CN117944328A - Z-Pin reinforced composite sandwich structure and preparation method thereof - Google Patents

Abstract

The invention provides a Z-Pin reinforced composite material sandwich structure and a preparation method thereof, wherein the Z-Pin reinforced composite material sandwich structure comprises an upper composite material skin, a core material and a lower composite material skin, and a composite material needle is implanted in the Z direction of a preformed body of the sandwich structure for Z-direction reinforcement; the composite material needle is made of the same material as the composite material skin, and the composite material needle is placed into the cavity to be implanted by a high-pressure air gun; the composite material needle is a carbon fiber or high-strength glass fiber reinforced plastic needle. The invention has the beneficial effects that: the composite material reinforcing rib vertical to the fiber cloth is implanted, and the scheme solves the problems that different reinforcing angles, large directional difference, unobvious effect, weakened performance in other directions and the like possibly caused by other reinforcing schemes, and particularly solves the problems that large products, sandwich pieces and special-shaped pieces are difficult to stitch and realize engineering, and defects are easy to generate in the X and Y directions of the in-plane fabric.

Description

Z-Pin reinforced composite sandwich structure and preparation method thereof

Technical Field

The invention belongs to a composite structural member, and particularly relates to the technical field of preparation processes of foam sandwich preformed bodies.

Background

The composite material is composed of fiber reinforced composite material, foam and fiber reinforced composite material, wherein the fiber reinforced composite material can be prepared by vacuum filling resin into fiber cloth for curing, or can be prepared by hot-press molding and curing of prepreg.

The Z direction between layers of the composite material is a weak point, and the existing reinforcing scheme mainly comprises a continuous fiber stitching three-dimensional weaving scheme; the Z-direction enhancement scheme is a main research enhancement scheme in the domestic industry at present, and related researches are carried out by domestic surgical research institutes and universities; the Z-direction strength of the fiber cloth or the sandwich material body is enhanced by adopting continuous fibers to stitch and weave the fiber cloth or the sandwich material body into a whole.

The scheme is the most easily conceivable Z-direction enhancement scheme in the conventional thinking, but the research progress is limited greatly, the effect is not ideal, and the main reasons are that:

1) The suturing can adopt two modes of manual suturing and equipment suturing, and the problems of difficulty, limitation and derivatization are all larger.

Manual suturing: the efficiency is low, the consistency of parameters such as manual sewing angle, strength, depth and the like is poor, meanwhile, when the product is large to a certain size, the overturning is difficult, particularly the manual sewing of a sandwich product is almost impossible, and the enhancement scheme is only suitable for local area implementation of a template, a small product or a product edge, and the like.

Mechanical stitching: the mechanical stitching can solve the problems of low manual stitching efficiency and instability, but for special-shaped products, the stitching equipment matched with the special-shaped products is required to be customized according to the specifications such as size, line type and the like, namely, each product in different shapes can be stitched better only by customizing a corresponding stitching equipment, and the application of the stitching equipment is greatly limited due to the fact that the stitching equipment is required to be debugged, corrected and the like.

2) Can cause defects

Because the continuous fiber is used for stitching, the fiber is implanted and enhanced in the Z direction, the fiber is inevitably turned in the direction of the cloth layer X, Y during turning and inserting, the state of the fiber fabric in the direction of X, Y is influenced, a certain amount of uneven, warping, rugged defects and the like are formed on the fiber in the direction, the fiber is enhanced in the Z direction and weakened in the direction of X, Y, the fiber stitching layout, angle, depth, strength and the like of the fiber affect the final performance of the product to a certain extent, the surface of the product is uneven to a certain extent, namely a series of defects are caused, and the application of the fiber is limited to a great extent.

2. Three-dimensional braiding, namely three-dimensionally braiding the fiber fabric; however, the cost is too high, each model piece needs to be designed independently, the trial braiding correction is poor in universality and few in application.

The fiber cloth is directly woven into the three-dimensional woven cloth in a shape state, and the three-dimensional woven cloth has high strength in X, Y, Z directions because the three-dimensional woven cloth is integrally woven.

