwards.

8. A molding method using the assembly as set forth in claim 7, characterized in that, when the curing molding of the annular carbon fiber prepreg (14) is performed, the annular carbon fiber prepreg (14) is fitted over the core mold (15), driven by the hydraulic means (21) of the thermo-compression molding machine (2), and the first outer mold (121) and the second outer mold (122) are driven to contract inwardly and compact the annular carbon fiber prepreg (14) through the conversion of motion, thereby compressing the annular carbon fiber prepreg (14); and the asynchronous internal shrinkage curing forming die (1) is heated by the upper heating block (241) and the lower heating block (242), and the temperature is kept for a certain time to finish curing of the annular carbon fiber prepreg (14).