However, the application is also limited and has the following main points:

1) Low braiding efficiency and very high braiding cost

The three-dimensional knitting cost is high, although special knitting is realized, a knitting program is required to design, special equipment knitting is also generally low in efficiency, and generally special-shaped complex and strong fabric knitting equipment is difficult to be used universally, even iterative optimization after multiple times of knitting is possible, and the like, so that the cost is very high, and the application of the special-shaped complex and strong fabric knitting equipment is greatly limited.

2) The braiding equipment is difficult to be used universally

The special-shaped fabric knitting equipment is difficult to be used commonly, the knitting equipment is required to be customized, high equipment investment, corresponding personnel, maintenance and the like are required, and popularization and application are greatly hindered.

3) Three-dimensional fabric property variation

The Z-direction performance of the three-dimensional fabric is greatly enhanced, but the fiber is greatly turned, and the X-direction performance and the Y-direction performance of the three-dimensional fabric are greatly affected.

4) Limited application process

On one hand, the single layer of the woven body is thicker, so that the woven body is not suitable for being made into prepreg, and the autoclave and the OOA process are not suitable; on the other hand, the special-shaped part is woven into a thickened fiber layer, and is not suitable for splicing, so that the special-shaped part is required to be woven into a whole, the special-shaped part with a complex shape is particularly difficult to weave, and the application is extremely limited.

The composite structure has the main problems that:

1) A layered structure having relatively low in-plane strength relative to interlayer forces;

2) The sandwich structure is designed to reduce weight as much as possible, the foam density is low, the strength is much lower than that of the reinforced composite material, and the overall compression strength is lower.

Chinese patent grant bulletin number CN113246585B, entitled punch pin, threading pin, system and method for making foam sandwich preforms; the foam sandwich preform comprises a first covering layer, a foam core material, a second covering layer and yarns, wherein the foam core material is positioned between the first covering layer and the second covering layer to form a sandwich structure, and the yarns penetrate through the sandwich structure and connect the first covering layer, the foam core material and the second covering layer. It gives to some extent a foam sandwich preform with different fiber column contents.

The punching equipment, the punching needle, the threading needle and other auxiliary systems are specially used for foam sandwich preformed body, and the fiber yarn can be threaded into the sandwich preformed body according to the set specification by adopting a series of punching and threading processes, and the resin is led into the sandwich preformed body for forming and curing, so that the Z-direction fiber reinforcement can be formed in the preformed body for Z-direction reinforcement.

It also has the following problems: 1) The pre-inserted fiber Z-Pin reinforced implantation fiber material adopts a liquid resin introduction process, so that the resin can form reinforcing benefit after being immersed and solidified, thus being only suitable for a liquid resin molding process;

2) The fiber yarn is implanted by a special fixed preset device, and can only be pre-implanted in a standard flat plate, and when the foam plate needs secondary processing or arc-shaped surface application, the application of the foam plate is limited.

Disclosure of Invention

Aiming at the technical problems, the invention provides a Z-direction implanted reinforced prefabricated needle-shaped composite material when foam is paved.

The technical scheme of the invention is as follows:

The Z-Pin reinforced composite material sandwich structure has the structural form of an upper composite material skin, a core material and a lower composite material skin, and a composite material needle is implanted in the Z direction of a preformed body of the sandwich structure for Z-direction reinforcement.

Further, the composite needle is made of the same material as the composite skin, and the composite needle is implanted by a high-pressure air gun.

Further, the composite needle is: carbon fiber or high-strength glass fiber reinforced plastic needle.

Further, the diameter of the composite material needle is 0.6-1.5 mm, an array or criss-cross arrangement mode is adopted in the surface of the sandwich preform, and the vertical distance between the composite material needle in the X direction and the Y direction in the surface is between 10-20 mm.

Furthermore, the composite material needles can be arranged in a variable density manner, namely, the needle pitch can be properly reduced in a region with high stress, and the needle pitch can be properly increased in a region with low stress.

A preparation method of a Z-Pin reinforced composite material sandwich structure comprises the following steps:

S1) prefabricating a composite needle, and injecting the length according to the requirement, and cutting the prefabricated composite needle into a prefabricated reinforcing needle with a designed specification by using a guillotine;

S2) paving the composite material sandwich structure according to the sequence of the skin fiber cloth, the core material and the upper surface layer 1-2 layers of composite material fiber cloth;

S3) placing the composite material needle into a high-pressure air gun, and implanting the composite material needle into the sandwich preform body along the Z direction according to a Z-Pin reinforcement scheme;

s4) paving upper surface layer fiber cloth (residual fibers);

S5) paving corresponding demolding cloth, diversion medium, diversion pipeline, vacuum bag film and sealing adhesive tape auxiliary materials according to a vacuum auxiliary molding process, after the sealing leakage detection is qualified, introducing corresponding resin, and curing to obtain the Z-pin reinforced composite sandwich structure.

Further, the diameter of the composite needle is 0.6-1.5mm.

Furthermore, the design implantation scheme is that the composite material needle arrangement cloth is vertically and horizontally arranged at a vertical distance of 10-20 mm, and is vertically and horizontally arranged or staggered.

Further, the structural thickness of the above-mentioned, laid layer is 2mm carbon fiber +20mm foam +2mm carbon fiber.

The invention has the beneficial effects that: the composite material reinforcing rib vertical to the fiber cloth is implanted, and the scheme solves the problems that different reinforcing angles, large directional difference, unobvious effect, weakened performance in other directions and the like possibly caused by other reinforcing schemes, and particularly solves the problems that large products, sandwich pieces and special-shaped pieces are difficult to stitch and realize engineering, and defects are easy to generate in the X and Y directions of the in-plane fabric.

Benefits are: 1) The enhancement scheme is not influenced by the size, the abnormal shape and the like of the product, and can be well implemented;

2) The implementation is simple;

3) After implementation, the strength is enhanced only in the Z direction, and the influence on the X, Y-direction in-plane strength is small;

4) The reinforcing benefit is remarkable, and the Z-direction strength and the stripping resistance are remarkably enhanced under the condition of small influence on the weight and the X and Y directions.

Drawings

FIG. 1 is a schematic structural view of a foam sandwich preform of the invention;

Fig. 2: a Z-Pin reinforced carbon needle arrangement (crisscross arrangement) schematic diagram;

Fig. 3: Z-Pin reinforced carbon needle arrangement (staggered arrangement) schematic diagram;

fig. 4: testing the drawing shear strength;

fig. 5: reinforced sample sets (still connected after failure);

Fig. 6: unreinforced sample set (separation after pull failure);

Fig. 7: testing compression strength;

Fig. 8: unreinforced compressed samples (with significant pressure loss);

Fig. 9: after reinforcement, the sample is compressed (no obvious damage mark is observed by naked eyes);

Wherein 1-a composite skin; 2-foaming; 3-composite needle.

Description of the embodiments

The technical scheme of the invention is further described below with reference to the accompanying drawings:

as in fig. 1, preform Z-Pin enhancement mechanism: in the Z direction of the composite material, composite needle-shaped reinforcing ribs perpendicular to the composite material skin are implanted,

The scheme solves the problems that different reinforcement angles and direction differences possibly caused by other reinforcement schemes are large, the effect is not obvious, the performance in other directions is weakened, and the like, particularly solves the problem that large products, sandwich pieces and special-shaped pieces are difficult to stitch and realize engineering, and solves the problems that defects are easy to generate in the X and Y directions of the fabric in the plane, and the like.

Embodiments are described below:

1) Prefabricating carbon fiber rods/needles (hereinafter referred to as needles) with the diameter of 0.6-1.5mm, injecting the carbon fiber rods/needles into the steel tube according to the required length, and cutting the steel tube into prefabricated reinforced needles with the designed specification by using a guillotine;

2) Fiber cloth, foam/other functional material layers are paved with +1-2 layers of fiber cloth;

3) Placing the prepared carbon needle into a special high-pressure air gun, selecting an air gun with corresponding specification according to the diameter of the carbon needle, and injecting the carbon needle into the laying layer according to a designed implantation scheme;

4) Laying a residual cloth layer of the surface fiber cloth;

5) And paving auxiliary materials such as a corresponding vacuum bag film, a sealing adhesive tape and the like according to a vacuum auxiliary forming process, introducing corresponding resin after sealing leakage detection is qualified, and curing to obtain a Z-pin reinforced product.

The hand-held high-pressure air gun can be a common carpenter type nailing high-pressure air gun, one needle can be injected one by one, and continuous injection of the air gun after independent design optimization can be adopted.

The hand-held high-pressure air gun is a common carpenter type nailing high-pressure air gun.

By selecting different composite material needles with the diameters of 0.6, 1.0 and 1.5mm, and arranging the composite material needles in different modes, a sample piece is prepared by a layering structure of 2mm carbon fibers, 20 mmH280 foam and 2mm carbon fibers, and the test shows that the following table 1 results are obtained:

note that: 1) 10 x 10 crisscross arrangement: when the carbon needles are preset, the longitudinal and transverse direction intervals are 10mm, and the carbon needles are distributed in a grid lattice mode, and a 100X 100mm flat plate is taken as an example, and the carbon needles are shown as a schematic diagram in fig. 2;

2) 10 x 10 staggered arrangement: the vertical and horizontal spacing of each carbon needle is 10mm, and every two adjacent rows of carbon needles are staggered transversely, and a 100X 100mm flat plate is taken as an example, and is shown in fig. 3.

1) Description of the drawing shear Strength

As shown in fig. 5 and 6: special tooling: the steel joint tool with the bonding surface diameter of 40mm is clamped by a clamping head of a universal testing machine, the bonding surface and a clamping core sample are firmly bonded by high-strength epoxy glue, the bonding force is larger than the strength of the sample, and the interface bonding strength is tested by drawing.

3) Compression strength benefit;

Preparing a carbon fiber sandwich foam composite material: as can be seen from the results of FIG. 7, FIG. 8 and Table 2, the carbon fiber composite sandwich foam product has a compressive strength of about 193% and a weight of only 2.2% after the Z-Pin reinforcement of the preform, and the compressive strength of the carbon fiber composite sandwich foam product is increased by about 2.3% by taking the 2# piece as an example.

Table 2 gain ratio table:

from the above data, it can be seen that:

1) After the carbon needle prefabricated member is adopted for reinforcement, under the condition that the weight of the sandwich composite material is slightly increased by 0.2-5.3%, the overall compression strength and the drawing shear strength (except for a 5# piece) are basically and obviously increased;

2) After the carbon needle prefabricated member is reinforced and damaged by the test, the carbon needle can still play a certain role in connection or support to prevent foam from damaging or splitting;

3) When the carbon needle prefabricated members are distributed in a staggered mode, compared with the longitudinal and transverse distribution, the compression strength is slightly better, the drawing shearing strength is obviously better, and especially as can be seen from the 5# piece, when the longitudinal and transverse distribution is adopted, and the distribution interval is larger, the drawing shearing strength is reduced;

4) When the distribution spacing of the carbon needle prefabricated members is 10, 15 and 20mm, the smaller the obvious spacing is, the better the reinforcing effect is, and the spacing of 10 and 15mm is obviously better than the spacing of 20mm, and because the spacing is reduced, the carbon needle injection workload is obviously increased in a square proportion, and the distribution pre-planting reinforcement is preferably carried out at the spacing of 10-20 mm;

5) The diameter of the carbon needle prefabricated member is selected to be 0.6-1.5mm, so that a relatively obvious enhancement effect can be achieved; the carbon needle with the diameter below 0.6mm has lower strength and larger difficulty in the prefabrication process, is easy to break in the implantation process, and is not recommended to be used, for example, the carbon needle with the diameter of 2mm has overlarge cross section, the implantation process difficulty is obviously increased, and the diameter of the carbon needle is preferably 0.6-1.5mm.

4) Conclusion(s)

From the comprehensive comparison, the Z-Pin reinforcement scheme of the preform has relatively simple reinforcement process, is not influenced by the restriction of the structural shape of the product, and can obtain the following benefits or changes:

a) The delamination resistance, bonding and compression strength of the composite material can be obviously improved under a small amount of weight increment;

Taking a sample No.2 as an example, under the condition of increasing the weight by 2.2%, the compression strength is increased by 193%, and the drawing shear strength is increased by 33.5%;

If only the local area with larger stress is enhanced in a targeted manner, for example, 10 percent of area enhancement is adopted, the total weight increment is almost negligible (weight increment is 0.22 percent);

The method is only limited to the local point reinforcement of the Z-direction carbon needle, and has influence on the strength of the composite material in X, Y directions, and is much smaller than continuous stitching and three-dimensional weaving;

b) The local layering defect termination capability is obviously improved, and the service time of the device under the condition of sudden damage is effectively prolonged.

The skin in the technical scheme of the invention: refers to a reinforced fiber composite material such as glass fiber, carbon fiber and the like;

The skin can be prepared by hot-press molding and curing of prepreg materials, or can be prepared by vacuum filling resin and curing molding after pre-laying.

Core material: low density, lightweight, high strength foam.

The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to the above-described embodiments

Specific details of the embodiments are described, and within the scope of the technical idea of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

In addition, the specific features described in the above embodiments are not shown in the drawings

In the case of shields, the combination may be made in any suitable way. The various possible combinations of the invention are not described in detail in order to avoid unnecessary repetition.

Moreover, any combination of the various embodiments of the invention can be made without departing from the spirit of the invention, which should also be considered as disclosed herein.

Claims (9)

1. The Z-Pin reinforced composite material sandwich structure is characterized by comprising an upper composite material skin, a core material and a lower composite material skin, wherein a composite material needle is implanted in the Z direction of a preformed body of the sandwich structure for Z-direction reinforcement.

2. The composite sandwich structure of claim 1 wherein the composite needle is the same material as the composite skin and the composite needle placement is accomplished by a high pressure air gun.

3. The composite sandwich structure of claim 1 or 2 wherein the composite needle is: and the composite needle is made of the same material as the surface skin.

4. A composite sandwich structure according to claim 3, wherein the diameter of the composite needle is 0.6-1.5 mm, an array or criss-cross arrangement mode is adopted in the surface of the sandwich preform, and the vertical distance between the composite needle in the X direction and the Y direction in the surface is between 10-20 mm.

5. The composite sandwich structure of claim 4 wherein said composite pins are arranged in a variable density arrangement such that in areas of greater stress the pins are reduced and in areas of lesser stress the pins are increased.

6. The preparation method of the Z-Pin reinforced composite material sandwich structure is characterized by comprising the following steps of:

S1) prefabricating a composite needle, and injecting the length according to the requirement, and cutting the prefabricated composite needle into a prefabricated reinforcing needle with a designed specification by using a guillotine;

S2) paving the composite material sandwich structure according to the sequence of the skin fiber cloth, the core material and the upper surface layer 1-2 layers of composite material fiber cloth;

S3) placing the composite material needle into a high-pressure air gun, and implanting the composite material needle into the sandwich preform body along the Z direction according to a Z-Pin reinforcement scheme;

S4) paving residual fiber cloth on the upper surface layer;

S5) paving corresponding stripping cloth, diversion medium, diversion pipeline, vacuum bag film and sealing adhesive tape auxiliary materials according to a vacuum auxiliary forming process, after the sealing leakage detection is qualified, introducing corresponding resin and/or hot-press forming, and curing to obtain the Z-pin reinforced composite sandwich structure.

7. The method of claim 6, wherein the composite needle has a diameter of 0.6 mm to 1.5mm.

8. The method of claim 6, wherein the design implant is a composite card clothing with a vertical distance of 10-20 mm in the cross-machine direction, a cross-machine direction, or a staggered arrangement.

9. The method of claim 6, wherein the structural thickness of the lay-up layer is 2mm carbon fiber +20mm foam +2mm carbon fiber.